KCNE1 and KCNE3 stabilize and/or slow voltage sensing S4 segment of KCNQ1 channel.
KCNE1 and KCNE3 stabilize and/or slow voltage sensing S4 segment of KCNQ1 channel.
复制标题
KCNE1和KCNE3稳定和/或kCNQ1通道的慢速电压传感S4段。
DOI：
10.1085/jgp.200709805
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发表时间：
2007-09
影响因子：
3.8
通讯作者：
Kubo, Yoshihiro
中科院分区：
文献类型：
--
作者：
Nakajo, Koichi;Kubo, Yoshihiro
KCNQ1是一种电压依赖性K+通道，其门控特性被辅助的KCNE蛋白显著改变。例如，主要在心脏和内耳表达的KCNE1显著减缓了KCNQ1的激活动力学。然而，在KCNE1存在的情况下，电压敏感的S4片段是否会有不同的移动尚不清楚。为了解决这个问题，我们系统地将半胱氨酸突变引入人类KCNQ1的S4片段的前半部分，一次一个。A226C位于S4片段的N端，在没有MTS试剂的情况下，其电流在重复刺激下是稳定的，因此被认为是最适合进行MTS可及性分析的突变体。MTS可及性分析表明，A226C突变体的表观二级速率常数是状态依赖的，在去极化过程中修改得更快，在有KCNE1的情况下比没有KCNE1的情况慢13倍。另一方面，在KCNE3存在下，修饰的二级速率常数不依赖于状态，这表明C226残基总是暴露在胞外环境中，即使在静止膜电位下也是如此。综上所述，这些结果表明，KCNE1使S4片段稳定在静息状态，并减缓了向激活状态的转变速度，而KCNE3则使S4片段稳定在激活状态。这些结果为KCNE1和KCNE3对KCNQ1通道的调制机制提供了新的见解。
KCNQ1 is a voltage-dependent K+ channel whose gating properties are dramatically altered by association with auxiliary KCNE proteins. For example, KCNE1, which is mainly expressed in heart and inner ear, markedly slows the activation kinetics of KCNQ1. Whether the voltage-sensing S4 segment moves differently in the presence of KCNE1 is not yet known, however. To address that question, we systematically introduced cysteine mutations, one at a time, into the first half of the S4 segment of human KCNQ1. A226C was found out as the most suited mutant for a methanethiosulfonate (MTS) accessibility analysis because it is located at the N-terminal end of S4 segment and its current was stable with repetitive stimuli in the absence of MTS reagent. MTS accessibility analysis revealed that the apparent second order rate constant for modification of the A226C mutant was state dependent, with faster modification during depolarization, and was 13 times slower in the presence of KCNE1 than in its absence. In the presence of KCNE3, on the other hand, the second order rate constant for modification was not state dependent, indicating that the C226 residue was always exposed to the extracellular milieu, even at the resting membrane potential. Taken together, these results suggest that KCNE1 stabilizes the S4 segment in the resting state and slows the rate of transition to the active state, while KCNE3 stabilizes the S4 segment in the active state. These results offer new insight into the mechanism of KCNQ1 channel modulation by KCNE1 and KCNE3.