Chikungunya virus-induced autophagy delays caspase-dependent cell death

Autophagy is an important survival pathway and can participate in the host response to infection. Studying Chikungunya virus (CHIKV), the causative agent of a major epidemic in India, Southeast Asia, and southern Europe, we reveal a novel mechanism by which autophagy limits cell death and mortality after infection. We use biochemical studies and single cell multispectral assays to demonstrate that direct infection triggers both apoptosis and autophagy. CHIKV-induced autophagy is mediated by the independent induction of endoplasmic reticulum and oxidative stress pathways. These cellular responses delay apoptotic cell death by inducing the IRE1α–XBP-1 pathway in conjunction with ROS-mediated mTOR inhibition. Silencing of autophagy genes resulted in enhanced intrinsic and extrinsic apoptosis, favoring viral propagation in cultured cells. Providing in vivo evidence for the relevance of our findings, Atg16L(HM) mice, which display reduced levels of autophagy, exhibited increased lethality and showed a higher sensitivity to CHIKV-induced apoptosis. Based on kinetic studies and the observation that features of apoptosis and autophagy were mutually exclusive, we conclude that autophagy inhibits caspase-dependent cell death but is ultimately overwhelmed by viral replication. Our study suggests that inducers of autophagy may limit the pathogenesis of acute Chikungunya disease

IRGM Is a Common Target of RNA Viruses that Subvert the Autophagy Network

Autophagy is a conserved degradative pathway used as a host defense mechanism against intracellular pathogens. However, several viruses can evade or subvert autophagy to insure their own replication. Nevertheless, the molecular details of viral interaction with autophagy remain largely unknown. We have determined the ability of 83 proteins of several families of RNA viruses (Paramyxoviridae, Flaviviridae, Orthomyxoviridae, Retroviridae and Togaviridae), to interact with 44 human autophagy-associated proteins using yeast two-hybrid and bioinformatic analysis. We found that the autophagy network is highly targeted by RNA viruses. Although central to autophagy, targeted proteins have also a high number of connections with proteins of other cellular functions. Interestingly, immunity-associated GTPase family M (IRGM), the most targeted protein, was found to interact with the autophagy-associated proteins ATG5, ATG10, MAP1CL3C and SH3GLB1. Strikingly, reduction of IRGM expression using small interfering RNA impairs both Measles virus (MeV), Hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1)-induced autophagy and viral particle production. Moreover we found that the expression of IRGM-interacting MeV-C, HCV-NS3 or HIV-NEF proteins per se is sufficient to induce autophagy, through an IRGM dependent pathway. Our work reveals an unexpected role of IRGM in virus-induced autophagy and suggests that several different families of RNA viruses may use common strategies to manipulate autophagy to improve viral infectivity

Éducation thérapeutique pour les enfants drépanocytaires (justifications à la mise en place et initiation de ce projet au CHU de Grenoble)

En 2005 l HAS publie des recommandations pour la prise en charge de la Drépanocytose chez l enfant et l adolescent. L éducation thérapeutique du patient (ETP) y tient un rôle important. Après une mise au point sur la Drépanocytose et l ETP, notre travail a pour objectif de justifier la mise en place d un programme d ETP au CHU de Grenoble. Une revue de la littérature montre qu une simple information délivrée lors des consultations de suivi n est plus suffisante. Des temps spécifiques d ETP sont indispensables. Les publications évaluant ces programmes insistent sur un moindre taux de recours aux services de soins et sur le bénéfice des coping strategy . L analyse des données épidémiologiques réalisée sur notre cohorte confirme l immense différence de symptomatologie entre les patients. Outre les crises douloureuses, les infections ORL sont responsables d une large majorité des recours aux soins et doivent bénéficier pleinement de l apport d un programme d ETP. Une enquête menée auprès de tous les CHU de France métropolitaine souligne la dynamique nationale actuelle avec la mise en place récente de programme d ETP pour une majorité de ces centres. Des entretiens menés auprès de familles suivies au CHU de Grenoble confirment qu elles sont favorables à la création d un tel programme et surtout mettent en lumière certaines difficultés insoupçonnées jusqu à présent. L ensemble des arguments développés permet de conclure à la nécessité d intégrer un programme d ETP à la prise en charge des enfants drépanocytaires. Pour cela une réflexion devra être menée sur la réorganisation du temps de travail de l équipe soignante et la façon de replacer le pédiatre au centre de ce programme.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Molecular determinants of SR-B1-dependent Plasmodium sporozoite entry into hepatocytes

International audienceSporozoite forms of the Plasmodium parasite, the causative agent of malaria, are transmitted by mosquitoes and first infect the liver for an initial round of replication before parasite proliferation in the blood. The molecular mechanisms involved during sporozoite invasion of hepatocytes remain poorly understood. Two receptors of the Hepatitis C virus (HCV), the tetraspanin CD81 and the scavenger receptor class B type 1 (SR-B1), play an important role during the entry of Plasmodium sporozoites into hepatocytes. In contrast to HCV entry, which requires both CD81 and SR-B1 together with additional host factors, CD81 and SR-B1 operate independently during malaria liver infection. Sporozoites from human-infecting P. falciparum and P. vivax rely respectively on CD81 or SR-B1. Rodent-infecting P. berghei can use SR-B1 to infect host cells as an alternative pathway to CD81, providing a tractable model to investigate the role of SR-B1 during Plasmodium liver infection. Here we show that mouse SR-B1 is less functional as compared to human SR-B1 during P. berghei infection. We took advantage of this functional difference to investigate the structural determinants of SR-B1 required for infection. Using a structure-guided strategy and chimeric mouse/human SR-B1 constructs, we could map the functional region of human SR-B1 within apical loops, suggesting that this region of the protein may play a crucial role for interaction of sporozoite ligands with host cells and thus the very first step of Plasmodium infection

