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The Ca2+‐activated Cl‐ channel TMEM16A represents the effector pathway for purinergic receptor‐mediated secretion in liver epithelium.
Author(s) -
Dutta Amal Kumar,
Khimji AlKarim,
Dougherty Michael,
Kresge Charles,
Woo Kangmee,
Esser Victoria,
Alpini Gianfranco,
Rockey Don
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.610.16
Subject(s) - purinergic receptor , chloride channel , secretion , apical membrane , chemistry , niflumic acid , extracellular , patch clamp , ussing chamber , channel blocker , membrane potential , microbiology and biotechnology , reversal potential , receptor , biophysics , biochemistry , biology , calcium , membrane , organic chemistry
In the liver, Cl − channels in the apical membrane of biliary epithelial cells (BECs) provide the driving force for biliary secretion. Extracellular nucleotides are important agonists for Ca2+‐activated Cl‐ channel activation. The molecular identity of the Ca2+‐activated Cl‐ channel is unknown. Aim to determine if TMEM16A represents the Ca 2+ ‐activated Cl − channel in BECs. Methods Studies were performed in human, mouse, and rat BECs. Membrane Cl − currents were measured by whole‐cell patch clamp and transepithelial secretion (Isc) by Ussing chamber. Results TMEM16A mRNA was detected by RT‐PCR in all BEC models. In polarized BEC monolayers, addition of ATP to the apical chamber increased Isc. Pre‐incubation with IL‐4 increased TMEM16A expression and was associated with an increase in Isc. The ATP‐stimulated Isc was completely inhibited by the Cl − channel blockers NPPB and niflumic acid, but insensitive to CFTR‐inh172. In single cells, exposure to ATP rapidly increased [Ca 2+ ] i and activated whole‐cell Cl − currents with a reversal potential of 0 mV and outward rectification. Transfection with TMEM16A siRNA significantly decreased TMEM16A expression and inhibited the ATP‐stimulated whole‐cell currents. Conclusion These results demonstrate that TMEM16A is functionally present in BECs and contributes to Ca 2+ ‐activated Cl − secretion in response to extracellular nucleotides. These studies represent the first molecular identification of an alternate, non‐CFTR , Cl − channel in BECs.