FEBS Letters

Identification of protein interaction regions of VINC/NEAT1/Men epsilon RNA.

Publication Date: 2010 Mar 4 PMID: 20211624
Authors: Sreenivasa Murthy, U. M. - Rangarajan, P. N.
Journal: FEBS Lett

The virus inducible noncoding RNA (VINC) was detected initially in the brain of mice infected with Japanese encephalitis virus (JEV) and rabies virus. VINC is also known as NEAT1 or Men epsilon RNA. It is localized in the nuclear paraspeckles of several murine as well as human cell lines and is essential for paraspeckle formation. We demonstrate that VINC interacts with the paraspeckle protein, P54nrb through three different protein interaction regions (PIRs) one of which (PIR-1) is localized near the 5' end while the other two (PIR-2, PIR-3) are localized near the 3' region of VINC. Our studies suggest that VINC may interact with P54nrb through a novel mechanism which is different from that reported for protein coding RNAs.

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Interaction of testisin with maspin and its impact on invasion and cell death resistance of cervical cancer cells.

Publication Date: 2010 Mar 4 PMID: 20211623
Authors: Yeom, S. Y. - Jang, H. L. - Kim, E. - Son, H. J. - Kim, B. G. - Park, C.
Journal: FEBS Lett

Previous studies have shown that testisin promotes malignant transformation in cancer cells. To define the mechanism of testisin-induced carcinogenesis, we performed yeast-two hybrid analysis and identified maspin, a tumor suppressor protein, as a testisin-interacting molecule. The direct interaction and cytoplasmic co-localization of testisin with maspin was confirmed by immunoprecipitation and confocal analysis, respectively. In cervical cancer cells, maspin modulated cell death and invasion; however, these effects were inhibited by testisin in parallel experiments. Of interest, the doxorubicin resistance was dramatically reduced by testisin knockdown (P = 0.016). Moreover, testisin was found to be over-expressed in cervical cancer samples as compared to matched normal cervical tissues. Thus, we postulate that testisin may promote carcinogenesis by inhibiting tumor suppressor activity of maspin. STRUCTURED SUMMARY: MINT-7712215, MINT-7712176: Testisin (uniprotkb:Q9Y6M0) binds (MI:0407) to Maspin (uniprotkb:P36952) by pull down (MI:0096) MINT-7712188: Testisin (uniprotkb:Q9Y6M0) and Maspin (uniprotkb:P36952) colocalize (MI:0403) by fluorescence microscopy (MI:0416) MINT-7712115: Testisin (uniprotkb:Q9Y6M0) physically interacts (MI:0915) with Maspin (uniprotkb:P36952) by two hybrid (MI:0018) MINT-7712162, MINT-7712128: Maspin (uniprotkb:P36952) physically interacts (MI:0915) with Testisin (uniprotkb:Q9Y6M0) by anti bait coimmunoprecipitation (MI:0006) MINT-7712147: Testisin (uniprotkb:Q9Y6M0) physically interacts (MI:0915) with Maspin (uniprotkb:P36952) by anti tag coimmunoprecipitation (MI:0007).

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Species-dependence of the redox potential of the primary quinone electron acceptor Q(A) in photosystem II verified by spectroelectrochemistry.

Publication Date: 2010 Mar 4 PMID: 20211622
Authors: Shibamoto, T. - Kato, Y. - Nagao, R. - Yamazaki, T. - Tomo, T. - Watanabe, T.
Journal: FEBS Lett

The redox potentials E(m)(Q(A)/Q(A)(-)) of the primary quinone electron acceptor Q(A) in oxygen-evolving photosystem II complexes of three species were determined by spectroelectrochemistry. The E(m)(Q(A)/Q(A)(-)) values were experimentally found to be -162 +/- 3 mV for a higher plant spinach, -171 +/- 3 mV for a green alga Chlamydomonas reinhardtii and -104 +/- 4 mV vs. SHE for a red alga Cyanidioschyzonmerolae. On the basis of possible deviations for the experimental values, as estimated to differ by 9 - 29 mV from each true value, plausible causes for such remarkable species-dependence of E(m)(Q(A)/Q(A)(-)) are discussed, mainly by invoking the effects of extrinsic subunits on the delicate structural environment around Q(A).

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QSOX Contains a Pseudo-Dimer of Functional and Degenerate Sulfhydryl Oxidase Domains.

Publication Date: 2010 Mar 4 PMID: 20211621
Authors: Alon, A. - Heckler, E. - Thorpe, C. - Fass, D.
Journal: FEBS Lett

Quiescin sulfhydryl oxidase (QSOX) catalyzes formation of disulfide bonds between cysteine residues in substrate proteins. Human QSOX1 is a multidomain, monomeric enzyme containing a module related to the single-domain sulfhydryl oxidases of the Erv family. A partial QSOX1 crystal structure reveals a single-chain pseudo-dimer mimicking the quaternary structure of Erv enzymes. However, one pseudo-dimer "subunit" has lost its cofactor and catalytic activity. In QSOX evolution, a further concatenation to a member of the protein disulfide isomerase family resulted in an enzyme capable of both disulfide formation and efficient transfer to substrate proteins.

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Uncoupling JAK3 activation induces apoptosis in human lymphoid cancer cells via regulating critical survival pathways.

Publication Date: 2010 Mar 4 PMID: 20211620
Authors: Nagy, Z. S. - Ross, J. A. - Rodriguez, G. - Bader, J. - Dimmock, J. - Kirken, R. A.
Journal: FEBS Lett

In the current work, we report that specific inhibition of JAK3 via NC1153 induces apoptosis of certain leukemia/lymphoma cell lines. Affymetrix microarray profiling following NC1153 treatment unveiled JAK3 dependent survival modulating pathways (p53, TGF-beta, TNFR and ER stress) in Kit225 cells. IL-2 responsive NC1153 target genes were regulated in human JAK3 positive, but not in JAK3 negative lymphoid tumor cells. Moreover, primary lymphoma samples revealed that a number of these genes were reciprocally regulated during disease progression and JAK3 inhibition suggesting that downstream targets of JAK3 could be exploited in the development of novel cancer treatment regimes.

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Channel character of uncoupling protein-mediated transport.

Publication Date: 2010 Mar 3 PMID: 20206627
Authors: Jezek, P. - Jaburek, M. - Garlid, K. D.
Journal: FEBS Lett

Mitochondrial uncoupling proteins (UCPs) are pure anion uniporters, which mediate fatty acid (FA) uniport leading to FA cycling. Protonated FAs then flip-flop back across the lipid bilayer. An existence of pure proton channel in UCPs is excluded by the equivalent flux-voltage dependencies for uniport of FAs and halide anions, which are best described by the Eyring barrier variant with a single energy well in the middle of two peaks. Experiments with FAs unable to flip and alkylsulfonates also support this view. Phylogenetically, UCPs took advantage of the common FA-uncoupling function of SLC25 family carriers and dropped their solute transport function.

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The structure of Get4 reveals an alpha-solenoid fold adapted for multiple interactions in tail-anchored protein biogenesis.

Publication Date: 2010 Mar 3 PMID: 20206626
Authors: Bozkurt, G. - Wild, K. - Amlacher, S. - Hurt, E. - Dobberstein, B. - Sinning, I.
Journal: FEBS Lett

Tail-anchored proteins play important roles in protein translocation, membrane fusion and apoptosis. They are targeted to the endoplasmic reticulum membrane via the guided-entry of tail-anchored proteins (Get) pathway. We present the 2A crystal structure of Get4 which participates in early steps of the Get pathway. The structure shows an alpha-solenoid fold with particular deviations from the regular pairwise arrangement of alpha-helices. A conserved hydrophobic groove accommodates the flexible C-terminal region in trans. The structural organization of the Get4 helical hairpin motifs provides a scaffold for protein-protein interactions in the Get pathway.

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Structure of the p53 C-terminus bound to 14-3-3: Implications for stabilization of the p53 tetramer.

Publication Date: 2010 Mar 3 PMID: 20206173
Authors: Schumacher, B. - Mondry, J. - Thiel, P. - Weyand, M. - Ottmann, C.
Journal: FEBS Lett

The adaptor protein 14-3-3 binds to and stabilizes the tumor suppressor p53 and enhances its anti-tumour activity. In the regulatory C-terminal domain of p53 several 14-3-3 binding motifs have been identified. Here, we report the crystal structure of the extreme C-terminus (residues 385-393, p53pT387) of p53 in complex with 14-3-3sigma at a resolution of 1.28A. p53pT387 is accommodated by 14-3-3 in a yet unrecognized fashion implying a rationale for 14-3-3 binding to the active p53 tetramer. The structure exhibits a potential binding site for small molecules that could stabilize the p53/14-3-3 protein complex suggesting the possibility for therapeutic intervention. STRUCTURED SUMMARY: MINT-7711943: 14-3-3 sigma (uniprotkb:P31947) and p53 (uniprotkb:P04637) bind (MI:0407) by X-ray crystallography (MI:0114) MINT-7711931: 14-3-3 sigma (uniprotkb:P31947) and p53 (uniprotkb:P04637) bind (MI:0407) by isothermal titration calorimetry (MI:0065).

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Computational prediction of nucleosome positioning by calculating the relative fragment frequency index of nucleosomal sequences.

Publication Date: 2010 Mar 3 PMID: 20206172
Authors: Ogawa, R. - Kitagawa, N. - Ashida, H. - Saito, R. - Tomita, M.
Journal: FEBS Lett

We developed an accurate method to predict nucleosome positioning from genome sequences by refining the previously developed method of Peckham et al. (2007) [19]. Here, we used the relative fragment frequency index we developed and a support vector machine to screen for nucleosomal and linker DNA sequences. Our twofold cross-validation revealed that the accuracy of our method based on the area under the receiver operating characteristic curve was 81%, whereas that of Peckham's method was 75% when both of two nucleosomal sequence data obtained from independent experiments were used for validation. We suggest that our method is more effective in predicting nucleosome positioning.

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Evidence that the C-terminus of OprM is involved in the assembly of the VceAB-OprM efflux pump.

Publication Date: 2010 Mar 3 PMID: 20206171
Authors: Bai, J. - Mosley, L. - Fralick, J. A.
Journal: FEBS Lett

Although the architecture of tripartite multiple drug resistance (MDR) efflux pumps of Gram-negative bacteria has been well characterized, the means by which the components recognize each other and assemble into a functional pump remains obscure. In this study we present evidence that the C-terminal domain of the Pseudomonas aeruginosa OprM and the alpha-helical hairpin domain of Vibrio cholerae VceA play an important role in the recognition/specificity/recruitment step in the assembly of a functional, VceAB-OprM chimeric efflux pump. To our knowledge, this is the first evidence directly linking the C-terminal domain of an outer membrane efflux protein to its recruitment during the assembly of a tripartite efflux pump.

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Ghrelin inhibits insulin secretion through the AMPK-UCP2 pathway in beta cells.

Publication Date: 2010 Mar 3 PMID: 20206170
Authors: Wang, Y. - Nishi, M. - Doi, A. - Shono, T. - Furukawa, Y. - Shimada, T. - Furuta, H. - Sasaki, H. - Nanjo, K.
Journal: FEBS Lett

Ghrelin inhibits insulin secretion partly via induction of IA-2beta. However, the orexigenic effect of ghrelin is mediated by the AMP-activated protein kinase (AMPK)-uncoupling protein 2 (UCP2) pathway. Here, we demonstrate that ghrelin's inhibitory effect on insulin secretion also occurs through the AMPK-UCP2 pathway. Ghrelin increased AMPK phosphorylation and UCP2 mRNA expression in MIN6 insulinoma cells. Overexpression or downregulation of UCP2 attenuated or enhanced insulin secretion, respectively. Furthermore, AMPK activator had a similar effect to ghrelin on UCP2 and insulin secretion in MIN6 cells. In conclusion, ghrelin's inhibitory effect on insulin secretion is partly mediated by the AMPK-UCP2 pathway, which is independent of the IA-2beta pathway.

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Vacuolar ion channels: Roles in plant nutrition and signalling.

Publication Date: 2010 Feb 25 PMID: 20188732
Authors: Isayenkov, S. - Isner, J. C. - Maathuis, F. J.
Journal: FEBS Lett

Vacuoles play various roles in many physiologically relevant processes in plants. Some of the more prominent are turgor provision, the storage of minerals and nutrients, and cellular signalling. To fulfil these functions a complement of membrane transporters is present at the tonoplast. Prolific patch clamp studies have shown that amongst these, both selective and non-selective ion channels participate in turgor regulation, nutrient storage and signalling. This article reviews the physiological roles, expression patterns and structure function properties of plant vacuolar anion and cation channels that are gated by voltage and ligands.

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Where do they come from? Insights into autophagosome formation.

Publication Date: 2010 Feb 25 PMID: 20188731
Authors: Hamasaki, M. - Yoshimori, T.
Journal: FEBS Lett

Autophagosomes (APs) are unique organelles that enwrap cytoplasmic components when necessary. APs then fuse with lysosomes and enclosed materials are degraded. Although approximately 30 autophagy-related genes (ATG) required for AP formation have been identified, fundamental questions on the membrane source or dynamics during the formation remain unresolved. Here, we present a comprehensive overview of the putative membrane sources identified to date.

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Parkin-mediated selective mitochondrial autophagy, mitophagy: Parkin purges damaged organelles from the vital mitochondrial network.

Publication Date: 2010 Feb 25 PMID: 20188730
Authors: Tanaka, A.
Journal: FEBS Lett

Cellular homeostasis is linked tightly to mitochondrial functions. Some damage to mitochondrial proteins and nucleic acids can lead to the depolarization of the inner mitochondrial membrane, thereby sensitizing impaired mitochondria for selective elimination by autophagy. Mitochondrial dysfunction is one of the key aspects of the pathobiology of neurodegenerative disease. Parkin, an E3 ligase located in the cytosol and originally discovered as mutated in monogenic forms of Parkinson's disease (PD), was found recently to translocate specifically to uncoupled mitochondria and to induce their autophagy.

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Comparative genomic and phylogenetic analysis of vitellogenin and other large lipid transfer proteins in metazoans.

Publication Date: 2010 Feb 24 PMID: 20188099
Authors: Hayward, A. - Takahashi, T. - Bendena, W. G. - Tobe, S. S. - Hui, J. H.
Journal: FEBS Lett

Vitellogenins and other large lipid transfer proteins (LLTP) are well known to play significant roles in the development, metabolism and reproduction of animals. Comparative genomics and phylogenetic analyses of LLTPs using the most comprehensive dataset in metazoans to date are carried out. Our analyses demonstrate that LLTP genes arose significantly earlier, and are more widespread than previously proposed - being present in numerous additional bilaterian and non-bilaterian lineages. A hypothesis is advanced that the most ancestral animal LLTP gene is Vtg, while loss of domains occurred at the bilaterians stem giving rise to apolipoprotein and microsomal triglyceride transfer proteins genes.

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Frontiers in membrane biochemistry.

Publication Date: 2010 Feb 24 PMID: 20188098
Authors: Sonnino, S. - Just, W.
Journal: FEBS Lett

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Mapping of the basic amino-acid residues responsible for tubulation and cellular protrusion by the EFC/F-BAR domain of pacsin2/Syndapin II.

Publication Date: 2010 Feb 24 PMID: 20188097
Authors: Shimada, A. - Takano, K. - Shirouzu, M. - Hanawa-Suetsugu, K. - Terada, T. - Toyooka, K. - Umehara, T. - Yamamoto, M. - Yokoyama, S. - Suetsugu, S.
Journal: FEBS Lett

The extended Fes-CIP4 homology (EFC)/FCH-BAR (F-BAR) domain tubulates membranes. Overexpression of the pacsin2 EFC/F-BAR domain resulted in tubular localization inside cells and deformed liposomes into tubules in vitro. We found that overexpression of the pacsin2 EFC/F-BAR domain induced cellular microspikes, with the pacsin2 EFC/F-BAR domain concentrated at the neck. The hydrophobic loops and the basic amino-acid residues on the concave surface of the pacsin2 EFC/F-BAR domain are essential for both the microspike formation and tubulation. Since the curvature of the neck of the microspike and that of the tubulation share similar geometry, the pacsin2 EFC/F-BAR domain is considered to facilitate both microspike formation and tubulation. STRUCTURED SUMMARY: MINT-7710892: EFCS pacsin2 (uniprotkb:Q9UNF0) and EFCS pacsin2 (uniprotkb:Q9UNF0) bind (MI:0407) by X-ray crystallography (MI:0114).

