Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, United States.
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, United States.
Elife. 2020 Jul 22;9:e58411. doi: 10.7554/eLife.58411.
Fusion of HIV-1 with the membrane of its target cell, an obligate first step in virus infectivity, is mediated by binding of the viral envelope (Env) spike protein to its receptors, CD4 and CCR5/CXCR4, on the cell surface. The process of viral fusion appears to be fast compared with viral egress and has not been visualized by EM. To capture fusion events, the process must be curtailed by trapping Env-receptor binding at an intermediate stage. We have used fusion inhibitors to trap HIV-1 virions attached to target cells by Envs in an extended pre-hairpin intermediate state. Electron tomography revealed HIV-1 virions bound to TZM-bl cells by 2-4 narrow spokes, with slightly more spokes present when evaluated with mutant virions that lacked the Env cytoplasmic tail. These results represent the first direct visualization of the hypothesized pre-hairpin intermediate of HIV-1 Env and improve our understanding of Env-mediated HIV-1 fusion and infection of host cells.
HIV-1 与靶细胞膜融合是病毒感染的必需的第一步，这是由病毒包膜（Env）刺突蛋白与其细胞表面受体 CD4 和 CCR5/CXCR4 的结合介导的。与病毒逸出相比，病毒融合的过程似乎很快，并且尚未通过 EM 可视化。为了捕获融合事件，必须通过在中间阶段捕获Env-受体结合来中断该过程。我们使用融合抑制剂来捕获通过 Env 附着在靶细胞上的 HIV-1 病毒颗粒，这些病毒颗粒处于延长的发夹前中间状态。电子断层扫描显示，HIV-1 病毒颗粒通过 2-4 个狭窄的辐条与 TZM-bl 细胞结合，当用缺乏Env 细胞质尾巴的突变病毒颗粒进行评估时，辐条稍多。这些结果代表了 HIV-1 Env 假设的发夹前中间物的首次直接可视化，并提高了我们对 Env 介导的 HIV-1 融合和宿主细胞感染的理解。
