Heinrich Pette Institute, Leibniz Institute for Experimental Virology, 20251 Hamburg, Germany.
Heinrich Pette Institute, Leibniz Institute for Experimental Virology, 20251 Hamburg, Germany
J Cell Sci. 2019 Jan 9;132(1):jcs217042. doi: 10.1242/jcs.217042.
In hepatocytes, PLIN2 is the major protein coating lipid droplets (LDs), an organelle the hepatitis C virus (HCV) hijacks for virion morphogenesis. We investigated the consequences of PLIN2 deficiency on LDs and on HCV infection. Knockdown of PLIN2 did not affect LD homeostasis, likely due to compensation by PLIN3, but severely impaired HCV particle production. PLIN2-knockdown cells had slightly larger LDs with altered protein composition, enhanced local lipase activity and higher β-oxidation capacity. Electron micrographs showed that, after PLIN2 knockdown, LDs and HCV-induced vesicular structures were tightly surrounded by ER-derived double-membrane sacs. Strikingly, the LD access for HCV core and NS5A proteins was restricted in PLIN2-deficient cells, which correlated with reduced formation of intracellular HCV particles that were less infectious and of higher density, indicating defects in maturation. PLIN2 depletion also reduced protein levels and secretion of ApoE due to lysosomal degradation, but did not affect the density of ApoE-containing lipoproteins. However, ApoE overexpression in PLIN2-deficient cells did not restore HCV spreading. Thus, PLIN2 expression is required for trafficking of core and NS5A proteins to LDs, and for formation of functional low-density HCV particles prior to ApoE incorporation.This article has an associated First Person interview with the first author of the paper.
在肝细胞中,PLIN2 是主要的脂滴(LDs)包被蛋白,HCV 病毒利用 LDs 进行病毒形态发生。我们研究了 PLIN2 缺乏对 LDs 和 HCV 感染的影响。PLIN2 的敲低不影响 LD 稳态,可能是由于 PLIN3 的代偿,但严重损害了 HCV 颗粒的产生。PLIN2 敲低的细胞的 LD 稍大,蛋白组成改变,局部脂肪酶活性增强,β-氧化能力提高。电子显微镜显示,PLIN2 敲低后,LD 和 HCV 诱导的囊泡结构被 ER 衍生的双层囊紧紧包围。引人注目的是,在 PLIN2 缺陷细胞中,HCV 核心和 NS5A 蛋白进入 LD 的通道受到限制,这与细胞内 HCV 颗粒形成减少相关,这些颗粒的感染性较低,密度较高,表明成熟缺陷。PLIN2 耗竭还通过溶酶体降解降低了 ApoE 的蛋白水平和分泌,但不影响 ApoE 含量脂蛋白的密度。然而,在 PLIN2 缺陷细胞中过表达 ApoE 并不能恢复 HCV 的扩散。因此,PLIN2 表达对于核心和 NS5A 蛋白向 LD 的运输以及 ApoE 掺入之前功能性低密度 HCV 颗粒的形成是必需的。本文有该论文第一作者的相关第一人称采访。