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Control of Ion Transport by Tmem16a Expressed in Murine Intestine.

ABSTRACT: 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.

SUBMITTER: Kunzelmann K

PROVIDER: S-EPMC6797858 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Control of Ion Transport by Tmem16a Expressed in Murine Intestine.

Kunzelmann Karl K Centeio Raquel R Wanitchakool Podchanart P Cabrita Inês I Benedetto Roberta R Saha Tultul T Hoque Kazi Mirajul KM Schreiber Rainer R

Frontiers in physiology 20191004

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 int ...[more]

PMID: 31680994

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Project description:Recently, overexpression of the genes TMEM16A and TMEM16B has been shown to produce currents qualitatively similar to native Ca(2+)-activated Cl(-) currents (I(ClCa)) in vascular smooth muscle. However, there is no information about this new gene family in vascular smooth muscle, where Cl(-) channels are a major depolarizing mechanism. Qualitatively similar Cl(-) currents were evoked by a pipette solution containing 500 nM Ca(2+) in smooth muscle cells isolated from BALB/c mouse portal vein, thoracic aorta, and carotid artery. Quantitative PCR using SYBR Green chemistry and primers specific for transmembrane protein (TMEM) 16A or the closely related TMEM16B showed TMEM16A expression as follows: portal vein > thoracic aorta > carotid artery > brain. In addition, several alternatively spliced variant transcripts of TMEM16A were detected. In contrast, TMEM16B expression was very low in smooth muscle. Western blot analysis with different antibodies directed against TMEM16A revealed a number of products with a consistent band at ?120 kDa, except portal vein, where an 80-kDa band predominated. TMEM16A protein was identified in the smooth muscle layers of 4-?m-thick slices of portal vein, thoracic aorta, and carotid artery. In isolated myocytes, fluorescence specific to a TMEM16A antibody was detected diffusely throughout the cytoplasm, as well as near the membrane. The same antibody used in Western blot analysis of lysates from vascular tissues also recognized an ?147-kDa mouse TMEM16A-green fluorescent protein (GFP) fusion protein expressed in HEK 293 cells, which correlated to a similar band detected by a GFP antibody. Patch-clamp experiments revealed that I(ClCa) generated by transfection of TMEM16A-GFP in HEK 293 cells displayed remarkable similarities to I(ClCa) recorded in vascular myocytes, including slow kinetics, steep outward rectification, and a response similar to the pharmacological agent niflumic acid. This study shows that TMEM16A expression is robust in murine vascular smooth muscle cells, consolidating the view that this gene is a viable candidate for the native Ca(2+)-activated Cl(-) channel in this cell type.

Dataset Information

Control of Ion Transport by Tmem16a Expressed in Murine Intestine.

Publications

Control of Ion Transport by Tmem16a Expressed in Murine Intestine.

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