Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan.
J Virol. 2011 Oct;85(20):10561-71. doi: 10.1128/JVI.00173-11. Epub 2011 Aug 10.
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.
自噬已被证明有利于丙型肝炎病毒（HCV）的复制或产生；然而，HCV 如何诱导自噬尚不清楚。在这里，我们证明 HCV 非结构蛋白 4B（NS4B）本身可以诱导自噬信号；NS4B 的 1 到 190 个氨基酸残基足以诱导自噬。进一步的研究表明，S6K 和 4E-BP1 的磷酸化水平没有改变，这表明 mTOR/S6 激酶途径和 mTOR/4E-BP1 途径与 NS4B 或 HCV 诱导的自噬无关。通过沉默 Rab5 或过表达显性负性 Rab5 突变体（S34N）抑制 Rab5 功能，导致 NS4B 或 HCV 诱导的自噬小泡形成显著减少。此外，抑制 III 类磷酸肌醇 3-激酶（PI 3-kinase）Vps34 的功能会损害自噬的诱导。最后，共免疫沉淀实验表明 NS4B 与 Rab5 和 Vps34 形成复合物，支持 Rab5 和 Vps34 参与 NS4B 诱导的自噬的观点。总之，这些结果不仅揭示了 NS4B 在自噬中的新作用，也为 HCV 诱导自噬的机制提供了线索。
