Figure 2. Hypothetical illustration of how SARS-CoV-2 interacts with membrane-bound DPP-4/CD26 to facilitate the entry of the virus into the host cells, for example the epithelial cells of alveoli.

Viral spike glycoprotein can bind to both soluble and membrane-bound receptor. Binding of spike protein to membrane-bound DPP-4 facilitates the viral entry to the target cell. The exact domain of DPP-4 wherein the spike protein occupies, is an open question. Potential interactive residues between DPP-4 and SARS-CoV-2 spike RBD have been shown [11].