Etude structurale et fonctionnelle de la phosphatase humaine PTPN4

The function of signaling proteins is determined by the nature of the domains from which they are made up. A better understanding of cell signaling pathways will result from the study of these domains and their regulation. PTPN4 is a non-receptor tyrosine phosphatase with an anti-apoptotic function. Upon infection with an attenuated rabies virus, its function is hijacked, which subsequently leads to cell death. This phenotype is arises from the interaction of the PDZ binding motif (PBM) of the viral glycoprotein with the PDZ domain of PTPN4. In this study, we show that this PDZ domain is an allosteric inhibitor of the catalytic activity of the PTPN4 phosphatase domain. This is the first description of the regulation of a phosphatase by a PDZ domain. This inhibition is released by the interaction of a ligand to the PDZ domain, such as the viral glycoprotein PBM. Our structural study revealed that the PBM recognition disrupts the transient inter-domain interactions and restores the complete phosphatase catalytic properties. As well, we identified a PTPN4 endogenous ligand, the MAP Kinase p38, which may participate in the regulation of the cellular homeostatic through its interaction with PTPN4. Thus, in addition to its phosphatase regulatory role, the PDZ domain also allows the recruitment of partners and the introduction of substrates to the PTPN4 phosphatase active site. This study contributes to our understanding of the role played by PDZ domains in cell signaling pathways.La fonction des protéines de signalisation est déterminée par la nature des domaines qui les composent. Une meilleure compréhension des voies de signalisation passe par l'étude de ces domaines et de leur régulation. PTPN4 est une tyrosine phosphatase qui joue un rôle anti-apoptotique. Lors de l'infection par une souche atténuée du virus de la rage, sa fonction est perturbée, conduisant à la mort des cellules. Cette perturbation est due à l'interaction du motif de reconnaissance au domaine PDZ (PBM) de la glycoprotéine virale avec le domaine PDZ de PTPN4. Nous avons montré que ce domaine PDZ a un rôle d'inhibiteur allostérique de l'activité catalytique de la phosphatase de PTPN4. Ceci représente la première description de la régulation d'une phosphatase par un domaine PDZ. Cette inhibition est levée lors de la fixation d'un ligand au domaine PDZ, tel que le PBM de la glycoprotéine virale. Notre étude structurale révèle que la fixation d'un PBM perturbe les interactions transitoires entre les deux domaines et rétablit ainsi les propriétés catalytiques de la phosphatase. Nous avons par ailleurs identifié un ligand endogène de PTPN4, la MAP Kinase p38 qui, à travers son interaction avec PTPN4, participerait à la régulation de l'homéostasie cellulaire. La formation du complexe implique le recrutement du PBM de p38 par le domaine PDZ de PTPN4. Ainsi, en plus d'avoir une fonction de régulation du domaine phosphatase, le domaine PDZ permet également le recrutement de partenaires et la présentation de substrats au site actif de la phosphatase de PTPN4. Cette étude contribue ainsi à améliorer notre connaissance du rôle des domaines PDZ dans les voies de signalisation cellulaires

Projet mathétactiques élaboration d'un modèle d'enseignement des mathématiques liant constructivisme et résolution de problèmes /

Également disponible en version papierTitre de l'écran-titre (visionné le 5 déc. 2009)Bibliogr.: p. 133-14

Clinical Chorioamnionitis and Neurodevelopment at 5 Years of Age in Children Born Preterm: The EPIPAGE-2 Cohort Study.

OBJECTIVE To assess the association between clinical chorioamnionitis and neurodevelopmental disorders at 5 years of age in children born preterm. STUDY DESIGN EPIPAGE 2 is a national, population-based cohort study of children born before 35 weeks of gestation in France in 2011. We included infants born alive between 24+0 and 34+6 weeks following preterm labor (PTL) or preterm premature rupture of membranes (PPROM). Clinical chorioamnionitis was defined as maternal fever before labor (>37.8°C) with at least two of the following criteria: maternal tachycardia, hyperleukocytosis, uterine contractions, purulent amniotic fluid, or fetal tachycardia. The primary outcome was a composite including cerebral palsy, coordination disorders, cognitive disorders, sensory disorders, or behavioral disorders. We also analyzed each of these disorders separately as secondary outcomes. We performed a multivariable analysis using logistic regression models. We accounted for the non-independence of twins and missing data by generalized estimating equation models and multiple imputations, respectively. RESULTS Among 2927 children alive at 5 years of age, 124 (3%) were born in a context of clinical chorioamnionitis. Overall, 8.2% and 9.6% of children exposed and unexposed respectively to clinical chorioamnionitis had moderate-to-severe neurodevelopmental disorders. After multiple imputations and multivariable analysis, clinical chorioamnionitis was not associated with the occurrence of moderate-to-severe neurodevelopmental disorders (adjusted odds ratio = 0.9, 95%CI: 0.5-1.8). CONCLUSION We did not find any association between clinical chorioamnionitis and neurodevelopmental disorders at 5 years of age in children born before 35 weeks of gestation after PTL or PPROM

