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

The most common mutation in the cystic fibrosis transmembrane conductance regulator ( CFTR) gene in individuals with cystic fibrosis, Delta F508, causes retention of Delta F508-CFTR in the endoplasmic reticulum and leads to the absence of CFTR Cl- channels in the apical plasma membrane. Rescue of Delta F508-CFTR by reduced temperature or chemical means reveals that the Delta F508 mutation reduces the half-life of Delta F508-CFTR in the apical plasma membrane. Because Delta F508-CFTR retains some Cl- channel activity, increased expression of \Delta F508-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 Delta F508-CFTR in polarized human airway epithelial cells. Accordingly, the goal of this study was to determine the cellular defects in the trafficking of rescued Delta F508-CFTR that lead to the decreased apical membrane half-life of Delta F508-CFTR in polarized human airway epithelial cells. We report that in polarized human airway epithelial cells (CFBE41o-) the Delta F508 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.