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。患有功能丧失的患者 锚蛋白B（AnkB）基因（ANK 2）的变异体显示出严重和复杂的心脏表型，包括窦性心律， 结功能障碍、心房颤动（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/或心源性猝死。此外，以前的研究 表明一般人群中常见的ANK 2基因变异与QTc改变相关， 室性心律失常的易感性，并且AnkB水平在心血管疾病的大型动物模型中改变， 疾病虽然这些研究为心律失常机制提供了重要的见解， 获得性疾病，他们还确定了我们对控制艾滋病毒/艾滋病的理解方面的重要差距。 自主神经系统控制心率和节律。考虑到异常自主控制的重要性 在心律失常和心脏疾病中，了解潜在的重要分子途径是至关重要的， 靶向关键膜受体/通道。 这个K99/R 00的建议集中在新的作用和机制的离子通道/膜蛋白 调节人类心脏自律性。本K99/R 00建议书涵盖了意外但直接相关的领域 心律失常生物学，每一个直接整合临床，转化和机制平台。这项建议是 基于临床和分子数据，证实了AnkB在调节细胞凋亡中的关键和意想不到的作用， 两个IKACh通道亚基G蛋白激活的内向整流（GIRK 1和 GIRK 4），调节心脏“战斗或逃跑”反应以及心房兴奋性，以响应胆碱能 刺激。我们发现了直接的AnkB/GIRK相互作用，并发现了携带GIRK 4的心律失常患者。 阻碍相互作用的变体。由于房性心律失常和不适当的心率是独立的预测因素 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 对先天性和后天性人类心房疾病都有影响。我们假设踝关节B 在调节心房中GIRK 4/GIRK 1的分子靶向和稳定性方面起着关键的未被认识的作用， 在一个实施例中，心脏起搏器可以通过刺激窦房结组织，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 假设由于减少锚蛋白-B表达或人锚蛋白- B功能丧失变异导致GIRK亚基调节丧失和心脏自律性改变。我们将（1） 确定GIRK 1/GIRK 4组装和膜靶向的分子机制; 2）确定GIRK 1/GIRK 4组装和膜靶向的新作用。 GIRK/IKACh和自主调节中基于AnkB的通路; 3）确定AnkB/GIRK 4复合物在人类中的作用 心房肌细胞在基线和疾病中。

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.