Honoré E, Attali B, Romey G, Heurteaux C, Ricard P, Lesage F, Lazdunski M, Barhanin J
Institut de Pharmacologie Moléculaire et Cellulaire, CNRS, Valbonne, France.
EMBO J. 1991 Oct;10(10):2805-11. doi: 10.1002/j.1460-2075.1991.tb07829.x.
Neonatal mouse cardiac poly(A)+ mRNA microinjection into Xenopus oocytes directed the expression of a delayed rectifier K+ current. A cDNA encoding this channel, called mIsK, was cloned from a neonatal mouse heart cDNA library whose properties were studied after expression of the complementary RNA in Xenopus oocytes. Among the different known K+ channel blockers, only the class III antiarrhythmic clofilium inhibited mIsK in the 10-100 microM range. The channel was completely insensitive to other antiarrhythmics such as quinine, quinidine, sotalol or amiodarone. mIsK was enhanced by increasing intracellular Ca2+ and by microinjected Ca(2+)-calmodulin dependent protein kinase II. These stimulations were reversed by the calmodulin antagonist W7. Conversely, the phorbol ester PMA, the diacylglycerol analog OAG and microinjected purified protein kinase C inhibited mIsK. This inhibitory effect could be prevented by the protein kinase C inhibitor staurosporine. These results were consistent with the presence of consensus sequences for kinase II and kinase C in the mIsK structure. Cultured newborn mouse ventricular cardiac cells exhibited a delayed rectifier K+ current which had biophysical properties similar to those of cloned mIsK and which was inhibited by clofilium and protein kinase C activators. In situ hybridization experiments revealed that mIsK mRNA was homogeneously distributed in the cardiac tissue. Neonatal mouse heart expressed the most mIsK mRNA compared with various other rat and mouse tissues. Since this K+ channel generates a current which appears to be involved in the control of both the action potential duration and the beating rate, these results suggest an important role for the mIsK channel in cardiac cell physiology and cardiac pathology.
将新生小鼠心脏的多聚腺苷酸加尾（poly(A)+）mRNA显微注射到非洲爪蟾卵母细胞中，可指导延迟整流钾电流的表达。从新生小鼠心脏cDNA文库中克隆出编码该通道的cDNA，命名为mIsK，在将其互补RNA在非洲爪蟾卵母细胞中表达后研究了其特性。在不同已知的钾通道阻滞剂中，只有Ⅲ类抗心律失常药氯非铵在10 - 100微摩尔范围内抑制mIsK。该通道对其他抗心律失常药如奎宁、奎尼丁、索他洛尔或胺碘酮完全不敏感。mIsK可通过增加细胞内钙离子浓度以及显微注射钙调蛋白依赖性蛋白激酶II来增强。这些刺激作用可被钙调蛋白拮抗剂W7逆转。相反，佛波酯PMA、二酰基甘油类似物OAG以及显微注射的纯化蛋白激酶C可抑制mIsK。这种抑制作用可被蛋白激酶C抑制剂星形孢菌素阻止。这些结果与mIsK结构中存在激酶II和激酶C的共有序列一致。培养的新生小鼠心室心肌细胞表现出一种延迟整流钾电流，其生物物理特性与克隆的mIsK相似，且被氯非铵和蛋白激酶C激活剂抑制。原位杂交实验表明，mIsK mRNA在心脏组织中均匀分布。与其他各种大鼠和小鼠组织相比，新生小鼠心脏中mIsK mRNA的表达量最高。由于这种钾通道产生的电流似乎参与了动作电位时程和心率的控制，这些结果提示mIsK通道在心肌细胞生理学和心脏病理学中具有重要作用。
