ABSTRACT
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 Ca2+-elevating muscarinic agonist carbachol (CCH). Basal, as well as both cAMP- and CCH-stimulated Isc, was largely reduced in Ano1 ± 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.
