Sodium Channels and Cardiac Arrhythmias

项目摘要 在进化过程中，电压门控钠通道是最复杂的兴奋性的组织的基础 对确保动作的尖锐启动动力和正确传播至关重要的组织 并处于细胞兴奋性的中心。因此，电压门控钠通道基因的突变 与包括心律失常在内的一系列疾病有关。钠电流的修正(INa)是 已知会导致获得性心脏病引起的心律失常和遗传性心律失常。 自从电压门控钠通道编码基因的原始克隆和其记录以来 30多年前，钠通道的亚单位被认为是一种 单体。然而，在之前的资助期间，我们对SCN5A突变的研究发现与 几种不同的心律失常综合征使我们对钠通道形成心律失常的传统观念提出了质疑。 单体。事实上，我们和其他人已经表明，几种Brugada综合征(BRS)突变显示出显性- 负效应(dN效应)，只能归因于多聚体中亚基之间的相互作用 复合体。类似地，我们已经证明了几个BRS或LQT3SCN5A突变的缺陷可能是 被不同的SCN5A多态拯救，表达在单独的构造上，再次支持了 亚基相互作用。最后，我们还报告了不存在的非典型BRS突变的存在 当缺陷单独表达时，但当与WT共同表达时，再次导致电流幅度降低 支持亚基的相互作用。因此，多种证据挑战了传统的 钠通道存在于含有单一亚基的复合体中。因此，我们试图调查 钠通道亚基的化学计量学。我们使用不同的实验方法演示了 钠通道形成功能性二聚体。我们还确定了调节二聚化的区域，并发现 这种物理二聚化导致钠通道的耦合选通，并涉及14-3-3。我们的发现 改变了关于钠通道组装、结构和功能的传统范式。我们的整体 这种更新的假设是，钠通道的物理二聚化导致依赖于二聚化 对正常生理和心脏有影响的通道活动(即通道门控和运输) 与钠电流调节失调有关的病理。在目标1中，我们将研究生物物理耦合和 确定这是否为动态调制。在目标2中，我们将探索钠通道和 14-3-3的牵连。最后，在目标3中，我们将确定翻译后修饰在 钠通道的二聚化。了解渠道二聚化、贩运的机制 而功能性生物物理耦合可以打开治疗和/或预防的新方法和靶点之门 心力衰竭时钠离子通道病变和INA调节失调。

Project Summary Evolutionarily, voltage-gated sodium channels are fundamental to the organization of most complex excitable tissues where they are crucial to ensure the sharp initiation dynamics and proper propagation of the action potential and are at the center of cellular excitability. Hence, mutations in voltage-gated sodium channel genes have been linked to a whole host of diseases including cardiac arrhythmias. Modification in Na+ current (INa) is known to contribute to both cardiac arrhythmias from acquired heart diseases and inherited cardiac arrhythmias. Since the original cloning of the genes encoding for voltage-gated sodium channels and the recording of its function by patch-clamping over 30 years ago, the -subunit of the sodium channel was thought to be a monomer. However, during the previous funding period our studies of mutations found in SCN5A linked to several different arrhythmic syndromes led us to question the traditional idea of the sodium channel forming a monomer. In fact, we and others have shown that several Brugada Syndrome (BrS) mutations display dominant- negative effects (DN-effect), which could only be attributed to interaction between -subunits within multimeric complexes. Similarly, we have shown that the defects of several BrS or LQT3 SCN5A mutations could be rescued by different SCN5A polymorphisms expressed on a separate construct, again supporting the idea of an subunit interaction. Finally, we also reported the presence of atypical BrS mutations that do not present defects when expressed alone but lead to reduced current amplitudes when co-expressed with WT, again supporting an interaction of the subunits. Therefore, multiple lines of evidence challenged the conventional wisdom that sodium channels exist in complexes containing a single subunit. We thus sought to investigate the stoichiometry of sodium channel subunits. We demonstrated using different experimental approaches that sodium channels form functional dimers. We also identified the region modulating the dimerization and found that this physical dimerization results in coupled gating of the sodium channels and involves 14-3-3. Our findings shifted conventional paradigms in regards to sodium channel assembly, structure, and function. Our overall hypothesis for this renewal is that the physical dimerization of sodium channels leads to dimerization-dependent channel activity (i.e. channel gating and trafficking) with implication for normal physiology and for cardiac pathologies linked to dysregulation of the sodium current. In aim 1 we will study the biophysical coupling and determine if this is dynamically modulated. In aim 2 we will explore trafficking of the sodium channel and the involvement of 14-3-3. Finally in aim 3 we will determine the role of posttranslational modification in the dimerization of sodium channels. Understanding of the mechanisms involved in channel dimerization, trafficking and functional biophysical coupling could open the door to new approaches and targets to treat and/or prevent sodium channelopathies and dysregulation of INa in heart failure.