Regulation of human cardiac Kv1.5 channels by extracellular acidification
Regulation of human cardiac Kv1.5 channels by extracellular acidification
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DOI：
10.1007/s00424-016-1890-x
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发表时间：
2016-10
期刊：
影响因子：
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通讯作者：
Shuang Wang;W. Ding;Jia-Yu bai;F. Toyoda;Min Wei;H. Matsuura
中科院分区：
文献类型：
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作者：
Shuang Wang;W. Ding;Jia-Yu bai;F. Toyoda;Min Wei;H. Matsuura
人Kv1.5通道（hKv1.5）传导超快速延迟整流钾电流（IKur），在心房肌细胞动作电位复极过程中起重要作用。本研究采用定点突变结合全细胞膜片钳技术研究了酸性pH对中国仓鼠卵巢（CHO）细胞异源表达的hKv1.5野生型（WT）及其孔突变型通道的影响。细胞外和细胞内的酸化，同样，并减少hKv1.5电流的幅度。细胞外酸化显著地将电流激活的电压依赖性转移到更去极化的电位，并加速电流的失活动力学。已知辅助β亚基Kvβ1.3和Kvβ1.2可改变hKv1.5的药理学敏感性，增强细胞外质子诱导的对hKv1.5电流的抑制作用。此外，几个突变体（T462 C，T479 A，T480 A，和I508 A）表现出显着更高的敏感性，酸性pH诱导的抑制相比，野生型通道，而H463 G突变体的抑制作用显着降低。这些观察结果表明：（1）细胞外酸化改变了hKv1.5的门控和活性;（2）β亚基和几个残基（T462、T479、T480和I508）在决定通道对酸暴露的敏感性方面起关键作用;（3）H463可能是细胞外质子抑制通道的关键传感器。
Human Kv1.5 channels (hKv1.5) conduct the ultra-rapid delayed rectifier potassium current (IKur), which plays an important role in action potential repolarization of atrial myocytes. The present study was undertaken to examine the effects of acidic pH on hKv1.5 wild-type (WT) and its pore mutant channels heterologously expressed in Chinese hamster ovary (CHO) cells using site-directed mutagenesis combined with whole-cell patch-clamp technique. Both extracellular and intracellular acidifications equally and reversely reduced the amplitude of hKv1.5 currents. The extracellular acidification significantly shifted the voltage dependence of current activation to more depolarized potentials and accelerated deactivation kinetics of the current. The ancillary β subunits Kvβ1.3 and Kvβ1.2, known to modify the pharmacological sensitivities of hKv1.5, enhanced the extracellular proton-induced inhibitory effect on hKv1.5 current. In addition, several mutants (T462C, T479A, T480A, and I508A) exhibited significantly higher sensitivity to acidic pH-induced inhibition compared with WT channel, whereas the inhibitory effect of acidic pH was markedly reduced in H463G mutant. These observations indicate that (1) extracellular acidification modifies hKv1.5 gating and activity, (2) β subunits and several residues (T462, T479, T480, and I508) play critical roles in determining the sensitivity of the channel to acidic exposure, and (3) H463 may be a critical sensor for the channel inhibition by extracellular protons.