TMPRSS2 and infection: TMPRSS2 is a key protease for the entry of SARS-CoV-2 into cells, and TMPRSS2 is able to cleave the SARS-CoV-2 spike protein to initiate virus invasion and infection of cells (Hoffmann et al., 2020; Zhang et al., 2020; Kishimoto et al., 2021).