Evidence suggesting that HCV p7 protects E2 glycoprotein from premature degradation during virus production
Evidence suggesting that HCV p7 protects E2 glycoprotein from premature degradation during virus production
复制标题
DOI：
10.1016/j.virusres.2013.06.008
复制
发表时间：
2013-09-01
期刊：
影响因子：
5
通讯作者：
Russell, Rodney S.
中科院分区：
文献类型：
--
作者：
Atoom, Ali M.;Jones, Daniel M.;Russell, Rodney S.
丙型肝炎病毒（HCV）基因组编码63个氨基酸（aa）的蛋白，p7，其位于结构蛋白和非结构蛋白之间。p7定位于内质网膜，由两个跨膜结构域（TM 1和TM 2）和一个胞质环组成。虽然它的确切作用是未知的，但p7对于细胞培养中感染性病毒的组装和/或释放以及黑猩猩的感染性至关重要。p7对HCV生命周期的贡献可能来自至少两个不同的角色。首先，几项研究表明，p7作为一种离子通道，其功能对感染至关重要。其次，p7与NS 2相互作用的方式，可以调节其他结构蛋白在组装过程中的靶向。在这项研究中，我们观察到TM 1和p7细胞质环的突变降低了单循环病毒生产试验中的感染性病毒生产。细胞内和细胞外病毒滴度的分析表明，p7的功能在一个阶段之前，产生感染性颗粒。这些影响不是由于RNA复制改变，因为没有观察到对NS 3或NS 5A蛋白水平的影响，也不是核心蛋白向脂滴募集改变的结果。同样，这些突变似乎并没有阻止核衣壳寡聚化。重要的是，我们发现，丙氨酸三联体取代，包括两个基本残基的细胞质环，这是必不可少的p7离子通道功能，显着降低E2糖蛋白水平。追踪E2水平的时程实验表明，E2随着时间的推移而降解，而不是以减少的量合成。本研究的结果提供了强有力的证据表明，p7的功能之一是保护丙型肝炎病毒糖蛋白在病毒形态发生过程中过早降解。(C)2013作者Elsevier B. V.出版，保留所有权利。
The hepatitis C virus (HCV) genome encodes a 63 amino acid (aa) protein, p7, which is located between the structural and non-structural proteins. p7 localizes to endoplasmic reticulum membranes and is composed of two transmembrane domains (TM1 and TM2) and a cytoplasmic loop. While its exact role is unknown, p7 is crucial for assembly and/or release of infectious virus production in cell culture, as well as infectivity in chimpanzees. The contribution of p7 to the HCV life cycle may result from at least two distinct roles. Firstly, several studies have shown that p7 acts as an ion channel, the functionality of which is critical for infection. Secondly, p7 interacts with NS2 in a manner that may regulate the targeting of other structural proteins during the assembly process. In this study, we observed that mutations in TM1 and the cytoplasmic loop of p7 decreased infectious virus production in a single-cycle virus production assay. Analysis of intra- and extracellular virus titers indicated that p7 functions at a stage prior to generation of infectious particles. These effects were not due to altered RNA replication since no effects on levels of NS3 or NS5A protein were observed, and were not a consequence of altered recruitment of core protein to lipid droplets. Similarly, these mutations seemingly did not prevent nucleocapsid oligomerization. Importantly, we found that an alanine triplet substitution including the two basic residues of the cytoplasmic loop, which is integral to p7 ion channel function, significantly reduced E2 glycoprotein levels. A time course experiment tracking E2 levels indicated that E2 was degraded over time, as opposed to being synthesized in reduced quantities. The results of this study provide strong evidence that one of the functions of p7 is to protect HCV glycoproteins from premature degradation during virion morphogenesis. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.