Control of Ion Transport by Tmem16a Expressed in Murine Intestine

Cl^- secretion by the human and murine intestinal epithelium occurs through the cystic fibrosis transmembrane conductance regulator (cftr). However, the Ca²⁺ activated Cl^- channel Tmem16a was shown to contribute to Cl^- secretion, mainly, but not exclusively, as a basolaterally located Cl^- channel that controls basolateral Ca²⁺ signaling, and thus activation of basolateral Ca²⁺ dependent Sk4 K⁺ channels. In intestinal goblet cells, Tmem16a was shown to regulated Ca²⁺ signals required for exocytosis of mucus. Because a recent report denied the existence and functional role of Tmem16a in murine intestine, we reexamined in detail expression of mRNA and protein for Tmem16a in mouse colon. In experiments using short-circuited Ussing chamber and whole cell patch-clamp techniques, we further compared ion transport in wild type (WT) colon with that in mice with intestinal epithelial specific knockout of Tmem16a. As reported earlier we fully confirm expression of Tmem16a in colonic epithelial cells and the role of Tmem16a for both Ca²⁺-dependent and cAMP-regulated ion secretion.