Different fast-gate regulation by external Cl- and H+ of the muscle-type CIC chloride channels
Different fast-gate regulation by external Cl- and H+ of the muscle-type CIC chloride channels
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DOI：
10.1085/jgp.118.1.23
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发表时间：
2001-07-01
影响因子：
3.8
通讯作者：
Chen, TY
中科院分区：
文献类型：
--
作者：
Chen, MF;Chen, TY
肌肉型CIC通道（CIC-0和CIC-1）的快门响应于膜电位（V）的变化而打开。这种门控过程与外部Cl-与通道孔的结合密切相关，其方式是Cl-在结合位点的占据增加通道的开放概率（P-o）。外部H+也增强了这些通道中的快门开放，提示结合位点的质子化可能增加Cl-结合亲和力的假设，这可能是H+调节的潜在机制。Cl ~-和H ~+对快栅P-o-V曲线的调制方式不同。改变外部Cl-浓度（[Cl-]（o））使P-o-V曲线沿电压轴平行沿着，而降低外部pH主要增加曲线的最小P-o。此外，饱和和非饱和[Cl-]的H+调制是相似的。因此，H+效应油的快速门控似乎不是一个后果，在Cl-结合亲和力的增加。我们以前发现，一个超极化有利的开放过程是重要的，以确定在非常负的电压CIC-0的快栅P-O。这种[Cl-]（o）-独立的机制引起了很少的关注，但它似乎是由外部H+调制的开放过程。
The fast gate of the muscle-type CIC channels (CIC-0 and CIC-1) opens in response to the change of membrane potential (V). This gating process is intimately associated with the binding of external Cl- to the channel pore in a way that the occupancy of Cl- oil the binding site increases the channel's open probability (P-o). External H+ also enhances the fast-gate opening in these channels, prompting a hypothesis that protonation of the binding site may increase the Cl- binding affinity, and this is possibly the underlying mechanism for the H+ modulation. However, Cl- and H+, modulate the fast-gate P-o-V curve in different Ways. Varying the external Cl- concentrations ([Cl-](o)) shifts the P-o-V curve in parallel along the voltage axis, Whereas reducing external pH mainly increases the minimal P-o Of the Curve. Furthermore, H+ modulations at saturating and nonsaturating [Cl-], are similar. Thus, the H+ effect oil the fast gating appears not to be a consequence of an increase in the Cl- binding affinity. We previously found that a hyperpolarization-favored opening process is important to determine the fast-gate P-o of CIC-0 at very negative voltages. This [Cl-](o)-independent mechanism attracted little attention, but it appears to be the opening process that is modulated by external H+.