Control of single channel conductance in the outer vestibule of the Kv2.1 potassium channel.
Control of single channel conductance in the outer vestibule of the Kv2.1 potassium channel.
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控制KV2.1钾通道外侧的单个通道电导。
DOI：
10.1085/jgp.200509465
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发表时间：
2006-08
影响因子：
3.8
通讯作者：
Korn, Stephen J
中科院分区：
文献类型：
--
作者：
Trapani, Josef G;Andalib, Payam;Consiglio, Joseph F;Korn, Stephen J
Kv2.1钾通道的电流大小受外源[K+]的调制。与电化学驱动力的变化所预期的行为相反，当细胞外[K+]在生理范围内增加时，通过Kv2.1通道的外向电流变得更大。这种不同寻常的特性背后的机制涉及Kv2.1通道进入两种不同的外部前庭构象之一，这两种构象由它们对茶的敏感性定义。开放为茶敏感构象的通道产生较大的宏观电流，而开放为茶不敏感构象的通道产生较小的宏观电流。在较高的[K+]，更多的通道开放到茶叶敏感的构象。在这篇手稿中，我们研究了构象变化导致电流大小变化的机制。我们首先测试了最简单的假设：每个药物定义的通道构象产生不同的单通道电导，一个更小，一个更大，电流大小的依赖于[K+]的变化反映了开放到两个构象中的通道的百分比依赖于[K+]的变化。利用单通道和宏观记录，以及隐马尔可夫模型，我们能够用这个模型定量地解释宏观电流的[K+]依赖性调节。结合以前发表的工作，这些结果支持一个模型，即外前庭赖氨酸干扰通过通道的K+流量，该赖氨酸定向的依赖于K+的变化通过改变这种干扰的水平来改变单通道电导。此外，这些结果提供了一个单通道电导在传导通路外端被一种机制调制的实验例子，该机制涉及通道激活进入具有不同外部前庭构象的开放状态。
Current magnitude in Kv2.1 potassium channels is modulated by external [K+]. In contrast to behavior expected from the change in electrochemical driving force, outward current through Kv2.1 channels becomes larger when extracellular [K+] is increased within the physiological range. The mechanism that underlies this unusual property involves the opening of Kv2.1 channels into one of two different outer vestibule conformations, which are defined by their sensitivity to TEA. Channels that open into a TEA-sensitive conformation generate larger macroscopic currents, whereas channels that open into a TEA-insensitive conformation generate smaller macroscopic currents. At higher [K+], more channels open into the TEA-sensitive conformation. In this manuscript, we examined the mechanism by which the conformational change produced a change in current magnitude. We started by testing the simplest hypothesis: that each pharmacologically defined channel conformation produces a different single channel conductance, one smaller and one larger, and that the [K+]-dependent change in current magnitude reflects the [K+]-dependent change in the percentage of channels that open into each of the two conformations. Using single channel and macroscopic recordings, as well as hidden Markov modeling, we were able to quantitatively account for [K+]-dependent regulation of macroscopic current with this model. Combined with previously published work, these results support a model whereby an outer vestibule lysine interferes with K+ flux through the channel, and that the [K+]-dependent change in orientation of this lysine alters single channel conductance by changing the level of this interference. Moreover, these results provide an experimental example of single channel conductance being modulated at the outer end of the conduction pathway by a mechanism that involves channel activation into open states with different outer vestibule conformations.