Calcium modification of voltage gated sodium channels

电压门控钠通道的钙修饰

• 批准号: 10798965
• 负责人: Christopher N. Johnson
• 金额: $ 21.6万
• 依托单位: MISSISSIPPI STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10798965
• 关键词: Action Potentials; Address; Affinity; Binding; Binding Proteins; Binding Sites; Calcium; Calmodulin; Cells; Central Nervous System; Complex; Conflict (Psychology); Custom; Data; Data Analyses; Disease; Electrophysiology (science); Genes; Goals; Impairment; Individual; Investigation; Ion Channel; Ion Channel Gating; Kinetics; Knowledge; Life; Literature; Measures; Modeling; Modification; Molecular Conformation; Mutation; Myocardium; Paper; Physiological; Point Mutation; Process; Protein Isoforms; Proteins; Recovery; Regulation; Reporting; Research Personnel; Role; Skeletal Muscle; Smooth Muscle; Sodium; Sodium Channel; Structure; Testing; Time; Work; design; novel; novel strategies; outcome disparities; small molecule; structural biology; treatment strategy; voltage

PROJECT SUMMARY Voltage-gated ion channels are essential for action potentials in excitable cells located throughout the body (central nervous system, smooth muscle, heart and skeletal muscle). Loss of, improper, or untimely function, can each cause or contribute to disease. Many individual point mutations in the genes of ion channel or accessory proteins have been associated with disease, some of which can be life threatening. Many disease- associated mutations are at or near accessory protein binding sites. Therefore, significant effort has been put forth by many investigators to characterize mechanisms of ion channel gating modification. It is well established that Ca2+ can alter ion channel function, and the Ca2+ sensing protein calmodulin (CaM) has a prominent role in these processes. Structural investigations have identified many distinct CaM-ion channel interactions; however, the posited physiological function and interpretation of this data is often controversial. Early studies relied on measuring ion channel function in the absence or presence of Ca2+ and this has generated seemingly disparate results. Subsequent investigation revealed the mechanism(s) of Ca2+- driven modification are complex and can involve multiple accessory proteins. I previously identified a high-affinity interaction between CaM and part of a voltage-gated sodium channel that is directly responsible for inactivating conduction. I leveraged my in-depth structural characterization to impair the CaM interaction without conferring additional modification to channel function. This is a notable accomplishment given this part of the channel undergoes rapid conformational change during each functional cycle. Because of this, I could for the first time clearly attribute modified sodium channel function to reduced CaM binding. My data demonstrate that sodium channels with this reduced CaM interaction require longer to recover from the inactivated state. Considering my structure/function findings with literature suggests a paradigm of CaM Facilitated Recovery from Inactivation (CFRI). As demonstrated in my papers and scientific data, CaM engages the inactivation gate of several sodium channel isoforms with high affinity, suggesting a unique model of regulation. My findings are in direct conflict with other reports that posit models of CaM Dependent Inactivation (CDI) and [Ca2+] insensitivity. These opposing models arise from knowledge gaps regarding (i) the kinetic rates of CaM interactions and (ii) the precise role of each CaM interaction in an excitable cell that contains oscillating [Ca2+]. My proposal addresses these knowledge gaps by uniquely combining structural biology, stopped-flow kinetics, and electrophysiology to dissect the roles of the CaM-ion channel interactions in excitable cells. Importantly, we then leverage this knowledge to design custom small molecules (SAR by NMR approach) that alter the kinetics of accessory protein interactions, with a goal of tuning channel gating. This work will test models of Ca2+ modification of ion channel function, and explore novel strategies for treating channelopathies.

项目概要 电压门控离子通道对于全身可兴奋细胞的动作电位至关重要 （中枢神经系统、平滑肌、心脏和骨骼肌）。功能丧失、不适当或不合时宜， 每种都可以导致或促成疾病。离子通道基因中的许多个体点突变或 辅助蛋白与疾病有关，其中一些可能危及生命。许多疾病—— 相关突变位于辅助蛋白结合位点处或附近。因此，已经付出了巨大的努力 许多研究人员提出来表征离子通道门控修饰的机制。 众所周知，Ca2+ 可以改变离子通道功能，而 Ca2+ 传感蛋白钙调蛋白 (CaM) 在这些过程中发挥着重要作用。结构研究已鉴定出许多不同的 CaM 离子 渠道互动；然而，假定的生理功能和对这些数据的解释通常是 有争议的。早期研究依赖于在存在或不存在 Ca2+ 的情况下测量离子通道功能， 这产生了看似不同的结果。随后的研究揭示了 Ca2+- 的机制 驱动修饰很复杂，可能涉及多种辅助蛋白。 我之前发现 CaM 和电压门控钠的一部分之间存在高亲和力相互作用 直接负责传导失活的通道。我利用我的深入结构 表征以损害 CaM 相互作用，而不会对通道功能进行额外的修改。 这是一项值得注意的成就，因为通道的这一部分在 每个功能周期。正因为如此，我第一次可以清楚地归因于修饰的钠通道 功能以减少 CaM 结合。我的数据表明，具有这种减少的 CaM 的钠通道 相互作用需要更长的时间才能从失活状态恢复。 考虑到我的结构/功能发现与文献提出了 CaM 促进的范例 失活恢复 (CFRI)。正如我的论文和科学数据所证明的那样，CaM 致力于 几种具有高亲和力的钠通道亚型的失活门，表明了一种独特的模型 规定。我的发现与其他提出 CaM 依赖性失活模型的报告直接冲突 (CDI) 和 [Ca2+] 不敏感。这些相反的模型源于关于（i）动力学速率的知识差距 CaM 相互作用以及 (ii) 每个 CaM 相互作用在包含振荡的可兴奋细胞中的精确作用 [Ca2+]。我的提案通过独特地结合结构生物学、停流技术来解决这些知识差距 动力学和电生理学来剖析 CaM-离子通道相互作用在可兴奋细胞中的作用。 重要的是，我们然后利用这些知识来设计定制小分子（通过 NMR 方法进行 SAR） 改变辅助蛋白相互作用的动力学，以调整通道门控为目标。这项工作将测试 Ca2+ 离子通道功能修饰模型，并探索治疗离子通道病的新策略。

项目成果

A Review of Calcineurin Biophysics with Implications for Cardiac Physiology.

• DOI: 10.3390/ijms222111565
• 发表时间: 2021-10-26
• 期刊: International journal of molecular sciences
• 影响因子: 5.6
• 作者: Williams RB;Johnson CN
• 通讯作者: Johnson CN