Duan Jing-jing, Ma Ji-hua, Zhang Pei-hua, Wang Xian-pei, Zou An-rou, Tu Dan-na
Cardio-Electrophysiological Research Laboratory Medical College, Wuhan University of Science and Technology, Wuhan 430081, China.
Acta Pharmacol Sin. 2007 Jul;28(7):959-67. doi: 10.1111/j.1745-7254.2007.00562.x.
The objectives of this study were to investigate the inhibitory action of verapamil on wild-type(WT) and mutation HERG K+ channel current (I(HERG)), and to determine whether mutations in the S6 region are important for the inhibition of I(HERG) by verapamil.
HERG channels (WT, Y652A, and F656A) were expressed in oocytes of Xenopus laevis and studied using the 2-electrode voltage- clamp technique.
WT HERG is blocked in a concentration-dependent manner by verapamil (half-maximal inhibition concentration [IC(50)]=5.1 micromol/L), and the steady state activation and inactivation parameters are shifted to more negative values. However, mutation to Ala of Y652 and F656 located on the S6 domain produced 16-fold and 20-fold increases in IC(50) for IHERG blockade, respectively. Simultaneously, the steady state activation and inactivation parameters for Y652A are also shifted to more negative values in the presence of the blockers.
Verapamil preferentially binds to and blocks open HERG channels. Tyr-652 and Phe-656, 2 aromatic amino-acid residues in the inner (S6) helix, are critical in the verapamil-binding site.
本研究旨在探究维拉帕米对野生型（WT）和突变型人乙醚 - 去极化相关基因（HERG）钾通道电流（I(HERG)）的抑制作用，并确定S6区域的突变对于维拉帕米抑制I(HERG)是否重要。
将HERG通道（WT、Y652A和F656A）在非洲爪蟾卵母细胞中表达，并使用双电极电压钳技术进行研究。
WT HERG被维拉帕米以浓度依赖性方式阻断（半数最大抑制浓度[IC(50)] = 5.1微摩尔/升），并且稳态激活和失活参数向更负值偏移。然而，位于S6结构域的Y652和F656突变为丙氨酸后，IHERG阻断的IC(50)分别增加了16倍和20倍。同时，在存在阻滞剂的情况下，Y652A的稳态激活和失活参数也向更负值偏移。
维拉帕米优先结合并阻断开放的HERG通道。位于内部（S6）螺旋中的两个芳香族氨基酸残基Tyr - 652和Phe - 656在维拉帕米结合位点中起关键作用。
