Hepatitis C virus (HCV) infection is tightly connected to the lipid metabolism with lipid droplets (LDs) serving as assembly sites for progeny virions. A previous LD proteome analysis identified annexin A3 (ANXA3) as an important HCV host factor that is enriched at LDs in infected cells and required for HCV morphogenesis. To further characterize ANXA3 function in HCV, we performed proximity labeling using ANXA3-BioID2 as bait in HCV-infected cells. Two of the top proteins identified proximal to ANXA3 during HCV infection were the La-related protein 1 (LARP1) and the ADP ribosylation factor-like protein 8B (ARL8B), both of which have been previously described to act in HCV particle production. In follow-up experiments, ARL8B functioned as a pro-viral HCV host factor without localizing to LDs and thus likely independent of ANXA3. In contrast, LARP1 interacts with HCV core protein in an RNA-dependent manner and is translocated to LDs by core protein. Knockdown of LARP1 decreased HCV spreading without altering HCV RNA replication or viral titers. Unexpectedly, entry of HCV particles and E1/E2-pseudotyped lentiviral particles was reduced by LARP1 depletion, whereas particle production was not altered. Using a recombinant vesicular stomatitis virus (VSV)ΔG entry assay, we showed that LARP1 depletion also decreased entry of VSV with VSV, MERS, and CHIKV glycoproteins. Therefore, our data expand the role of LARP1 as an HCV host factor that is most prominently involved in the early steps of infection, likely contributing to endocytosis of viral particles through the pleiotropic effect LARP1 has on the cellular translatome.

中文翻译：

---

HCV 感染中宿主因子 ANXA3 的邻近标记揭示了 LARP1 在病毒进入中的新功能


丙型肝炎病毒（HCV）感染与脂质代谢密切相关，脂滴（LD）充当子代病毒颗粒的组装位点。之前的 LD 蛋白质组分析确定膜联蛋白 A3 (ANXA3) 是一种重要的 HCV 宿主因子，它在感染细胞的 LD 处富集，并且是 HCV 形态发生所必需的。为了进一步表征 ANXA3 在 HCV 中的功能，我们使用 ANXA3-BioID2 作为诱饵在 HCV 感染的细胞中进行邻近标记。 HCV 感染过程中与 ANXA3 邻近的两个最重要的蛋白质是 La 相关蛋白 1 (LARP1) 和 ADP 核糖基化因子样蛋白 8B (ARL8B)，之前已描述这两种蛋白在 HCV 颗粒产生中发挥作用。在后续实验中，ARL8B 作为促病毒 HCV 宿主因子发挥作用，而不定位于 LD，因此可能独立于 ANXA3。相反，LARP1以RNA依赖性方式与HCV核心蛋白相互作用，并通过核心蛋白易位至LD。 LARP1 的敲除减少了 HCV 传播，但不改变 HCV RNA 复制或病毒滴度。出乎意料的是，HCV 颗粒和 E1/E2 假型慢病毒颗粒的进入因 LARP1 耗尽而减少，而颗粒的产生却没有改变。使用重组水泡性口炎病毒 (VSV)ΔG 进入测定，我们发现 LARP1 耗尽也减少了 VSV、VSV、MERS 和 CHIKV 糖蛋白的进入。因此，我们的数据扩展了 LARP1 作为 HCV 宿主因子的作用，该因子在感染的早期步骤中最为显着，可能通过 LARP1 对细胞翻译组的多效性作用促进病毒颗粒的内吞作用。