title: Rab5 and class III phosphoinositide 3-kinase Vps34 are involved in hepatitis C virus NS4B-induced autophagy.
abstract: Autophagy has been shown to facilitate replication or production of hepatitis C virus (HCV); nevertheless, how HCV induces autophagy remains unclear. Here, we demonstrate that HCV nonstructural protein 4B (NS4B) alone can induce autophagy signaling; amino acid residues 1 to 190 of NS4B are sufficient for this induction. Further studies showed that the phosphorylation levels of S6K and 4E-BP1 were not altered, suggesting that the mTOR/S6 kinase pathway and mTOR/4E-BP1 pathway did not contribute to NS4B- or HCV-induced autophagy. Inhibition of Rab5 function by silencing Rab5 or overexpressing dominant-negative Rab5 mutant (S34N) resulted in significant reduction of NS4B- or HCV-induced autophagic vesicle formation. Moreover, the autophagy induction was impaired by inhibition of class III phosphoinositide 3-kinase (PI 3-kinase) Vps34 function. Finally, the coimmunoprecipitation assay indicated that NS4B formed a complex with Rab5 and Vps34, supporting the notion that Rab5 and Vps34 are involved in NS4B-induced autophagy. Taken together, these results not only reveal a novel role of NS4B in autophagy but also offer a clue to the mechanism of HCV-induced autophagy.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Wen-Chi
authors.initials: WC
authors.lastname: Su
authors.forename: Ti-Chun
authors.initials: TC
authors.lastname: Chao
authors.forename: Yih-Leh
authors.initials: YL
authors.lastname: Huang
authors.forename: Shih-Che
authors.initials: SC
authors.lastname: Weng
authors.forename: King-Song
authors.initials: KS
authors.lastname: Jeng
authors.forename: Michael M C
authors.initials: MM
authors.lastname: Lai
mesh_terms: D001343:Autophagy; D002460:Cell Line; D058546:Class III Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D020868:Gene Silencing; D016174:Hepacivirus / Q000472:pathogenicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D050505:Mutant Proteins; C080107:NS4B protein, flavivirus; D017361:Viral Nonstructural Proteins; D058546:Class III Phosphatidylinositol 3-Kinases; D020696:rab5 GTP-Binding Proteins