Ca2+‐activated Cl− channels (TMEM16A) underlie spontaneous electrical activity in isolated mouse corpus cavernosum smooth muscle cells

• Published in: Physiological reports Vol. 10; no. 22; pp. e15504 - n/a
• Main Authors: Lim, Xin Rui, Drumm, Bernard T., Sergeant, Gerard P., Hollywood, Mark A., Thornbury, Keith D.
• Format: Journal Article
• Language: English
• Published: Oxford John Wiley & Sons, Inc 01-11-2022; Wiley
• Subjects: Antibodies; Bladder; Calcium (intracellular); Calcium (reticular); Calcium channels; corpus cavernosum; Cyclopiazonic acid; Erectile dysfunction; Immunocytochemistry; Inositol 1,4,5-trisphosphate receptors; Muscle contraction; Nifedipine; patch clamp; Penis; Pentobarbital; Phenylephrine; Ryanodine receptors; Sarcoplasmic reticulum; Small intestine; Smooth muscle; Software; Tetracaine; TMEM16A; Europe
• ISSN: 2051-817X
• DOI: 10.14814/phy2.15504

Penile detumescence is maintained by tonic contraction of corpus cavernosum smooth muscle cells (CCSMC), but the underlying mechanisms have not been fully elucidated. The purpose of this study was to characterize the mechanisms underlying activation of TMEM16A Ca2+‐activated Cl− channels in freshly isolated murine CCSMC. Male C57BL/6 mice aged 10–18 weeks were euthanized via intraperitoneal injection of sodium pentobarbital (100 mg.kg−1). Whole‐cell patch clamp, pharmacological, and immunocytochemical experiments were performed on isolated CCSM. Tension measurements were performed in whole tissue. TMEM16A expression in murine corpus cavernosum was confirmed using immunocytochemistry. Isolated CCSMC developed spontaneous transient inward currents (STICs) under voltage clamp and spontaneous transient depolarizations (STDs) in current clamp mode of the whole cell, perforated patch clamp technique. STICs reversed close to the predicted Cl− equilibrium potential and both STICs and STDs were blocked by the TMEM16A channel blockers, Ani9 and CaCC(inh)‐A01. These events were also blocked by GSK7975A (ORAI inhibitor), cyclopiazonic acid (CPA, sarcoplasmic reticulum [SR] Ca2+‐ATPase blocker), tetracaine (RyR blocker), and 2APB (IP3R blocker), suggesting that they were dependent on Ca2+ release from intracellular Ca2+ stores. Nifedipine (L‐type Ca2+ channel blocker) did not affect STICs, but reduced the duration of STDs. Phenylephrine induced transient depolarizations and transient inward currents which were blocked by Ani9. Similarly, phenylephrine induced phasic contractions of intact corpus cavernosum muscle strips and these events were also inhibited by Ani9. This study suggests that contraction of CCSM is regulated by activation of TMEM16A channels and therefore inhibition of these channels could lead to penile erection.
This study suggests a simple model of mechanism of TMEM16A channels activation: Ca2+ influx via CRAC channel; and spontaneous Ca2+ release from the SR, initiated via RyR and possibly propagated via IP3R. Released Ca2+ then activates TMEM16A channels to depolarise membrane potential, thus activating L‐type Ca2+ channels to cause further depolarisation. Adrenergic receptor activation can cause activation of TMEM16A channels through the IP3R pathway.