Direct interactions between EN aC gamma subunit and Cl CN 2 in cystic fibrosis epithelial cells

Cystic fibrosis ( CF ) is a lethal disease caused by mutations in the chloride channel CFTR gene. The disease is characterized by decreased chloride secretion and unregulated sodium absorption through the epithelial sodium channel ( EN aC) in the airway epithelium and other affected organs. We hypothesize that a non‐ CFTR alternative chloride channel Cl CN 2 can be activated to negatively regulate EN aC in CF epithelial cell cultures. We identified a novel interaction between Cl CN 2 and the EN aC γ subunit in CF airway epithelial cells and show that the upregulation of Cl CN 2 leads to decreased expression of EN aC γ via a K63 ubiquitination mechanism. These regulatory effects of Cl CN 2 on EN aC γ appear to be dependent on the CBS ‐1 domain located within the c‐terminus of Cl CN 2, which is necessary for the targeting of Cl CN 2 to the apical surface. In sum, these results suggest the ability of Cl CN 2 to negatively regulate sodium absorption through EN aC, supporting its role as a therapeutic target for the treatment of CF .