Anoctamins support calcium-dependent chloride secretion by facilitating calcium signaling in adult mouse intestine

Intestinal epithelial electrolyte secretion is activated by increase in intracellular cAMP or Ca2+ and opening of apical Cl− channels. In infants and young animals, but not in adults, Ca2+-activated chloride channels may cause secretory diarrhea during rotavirus infection. While detailed knowledge exists concerning the contribution of cAMP-activated cystic fibrosis transmembrane conductance regulator (CFTR) channels, analysis of the role of Ca2+-dependent Cl− channels became possible through identification of the anoctamin (TMEM16) family of proteins. We demonstrate expression of several anoctamin paralogues in mouse small and large intestines. Using intestinal-specific mouse knockout models for anoctamin 1 (Ano1) and anoctamin 10 (Ano10) and a conventional knockout model for anoctamin 6 (Ano6), we demonstrate the role of anoctamins for Ca2+-dependent Cl− secretion induced by the muscarinic agonist carbachol (CCH). Ano1 is preferentially expressed in the ileum and large intestine, where it supports Ca2+-activated Cl− secretion. In contrast, Ano10 is essential for Ca2+-dependent Cl− secretion in jejunum, where expression of Ano1 was not detected. Although broadly expressed, Ano6 has no role in intestinal cholinergic Cl− secretion. Ano1 is located in a basolateral compartment/membrane rather than in the apical membrane, where it supports CCH-induced Ca2+ increase, while the essential and possibly only apical Cl− channel is CFTR. These results define a new role of Ano1 for intestinal Ca2+-dependent Cl− secretion and demonstrate for the first time a contribution of Ano10 to intestinal transport.