title: Pharmacological characterization of TMEM16A currents.
abstract: Recent studies have shown that transmembrane protein 16 A (TMEM16A) is a subunit of calcium-activated chloride channels (CACCs). Pharmacological agents have been used to probe the functional role of CACCs, however their effect on TMEM16A currents has not been systematically investigated. In the present study, we characterized the voltage and concentration-dependent effects of 2 traditional CACC inhibitors (niflumic acid and anthracene-9-carboxcylic acid) and 2 novel CACC / TMEM16A inhibitors (CACC(inh)A01 and T16A(inh)A01) on TMEM16A currents. The whole cell patch clamp technique was used to record TMEM16A currents from HE K 293 cells that stably expressed human TMEM16A. Niflumic acid, A-9-C, CACC(inh)A01 and T16A(inh)A01 inhibited TMEM16A currents with IC50 values of 12, 58, 1.7 and 1.5 μM, respectively, however, A-9-C and niflumic acid were less efficacious at negative membrane potentials. A-9-C and niflumic acid reduced the rate of TMEM16A tail current deactivation at negative membrane potentials and A-9-C (1 mM) enhanced peak TMEM16A tail current amplitude. In contrast, the inhibitory effects of CACC(inh)A01 and T16A(inh)A01 were independent of voltage and they did not prolong the rate of TMEM16A tail current deactivation. The effects of niflumic acid and A-9-C on TMEM16A currents were similar to previous observations on CACCs in vascular smooth muscle, strengthening the hypothesis that they are encoded by TMEM16A. However, CACC(inh)A01 and T16A(inh)A01 were more potent inhibitors of TMEM16A channels and their effects were not diminished at negative membrane potentials making them attractive candidates to interrogate the functional role of TMEM16A channels in future studies.
authors.forename: Eamonn
authors.initials: E
authors.lastname: Bradley
authors.forename: Stephen
authors.initials: S
authors.lastname: Fedigan
authors.forename: Timothy
authors.initials: T
authors.lastname: Webb
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hollywood
authors.forename: Keith D
authors.initials: KD
authors.lastname: Thornbury
authors.forename: Noel G
authors.initials: NG
authors.lastname: McHale
authors.forename: Gerard P
authors.initials: GP
authors.lastname: Sergeant
mesh_terms: D000075369:Anoctamin-1; D000873:Anthracenes / Q000494:pharmacology; D018118:Chloride Channels / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D007700:Kinetics; D009363:Neoplasm Proteins / Q000378:metabolism*; D009544:Niflumic Acid / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011743:Pyrimidines / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: C476213:ANO1 protein, human; D000075369:Anoctamin-1; D000873:Anthracenes; D018118:Chloride Channels; D009363:Neoplasm Proteins; D011743:Pyrimidines; C578466:T16AInh-A01; D013844:Thiazoles; D009544:Niflumic Acid; C034020:anthracene