Defining new pathways for cardiac automaticity

项目摘要 心律失常是心脏病死亡的主要原因。藏有功能丧失的患者 Ankyrin-B(AnkB)基因的变异(ANK2)表现出严重和复杂的心脏表型，包括窦性心动过速 结节功能障碍、房颤(AF)、心率变异性(HRV)、传导缺陷、儿茶酚胺能 多形性室性心律失常(CPVT)和/或心脏性猝死。此外，之前的研究已经 研究表明，普通人群中常见的ANK2基因变异与QTC改变和 室性心律失常的易感性以及AnkB水平在心血管大动物模型中的变化 疾病。虽然这些研究为心律失常的共同机制和 关于获得性疾病形式，他们还发现了我们在控制 心率和节律由自主神经系统决定。鉴于异常自主神经控制的重要性 在心律失常和疾病中，了解潜在的分子通路是至关重要的 靶向关键的膜受体/通道。 这项K99/R00提案侧重于离子通道/膜蛋白的新作用和机制 人体心脏自律性的调节。这份K99/R00建议书涵盖了意想不到但直接相关的领域 心律失常生物学，每个都直接集成了临床、翻译和机械平台。这项建议是 基于临床和分子数据，证明了AnkB在调节血管紧张素转换酶中的关键和意外作用 两个IKACh通道亚基G蛋白激活的内向整流(GIRK1和GIRK1)的组装和靶向 GIRK4)，调节心脏的“飞或飞”反应以及对胆碱能反应的心房兴奋性 刺激物。我们确定了AnkB/GIRK的直接相互作用，并发现了携带GIRK4的心律失常患者 阻止这种互动的变种。房性心律失常和心率异常是独立的预测因素 心血管死亡率和IKACh失调是房性心律失常的主要标志，这些发现将 对先天和后天的人类心房疾病都有影响。我们假设Ankyrin-B 在调节GIRK4/GIRK1在心房和心脏的分子靶向和稳定中起着关键的未知作用 窦房结组织，从而控制交感神经/副交感神经平衡以调节心率。我们进一步 假设由于锚蛋白-B表达减少或人类锚蛋白-B表达减少导致的锚蛋白-B途径功能障碍- B功能缺失变异导致GIRK亚单位调节丧失，心脏自律性改变。我们会1) 确定GIRK1/GIRK4组装和膜靶向的分子机制；2)确定GIRK1/GIRK4的新作用 基于AnkB的GIRK/IKACh通路与自主神经调节；3)明确AnkB/GIRK4复合体在人类中的作用 基础和疾病状态下的心房肌细胞。

Project Summary Cardiac arrhythmias are a major cause of mortality in heart disease. Patients harboring loss-of-function variants in the ankyrin-B (AnkB) gene (ANK2) display severe and complex cardiac phenotypes, including sinus node dysfunction, atrial fibrillation (AF), heart rate variability (HRV), conduction defects, catecholaminergic polymorphic ventricular arrhythmia (CPVT), and/or sudden cardiac death. Moreover, previous studies have shown that common ANK2 gene variants in the general population are associated with QTc alterations and ventricular arrhythmia susceptibility, and that AnkB levels are altered in large animal models of cardiovascular disease. While these studies have provided important insight into arrhythmia mechanisms in common and acquired forms of disease, they have also identified important gaps in our understanding regarding control of heart rate and rhythm by the autonomic nervous system. Given the importance of abnormal autonomic control in cardiac arrhythmia and disease, it is essential to understand the underlying molecular pathways important for targeting of key membrane receptors/channels. This K99/R00 proposal focuses on new roles and mechanisms underlying ion channel/membrane protein regulation in human cardiac automaticity. This K99/R00 proposal covers unexpected, but directly related areas of arrhythmia biology, each directly integrating clinical, translational, and mechanistic platforms. This proposal is based on clinical and molecular data demonstrating a key and unexpected role of AnkB in regulating the assembly and targeting of the two IKACh channel subunits G-protein-activated inwardly rectifying (GIRK1 and GIRK4) that regulate cardiac `fight or flight' responses as well as atrial excitability in response to cholinergic stimuli. We identified direct AnkB/GIRK interactions and uncovered patients with arrhythmias harboring GIRK4 variants that block the interaction. As atrial arrhythmias and inappropriate heart rate are independent predictors of cardiovascular mortality and IKACh dysregulation is a major hallmark of atrial arrhythmias, these findings will have impact on both congenital and acquired forms of human atrial disease. We hypothesize that ankyrin-B plays a key unrecognized role regulating the molecular targeting and stabilization of GIRK4/GIRK1 in atria and sinoatrial node tissue, thus controlling sympathetic/parasympathetic balance to tune the heart rate. We further hypothesize that dysfunction in the ankyrin-B pathway due to reduced ankyrin-B expression or human ankyrin- B loss-of-function variants results in loss of GIRK subunit regulation and altered cardiac automaticity. We will 1) Identify molecular mechanisms for GIRK1/GIRK4 assembly and membrane targeting; 2) Identify novel roles for AnkB-based pathways in GIRK/IKACh & autonomic regulation; 3) Define roles of AnkB/GIRK4 complex in human atrial myocytes at baseline & in disease.