Trafficking and Regulation of Cardiovascular K+ Channels

描述(由申请人提供)：这项提案的长期目标是了解调节细胞表面水平、心血管离子通道的定位和靶向的精确机制。房颤是最常见的心律失常，影响着200多万美国人，并导致因中风和心力衰竭而导致的重大死亡。人类心脏的这种电不稳定可能是由于继发于结构性心脏病的离子通道重塑或由于离子通道功能的原发遗传缺陷而导致的获得性障碍。Kv1.5是一种重要的心血管K+通道，对人心脏的心房复极起重要作用。功能性Kv1.5细胞表面表达的改变参与了阵发性和持续性房颤以及慢性缺氧性肺动脉高压的病理生理学过程。值得注意的是，尽管Kv1.5表面表达的变化与心血管疾病之间存在明显的联系，但对其质膜靶向或定位的控制机制知之甚少。最近，我们发现Kv1.5在心肌细胞质膜上发生了意想不到的动态转运，并证明了内化和循环在维持稳态离子通道表面水平中的作用。然而，与心脏中的大多数蛋白质一样，控制心房肌细胞Kv1.5表面水平的分子机制和调控机制仍不清楚。我们推测，在心房肌细胞中，Kv1.5的表面水平是由驱动蛋白和肌球蛋白马达的协调运动控制的，这些马达通过Rab GTP酶耦合到通道上，调节通道的内化和再循环。此外，我们认为这一过程受胆碱能刺激的调节，并可通过抗心律失常药物结合进行治疗控制。因此，在特定的目标1中，我们将确定Kv1.5在小鼠和人心房肌细胞中内化和再循环的分子机制。在具体目标2中，我们将确定胆碱能和肾上腺素能刺激在Kv1.5内化和循环的直接调控中的作用和机制。在具体目标3中，我们将确定抗心律失常药物诱导的Kv1.5通道内化的机制。我们建议的研究的成功完成无疑将有助于我们了解以Kv1.5表面表达改变为特征的病理生理条件下的事件，并可能为新的治疗策略提供新的见解，这些治疗策略旨在操纵特定的离子通道运输途径，用于治疗心血管通道疾病和调节心脏电兴奋性。

DESCRIPTION (provided by applicant): The long-term goals of this proposal are to understand the precise mechanisms regulating cell- surface level, localization and targeting of cardiovascular ion channels. Atrial fibrillation is the most common cardiac arrhythmia affecting more than 2 million Americans and results in significant mortality due to stroke and heart failure. This electrical instability in the human heart can occur through an acquired disorder attributable to ion channel remodeling secondary to structural heart disease or as a result from a primary genetic defect in ion channel function. Kv1.5 is a prominent cardiovascular K+ channel that is vital for atrial repolarization in the human heart. Alterations in the cell surface expression of functional Kv1.5 contribute to the pathophysiology of paroxysmal and persistent atrial fibrillation as well as chronic hypoxic pulmonary hypertension. Remarkably, despite the clear links between changes in Kv1.5 surface expression and cardiovascular disease, relatively little is known regarding the mechanisms controlling its plasma membrane targeting or localization. Recently, we have discovered an unexpected dynamic trafficking of Kv1.5 at the myocyte plasma membrane and demonstrated a role for internalization and recycling in the maintenance of steady- state ion channel surface levels. Nonetheless, similar to most proteins in the heart, the molecular machinery and the regulatory mechanisms controlling the surface levels of Kv1.5 in atrial myocytes remain unclear. We hypothesize that, in atrial myocytes, Kv1.5 surface levels are controlled by the coordinated movement of kinesin and myosin motors coupled to the channel by Rab GTPases that act to regulate channel internalization and recycling. Moreover, we propose that this process is modulated by cholinergic stimulation and can be therapeutically controlled by antiarrhythmic drug binding. Therefore in Specific Aim 1, we will define the molecular machinery involved in internalization and recycling of Kv1.5 in mouse and human atrial myocytes. In Specific Aim 2, we will determine the contribution and mechanisms of cholinergic and adrenergic stimulation to the direct modulation of Kv1.5 internalization and recycling. In Specific Aim 3, we will determine the mechanisms of antiarrhythmic drug-induced Kv1.5 channel internalization. Successful completion of our proposed studies will undoubtedly contribute to our knowledge of the events underlying the pathophysiological conditions characterized by altered Kv1.5 surface expression and likely provide novel insight into novel therapeutic strategies designed to manipulate specific ion channel trafficking pathways for the treatment of cardiovascular channelopathies and modulation of cardiac electrical excitability.