Blood Systems Research Institute and Department of Laboratory Medicine, University of California, San Francisco, CA, USA.
Virology. 2011 May 10;413(2):265-74. doi: 10.1016/j.virol.2011.02.020. Epub 2011 Mar 23.
Severe acute respiratory syndrome coronavirus (SARS-CoV) poses a considerable threat to human health. Activation of the viral spike (S)-protein by host cell proteases is essential for viral infectivity. However, the cleavage sites in SARS-S and the protease(s) activating SARS-S are incompletely defined. We found that R667 was dispensable for SARS-S-driven virus-cell fusion and for SARS-S-activation by trypsin and cathepsin L in a virus-virus fusion assay. Mutation T760R, which optimizes the minimal furin consensus motif 758-RXXR-762, and furin overexpression augmented SARS-S activity, but did not result in detectable SARS-S cleavage. Finally, SARS-S-driven cell-cell fusion was independent of cathepsin L, a protease essential for virus-cell fusion. Instead, a so far unknown leupeptin-sensitive host cell protease activated cellular SARS-S for fusion with target cells expressing high levels of ACE2. Thus, different host cell proteases activate SARS-S for virus-cell and cell-cell fusion and SARS-S cleavage at R667 and 758-RXXR-762 can be dispensable for SARS-S activation.
严重急性呼吸综合征冠状病毒（SARS-CoV）对人类健康构成了相当大的威胁。病毒刺突（S）-蛋白被宿主细胞蛋白酶激活对于病毒的感染力至关重要。然而，SARS-CoV 的裂解位点和激活 SARS-CoV 的蛋白酶（s）尚未完全确定。我们发现，R667 在病毒-病毒融合试验中对于 SARS-CoV 驱动的病毒-细胞融合和胰蛋白酶及组织蛋白酶 L 激活 SARS-CoV 是可有可无的。优化最小的弗林共识基序 758-RXXR-762 的突变 T760R 和弗林过表达增强了 SARS-CoV 的活性，但不会导致 SARS-CoV 的可检测切割。最后，SARS-CoV 驱动的细胞-细胞融合不依赖于组织蛋白酶 L，组织蛋白酶 L 是病毒-细胞融合所必需的蛋白酶。相反，一种迄今为止未知的亮抑酶肽敏感的宿主细胞蛋白酶激活了细胞表面的 SARS-CoV，使其与表达高水平 ACE2 的靶细胞融合。因此，不同的宿主细胞蛋白酶可以激活 SARS-CoV 进行病毒-细胞和细胞-细胞融合，而 SARS-CoV 在 R667 和 758-RXXR-762 处的切割对于 SARS-CoV 的激活可能是可有可无的。
