Regulatory function of the P295-T311 motif of the estrogen receptor α - does proteasomal degradation of the receptor induce emergence of peptides implicated in estrogenic responses?

The way in which estrogen receptor α (ERα) mediates gene transcription and hormone-dependent cancer cell proliferation is now being largely reconsidered in view of several recent discoveries. ERα-mediated transcription appears to be a cyclic and transient process where the proteasome - and thus receptor degradation - plays a pivotal role. In view of our recent investigations, which demonstrate the estrogenic activity of a synthetic peptide corresponding to a regulatory motif of the receptor (ERα17p), we propose that ERα proteasomal degradation could induce the emergence of regulatory peptide(s). The latter would function as a signal and contribute to the ERα activation process, amplifying the initial hormonal stimulation and giving rise to sustained estrogenic response

Differential RNA-binding activity of the hnRNP G protein correlated with the sex genotype in the amphibian oocyte

A proteomic approach has enabled the identification of an orthologue of the splicing factor hnRNP G in the amphibians Xenopus tropicalis, Ambystoma mexicanum, Notophthalmus viridescens and Pleurodeles walt, which shows a specific RNA-binding affinity similar to that of the human hnRN G protein. Three isoforms of this protein with a differential binding affinity for a specific RNA probe were identified in the P. walt oocyte. In situ hybridization to lampbrush chromosomes of P. waltl revealed the presence of a family of hnRNP G genes, which were mapped on the Z and W chromosomes and one autosome. This indicates that the isoforms identified in this study are possibly encoded by a gene family linked to the evolution of sex chromosomes similarly to the hnRNP G/RBMX gene family in mammals

Recherche des partenaires de l'amyloïde-bêta 1-42 par spectrométrie de masse

L utilisation de la protéomique et de la spectrométrie de masse est devenue indispensable pour la compréhension au niveau moléculaire de nombreuses pathologies. Le peptide amyloïde bêta (Ab) 1-42 tient un rôle central dans le développement de la maladie d Alzheimer (MA). Cependant, les mécanismes de la toxicité induite par ce peptide sont toujours mal connus. Ce travail vise à identifier les partenaires protéiques de la forme fibrillaire du peptide Ab, afin d'avoir une meilleure comprehénsion des mécanismes moléculaires induits par ce peptide et d'identifier d'éventuels candidats comme cibles thérapeutiques de traitement contre la MA. Pour cela, nous avons mis en place une stratégie de co-précipitation des protéines en interaction avec le peptide Ab 1-42 sous forme fibrillaire, en utilisant des protéines extraites de synaptosomes de rat. L identification des protéines co-précipitées avec les fibrilles est réalisée en LC-MS/MS (Hesse et al. 2011) (ESI-LIT-FTICR). Les résultats obtenus sur six expériences indépendantes nous ont permis d identifier 172 protéines spécifiquement co-précipitées à l Ab. Parmi ces protéines, 11 sont identifiées dans l ensemble des réplicats biologiques Ras-related protein Ral-A, Cytochrome b-c1, amine oxidase B, 3-hydroxyacyl-CoA dehydrogenase type 2, mitochondrial import TOM70, Dynamin-like 120 kDA protein, Succinate dehydrogenase, LETM1, EF-hand domain containing protein, Up-regulated during skeletal muscle growth protein et Dihydrolipoyllysine-residue succinyltransferase component of 2-oxoglutarate dehydrogenase complex.. Certaines de ces protéines sont associées dans la littérature au contrôle de l homéostasie du calcium, ou l organisation des microtubules, qui sont perturbées dans la MA. Afin de pouvoir compléter cette liste nous avons mis au point au laboratoire le couplage entre la chromatographie liquide et les spectromètres de masse équipés d une source MALDI. Ce couplage nous offre des possibilités d anlyses supplémentaires (Chiappetta et al. 2010) ainsi qu une complémentarité d analyse comparé au montage classique (LC-ESI). Pour comprendre la complémentarité protéique et peptidique de ces deux approches(LC-MALDI et LC-ESI) nous avons étudié différents facteurs phyisco-chimiques pouvant induire une discrimination et une ionisation préférentiellePARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Contribution of proteases and cellulases produced by solid-state fermentation to the improvement of corn ethanol production