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S100 proteins regulate the interaction of Hsp90 with Cyclophilin 40 and FKBP52 through their tetratricopeptide repeats.

Publication Date: 2010 Feb 24 PMID: 20188096
Authors: Shimamoto, S. - Kubota, Y. - Tokumitsu, H. - Kobayashi, R.
Journal: FEBS Lett

S100 proteins are a subfamily of the EF-hand type calcium sensing proteins, the exact biological functions of which have not been clarified yet. In this work, we have identified Cyclophilin 40 (CyP40) and FKBP52 (called immunophilins) as novel targets of S100 proteins. These immunophilins contain a tetratricopeptide repeat (TPR) domain for Hsp90 binding. Using glutathione-S transferase pull-down assays and immunoprecipitation, we have demonstrated that S100A1 and S100A2 specifically interact with the TPR domains of FKBP52 and CyP40 in a Ca(2+)-dependent manner, and lead to inhibition of the CyP40-Hsp90 and FKBP52-Hsp90 interactions. These findings have suggested that the Ca(2+)/S100 proteins are TPR-targeting regulators of the immunophilins-Hsp90 complex formations. STRUCTURED SUMMARY: MINT-7710442: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by competition binding (MI:0405) MINT-7710192: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A1 (uniprotkb:P35467) by pull down (MI:0096) MINT-7710412: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by competition binding (MI:0405) MINT-7710374: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A2 (uniprotkb:P29034) by pull down (MI:0096) MINT-7710452: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with S100A2 (uniprotkb:P29034) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007) MINT-7710387: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A6 (uniprotkb:P06703) by pull down (MI:0096) MINT-7710279: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A1 (uniprotkb:P35467) by competition binding (MI:0405) MINT-7710224: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to Hsp90 (uniprotkb:P07900) by pull down (MI:0096) MINT-7710464: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with S100A6 (uniprotkb:P06703) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007) MINT-7710249: Cyp40 (uniprotkb:P26882) binds (MI:0407) to Hsp90 (uniprotkb:P07900) by pull down (MI:0096) MINT-7710422: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A6 (uniprotkb:P06703) by competition binding (MI:0405) MINT-7710348: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A2 (uniprotkb:P29034) by pull down (MI:0096) MINT-7710208: FKBP52 (uniprotkb:Q02790) binds (MI:0407) to S100A1 (uniprotkb:P35467) by pull down (MI:0096) MINT-7710265: Cyp40 (uniprotkb:P26882) physically interacts (MI:0915) with S100A1 (uniprotkb:P35467) by competition binding (MI:0405) MINT-7710361: Cyp40 (uniprotkb:P26882) binds (MI:0407) to S100A6 (uniprotkb:P06703) by pull down (MI:0096) MINT-7710476: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A2 (uniprotkb:P29034) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007) MINT-7710316: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A1 (uniprotkb:P35467) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007) MINT-7710432: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0915) with S100A2 (uniprotkb:P29034) by competition binding (MI:0405) MINT-7710488: FKBP52 (uniprotkb:Q02790) physically interacts (MI:0914) with S100A6 (uniprotkb:P06703) and Hsp90 (uniprotkb:P07900) by anti tag coimmunoprecipitation (MI:0007) MINT-7710329: S100A6 (uniprotkb:P14069) physically interacts (MI:0914) with FKBP52 (uniprotkb:P30416) and Cyp40 (uniprotkb:Q08752) by anti bait coimmunoprecipitation (MI:0006) MINT-7710295: Cyp40 (uniprotkb:P26882) physically interacts (MI:0914) with Hsp90 (uniprotkb:P07900) and S100A1 (uniprotkb:P35467) by anti tag coimmunoprecipitation (MI:0007).

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Protein kinase C-related kinase targets nuclear localization signals in a subset of class IIa histone deacetylases.

Publication Date: 2010 Feb 24 PMID: 20188095
Authors: Harrison, B. C. - Huynh, K. - Lundgaard, G. L. - Helmke, S. M. - Perryman, M. B. - McKinsey, T. A.
Journal: FEBS Lett

Class IIa histone deacetylases (HDACs) -4, -5, -7 and -9 undergo signal-dependent nuclear export upon phosphorylation of conserved serine residues that are targets for 14-3-3 binding. Little is known of other mechanisms for regulating the subcellular distribution of class IIa HDACs. Using a biochemical purification strategy, we identified protein kinase C-related kinase-2 (PRK2) as an HDAC5-interacting protein. PRK2 and the related kinase, PRK1, phosphorylate HDAC5 at a threonine residue (Thr-292) positioned within the nuclear localization signal (NLS) of the protein. HDAC7 and HDAC9 contain analogous sites that are phosphorylated by PRK, while HDAC4 harbors a non-phosphorylatable alanine residue at this position. We provide evidence to suggest that the unique phospho-acceptor cooperates with the 14-3-3 target sites to impair HDAC nuclear import. STRUCTURED SUMMARY: MINT-7710106:HDAC5 (uniprotkb:Q9UQL6) physically interacts (MI:0915) with PRK2 (uniprotkb:Q16513) by pull down (MI:0096).

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The role of PI3P phosphatases in the regulation of autophagy.

Publication Date: 2010 Feb 24 PMID: 20188094
Authors: Vergne, I. - Deretic, V.
Journal: FEBS Lett

Autophagy initiation is strictly dependent on phosphatidylinositol 3-phosphate (PI3P) synthesis. PI3P production is under tight control of PI3Kinase, hVps34, in complex with Beclin-1. Mammalian cells express several PI3P phosphatases that belong to the myotubularin family. Even though some of them have been linked to serious human diseases, their cellular function is largely unknown. Two recent studies indicate that PI3P metabolism involved in autophagy initiation is further regulated by the PI3P phosphatases Jumpy and MTMR3. Additional pools of PI3P, upstream of mTOR and on the endocytic pathway, may modulate autophagy indirectly, suggesting that other PI3P phosphatases might be involved in this process. This review sums up our knowledge on PI3P phosphatases and discusses the recent progress on their role in autophagy.

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Voltage dependent anion-selective channel (VDAC) in the plasma membrane.

Publication Date: 2010 Feb 23 PMID: 20184885
Authors: De Pinto, V. - Messina, A. - Lane, D. J. - Lawen, A.
Journal: FEBS Lett

Voltage dependent anion channels (VDACs) have originally been characterised as mitochondrial porins. Starting in the late 1980s, however, evidence began to accumulate that VDACs can also be expressed in plasma membranes. In this review, we briefly revisit the historical milestones in the discovery of plasma membrane-bound VDAC, and we critically analyse the evidence for VDAC plasma membrane localization obtained from various purification strategies and recently from plasma membrane proteomics studies. We discuss the possible biological function and relevance of VDAC in the plasma membrane and finally discuss a hypothetical model of how VDAC may be targeted to the plasma membrane.

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Autophagy.

Publication Date: 2010 Feb 23 PMID: 20184884
Authors: Mizushima, N.
Journal: FEBS Lett

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Ceramide-rich platforms in transmembrane signaling.

Publication Date: 2010 Feb 20 PMID: 20178791
Authors: Stancevic, B. - Kolesnick, R.
Journal: FEBS Lett

Recent evidence suggests that ceramide regulates stress signaling via reorganization of the plasma membrane. The focus of this review will be to discuss the mechanism by which acid sphingomyelinase (ASMase)-generated ceramide initiates transmembrane signaling in the plasma membrane exoplasmic leaflet. In particular, we review the unique biophysical properties of ceramide that render it proficient in formation of signaling domains termed ceramide-rich platforms (CRPs), and the role of CRPs in the pathophysiology of various diseases. The biomedical significance of CRPs makes these structures an attractive therapeutic target.

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Dimerisation and structural integrity of Heparin Binding Hemagglutinin A from Mycobacterium tuberculosis: Implications for bacterial agglutination.

Publication Date: 2010 Feb 20 PMID: 20178790
Authors: Esposito, C. - Carullo, P. - Pedone, E. - Graziano, G. - Vecchio, P. D. - Berisio, R.
Journal: FEBS Lett

Heparin Binding Hemagglutinin A (HBHA) is hitherto the sole virulence factor associated with tuberculosis dissemination from the lungs, the site of primary infection, to epithelial cells. We have previously reported the solution structure of HBHA, a dimeric and elongated molecule. Since oligomerisation of HBHA is associated with its ability to induce bacterial agglutination, we investigated this process using experimental and modelling techniques. We here identified a short segment of HBHA whose presence is mandatory for the stability of folded conformation, whose denaturation is a reversible two-state process. Our data suggest that agglutination-driven cell-cell interactions do not occur via association of HBHA monomers, nor via association of HBHA dimers and open the scenario to a possible trans-dimerisation process. STRUCTURED SUMMARY: MINT-7709940, MINT-7709948: HBHA (uniprotkb:A5TZK3) and HBHA (uniprotkb:A5TZK3) bind (MI:0407) by circular dichroism (MI:0016)MINT-7709966: HBHA (uniprotkb:A5TZK3) and HBHA (uniprotkb:A5TZK3) bind (MI:0407) by biophysical (MI:0013)MINT-7709955: HBHA (uniprotkb:A5TZK3) and HBHA (uniprotkb:A5TZK3) bind (MI:0407) by dynamic light scattering (MI:0038).

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Large conductance, Ca(2+)-activated K(+) channels (BK(Ca)) and arteriolar myogenic signaling.

Publication Date: 2010 Feb 20 PMID: 20178789
Authors: Hill, M. A. - Yang, Y. - Ella, S. R. - Davis, M. J. - Braun, A. P.
Journal: FEBS Lett

Myogenic, or pressure-induced, vasoconstriction is critical for local blood flow autoregulation. Underlying this vascular smooth muscle (VSM) response are events including membrane depolarization, Ca(2+) entry and mobilization, and activation of contractile proteins. Large conductance, Ca(2+)-activated K(+) channel (BK(Ca)) has been implicated in several of these steps including, (1) channel closure causing membrane depolarization, and (2) channel opening causing hyperpolarization to oppose excessive pressure-induced vasoconstriction. As multiple mechanisms regulate BK(Ca) activity (subunit composition, membrane potential (Em) and Ca(2+) levels, post-translational modification) tissue level diversity is predicted. Importantly, heterogeneity in BK(Ca) channel activity may contribute to tissue-specific differences in regulation of myogenic vasoconstriction, allowing local hemodynamics to be matched to metabolic requirements. Knowledge of such variability will be important to exploiting the BK(Ca) channel as a therapeutic target and understanding systemic effects of its pharmacological manipulation.

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Mitochondrial ion channels as therapeutic targets.

Publication Date: 2010 Feb 20 PMID: 20178788
Authors: Peixoto, P. M. - Ryu, S. Y. - Kinnally, K. W.
Journal: FEBS Lett

The study of mitochondrial ion channels changed our perception of these double-wrapped organelles from being just the power house of a cell to the guardian of a cell's fate. Mitochondria communicate with the cell through these special channels. Most of the time, the message is encoded by ion flow across the mitochondrial outer and inner membranes. Potassium, sodium, calcium, protons, nucleotides, and proteins traverse the mitochondrial membranes in an exquisitely regulated manner to control a myriad of processes, from respiration and mitochondrial morphology to cell proliferation and cell death. This review is an update on both well established and putative mitochondrial channels regarding their composition, function, regulation, and therapeutic potential.

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Hierarchical organization of the plasma membrane: Investigations by single-molecule tracking vs. fluorescence correlation spectroscopy.

Publication Date: 2010 Feb 20 PMID: 20178787
Authors: Kusumi, A. - Shirai, Y. M. - Koyama-Honda, I. - Suzuki, K. G. - Fujiwara, T. K.
Journal: FEBS Lett

Single-molecule tracking and fluorescence correlation spectroscopy (FCS) applied to the plasma membrane in living cells have allowed a number of unprecedented observations, thus fostering a new basic understanding of molecular diffusion, interaction, and signal transduction in the plasma membrane. It is becoming clear that the plasma membrane is a heterogeneous entity, containing diverse structures on nano-meso-scales (2-200nm) with a variety of lifetimes, where certain membrane molecules stay together for limited durations. Molecular interactions occur in the time-dependent inhomogeneous two-dimensional liquid of the plasma membrane, which might be a key for plasma membrane functions.

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Pharmacology of mitochondrial potassium channels: dark side of the field.

Publication Date: 2010 Feb 20 PMID: 20178786
Authors: Szewczyk, A. - Kajma, A. - Malinska, D. - Wrzosek, A. - Bednarczyk, P. - Zablocka, B. - Dolowy, K.
Journal: FEBS Lett

Mitochondrial potassium channels play an important role in cytoprotection. Potassium channels in the inner mitochondrial membrane are modulated by inhibitors and activators (potassium channel openers) previously described for plasma membrane potassium channels. The majority of mitochondrial potassium channel modulators exhibit a broad spectrum of off-target effects. These include uncoupling properties, inhibition of the respiratory chain and effects on cellular calcium homeostasis. Therefore, the rational application of channel inhibitors or activators is crucial to understanding the cellular consequences of mitochondrial channel inhibition or activation. Moreover, understanding their side-effects should facilitate the design of a specific mitochondrial channel opener with cytoprotective properties. In this review, we discuss the complex interactions of potassium channel inhibitors and activators with cellular structures.

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Proton-conductivity assay of plugged and unplugged MotA/B proton channel by cytoplasmic pHluorin expressed in Salmonella.

Publication Date: 2010 Feb 21 PMID: 20178785
Authors: Morimoto, Y. V. - Che, Y. S. - Minamino, T. - Namba, K.
Journal: FEBS Lett

MotA and MotB form the proton-channel complex of the proton-driven bacterial flagellar motor. A plug segment of Escherichia coli MotB suppresses proton leakage through the MotA/B complex when it is not assembled into the motor. Using a ratiometric pH indicator protein, pHluorin, we show that the proton-conductivity of a Salmonella MotA/B complex not incorporated into the motor is two orders of magnitude lower than that of a complex that is incorporated and activated. This leakage is, however, significant enough to change the cytoplasmic pH to a level at which the chemotaxis signal transduction system responds.

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Crystal structure of the transcriptional activator HlyU from Vibrio vulnificus CMCP6.

Publication Date: 2010 Feb 21 PMID: 20178784
Authors: Nishi, K. - Lee, H. J. - Park, S. Y. - Bae, S. J. - Lee, S. E. - Adams, P. D. - Rhee, J. H. - Kim, J. S.
Journal: FEBS Lett

HlyU is a transcription factor of the ArsR/SmtB family and activates the expression of the pathogenic Vibrio vulnificus RTX toxin. In contrast to the other metal-responding ArsR/SmtB proteins, HlyU does not sense metal ions. To provide its structural information, we elucidated the crystal structure of HlyU from V. vulnificus CMCP6 (HlyU_Vv). The monomeric HlyU_Vv architecture of five alpha-helices and two beta-strands, some of which constitute a typical DNA-binding winged helix-turn-helix (wHTH) motif, is very similar to that of other transcription regulators. Nonetheless, the homo-dimeric HlyU_Vv structure shows several different, three-dimensional features in the spatial position and the detailed dimeric interaction, which were not observed in the modeling study based on the same protein family and sequence similarity. STRUCTURED SUMMARY: MINT-7710072, MINT-7710086: HlyU_Vv (uniprotkb:Q8DES3) and HlyU_Vv (uniprotkb:Q8DES3) bind (MI:0407) by X-ray crystallography (MI:0114).

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New design platform for malonyl-CoA-acyl carrier protein transacylase.