Conformation-specific inhibitors of activated Ras GTPases reveal limited Ras dependency of patient-derived cancer organoids

The small GTPases H, K, and NRAS are molecular switches indispensable for proper regulation of cellular proliferation and growth. Several mutations in the genes encoding members of this protein family are associated with cancer and result in aberrant activation of signaling processes caused by a deregulated recruitment of downstream effector proteins. In this study, we engineered variants of the Ras-binding domain (RBD) of the C-Raf proto-oncogene, Ser/Thr kinase (CRAF). These variants bound with high affinity with the effector-binding site of Ras in an active conformation. Structural characterization disclosed how the newly identified RBD mutations cooperate and thereby enhance affinity with the effector-binding site in Ras compared with WT RBD. The engineered RBD variants closely mimicked the interaction mode of naturally occurring Ras effectors and acted as dominant-negative affinity reagents that block Ras signal transduction. Experiments with cancer cells showed that expression of these RBD variants inhibits Ras signaling, reducing cell growth and inducing apoptosis. Using these optimized RBD variants, we stratified patient-derived colorectal cancer organoids with known Ras mutational status according to their response to Ras inhibition. These results revealed that the presence of Ras mutations was insufficient to predict sensitivity to Ras inhibition, suggesting that not all of these tumors required Ras signaling for proliferation. In summary, by engineering the Ras/Raf interface of the CRAF-RBD, we identified potent and selective inhibitors of Ras in its active conformation that outcompete binding of Ras-signaling effectors

L’EROP : 10 ans pour le rétablissement des oiseaux de proie au Québec

L’Équipe de rétablissement des oiseaux de proie du Québec (EROP) a été fondée en 2004, à la suite de la fusion des équipes de rétablissement du faucon pèlerin (Falco peregrinus), du pygargue à tête blanche (Haliaeetus leucocephalus) et de l’aigle royal (Aquila chrysaetos). À ces espèces d’intérêt pour l’EROP s’est ajouté récemment le hibou des marais (Asio flammeus). À l’aide des plans de rétablissement de chacune des espèces, l’EROP veille à la mise en oeuvre de mesures de conservation (p. ex. acquisition de connaissances, sensibilisation, protection) visant à redresser la situation des populations d’oiseaux de proie en situation précaire au Québec. Cet article présente le mandat, le mode de fonctionnement et les principales réalisations de l’EROP au cours de la dernière décennie. The Québec raptor recovery team (EROP) was established in 2004 following the merger of the peregrine falcon (Falcoperegrinus), bald eagle (Haliaeetus leucocephalus) and golden eagle (Aquilachrysaetos) recovery teams. Recently, the short-eared owl (Asioflammeus) has also been added to the list of species covered by EROP. The team aims to foster conservation measures (e.g., data collection, public awareness and protection) to improve the population status of endangered birds of prey, and achieves this through the publication of species recovery plans. This article outlines the mission, and the working and main achievements of EROP over the past decade

Rules Governing Selective Protein Carbonylation

BACKGROUND:Carbonyl derivatives are mainly formed by direct metal-catalysed oxidation (MCO) attacks on the amino-acid side chains of proline, arginine, lysine and threonine residues. For reasons unknown, only some proteins are prone to carbonylation. METHODOLOGY/PRINCIPAL FINDINGS:we used mass spectrometry analysis to identify carbonylated sites in: BSA that had undergone in vitro MCO, and 23 carbonylated proteins in Escherichia coli. The presence of a carbonylated site rendered the neighbouring carbonylatable site more prone to carbonylation. Most carbonylated sites were present within hot spots of carbonylation. These observations led us to suggest rules for identifying sites more prone to carbonylation. We used these rules to design an in silico model (available at http://www.lcb.cnrs-mrs.fr/CSPD/), allowing an effective and accurate prediction of sites and of proteins more prone to carbonylation in the E. coli proteome. CONCLUSIONS/SIGNIFICANCE:We observed that proteins evolve to either selectively maintain or lose predicted hot spots of carbonylation depending on their biological function. As our predictive model also allows efficient detection of carbonylated proteins in Bacillus subtilis, we believe that our model may be extended to direct MCO attacks in all organisms

