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Fig. 3 | Animal Diseases

Fig. 3

From: Roles of host proteases in the entry of SARS-CoV-2

Fig. 3

Attachment and entry model of SARS-CoV-2. When SARS-CoV-2 is released by the parental cell, some S is cleaved by host furin. Cleavage by furin facilitates faster binding to the functional receptor ACE2. The binding of ACE2 to S induces a conformational change which exposes the S2’ cleavage site. The presence or absence of TMPRSS2 dictates whether the virus enters through a fast membrane fusion or a slow endosomal route. In the absence of TMPRSS2, the virus is taken into an endosome where the pH will drop, activating cathepsin L. Cathepsin L cleaves S to initiate fusion to the endosomal membrane before release of viral RNA into the cytosol. In the presence of TMPRSS2, the S2’ site is cleaved and the virus can fuse directly to the cell membrane, allowing for a more rapid entry of the viral RNA into the cell

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