期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：1
DOI：10.1073/pnas.2111199119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
The SARS-CoV-2 spike protein is responsible for host receptor recognition, membrane fusion, and viral infection. Understanding the cellular and inhibiting the molecular mechanisms of spike-driven viral entry is a research priority in curbing the ongoing pandemic and preventing future coronavirus outbreaks. Here, we highlight that the generation of SARS-CoV-2 S2′ fragments, a proteolytic event occurring within the S2 subunit, is a molecular switch coupled to membrane fusion. Downstream of host receptor recognition, spike-driven syncytia formation requires the presence of an S2′ cleavage site at arginine 815 but not 685. Hence, the proteolytic processing of spike at the S2′ site upon its engagement of host ACE2 may serve as a potential antiviral target against the current SARS-CoV-2 and related coronavirus strains.
The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has resulted in tremendous loss worldwide. Although viral spike (S) protein binding of angiotensin-converting enzyme 2 (ACE2) has been established, the functional consequences of the initial receptor binding and the stepwise fusion process are not clear. By utilizing a cell–cell fusion system, in complement with a pseudoviral infection model, we found that the spike engagement of ACE2 primed the generation of S2′ fragments in target cells, a key proteolytic event coupled with spike-mediated membrane fusion. Mutagenesis of an S2′ cleavage site at the arginine (R) 815, but not an S2 cleavage site at arginine 685, was sufficient to prevent subsequent syncytia formation and infection in a variety of cell lines and primary cells isolated from human ACE2 knock-in mice. The requirement for S2′ cleavage at the R815 site was also broadly shared by other SARS-CoV-2 spike variants, such as the Alpha, Beta, and Delta variants of concern. Thus, our study highlights an essential role for host receptor engagement and the key residue of spike for proteolytic activation, and uncovers a targetable mechanism for host cell infection by SARS-CoV-2.