Le classicisme hollywoodien

Dès les années 1920, et plus nettement encore au cours des décennies suivantes, le cinéma américain fut déclaré « classique » en dépit de son évidente modernité. Ses défenseurs affirmaient ainsi leur confiance dans un art populaire et neuf, que ses liens avec l’industrie avaient très tôt rendu suspect aux gardiens de la tradition. Cette première phase de légitimation passée, ce fut ailleurs qu’on chercha la qualité classique d’Hollywood : dans la conformité à des normes stylistiques et narratives, dans la structure économique des studios de l’âge d’or, dans leur puissance d’innovation esthétique et technologique. À se déplacer ainsi, de génération en génération, la notion de « classicisme hollywoodien » devenait source de malentendus. Ce cinéma, d’abord destiné à des millions de spectateurs avides de divertissement, avait-il vraiment été classique, au sens que l’histoire du goût donne à ce mot ? Des films soumis à de stricts impératifs économiques, moraux et idéologiques peuvent-ils devenir des modèles pour penser l’homme et le monde ? Faut-il entendre désormais que Ford et Hawks sont classiques à l’égal de Racine ou Poussin ? À partir de ces interrogations, un séminaire puis un colloque organisés à l’École normale supérieure en 2007 ont réuni des chercheurs de toutes disciplines, invités à revisiter les grandes problématiques qui structurent la période classique d’Hollywood : acteurs et stars, genres, auteurs, fiction, transferts culturels, histoire et idéologie, évolution du studio system, analyse du style classique et de son héritage. Sur toutes ces questions, ce recueil ne se veut pas un bilan, mais l’occasion d’ouvrir de nouvelles perspectives à la recherche en études cinématographiques, et d’affirmer l’importance historique et symbolique de l’âge d’or hollywoodien dans l’histoire de l’art, de la culture et des idées

Drosophila Translational Elongation Factor-1γ Is Modified in Response to DOA Kinase Activity and Is Essential for Cellular Viability

Drosophila translational elongation factor-1γ (EF1γ) interacts in the yeast two-hybrid system with DOA, the LAMMER protein kinase of Drosophila. Analysis of mutant EF1γ alleles reveals that the locus encodes a structurally conserved protein essential for both organismal and cellular survival. Although no genetic interactions were detected in combinations with mutations in EF1α, an EF1γ allele enhanced mutant phenotypes of Doa alleles. A predicted LAMMER kinase phosphorylation site conserved near the C terminus of all EF1γ orthologs is a phosphorylation site in vitro for both Drosophila DOA and tobacco PK12 LAMMER kinases. EF1γ protein derived from Doa mutant flies migrates with altered mobility on SDS gels, consistent with it being an in vivo substrate of DOA kinase. However, the aberrant mobility appears to be due to a secondary protein modification, since the mobility of EF1γ protein obtained from wild-type Drosophila is unaltered following treatment with several nonspecific phosphatases. Expression of a construct expressing a serine-to-alanine substitution in the LAMMER kinase phosphorylation site into the fly germline rescued null EF1γ alleles but at reduced efficiency compared to a wild-type construct. Our data suggest that EF1γ functions in vital cellular processes in addition to translational elongation and is a LAMMER kinase substrate in vivo

Production of Infectious Hepatitis C Virus in Primary Cultures of Human Adult Hepatocytes

International audienc

Interference with the production of infectious viral particles and bimodal inhibition of replication are broadly conserved antiviral properties of IFITMs.

IFITMs are broad antiviral factors that block incoming virions in endosomal vesicles, protecting target cells from infection. In the case of HIV-1, we and others reported the existence of an additional antiviral mechanism through which IFITMs lead to the production of virions of reduced infectivity. However, whether this second mechanism of inhibition is unique to HIV or extends to other viruses is currently unknown. To address this question, we have analyzed the susceptibility of a broad spectrum of viruses to the negative imprinting of the virion particles infectivity by IFITMs. The results we have gathered indicate that this second antiviral property of IFITMs extends well beyond HIV and we were able to identify viruses susceptible to the three IFITMs altogether (HIV-1, SIV, MLV, MPMV, VSV, MeV, EBOV, WNV), as well as viruses that displayed a member-specific susceptibility (EBV, DUGV), or were resistant to all IFITMs (HCV, RVFV, MOPV, AAV). The swapping of genetic elements between resistant and susceptible viruses allowed us to point to specificities in the viral mode of assembly, rather than glycoproteins as dominant factors of susceptibility. However, we also show that, contrarily to X4-, R5-tropic HIV-1 envelopes confer resistance against IFITM3, suggesting that viral receptors add an additional layer of complexity in the IFITMs-HIV interplay. Lastly, we show that the overall antiviral effects ascribed to IFITMs during spreading infections, are the result of a bimodal inhibition in which IFITMs act both by protecting target cells from incoming viruses and in driving the production of virions of reduced infectivity. Overall, our study reports for the first time that the negative imprinting of the virion particles infectivity is a conserved antiviral property of IFITMs and establishes IFITMs as a paradigm of restriction factor capable of interfering with two distinct phases of a virus life cycle