State-dependent mibefradil block of Na+ channels
State-dependent mibefradil block of Na+ channels
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DOI：
10.1124/mol.66.6.1652
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发表时间：
2004-12-01
影响因子：
3.6
通讯作者：
Hanck, DA
中科院分区：
文献类型：
--
作者：
McNulty, MM;Hanck, DA
米贝拉地尔是一种T型钙通道拮抗剂，据报道与其他类型的离子通道（包括K+、Cl-和Na+通道）具有交叉反应性。使用全细胞电压钳，我们研究了米贝拉地尔阻断人胚肾细胞中表达的四种Na+通道亚型：Na（v）1.5（心脏）、Na（v）1.4（骨骼肌）、Na（v）1.2（脑）和Na（v）1.7（外周神经）。米贝拉地尔阻断Na（v）1.5的使用/频率依赖性的方式，表明优先绑定到国家访问期间去极化。米贝拉地尔以相似的亲和力和对保持电位的依赖性阻断所有Na+通道亚型的电流，并且在去极化电位下减慢药物解离速率（对于Na-v 1.5，k（off）在-130 mV下为0.024/s，在-100 mV下为0.007/ s）。我们进一步探测了米贝拉地尔与失活的Na（v）1.5通道的相互作用。阻滞的程度和时程均不依赖于刺激持续时间，这显著改变了通道在快速失活状态下的驻留时间。此外，抑制快速失活盖（Na-v 1.5 ICM + MTSET）的结合不会改变米贝拉地尔阻滞，证实药物不会优先与快速失活状态相互作用。我们还测试了米贝拉地尔是否与缓慢失活状态相互作用。当用60秒脉冲至-10 mV诱导缓慢失活后选择性地应用于通道时，米贝拉地尔（1 μ M）在Na-v 1.5中产生45%的部分阻断，在缓慢失活更完全的同种型（Na-v 1.4）中产生更大的阻断（88%）。我们的研究结果表明，米贝拉地尔阻断Na+通道的状态依赖性的方式，不依赖于快速失活，但可能涉及与一个或多个缓慢失活状态（S）的相互作用。
Mibefradil is a T-type Ca2+ channel antagonist with reported cross-reactivity with other classes of ion channels, including K+, Cl-, and Na+ channels. Using whole-cell voltage clamp, we examined mibefradil block of four Na+ channel isoforms expressed in human embryonic kidney cells: Na(v)1.5 (cardiac), Na(v)1.4 (skeletal muscle), Na(v)1.2 (brain), and Na(v)1.7 (peripheral nerve). Mibefradil blocked Na(v)1.5 in a use/frequency-dependent manner, indicating preferential binding to states visited during depolarization. Mibefradil blocked currents of all Na+ channel isoforms with similar affinity and a dependence on holding potential, and drug off-rate was slowed at depolarized potentials ( k(off) was 0.024/s at - 130 mV and 0.007/ s at - 100 mV for Na-v 1.5). We further probed the interaction of mibefradil with inactivated Na(v)1.5 channels. Neither the degree nor the time course of block was dependent on the stimulus duration, which dramatically changed the residency time of channels in the fast-inactivated state. In addition, inhibiting the binding of the fast inactivation lid (Na-v 1.5 ICM + MTSET) did not alter mibefradil block, confirming that the drug does not preferentially interact with the fast-inactivated state. We also tested whether mibefradil interacted with slow-inactivated state(s). When selectively applied to channels after inducing slow inactivation with a 60-s pulse to - 10 mV, mibefradil (1 muM) produced 45% fractional block in Na-v 1.5 and greater block (88%) in an isoform (Na-v 1.4) that slow-inactivates more completely. Our results suggest that mibefradil blocks Na+ channels in a state-dependent manner that does not depend on fast inactivation but probably involves interaction with one or more slow-inactivated state(s).