Study of the impact of perilipin polymorphisms in a French population

BACKGROUND: Perilipins are proteins localized at the surface of the lipid droplet in adipocytes, steroid-producing cells and ruptured atherosclerotic plaques playing a role in the regulation of triglyceride deposition and mobilization. We investigated whether perilipin gene polymorphisms were associated with obesity, type 2 diabetes, and their related variables (anthropometric variables, plasma leptin, lipids, glucose and insulin concentrations) in a cross-sectional random sample of 1120 French men and women aged 35 to 65 years old, including 227 obese (BMI ≥ 30 kg/m(2)) and 275 type 2 diabetes subjects. RESULTS: Among 7 perilipin polymorphisms tested, only 2 (rs4578621 and rs894160) of them were frequent enough to be fully investigated and we genotyped the sample using the PCR-RFLP method. No significant associations could be found between any of these polymorphisms and the studied phenotypes. CONCLUSION: The rs4578621 and rs894160 polymorphisms of the perilipin gene are not major genetic determinants of obesity and type 2 diabetes-related phenotypes in a random sample of French men and women

Degradation of receptor tyrosine kinase Met by proteolytic cleavages

La dérégulation de la signalisation du récepteur tyrosine kinase Met et de son ligand l'HGF/SF est associée à la progression tumorale et à la métastase dans de nombreux types de cancers. En condition de stress et en absence de ligand, Met est clivé par des caspases dans le domaine juxta-membranaire et libère un fragment proapoptotique dans le cytoplasme, p40 Met. J'ai pu montrer qu'un clivage C-terminal de Met créée une séquentialité dans ces clivages. Le clivage C-terminal du récepteur Met est important dans la formation du fragment apoptotique mais n'affecte pas les réponses biologiques induites par l’HGF/SF. D'autre part, Met est une cible de la « presenilin-dependent regulated intramembrane proteolysis » (ou PS-RIP). Ce processus de dégradation implique un double clivage séquentiel par des métalloprotéases membranaires puis par le complexe g-secrétase. Ces clivages régulent la demi-vie du récepteur Met et préviennent son activation en absence de ligand. Suite au clivage par les métalloprotéases, Met peut également échapper au complexe g-secrétase par son internalisation préalable. Les fragments générés sont alors dégradés par le lysosome. Les fragments de ces deux voies de dégradation ont la capacité de transformer des fibroblastes. De façon intéressante, l’analyse de xénogreffes de tumeurs humaines chez des souris a montré une accumulation de ces fragments. Nous proposons donc que les voies de dégradation PS-RIP et lysosomale préviennent l’accumulation de fragments délétères de Met. Les différents clivages du récepteur Met permettent de réguler son action en absence d'HGF/SF et pourraient donc jouer un rôle important dans les réponses physiologiques.Signalling dysregulation of receptor tyrosine kinase Met and its ligand the HGF/SF (Hepatocyte Growth Factor/Scatter Factors) is associated with tumor growth and metastasis in numerous cancer. Iin stress condition and without its ligand, Met is cleaved by caspases in the juxtamembrane domain which liberates a proapoptotic fragment in cytoplasm, p40 Met. I have shown that a C-terminal cleavage of Met creates a hierarchical organization of these cleavages. The C-terminal cleavage of Met receptor is important to generate apoptotic fragment but does not affect the biological responses induced by the HGF/SF. On the other hand, Met is targeted by PreSenilin-dependent Regulated Intramembrane Proteolysis (called PS-RIP). This proteolytic process of degradation involves two sequential cleavages by membranous metalloproteases and by g-secretase complex. These cleavages regulate half-life of Met receptor and prevent its activation without ligand.Following the cleavage by metalloproteases, Met can escape from g-secretase complex through its prior internalization. Generated fragments are then degraded by the lysosome. Fragments of both degradation patways are able to transform fibroblasts. Interestingly, human tumor xenografts in mice display accumulation of these fragments, suggesting these PS-RIP and lysosomal degradations pathways prevent accumulation of deleterious fragments of Met.Different cleavages of Met receptor can regulate its action without HGF/SF and could have an important role in physiological responses

