Program in Virology, Harvard Medical School, Cambridge, Massachusetts, USA.
J Virol. 2013 Mar;87(5):2673-85. doi: 10.1128/JVI.02277-12. Epub 2012 Dec 19.
As an obligate pathogen, influenza virus requires host cell factors and compartments to mediate productive infection and to produce infectious progeny virus. Recently, several small interfering RNA (siRNA) knockdown screens revealed influenza virus host dependency proteins, all of which identified at least two subunits of the coat protein I (COPI) complex. COPI proteins oligomerize to form coated vesicles that transport contents between the Golgi apparatus and the endoplasmic reticulum, and they have also been reported to mediate endosomal trafficking. However, it remains unclear which steps in the influenza virus infection cycle rely on the COPI complex. Upon systematic dissection of the influenza virus infection cycle, from entry to progeny virion production, we found that prolonged exposure to COPI complex disruption through siRNA depletion resulted in significant defects in virus internalization and trafficking to late endosomes. Acute inhibition of COPI complex recruitment to the Golgi apparatus with pharmacological compounds failed to recapitulate the same entry defects as observed with the COPI-depleted cells but did result in specific decreases in viral membrane protein expression and assembly, leading to defects in progeny virion production. Taken together, our findings suggest that COPI complexes likely function indirectly in influenza virus entry but play direct roles in viral membrane protein expression and assembly.
作为一种专性病原体，流感病毒需要宿主细胞因子和区室来介导有效的感染，并产生有感染性的子代病毒。最近，几项小干扰 RNA（siRNA）敲低筛选揭示了流感病毒宿主依赖性蛋白，所有这些蛋白都鉴定出至少两个衣壳蛋白 I（COPI）复合物的亚基。COPI 蛋白寡聚形成有被小泡，在高尔基体和内质网之间运输物质，它们也被报道介导内体运输。然而，在流感病毒感染周期中，哪些步骤依赖于 COPI 复合物仍不清楚。在对流感病毒感染周期进行系统剖析，从进入到子代病毒粒子的产生，我们发现，通过 siRNA 耗竭长时间暴露于 COPI 复合物破坏会导致病毒内化和向晚期内体运输的严重缺陷。用药理学化合物急性抑制 COPI 复合物向高尔基体的募集，未能重现与 COPI 耗竭细胞观察到的相同的进入缺陷，但确实导致病毒膜蛋白表达和组装特异性下降，导致子代病毒粒子产生缺陷。总之，我们的研究结果表明，COPI 复合物可能在流感病毒进入中间接发挥作用，但在病毒膜蛋白表达和组装中直接发挥作用。
