TMPRSS2 and viral infectious disease: First, we monitored MAPK activation in response to a treatment with His-tagged recombinant spike receptor binding domain (Spike-RBD) in Caco-2 cells, which have high level of ACE2 (Fig S1A), express ADAM17, TMPRSS2 and FURIN (Fig S1B) that were previously described as key players in viral infection, and are highly permissive for SARS-CoV-2 (Zupin et al, 2022) (Fig S1C).