Publication Date: 2010 Feb 19 PMID: 20176020
Authors: Hong, S. K. - Kim, K. H. - Park, J. K. - Jeong, K. W. - Kim, Y. - Kim, E. E.
Journal: FEBS Lett

Malonyl-CoA-acyl carrier protein transacylase (MCAT) transfers the malonyl group from malonyl-CoA to holo-acyl carrier protein (ACP), and since malonyl-ACP is a key building block for fatty-acid biosynthesis it is considered as a promising antibacterial target. The crystal structures of MCAT from Staphylococcus aureus and Streptococcus pneumoniae have been determined at 1.46 and 2.1A resolution, respectively. In the SaMCAT structure, the N-terminal expression peptide of a neighboring molecule running in the opposite direction of malonyl-CoA makes extensive interactions with the highly conserved "Gly-Gln-Gly-Ser-Gln" stretch, suggesting a new design platform. Mutagenesis results suggest that Ser91 and His199 are the catalytic dyad.

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Mitochondrial respiratory chain involvement in peroxiredoxin 3 oxidation by phenethyl isothiocyanate and auranofin.

Publication Date: 2010 Feb 19 PMID: 20176019
Authors: Brown, K. K. - Cox, A. G. - Hampton, M. B.
Journal: FEBS Lett

Mitochondrial peroxiredoxin 3 (Prx 3) is rapidly oxidized in cells exposed to phenethyl isothiocyanate (PEITC) and auranofin (AFN), but the mechanism of oxidation is unclear. Using HL-60 cells deplete of mitochondrial DNA we show that peroxiredoxin 3 oxidation and cytotoxicity requires a functional respiratory chain. Thioredoxin reductase (TrxR) could be inhibited by up to 90% by auranofin without direct oxidation of peroxiredoxin 3. However, inhibition of thioredoxin reductase promoted peroxiredoxin 3 oxidation and cytotoxicity in combination with phenethyl isothiocyanate or antimycin A. We conclude that rapid peroxiredoxin 3 oxidation occurs as a consequence of increased oxidant production from the mitochondrial respiratory chain.

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UV-induced downregulation of the CDC25B protein in human cells.

Publication Date: 2010 Feb 19 PMID: 20176018
Authors: Lemaire, M. - Ducommun, B. - Nebreda, A. R.
Journal: FEBS Lett

The CDC25B phosphatase regulates the activation of CDK1-Cyclin B at the onset of mitosis, being a key target of the checkpoint pathways activated by cellular stress and DNA damage. Previous work has reported that checkpoint activation induces the sequestration of CDC25B in the cytoplasm. Here we show that in response to UV irradiation, the levels of CDC25B protein can be downregulated independently of classical checkpoints pathways such as p53, ATM/ATR and p38 MAPK. We also show that translational repression mediated by eIF2alpha phosphorylation regulates CDC25B expression levels. Taken together, our results illustrate a new mechanism of CDC25B regulation in response to stress.

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Cu,Zn-superoxide dismutase is required for cell wall structure and for tolerance to cell wall-perturbing agents in Saccharomyces cerevisiae.

Publication Date: 2010 Feb 19 PMID: 20176017
Authors: Liu, X. - Zhang, X. - Zhang, Z.
Journal: FEBS Lett

Here we report that deletion of SOD1, the Cu,Zn-superoxide dismutase in Saccharomyces cerevisiae is sensitive to cell wall-perturbing agents, such as Calcofluor white and Congo red. The sensitivity was restored by retransformation with wild type SOD1 or the addition of N-acetylcysteine or reduced glutathione to the medium. Additionally, the accumulation of reactive oxygen species was observed in sod1Delta mutant in the presence of Calcofluor white or Congo red. Cell wall analysis indicated an increase of cell wall chitin and cell wall thickness in sod1Delta mutant compared to wild type. These results indicate a novel direct connection between antioxidative functions and cell wall homeostasis.

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NSF independent fusion of Salmonella-containing late phagosomes with early endosomes.

Publication Date: 2010 Feb 20 PMID: 20176016
Authors: Parashuraman, S. - Madan, R. - Mukhopadhyay, A.
Journal: FEBS Lett

Initial characterizations of live-Salmonella-containing early (LSEP) and late phagosomes (LSLP) in macrophages show that both phagosomes retain Rab5 and EEA1. In addition, LSEP specifically contain transferrin receptor whereas LSLP possess relatively more rabaptin-5. In contrast to LSLP, late-Salmonella-containing vacuoles in epithelial cells show significantly reduced levels of Rab5 and EEA1. Subsequent results demonstrate that both phagosomes efficiently fuse with early endosomes (EE). In contrast to LSEP, fusion between LSLP and EE is insensitive to ATPgammaS treatment. Furthermore, LSLP fuses with EE in absence of NEM-sensitive fusion factor (NSF) as well as in the presence of NSF:D1EQ mutant demonstrating that LSLP fusion with EE is NSF independent.

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The antiviral protein viperin is a radical SAM enzyme.

Publication Date: 2010 Feb 20 PMID: 20176015
Authors: Duschene, K. S. - Broderick, J. B.
Journal: FEBS Lett

Viperin, an interferon-inducible antiviral protein, is shown to bind an iron-sulfur cluster, based on iron analysis as well as UV-Vis and electron paramagnetic resonance spectroscopic data. The reduced protein contains a [4Fe-4S](1+) cluster whose g-values are altered upon addition of S-adenosylmethionine (SAM), consistent with SAM coordination to the cluster. Incubation of reduced viperin with SAM results in reductive cleavage of SAM to produce 5'-deoxyadenosine (5'-dAdo), a reaction characteristic of the radical SAM superfamily. The 5'-dAdo cleavage product was identified by a combination of HPLC and mass spectrometry analysis.

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Discovery of a putative acetoin dehydrogenase complex in the hyperthermophilic archaeon Sulfolobus solfataricus.

Publication Date: 2010 Feb 18 PMID: 20171216
Authors: Payne, K. A. - Hough, D. W. - Danson, M. J.
Journal: FEBS Lett

Like many other aerobic archaea, the hyperthermophile Sulfolobus solfataricus possesses a gene cluster encoding components of a putative 2-oxoacid dehydrogenase complex. In the current paper, we have cloned and expressed the first two genes of this cluster and demonstrate that the protein products form an alpha(2)beta(2) hetero-tetramer possessing the catalytic activity characteristic of the first component enzyme of an acetoin dehydrogenase multienzyme complex. This represents the first report of an acetoin multienzyme complex in archaea, and contrasts with the branched-chain 2-oxoacid dehydrogenase complex activities characterised in two other archaea, Thermoplasma acidophilum and Haloferax volcanii.

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High density lipoprotein inhibits the activation of sterol regulatory element-binding protein-1 in cultured cells.

Publication Date: 2010 Feb 18 PMID: 20171215
Authors: Yoshida, M. - Harada, N. - Yoshida, K. - Nakagawa, T. - Shimohata, T. - Mawatari, K. - Takahashi, A. - Sakaue, H. - Nakaya, Y.
Journal: FEBS Lett

A link between cellular uptake of high density lipoprotein (HDL) and regulation of sterol regulatory element-binding protein-1 (SREBP-1) was investigated in vitro. HDL decreased nuclear SREBP-1 levels as well as SREBP-1 target gene expression in HepG2 and HEK293 cells. However, HDL did not repress an exogenously expressed, constitutively active form of SREBP-1. HDL increased cellular cholesterol levels, and cellular cholesterol depletion by methyl-beta-cyclodextrin abolished the effects of HDL. These results suggest that HDL inhibits the activation of SREBP-1 through a cholesterol-dependent mechanism, which may play an important role in regulating lipid synthetic pathways mediated by SREBP-1.

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Unraveling evolutionary constraints: A heterogeneous conservation in dynamics of the titin Ig domains.

Publication Date: 2010 Feb 18 PMID: 20171214
Authors: Lukman, S. - Grant, G. H. - Bui, J. M.
Journal: FEBS Lett

The giant protein titin, which comprises immunoglobulin (Ig) domains, acts as a bidirectional spring in muscle. The unfolding of Ig domains has been extensively studied, but their dynamics under native states have not been well-characterized. We performed molecular dynamics simulation on a single titin Ig domain and multi-domains. Mobile regions displaying concerted motions were identified. The dynamics of Ig domains are constrained by evolutionary pressures, in such a way that global dominant motion is conserved, yet different flexibilities within Ig domains and in linkers connecting neighbouring domains were observed. We explain these heterogeneous conserved dynamics in relation to sequence conservation across species and the sequence diversity among neighbouring Ig domains.

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N-terminal PH domain and C-terminal auto-inhibitory region of CKIP-1 coordinate to determine its nucleus-plasma membrane shuttling.

Publication Date: 2010 Feb 18 PMID: 20171213
Authors: Xi, S. - Tie, Y. - Lu, K. - Zhang, M. - Yin, X. - Chen, J. - Xing, G. - Tian, C. - Zheng, X. - He, F. - Zhang, L.
Journal: FEBS Lett

The pleckstrin homology (PH) domain-containing protein casein kinase 2 interacting protein-1 (CKIP-1) plays an important role in regulation of bone formation and muscle differentiation. How CKIP-1 localization is determined remains largely unclear. We observed that isolated CKIP-1-PH domain was predominantly localized in the nucleus and the C-terminus of CKIP-1 counteracted its nuclear localization. The net charge of basic residues and a serine-rich motif within the PH domain plays a pivotal role in the localization switch of both full-length CKIP-1 and the isolated PH domain. We propose that the N-terminal PH domain and C-terminal auto-inhibitory region of CKIP-1 coordinate to determine its subcellular localization and the nucleus-plasma membrane shuttling.

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Effects of human T-cell leukemia virus type 1 (HTLV-1) p13 on mitochondrial K(+) permeability: A new member of the viroporin family?

Publication Date: 2010 Feb 17 PMID: 20170654
Authors: Silic-Benussi, M. - Marin, O. - Biasiotto, R. - D'Agostino, D. M. - Ciminale, V.
Journal: FEBS Lett

Human T-cell leukemia virus type-1 (HTLV-1) encodes a mitochondrial protein named p13. p13 mediates an inward K(+) current in isolated mitochondria that leads to mitochondrial swelling, depolarization, increased respiratory chain activity and reactive oxygen species (ROS) production. These effects trigger the opening of the permeability transition pore and are dependent on the presence of K(+) and on the amphipathic alpha helical domain of p13. In the context of cells, p13 acts as a sensitizer to selected apoptotic stimuli. Although it is not known whether p13 influences the activity of endogenous K(+) channels or forms a channel itself, it shares some structural and functional analogies with viroporins, a class of small integral membrane proteins that form pores and alter membrane permeability.

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GABAA receptor subunit beta1 is involved in the formation of protease-resistant prion protein in prion-infected neuroblastoma cells.

Publication Date: 2010 Feb 14 PMID: 20159020
Authors: Kimura, T. - Ishikawa, K. - Sakasegawa, Y. - Teruya, K. - Sata, T. - Schatzl, H. - Doh-Ura, K.
Journal: FEBS Lett

gamma-Aminobutyric acid type A (GABAA) receptor beta1 (gabrb1), a subunit of GABAA receptors involved in inhibitory effects on neurotransmission, was found to associate with the formation of protease-resistant prion protein in prion-infected neuroblastoma cells. Silencing of gabrb1 gene expression significantly decreased the abnormal prion protein level but paradoxically increased the normal prion protein level. Treatment with a gabrb1-specific inhibitor, salicylidene salicylhydrazide, dose-dependently decreased the abnormal prion protein level, but silencing of other GABAA receptor subunits' gene expression and treatments with the receptor antagonists and agonists did not. Therefore, gabrb1 involvement in abnormal prion protein formation is independent of GABAA receptors.

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Site-directed mutagenesis and PBAN activation of the Helicoverpa zea PBAN-receptor.

Publication Date: 2010 Feb 14 PMID: 20159019
Authors: Choi, M. Y. - Jurenka, R. A.
Journal: FEBS Lett

Pheromone biosynthesis-activating neuropeptide (PBAN) and pyrokinins belong to a family of insect peptide hormones that have a common FXPRLamide C-terminal ending. The G-protein-coupled receptors (GPCRs) for this peptide family were first identified from a moth and Drosophila with sequence similarity to neuromedin U receptors from vertebrates. We have characterized the PBAN-receptor (PBAN-R or PR) active binding domains using chimeric GPCRs and proposed that extracellular loop 3 is critical for ligand selection. Here, we characterized the 3rd extracellular domain of PBAN-R through site-directed point mutations. Results are discussed in context of the structural features required for receptor activation using receptor activation experiments and in silico computational modeling. This research will help in characterizing these receptors towards a goal of finding agonists and/or antagonists for PBAN/pyrokinin receptors.

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Identification and characterization of the novel protein CCDC106 that interacts with p53 and promotes its degradation.

Publication Date: 2010 Feb 14 PMID: 20159018
Authors: Zhou, J. - Qiao, X. - Xiao, L. - Sun, W. - Wang, L. - Li, H. - Wu, Y. - Ding, X. - Hu, X. - Zhou, C. - Zhang, J.
Journal: FEBS Lett

The putative CCDC106 protein was previously identified as a p53-interacting partner by automated yeast two-hybrid screening, but its sequence and function have not been validated experimentally. Here, we identified three variant transcripts of the CCDC106 gene; these transcripts differ in their second exons due to the use of different splice acceptor site, but encode an identical protein of 280 residues. A bipartite nuclear localisation signal at residues 151-164 mediates the nuclear localisation of CCDC106. Double immunofluorescence staining revealed the colocalisation of endogenous CCDC106 and p53 protein in nuclei. The in vivo interaction between CCDC106 and p53 was confirmed by a co-immunoprecipitation assay. Furthermore, we demonstrated that CCDC106 promotes the degradation of p53 protein and inhibits its transactivity. STRUCTURED SUMMARY: MINT-7681390: CCDC106 (uniprotkb:Q9BWC9) physically interacts (MI:0915) with p53 (uniprotkb:P04637) by anti tag co-immunoprecipitation (MI:0007) MINT-7681212: p53 (uniprotkb:P04637) and CCDC106 (uniprotkb:Q9BWC9) colocalise (MI:0403) by fluorescence microscopy (MI:0416).

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Recognition of cellooligosaccharides by a family 28 carbohydrate-binding module.

Publication Date: 2010 Feb 14 PMID: 20159017
Authors: Tsukimoto, K. - Takada, R. - Araki, Y. - Suzuki, K. - Karita, S. - Wakagi, T. - Shoun, H. - Watanabe, T. - Fushinobu, S.
Journal: FEBS Lett

The crystal structures of a carbohydrate-binding module (CBM) family 28 domain of endoglucanase Cel5A from Clostridium josui have been determined in ligand-free and complex forms with cellobiose, cellotetraose, and cellopentaose as the first complex structures of this family. In the cleft of a beta-sandwich fold, the ligands are recognized by stacking interactions and hydrogen bonds. Conformations of the bound cellooligosaccharides are similar to those in crystals and solution but clearly different from the cellulose structure. Interestingly, the glucan chain bound on CBM28 is in the opposite direction of that bound to CBM17, although these families share significant structural similarity.

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Regulation of ceramide channels by Bcl-2 family proteins.

Publication Date: 2010 Feb 14 PMID: 20159016
Authors: Ganesan, V. - Colombini, M.
Journal: FEBS Lett

Mitochondrial outer membrane permeabilization to proteins, an irreversible step in apoptosis by which critical proteins are released, is tightly regulated by Bcl-2 family proteins. The exact nature of the release pathway is still undefined. Ceramide is an important sphingolipid, involved in various cellular processes including apoptosis. Here we describe the structural properties of ceramide channels and their regulation by the anti-apoptotic and pro-apoptotic proteins of the Bcl-2 family. The evolutionarily conserved regulation of ceramide channels by Bcl-2 family proteins, consistent with their role in apoptosis, lends credibility to the notion that ceramide channels constitute the protein release pathway.

