title: CFTR and TMEM16A are separate but functionally related Cl- channels.
abstract: Previous reports point out to a functional relationship of the cystic fibrosis transmembrane conductance regulator (CFTR) and Ca(2+) activated Cl(-) channels (CaCC). Recent findings showing that TMEM16A forms the essential part of CaCC, prompted us to examine whether CFTR controls TMEM16A. Inhibition of endogenous CaCC by activation of endogenous CFTR was found in 16HBE human airway epithelial cells, which also express TMEM16A. In contrast, CFBE airway epithelial cells lack of CFTR expression, but express TMEM16A along with other TMEM16-proteins. These cells produce CaCC that is inhibited by overexpression and activation of CFTR. In HEK293 cells coexpressing TMEM16A and CFTR, whole cell currents activated by IMBX and forskolin were significantly reduced when compared with cells expressing CFTR only, while the halide permeability sequence of CFTR was not changed. Expression of TMEM16A, but not of TMEM16F, H or J, produced robust CaCC, which that were inhibited by CaCCinh-A01 and niflumic acid, but not by CFTRinh-172. TMEM16A-currents were attenuated by additional expression of CFTR, and were completely abrogated when additionally expressed CFTR was activated by IBMX and forskolin. On the other hand, CFTR-currents were attenuated by additional expression of TMEM16A. CFTR and TMEM16A were both membrane localized and could be coimmunoprecipitated. Intracellular Ca(2+) signals elicited by receptor-stimulation was not changed during activation of CFTR, while ionophore-induced rise in [Ca(2+)](i) was attenuated after stimulation of CFTR. The data indicate that both CFTR and TMEM16 proteins are separate molecular entities that show functional and molecular interaction.
authors.affiliation: Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, Regensburg, Germany.
authors.forename: Jiraporn
authors.initials: J
authors.lastname: Ousingsawat
authors.forename: Patthara
authors.initials: P
authors.lastname: Kongsuphol
authors.forename: Rainer
authors.initials: R
authors.lastname: Schreiber
authors.forename: Karl
authors.initials: K
authors.lastname: Kunzelmann
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000075369:Anoctamin-1; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018118:Chloride Channels / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D009363:Neoplasm Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; C492109:CLCA1 protein, human; D018118:Chloride Channels; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine