Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA.
Chao Family Comprehensive Cancer Center, University of California, Irvine, Irvine, CA.
J Gen Physiol. 2021 Sep 6;153(9). doi: 10.1085/jgp.202012833. Epub 2021 Jul 6.
Voltage-gated sodium, potassium, and calcium channels consist of four voltage-sensing domains (VSDs) that surround a central pore domain and transition from a down state to an up state in response to membrane depolarization. While many types of drugs bind pore domains, the number of organic molecules known to bind VSDs is limited. The Hv1 voltage-gated proton channel is made of two VSDs and does not contain a pore domain, providing a simplified model for studying how small ligands interact with VSDs. Here, we describe a ligand, named HIF, that interacts with the Hv1 VSD in the up and down states. We find that HIF rapidly inhibits proton conduction in the up state by blocking the open channel, as previously described for 2-guanidinobenzimidazole and its derivatives. HIF, however, interacts with a site slowly accessible in the down state. Functional studies and MD simulations suggest that this interaction traps the compound in a narrow pocket lined with charged residues within the VSD intracellular vestibule, which results in slow recovery from inhibition. Our findings point to a "wrench in gears" mechanism whereby side chains within the binding pocket trap the compound as the teeth of interlocking gears. We propose that the use of screening strategies designed to target binding sites with slow accessibility, similar to the one identified here, could lead to the discovery of new ligands capable of interacting with VSDs of other voltage-gated ion channels in the down state.
电压门控钠离子、钾离子和钙离子通道由四个环绕中央孔道域的电压感应结构域 (VSD) 组成，在膜去极化时，它们从向下状态转变为向上状态。虽然许多类型的药物与孔道域结合，但已知与 VSD 结合的有机分子数量有限。Hv1 电压门控质子通道由两个 VSD 组成，不包含孔道域，为研究小分子配体如何与 VSD 相互作用提供了简化模型。在这里，我们描述了一种名为 HIF 的配体，它与向上和向下状态的 Hv1 VSD 相互作用。我们发现，HIF 像 2-胍基苯并咪唑及其衍生物一样，在向上状态通过阻断开放通道快速抑制质子传导。然而，HIF 与向下状态中缓慢可及的位点相互作用。功能研究和 MD 模拟表明，这种相互作用将化合物困在 VSD 细胞内前庭中带有带电残基的狭窄口袋中，导致抑制作用缓慢恢复。我们的发现指出了一种“齿轮卡住”的机制，其中结合口袋内的侧链将化合物困住，就像互锁齿轮的齿一样。我们提出，使用旨在靶向具有缓慢可及性的结合位点的筛选策略，类似于这里所确定的策略，可能会发现能够与向下状态的其他电压门控离子通道的 VSD 相互作用的新配体。
