title: FIG4 is a hepatitis C virus particle-bound protein implicated in virion morphogenesis and infectivity with cholesteryl ester modulation potential.
abstract: There is growing evidence that virus particles also contain host cell proteins, which provide viruses with certain properties required for entry and release. A proteomic analysis performed on double-gradient-purified hepatitis C virus (HCV) from two highly viraemic patients identified the phosphatidylinositol 3,5-bisphosphate 5-phosphatase FIG4 (KIAA0274) as part of the viral particles. We validated the association using immunoelectron microscopy, immunoprecipitation and neutralization assays in vitro as well as patient-derived virus particles. RNA interference-mediated reduction of FIG4 expression decreased cholesteryl ester (CE) levels along with intra- and extracellular viral infectivity without affecting HCV RNA levels. Likewise, overexpressing FIG4 increased intracellular CE levels as well as intra- and extracellular viral infectivity without affecting viral RNA levels. Triglyceride levels and lipid droplet (LD) parameters remained unaffected. The 3,5-bisphosphate 5-phosphatase active site of FIG4 was found to strongly condition these results. Whilst FIG4 was found to localize to areas corresponding to viral assembly sites, at the immediate vicinity of LDs in calnexin-positive and HCV core-positive regions, no implication of FIG4 in the secretory pathway of the hepatocytes could be found using either FIG4-null mice, in vitro morphometry or functional assays of the ERGIC/Golgi compartments. This indicates that FIG4-dependent modulation of HCV infectivity is unrelated to alterations in the functionality of the secretory pathway. As a result of the documented implication of CE in the composition and infectivity of HCV particles, these results suggest that FIG4 binds to HCV and modulates particle formation in a CE-related manner.
authors.affiliation: Pathogenesis of Hepatitis B and C - DEVweCAN LabEx, INSERM U1052-CNRS 5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, 69008 Lyon, France.
authors.forename: Jessica
authors.initials: J
authors.lastname: Cottarel
authors.affiliation: Pathogenesis of Hepatitis B and C - DEVweCAN LabEx, INSERM U1052-CNRS 5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, 69008 Lyon, France.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Plissonnier
authors.affiliation: Canary Center for Cancer Early Detection, Department of Radiology, Stanford University School of Medicine, Palo Alto, CA 94304, USA.
authors.forename: Majlinda
authors.initials: M
authors.lastname: Kullolli
authors.affiliation: Canary Center for Cancer Early Detection, Department of Radiology, Stanford University School of Medicine, Palo Alto, CA 94304, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Pitteri
authors.affiliation: Department of Clinical Pathology, University of Geneva, Geneva, Switzerland.
authors.forename: Sophie
authors.initials: S
authors.lastname: Clément
authors.affiliation: Department of Biology, University of Konstanz, Germany.
authors.forename: Valentina
authors.initials: V
authors.lastname: Millarte
authors.affiliation: Hôpital d'Orléans, 45000 Orléans, France.
authors.forename: Si-Nafa
authors.initials: SN
authors.lastname: Si-Ahmed
authors.affiliation: Department of Biology, University of Konstanz, Germany.|Hôpital d'Orléans, 45000 Orléans, France.
authors.forename: Hesso
authors.initials: H
authors.lastname: Farhan
authors.affiliation: Pathogenesis of Hepatitis B and C - DEVweCAN LabEx, INSERM U1052-CNRS 5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, 69008 Lyon, France.|Hospices Civils de Lyon, Service d'Hépatogastroentérologie, 69001 Lyon, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Zoulim
authors.affiliation: Pathogenesis of Hepatitis B and C - DEVweCAN LabEx, INSERM U1052-CNRS 5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, 69008 Lyon, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Parent
mesh_terms: D002460:Cell Line; D002788:Cholesterol Esters / Q000378:metabolism*; D005420:Flavoproteins / Q000302:isolation & purification / Q000378:metabolism*; D016174:Hepacivirus / Q000737:chemistry* / Q000502:physiology*; D022781:Hepatocytes / Q000821:virology; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D016253:Microscopy, Immunoelectron; D009500:Neutralization Tests; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D014771:Virion / Q000737:chemistry; D019065:Virus Assembly; D053586:Virus Internalization
chemical_list: D002788:Cholesterol Esters; D005420:Flavoproteins; C522215:FIG4 protein, human; D010744:Phosphoric Monoester Hydrolases