The Short Apical Membrane Half-life of Rescued ΔF508-Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Results from Accelerated Endocytosis of ΔF508-CFTR in Polarized Human Airway Epithelial Cells

Abstract The most common mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in individuals with cystic fibrosis, ΔF508, causes retention of ΔF508-CFTR in the endoplasmic reticulum and leads to the absence of CFTR Cl- channels in the apical plasma membrane. Rescue of ΔF508-CFTR by reduced temperature or chemical means reveals that the ΔF508 mutation reduces the half-life of ΔF508-CFTR in the apical plasma membrane. Because ΔF508-CFTR retains some Cl- channel activity, increased expression of ΔF508-CFTR in the apical membrane could serve as a potential therapeutic approach for cystic fibrosis. However, little is known about the mechanisms responsible for the short apical membrane half-life of ΔF508-CFTR in polarized human airway epithelial cells. Accordingly, the goal of this study was to determine the cellular defects in the trafficking of rescued ΔF508-CFTR that lead to the decreased apical membrane half-life of ΔF508-CFTR in polarized human airway epithelial cells. We report that in polarized human airway epithelial cells (CFBE41o-) the ΔF508 mutation increased endocytosis of CFTR from the apical membrane without causing a global endocytic defect or affecting the endocytic recycling of CFTR in the Rab11a-specific apical recycling compartment.