Setting the stage for molecular dissection of the regulatory components of BK channels.
Setting the stage for molecular dissection of the regulatory components of BK channels.
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DOI：
10.1085/jgp.20028689
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发表时间：
2002-09
期刊：
影响因子：
--
通讯作者：
Lingle CJ
中科院分区：
文献类型：
--
作者：
Lingle CJ
尽管在不同组织中大电导率、钙和电压激活的K+通道（也称为“BK”或“maxi-K”通道）的性质存在显著差异（McManus，1991; Vergara等人，1998），所有BK通道的定义特征是它们的激活由两个独立的生理刺激（膜电压和胞质Ca 2+浓度（[Ca 2 +] i））控制。这种由Ca 2+和电压的双重调节使得BK通道在细胞兴奋性的调节中比严格的电压门控K+通道同系物发挥更动态的作用，因为在任何特定去极化期间的激活程度也与[Ca 2 +] i有关。自从BK通道被首次发现以来，这种双重调节自然吸引了那些对通道门控机制感兴趣的人，提出了一个迷人的问题：两个独立刺激各自影响BK通道开放能力的分子机制是什么？先验的人可能会想象任何一种机制，通过这些机制，两种不同的刺激可以调节通道的激活。在这方面，最早提出的一个建议是，Ca 2+结合本身可能是电压依赖性的（Moczydlowski和Latorre，1983）。或者（但不完全），Ca 2+和电压依赖性步骤可能各自独立地起作用以促进通道激活，Ca 2+结合可能直接影响电压传感器平衡或Ca 2+可能仅在电压传感器移动后发挥其作用。在过去的5年里，有一系列实质性的论文，累积阐明了钙离子和电压调节BK通道的潜在机制。令人欣慰的是，一个共同的主题渗透到这项工作中，无论BK通道门控是用单通道（Rothberg和Magleby，1999，2000）还是宏观电流（考克斯等人，1997; Cui等人，1997），或者是否已经使用辅助性β亚基（考克斯和奥尔德里奇，2000; Nimigean和Magleby，2000）、突变（崔和奥尔德里奇，2000）、Mg 2+（石和崔，2001;张等人，2001）、Ca 2+（Rothberg和Magleby，1999;考克斯和Aldrich，2000）、电压（Horrigan和Aldrich，1999; Horrigan等人，1999），或Ca 2+和电压两者（Rothberg和Magleby，2000）。所有这些文件都有助于认为，电压和Ca 2+调节变构BK通道激活独立影响能量的通道开放。然而，尽管这一不断发展的共识，一些重要的问题与钙离子和电压之间的变构耦合仍然没有得到解决。现在，在本期《普通生理学杂志》上发表的一项引人注目的研究中，Horrigan和Aldrich（2002）提出了这一研究路径的重要延伸。具体来说，他们解决了这样一个问题：“Ca 2+对BK通道激活的变构效应是否通过对电压传感器激活、通道开放或两者的影响而发生”？通过使用门控电流和离子电流测量，他们的工作提供了一个更直接的测试变构机制和配体结合和电压门控之间的联系比以前的工作。从他们的工作中得出的结论是，Ca 2+和电压独立地调节通道开放，并且Ca 2+结合和电压传感器运动之间的相互作用是次要的。这一结论是通过巧妙的分析方法和技术上具有挑战性的实验相结合而得出的，这些实验允许在独立阐明电压传感器运动与Ca 2+依赖性通道激活的条件下详细定义离子和门控电流。
Despite remarkable diversity in the properties of largeconductance, calcium-and voltage-activated K+ channels (also termed “BK” or “maxi-K” channels) in different tissues,(McManus, 1991; Vergara et al., 1998), the defining characteristic of all BK channels is that their activation is controlled by two independent physiological stimuli, membrane voltage and cytosolic Ca2+ concentrations ([Ca2+] i). This dual regulation by Ca2+ and voltage allows BK channels to play a more dynamic role in the regulation of cellular excitability than is possible with strictly voltage-gated K+ channel homologues, as the extent of activation during any particular depolarization is also linked to [Ca2+] i. Since the initial discovery of BK channels, this dual regulation has naturally tantalized those interested in channel gating mechanisms, posing the fascinating question: what is the molecular mechanism by which two independent stimuli each influence the ability of the BK channel to open? A priori one might imagine any of a number of mechanisms by which two distinct stimuli can regulate activation of a channel. One of the earliest proposals in this regard suggested that Ca2+ binding itself could be voltage-dependent (Moczydlowski and Latorre, 1983). Alternatively (but not exhaustively), Ca2+ and voltagedependent steps might each act independently to promote channel activation, Ca2+ binding might directly influence the voltage-sensor equilibrium or Ca2+ might only exert its effect after movement of the voltage sensors. In the last 5 yr, there have been a stream of substantive papers that cumulatively have illuminated the mechanisms underlying regulation of BK channels by Ca2+ and voltage. Gratifyingly, a common theme permeates this work, whether BK channel gating has been studied with single channels (Rothberg and Magleby, 1999, 2000) or macroscopic currents (Cox et al., 1997; Cui et al., 1997), or whether gating has been probed using auxiliary ß subunits (Cox and Aldrich, 2000; Nimigean and Magleby, 2000), mutations (Cui and Aldrich, 2000), Mg2+(Shi and Cui, 2001; Zhang et al., 2001), Ca2+(Rothberg and Magleby, 1999; Cox and Aldrich, 2000), voltage (Horrigan and Aldrich, 1999; Horrigan et al., 1999), or both Ca2+ and voltage (Rothberg and Magleby, 2000). All of these papers have contributed to the view that voltage and Ca2+ regulate allosterically BK channel activation by independently influencing the energetics of channel opening. Yet, despite this evolving consensus, several important questions concerned with allosteric coupling between Ca2+ and voltage remain unresolved. Now in a compelling study in this issue of the Journal of General Physiology, Horrigan and Aldrich (2002) present an important extension of this path of investigation. Specifically, they address the question:“Does the allosteric effect of Ca2+ on BK channel activation occur via effects on voltage-sensor activation, channel opening, or both”? By using both gating current and ion current measurements, their work provides a more direct test of the allosteric mechanism and the linkage between ligand-binding and voltage-gating than in previous work. The conclusion from their work is that Ca2+ and voltage independently act to regulate channel opening, and that the interaction between Ca2+ binding and voltage-sensor movement is minor. This conclusion is reached through a combination of clever analytic methods and technically challenging experiments that allow detailed definition of the ionic and gating currents under conditions that independently illuminate voltage-sensor movement versus Ca2+-dependent channel activation.Before highlighting the key experimental observations in …
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DOI：
10.1085/jgp.109.5.647
发表时间：
1997-05
期刊：
The Journal of general physiology
影响因子：
--
作者：
Cui J;Cox DH;Aldrich RW
通讯作者：
Aldrich RW
每通道总充电移动。门控电荷位移与激活的电压灵敏度之间的关系。
影响因子：
3.8
作者：
Sigg, D;Bezanilla, F
通讯作者：
Bezanilla, F
影响因子：
2.9
作者：
Cui, JM;Aldrich, RW
通讯作者：
Aldrich, RW
影响因子：
16.2
作者：
Jiang, YX;Pico, A;MacKinnon, R
通讯作者：
MacKinnon, R
DOI：
10.1085/jgp.111.6.751
发表时间：
1998-06
期刊：
The Journal of general physiology
影响因子：
--
作者：
Rothberg BS;Magleby KL
通讯作者：
Magleby KL