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TPCs: Endolysosomal channels for Ca(2+) mobilization from acidic organelles triggered by NAADP.

Publication Date: 2010 Feb 14 PMID: 20159015
Authors: Zhu, M. X. - Ma, J. - Parrington, J. - Galione, A. - Mark Evans, A.
Journal: FEBS Lett

Two-pore channels (TPCs or TPCNs) are novel members of the large superfamily of voltage-gated cation channels with slightly higher sequence homology to the pore-forming subunits of voltage-gated Ca(2+) and Na(+) channels than most other members. Recent studies demonstrate that TPCs locate to endosomes and lysosomes and form Ca(2+) release channels that respond to activation by the Ca(2+) mobilizing messenger, nicotinic acid adenine dinucleotide phosphate (NAADP). With multiple endolysosomal targeted NAADP receptors now identified, important new insights into the regulation of endolysosomal function in health and disease will therefore be unveiled.

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Design and characterization of a constitutively open KcsA.

Publication Date: 2010 Feb 12 PMID: 20153331
Authors: Cuello, L. G. - Jogini, V. - Cortes, D. M. - Sompornpisut, A. - Purdy, M. D. - Wiener, M. C. - Perozo, E.
Journal: FEBS Lett

The molecular nature of the structure responsible for proton sensitivity in KcsA has been identified as a charge cluster that surrounds the inner helical bundle gate. Here, we show that this proton sensor can be modified to engineer a constitutively open form of KcsA, amenable to functional, spectroscopic and structural analyses. By combining charge neutralizations for all acidic and basic residues in the cluster at positions 25, 117-122 and 124 (but not E118), a mutant KcsA is generated that displays constitutively open channel activity up to pH 9. The structure of this mutant revealed that full opening appears to be inhibited by lattice forces since the activation gate seems to be only on the early stages of opening.

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PINK1 is recruited to mitochondria with parkin and associates with LC3 in mitophagy.

Publication Date: 2010 Feb 12 PMID: 20153330
Authors: Kawajiri, S. - Saiki, S. - Sato, S. - Sato, F. - Hatano, T. - Eguchi, H. - Hattori, N.
Journal: FEBS Lett

Mutations in PTEN-induced putative kinase 1 (PINK1) cause recessive form of Parkinson's disease (PD). PINK1 acts upstream of parkin, regulating mitochondrial integrity and functions. Here, we show that PINK1 in combination with parkin results in the perinuclear mitochondrial aggregation followed by their elimination. This elimination is reduced in cells expressing PINK1 mutants with wild-type parkin. Although wild-type PINK1 localizes in aggregated mitochondria, PINK1 mutants localization remains diffuse and mitochondrial elimination is not observed. This phenomenon is not observed in autophagy-deficient cells. These results suggest that mitophagy controlled by the PINK1/parkin pathway might be associated with PD pathogenesis. STRUCTURED SUMMARY: MINT-7557195: PINK1 (uniprotkb:Q9BXM7) physically interacts (MI:0915) with LC3 (uniprotkb:Q9GZQ8) by anti tag coimmunoprecipitation (MI:0007) MINT-7557109: LC3 (uniprotkb:Q9GZQ8) and PINK1 (uniprotkb:Q9BXM7) colocalize (MI:0403) by fluorescence microscopy (MI:0416) MINT-7557121: tom20 (uniprotkb:Q15388) and PINK1 (uniprotkb:Q9BXM7) colocalize (MI:0403) by fluorescence microscopy (MI:0416) MINT-7557138: parkin (uniprotkb:O60260), PINK1 (uniprotkb:Q9BXM7) and tom20 (uniprotkb:Q15388) colocalize (MI:0403) by fluorescence microscopy (MI:0416) MINT-7557173: LC3 (uniprotkb:Q9GZQ8) physically interacts (MI:0915) with PINK1 (uniprotkb:Q9BXM7) by anti bait coimmunoprecipitation (MI:0006).

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Reconstitution of the mitochondrial Hsp70 (mortalin)-p53 interaction using purified proteins - Identification of additional interacting regions.

Publication Date: 2010 Feb 12 PMID: 20153329
Authors: Iosefson, O. - Azem, A.
Journal: FEBS Lett

Previous studies have shown that the mammalian mitochondrial 70 kDa heat-shock protein (mortalin) can also be detected in the cytosol. Cytosolic mortalin binds p53 and by doing so, prevents translocation of the tumor suppressor into the nucleus. In this study, we developed a novel binding assay, using purified proteins, for tracking the interaction between p53 and mortalin. Our results reveal that: (i) P53 binds to the peptide-binding site of mortalin which enhances the ability of the former to bind DNA. (ii) An additional previously unknown binding site for mortalin exists within the C-terminal domain of p53. STRUCTURED SUMMARY: MINT-7557591: p53 (uniprotkb:P04637) binds (MI:0407) to DnaK (uniprotkb:P0A6Y8) by affinity chromatography technology (MI:0004) MINT-7557644: mortalin (uniprotkb:P38646) binds (MI:0407) to p53 (uniprotkb:P04637) by pull down (MI:0096) MINT-7557580, MINT-7557611: p53 (uniprotkb:P04637) binds (MI:0407) to mortalin (uniprotkb:P38646) by affinity chromatography technology (MI:0004).

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Signal transduction to the permeability transition pore.

Publication Date: 2010 Feb 11 PMID: 20153328
Authors: Rasola, A. - Sciacovelli, M. - Pantic, B. - Bernardi, P.
Journal: FEBS Lett

The permeability transition pore (PTP) is an inner mitochondrial membrane channel that has been thoroughly characterized functionally, yet remains an elusive molecular entity. The best characterized PTP-regulatory component, cyclophilin (CyP) D, is a matrix protein that favors pore opening. CyP inhibitors, CyP-D null animals, and in situ PTP readouts have established the role of PTP as an effector mechanism of cell death, and the growing definition of PTP signalling mechanisms. This review briefly covers the functional features of the PTP and the role played by its dysregulation in disease pathogenesis. Recent progress on PTP modulation by kinase/phosphatase signal transduction is discussed, with specific emphasis on hexokinase and on the Akt-ERK-GSK3 axis, which might modulate the PTP through CyP-D phosphorylation.

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Heat-shock protein 70 binds to a novel sequence in 5' UTR of tumor suppressor SMAR1 and regulates its mRNA stability upon Prostaglandin A2 treatment.

Publication Date: 2010 Feb 11 PMID: 20153327
Authors: Pavithra, L. - Sreenath, K. - Singh, S. - Chattopadhyay, S.
Journal: FEBS Lett

Here, we report Prostaglandin A2 (PGA2) induced binding of HSP70 to a novel site on phi1 SMAR1 5' UTR which stabilizes the wild type transcript and leads to subsequent increase in SMAR1 protein levels. SMAR1 mediated cell cycle arrest is perturbed in PGA2-treated cells when HSP70 is knocked-down. Contrarily HSP70, unlike SMAR1, is overexpressed in breast cancers. We demonstrate that this is because of the inability of HSP70 to bind to the phi17 SMAR1 UTR variant which is the predominant form in breast cancers.

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Physiological significance of selective degradation of p62 by autophagy.

Publication Date: 2010 Feb 12 PMID: 20153326
Authors: Komatsu, M. - Ichimura, Y.
Journal: FEBS Lett

Autophagy is a highly conserved bulk protein degradation pathway responsible for the turnover of long-lived proteins, disposal of damaged organelles, and clearance of aggregate-prone proteins. Thus, inactivation of autophagy results in cytoplasmic protein inclusions, which are composed of misfolded proteins and excess accumulation of deformed organelles, leading to liver injury, diabetes, myopathy, and neurodegeneration. Although autophagy has been considered non-selective, growing lines of evidence indicate the selectivity of autophagy in sorting vacuolar enzymes and in the removal of aggregate-prone proteins, unwanted organelles and microbes. Such selectivity by autophagy enables diverse cellular regulations, similar to the ubiquitin-proteasome pathway. In this review, we introduce the selective turnover of the ubiquitin- and LC3-binding protein 'p62' through autophagy and discuss its physiological significance.

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RNA interference-mediated suppression of xanthine dehydrogenase reveals the role of purine metabolism in drought tolerance in Arabidopsis.

Publication Date: 2010 Feb 11 PMID: 20153325
Authors: Watanabe, S. - Nakagawa, A. - Izumi, S. - Shimada, H. - Sakamoto, A.
Journal: FEBS Lett

We have previously demonstrated that RNA interference-mediated suppression of xanthine dehydrogenase (XDH), the rate-limiting enzyme in purine degradation, causes defects in the normal growth and development of Arabidopsis thaliana. Here, we investigated a possible role for XDH in drought tolerance, since this enzyme is also implicated in plant stress responses and acclimatization. When XDH-suppressed lines were subjected to drought stress, plant growth was markedly reduced in conjunction with significantly enhanced cell death and H(2)O(2) accumulation. This drought-hypersensitive phenotype was reversed by pretreatment with exogenous uric acid, the catalytic product of XDH. These results suggest that fully functional purine metabolism plays a role in the Arabidopsis drought acclimatization.

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The protein encoded by the functional steroid receptor RNA activator is a new modulator of ER alpha transcriptional activity.

Publication Date: 2010 Feb 11 PMID: 20153324
Authors: Chooniedass-Kothari, S. - Vincett, D. - Yan, Y. - Cooper, C. - Hamedani, M. K. - Myal, Y. - Leygue, E.
Journal: FEBS Lett

The steroid receptor RNA activator gene (SRA1) encodes for a functional RNA (SRA) as well as a protein (SRAP). While several groups reported on SRA-RNA mechanism of action, SRAP exact function remains to be elucidated, mainly due to a lack of studies investigating the function of the protein independently of its RNA counterpart. Using two independent models to examine its specific functions, SRAP was found to enhance estrogen receptor alpha activity in a ligand and response-element dependent manner. Our data therefore suggest that both transcript and protein products of the SRA1 gene co-modulate the transcriptional activity of steroid receptors.

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New measures for estimating surface complementarity and packing at protein-protein interfaces.

Publication Date: 2010 Feb 12 PMID: 20153323
Authors: Mitra, P. - Pal, D.
Journal: FEBS Lett

A number of methods exist that use different approaches to assess geometric properties like the surface complementarity and atom packing at the protein-protein interface. We have developed two new and conceptually different measures using the Delaunay tessellation and interface slice selection to compute the surface complementarity and atom packing at the protein-protein interface in a straightforward manner. Our measures show a strong correlation among themselves and with other existing measures, and can be calculated in a highly time-efficient manner. The measures are discriminative for evaluating biological, as well as non-biological protein-protein contacts, especially from large protein complexes and large-scale structural studies (http://pallab.serc.iisc.ernet.in/nip_nsc).

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Novel splice variant of mouse insulin2 mRNA: Implications for insulin expression.

Publication Date: 2010 Feb 12 PMID: 20153322
Authors: Panda, A. C. - Kulkarni, S. D. - Muralidharan, B. - Bakthavachalu, B. - Seshadri, V.
Journal: FEBS Lett

Insulin is a secreted peptide that controls glucose homeostasis in mammals, and insulin biosynthesis is regulated by glucose at many levels. Rodent insulin is encoded by two non-allelic genes. We have identified a novel splice variant of the insulin2 gene in mice that constitutes about 75% of total insulin2 mRNA. The alternate splicing does not alter the ORF but reduces the 5'UTR by 12 bases. A reporter gene containing the novel short 5'UTR, is more efficiently expressed in cells, suggesting that alternative splicing of insulin mRNA in mice could result in an additional level of regulation in insulin biosynthesis.

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The trypanosome Pumilio-domain protein PUF7 associates with a nuclear cyclophilin and is involved in ribosomal RNA maturation.

Publication Date: 2010 Feb 12 PMID: 20153321
Authors: Droll, D. - Archer, S. - Fenn, K. - Delhi, P. - Matthews, K. - Clayton, C.
Journal: FEBS Lett

Proteins with Pumilio RNA binding domains (Puf proteins) are ubiquitous in eukaryotes. Some Puf proteins bind to the 3'-untranslated regions of mRNAs, acting to repress translation and promote degradation; others are involved in ribosomal RNA maturation. The genome of Trypanosoma brucei encodes eleven Puf proteins whose function cannot be predicted by sequence analysis. We show here that epitope-tagged TbPUF7 is located in the nucleolus, and associated with a nuclear cyclophilin-like protein, TbNCP1. RNAi targeting PUF7 reduced trypanosome growth and inhibited two steps in ribosomal RNA processing.

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Positive contribution of the IRE1alpha-XBP1 pathway to placental expression of CEA family genes.

Publication Date: 2010 Mar 5 PMID: 20146926
Authors: Oikawa, D. - Akai, R. - Iwawaki, T.
Journal: FEBS Lett

Inositol requiring enzyme-1alpha (IRE1alpha) is an ER-located transmembrane RNase whose activation leads to the production of the transcription factor X-box binding protein 1 (XBP1). Recently, we showed that the IRE1alpha-XBP1 pathway plays an essential role in the placenta. However, details of its function remain unclear. To address this point, we searched for IRE1alpha- or XBP1-regulated genes in the placenta, and identified the CEA family as a novel target of the IRE1alpha-XBP1 pathway. Moreover, PSG genes, which also belong to the CEA family, were up-regulated by XBP1. We have therefore identified a new aspect of the physiological function of the IRE1alpha-XBP1 pathway in the placenta.

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Vertebrate beta-thymosins: conserved synteny reveals the relationship between those of bony fish and of land vertebrates.

Publication Date: 2010 Mar 5 PMID: 20138884
Authors: Edwards, J.
Journal: FEBS Lett

Using conservation of synteny I show how the four thymosins expressed by teleost fish are related to the three of tetrapods, which is not evident from their protein sequences. This clarification was aided by identification of a novel thymosin of reptilians that replaces the beta10 thymosin of mammals. Recent reconstruction of the ancestral vertebrate genome suggests that divergence of beta-thymosins began with duplication preceding the two rounds of whole genome duplication.

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The SLO3 sperm-specific potassium channel plays a vital role in male fertility.

Publication Date: 2010 Mar 5 PMID: 20138882
Authors: Santi, C. M. - Martinez-Lopez, P. - de la Vega-Beltran, J. L. - Butler, A. - Alisio, A. - Darszon, A. - Salkoff, L.
Journal: FEBS Lett

Here we show a unique example of male infertility conferred by a gene knockout of the sperm-specific, pH-dependent SLO3 potassium channel. In striking contrast to wild-type sperm which undergo membrane hyperpolarization during capacitation, we found that SLO3 mutant sperm undergo membrane depolarization. Several defects in SLO3 mutant sperm are evident under capacitating conditions, including impaired motility, a bent "hairpin" shape, and failure to undergo the acrosome reaction (AR). The failure of AR is rescued by valinomycin which hyperpolarizes mutant sperm. Thus SLO3 is the principal potassium channel responsible for capacitation-induced hyperpolarization, and membrane hyperpolarization is crucial to the AR.

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Crystal structure of the LMAN1-CRD/MCFD2 transport receptor complex provides insight into combined deficiency of factor V and factor VIII.

Publication Date: 2010 Mar 5 PMID: 20138881
Authors: Wigren, E. - Bourhis, J. M. - Kursula, I. - Guy, J. E. - Lindqvist, Y.
Journal: FEBS Lett

LMAN1 is a glycoprotein receptor, mediating transfer from the ER to the ER-Golgi intermediate compartment. Together with the co-receptor MCFD2, it transports coagulation factors V and VIII. Mutations in LMAN1 and MCFD2 can cause combined deficiency of factors V and VIII (F5F8D). We present the crystal structure of the LMAN1/MCFD2 complex and relate it to patient mutations. Circular dichroism data show that the majority of the substitution mutations give rise to a disordered or severely destabilized MCFD2 protein. The few stable mutation variants are found in the binding surface of the complex leading to impaired LMAN1 binding and F5F8D.

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Generating artificial homologous proteins according to the representative family character in molecular mechanics properties--an attempt in validating an underlying rule of protein evolution.

