Human cytomegalovirus US7, US8, US9, and US10 are cytoplasmic glycoproteins, not found at cell surfaces, and US9 does not mediate cell-to-cell spread
Human cytomegalovirus US7, US8, US9, and US10 are cytoplasmic glycoproteins, not found at cell surfaces, and US9 does not mediate cell-to-cell spread
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DOI：
10.1128/jvi.76.11.5748-5758.2002
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发表时间：
2002-06-01
影响因子：
5.4
通讯作者：
Johnson, DC
中科院分区：
文献类型：
--
作者：
Huber, MT;Tomazin, R;Johnson, DC
人巨细胞病毒（HCMV）表达大量功能未知的膜蛋白。其中一类膜蛋白显然可以使 HCMV 逃避免疫系统的检测。其中最具特征的是在 HCMV 基因组 US2 至 US11 区域编码的糖蛋白，介导对 CD8(+) 和 CD4(+) T 细胞的抗性。 US2、US3、US6 和 US11 阻断主要组织相容性复合体 (MHC) I 类和 II 类抗原呈递途径的各个方面，在细胞质膜中发挥作用，导致 MHC 蛋白保留、降解或错误定位。该区域的远同源基因 US7、US8、US9 和 US10 尚未得到很好的表征。在这里，我们通过使用复制缺陷型腺病毒（Ad）载体报告了 US7 至 US10 编码的糖蛋白的表达。 US7、US9 和 US10 仍然对糖苷内切酶 H 敏感，并且通过共聚焦显微镜测定，它们仅或大部分存在于内质网 (ER) 中。 US8到达高尔基体和跨高尔基体网络并更快地降解。先前的研究表明，US9 可以定位于细胞连接并介导 ARPE-19 视网膜上皮细胞中的细胞间传播。我们在 HEC-1A 上皮细胞的细胞连接处没有发现 US9 的证据。缺乏 US9 的 HCMV 重组体在 ARPE-19 细胞单层上产生较小的噬斑，但与这些细胞中的野生型 HCMV 相比，也表现出病毒复制缺陷。以类似方式构建的能够表达 US9 的其他 HCMV 重组体也产生了小噬斑，其中一些在 ARPE-19 细胞中产生感染性后代时表现出缺陷。因此，细胞间扩散缺陷（噬菌斑大小）与US9表达缺失之间不存在相关性，并且US9（-）突变体可能产生较小的噬菌斑，因为它们产生较少的后代。总之，我们的结果并不支持 US9 在 HCMV 细胞间传播中发挥直接作用的假设。
Human cytomegalovirus (HCMV) expresses a large number of membrane proteins with unknown functions. One class of these membrane proteins apparently acts to allow HCMV to escape detection by the immune system. The best characterized of these are the glycoproteins encoded within the US2 to US11 region of the HCMV genome that mediate resistance to CD8(+) and CD4(+) T cells. US2, US3, US6, and US11 block various aspects of the major histocompatibility complex (MHC) class I and class II antigen presentation pathways, functioning in cytoplasmic membranes to cause retention, degradation, or mislocalization of MHC proteins. Distantly homologous genes in this region, US7, US8, US9, and US10, are not well characterized. Here, we report expression of the glycoproteins encoded by US7 to US10 by using replication-defective adenovirus (Ad) vectors. US7, US9, and US10 remained sensitive to endoglycosidase H and were exclusively or largely present in the endoplasmic reticulum (ER) as determined by confocal microscopy. US8 reached the Golgi apparatus and trans-Golgi network and was more quickly degraded. Previous studies suggested that US9 could localize to cell junctions and mediate cell-to-cell spread in ARPE-19 retinal epithelial cells. We found no evidence of US9 at cell junctions of HEC-1A epithelial cells. HCMV recombinants lacking US9 produced smaller plaques on ARPE-19 cell monolayers but also exhibited defects in virus replication compared with wild-type HCMV in these cells. Other HCMV recombinants constructed in a similar fashion that were able to express US9 also produced small plaques and some of these exhibited defects in production of infectious progeny in ARPE-19 cells. Thus, there was no correlation between defects in cell-to-cell spread (plaque size) and loss of expression of US9, and it is possible that US9(-) mutants produce smaller plaques because they produce fewer progeny. Together, our results do not support the hypothesis that US9 plays a direct role in HCMV cell-to-cell spread.