Molecular basis for differential modulation of BK channel voltage-dependent gating by auxiliary γ subunits.
Molecular basis for differential modulation of BK channel voltage-dependent gating by auxiliary γ subunits.
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DOI：
10.1085/jgp.201511356
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发表时间：
2015-06
期刊：
影响因子：
--
通讯作者：
Yan J
中科院分区：
文献类型：
--
作者：
Li Q;Fan F;Kwak HR;Yan J
BKγ亚基在改变BK激活的电压依赖性方面的功效的显著差异主要取决于TM片段和邻近的细胞内带正电荷的氨基酸簇。大电导钙离子和电压激活钾通道（BK）由成孔α亚基和各种调节辅助亚基组成。BK通道辅助γ（BKγ）亚基是一类新发现的蛋白质，含有一个胞外富含亮氨酸重复结构域（LRRD）、一个跨膜（TM）片段和一个短的胞质C末端尾（C-tail）。虽然四种BKγ蛋白中的每一种都使BK通道激活的电压依赖性向超极化方向移动，但它们显示出明显不同的功效，在15-145 mV的范围内介导移动。对通过交换单个结构元件产生的嵌合BKγ亚基以及BKγ缺失和取代突变体的分析表明，四个BKγ亚基对BK门控的差异调节取决于由TM片段和相邻的细胞内带正电荷的氨基酸簇组成的小区域。对于BK通道激活的电压依赖性，γ1和γ2 TM段贡献了约-100 mV，γ1和γ3 C尾贡献了约-40 mV，而γ3和γ4 TM段以及γ2和γ4 C尾的贡献要小得多。大的细胞外LRRD主要是功能可互换的，尽管γ1 LRRD在增强（或减弱）BK通道电压依赖性门控向超极化电位的转变方面比其他BKγ亚基的作用略差（或略有效）。对突变的BKγ亚基的分析表明，带正电荷的氨基酸的近膜簇决定了γ1和γ3 C-尾的功能。因此，BKγ亚基的调节功能分别通过其TM片段和相邻细胞内带正电荷区域的变化进行粗调和微调。我们的研究结果表明，BK通道的调节辅助γ亚基依赖于内和/或近膜机制。
The marked difference in the efficacy of BKγ subunits in shifting the voltage dependence of BK activation depends mainly on the TM segment and a neighboring intracellular cluster of positively charged amino acids. Large conductance Ca2+- and voltage-activated potassium (BK) channels are comprised of pore-forming α subunits and various regulatory auxiliary subunits. The BK channel auxiliary γ (BKγ) subunits are a newly identified class of proteins containing an extracellular leucine-rich repeat domain (LRRD), a single transmembrane (TM) segment, and a short cytoplasmic C-terminal tail (C-tail). Although each of the four BKγ proteins shifts the voltage dependence of BK channel activation in a hyperpolarizing direction, they show markedly different efficacies, mediating shifts over a range of 15–145 mV. Analyses of chimeric BKγ subunits created by swapping individual structural elements, and of BKγ deletion and substitution mutants, revealed that differential modulation of BK gating by the four BKγ subunits depends on a small region consisting of the TM segment and the adjacent intracellular cluster of positively charged amino acids. The γ1 and γ2 TM segments contributed approximately −100 mV, and the γ1 and γ3 C-tails contributed approximately −40 mV, to shifting the voltage dependence of BK channel activation, whereas the γ3 and γ4 TM segments and the γ2 and γ4 C-tails contributed much less. The large extracellular LRRDs were mainly functionally interchangeable, although the γ1 LRRD was slightly less effective at enhancing (or slightly more effective at attenuating) the shift in BK channel voltage-dependent gating toward hyperpolarizing potentials than those of the other BKγ subunits. Analysis of mutated BKγ subunits revealed that juxta-membrane clusters of positively charged amino acids determine the functions of the γ1 and γ3 C-tails. Therefore, the modulatory functions of BKγ subunits are coarse- and fine-tuned, respectively, through variations in their TM segments and in the adjacent intracellular positively charged regions. Our results suggest that BK channel modulation by auxiliary γ subunits depends on intra- and/or juxta-membrane mechanisms.
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DOI：
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发表时间：
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影响因子：
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