Sodium Channels and Cardiac Arrhythmias

项目摘要 在进化上，电压门控钠通道是组织最复杂的可兴奋的细胞的基础。 组织，它们对于确保动作的急剧启动动力学和适当传播至关重要 潜在的，并在细胞兴奋性的中心。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。Na+电流（INa）的改变是 已知其导致后天性心脏病和遗传性心律失常。 自从最初克隆了编码电压门控钠通道的基因并记录了它的变化以来， 30多年前，钠通道的β-亚基被认为是一种 单体的然而，在上一个资助期间，我们对SCN 5A中发现的突变的研究与 几种不同的糖尿病综合征使我们质疑钠通道形成一个钠通道的传统观念。 单体的事实上，我们和其他人已经证明，几个Brugada综合征（BrS）突变显示显性- 负效应（DN-效应），这只能归因于多聚体中的β-亚基之间的相互作用， 配合物类似地，我们已经表明，几种BrS或LQT 3 SCN 5A突变的缺陷可能是 通过在单独的构建体上表达的不同SCN 5A多态性来拯救，再次支持了 亚基相互作用。最后，我们还报告了非典型BrS突变的存在， 当单独表达时导致缺陷，但当与WT共表达时导致电流幅度降低， 从而支持所述多核苷酸亚基之间的相互作用。因此，多种证据挑战了传统的 钠离子通道存在于含有一个单亚基的复合物中。因此，我们试图调查 钠离子通道钙离子亚基的化学计量。我们用不同的实验方法证明， 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， 这种物理二聚化导致钠通道的偶联门控，并涉及14-3-3。我们的研究结果 改变了钠通道组装、结构和功能方面的传统范式。我们的整体 这种更新的假设是钠通道的物理二聚化导致二聚化依赖性的 通道活动（即通道门控和运输）与正常生理学和心脏 与钠电流失调有关的病理学。在目标1中，我们将研究生物物理耦合， 确定这是否是动态调制的。在aim 2中，我们将探索钠通道和 14-3-3的参与最后，在目标3中，我们将确定翻译后修饰在 钠通道的二聚化。了解通道二聚化、运输 和功能性生物物理耦合可以为治疗和/或预防的新方法和目标打开大门 心力衰竭中钠通道病和INa调节异常。

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.