HCN Channels: Gating Change Movements and Mechanisms

描述（由申请方提供）：本项目的目的是表征电压门控离子通道的超极化激活环核苷酸门控阳离子通道（HCN）亚家族的门控电流和门控机制。HCN通道在结构上类似于电压门控性K+（Kv）通道，但是响应于膜超极化而不是去极化而开放。电压门控离子通道的开放可以通过三个过程来描述：电压感应、变构偶联和通道激活或孔开放。本计画旨在了解电压感应与导致HCN通道活化的变构偶合之间的分子关系。在Kv通道中，电压感应由带正电荷的跨膜结构域S4的电压依赖性运动产生。S4的移动导致孔打开或关闭，并且可以通过其产生的门控电流来测量。该项目将确定门控电流如何与HCN通道的时间和电压依赖性门控相关，S4结构域如何有助于这些门控电流，以及S4-S5连接体如何影响这些门控电流并将其耦合到孔开放。 该建议将提供S4在HCN通道激活中所起作用的第一个直接测量。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中的哪些残基有助于门控电流以及S4-S5接头如何调节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.