Institute for Infection Medicine, Christian Albrecht University of Kiel, Kiel, Germany.
Infection Biology Unit, German Primate Center, Göttingen, Germany.
J Virol. 2018 Apr 13;92(9). doi: 10.1128/JVI.00013-18. Print 2018 May 1.
Human cytomegalovirus (HCMV) is a widespread human pathogen that causes asymptomatic infection in healthy individuals but poses a serious threat to immunocompromised patients. During the late phase of HCMV infection, the viral capsid is transported to the cytoplasmic viral assembly center (cVAC), where it is enclosed by the tegument protein layer and the viral envelope. The cVAC consists of circularly arranged vesicles from the -Golgi and endosomal networks. The HCMV gene UL35 encodes ppUL35 and its shorter form, ppUL35A. We have previously shown that the UL35 gene is involved in HCMV assembly, but it is unknown how UL35 proteins regulate viral assembly. Here we show that sorting nexin 5 (SNX5), a component of the retromer and part of the retrograde transport pathway, interacts with UL35 proteins. Expression of wild-type proteins but not mutants defective in SNX5 binding resulted in the cellular redistribution of the cation-independent mannose-6-phosphate receptor (CI-M6PR), indicating that UL35 proteins bind and negatively regulate SNX5 to modulate cellular transport pathways. Furthermore, binding of UL35 proteins to SNX5 was required for efficient viral replication and for transport of the most abundant HCMV glycoprotein B (gB; gpUL55) to the cVAC. These results indicate that ppUL35 and ppUL35A control the localization of the essential gB through the regulation of a retrograde transport pathway. Thus, this work is the first to define a molecular interaction between a tegument protein and a vesicular transport factor to regulate glycoprotein localization. Human cytomegalovirus is ubiquitously present in the healthy population, but reactivation or reinfection can cause serious, life-threatening infections in immunocompromised patients. For completion of its lytic cycle, human cytomegalovirus induces formation of an assembly center where mature virus particles are formed from multiple viral proteins. Viral glycoproteins use separate vesicular pathways for transport to the assembly center, which are incompletely understood. Our research identified a viral structural protein which affects the localization of one of the major glycoproteins. We could link this change in glycoprotein localization to an interaction of the structural protein with a cellular protein involved in regulation of vesicle transport. This increases our understanding of how the virus intersects into cellular regulatory pathways to enhance its own replication.
人类巨细胞病毒 (HCMV) 是一种广泛存在的人类病原体，它在健康个体中引起无症状感染，但对免疫功能低下的患者构成严重威胁。在 HCMV 感染的晚期，病毒衣壳被运送到细胞质病毒组装中心 (cVAC)，在那里它被被膜蛋白层和病毒包膜所包围。cVAC 由来自 -高尔基体和内体网络的环状排列的小泡组成。HCMV 基因 UL35 编码 ppUL35 和其较短形式 ppUL35A。我们之前已经表明，UL35 基因参与 HCMV 的组装，但尚不清楚 UL35 蛋白如何调节病毒的组装。在这里，我们表明分选连接蛋白 5 (SNX5)，一种逆行运输途径的组成部分和 retromer 的一部分，与 UL35 蛋白相互作用。野生型蛋白的表达而不是与 SNX5 结合缺陷的突变体的表达导致阳离子非依赖性甘露糖-6-磷酸受体 (CI-M6PR) 的细胞再分布，表明 UL35 蛋白结合并负调控 SNX5 以调节细胞运输途径。此外，UL35 蛋白与 SNX5 的结合对于有效的病毒复制以及将最丰富的 HCMV 糖蛋白 B (gB; gpUL55) 运输到 cVAC 是必需的。这些结果表明，ppUL35 和 ppUL35A 通过调节逆行运输途径来控制必需的 gB 的定位。因此，这项工作首次定义了一种包膜蛋白和一种囊泡运输因子之间的分子相互作用，以调节糖蛋白的定位。人类巨细胞病毒在健康人群中普遍存在，但在免疫功能低下的患者中重新激活或再感染会导致严重的、危及生命的感染。为了完成其裂解周期，人类巨细胞病毒诱导形成一个组装中心，其中成熟的病毒颗粒由多种病毒蛋白形成。病毒糖蛋白使用单独的囊泡途径运输到组装中心，但这一过程尚不完全清楚。我们的研究确定了一种病毒结构蛋白，它影响一种主要糖蛋白的定位。我们可以将糖蛋白定位的这种变化与结构蛋白与参与囊泡运输调节的细胞蛋白之间的相互作用联系起来。这增加了我们对病毒如何与细胞调节途径交叉以增强自身复制的理解。