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

β-Aminoisobutyric Acid Induces Browning of White Fat and Hepatic β-Oxidation and Is Inversely Correlated with Cardiometabolic Risk Factors

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) regulates metabolic genes in skeletal muscle and contributes to the response of muscle to exercise. Muscle PGC-1α transgenic expression and exercise both increase the expression of thermogenic genes within white adipose. How the PGC-1α-mediated response to exercise in muscle conveys signals to other tissues remains incompletely defined. We employed a metabolomic approach to examine metabolites secreted from myocytes with forced expression of PGC-1α, and identified β-aminoisobutyric acid (BAIBA) as a small molecule myokine. BAIBA increases the expression of brown adipocyte-specific genes in white adipocytes and β-oxidation in hepatocytes both in vitro and in vivo through a PPARα-mediated mechanism, induces a brown adipose-like phenotype in human pluripotent stem cells, and improves glucose homeostasis in mice. In humans, plasma BAIBA concentrations are increased with exercise and inversely associated with metabolic risk factors. BAIBA may thus contribute to exercise-induced protection from metabolic diseases

Structural and functional study of the human phosphatase PTPN4

La fonction des protéines de signalisation est déterminée par la nature des domaines qui les composent. Une meilleure compréhension des voies de signalisation passe par l'étude de ces domaines et de leur régulation. PTPN4 est une tyrosine phosphatase qui joue un rôle anti-apoptotique. Lors de l'infection par une souche atténuée du virus de la rage, sa fonction est perturbée, conduisant à la mort des cellules. Cette perturbation est due à l'interaction du motif de reconnaissance au domaine PDZ (PBM) de la glycoprotéine virale avec le domaine PDZ de PTPN4. Nous avons montré que ce domaine PDZ a un rôle d'inhibiteur allostérique de l'activité catalytique de la phosphatase de PTPN4. Ceci représente la première description de la régulation d'une phosphatase par un domaine PDZ. Cette inhibition est levée lors de la fixation d'un ligand au domaine PDZ, tel que le PBM de la glycoprotéine virale. Notre étude structurale révèle que la fixation d'un PBM perturbe les interactions transitoires entre les deux domaines et rétablit ainsi les propriétés catalytiques de la phosphatase. Nous avons par ailleurs identifié un ligand endogène de PTPN4, la MAP Kinase p38 qui, à travers son interaction avec PTPN4, participerait à la régulation de l'homéostasie cellulaire. La formation du complexe implique le recrutement du PBM de p38 par le domaine PDZ de PTPN4. Ainsi, en plus d'avoir une fonction de régulation du domaine phosphatase, le domaine PDZ permet également le recrutement de partenaires et la présentation de substrats au site actif de la phosphatase de PTPN4. Cette étude contribue ainsi à améliorer notre connaissance du rôle des domaines PDZ dans les voies de signalisation cellulaires.The function of signaling proteins is determined by the nature of the domains from which they are made up. A better understanding of cell signaling pathways will result from the study of these domains and their regulation. PTPN4 is a non-receptor tyrosine phosphatase with an anti-apoptotic function. Upon infection with an attenuated rabies virus, its function is hijacked, which subsequently leads to cell death. This phenotype is arises from the interaction of the PDZ binding motif (PBM) of the viral glycoprotein with the PDZ domain of PTPN4. In this study, we show that this PDZ domain is an allosteric inhibitor of the catalytic activity of the PTPN4 phosphatase domain. This is the first description of the regulation of a phosphatase by a PDZ domain. This inhibition is released by the interaction of a ligand to the PDZ domain, such as the viral glycoprotein PBM. Our structural study revealed that the PBM recognition disrupts the transient inter-domain interactions and restores the complete phosphatase catalytic properties. As well, we identified a PTPN4 endogenous ligand, the MAP Kinase p38, which may participate in the regulation of the cellular homeostatic through its interaction with PTPN4. Thus, in addition to its phosphatase regulatory role, the PDZ domain also allows the recruitment of partners and the introduction of substrates to the PTPN4 phosphatase active site. This study contributes to our understanding of the role played by PDZ domains in cell signaling pathways