Heart and Circulatory Physiology

TMEM16A channels generate Ca2+-activated Cl currents in cerebral artery smooth muscle cells

Candice Thomas-Gatewood, Zachary P. Neeb, Simon Bulley, Adebowale Adebiyi, John P. Bannister, M. Dennis Leo, Jonathan H. Jaggar


Transmembrane protein (TMEM)16A channels are recently discovered membrane proteins that display electrophysiological properties similar to classic Ca2+-activated Cl (ClCa) channels in native cells. The molecular identity of proteins that generate ClCa currents in smooth muscle cells (SMCs) of resistance-size arteries is unclear. Similarly, whether cerebral artery SMCs generate ClCa currents is controversial. Here, using molecular biology and patch-clamp electrophysiology, we examined TMEM16A channel expression and characterized Cl currents in arterial SMCs of resistance-size rat cerebral arteries. RT-PCR amplified transcripts for TMEM16A but not TMEM16B–TMEM16H, TMEM16J, or TMEM16K family members in isolated pure cerebral artery SMCs. Western blot analysis using an antibody that recognized recombinant (r)TMEM16A channels detected TMEM16A protein in cerebral artery lysates. Arterial surface biotinylation and immunofluorescence indicated that TMEM16A channels are located primarily within the arterial SMC plasma membrane. Whole cell ClCa currents in arterial SMCs displayed properties similar to those generated by rTMEM16A channels, including Ca2+ dependence, current-voltage relationship linearization by an elevation in intracellular Ca2+ concentration, a Nerstian shift in reversal potential induced by reducing the extracellular Cl concentration, and a negative reversal potential shift when substituting extracellular I for Cl. A pore-targeting TMEM16A antibody similarly inhibited both arterial SMC ClCa and rTMEM16A currents. TMEM16A knockdown using small interfering RNA also inhibited arterial SMC ClCa currents. In summary, these data indicate that TMEM16A channels are expressed, insert into the plasma membrane, and generate ClCa currents in cerebral artery SMCs.

  • arterial smooth muscle
  • transmembrane protein 16A
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