Along these lines, our data demonstrate that there is no response to the ENaC blocker benzamil in human CF primary airway epithelial cells under unperturbed thin film conditions (Fig. 5) most likely due to near silent ENaC channels under physiological conditions, where cleavage-activation by proteases including CAPs is prevented by endogenous antiproteases44. This evidence concerns the gene CAPS and cystic fibrosis.