title: Interactions between viral nonstructural proteins and host protein hVAP-33 mediate the formation of hepatitis C virus RNA replication complex on lipid raft.
abstract: The lipid raft membrane has been shown to be the site of hepatitis C virus (HCV) RNA replication. The mechanism of formation of the replication complex is not clear. We show here that the formation of the HCV RNA replication complex on lipid raft (detergent-resistant membranes) requires interactions among the HCV nonstructural (NS) proteins and may be initiated by the precursor of NS4B, which has the intrinsic property of anchoring to lipid raft membrane. In hepatocyte cell lines containing an HCV RNA replicon, most of the other NS proteins, including NS5A, NS5B, and NS3, were also localized to the detergent-resistant membranes. However, when individually expressed, only NS4B was associated exclusively with lipid raft. In contrast, NS5B and NS3 were localized to detergent-sensitive membrane and cytosolic fractions, respectively. NS5A was localized to both detergent-sensitive and -resistant membrane fractions. Furthermore, we show that a cellular vesicle membrane transport protein named hVAP-33 (the human homologue of the 33-kDa vesicle-associated membrane protein-associated protein), which binds to both NS5A and NS5B, plays a critical role in the formation of HCV replication complex. The hVAP-33 protein is partially associated with the detergent-resistant membrane fraction. The expression of dominant-negative mutants and small interfering RNA of hVAP-33 in HCV replicon cells resulted in the relocation of NS5B from detergent-resistant to detergent-sensitive membranes. Correspondingly, the amounts of both HCV RNA and proteins in the cells were reduced, indicating that hVAP-33 is critical for the formation of HCV replication complex and RNA replication. These results indicate that protein-protein interactions among the various HCV NS proteins and hVAP-33 are important for the formation of HCV replication complex.
authors.affiliation: Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, California 90033, USA.
authors.forename: Lu
authors.initials: L
authors.lastname: Gao
authors.forename: Hideki
authors.initials: H
authors.lastname: Aizaki
authors.forename: Jian-Wen
authors.initials: JW
authors.lastname: He
authors.forename: Michael M C
authors.initials: MM
authors.lastname: Lai
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003902:Detergents / Q000494:pharmacology; D016174:Hepacivirus / Q000235:genetics / Q000502:physiology*; D006801:Humans; D046911:Macromolecular Substances; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012995:Solubility / Q000187:drug effects; D033921:Vesicular Transport Proteins; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D014779:Virus Replication; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; D012324:RNA-Dependent RNA Polymerase
chemical_list: D002352:Carrier Proteins; D003902:Detergents; D046911:Macromolecular Substances; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D012367:RNA, Viral; D033921:Vesicular Transport Proteins; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases; C093542:NS4 protein, hepatitis C virus; C114051:VAPA protein, human; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase