Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States.
Department of Microbiology and Immunology, Cornell University, Ithaca, New York 14853, United States.
ACS Infect Dis. 2021 Feb 12;7(2):264-272. doi: 10.1021/acsinfecdis.0c00701. Epub 2021 Jan 12.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses its spike (S) protein to mediate viral entry into host cells. Cleavage of the S protein at the S1/S2 and/or S2' site(s) is associated with viral entry, which can occur at either the cell plasma membrane (early pathway) or the endosomal membrane (late pathway), depending on the cell type. Previous studies show that SARS-CoV-2 has a unique insert at the S1/S2 site that can be cleaved by furin, which appears to expand viral tropism to cells with suitable protease and receptor expression. Here, we utilize viral pseudoparticles and protease inhibitors to study the impact of the S1/S2 cleavage on infectivity. Our results demonstrate that S1/S2 cleavage is essential for early pathway entry into Calu-3 cells, a model lung epithelial cell line, but not for late pathway entry into Vero E6 cells, a model cell line. The S1/S2 cleavage was found to be processed by other proteases beyond furin. Using bioinformatic tools, we also analyze the presence of a furin S1/S2 site in related CoVs and offer thoughts on the origin of the insertion of the furin-like cleavage site in SARS-CoV-2.
严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）利用其刺突（S）蛋白介导病毒进入宿主细胞。S 蛋白在 S1/S2 和/或 S2'位点的裂解与病毒进入有关，这可以发生在细胞膜（早期途径）或内体膜（晚期途径），取决于细胞类型。先前的研究表明，SARS-CoV-2 在 S1/S2 位点具有独特的插入序列，可以被弗林蛋白酶切割，这似乎扩大了病毒对具有合适蛋白酶和受体表达的细胞的嗜性。在这里，我们利用病毒假型和蛋白酶抑制剂来研究 S1/S2 裂解对感染性的影响。我们的结果表明，S1/S2 裂解对于 Calu-3 细胞（一种肺上皮细胞系）的早期途径进入是必不可少的，但对于 Vero E6 细胞（一种模型细胞系）的晚期途径进入则不是必需的。发现 S1/S2 裂解是由弗林蛋白酶以外的其他蛋白酶进行加工的。我们还使用生物信息学工具分析了相关 CoV 中存在的弗林 S1/S2 位点，并就 SARS-CoV-2 中弗林样裂解位点插入的起源提出了一些看法。
