title: TRPC1 regulates calcium-activated chloride channels in salivary gland cells.
abstract: Calcium-activated chloride channel (CaCC) plays an important role in modulating epithelial secretion. It has been suggested that in salivary tissues, sustained fluid secretion is dependent on Ca(2+) influx that activates ion channels such as CaCC to initiate Cl(-) efflux. However direct evidence as well as the molecular identity of the Ca(2+) channel responsible for activating CaCC in salivary tissues is not yet identified. Here we provide evidence that in human salivary cells, an outward rectifying Cl(-) current was activated by increasing [Ca(2+)]i, which was inhibited by the addition of pharmacological agents niflumic acid (NFA), an antagonist of CaCC, or T16Ainh-A01, a specific TMEM16a inhibitor. Addition of thapsigargin (Tg), that induces store-depletion and activates TRPC1-mediated Ca(2+) entry, potentiated the Cl(-) current, which was inhibited by the addition of a non-specific TRPC channel blocker SKF96365 or removal of external Ca(2+). Stimulation with Tg also increased plasma membrane expression of TMEM16a protein, which was also dependent on Ca(2+) entry. Importantly, in salivary cells, TRPC1 silencing, but not that of TRPC3, inhibited CaCC especially upon store depletion. Moreover, primary acinar cells isolated from submandibular gland also showed outward rectifying Cl(-) currents upon increasing [Ca(2+)]i. These Cl(-) currents were again potentiated with the addition of Tg, but inhibited in the presence of T16Ainh-A01. Finally, acinar cells isolated from the submandibular glands of TRPC1 knockout mice showed significant inhibition of the outward Cl(-) currents without decreasing TMEM16a expression. Together the data suggests that Ca(2+) entry via the TRPC1 channels is essential for the activation of CaCC.
authors.affiliation: Department of Basic Sciences, School of Medicine Health Sciences, University of North Dakota, Grand Forks, North Dakota.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Laboratory of Signal Transduction, NIHES, NIH, Research Triangle Park, North Carolina.
authors.forename: Lutz
authors.initials: L
authors.lastname: Birnbaumer
authors.affiliation: Department of Basic Sciences, School of Medicine Health Sciences, University of North Dakota, Grand Forks, North Dakota.
authors.forename: Brij B
authors.initials: BB
authors.lastname: Singh
mesh_terms: D000818:Animals; D000075369:Anoctamin-1; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics*; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors; D009544:Niflumic Acid / Q000008:administration & dosage; D011743:Pyrimidines / Q000008:administration & dosage; D012469:Salivary Glands / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D013844:Thiazoles / Q000008:administration & dosage
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; D018118:Chloride Channels; D009363:Neoplasm Proteins; D011743:Pyrimidines; C578466:T16AInh-A01; D050052:TRPC Cation Channels; D013844:Thiazoles; C096351:transient receptor potential cation channel, subfamily C, member 1; D009544:Niflumic Acid; D002118:Calcium