,Verapamil blocks HERG channel by the helix residue Y652 and F656 in the S6 transmembrane domain

• 作 者: Jing-jing DUAN Ji-hua MA Pei-hua ZHANG Xian-pei WANG An-rou ZOU Dan-ha TU
• 机 构: Cardio-Electrophysiological Research Laboratory Medical College, Wuhan University of Science and Tec
• 出 处: 中国药理学报（英文版）
• 发表日期: 2007年7期
• 关键词: verapamil HERG K+ channel voltage clamp

Aim: The objectives of this study were to investigate the inhibitory action of verapamil on wild-type(WT) and mutation HERG K+ channel current (IHERG), andto determine whether mutations in the S6 region are important for the inhibition ofIHERG by verapamil. Methods: HERG channels (WT, Y652A, and F656A) wereexpressed in oocytes of Xenopus laevis and studied using the 2-electrode volt-age-clamp technique. Results: WT HERG is blocked in a concentration-depen-dent manner by verapamil (half-maximal inhibition concentration [IC50]=5.1 μmol/L),and the steady state activation and inactivation parameters are shifted to morenegative values. However, mutation to Ala of Y652 and F656 located on the S6domain produced 16-fold and 20-fold increases in IC50 for IHERG blockade,respectively. Simultaneously, the steady state activation and inactivation para-meters for Y652A are also shifted to more negative values in the presence of theblockers. Conclusion: Verapamil preferentially binds to and blocks open HERGchannels. Tyr-652 and Phe-656, 2 aromatic amino-acid residues in the inner (S6)helix, are critical in the verapamil-binding site.