Publication Date: 2010 Mar 5 PMID: 20138878
Authors: Liu, X. - Zhao, Y. P.
Journal: FEBS Lett

The molecular mechanics property is the foundation of many characters of proteins. Based on intramolecular hydrophobic force network, the representative family character underlying a protein's mechanics property is described by a simple two-letter scheme. The tendency of a sequence to become a member of a protein family is scored according to this mathematical representation. Remote homologs of the WW-domain family could be easily designed using such a mechanistic signature of protein homology. Experimental validation showed that nearly all artificial homologs have the representative folding and bioactivity of their assigned family. Since the molecular mechanics property is the only consideration in this study, the results indicate its possible role in the generation of new members of a protein family during evolution.

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Myeloid translocation gene 16b is a dual A-kinase anchoring protein that interacts selectively with plexins in a phospho-regulated manner.

Publication Date: 2010 Mar 5 PMID: 20138877
Authors: Fiedler, S. E. - Schillace, R. V. - Daniels, C. J. - Andrews, S. F. - Carr, D. W.
Journal: FEBS Lett

The myeloid translocation gene (MTG) homologue Nervy associates with PlexinA on the plasma membrane, where it functions as an A-kinase anchoring protein (AKAP) to modulate plexin-mediated semaphorin signaling in Drosophila. Mammalian MTG16b is an AKAP found in immune cells where plexin-mediated semaphorin signaling regulates immune responses. This study provides the first evidence that MTG16b is a dual AKAP capable of binding plexins. These interactions are selective (PlexinA1 and A3 bind MTG, while PlexinB1 does not) and can be regulated by PKA-phosphorylation. Collectively, these data suggest a possible mechanism for the targeting and integration of adenosine 3',5'-cyclic monophosphate (cAMP) and semaphorin signaling in immune cells.

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Ectopic recombination in the central and peripheral nervous system by aP2/FABP4-Cre mice: implications for metabolism research.

Publication Date: 2010 Mar 5 PMID: 20138876
Authors: Martens, K. - Bottelbergs, A. - Baes, M.
Journal: FEBS Lett

aP2-Cre mice have amply been used to generate conditional adipose selective inactivation of important signaling molecules. We show that the efficiency of Cre mediated recombination in adipocytes and adipose selectivity is not always guaranteed. In particular, Cre activity was found in ganglia of the peripheral nervous system (PNS), in adrenal medulla and in neurons throughout the central nervous system (CNS). Because these tissues have an important impact on adipose tissue, care should be taken when using aP2-Cre mice to define the role of the targeted genes in adipose tissue function.

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BS69 cooperates with TRAF3 in the regulation of Epstein-Barr virus-derived LMP1/CTAR1-induced NF-kappaB activation.

Publication Date: 2010 Mar 5 PMID: 20138174
Authors: Ikeda, O. - Miyasaka, Y. - Yoshida, R. - Mizushima, A. - Oritani, K. - Sekine, Y. - Kuroda, M. - Yasui, T. - Fujimuro, M. - Muromoto, R. - Nanbo, A. - Matsuda, T.
Journal: FEBS Lett

Epstein-Barr virus latent membrane protein 1 (LMP1) activates NF-kappaB signaling pathways through two C-terminal regions, CTAR1 and CTAR2. Previous studies have demonstrated that BS69, a multidomain cellular protein, regulates LMP1/CTAR2-mediated NF-kappaB activation by interfering with the complex formation between TRADD and LMP1/CTAR2. Here, we found that BS69 directly interacted with the LMP1/CTAR1 domain and regulated LMP1/CTAR1-mediated NF-kappaB activation and subsequent IL-6 production. Regarding the mechanisms involved, we found that BS69 directly interacted with TRAF3, a negative regulator of NF-kappaB activation. Furthermore, small-interfering RNA-mediated knockdown experiments revealed that TRAF3 was involved in the BS69-mediated suppression of LMP1/CTAR1-induced NF-kappaB activation.

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A novel role of microtubular cytoskeleton in the dynamics of caspase-dependent Fas/CD95 death receptor complexes during apoptosis.

Publication Date: 2010 Mar 5 PMID: 20138036
Authors: Doma, E. - Chakrabandhu, K. - Hueber, A. O.
Journal: FEBS Lett

The activation of cysteine-aspartic proteases or caspases and the dynamic arrangement of cytoskeletal components are crucial during apoptosis. Here we describe the fate of Fas downstream of the FasL-induced internalization step, including formation of caspase-dependent SDS-stable Fas complexes, which is mediated by cytoskeleton integrity. We show, in particular, that following FasL treatment, the Fas lower aggregate complex can be co-immunoprecipitated with tubulin and an active form of caspase-8 and that this interaction contributes to the propagation of FasL-induced cell death. The importance of cytoskeletal components during FasL-induced apoptosis is highlighted by our detection of a pool of microtubule-associated Fas complexes.

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Structure of translation initiation factor 1 from Mycobacterium tuberculosis and inferred binding to the 30S ribosomal subunit.

Publication Date: 2010 Mar 5 PMID: 20132820
Authors: Hatzopoulos, G. N. - Mueller-Dieckmann, J.
Journal: FEBS Lett

The crystal structure of the free form of IF1 from Mycobacterium tuberculosis has been determined at 1.47 A resolution. The structure adopts the expected OB fold and matches the high structural conservation among IF1 orthologues. In order to further explore the function of Mtb-IF1, we built a model of its interaction with the 30S ribosomal subunit based on the crystal structure of the complex from Thermus thermophilus. The model suggests that several functionally important side chain residues undergo large movements while the rest of the protein in complex shows only very limited conformational change as compared to its form in solution.

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The redox state of the plastoquinone pool directly modulates minimum chlorophyll fluorescence yield in Chlamydomonas reinhardtii.

Publication Date: 2010 Mar 5 PMID: 20122933
Authors: Hohmann-Marriott, M. F. - Takizawa, K. - Eaton-Rye, J. J. - Mets, L. - Minagawa, J.
Journal: FEBS Lett

The effect of the plastoquionone (PQ) pool oxidation state on minimum chlorophyll fluorescence was studied in the green alga Chlamydomonas reinhardtii. In wild type and a mutant strain that lacks both photosystems but retains light harvesting complexes, oxygen depletion induced a rise in minimum chlorophyll fluorescence. An increase in minimum fluorescence yield is also observed when the PQ pool becomes reduced in the presence of oxygen and after application of an ionophore that collapses the transmembrane proton gradient. Together these results indicate that minimum chlorophyll fluorescence is modulated by the PQ oxidation state.

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The conserved Cys76 plays a crucial role for the conformation of reduced glutathione peroxidase-type tryparedoxin peroxidase.

Publication Date: 2010 Mar 5 PMID: 20122932
Authors: Muhle-Goll, C. - Fuller, F. - Ulrich, A. S. - Krauth-Siegel, R. L.
Journal: FEBS Lett

The crystal structure of reduced tryparedoxin peroxidase shows Cys47 close to Gln82 and Trp137 and helix formation of residues 87 to 97 whereas the NMR structure of the reduced C76S mutant adopts a different conformation similar to the oxidized protein. Circular dichroism (CD), fluorescence and NMR spectroscopy reveal that the fully active C76S mutant differs from the wildtype (WT) enzyme mainly in its reduced form both in secondary structure content and Trp137 environment. This implies that Cys76 plays a critical role for the reduced enzyme assuming different conformational states and that the catalytic triad may only be necessary as short-lived intermediate during catalysis.

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Involvement of protein kinase Cdelta in induction of apoptosis by cationic liposomes in macrophage-like RAW264.7 cells.

Publication Date: 2010 Mar 5 PMID: 20122929
Authors: Arisaka, M. - Nakamura, T. - Yamada, A. - Negishi, Y. - Aramaki, Y.
Journal: FEBS Lett

We have recently demonstrated that reactive oxygen species (ROS) play an important role in RAW264.7 cell apoptosis induced by cationic liposomes composed of stearylamine (SA-liposomes). In this study, we investigated whether protein kinase Cdelta PKCdelta) is involved in apoptosis induced by cationic liposomes. Tyrosine phosphorylation, nuclear localization, and cleavage of PKCdelta were observed following the treatment of cells with SA-liposomes, suggesting that SA-liposomes activate PKCdelta. Rottlerin, a specific inhibitor of PKCdelta, inhibited ROS generation and also suppressed apoptosis. Cell surface proteoglycans may contribute to PKCdelta activation by SA-liposomes. These findings suggest that PKCdelta is strongly associated with apoptosis induced by SA-liposomes.

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JNK-ATF-2 inhibits thrombomodulin (TM) expression by recruiting histone deacetylase4 (HDAC4) and forming a transcriptional repression complex in the TM promoter.

Publication Date: 2010 Mar 5 PMID: 20116378
Authors: Rong, Y. - Zhang, M. - Zhang, L. - Wang, X. L. - Shen, Y. H.
Journal: FEBS Lett

Thrombomodulin (TM) is an important vascular protective molecule that has anticoagulant, anti-inflammatory and anti-apoptotic properties. TM is downregulated in many thrombotic and vascular diseases. However, the mechanisms responsible for TM suppression are not completely understood. In this study, we investigated the mechanism involved in fatty acid-induced suppression of TM expression in human aortic endothelial cells. We found that palmitic acid inhibited TM expression through the JNK and p38 pathways. ATF-2, a JNK and p38 target transcription factor, was involved in the suppression. ATF-2 can bind to the TM promoter, recruit HDAC4 and form a transcriptional repression complex in the promoter, which may lead to chromatin condensation and transcriptional arrest. This study provides novel insight into TM down-regulation by stress signaling pathways.

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Tumor suppressor activity of KLF6 mediated by downregulation of the PTTG1 oncogene.

Publication Date: 2010 Mar 5 PMID: 20116377
Authors: Lee, U. E. - Ghiassi-Nejad, Z. - Paris, A. J. - Yea, S. - Narla, G. - Walsh, M. - Friedman, S. L.
Journal: FEBS Lett

The tumor suppressor Kruppel-like factor 6 (KLF6) is frequently inactivated in hepatocellular carcinoma (HCC). To unearth downstream transcriptional targets of KLF6, cDNA microarray analysis of whole liver was compared between KLF6+/+ and KLF6+/- mice. Pituitary tumor transforming gene 1 (PTTG1), an oncogene, was the most up-regulated transcript in KLF6+/- liver. In human HCCs, KLF6 mRNA was significantly decreased, associated with increased PTTG1. In HepG2, KLF6 transcriptionally repressed PTTG1 by direct promoter interaction. Whereas KLF6 downregulation by siRNA increased HepG2 proliferation, siRNA to PTTG1 was anti-proliferative. PTTG1 downregulation represents a novel tumor suppressor pathway of KLF6.

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CBFA2T3-ZNF651, like CBFA2T3-ZNF652, functions as a transcriptional corepressor complex.

Publication Date: 2010 Mar 5 PMID: 20116376
Authors: Kumar, R. - Cheney, K. M. - Neilsen, P. M. - Schulz, R. B. - Callen, D. F.
Journal: FEBS Lett

A significant proportion of the human genome codes for transcription factors. Balanced activity of transcriptional activators and repressors is essential for normal development and differentiation. Previously we reported that a classical C2H2 zinc finger DNA binding protein ZNF652 functionally interacts with CBFA2T3 to repress transcription of genes containing ZNF652 consensus DNA binding sequence within the promoters of these target genes. Here we show that ZNF651 is a ZNF652 paralogue that shares a common DNA binding sequence with ZNF652 and represses target gene expression through the formation of a CBFA2T3-ZNF651 corepressor complex. It is suggested that CBFA2T3-ZNF651 and CBFA2T3-ZNF652 repressor complexes perform functionally similar roles in a tissue-specific manner.

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Dynamin-1 co-associates with native mouse brain BKCa channels: proteomics analysis of synaptic protein complexes.

Publication Date: 2010 Mar 5 PMID: 20114047
Authors: Gorini, G. - Ponomareva, O. - Shores, K. S. - Person, M. D. - Harris, R. A. - Mayfield, R. D.
Journal: FEBS Lett

In every synapse, a large number of proteins interact with other proteins in order to carry out signaling and transmission in the central nervous system. In this study, we used interaction proteomics to identify novel synaptic protein interactions in mouse cortical membranes under native conditions. Using immunoprecipitation, immunoblotting, and mass spectrometry, we identified a number of novel synaptic protein interactions involving soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), calcium-activated potassium channel (BKCa) alpha subunits, and dynamin-1. These novel interactions offer valuable insight into the protein-protein interaction network in intact synapses that could advance understanding of vesicle trafficking, release, and recycling.

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Intrahepatic cholesterol influences progression, inhibition and reversal of non-alcoholic steatohepatitis in hyperlipidemic mice.

Publication Date: 2010 Mar 5 PMID: 20114046
Authors: Wouters, K. - van Bilsen, M. - van Gorp, P. J. - Bieghs, V. - Lutjohann, D. - Kerksiek, A. - Staels, B. - Hofker, M. H. - Shiri-Sverdlov, R.
Journal: FEBS Lett

Hepatic inflammation is the key factor in non-alcoholic steatohepatitis (NASH) and promotes progression to liver damage. We recently identified dietary cholesterol as the cause of hepatic inflammation in hyperlipidemic mice. We now show that hepatic transcriptome responses are strongly dependent on cholesterol metabolism during diet-induced NASH and its inhibition by fenofibrate. Furthermore, we show that, despite doubling hepatic steatosis, pharmacological LXR activation reverses hepatic inflammation, in parallel with reversing hepatic cholesterol levels. Together, the results indicate a prominent role of cholesterol during the development, inhibition and reversal of hepatic inflammation in NASH and reveal potential new therapeutic strategies against NASH.

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Akt isoforms regulate intermediate filament protein levels in epithelial carcinoma cells.

Publication Date: 2010 Mar 5 PMID: 20109457
Authors: Fortier, A. M. - Van Themsche, C. - Asselin, E. - Cadrin, M.
Journal: FEBS Lett

Keratin 8 and 18 are simple epithelial intermediate filament (IF) proteins, whose expression is differentiation- and tissue-specific, and is maintained during tumorigenesis. Vimentin IF is often co-expressed with keratins in cancer cells. Recently, IF have been proposed to be involved in signaling pathways regulating cell growth, death and motility. The PI3K/Akt pathway plays a pivotal role in these processes. Thus, we investigated the role of Akt (1 and 2) in regulating IF expression in different epithelial cancer cell lines. Over-expression of Akt1 increases K8/18 proteins. Akt2 up-regulates K18 and vimentin expression by an increased mRNA stability. To our knowledge, these results represent the first indication that Akt isoforms regulate IF expression and support the hypothesis that IFs are involved in PI3K/Akt pathway.

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The regulatory factor SipA is a highly stable beta-II class protein with a SH3 fold.

Publication Date: 2010 Mar 5 PMID: 20102713
Authors: Lopez-Redondo, M. L. - Contreras, A. - Marina, A. - Neira, J. L.
Journal: FEBS Lett

The small regulator SipA, interacts with the ATP-binding domain of non-bleaching sensor histidine kinase (NblS), the most conserved histidine kinase in cyanobacteria. NblS regulates photosynthesis and acclimation to a variety of environmental conditions. We show here that SipA is a highly stable protein in a wide pH range, with a thermal denaturation midpoint of 345 K. Circular dichroism and 1D 1H NMR spectroscopies, as well as modelling, suggest that SipA is a beta-II class protein, with short strands followed by turns and long random-coil polypeptide patches, matching the SH3 fold. The experimentally determined m-value and the heat capacity change upon thermal unfolding (DeltaCp) closely agreed with the corresponding theoretical values predicted from the structural model, further supporting its accuracy.

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Stopped-flow studies of the reaction of D-tartronate semialdehyde-2-phosphate with human neuronal enolase and yeast enolase 1.

