TMPRSS2 and infection: Furin cleavage occurs during S‐protein biogenesis in acidic compartments of the secretory pathway and enables S‐protein binding to neuropilin 1 via the C terminus of the cleaved S1 domain enhancing infection of epithelial and olfactory neuronal cells low in transmembrane protease serine subtype 2 (TMPRSS2) [17, 18, 19].