The kinetic and physical basis of KATP channel gating:: Toward a unified molecular understanding
The kinetic and physical basis of KATP channel gating:: Toward a unified molecular understanding
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DOI：
10.1016/s0006-3495(00)76779-8
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发表时间：
2000-05-01
影响因子：
3.4
通讯作者：
Nichols, CG
中科院分区：
文献类型：
--
作者：
Enkvetchakul, D;Loussouarn, G;Nichols, CG
K-ATP通道可以由含有或不含有SUR1的Kir6.2亚基组成。K-ATP通道的开放状态稳定性可以通过突变整个Kir6.2亚基来增加或降低，并通过在细胞膜上应用PIP来增加。开放状态稳定性的增加表现为在没有ATP的情况下通道开放概率的增加(PO-ZERO)和对ATP抑制的敏感性的相关降低。对带有和不带有SUR1的野生型和I154C突变通道进行了单通道寿命分析，通道动力学包括单一的不变的开放持续时间；不变的简短的关闭持续时间；以及由“指数混合体”组成的更长的关闭事件，这些事件在ATP中延长，在PIP处理后缩短。稳态和动态数据不能通过假设ATP与通道结合并导致门关闭来解释。相反，我们证明了它们可以用关于门控行为的假设如下的模型来解释：1)通道经历了从开放状态到短关闭状态(C-f)和更长寿命关闭状态(C-o)的对ATP不敏感的转变；2)在SUR1的存在下，C-O状态不稳定；3)ATP可以进入这种C-O状态，使其稳定，从而抑制宏观电流，PIP的作用和稳定开放状态的突变随后将从开放状态到ATP可访问的C-O状态的“关键转变”的平衡向O状态移动，降低了C-O状态的可及性，从而降低了ATP的敏感性。
K-ATP channels can be formed from Kir6.2 subunits with or without SUR1. The open-state stability of K-ATP, channels can be increased or reduced by mutations throughout the Kir6.2 subunit, and is increased by application of PIP, to the cytoplasmic membrane. Increase of open-state stability is manifested as an increase in the channel open probability in the absence of ATP (Po-zero) and a correlated decrease in sensitivity to inhibition by ATP. Single channel lifetime analyses were performed on wild-type and I154C mutant channels expressed with, and without, SUR1, Channel kinetics include a single, invariant, open duration; an invariant, brief, closed duration; and longer closed events consisting of a "mixture of exponentials," which are prolonged in ATP and shortened after PIP, treatment. The steady-state and kinetic data cannot be accounted for by assuming that ATP binds to the channel and causes a gate to close. Rather, we show that they can be explained by models that assume the following regarding the gating behavior: 1) the channel undergoes ATP-insensitive transitions from the open state to a short closed state (C-f) and to a longer-lived closed state (C-o); 2) the C-o state is destabilized in the presence of SUR1; and 3) ATP can access this C-o state, stabilizing it and thereby inhibiting macroscopic currents, The effect of PIP, and mutations that stabilize the open state is then to shift the equilibrium of the "critical transition" from the open state to the ATP-accessible C-o state toward the O state, reducing accessibility of the C-o state, and hence reducing ATP sensitivity.