Publication Date: 2010 Mar 5 PMID: 20102712
Authors: Brewer, J. M. - McKinnon, J. S. - Phillips, R. S.
Journal: FEBS Lett

We determined the kinetics of the reaction of human neuronal enolase and yeast enolase 1 with the slowly-reacting chromophoric substrate D-tartronate semialdehyde phosphate (TSP), each in tris (tris (hydroxymethyl) aminomethane) and another buffer at several Mg2+ concentrations, 50 or 100 microM, 1 mM and 30 mM. All data were biphasic, and could be satisfactorily fit, assuming either two successive first-order reactions or two independent first-order reactions. Higher Mg2+ concentrations reduce the relative magnitude of the slower reaction. The results are interpreted in terms of a catalytically significant interaction between the two subunits of these enzymes.

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X-ray structures of the peridinin-chlorophyll-protein reconstituted with different chlorophylls.

Publication Date: 2010 Mar 5 PMID: 20102711
Authors: Schulte, T. - Hiller, R. G. - Hofmann, E.
Journal: FEBS Lett

The peridinin-chlorophyll a-protein (PCP) from dinoflagellates is a soluble light harvesting antenna which gathers incoming photons mainly by the carotenoid peridinin. In PCPs reconstituted with different chlorophylls, the peridinin to chlorophyll energy transfer rates are well predicted by a Forster-like theory, but only if the pigment arrangements are identical in all PCPs. We have determined the X-ray structures of PCPs reconstituted with Chlorophyll-b (Chl-b), Chlorophyll-d (Chl-d) and Bacteriochlorophyll-a (BChl-a) to resolutions
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C1qTNF-related protein-6 mediates fatty acid oxidation via the activation of the AMP-activated protein kinase.

Publication Date: 2010 Mar 5 PMID: 20102710
Authors: Lee, W. - Kim, M. J. - Park, E. J. - Choi, Y. J. - Park, S. Y.
Journal: FEBS Lett

C1qTNF-related proteins (CTRPs) are involved in diverse processes including metabolism, inflammation host defense, apoptosis, cell differentiation, autoimmunity, hibernation, and organogenesis. However, the physiological role of CTRP6 remains poorly understood. Here we demonstrate that the globular domain of CTRP6 mediates the phosphorylation and activation of the 5'-AMP-activated protein kinase (AMPK) in skeletal muscle cells. In parallel with the activation of AMPK, CTRP6 induces the phosphorylation of acetyl coenzyme A carboxylase (ACC) and fatty acid oxidation in myocytes. Thus, CTRP6 plays a role in fatty acid metabolism via the AMPK-ACC pathway.

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NOX3-derived reactive oxygen species promote TNF-alpha-induced reductions in hepatocyte glycogen levels via a JNK pathway.

Publication Date: 2010 Mar 5 PMID: 20102709
Authors: Li, L. - He, Q. - Huang, X. - Man, Y. - Zhou, Y. - Wang, S. - Wang, J. - Li, J.
Journal: FEBS Lett

TNF-alpha-induced insulin resistance is associated with generation of reactive oxygen species (ROS). This study aims at defining the link between ROS production and hepatic insulin resistance. Treatment with TNF-alpha increased ROS generation through activating NADPH oxidase 3 (NOX3) in HepG2 hepatocytes. Down-regulation of NOX3 using siRNA prevented TNF-alpha-induced decrease of cellular glycogen. In the cells treated with TNF-alpha, there were NOX3-dependent activation of JNK, inhibition of IRS1 and phosphorylation of AKT/PKB and GSK. In conclusion, the effects of TNF-alpha on hepatic insulin resistance appear to be, at least in part, mediated by NOX3-derived ROS through a JNK pathway.

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MiRNA-26b regulates the expression of cyclooxygenase-2 in desferrioxamine-treated CNE cells.

Publication Date: 2010 Mar 5 PMID: 20100477
Authors: Ji, Y. - He, Y. - Liu, L. - Zhong, X.
Journal: FEBS Lett

Here we report that miR-26b is involved in COX-2 overexpression in desferrioxamine (DFOM)-treated carcinoma of nasopharyngeal epithelial (CNE) cells. The level of miR-26b in DFOM-treated CNE cells is inversely proportional to the expression level of the COX-2 protein. Overexpression of miR-26b in DFOM-treated CNE cells inhibits cell proliferation. A luciferase reporter gene experiment suggests that the 3' untranslated region of COX-2 carries a binding site for miR-26b. Overexpression of miR-26b marginally reduces the levels of COX-2 protein in DFOM-treated CNE cells. Moreover, knockdown of COX-2 expression had a similar effect to overexpression of miR-26b. Taken together, these results suggest that miR-26b regulates COX-2 expression in DFOM-treated cells.

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Evaluating bistability of Bax activation switch.

Publication Date: 2010 Mar 5 PMID: 20096692
Authors: Sun, T. - Lin, X. - Wei, Y. - Xu, Y. - Shen, P.
Journal: FEBS Lett

Mitochondrial apoptotic pathway is precisely controlled by BCL-2 family. Complex interactions of BCL-2 family proteins constitute a bistable switch of which detailed experimental and theoretical delineation remains elusive. In this paper, combined approaches were used to explore the bistability of Bax activation switch. We found that Bax activation is indeed in an 'all-or-none' manner. The 'variable-delay, snap-action' nature for Bax activation is further explored theoretically. We suggest that bistability is largely attributed to topological structure and shows considerable robustness. Therefore, our study characterizes dynamics and sensitivities in intrinsic apoptotic pathway.

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The C-terminal residues of the 2b protein of Cucumber mosaic virus are important for efficient expression in Escherichia coli and DNA-binding.

Publication Date: 2010 Mar 5 PMID: 20096691
Authors: Sueda, K. - Shimura, H. - Meguro, A. - Uchida, T. - Inaba, J. - Masuta, C.
Journal: FEBS Lett

The RNA silencing suppressor 2b protein of Cucumber mosaic virus (CMV) is difficult to produce in Escherichia coli. We compared two CMV 2b proteins that differ in their toxicity against E. coli and found that the acidic amino acid residues in the C-terminal significantly affected the toxicity and expression level of the protein in E. coli. In addition, in a DNA-binding assay, 2b had the ability to bind to DNA, and this ability was affected by the charge on the C-terminal residues of 2b. We concluded that the C-terminal residues were important for 2b's DNA-binding ability, which may partly explain the toxicity of the protein.

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Comments on the rank product method for analyzing replicated experiments.

Publication Date: 2010 Mar 5 PMID: 20093118
Authors: Koziol, J. A.
Journal: FEBS Lett

Breitling et al. introduced a statistical technique, the rank product method, for detecting differentially regulated genes in replicated microarray experiments. The technique has achieved widespread acceptance and is now used more broadly, in such diverse fields as RNAi analysis, proteomics, and machine learning. In this note, we relate the rank product method to linear rank statistics and provide an alternative derivation of distribution theory attending the rank product method.

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Regulation of HOXA2 gene expression by the ATP-dependent chromatin remodeling enzyme CHD8.

Publication Date: 2010 Feb 19 PMID: 20085832
Authors: Yates, J. A. - Menon, T. - Thompson, B. A. - Bochar, D. A.
Journal: FEBS Lett

Chromodomain, helicase, DNA-binding protein 8 (CHD8) is an ATP-dependent chromatin remodeling enzyme that has been demonstrated to exist within a large protein complex which includes WDR5, Ash2L, and RbBP5, members of the Mixed Lineage Leukemia (MLL) histone modifying complexes. Here we show that CHD8 relocalizes to the promoter of the MLL regulated gene HOXA2 upon gene activation. Depletion of CHD8 enhances HOXA2 expression under activating conditions. Furthermore, depletion of CHD8 results in a loss of the WDR5/Ash2L/RbBP5 subcomplex, and consequently H3K4 trimethylation, at the HOXA2 promoter. These studies suggest that CHD8 alters HOXA2 gene expression and regulates the recruitment of chromatin modifying enzymes.

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Characterization of hydrogen peroxide production by Duox in bronchial epithelial cells exposed to Pseudomonas aeruginosa.

Publication Date: 2010 Mar 5 PMID: 20085766
Authors: Rada, B. - Leto, T. L.
Journal: FEBS Lett

Hydrogen peroxide production by the NADPH oxidase Duox1 occurs during activation of respiratory epithelial cells stimulated by purified bacterial ligands, such as lipopolysaccharide. Here, we characterize Duox activation using intact bacterial cells of several airway pathogens. We found that only Pseudomonas aeruginosa, not Burkholderia cepacia or Staphylococcus aureus, triggers H2O2 production in bronchial epithelial cells in a calcium-dependent but predominantly ATP-independent manner. Moreover, by comparing mutant Pseudomonas strains, we identify several virulence factors that participate in Duox activation, including the type-three secretion system. These data provide insight on Duox activation by mechanisms unique to P. aeruginosa.

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Noxa is necessary for hydrogen peroxide-induced caspase-dependent cell death.

Publication Date: 2010 Feb 19 PMID: 20085765
Authors: Aikawa, T. - Shinzawa, K. - Tanaka, N. - Tsujimoto, Y.
Journal: FEBS Lett

Oxidative stress induces apoptosis or necrosis of many cell types, which can cause tissue injury. Hydrogen peroxide (H(2)O(2)) induced apoptotic death of Jurkat cells. This effect was inhibited by overexpression of human Bcl-2, by silencing of cytochrome c, and by ablation of Bax/Bak, indicating that H(2)O(2)-induced apoptosis was mediated by the mitochondrial pathway in Jurkat cells. Treatment with H(2)O(2) caused an increase of Noxa protein, via activating transcription factor 4-dependent accumulation of Noxa mRNA and inhibition of Noxa protein degradation. H(2)O(2)-induced apoptosis was strongly suppressed by silencing of Noxa, indicating that Noxa plays a crucial role in this form of apoptosis.

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Stoichiometric protein complex formation and over-expression using the prokaryotic native operon structure.

Publication Date: 2010 Feb 19 PMID: 20085764
Authors: Poulsen, C. - Holton, S. - Geerlof, A. - Wilmanns, M. - Song, Y. H.
Journal: FEBS Lett

In prokaryotes, operon encoded proteins often form protein-protein complexes. Here, we show that the native structure of operons can be used to efficiently overexpress protein complexes. This study focuses on operons from mycobacteria and the use of Mycobacterium smegmatis as an expression host. We demonstrate robust and correct stoichiometric expression of dimers to higher oligomers. The expression efficacy was found to be largely independent of the intergenic distances. The strategy was successfully extended to express mycobacterial protein complexes in Escherichia coli, showing that the operon structure of gram-positive bacteria is also functional in gram-negative bacteria. The presented strategy could become a general tool for the expression of large quantities of pure prokaryotic protein complexes for biochemical and structural studies.

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The N-terminal domain of human holocarboxylase synthetase facilitates biotinylation via direct interaction with the substrate protein.

Publication Date: 2010 Feb 19 PMID: 20085763
Authors: Lee, C. K. - Cheong, C. - Jeon, Y. H.
Journal: FEBS Lett

Human holocarboxylase synthetase shows a high degree of sequence homology in the catalytic domain with bacterial biotin ligases such as Escherichia coli BirA, but differs in the length and sequence of the N-terminus. Despite several studies having been undertaken on the N-terminal region of hHCS, the role of this region remains unclear. We determined the structure of the N-terminal domain of hHCS by limited proteolysis and showed that this domain has a crucial effect on the enzymatic activity. The domain interacts not only with biotin acceptor protein, but also with the catalytic domain of hHCS, as shown by nuclear magnetic resonance (NMR) experiments. We propose that the N-terminal domain of hHCS recognizes the charged region of biotin acceptor protein, distinctly from the recognition by the catalytic domain.

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Nucleotide utilization requirements that render ClpB active as a chaperone.

Publication Date: 2010 Mar 5 PMID: 20085762
Authors: del Castillo, U. - Fernandez-Higuero, J. A. - Perez-Acebron, S. - Moro, F. - Muga, A.
Journal: FEBS Lett

ClpB is a member of the AAA+ superfamily that forms a ring-shaped homohexamer. Each protomer contains two nucleotide binding domains arranged in two rings that hydrolyze ATP. We extend here previous studies on ClpB nucleotide utilization requirements by using an experimental approach that maximizes random incorporation of different subunits into the protein hexamer. Incorporation of one subunit unable to bind or hydrolyze ATP knocks down the chaperone activity, while the wt hexamer can accommodate two mutant subunits that hydrolyze ATP in only one protein ring. Four subunits seem to build the functional cooperative unit, provided that one of the protein rings contains active nucleotide binding sites.

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Nrf3-deficient mice are not protected against acute lung and adipose tissue damages induced by butylated hydroxytoluene.

Publication Date: 2010 Mar 5 PMID: 20085761
Authors: Chevillard, G. - Nouhi, Z. - Anna, D. - Paquet, M. - Blank, V.
Journal: FEBS Lett

We found that both wild type and Nrf3 (NF-E2-related factor 3) deficient mice are sensitive to BHT single administration exhibiting respiratory distress and considerably lose body weight following treatment. At time of sacrifice, the BHT-treated Nrf3-/- mice had lost significantly more body weight than their WT counterparts. In the lung, transcript levels of the transcription factors Nrf1, Nrf2 and Nrf3 were differentially regulated by BHT treatment. In addition, genes implicated in adipogenesis were repressed following BHT exposure in the white adipose tissue. Together, our data provide the first evidence that BHT exposure not only affects lung function but also leads to impaired adipogenesis in adipocytes.

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Characterization of DNA-Hv1 histone interactions; discrimination of DNA size and shape.

Publication Date: 2010 Mar 5 PMID: 20085758
Authors: Papadakis, G. - Tsortos, A. - Mitsakakis, K. - Gizeli, E.
Journal: FEBS Lett

We have studied the formation of histone Hv1-DNA complexes using an acoustic biosensor and AFM imaging. Our results show that DNA and histone molecules aggregate into amorphous accumulations which form a compact rigid layer on the sensor's surface. By measuring changes in the acoustic wave amplitude, it was possible to titrate surface bound DNA with Hv1 and discriminate between DNA molecules of different size and shape. From the kinetic analysis of real time data, Keq was found equal to 3x10(5) M(-1).

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Identification of a novel splicing isoform of murine CGI-58.

Publication Date: 2010 Mar 5 PMID: 20083112
Authors: Yang, X. - Lu, X. - Liu, J.
Journal: FEBS Lett

The comparative gene identification-58 (CGI-58) gene, mutations of which are linked to Chanarin-Dorfman syndrome, encodes a protein of the alpha/beta hydrolase domain subfamily. We report here a new alternative splicing isoform of the murine CGI-58 gene, termed mCGI-58S. Sequence comparison indicates the lack of second and third exons in this cDNA variant. While the full-length protein displayed perilipin-dependent localization to lipid droplets, mCGI-58S showed a predominant cytoplasmic staining when expressed in cells. mCGI-58S was incapable of activating adipose triglyceride lipase but retained the capacity to acylate lysophosphatidic acid. Overexpression of mCGI-58S failed to promote lipid droplet turnover and loss of intracellular triacylglycerols. These results suggest that this splicing event may be involved in the regulation of lipid homeostasis.

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Salmonella regulation of intestinal stem cells through the Wnt/beta-catenin pathway.

Publication Date: 2010 Mar 5 PMID: 20083111
Authors: Liu, X. - Lu, R. - Wu, S. - Sun, J.
Journal: FEBS Lett

Recent studies have revealed that bacteria target stem cells for long-term survival in a Drosophila model. However, in mammalian models, little is known about bacterial infection and intestinal stem cells. Our study aims at understanding bacterial regulation of the intestinal stem cell in a Salmonella colitis mouse model. We found that Salmonella activates the Wnt/beta-catenin signaling pathway that is known to regulate stem cells. We identified Salmonella protein AvrA that modulates Wnt signaling including upregulating Wnt expression, modifying beta-catenin, increasing total beta-catenin expression, and activating Wnt/beta-catenin transcriptional activity in the intestinal epithelial cells. The numbers of stem cells and proliferative cells increased in the intestine infected with Salmonella expressing AvrA. Our study provides insights into bacterial infection and stem cell maintenance.

