Mechanism of Inhibition of Enveloped Virus Membrane Fusion by the Antiviral Drug Arbidol

The broad-spectrum antiviral arbidol (Arb) inhibits cell entry of enveloped viruses by blocking viral fusion with host cell membrane. To better understand Arb mechanism of action, we investigated its interactions with phospholipids and membrane peptides. We demonstrate that Arb associates with phospholipids in the micromolar range. NMR reveals that Arb interacts with the polar head-group of phospholipid at the membrane interface. Fluorescence studies of interactions between Arb and either tryptophan derivatives or membrane peptides reconstituted into liposomes show that Arb interacts with tryptophan in the micromolar range. Interestingly, apparent binding affinities between lipids and tryptophan residues are comparable with those of Arb IC50 of the hepatitis C virus (HCV) membrane fusion. Since tryptophan residues of membrane proteins are known to bind preferentially at the membrane interface, these data suggest that Arb could increase the strength of virus glycoprotein's interactions with the membrane, due to a dual binding mode involving aromatic residues and phospholipids. The resulting complexation would inhibit the expected viral glycoprotein conformational changes required during the fusion process. Our findings pave the way towards the design of new drugs exhibiting Arb-like interfacial membrane binding properties to inhibit early steps of virus entry, i.e., attractive targets to combat viral infection

Evolution des connaissances sur la couverture méso-cénozoïque du plateau vendéen - apports de la campagne sismique SYRRE.

National audienceLa plateforme vendéenne est un secteur clé situé à la croisée de trois domaines géodynamiques : la bordure méridionale du Massif Armoricain varisque affleurant à l'Ile d'Yeu et à Rochebonne, la bordure septentrionale du bassin d'aquitaine/bassin de Parentis (flexure " celta-aquitaine ") et la marge Nord-Gascogne qui a enregistré l'histoire du golfe de Gascogne. L'évolution du remplissage sédimentaire méso-cénozoïque et Plio-Quaternaire et la trame tectonique de la plate-forme continentale vendéenne sont mal connus. En 2005 et 2006, les missions de sismique réflexion Haute Résolution (GEOVEND, GEOVEND06, Géosciences Rennes-BRGM) ont permis de proposer une cartographie des unités sismiques des formations du Jurassique et du Crétacé (Huerta et al., 2008). Mais la synthèse cartographique Terre-Mer (Thinon et al., 2013) a montré des zones d'incohérences cartographiques entre les cartes géologiques existantes. La campagne supplémentaire de Sismique réflexion Très Haute Résolution, entre l'île d'Yeu, Rochebonne et l'île de Ré ", SYRRE, a eu lieu du 7 au 17 Mai 2014, dans le cadre du projet "RGF-plateau continental"* en collaboration entre le BRGM et les universités de Rennes et La Rochelle. La densification du réseau sismique permet de préciser l'extension des bassins tertiaires et des dépôts du Crétacé supérieur et d'imager les géométries des surfaces majeures et des dépôts méso-cénozoïques pour déterminer les directions de progradation et en déduire les aires de subsidence. Elle apporte des éléments pour la reconstitution des paléogéographies du Jurassique au Tertiaire. Elles renseignent sur la répartition des structures, le style et le calendrier de déformation. Cette connaissance permettra d'obtenir une vision globale de la structuration et de la sédimentation du plateau continental vendéen dans le prolongement du plateau continental Sud-Bretagne. Huerta P., Proust J.N., Guennoc P., Thinon I. -2010- Seismic stratigraphy of the Vendée-Armorican Platform of the French Atlantic Shelf: new insights into the history of the North Atlantic Ocean. Bull. Soc. géol. Fr. , t. 181, no 1, pp. 37-50. Thinon I., Baudouin V., Paquet F., Conil P., Béchennec F., Le Bayon B.- 2013- Cartographie géologique harmonisée du littoral des Pays-de-la-Loire - BRGM/RP-62383-FR. 79p. * appartient au programme de recherche et de cartographie Terre-Mer du territoire français du BRGM

Hepatitis C Virus Envelope Glycoprotein E1 Forms Trimers at the Surface of the Virion.

International audienceIn hepatitis C virus (HCV)-infected cells, the envelope glycoproteins E1 and E2 assemble as a heterodimer. To investigate potential changes in the oligomerization of virion-associated envelope proteins, we performed SDS-PAGE under reducing conditions but without thermal denaturation. This revealed the presence of SDS-resistant trimers of E1 in the context of cell-cultured HCV (HCVcc) as well as in the context of HCV pseudoparticles (HCVpp). The formation of E1 trimers was found to depend on the coexpression of E2. To further understand the origin of E1 trimer formation, we coexpressed in bacteria the transmembrane (TM) domains of E1 (TME1) and E2 (TME2) fused to reporter proteins and analyzed the fusion proteins by SDS-PAGE and Western blotting. As expected for strongly interacting TM domains, TME1-TME2 heterodimers resistant to SDS were observed. These analyses also revealed homodimers and homotrimers of TME1, indicating that such complexes are stable species. The N-terminal segment of TME1 exhibits a highly conserved GxxxG sequence, a motif that is well documented to be involved in intramembrane protein-protein interactions. Single or double mutations of the glycine residues (Gly354 and Gly358) in this motif markedly decreased or abrogated the formation of TME1 homotrimers in bacteria, as well as homotrimers of E1 in both HCVpp and HCVcc systems. A concomitant loss of infectivity was observed, indicating that the trimeric form of E1 is essential for virus infectivity. Taken together, these results indicate that E1E2 heterodimers form trimers on HCV particles, and they support the hypothesis that E1 could be a fusion protein.HCV glycoproteins E1 and E2 play an essential role in virus entry into liver cells as well as in virion morphogenesis. In infected cells, these two proteins form a complex in which E2 interacts with cellular receptors, whereas the function of E1 remains poorly understood. However, recent structural data suggest that E1 could be the protein responsible for the process of fusion between viral and cellular membranes. Here we investigated the oligomeric state of HCV envelope glycoproteins. We demonstrate that E1 forms functional trimers after virion assembly and that in addition to the requirement for E2, a determinant for this oligomerization is present in a conserved GxxxG motif located within the E1 transmembrane domain. Taken together, these results indicate that a rearrangement of E1E2 heterodimer complexes likely occurs during the assembly of HCV particles to yield a trimeric form of the E1E2 heterodimer. Gaining structural information on this trimer will be helpful for the design of an anti-HCV vaccine