The subsequent binding of ACE2 receptor to the spike glycoprotein triggers both the ADAM17-mediated ACE2 shedding and dissociation of S1 fragments by exogenous (furin-related or other) proteases from the spike trimer, which leads on one hand to one S1-ACE2 complex and two S1 free fragments, and on the other hand to fusion of S2 viral trimers and cellular membrane structures, finally producing cell infection. Here, ACE2 is linked to infection.