Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, Oregon, USA
Department of Molecular Microbiology and Immunology, Oregon Health and Sciences University, Portland, Oregon, USA.
mBio. 2018 May 8;9(3):e00781-18. doi: 10.1128/mBio.00781-18.
Human cytomegalovirus (HCMV) replicates in many diverse cell types , and entry into different cells involves distinct entry mechanisms and different envelope glycoproteins. HCMV glycoprotein gB is thought to act as the virus fusogen, apparently after being triggered by different gH/gL proteins that bind distinct cellular receptors or entry mediators. A trimer of gH/gL/gO is required for entry into all cell types, and entry into fibroblasts involves trimer binding to platelet-derived growth factor receptor alpha (PDGFRα). HCMV entry into biologically relevant epithelial and endothelial cells and monocyte-macrophages also requires a pentamer, gH/gL complexed with UL128, UL130, and UL131, and there is evidence that the pentamer binds unidentified receptors. We screened an epithelial cell cDNA library and identified the cell surface protein CD147, which increased entry of pentamer-expressing HCMV into HeLa cells but not entry of HCMV that lacked the pentamer. A panel of CD147-specific monoclonal antibodies inhibited HCMV entry into epithelial and endothelial cells, but not entry into fibroblasts. shRNA silencing of CD147 in endothelial cells inhibited HCMV entry but not entry into fibroblasts. CD147 colocalized with HCMV particles on cell surfaces and in endosomes. CD147 also promoted cell-cell fusion induced by expression of pentamer and gB in epithelial cells. However, soluble CD147 did not block HCMV entry and trimer and pentamer did not bind directly to CD147, supporting the hypothesis that CD147 acts indirectly through other proteins. CD147 represents the first HCMV entry mediator that specifically functions to promote entry of pentamer-expressing HCMV into epithelial and endothelial cells. Human cytomegalovirus infects nearly 80% of the world's population and causes significant morbidity and mortality. The current method of treatment involves the use of antiviral agents that are prone to resistance and can be highly toxic to patients; currently, there is no vaccine against HCMV available. HCMV infections involve virus dissemination throughout the body, infecting a wide variety of tissues; however, the mechanism of spread is not well understood, particularly with regard to which cellular proteins are utilized by HCMV to establish infection. This report describes the characterization of a newly identified cellular molecule that affects HCMV entry into epithelial and endothelial cells. These results will lead to a better understanding of HCMV pathogenesis and have implications for the development of future therapeutics.
人类巨细胞病毒 (HCMV) 在多种不同的细胞类型中复制，进入不同的细胞涉及不同的进入机制和不同的包膜糖蛋白。HCMV 糖蛋白 gB 被认为是病毒融合蛋白，显然是在不同的 gH/gL 蛋白触发后，这些蛋白结合不同的细胞受体或进入介质。进入所有细胞类型都需要三聚体 gH/gL/gO，而进入成纤维细胞则需要三聚体与血小板衍生生长因子受体 alpha (PDGFRα) 结合。HCMV 进入生物学上相关的上皮细胞和内皮细胞以及单核细胞-巨噬细胞也需要五聚体，gH/gL 与 UL128、UL130 和 UL131 复合，有证据表明五聚体结合未鉴定的受体。我们筛选了上皮细胞 cDNA 文库，并鉴定了细胞表面蛋白 CD147，它增加了表达五聚体的 HCMV 进入 HeLa 细胞的能力，但不能进入缺乏五聚体的 HCMV。一组 CD147 特异性单克隆抗体抑制了上皮细胞和内皮细胞中的 HCMV 进入，但不能抑制成纤维细胞中的进入。内皮细胞中 CD147 的 shRNA 沉默抑制了 HCMV 的进入，但不能抑制成纤维细胞的进入。CD147 在细胞表面和内体上与 HCMV 颗粒共定位。CD147 还促进了上皮细胞中五聚体和 gB 表达诱导的细胞-细胞融合。然而，可溶性 CD147 不能阻断 HCMV 进入，三聚体和五聚体也不能直接与 CD147 结合，这支持了 CD147 通过其他蛋白间接作用的假说。CD147 是第一个专门促进表达五聚体的 HCMV 进入上皮细胞和内皮细胞的 HCMV 进入介质。人类巨细胞病毒感染了世界上近 80%的人口，导致了严重的发病率和死亡率。目前的治疗方法包括使用抗病毒药物，这些药物容易产生耐药性，并且对患者有高度毒性；目前，尚无针对 HCMV 的疫苗。HCMV 感染涉及病毒在全身的传播，感染了广泛的各种组织；然而，其传播机制尚不清楚，特别是关于 HCMV 利用哪些细胞蛋白来建立感染。本报告描述了一种新鉴定的细胞分子的特征，该分子影响 HCMV 进入上皮细胞和内皮细胞。这些结果将导致对 HCMV 发病机制的更好理解，并对未来治疗方法的发展具有意义。
