HCN Channels: Gating Change Movements and Mechanisms

描述(由申请人提供)：本项目的目标是描述超极化激活的环核苷酸门控阳离子通道(HCN)亚家族电压门控离子通道的门控电流和门控机制。HCN通道在结构上类似于电压门控K+(Kv)通道，但开放是响应细胞膜超极化而不是去极化。电压门控离子通道的开放可以用三个过程来描述：电压传感、变构耦合和通道激活或孔道开放。本项目旨在了解电压感应和引起HCN通道激活的变构耦合之间的分子关系。在Kv通道中，电压敏感是由带正电的跨膜区S4的电压依赖运动引起的。S4的运动导致气孔的打开或关闭，并可以通过它产生的门控电流来测量。该项目将确定门控电流如何与HCN通道的时间和电压相关的门控相关联，S4结构域如何影响这些门控电流，以及S4-S5连接子如何影响这些门控电流并将它们耦合到孔开口。 这项提议将提供第一个直接测量S4在HCN通道激活中所起作用的方法。它将阐明HCN门控电流的大小、方向、电压依赖性和动力学，确定S4中的哪些残基对门控电流起作用，以及S4-S5连接子如何调节S4运动并将其耦合到HCN通道开放。

DESCRIPTION (provided by applicant): The goal of this project is to characterize the gating currents and gating mechanisms of the hyperpolarization-activated cyclic nucleotide-gated cation channel (HCN) subfamily of voltage-gated ion channels. HCN channels are structurally similar to voltage-gated K+ (Kv) channels, but open in response to nembrane hyperpolarization instead of depolarization. Voltage-gated ion channel opening can be described by three processes: voltage sensing, allosteric coupling and channel activation or pore opening. This project aims to understand the molecular relationship between voltage sensing and the allosteric coupling that causes HCN channel activation. In Kv channels, voltage sensing arises from the voltage dependent movement of the positively charged, transmembrane domain S4. Movement of S4 results in pore opening or closing and can be measured by the gating current it produces. This project will determine how gating currents are associated with he time- and voltage-dependent gating of HCN channels, how the S4 domain contributes to these gating currents, and how the S4-S5 linker affects these gating currents and couples them to pore opening. This proposal will provide the first direct measure of the role that S4 plays in HCN channel activation. It will elucidate the magnitude, direction, voltage dependence and kinetics of HCN gating current, determine which residues in S4 contribute to gating current and how the S4-S5 linker modulates S4 movement and couples it to HCN channel opening.