Abstract
The spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important target for vaccine and drug development. However, the rapid emergence of variant strains with mutated S proteins has rendered many treatments ineffective. Cleavage of the S protein by host proteases is essential for viral infection. Here, we discovered that the S protein contains two previously unidentified Cathepsin L (CTSL) cleavage sites (CS-1 and CS-2). Both sites are highly conserved among all known SARS-CoV-2 variants. Our structural studies revealed that CTSL cleavage promoted S to adopt receptor-binding domain (RBD) “up” activated conformations, facilitating receptor-binding and membrane fusion. We confirmed that CTSL cleavage is essential during infection of all emerged SARS-CoV-2 variants (including the recently emerged Omicron variant) by pseudovirus (PsV) infection experiment. Furthermore, we found CTSL-specific inhibitors not only blocked infection of PsV/live virus in cells but also reduced live virus infection of ex vivo lung tissues of both human donors and human ACE2-transgenic mice. Finally, we showed that two CTSL-specific inhibitors exhibited excellent In vivo effects to prevent live virus infection in human ACE2-transgenic mice. Our work demonstrated that inhibition of CTSL cleavage of SARS-CoV-2 S protein is a promising approach for the development of future mutation-resistant therapy.
【초록키워드】 Treatment, SARS-CoV-2, viral infection, Vaccine, coronavirus, therapy, S protein, variant, SARS-CoV-2 variant, Infection, omicron, virus, CTSL, Protein, SARS-CoV-2 variants, pseudovirus, mice, RBD, membrane fusion, experiment, inhibitor, Live virus, SARS-CoV-2 S protein, cathepsin, conformations, strain, Ex vivo, acute respiratory syndrome, domain, lung tissue, host protease, cleavage site, Effect, approach, Prevent, Cell, blocked, conserved, reduced, exhibited, activated, demonstrated, mutated, the S protein, promoted, CTSL cleavage, human donor, 【제목키워드】 viral infection, SARS-CoV-2 spike protein, novel, mechanism, treatment strategy, cleavage site,