Control of transient, resurgent, and persistent current by open-channel block by Na channel β4 in cultured cerebellar granule neurons
Control of transient, resurgent, and persistent current by open-channel block by Na channel β4 in cultured cerebellar granule neurons
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DOI：
10.1073/pnas.1005633107
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发表时间：
2010-07-06
影响因子：
11.1
通讯作者：
Raman, Indira M.
中科院分区：
文献类型：
--
作者：
Bant, Jason S.;Raman, Indira M.
在几类神经元（包括小脑细胞）中的电压门控Na通道受到内源性蛋白的开放通道阻断和解除阻断。Na-V β 4（Scn 4 b）亚基是一种候选阻断蛋白，因为其胞质尾区的游离肽（β 4肽）可以阻断开放的Na通道，并在通道复极化后解除阻断时诱导复活电流。然而，在异源表达系统中，Na-V β 4不能产生复活电流。因此，我们测试了该亚基在产生复活电流中的必要性，以及其对Na通道门控和动作电位的影响。环，通过研究用针对Scn 4 b的siRNA处理的培养小脑颗粒神经元。定量RT-PCR证实，Scn 4 b的敲除导致5种电生理表型：恢复电流的损失，持续电流的减少，瞬态电流的超极化半失活电压，更高的基强度和重复性降低。戒指所有钠电流的中断。环被β 4肽拯救。最简单的解释是Na-V β 4本身阻断颗粒细胞的Na通道，使该亚基成为负责复活电流的第一个阻断蛋白。结果还表明，一个已知的开放通道阻断肽不仅允许从非导电状态从正电压复极后快速恢复，但也增加了钠通道的可用性在负电位拮抗快速失活。因此，Na-V β 4表达决定了Na通道门控的多个方面，从而调节培养的小脑颗粒细胞的兴奋性。
Voltage-gated Na channels in several classes of neurons, including cells of the cerebellum, are subject to an open-channel block and unblock by an endogenous protein. The Na-V beta 4 (Scn4b) subunit is a candidate blocking protein because a free peptide from its cytoplasmic tail, the beta 4 peptide, can block open Na channels and induce resurgent current as channels unblock upon repolarization. In heterologous expression systems, however, Na-V beta 4 fails to produce resurgent current. We therefore tested the necessity of this subunit in generating resurgent current, as well as its influence on Na channel gating and action potential. ring, by studying cultured cerebellar granule neurons treated with siRNA targeted against Scn4b. Knockdown of Scn4b, confirmed with quantitative RT-PCR, led to five electrophysiological phenotypes: a loss of resurgent current, a reduction of persistent current, a hyperpolarized half-inactivation voltage of transient current, a higher rheobase, and a decrease in repetitive. ring. All disruptions of Na currents and. ring were rescued by the beta 4 peptide. The simplest interpretation is that Na-V beta 4 itself blocks Na channels of granule cells, making this subunit the first blocking protein that is responsible for resurgent current. The results also demonstrate that a known open-channel blocking peptide not only permits a rapid recovery from nonconducting states upon repolarization from positive voltages but also increases Na channel availability at negative potentials by antagonizing fast inactivation. Thus, Na-V beta 4 expression determines multiple aspects of Na channel gating, thereby regulating excitability in cultured cerebellar granule cells.