The Human Cytomegalovirus Nonstructural Glycoprotein UL148 Reorganizes the Endoplasmic Reticulum.
The Human Cytomegalovirus Nonstructural Glycoprotein UL148 Reorganizes the Endoplasmic Reticulum.
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人类巨细胞病毒非结构糖蛋白 UL148 重组内质网。
DOI：
10.1128/mbio.02110-19
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发表时间：
2019
期刊：
影响因子：
6.4
通讯作者：
Kamil,JeremyP
中科院分区：
文献类型：
--
作者：
Zhang,Hongbo;Read,Clarissa;Nguyen,ChristopherC;Siddiquey,MohammedNA;Shang,Chaowei;Hall,CameronM;vonEinem,Jens;Kamil,JeremyP
人巨细胞病毒（HCMV）编码内质网（ER）驻留糖蛋白，UL 148，激活未折叠蛋白反应（UPR），但在培养的细胞中病毒复制完全被抑制。因此，其先前在免疫逃避和病毒细胞嗜性的调制中的作用被假设为引起ER应激。在这里，我们表明，UL 148是必要的，足以驱动形成突出的ER衍生结构，平均占5%的感染细胞质。这些结构是UL 148与参与ER质量控制的细胞蛋白质（如HRD 1和EDEM 1）结合的位点。电子显微镜显示，感染野生型而非UL 148缺失型HCMV的细胞显示出明显堆积的致密皱褶ER膜，这些膜与扩张的光滑和部分粗糙ER池相连。在UL 148-绿色荧光蛋白（GFP）融合蛋白的异位表达期间，点状信号在明显结构处积聚。该结构在光漂白后表现出较差的荧光恢复，这表明它们的内容物移动的较差，并且不能有效地与ER的其余部分交换。整合应激反应（ISR）的小分子阻断可防止斑点的形成，导致均匀的网状荧光信号。因此，HCMV感染期间的ISR抑制消除了UL 148和HRD 1聚结成离散结构，这表明UL 148需要ISR来引起ER重组。鉴于UL 148稳定的病毒包膜糖蛋白复合物的受体结合亚基的不成熟形式的重要HCMV感染性，我们的研究结果表明，压力依赖性ER重塑有助于病毒细胞tropis.IMPORTANCEPerturbations内质网（ER）形态发生在感染过程中与各种细胞内病原体和某些遗传性疾病。我们确定，人巨细胞病毒（HCMV）基因产物，UL 148，深刻重组ER感染过程中，并足以做到这一点时，表达自己。我们的研究结果表明，ER的UL 148依赖性重组是HCMV感染细胞的一个突出特征。此外，我们发现，这个病毒诱导的细胞器重塑的例子需要综合应激反应（ISR），一种有助于许多疾病状态的应激适应途径。由于ER重组伴随着UL 148在调节HCMV细胞嗜性和逃避抗病毒免疫反应中的作用，我们的研究结果可能对理解所涉及的机制有影响。此外，我们的研究结果提供了一个基础，利用UL 148作为一种工具，调查细胞器的反应，以应激和识别新的药物靶向ISR。
Human cytomegalovirus (HCMV) encodes an endoplasmic reticulum (ER)-resident glycoprotein, UL148, which activates the unfolded protein response (UPR) but is fully dispensable for viral replication in cultured cells. Hence, its previously ascribed roles in immune evasion and modulation of viral cell tropism are hypothesized to cause ER stress. Here, we show that UL148 is necessary and sufficient to drive the formation of prominent ER-derived structures that on average occupy 5% of the infected cell cytoplasm. The structures are sites where UL148 coalesces with cellular proteins involved in ER quality control, such as HRD1 and EDEM1. Electron microscopy revealed that cells infected with wild-type but notUL148-null HCMV show prominent accumulations of densely packed ruffled ER membranes which connect to distended cisternae of smooth and partially rough ER. During ectopic expression of UL148-green fluorescent protein (GFP) fusion protein, punctate signals traffic to accumulate at conspicuous structures. The structures exhibit poor recovery of fluorescence after photobleaching, which suggests that their contents are poorly mobile and do not efficiently exchange with the rest of the ER. Small-molecule blockade of the integrated stress response (ISR) prevents the formation of puncta, leading to a uniform reticular fluorescent signal. Accordingly, ISR inhibition during HCMV infection abolishes the coalescence of UL148 and HRD1 into discrete structures, which argues that UL148 requires the ISR to cause ER reorganization. Given that UL148 stabilizes immature forms of a receptor binding subunit for a viral envelope glycoprotein complex important for HCMV infectivity, our results imply that stress-dependent ER remodeling contributes to viral cell tropism.IMPORTANCEPerturbations to endoplasmic reticulum (ER) morphology occur during infection with various intracellular pathogens and in certain genetic disorders. We identify that a human cytomegalovirus (HCMV) gene product, UL148, profoundly reorganizes the ER during infection and is sufficient to do so when expressed on its own. Our results reveal that UL148-dependent reorganization of the ER is a prominent feature of HCMV-infected cells. Moreover, we find that this example of virally induced organelle remodeling requires the integrated stress response (ISR), a stress adaptation pathway that contributes to a number of disease states. Since ER reorganization accompanies roles of UL148 in modulation of HCMV cell tropism and in evasion of antiviral immune responses, our results may have implications for understanding the mechanisms involved. Furthermore, our findings provide a basis to utilize UL148 as a tool to investigate organelle responses to stress and to identify novel drugs targeting the ISR.