Role of the Endoplasmic Reticulum-associated Degradation (ERAD) Pathway in Degradation of Hepatitis C Virus Envelope Proteins and Production of Virus Particles
Role of the Endoplasmic Reticulum-associated Degradation (ERAD) Pathway in Degradation of Hepatitis C Virus Envelope Proteins and Production of Virus Particles
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DOI：
10.1074/jbc.m111.259085
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发表时间：
2011-10-28
影响因子：
4.8
通讯作者：
Suzuki, Tetsuro
中科院分区：
文献类型：
--
作者：
Saeed, Mohsan;Suzuki, Ryosuke;Suzuki, Tetsuro
病毒感染经常引起宿主细胞中的内质网（ER）应激，导致ER相关降解（ERAD）途径的刺激，其随后靶向未组装的糖蛋白用于泛素化和蛋白酶体降解。然而，ERAD途径在病毒生命周期中的作用尚不明确。在本文中，我们证明，丙型肝炎病毒（HCV）感染激活ERAD途径，这反过来又控制病毒糖蛋白的命运和调节病毒的生产。ERAD蛋白，如EDEM 1和EDEM 3，被发现通过直接的物理相互作用增加HCV包膜蛋白的泛素化。敲低EDEM 1和EDEM 3增加了HCV E2的半衰期以及病毒的产生，而这些蛋白的外源表达减少了感染性病毒颗粒的产生。进一步的研究表明，只有EDEM 1和EDEM 3与SEL 1L结合，SEL 1L是一种ER膜衔接蛋白，参与ERAD底物从ER向细胞质的转运。当HCV感染的细胞用Kifunensine（一种有效的ERAD途径抑制剂）处理时，HCV E2的半衰期增加，病毒产量也增加。Kifunensine抑制EDEM 1和EDEM 3与SEL 1L的结合，从而阻断HCV E2蛋白的泛素化。ERAD途径的化学抑制既不影响日本脑炎病毒（JEV）的生产，也不影响JEV包膜蛋白的稳定性。免疫共沉淀试验表明，EDEM同源物不与JEV包膜蛋白结合。这些发现强调了ERAD途径在特定病毒生命周期中的关键作用。
Viral infections frequently cause endoplasmic reticulum (ER) stress in host cells leading to stimulation of the ER-associated degradation (ERAD) pathway, which subsequently targets unassembled glycoproteins for ubiquitylation and proteasomal degradation. However, the role of the ERAD pathway in the viral life cycle is poorly defined. In this paper, we demonstrate that hepatitis C virus (HCV) infection activates the ERAD pathway, which in turn controls the fate of viral glycoproteins and modulates virus production. ERAD proteins, such as EDEM1 and EDEM3, were found to increase ubiquitylation of HCV envelope proteins via direct physical interaction. Knocking down of EDEM1 and EDEM3 increased the half-life of HCV E2, as well as virus production, whereas exogenous expression of these proteins reduced the production of infectious virus particles. Further investigation revealed that only EDEM1 and EDEM3 bind with SEL1L, an ER membrane adaptor protein involved in translocation of ERAD substrates from the ER to the cytoplasm. When HCV-infected cells were treated with kifunensine, a potent inhibitor of the ERAD pathway, the half-life of HCV E2 increased and so did virus production. Kifunensine inhibited the binding of EDEM1 and EDEM3 with SEL1L, thus blocking the ubiquitylation of HCV E2 protein. Chemical inhibition of the ERAD pathway neither affected production of the Japanese encephalitis virus (JEV) nor stability of the JEV envelope protein. A co-immunoprecipitation assay showed that EDEM orthologs do not bind with JEV envelope protein. These findings highlight the crucial role of the ERAD pathway in the life cycle of specific viruses.