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9‐Phenanthrol inhibits recombinant and arterial myocyte TMEM 16 A channels
Author(s) -
Burris Sarah K,
Wang Qian,
Bulley Simon,
Neeb Zachary P,
Jaggar Jonathan H
Publication year - 2015
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.13077
Subject(s) - depolarization , transient receptor potential channel , myocyte , patch clamp , biophysics , membrane potential , ion channel , channel blocker , chemistry , vascular smooth muscle , activator (genetics) , medicine , biochemistry , microbiology and biotechnology , receptor , biology , smooth muscle , calcium , organic chemistry
Background and Purpose In arterial smooth muscle cells (myocytes), intravascular pressure stimulates membrane depolarization and vasoconstriction (the myogenic response). Ion channels proposed to mediate pressure‐induced depolarization include several transient receptor potential ( TRP ) channels, including TRPM 4, and transmembrane protein 16 A ( TMEM 16 A ), a Ca 2+ ‐activated Cl − channel (CaCC). 9‐Phenanthrol, a putative selective TRPM 4 channel inhibitor, abolishes myogenic tone in cerebral arteries, suggesting that either TRPM 4 is essential for pressure‐induced depolarization, upstream of activation of other ion channels or that 9‐phenanthrol is non‐selective. Here, we tested the hypothesis that 9‐phenanthrol is also a TMEM 16 A channel blocker, an ion channel for which few inhibitors have been identified. Experimental Approach Patch clamp electrophysiology was used to measure rat cerebral artery myocyte and human recombinant TMEM 16 A ( rTMEM 16 A ) currents or currents generated by recombinant bestrophin‐1, another Ca 2+ ‐activated Cl − channel, expressed in HEK 293 cells. Key Results 9‐Phenanthrol blocked myocyte TMEM 16 A currents activated by either intracellular Ca 2+ or E act , a TMEM 16 A channel activator. In contrast, 9‐phenanthrol did not alter recombinant bestrophin‐1 currents. 9‐Phenanthrol reduced arterial myocyte TMEM 16 A currents with an IC 50 of ∼12 μM. Cell‐attached patch recordings indicated that 9‐phenanthrol reduced single rTMEM 16 A channel open probability and mean open time, and increased mean closed time without affecting the amplitude. Conclusions and Implications These data identify 9‐phenanthrol as a novel TMEM 16 A channel blocker and provide an explanation for the previous observation that 9‐phenanthrol abolishes myogenic tone when both TRPM 4 and TMEM 16 A channels contribute to this response. 9‐Phenanthrol may be a promising candidate from which to develop TMEM 16 A channel‐specific inhibitors.