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ATP-triggered ADP release from the asymmetric chaperonin GroEL/GroES/ADP7 is not the rate-limiting step of the GroEL/GroES reaction cycle.

Publication Date: 2010 Mar 5 PMID: 20083109
Authors: Tyagi, N. K. - Fenton, W. A. - Horwich, A. L.
Journal: FEBS Lett

The GroEL/GroES protein folding chamber is formed and dissociated by ATP binding and hydrolysis. ATP hydrolysis in the GroES-bound (cis) ring gates entry of ATP into the opposite unoccupied trans ring, which allosterically ejects cis ligands. While earlier studies suggested that hydrolysis of cis ATP is the rate-limiting step of the cycle (t1/2 approximately 10 s), a recent study suggested that ADP release from the cis ring may be rate-limiting (t1/2 approximately 15-20 s). Here we have measured ADP release using a coupled enzyme assay and observed a t1/2 for release of
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Use of a redox-sensing GFP (c-roGFP1) for real-time monitoring of cytosol redox status in Arabidopsis thaliana water-stressed plants.

Publication Date: 2010 Mar 5 PMID: 20079738
Authors: Jubany-Mari, T. - Alegre-Batlle, L. - Jiang, K. - Feldman, L. J.
Journal: FEBS Lett

Using Arabidopsis plants transformed with a redox-sensing green fluorescent protein targeted to the cytosol (c-roGFP1), we have demonstrated, in real time, measurements of reversible changes of redox status in the cytosol of plants subjected to a gradual water-stress, followed by re-watering. Plants sensed water stress, and changed the redox potential of their cytosol to a more oxidized value after a gradually-imposed water stress. Small variations in the cytosol redox potential and ascorbate (AA) values suggest that this parameter was tightly regulated. The re-watering was paralleled by a return of water stress, redox potential and ascorbate to initial values, showing the reversibility of water stress and its consequences.

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Influence of the hepatitis C virus 3'-untranslated region on IRES-dependent and cap-dependent translation initiation.

Publication Date: 2010 Feb 19 PMID: 20079737
Authors: Bung, C. - Bochkaeva, Z. - Terenin, I. - Zinovkin, R. - Shatsky, I. N. - Niepmann, M.
Journal: FEBS Lett

Translation of hepatitis C virus (HCV) genomic RNA is directed by an internal ribosome entry site (IRES) in the 5'-untranslated region (5'-UTR), and the HCV 3'-UTR enhances IRES activity. Since the HCV 3'-UTR has a unique structure among 3'-UTRs, we checked possible communication between the 5'- and the 3'-UTR of HCV during translation using chimeric reporter RNAs. We show that translation directed by the HCV IRES and by the HCV-like IRES of porcine teschovirus (PTV) which belongs to a quite distinct family of viruses (picornaviruses) or by the EMCV IRES is also enhanced by the HCV 3'-UTR or by a poly(A)-tail in different cell types.

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In vitro regulation of circadian phosphorylation rhythm of cyanobacterial clock protein KaiC by KaiA and KaiB.

Publication Date: 2010 Mar 5 PMID: 20079736
Authors: Nakajima, M. - Ito, H. - Kondo, T.
Journal: FEBS Lett

Biochemical circadian oscillation of KaiC phosphorylation, by mixing three Kai proteins and ATP, has been proven to be the central oscillator of the cyanobacterial circadian clock. In vivo, the intracellular levels of KaiB and KaiC oscillate in a circadian fashion. By scrutinizing KaiC phosphorylation rhythm in a wide range of Kai protein concentrations, KaiA and KaiB were found to be "parameter-tuning" and "state-switching" regulators of KaiC phosphorylation rhythm, respectively. Our results also suggest a possible entrainment mechanism of the cellular circadian clock with the circadian variation of intracellular levels of Kai proteins.

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The ND2 subunit is labeled by a photoaffinity analogue of asimicin, a potent complex I inhibitor.

Publication Date: 2010 Mar 5 PMID: 20074573
Authors: Nakamaru-Ogiso, E. - Han, H. - Matsuno-Yagi, A. - Keinan, E. - Sinha, S. C. - Yagi, T. - Ohnishi, T.
Journal: FEBS Lett

NADH:ubiquinone oxidoreductase (complex I) is the entry enzyme of mitochondrial oxidative phosphorylation. To obtain the structural information on inhibitor/quinone binding sites, we synthesized [3H]benzophenone-asimicin ([3H]BPA), a photoaffinity analogue of asimicin, which belongs to the acetogenin family known as the most potent complex I inhibitor. We found that [3H]BPA was photo-crosslinked to ND2, ND1 and ND5 subunits, by the three dimensional separation (blue-native/doubled SDS-PAGE) of [3H]BPA-treated bovine heart submitochondrial particles. The cross-linking was blocked by rotenone. This is the first finding that ND2 was photo-crosslinked with a potent complex I inhibitor, suggesting its involvement in the inhibitor/quinone-binding.

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NMR characterization of the interactions between lyso-GM1 aqueous micelles and amyloid beta.

Publication Date: 2010 Feb 19 PMID: 20074569
Authors: Yagi-Utsumi, M. - Kameda, T. - Yamaguchi, Y. - Kato, K.
Journal: FEBS Lett

Gangliosides are targets for a variety of pathologically relevant proteins, including amyloid beta (Abeta), an important component implicated in Alzheimer's disease (AD). To provide a structural basis for this pathogenic interaction associated with AD, we conducted NMR analyses of the Abeta interactions with gangliosides using lyso-GM1 micelles as a model system. Our NMR data revealed that the sugar-lipid interface is primarily perturbed upon binding of Abeta to the micelles, underscoring the importance of the inner part of the ganglioside cluster for accommodating Abeta in comparison with the outer carbohydrate branches that provide microbial toxin- and virus-binding sites.

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High glucose down-regulates miR-29a to increase collagen IV production in HK-2 cells.

Publication Date: 2010 Feb 19 PMID: 20067797
Authors: Du, B. - Ma, L. M. - Huang, M. B. - Zhou, H. - Huang, H. L. - Shao, P. - Chen, Y. Q. - Qu, L. H.
Journal: FEBS Lett

Deposition of collagen IV in proximal tubule cells (PTCs) plays an important role during diabetic nephropathy, but the mechanism underlying excessive production of collagen IV remains poorly understood. In this study, we examined the miRNA profile of HK-2 cells and found that high glucose/TGF-beta1 induced significant down-regulation of miR-29a. We then showed that miR-29a negatively regulated collagen IV by directly targeting the 3'UTRs of col4a1 and col4a2. These results suggest that miR-29a acts as a repressor to fine-tune collagen expression and that the reduction of miR-29a caused by high glucose may increase the risk of excess collagen deposition in PTCs.

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Functional role of acetylcholine and the expression of cholinergic receptors and components in osteoblasts.

Publication Date: 2010 Feb 19 PMID: 20067796
Authors: Sato, T. - Abe, T. - Chida, D. - Nakamoto, N. - Hori, N. - Kokabu, S. - Sakata, Y. - Tomaru, Y. - Iwata, T. - Usui, M. - Aiko, K. - Yoda, T.
Journal: FEBS Lett

Recent studies have indicated that acetylcholine (ACh) plays a vital role in various tissues, while the role of ACh in bone metabolism remains unclear. Here we demonstrated that ACh induced cell proliferation and reduced alkaline phosphatase (ALP) activity via nicotinic (nAChRs) and muscarinic acetylcholine receptors (mAChRs) in osteoblasts. We detected mRNA expression of several nAChRs and mAChRs. Furthermore, we showed that cholinergic components were up-regulated and subunits/subtypes of acetylcholine receptors altered during osteoblast differentiation. To our knowledge, this is the first report demonstrating that osteoblasts express specific acetylcholine receptors and cholinergic components and that ACh plays a possible role in regulating the proliferation and differentiation of osteoblasts.

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Estrogen regulates the expression of N-methyl-D-aspartate (NMDA) receptor subunit epsilon 4 (Grin2d), that is essential for the normal sexual behavior in female mice.

Publication Date: 2010 Feb 19 PMID: 20067795
Authors: Ikeda, K. - Fukushima, T. - Ogura, H. - Tsukui, T. - Mishina, M. - Muramatsu, M. - Inoue, S.
Journal: FEBS Lett

Estrogen plays important roles in the reproductive behavior of animals. In the present study, we found that the Grin2d gene of mouse possessed half-sites of the estrogen-responsive element (ERE) in the 3'-untranslated region (UTR). Quantitative PCR analysis showed that the reduced Grin2d mRNA expression in the hypothalamus of the ovariectomized mice was restored by estrogen administration. Downregulation of Grin2d mRNA expression was also detected in the hypothalamus of estrogen receptor alpha-knockout female mice. Moreover, estrogen-induced lordosis response was decreased in Grin2d-knockout mice. These results suggest that estrogen regulates lordosis behavior through the regulation of Grin2d expression in the hypothalamus of female mice.

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Golgi apparatus casein kinase phosphorylates bioactive Ser-6 of bone morphogenetic protein 15 and growth and differentiation factor 9.

Publication Date: 2010 Feb 19 PMID: 20067794
Authors: Tibaldi, E. - Arrigoni, G. - Martinez, H. M. - Inagaki, K. - Shimasaki, S. - Pinna, L. A.
Journal: FEBS Lett

Bone morphogenetic protein-15 (BMP-15) and growth and differentiation factor-9 (GDF-9) are oocyte-secreted factors that play essential roles in human folliculogenesis and ovulation. Their bioactivity is tightly regulated through phosphorylation, likely to occur within the Golgi apparatus of the secretory pathway. Here we show that Golgi apparatus casein kinase (G-CK) catalyzes the phosphorylation of rhBMP-15 and rhGDF-9. rhBMP-15, in particular, is an excellent substrate for G-CK. In each protein a single residue is phosphorylated by G-CK, corresponding to the serine residue at the sixth position of the mature region of both rhBMP-15 and rhGDF-9, whose phosphorylation is required for biological activity.

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The role of protonation in protein fibrillation.

Publication Date: 2010 Feb 19 PMID: 20067793
Authors: Jeppesen, M. D. - Westh, P. - Otzen, D. E.
Journal: FEBS Lett

Many proteins fibrillate at low pH despite a high population of charged side chains. Therefore exchange of protons between the fibrillating peptide and its surroundings may play an important role in fibrillation. Here, we use isothermal titration calorimetry to measure exchange of protons between buffer and the peptide hormone glucagon during fibrillation. Glucagon absorbs or releases protons to an extent which allows it to attain a net charge of zero in the fibrillar state, both at acidic and basic pH. Similar results are obtained for lysozyme. This suggests that side chain pK(a) values change dramatically in the fibrillar state.

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Crystal structure of the PHF8 Jumonji domain, an Nepsilon-methyl lysine demethylase.

Publication Date: 2010 Feb 19 PMID: 20067792
Authors: Yue, W. W. - Hozjan, V. - Ge, W. - Loenarz, C. - Cooper, C. D. - Schofield, C. J. - Kavanagh, K. L. - Oppermann, U. - McDonough, M. A.
Journal: FEBS Lett

Crystallographic analysis of the catalytic domain of PHD finger protein 8 (PHF8), an N(epsilon)-methyl lysine histone demethylase associated with mental retardation and cleft lip/palate, reveals a double-stranded beta-helix fold with conserved Fe(II) and cosubstrate binding sites typical of the 2-oxoglutarate dependent oxygenases. The PHF8 active site is highly conserved with those of the FBXL10/11demethylases, which are also selective for the di-/mono-methylated lysine states, but differs from that of the JMJD2 demethylases which are selective for tri-/di-methylated states. The results rationalize the lack of activity for the clinically observed F279S PHF8 variant and they will help to identify inhibitors selective for specific N(epsilon)-methyl lysine demethylase subfamilies.

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Nonsense-mediated translational repression involves exon junction complex downstream of premature translation termination codon.

Publication Date: 2010 Feb 19 PMID: 20067791
Authors: Lee, H. C. - Oh, N. - Cho, H. - Choe, J. - Kim, Y. K.
Journal: FEBS Lett

Human transforming growth factor-beta receptor type 2 (TGFbetaR2) mRNA harboring a premature translation termination codon (PTC) generated by frameshift mutation is targeted for nonsense-mediated translational repression (NMTR), rather than nonsense-mediated mRNA decay (NMD). Here we show that exon junction complex (EJC) downstream of a PTC plays an inhibitory role in translation of TGFbetaR2 mRNA. Translational repression by core EJC components occurs after formation of 80S ribosome complex, which is demonstrated using different types of internal ribosome entry sites (IRESes). Our findings implicate EJCs or core EJC components as negative regulators of translation.

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A subunit of decaprenyl diphosphate synthase stabilizes octaprenyl diphosphate synthase in Escherichia coli by forming a high-molecular weight complex.

Publication Date: 2010 Feb 19 PMID: 20051244
Authors: Cui, T. Z. - Kaino, T. - Kawamukai, M.
Journal: FEBS Lett

The length of the isoprenoid-side chain in ubiquinone, an essential component of the electron transport chain, is defined by poly-prenyl diphosphate synthase, which comprises either homomers (e.g., IspB in Escherichia coli) or heteromers (e.g., decaprenyl diphosphate synthase (Dps1) and D-less polyprenyl diphosphate synthase (Dlp1) in Schizosaccharomyces pombe and in humans). We found that expression of either dlp1 or dps1 recovered the thermo-sensitive growth of an E. coli ispB(R321A) mutant and restored IspB activity and production of Coenzyme Q-8. IspB interacted with Dlp1 (or Dps1), forming a high-molecular weight complex that stabilized IspB, leading to full functionality.

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A novel class of bacterial translation factor RF3 mutations suggests specific structural domains for premature peptidyl-tRNA drop-off.

Publication Date: 2010 Feb 19 PMID: 20043913
Authors: Watanabe, Y. - Nakamura, Y. - Ito, K.
Journal: FEBS Lett

The bacterial translation factor RF3 promotes translation termination by recycling the tRNA-mimicking release factors, RF1 and RF2, after mature polypeptide release. RF3 also enhances the premature peptidyl-tRNA drop-off reaction in the presence of RRF and EF-G. Despite the recently resolved X-ray crystal structure of RF3, the molecular details of the bimodal functionality of RF3 remain obscure. In this report, we demonstrate a novel class of RF3 mutations specifically defective in the tRNA drop-off reaction. These mutations suggest differential molecular pathways closely related to the guanine nucleotide modes of RF3.

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Structural and functional evidence for a substrate exclusion mechanism in mammalian tolloid like-1 (TLL-1) proteinase.

Publication Date: 2010 Feb 19 PMID: 20043912
Authors: Berry, R. - Jowitt, T. A. - Garrigue-Antar, L. - Kadler, K. E. - Baldock, C.
Journal: FEBS Lett

Bone morphogenetic protein-1 (BMP-1)/tolloid proteinases are fundamental to regulating dorsal ventral patterning and extracellular matrix deposition. In mammals there are four proteinases, the splice variants BMP-1 and mammalian tolloid (mTLD), and tolloid like-1 and -2 (TLL-1/2). BMP-1 has the highest catalytic activity and lacks three non-catalytic domains. We demonstrate that TLL-1, which has intermediate activity, forms a calcium-ion dependent dimer with monomers stacked side-by-side. In contrast, truncated TLL-1 molecules having the same shorter structure as BMP-1 are monomers and have improved activity towards their substrate chordin. The increased activity exceeds not only that of full-length TLL-1 but also BMP-1.

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The glucagon receptor antagonist BI-32169 constitutes a new class of lasso peptides.

Publication Date: 2010 Feb 19 PMID: 20043911
Authors: Knappe, T. A. - Linne, U. - Xie, X. - Marahiel, M. A.
Journal: FEBS Lett

The glucagon receptor antagonist BI-32169, recently isolated from Streptomyces sp., was described as a bicyclic peptide, although its primary structure comprises conserved elements of class I and class II lasso peptides. Tandem mass spectrometric and nuclear magnetic resonance spectroscopic studies revealed that BI-32169 is a lasso-structured peptide constituting the new class III of lasso peptides. The determined lasso fold opens new avenues to improve the promising biological activity of BI-32169.