Dégradation du récepteur tyrosine kinase Met par clivages protéolytiques

La dérégulation de la signalisation du récepteur tyrosine kinase Met et de son ligand l'HGF/SF est associée à la progression tumorale et à la métastase dans de nombreux types de cancers. En condition de stress et en absence de ligand, Met est clivé par des caspases dans le domaine juxta-membranaire et libère un fragment proapoptotique dans le cytoplasme, p40 Met. J'ai pu montrer qu'un clivage C-terminal de Met créée une séquentialité dans ces clivages. Le clivage C-terminal du récepteur Met est important dans la formation du fragment apoptotique mais n'affecte pas les réponses biologiques induites par l HGF/SF. D'autre part, Met est une cible de la presenilin-dependent regulated intramembrane proteolysis (ou PS-RIP). Ce processus de dégradation implique un double clivage séquentiel par des métalloprotéases membranaires puis par le complexe g-secrétase. Ces clivages régulent la demi-vie du récepteur Met et préviennent son activation en absence de ligand. Suite au clivage par les métalloprotéases, Met peut également échapper au complexe g-secrétase par son internalisation préalable. Les fragments générés sont alors dégradés par le lysosome. Les fragments de ces deux voies de dégradation ont la capacité de transformer des fibroblastes. De façon intéressante, l analyse de xénogreffes de tumeurs humaines chez des souris a montré une accumulation de ces fragments. Nous proposons donc que les voies de dégradation PS-RIP et lysosomale préviennent l accumulation de fragments délétères de Met. Les différents clivages du récepteur Met permettent de réguler son action en absence d'HGF/SF et pourraient donc jouer un rôle important dans les réponses physiologiques.Signalling dysregulation of receptor tyrosine kinase Met and its ligand the HGF/SF (Hepatocyte Growth Factor/Scatter Factors) is associated with tumor growth and metastasis in numerous cancer. Iin stress condition and without its ligand, Met is cleaved by caspases in the juxtamembrane domain which liberates a proapoptotic fragment in cytoplasm, p40 Met. I have shown that a C-terminal cleavage of Met creates a hierarchical organization of these cleavages. The C-terminal cleavage of Met receptor is important to generate apoptotic fragment but does not affect the biological responses induced by the HGF/SF. On the other hand, Met is targeted by PreSenilin-dependent Regulated Intramembrane Proteolysis (called PS-RIP). This proteolytic process of degradation involves two sequential cleavages by membranous metalloproteases and by g-secretase complex. These cleavages regulate half-life of Met receptor and prevent its activation without ligand.Following the cleavage by metalloproteases, Met can escape from g-secretase complex through its prior internalization. Generated fragments are then degraded by the lysosome. Fragments of both degradation patways are able to transform fibroblasts. Interestingly, human tumor xenografts in mice display accumulation of these fragments, suggesting these PS-RIP and lysosomal degradations pathways prevent accumulation of deleterious fragments of Met.Different cleavages of Met receptor can regulate its action without HGF/SF and could have an important role in physiological responses.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Phosphorylation of the MET receptor on juxtamembrane tyrosine residue 1001 inhibits its caspase-dependent cleavage

International audienceThe MET tyrosine kinase is the hepatocyte growth factor/scatter factor (HGF/SF) receptor, which elicits multiple biological responses in epithelial cells, including cell survival. We previously demonstrated that in stress conditions, the MET receptor is cleaved by caspases within its juxtamembrane region, generating a pro-apoptotic intracellular fragment of 40 kDa. The caspase cleavage site at aspartic acid D1000 is adjacent to tyrosine Y1001, which when phosphorylated upon MET activation, is involved in CBL recruitment, allowing receptor ubiquitination and down regulation. Scanning mutagenesis of the MET juxtamembrane region led us to demonstrate that V999 and D1000 are essential for the caspase cleavage, while D1000 and Y1001 are essential for CBL recruitment. By examining whether overlapping of these sites leads to a functional interference, an inverse relationship was found between generation of p40 MET and phosphorylation of MET, with a direct involvement of phosphorylated Y1001 in protecting MET against its caspase cleavage. A molecular modeling analysis of caspase 3 interaction with the juxtamembrane region of MET confirmed that phosphorylation of this tyrosine is not compatible with its recognition by active caspase 3. These data demonstrate a direct protection mechanism of an activated phosphorylated MET receptor, against its caspase-dependent cleavage

Additional file 3: of A genome-wide association study identifies candidate loci associated to syringomyelia secondary to Chiari-like malformation in Cavalier King Charles Spaniels

Figure S1. P value distribution inside the CFA15 (24537882-26,252,411 bp) associated region. This region spans 1.7 Mb surrounding SNPs associated to ratio F-d/BC and was identified using Haploview V4.2. (PDF 54 kb

Additional file 2: of A genome-wide association study identifies candidate loci associated to syringomyelia secondary to Chiari-like malformation in Cavalier King Charles Spaniels

Table S2. SNPs suggestive of association to SM in the CKCS breed. This table enlists all SNPs suggestive of association with FDR corrected scores between 0.05 and 0.1. These SNPs were identified following a GWAS using a mixed linear model with age as a covariate on the previously identified traits (Line AE, line AI, angle 3, angle 7, ratio F-d/BC and L4 + L7). (DOCX 15 kb

Down-Regulation of the Met Receptor Tyrosine Kinase by Presenilin-dependent Regulated Intramembrane Proteolysis

Hepatocyte growth factor/scatter factor (HGF/SF) acts through the membrane-anchored Met receptor tyrosine kinase to induce invasive growth. Deregulation of this signaling is associated with tumorigenesis and involves, in most cases, overexpression of the receptor. We demonstrate that Met is processed in epithelial cells by presenilin-dependent regulated intramembrane proteolysis (PS-RIP) independently of ligand stimulation. The proteolytic process involves sequential cleavage by metalloproteases and the γ-secretase complex, leading to generation of labile fragments. In normal epithelial cells, although expression of cleavable Met by PS-RIP is down-regulated, uncleavable Met displayed membrane accumulation and induced ligand-independent motility and morphogenesis. Inversely, in transformed cells, the Met inhibitory antibody DN30 is able to promote Met PS-RIP, resulting in down-regulation of the receptor and inhibition of the Met-dependent invasive growth. This demonstrates the original involvement of a proteolytic process in degradation of the Met receptor implicated in negative regulation of invasive growth