Division of Gastroenterology, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, United States of America.
PLoS Pathog. 2013;9(8):e1003513. doi: 10.1371/journal.ppat.1003513. Epub 2013 Aug 1.
Hepatitis C virus (HCV) is a single-stranded RNA virus that replicates on endoplasmic reticulum-derived membranes. HCV particle assembly is dependent on the association of core protein with cellular lipid droplets (LDs). However, it remains uncertain whether HCV assembly occurs at the LD membrane itself or at closely associated ER membranes. Furthermore, it is not known how the HCV replication complex and progeny genomes physically associate with the presumed sites of virion assembly at or near LDs. Using an unbiased proteomic strategy, we have found that Rab18 interacts with the HCV nonstructural protein NS5A. Rab18 associates with LDs and is believed to promote physical interaction between LDs and ER membranes. Active (GTP-bound) forms of Rab18 bind more strongly to NS5A than a constitutively GDP-bound mutant. NS5A colocalizes with Rab18-positive LDs in HCV-infected cells, and Rab18 appears to promote the physical association of NS5A and other replicase components with LDs. Modulation of Rab18 affects genome replication and possibly also the production of infectious virions. Our results support a model in which specific interactions between viral and cellular proteins may promote the physical interaction between membranous HCV replication foci and lipid droplets.
丙型肝炎病毒（HCV）是一种单链 RNA 病毒，在内质网衍生的膜上复制。HCV 粒子的组装依赖于核心蛋白与细胞脂滴（LDs）的结合。然而，目前仍不确定 HCV 组装是发生在 LD 膜本身还是在紧密相关的内质网膜上。此外，尚不清楚 HCV 复制复合物和子代基因组如何与假定的病毒组装部位在 LD 处或附近物理关联。我们使用一种无偏的蛋白质组学策略发现 Rab18 与 HCV 非结构蛋白 NS5A 相互作用。Rab18 与 LDs 相关联，被认为促进 LDs 和内质网膜之间的物理相互作用。活性（GTP 结合）形式的 Rab18 比组成型 GDP 结合突变体更强烈地结合 NS5A。在 HCV 感染的细胞中，NS5A 与 Rab18 阳性 LDs 共定位，并且 Rab18 似乎促进 NS5A 和其他复制酶成分与 LDs 的物理关联。Rab18 的调节会影响基因组复制，可能还会影响传染性病毒粒子的产生。我们的结果支持这样一种模型，即病毒和细胞蛋白之间的特定相互作用可能促进膜性 HCV 复制焦点与脂滴之间的物理相互作用。
