2-B-P-097 〇関根 大雅、近藤 るびい、鈴木 良明、山村 寿男 Taiga Sekine, Rubii Kondo, Yoshiaki Suzuki, Hisao Yamamura 名古屋市立大・院薬・細胞分子薬効解析学 Dept. Mol. Cell. Pharmacol., Grad. Sch. Pharmaceut. Sci., Nagoya City Univ. Background
Ca²⁺-activated Cl^- channels are expressed in smooth muscle, endothelial and secretory cells, and are involved in the smooth muscle contraction and cell growth and death. It has been reported that paxilline, a versatile inhibitor of big-conductance Ca²⁺-activated K⁺ (BK_Ca) channels, suppresses Ca²⁺-activated Cl^- current, but the molecular mechanism of this suppression remains unclear. In this study, we focused on TMEM16A, which has been identified as a molecular entity of Ca²⁺-activated Cl^- channels and examined the pharmacological effects of paxilline on the Ca²⁺-activated Cl^- channel TMEM16A.
Method
The whole-cell patch clamp method was applied to HEK293 cells with steady-state expression of TMEM16A channel, and Ca²⁺-activated Cl^- current was measured.
Result
In TMEM16A-HEK293 cells, outward currents slowly activated by depolarization and inward trailing currents activated by repolarization were observed. The pharmacological effects of paxilline on TMEM16A channels were examined and found that 10 mM paxilline significantly suppressed the Ca²⁺-activated Cl^- current constituted by TMEM16A. The activation time constant of the outward current was increased by paxilline. Furthermore, the inhibitory effect of paxilline on TMEM16A channels was concentration dependent.
Summary
It has been shown that paxilline, a general-purpose BK_Ca channel inhibitor, suppresses Ca²⁺-activated Cl^- channels composed of TMEM16A. These findings may lead to the elucidation of the function of the Ca²⁺-activated Cl^- channel TMEM16A and targeted drug discovery.