Voltage Sensor Movement in the HERG Potassium Channel

HERG 钾通道中的电压传感器运动

• 批准号: 6717409
• 负责人: MARTIN TRISTANI-FIROUZI
• 金额: $ 37.38万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-01-15 至 2008-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6717409
• 关键词: Xenopus oocyte; action potentials; arrhythmia; cardiovascular function; clinical research; electrophysiology; heart rhythm; membrane potentials; potassium channel; site directed mutagenesis; slow potential; voltage /patch clamp; voltage gated channel

DESCRIPTION (provided by applicant): The overall goals of this proposal are to define the structural basis of voltage sensor movement and the mechanism of coupling sensor movement to opening of HERG delayed rectifier K+ channels. HERG is one of several voltage-gated IC channels that mediate repolarization of the cardiac action potential. HERG channel dysfunction, caused by mutations or commonly prescribed medications, is associated with life-threatening arrhythmias. The critical role of HERG in the maintenance of normal cardiac electrical activity derives from its unusual gating properties: slow channel activation and fast inactivation. Activation and inactivation gating are voltage dependent, implying that these processes are coupled to movement of charged residues within the membrane. The structural basis of voltage sensor movement and mechanism of coupling sensor movement to HERG channel opening are not known. In this proposal, we provide the first description of HERG voltage sensor movement as measured by gating current. We hypothesize (1) the domains surrounding the S4 domain (the putative voltage sensor) influence the rate of S4 movement and account for the slow activation of HERG ionic current, (2) inactivation and activation gating are coupled to the same fundamental voltage sensing mechanism and (3) voltage sensor movement is coupled to channel opening via a direct interaction between the intracellular S4-S5 linker and the S6 domain. The aims of this proposal are to determine the structural basis of slow activation in HERG channels, to define the voltage sensor movement associated with fast HERG inactivation and to determine the mechanism whereby movement of the voltage sensor is coupled to channel opening. These aims will be accomplished using site-directed mutagenesis, chimeric constructs between HERG and the structurally related EAG channel, biochemical assays, two microelectrode voltage clamp and cut-open oocyte voltage clamp techniques. Insight into the molecular basis of voltage sensing in the HERG channel will advance our understanding of how this channel contributes to normal electrical stability in the heart and may advance our understanding of arrhythmia susceptibility.

描述（由申请人提供）：该提案的总体目标是定义电压传感器运动的结构基础以及将传感器运动耦合到HERG延迟整流器K+通道的打开的机制。 HEG 是介导心脏动作电位复极化的几种电压门控 IC 通道之一。由突变或常用处方药物引起的 HERG 通道功能障碍与危及生命的心律失常有关。 HERG 在维持正常心电活动中的关键作用源自其不寻常的门控特性：缓慢的通道激活和快速的失活。激活和失活门控依赖于电压，这意味着这些过程与膜内带电残基的运动耦合。电压传感器运动的结构基础以及传感器运动与 HEG 通道开口耦合的机制尚不清楚。在本提案中，我们首次描述了通过选通电流测量的 HEG 电压传感器运动。我们假设 (1) S4 域（假定的电压传感器）周围的域影响 S4 运动速率并解释 HERG 离子电流的缓慢激活，(2) 失活和激活门控与相同的基本电压传感机制耦合(3)电压传感器运动通过细胞内S4-S5连接子和S6结构域之间的直接相互作用与通道开放耦合。该提案的目的是确定 HERG 通道中缓慢激活的结构基础，定义与快速 HERG 失活相关的电压传感器运动，并确定电压传感器的运动与通道开放耦合的机制。这些目标将通过定点诱变、HERG 和结构相关的 EAG 通道之间的嵌合构建体、生化测定、两个微电极电压钳和切开卵母细胞电压钳技术来实现。深入了解 HERG 通道电压传感的分子基础将有助于我们了解该通道如何有助于心脏的正常电稳定性，并可能增进我们对心律失常易感性的理解。