Abstract By cultivating a strain of Aspergillus tubingensis on agro-industrial by-products using solid-state fermentation technology, a biocatalyst containing more than 130 different enzymes was obtained. The enzymatic complex was composed mainly of hydrolases, among which a protease, an aspergillopepsin, accounted for more than half of the total proteins. Cell-wall-degrading enzymes such as pectinases, cellulases and hemicellulases were also highly represented. Adding the biocatalyst to corn mash at 1 kg/T corn allowed to significantly improve ethanol production performances. The final ethanol concentration was increased by 6.8% and the kinetics was accelerated by 14 h. The aim of this study was to identify the enzymes implicated in the effect on corn ethanol production. By fractionating the biocatalyst, the particular effect of the major enzymes was investigated. Experiments revealed that, together, the protease and two cellulolytic enzymes (an endoglucanase and a β-glucosidase) were responsible for 80% of the overall effect of the biocatalyst. Nevertheless, the crude extract of the biocatalyst showed greater impact than the combination of up to seven purified enzymes, demonstrating the complementary enzymatic complex obtained by solid-state fermentation. This technology could, therefore, be a relevant natural alternative to the use of GMO-derived enzymes in the ethanol industry

A proteomic study reveals novel insights into the diversity of aquaporin forms expressed in the plasma membrane of plant roots.

Aquaporins are channel proteins that facilitate the diffusion of water across cell membranes. The genome of Arabidopsis thaliana encodes 35 full-length aquaporin homologues. Thirteen of them belong to the plasma membrane intrinsic protein (PIP) subfamily and predominantly sit at the plasma membrane (PM). In the present work we combine separations of membrane proteins (by one- and two-dimensional gel electrophoresis) with identification by MS (matrix-assisted laser-desorption ionization-time-of-flight and electrospray-ionization tandem MS) to take an inventory of aquaporin isoforms expressed in the PM of Arabidopsis thaliana roots. Our analysis provides direct evidence for the expression of five PIPs (PIP1;1, PIP1;5, PIP2;1, PIP2;2 and PIP2;7) in the root PM and suggests the presence of at least three other PIP isoforms. In addition, we show that the same PIP isoform can be present under several forms with distinct isoelectric points. More specifically, we identify phosphorylated aquaporins in the PIP1 and PIP2 subgroups and suggest the existence of other post-translational modifications. Their identification should provide clues to reveal novel molecular mechanisms for aquaporin regulation

Two Glutaraldehyde‐Immobilized Trypsin Preparations for Peptide Mapping by Capillary Zone Electrophoresis, Liquid Chromatography, and Mass Spectrometry

International audienc

Quantitative phosphoproteomic analysis reveals shared and specific targets of Arabidopsis mitogen-activated protein kinases (MAPKs) MPK3, MPK4, and MPK6

In Arabidopsis, mitogen-activated protein kinases MPK3, MPK4, and MPK6 constitute essential relays for a variety of functions including cell division, development and innate immunity. Although some substrates of MPK3, MPK4 and MPK6 have been identified, the picture is still far from complete. To identify substrates of these MAPKs likely involved in cell division, growth and development we compared the phosphoproteomes of wild-type and mpk3, mpk4, and mpk6. To study the function of these MAPKs in innate immunity, we analyzed their phosphoproteomes following microbe-associated molecular pattern (MAMP) treatment. Partially overlapping substrates were retrieved for all three MAPKs, showing target specificity to one, two or all three MAPKs in different biological processes. More precisely, our results illustrate the fact that the entity to be defined as a specific or a shared substrate for MAPKs is not a phosphoprotein but a particular (S/T) P phosphorylation site in a given protein. One hundred fifty-two peptides were identified to be differentially phosphorylated in response to MAMP treatment and/or when compared between genotypes and 70 of them could be classified as putative MAPK targets. Biochemical analysis of a number of putative MAPK substrates by phosphorylation and interaction assays confirmed the global phosphoproteome approach. Our study also expands the set of MAPK substrates to involve other protein kinases, including calcium-dependent (CDPK) and sugar nonfermenting (SnRK) protein kinases