title: Hepatitis C Virus-Induced Rab32 Aggregation and Its Implications for Virion Assembly.
abstract: Hepatitis C virus (HCV) is highly dependent on cellular factors for viral propagation. Using high-throughput next-generation sequencing, we analyzed the host transcriptomic changes and identified 30 candidate genes which were upregulated in cell culture-grown HCV (HCVcc)-infected cells. Of these candidates, we selected Rab32 for further investigation. Rab32 is a small GTPase that regulates a variety of intracellular membrane-trafficking events in various cell types. In this study, we demonstrated that both mRNA and protein levels of Rab32 were increased in HCV-infected cells. Furthermore, we showed that HCV infection converted the predominantly expressed GTP-bound Rab32 to GDP-bound Rab32, contributing to the aggregation of Rab32 and thus making it less sensitive to cellular degradation machinery. In addition, GDP-bound Rab32 selectively interacted with HCV core protein and deposited core protein into the endoplasmic reticulum (ER)-associated Rab32-derived aggregated structures in the perinuclear region, which were likely to be viral assembly sites. Using RNA interference technology, we demonstrated that Rab32 was required for the assembly step but not for other stages of the HCV life cycle. Taken together, these data suggest that HCV may modulate Rab32 activity to facilitate virion assembly.
  
  
  OBJECTIVE
  Rab32, a member of the Ras superfamily of small GTPases, regulates various intracellular membrane-trafficking events in many cell types. In this study, we showed that HCV infection concomitantly increased Rab32 expression at the transcriptional level and altered the balance between GDP- and GTP-bound Rab32 toward production of Rab32-GDP. GDP-bound Rab32 selectively interacted with HCV core protein and enriched core in the ER-associated Rab32-derived aggregated structures that were probably necessary for viral assembly. Indeed, we showed that Rab32 was specifically required for the assembly of HCV. Collectively, our study identifies that Rab32 is a novel host factor essential for HCV particle assembly.
authors.affiliation: National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea.
authors.forename: Tu M
authors.initials: TM
authors.lastname: Pham
authors.affiliation: National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea.
authors.forename: Si C
authors.initials: SC
authors.lastname: Tran
authors.affiliation: National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea.
authors.forename: Yun-Sook
authors.initials: YS
authors.lastname: Lim
authors.affiliation: National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea sbhwang@hallym.ac.kr.
authors.forename: Soon B
authors.initials: SB
authors.lastname: Hwang
mesh_terms: D002460:Cell Line; D015870:Gene Expression; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D016174:Hepacivirus / Q000502:physiology*; D006526:Hepatitis C / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D054884:Host-Pathogen Interactions; D006801:Humans; D009154:Mutation; D011401:Promoter Regions, Genetic; D066329:Protein Aggregates; D011485:Protein Binding; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism; D019065:Virus Assembly; D014779:Virus Replication; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D066329:Protein Aggregates; D014758:Viral Core Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C466094:Rab32 protein, human; D020691:rab GTP-Binding Proteins
keywords: RNA-Seq; Rab32; core; hepatitis C virus; host factor; virion assembly