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-na TU 

机构地区：[1]Cardio-Electrophysiological Research Laboratory Medical College, Wuhan University of Science and Technology, Wuhan 430081, China [2]Research Center of lon Channelopathy, Department of Cardiology, Institute of Cardiovascular Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China

出　　处：《Acta Pharmacologica Sinica》2007年第7期959-967,共9页中国药理学报（英文版）

基　　金：This work was supported by the National Natural Science Foundation of China(№ 30470711)

摘　　要：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）, and to determine whether mutations in the S6 region ale important for the inhibition of IHERG by verapamil. Methods： HERG channels （WT, Y652A, and F656A） were expressed in oocytes of Xenopus laevis and studied using the 2-electrode voltage-clamp technique. Results： WT HERG is blocked in a concentration-dependent manner by verapamil （half-maximal inhibition concentration [IC50]=5.1 μmol/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 IC50 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. Conclusion： 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.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）, and to determine whether mutations in the S6 region ale important for the inhibition of IHERG by verapamil. Methods： HERG channels （WT, Y652A, and F656A） were expressed in oocytes of Xenopus laevis and studied using the 2-electrode voltage-clamp technique. Results： WT HERG is blocked in a concentration-dependent manner by verapamil （half-maximal inhibition concentration [IC50]=5.1 μmol/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 IC50 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. Conclusion： 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.

关 键 词：VERAPAMIL HERG K^＋ channel voltage clamp 

分 类 号：R972[医药卫生—药品]