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RKIP inhibits NF-kappaB in cancer cells by regulating upstream signaling components of the IkappaB kinase complex.

Publication Date: 2010 Feb 19 PMID: 20043910
Authors: Tang, H. - Park, S. - Sun, S. C. - Trumbly, R. - Ren, G. - Tsung, E. - Yeung, K. C.
Journal: FEBS Lett

RKIP was first identified as an inhibitor of the Raf-MEK-ERK signaling pathway. RKIP was also found to play an important role in the NF-kappaB pathway. Genetic and biochemical studies demonstrated that RKIP functioned as a scaffold protein facilitating the phosphorylation of IkappaB by upstream kinases. However, contrary to what one would expect of a scaffold protein, our results show that RKIP has an overall inhibitory effect on the NF-kappaB transcriptional activities. Since NF-kappaB target gene expression is subject to negative regulation involving the optimal induction of negative regulators, our data support a hypothesis that RKIP inhibits NF-kappaB activity via the auto-regulatory feedback loop by rapidly inducing the expression and synthesis of inhibitors of NF-kappaB activation.

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Flavones suppress type I IL-4 receptor signaling by down-regulating the expression of common gamma chain.

Publication Date: 2010 Feb 19 PMID: 20040389
Authors: Yamashita, S. - Yamashita, T. - Yamada, K. - Tachibana, H.
Journal: FEBS Lett

Immunoglobulin E (IgE) production is induced by interleukin (IL)-4 signaling mediated by type I IL-4 receptor (IL-4R) in B cells. We found that flavones inhibited IL-4-induced epsilon germline transcription which is essential for IgE class switching, and the phosphorylation of signal transducer and activator of transcription 6, janus kinase 3, and IL-4Ralpha, whereas IL-4 signaling mediated through type II IL-4R was unaffected by flavones. Furthermore, flavones reduced the expression of common gamma chain, a characteristic constituent subunit of type I IL-4R, suggesting that flavones suppress type I IL-4R signaling.

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Roles of the intramolecular regions of FE65 in its trans-accumulation and in p53 stabilization in the nuclear matrix of osmotically stressed cells.

Publication Date: 2010 Feb 19 PMID: 20036665
Authors: Kawai, T. - Nakaya, T. - Suzuki, T.
Journal: FEBS Lett

The neural adaptor protein FE65 interacts with the amyloid beta-protein precursor (APP). In osmotically stressed cells, the membrane APP-tethered FE65 is released into the cytoplasm and translocates to the nuclear matrix, where it stabilizes p53 via a non-canonical pathway. In this study, we found that the second phosphotyrosine interaction domain (PI2) of FE65 mediated its trans-accumulation in the nuclear matrix of osmotically stressed cells. The carboxyl-terminal half of FE65, which contains the PI2 domain, failed to stabilize p53, suggesting that the amino-terminal half of the protein plays an important role in the stabilization of p53 in osmotically stressed cells.

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Photodynamic antimicrobial activity of avian eggshell pigments.

Publication Date: 2010 Feb 19 PMID: 20036664
Authors: Ishikawa, S. - Suzuki, K. - Fukuda, E. - Arihara, K. - Yamamoto, Y. - Mukai, T. - Itoh, M.
Journal: FEBS Lett

Pigmentation in avian eggshells appears to be associated with shell strength, temperature regulation, and camouflage. The pigments found in eggshells are mainly porphyrins, which have been utilized therapeutically as photosensitizers. Here, we examined the photoinactivation of gram-positive (Staphylococcus aureus, Bacillus cereus) and gram-negative bacteria (Escherichia coli, Salmonella enteritidis) by hen eggshells and their pigments. The results indicated that eggshells have a light-dependent antimicrobial activity against gram-positive, but not gram-negative, bacteria. Our results indicate the possibility that the natural pigments used therapeutically have evolved in nature as a defence system.

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Structure of the GTPase and GDI domains of FeoB, the ferrous iron transporter of Legionella pneumophila.

Publication Date: 2010 Feb 19 PMID: 20036663
Authors: Petermann, N. - Hansen, G. - Schmidt, C. L. - Hilgenfeld, R.
Journal: FEBS Lett

Prokaryotic pathogens have developed specialized mechanisms for efficient uptake of ferrous iron (Fe(2+)) from the host. In Legionella pneumophila, the causative agent of Legionnaires' disease, the transmembrane GTPase FeoB plays a key role in Fe(2+) acquisition and virulence. FeoB consists of a membrane-embedded core and an N-terminal, cytosolic region (NFeoB). Here, we report the crystal structure of NFeoB from L. pneumophila, revealing a monomeric protein comprising two separate domains with GTPase and guanine-nucleotide dissociation inhibitor (GDI) functions. The GDI domain displays a novel fold, whereas the overall structure of the GTPase domain resembles that of known G domains but is in the rarely observed nucleotide-free state.

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The PsbS protein controls the macro-organisation of photosystem II complexes in the grana membranes of higher plant chloroplasts.

Publication Date: 2010 Feb 19 PMID: 20035752
Authors: Kereiche, S. - Kiss, A. Z. - Kouril, R. - Boekema, E. J. - Horton, P.
Journal: FEBS Lett

The PsbS protein is a critical component in the regulation of non-photochemical quenching (NPQ) in higher plant photosynthesis. Electron microscopy and image analysis of grana membrane fragments from wild type and mutant Arabidopsis plants showed that the semi-crystalline domains of photosystem II supercomplexes were identical in the presence and absence of PsbS. However, the frequency of the domains containing crystalline arrays was increased in the absence of PsbS. Conversely, there was a complete absence of such arrays in the membranes of plants containing elevated amounts of this protein. It is proposed that PsbS controls the macro-organisation of the grana membrane, providing an explanation of its role in NPQ.

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Mechanical stimulation suppresses phosphorylation of eIF2alpha and PERK-mediated responses to stress to the endoplasmic reticulum.

Publication Date: 2010 Feb 19 PMID: 20034494
Authors: Hirasawa, H. - Jiang, C. - Zhang, P. - Yang, F. C. - Yokota, H.
Journal: FEBS Lett

Cellular perturbations such as stress to the endoplasmic reticulum induce an integrated stress response, which activates phosphorylation of eIF2alpha and leads to alleviation of cellular injury or apoptosis. This study investigated the role of mechanical stimulation in the regulation of eIF2alpha and cell death. Mechanical stimulation was applied to mouse ulnae, MC3T3 cells, and mesenchymal stem cells. The results demonstrate that mechanical stimulation reduces phosphorylation of eIF2alpha through inactivation of Perk. Furthermore, flow pre-treatment reduces thapsigargin-induced cell mortality through suppression of phosphorylation of Perk. However, H(2)O(2)-driven cell mortality, which is not mediated by Perk, is not suppressed by mechanical stimulation. Taken together, our observations suggest a pro-survival role of mechanical stimulation in Perk-mediated stress responses.

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Disulfide linkage in the coiled-coil domain of subunit H of A1AO ATP synthase from Methanocaldococcus jannaschii and the NMR structure of the C-terminal segment H(85-104).

Publication Date: 2010 Feb 19 PMID: 20026332
Authors: Gayen, S. - Gruber, G.
Journal: FEBS Lett

The C-terminal residues 98-104 are important for structure stability of subunit H of A(1)A(O) ATP synthases as well as its interaction with subunit A. Here we determined the structure of the segment H(85-104) of H from Methanocaldococcus jannaschii, showing a helix between residues Lys90 to Glu100 and flexible tails at both ends. The helix-helix arrangement in the C-terminus was investigated by exchange of hydrophobic residues to single cysteine in mutants of the entire subunit H (H(I93C), H(L96C) and H(L98C)). Together with the surface charge distribution of H(85-104), these results shine light into the A-H assembly of this enzyme.

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Divalent metal-dependent regulation of hepcidin expression by MTF-1.

Publication Date: 2010 Feb 19 PMID: 20026331
Authors: Balesaria, S. - Ramesh, B. - McArdle, H. - Bayele, H. K. - Srai, S. K.
Journal: FEBS Lett

Hepcidin is a small acute phase peptide that regulates iron absorption. It is induced by inflammation and infection, but is repressed by anaemia and hypoxia. Here we further reveal that hepcidin transcription also involves interactions between functional metal response elements (MREs) in its promoter, and the MRE-binding transcription factor-1. Analysis of hepcidin mRNA and protein levels in hepatoma cells suggests that its expression may be regulated by divalent metal ions, with zinc inducing maximal effects on hepcidin levels. These data suggest that this peptide may be a pleiotropic sensor of divalent metals, some of which are xenobiotic environmental toxins.

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Gentamicin inhibits HSP70-assisted protein folding by interfering with substrate recognition.

Publication Date: 2010 Feb 19 PMID: 20026329
Authors: Yamamoto, S. - Nakano, S. - Owari, K. - Fuziwara, K. - Ogawa, N. - Otaka, M. - Tamaki, K. - Watanabe, S. - Komatsuda, A. - Wakui, H. - Sawada, K. - Kubota, H. - Itoh, H.
Journal: FEBS Lett

We previously reported that gentamicin (GM) specifically binds to heat-shock protein with subunit molecular masses of 70 kDa (HSP70). In the present study, we have investigated the effects of GM binding on HSP70-assisted protein folding in vitro. The C-terminal, and not the N-terminal of HSP70 was found to bind to GM. GM significantly suppressed refolding of firefly luciferase in the presence of HSP70 and HSP40, although the ATPase activity of HSP70 was unaffected by GM. A surface plasmon resonance analysis revealed that GM specifically interferes with the binding of HSP70 to a model peptide that mimics the exposed hydrophobic surface of the folding intermediates. These results indicated that GM inhibits the chaperone activity of HSP70 and may suppress protein folding via inhibition of HSP70 in vivo.

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The yeast aquaglyceroporin Fps1p is a bidirectional arsenite channel.

Publication Date: 2010 Feb 19 PMID: 20026328
Authors: Maciaszczyk-Dziubinska, E. - Migdal, I. - Migocka, M. - Bocer, T. - Wysocki, R.
Journal: FEBS Lett

The stress-activated kinase Hog1p mediates arsenic tolerance by decreasing arsenite influx through the aquaglyceroporin Fps1p in Saccharomyces cerevisiae. Unexpectedly, we found that overexpression of FPS1 increased arsenite tolerance suggesting a physiological role of Fps1p in arsenic detoxification. Consistently, during arsenite treatment transcription of FPS1 gene was strongly upregulated, while Fps1p was not degraded and remained localized to the plasma membrane. Moreover, deletion of FPS1 gene resulted in arsenate sensitivity. Finally, transport experiments revealed that Fps1p in concert with the arsenite transporter Acr3p mediates arsenite efflux.

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Methyl-Typing: an improved and visualized COBRA software for epigenomic studies.

Publication Date: 2010 Feb 19 PMID: 20026327
Authors: Yang, C. H. - Chuang, L. Y. - Cheng, Y. H. - Gu, D. L. - Chen, C. H. - Chang, H. W.
Journal: FEBS Lett

Combined bisulfite restriction analysis (COBRA) is one of the most commonly used methylation quantification methods. However, it focuses on relatively few restriction enzymes. Here, we present Methyl-Typing, a web-based software that provides restriction enzyme mining data for methyl-cytosine-containing sequences following bisulfite-conversion. Gene names, accession numbers, sequences, PCR primers, and file upload are accessible for input. Promoter sequences and restriction enzymes for CpG- and GpC-containing recognition sites are retrieved. Four representative enzymes were tested successfully by COBRA on the experimental work. Therefore, the Methyl-Typing tool provides a comprehensive COBRA-restriction enzyme mining. It is freely available at http://bio.kuas.edu.tw/methyl-typing.

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Panky, a novel photoreceptor-specific ankyrin repeat protein, is a transcriptional cofactor that suppresses CRX-regulated photoreceptor genes.

Publication Date: 2010 Feb 19 PMID: 20026326
Authors: Sanuki, R. - Omori, Y. - Koike, C. - Sato, S. - Furukawa, T.
Journal: FEBS Lett

Neuronal gene transcription is regulated by both transcriptional activators and repressors. While the roles of transactivators in retinal photoreceptor development have been well characterized, the roles of repressors have been poorly understood. We isolated Panky/Ankrd33, a gene encoding an ankyrin repeat-containing protein. Panky-A was specifically expressed in retinal photoreceptors and the pineal gland, and its expression was directly up-regulated by the CRX transcription factor. Subcellular localization of PANKY-A was observed in the nucleus and cytoplasm. Additionally, transactivation analysis suggested that PANKY-A is a transcriptional cofactor that suppresses CRX-activated photoreceptor genes. Furthermore, we found by an electrophoretic mobility shift assay that PANKY inhibited the DNA-binding activity of CRX.

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PCSK9-deficient mice exhibit impaired glucose tolerance and pancreatic islet abnormalities.

Publication Date: 2010 Feb 19 PMID: 20026049
Authors: Mbikay, M. - Sirois, F. - Mayne, J. - Wang, G. S. - Chen, A. - Dewpura, T. - Prat, A. - Seidah, N. G. - Chretien, M. - Scott, F. W.
Journal: FEBS Lett

Proprotein convertase subtilisin/kexin type 9 (PCSK9), a liver-secreted plasma enzyme, restricts hepatic uptake of low-density lipoprotein (LDL) cholesterol by promoting the degradation of LDL receptors (LDLR). PCSK9 and LDLR are also expressed in insulin-producing pancreatic islet beta cells, possibly affecting the function of these cells. Here we show that, compared to control mice, PCSK9-null male mice over 4 months of age carried more LDLR and less insulin in their pancreas; they were hypoinsulinemic, hyperglycemic and glucose-intolerant; their islets exhibited signs of malformation, apoptosis and inflammation. Collectively, these observations suggest that PCSK9 may be necessary for the normal function of pancreatic islets.

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Curcumin inhibits hepatitis C virus replication via suppressing the Akt-SREBP-1 pathway.

Publication Date: 2010 Feb 19 PMID: 20026048
Authors: Kim, K. - Kim, K. H. - Kim, H. Y. - Cho, H. K. - Sakamoto, N. - Cheong, J.
Journal: FEBS Lett

A polyphenolic compound from the curry spice turmeric, curcumin, is known to show anti-viral activity against the influenza virus, adenovirus, coxsackievirus, and the human immunodeficiency virus. However, it remains to be determined whether curcumin can inhibit the replication of hepatitis C virus (HCV). In this study, we showed that curcumin decreases HCV gene expression via suppression of the Akt-SREBP-1 activation, not by NF-kappaB pathway. The combination of curcumin and IFNalpha exerted profound inhibitory effects on HCV replication. Collectively, our results indicate that curcumin can suppress HCV replication in vitro and may be potentially useful as novel anti-HCV reagents.

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Screening-based discovery of drug-like O-GlcNAcase inhibitor scaffolds.

Publication Date: 2010 Feb 19 PMID: 20026047
Authors: Dorfmueller, H. C. - van Aalten, D. M.
Journal: FEBS Lett

O-GlcNAcylation is an essential posttranslational modification in metazoa. Modulation of O-GlcNAc levels with small molecule inhibitors of O-GlcNAc hydrolase (OGA) is a useful strategy to probe the role of this modification in a range of cellular processes. Here we report the discovery of novel, low molecular weight and drug-like O-GlcNAcase inhibitor scaffolds by high-throughput screening. Kinetic and X-ray crystallographic analyses of the binding modes with human/bacterial O-GlcNAcases identify some of these as competitive inhibitors. Comparative kinetic experiments with the mechanistically related human lysosomal hexosaminidases reveal that three of the inhibitor scaffolds show selectivity towards human OGA. These scaffolds provide attractive starting points for the development of non-carbohydrate, drug-like OGA inhibitors.

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