Les proteines de choc thermique murines de 89 Kd : caracterisation et expression differentielle apres un choc thermique et au cours du developpement embryonnaire precoce de la souris

SIGLECNRS T 58620 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Caractérisation des partenaires de la Kinase neuronale PAK3, et rôle de ces complexes dans la plasticité neuronale

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

VOIE DE SIGNALISATION MAP KINASE/ERK ET SECOND MESSAGER AMPC DANS LE SYSTEME NERVEUX (CONTRIBUTION DE LA REGULATION DE LA PROTEINE B-RAF PAR LA PKA)

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Mouse 89 kD heat shock protein

International audienceUnstressed early mouse embryos have been previously shown [1] to synthesize at very high rates 70 and 89 kD proteins belonging to the heat shock protein (HSP) family. But it was not clear whether expression of heat shock-inducible or non-inducible (cognate) genes accounted for this spontaneous synthesis. In this report we show that the 89 kD mouse HSP can be separated into two proteins by high resolution PAGE. These two components show distinct but related peptide pattern after limited proteolysis. They are synthesized from distinct mRNAs. One of these proteins--HSP89f--is synthesized at a high rate by unstressed cells and its synthesis is rather insensitive to stress, whereas synthesis of the other protein--HSP89s--is strongly stimulated by heat shock in fibroblasts. Both HSP89f and HSP89s are major proteins synthesized in unstressed mouse preimplantation embryos and embryonal carcinoma (EC) cells. After in vitro differentiation of the EC cells the spontaneous synthesis of HSP89s decreases. Thus spontaneous expression of a mammalian inducible HSP is developmentally regulated

The Mouse B- raf Gene Encodes Multiple Protein Isoforms with Tissue-specific Expression

International audienceThe c-Rmil/B-raf proto-oncogene is a member of the mil/raf family encoding serine/threonine protein kinases shown to be involved in signal transduction from the membrane to the nucleus. We isolated from a mouse brain library B-raf cDNAs containing a previously unidentified 36-base pair alternatively spliced exon located between exons 8 and 9 and, therefore, designated exon 8b. Human and mouse B-raf mRNAs also contain the 120-base pair alternatively spliced exon 10 previously described in the avian c-Rmil gene. Independent splicing of these two exons, located between the conserved region 2 (CR2) and the catalytic domain (CR3) gives rise to mRNAs potentially encoding four distinct proteins. By using specific sera generated against different portions of B-Raf, we identified at least 10 protein isoforms in adult mouse tissues. Some isoforms, in the range of 69-72 kDa, are not recognized by antisera directed against peptides encoded by exons 1 and 2, indicating the existence of B-Raf proteins with two different NH2 extremities. The other isoforms, in the range of 79-99 kDa, contain the amino acids encoded by exons 1 and 2, by either or both of the alternatively spliced exons, and, possibly, by another of the unidentified exon. Analysis of B-raf mRNA expression by reverse transcriptase-polymerase chain reaction and immunocharacterization of B-Raf proteins in different tissues of the adult mouse showed a tissue-specific pattern of B-Raf isoforms expression. Interestingly, isoforms containing amino acids encoded by exon 10 are specifically expressed in neural tissues. Taken together, these results suggest that distinct B-Raf proteins could be involved, in a tissue-specific manner, in signal transduction pathways

[Experimental study of mechanisms of neuronal death in the course oh HIV infection].

International audienceThe HIV1 virus and its envelope glycoprotein gp120 are toxic for human neurones in vitro. This neurotoxicity is, at least partially, of an apoptotic nature, resulting from the interaction of gp120 with the neuronal membrane which leads to perturbations of intracellular signaling systems. These latter bring about on the one hand a raising of [Ca2+]i partly due to the potentiation of the NMDA receptor response to endogenous glutamate and on the other hand the activation of certain MAP kinases (ERK and JNK) which lead to the initiation of the cell death program

Phosphorylation by PKA of a site unique to B-Raf kinase. [La kinase B-Raf est phosphorylée par la PKA sur un site non conservé au sein de la famille Raf].

The Raf kinases serve as central intermediates to relay signals from Ras to ERK. Cell-specific effects of these signals on growth, differentiation and survival can be observed due to the recruitment of different isoenzymes of the Raf family. The in vitro phosphorylation of a site unique to B-Raf (Ser429) has been proposed to be responsible for the negative regulation of the isoenzyme by Akt. Using phosphopetide mapping and site-directed mutagenesis we showed that Ser429 is phosphorylated upon cAMP elevation in PC12 cells and proposed that PKA is a major kinase phosphorylating the B-Raf-specific site in vivo

[Experimental study of mechanisms of neuronal death in the course oh HIV infection].

International audienceThe HIV1 virus and its envelope glycoprotein gp120 are toxic for human neurones in vitro. This neurotoxicity is, at least partially, of an apoptotic nature, resulting from the interaction of gp120 with the neuronal membrane which leads to perturbations of intracellular signaling systems. These latter bring about on the one hand a raising of [Ca2+]i partly due to the potentiation of the NMDA receptor response to endogenous glutamate and on the other hand the activation of certain MAP kinases (ERK and JNK) which lead to the initiation of the cell death program