Intestinal TMEM16A Control Luminal Chloride Secretion in a NHERF1 Dependent Manner

TMEM16A (Transmembrane protein 16A or Anoctamin1) is a calcium-activated chloride channel. (CaCC),that exerts critical roles in epithelial secretion. However, its localization, function, and regulation in intestinal chloride (Cl) secretion remain obscure. Here, we show that TMEM16A protein abundance correlates with Cl secretion in different regions of native intestine activated by the Ca-elevating muscarinic agonist carbachol (CCH). Basal, as well as both cAMP- and CCH-stimulated Isc, was largely reduced in  ± mouse intestine. We found CCH was not able to increase Isc in the presence of apical to serosal Cl gradient, strongly supporting TMEM16A as primarily a luminal Cl channel. Immunostaining demonstrated apical localization of TMEM16A where it colocalized with NHERF1 in mouse colonic tissue. Cellular depletion of NHERF1 in human colonic T84 cells caused a significant reduction of both cAMP- and CCH-stimulated Isc. Immunoprecipitation experiments revealed that NHERF1 forms a complex with TMEM16A through a PDZ-based interaction. We conclude that TMEM16A is a luminal Cl channel in the intestine that functionally interacts with CFTR via PDZ-based interaction of NHERF1 for efficient and specific cholinergic stimulation of intestinal Cl secretion.