NRP1 and infection: In addition, the proprotein convertase furin, which is also present in endothelial cells, can preactivate SARS-CoV-2 particles during infection, and when a conserved C-terminus of the spike protein is exposed after cleavage of the furin-like cleavage sites on this protein, it binds to the receptors Neuropilin-1 and Neuropilin-2, which are also present on these cells, consequently increasing infectivity [9,165].