FURIN and cystic fibrosis: In accord with what was observed in CF primary hAECs, we found that exposure of Calu-3 cells to P. aeruginosa flagellin significantly increased TMPRSS2 mRNA expression (Figure 2B) in a dose-dependent manner (Supplementary Figure 1) without affecting the transcripts levels of ACE2 (Figure 2C) and FURIN (not illustrated).