Large-conductance Ca2+- and voltage-gated K+ channels form and break interactions with membrane lipids during each gating cycle
Large-conductance Ca2+- and voltage-gated K+ channels form and break interactions with membrane lipids during each gating cycle
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DOI：
10.1073/pnas.1901381116
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
Yutao Tian;S. Heinemann;T. Hoshi
中科院分区：
文献类型：
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作者：
Yutao Tian;S. Heinemann;T. Hoshi
重要性离子通道介导的电兴奋性驻留在膜脂质，然而，相互作用的性质仍然不清楚。这项研究表明，特定的正性氨基酸残基的Ca 2+和电压门控的K+ [大钾（BK）]通道，细胞兴奋性的负反馈组件，形成与负脂质氧原子的相互作用时，离子传导门是开放的。当门关闭时，相同的阳性残基与蛋白质内的阴性残基相互作用。这种脂质依赖性门控循环可以解释BK通道的细胞信号分子和药理学调节剂如何工作，推进对离子通道功能的基本理解并促进治疗药物的开发。膜去极化和细胞内Ca 2+促进大电导Ca 2+和电压门控（Slo 1）大钾（BK）通道的激活。我们研究的物理相互作用，稳定的关闭和开放的构象的离子传导门的人Slo 1通道，使用电生理和计算方法。结果表明，通过跨膜S6片段（“RKK环”）胞质末端的负残基（E321和E324）和正残基（329 RKK 331）的亚基间离子-离子相互作用，封闭构象得以稳定。当通道门打开时，RKK环断裂，正残基与附近的膜脂质氧原子发生静电相互作用。E321和E324通过水稳定。当329 RKK 331残基突变为疏水氨基酸时，这些残基与脂质尾部形成更强的疏水相互作用，以促进开放构象，将激活的电压依赖性向负方向移动高达400 mV，并稳定选择性过滤器区域。因此，RKK片段与来自两个来源的氧原子形成静电相互作用，其他氨基酸残基（E321/E324）和膜脂质，这取决于门状态。每当通道打开和关闭时，上述相互作用就会形成和破坏。这种脂质依赖性Slo 1门控可以解释两亲性信号分子和亲脂活性剂如何影响通道活性，并且类似的机制可能在其他离子通道中起作用。
Significance Ion channels mediating electrical excitability reside within membrane lipids; however, the nature of the interactions remains obscure. This study shows that specific positive amino acid residues of the Ca2+- and voltage-gated K+ [big potassium (BK)] channel, a negative-feedback component in cell excitability, form interactions with negative lipid oxygen atoms when the ion conduction gate is open. When the gate is closed, the same positive residues interact with negative residues within the protein. This lipid-dependent gating cycle may explain how cell-signaling molecules and pharmacological modulators of the BK channel work, advancing the fundamental understanding of ion channel function and facilitating therapeutic drug development. Membrane depolarization and intracellular Ca2+ promote activation of the large-conductance Ca2+- and voltage-gated (Slo1) big potassium (BK) channel. We examined the physical interactions that stabilize the closed and open conformations of the ion conduction gate of the human Slo1 channel using electrophysiological and computational approaches. The results show that the closed conformation is stabilized by intersubunit ion–ion interactions involving negative residues (E321 and E324) and positive residues (329RKK331) at the cytoplasmic ends of the transmembrane S6 segments (“RKK ring”). When the channel gate is open, the RKK ring is broken and the positive residues instead make electrostatic interactions with nearby membrane lipid oxygen atoms. E321 and E324 are stabilized by water. When the 329RKK331 residues are mutated to hydrophobic amino acids, these residues form even stronger hydrophobic interactions with the lipid tails to promote the open conformation, shifting the voltage dependence of activation to the negative direction by up to 400 mV and stabilizing the selectivity filter region. Thus, the RKK segment forms electrostatic interactions with oxygen atoms from two sources, other amino acid residues (E321/E324), and membrane lipids, depending on the gate status. Each time the channel opens and closes, the aforementioned interactions are formed and broken. This lipid-dependent Slo1 gating may explain how amphipathic signaling molecules and pharmacologically active agents influence the channel activity, and a similar mechanism may be operative in other ion channels.