Schuster A, Lacinová L, Klugbauer N, Ito H, Birnbaumer L, Hofmann F
Institut für Pharmakologie and Toxikologie de TU München, Germany.
EMBO J. 1996 May 15;15(10):2365-70.
The current through the L-type calcium channel is inhibited and stimulated by distinct dihydropyridines at very low concentrations. The molecular determinants for the high affinity block and stimulation were investigated using chimeras between the class C and E calcium channels. Mutation of three amino acids in the last putative transmembrane segment (IVS6) of the alpha1C subunit decreased the affinity for (+)isradipine 100-fold without significantly affecting the basic properties of the expressed channel. Mutation of two of these three amino acids completely abolished the stimulatory effect of the calcium channel agonist Bay K 8644. These mutations only slightly affected the blocking efficacy of mibefradil and the phenylalkylamine devapamil. Three distinct but adjacently located amino acids mediated the high affinity block by devapamil. These results suggest that the IVS6 segment of the alpha1C subunit is critical for the high affinity interaction between the L-type calcium channel and the calcium channel agonist Bay K 8644 and the two antagonists isradipine and devapamil.
在极低浓度下，不同的二氢吡啶对L型钙通道的电流具有抑制和刺激作用。利用C类和E类钙通道之间的嵌合体研究了高亲和力阻断和刺激的分子决定因素。α1C亚基最后一个假定跨膜片段（IVS6）中的三个氨基酸发生突变，使对（+）伊拉地平的亲和力降低了100倍，而对所表达通道的基本特性没有显著影响。这三个氨基酸中的两个发生突变，完全消除了钙通道激动剂Bay K 8644的刺激作用。这些突变仅轻微影响米贝拉地尔和苯烷基胺地伐帕米的阻断效力。三个不同但相邻的氨基酸介导了地伐帕米的高亲和力阻断。这些结果表明，α1C亚基的IVS6片段对于L型钙通道与钙通道激动剂Bay K 8644以及两种拮抗剂伊拉地平与地伐帕米之间的高亲和力相互作用至关重要。
