Block of hERG Channels by Berberine: Mechanisms of Voltage- and State-Dependence Probed With Site-Directed Mutant Channels
Block of hERG Channels by Berberine: Mechanisms of Voltage- and State-Dependence Probed With Site-Directed Mutant Channels
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DOI：
10.1097/01.fjc.0000191564.52242.00
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发表时间：
2006-01
影响因子：
3
通讯作者：
Aldo A. Rodríguez-Menchaca;Tania Ferrer-Villada;Jesus Lara;David Fernandez;R. Navarro-Polanco;J. Sánchez-Chapula
中科院分区：
文献类型：
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作者：
Aldo A. Rodríguez-Menchaca;Tania Ferrer-Villada;Jesus Lara;David Fernandez;R. Navarro-Polanco;J. Sánchez-Chapula
小檗碱延长心脏动作电位的持续时间而不影响静息膜电位或动作电位振幅。关于小檗碱是否通过优先阻断延迟整流钾电流的不同组分IKr和ikk来发挥这一作用存在争议。本研究研究了小檗碱对HEK-293细胞和爪蟾卵母细胞中表达的hERG （IKr）和KCNQ1/KCNE1 （IKs）通道的影响。在HEK-293细胞中，小檗碱对hERG的IC50为3.1±0.5 μM，而KCNQ1/KCNE1通道的IC50降低了11±4%。同样，在卵母细胞中，hERG通道比KCNQ1/KCNE1通道（在300 μM处阻滞约20%）对小檗碱更敏感（IC50 = 80±5 μM）。膜去极化使hERG阻滞明显增加。位于S6结构域的Y652或F656的Ala或位于hERG孔螺旋底部的V625的突变降低了对小檗碱阻断的敏感性。一个失活缺陷突变体hERG通道（G628C/S631C）也被小檗碱阻断。综上所述，这些发现表明，小檗碱通过与特异性残基相互作用，优先阻断hERG通道的开放状态，这些残基在之前的报道中对结合更有效的拮抗剂很重要。
Berberine prolongs the duration of cardiac action potentials without affecting resting membrane potential or action potential amplitude. Controversy exists regarding whether berberine exerts this action by preferential block of different components of the delayed rectifying potassium current, IKr and IKs. Here we have studied the effects of berberine on hERG (IKr) and KCNQ1/KCNE1 (IKs) channels expressed in HEK-293 cells and Xenopus oocytes. In HEK-293 cells, the IC50 for berberine was 3.1 ± 0.5 μM on hERG compared with 11 ± 4% decreases on KCNQ1/KCNE1 channels by 100 μM berberine. Likewise in oocytes, hERG channels were more sensitive to block by berberine (IC50 = 80 ± 5 μM) compared with KCNQ1/KCNE1 channels (∼20% block at 300 μM). hERG block was markedly increased by membrane depolarization. Mutation to Ala of Y652 or F656 located on the S6 domain, or V625 located at the base of the pore helix of hERG decreased sensitivity to block by berberine. An inactivation-deficient mutant hERG channel (G628C/S631C) was also blocked by berberine. Together these findings indicate that berberine preferentially blocks the open state of hERG channels by interacting with specific residues that were previously reported to be important for binding of more potent antagonists.