Molecular Mechanisms of Pacemaker Channel Function

起搏通道功能的分子机制

• 批准号: 6866346
• 负责人: Michael Craig Sanguinetti
• 金额: $ 33.64万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-09-30 至 2009-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6866346
• 关键词: Xenopus oocyte; crosslink; cyclic compound; disulfide bond; divalent cations; heart electrical activity; heart function; heart pacemaker tissue; ion channel blocker; ionic bond; membrane channels; membrane potentials; microelectrodes; model design /development; nucleotides; point mutation; protein structure function; site directed mutagenesis; stoichiometry; voltage /patch clamp; voltage gated channel

DESCRIPTION (provided by applicant): The overall goal of this project is to characterize the molecular mechanisms of HCN and hERG channel gating. HCN channels conduct the pacemaker current (If), and hERG channels conduct the rapid delayed rectifier current IKr. The voltage and time-dependent gating of these currents contribute to the rhythmic firing of cardiac pacemaker cells. HERG channels are opened by membrane depolarization, coupled to outward motion of the S4 voltage sensor. In contrast, HCN channels are opened by membrane hyperpolarization, coupled to inward motion of the S4 domain. We hypothesize that the opposite polarity of coupling between S4 movement and activation of HCN and hERG results from channel-specific interactions between residues in the S4-S5 linker and the C-terminal end of the S6 domain. For hERG, we have characterized the gating currents associated with S4 movement and the structural basis for drug binding; we will extend these studies to HCN channels. In addition, the molecular mechanisms of altered hERG channel gating induced by changes in external cations will be determined. Ionic and gating currents will be recorded using two microelectrode and cut-open Vaseline gap voltage clamp techniques of channels heterologously expressed in Xenopus oocytes. These studies promise to further our understanding of the biological oscillator that controls heart rhythm.

描述（由申请人提供）：该项目的总体目标是表征HCN和HERG通道门控的分子机制。 HCN通道会导致起搏器电流（IF），而HERG通道进行了快速延迟整流器电流IKR。这些电流的电压和时间依赖性门控有助于心脏起搏器细胞的节奏性。 HERG通道通过膜去极化打开，并与S4电压传感器的向外运动结合。相反，HCN通道通过膜超极化打开，并耦合到S4结构域的内向运动。我们假设S4移动与HCN激活与HERG激活与HERG激活之间的相反极性是由S4-S5接头中的残基与S6域的C末端之间的频道特异性相互作用引起的。对于HERG，我们表征了与S4运动相关的门控电流和药物结合的结构基础。我们将将这些研究扩展到HCN渠道。另外，将确定外部阳离子变化引起的改变HERG通道门控的分子机制。离子和门控电流将使用两种微电极和切开的凡士林间隙电压夹在Xenopus卵母细胞中异源表达的通道技术。这些研究有望进一步了解控制心律的生物振荡器。