Dual nature of human ACE2 glycosylation in binding to SARS-CoV-2 spike

Binding of the spike protein of SARS-CoV-2 to the human angiotensinconverting enzyme 2 (ACE2) receptor triggers translocation of the virus into cells. Both the ACE2 receptor and the spike protein are heavily glycosylated, including at sites near their binding interface. We built fully glycosylated models of the ACE2 receptor bound to the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. Using atomistic molecular dynamics (MD) simulations, we found that the glycosylation of the human ACE2 receptor contributes substantially to the binding of the virus. Interestingly, the glycans at two glycosylation sites, N90 and N322, have opposite effects on spike protein binding. The glycan at the N90 site partly covers the binding interface of the spike RBD. Therefore, this glycan can interfere with the binding of the spike protein and protect against docking of the virus to the cell. By contrast, the glycan at the N322 site interacts tightly with the RBD of the ACE2-bound spike protein and strengthens the complex. Remarkably, the N322 glycan binds to a conserved region of the spike protein identified previously as a cryptic epitope for a neutralizing antibody. By mapping the glycan binding sites, our MD simulations aid in the targeted development of neutralizing antibodies and SARS-CoV-2 fusion inhibitors.

Automated summary

Glycosylation of the human ACE2 receptor plays a substantial role in the binding of the SARS-CoV-2 virus. Glycans at the N90 and N322 sites have opposite effects on spike protein binding, with the N90 glycan interfering with binding and the N322 glycan strengthening the complex. Additionally, the N322 glycan binds to a conserved region of the spike protein that has been identified as a cryptic epitope for a neutralizing antibody, showing potential for the development of targeted neutralizing antibodies and fusion inhibitors against SARS-CoV-2.