KCNJ2-Induced Arrhythmia Mechanisms in CPVT and Heart Failure.

KCNJ2 诱导 CPVT 和心力衰竭的心律失常机制。

• 批准号: 10228058
• 负责人: Lee Lochbaum Eckhardt
• 金额: $ 38.12万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10228058
• 关键词: ANK2 gene; Address; Adrenergic Agents; Affinity; Ankyrins; Arrhythmia; Biophysical Process; Biophysics; CALM1 gene; Calcium; Calmodulin; Calsequestrin; Cardiac; Catecholaminergic Polymorphic Ventricular Tachycardia; Cause of Death; Cell model; Chronic; Clinical; Closure by clamp; Cyclic AMP-Dependent Protein Kinases; Electrophysiology (science); Evidence based treatment; Exhibits; Functional disorder; Generations; Genes; Genetic; Goals; Heart; Heart Diseases; Heart Ventricle; Heart failure; Homeostasis; Human; Image; Interruption; Ion Channel; Knock-in; Knock-in Mouse; Lead; Link; Mass Spectrum Analysis; Mediating; Membrane; Membrane Potentials; Methods; Modeling; Muscle Cells; Mutation; Optics; Organ; Outcomes Research; Patients; Pharmaceutical Preparations; Phase; Phenocopy; Phenotype; Phosphorylation; Phosphorylation Site; Pore Proteins; Predisposition; Prevention; Resolution; Rest; Ryanodine Receptor Calcium Release Channel; Short QT syndrome; Stress; Syndrome; Systolic heart failure; Techniques; Testing; Transgenic Mice; Triad Acrylic Resin; United States; Ventricular; Ventricular Arrhythmia; Ventricular Tachycardia; adrenergic stress; biophysical properties; clinical phenotype; density; experimental group; genetic signature; improved; in vivo; innovation; inorganic phosphate; insight; loss of function; molecular dynamics; mouse model; mutant; optimal treatments; periodic paralysis; prevent; response; sudden cardiac death; triadin; voltage

Arrhythmic sudden cardiac death (SCD) is a leading cause of death in the United States and can be caused by ionic current abnormalities occurring in genetic arrhythmia syndromes or acquired heart disease such as heart failure. This project focuses on the impact of cardiac inward rectifier current (IK1) on -adrenergic-dependent genetic and acquired ventricular arrhythmias. IK1 maintains resting membrane potential, contributes to phase 3 repolarization, and is remodeled in heart failure. KCNJ2 encodes the ion channel Kir2.1 that forms the dominant protein pore subunit for IK1 in the human cardiac ventricle. Loss of function KCNJ2 mutations present with two clinical phenotypes, Adersen-Tawil Syndrome (ATS), composed of a triad of ventricular arrhythmias, dysmorphic features and periodic paralysis, or Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), which presents with adrenergic-dependent ventricular arrhythmias including polymorphic ventricular tachycardia (PMVT) and bidirectional VT (BiVT) with a lack non-cardiac ATS features. CPVT has been attributed to abnormal calcium (Ca2+) handling related to mutations in Ca2+ handling genes and the signature arrhythmia for CPVT, BiVT, is caused by Ca2+ overload. Unlike the other CPVT targets, Kir2.1 does not directly participate in Ca2+ homeostasis, yet Ca2+ modulates Kir2.1 by specifically blocking the outward Kir2.1 current. -adrenergic stimulation activates protein-kinase A (PKA), which phosphorylates Kir2.1 with subsequent increase in outward Kir2.1 current. How Kir2.1 with CPVT-causing mutations fail to respond to PKA is unknown, particularly since the known CPVT mutations are not phosphorylation sites. Our central hypothesis is that under -adrenergic stimulation, CPVT-causing Kir2.1 mutant channels have loss of outward current due to both lack of a PKA response and increased sensitivity to Ca2+ block, reducing outward current and thus repolarization drive causing membrane potential instability, favoring delayed after-depolarizations (DADs) triggered activity. Additionally, decreased IK1 in systolic heart failure is thought to be a key feature in ventricular arrhythmias and SCD. We hypothesize that IK1 is decreased predominately during -adrenergic stimulation due to elevated Ca2+ in a manner similar to CPVT-causing KCNJ2 mutations. In this study, we will address these questions using a variety of cellular models and transgenic mouse models to determine the biophysical properties, Ca2+ sensitivity, phosphorylation state and arrhythmia mechanism of KCNJ2 mutations associated with a CPVT or an ATS phenotype and compare that to a heart failure model. Our innovative methods will include high-definition mass spectrometry, optical mapping and calcium imaging. The outcomes of this research will allow us to elucidate the mechanism by which -adrenergic-dependent loss of IK1 can result in ventricular arrhythmia in CPVT and heart failure and compare that to an ATS arrhythmia mechanism. Elucidating the nuances of IK1 dysfunction and Ca2+ handling under -adrenergic stress will lead to more evidence-based treatment approaches and prevention of SCD.

心律不齐的心脏死亡（SCD）是美国的主要死亡原因，可能是由 遗传心律不齐综合征或心脏病等产生的离子电流异常 失败。该项目侧重于心脏向内整流器电流（IK1）对肾上腺素的影响 遗传和获得的心室心律不齐。 IK1保持静息膜电位，有助于第3阶段 复制，并在心力衰竭中重塑。 KCNJ2编码形成的离子通道kir2.1 人类心脏通气中IK1的主要蛋白质孔亚基。功能丧失kCNJ2突变 具有两个临床表型，由室心律失常三合会组成的Adersen-Tawil综合征（ATS）， 营养不良的特征和周期性瘫痪或儿茶酚胺能多态性心动心动过速 （CPVT），呈现肾上腺依赖性心律不齐，包括多态性心律失常 心动过速（PMVT）和双向VT（BIVT）缺乏非心动ATS特征。 CPVT已有 归因于与Ca2+处理基因突变有关的异常钙（Ca2+）处理 CPVT，BIVT的心律失常是由Ca2+过载引起的。与其他CPVT目标不同，Kir2.1不直接 参与Ca2+稳态，但是CA2+通过专门阻止向外的Kir2.1电流来调节Kir2.1。 -肾上腺素能刺激激活蛋白质激酶A（PKA），该蛋白激酶A（PKA）磷酸化Kir2.1随后磷酸化 向外增加Kir2.1电流。与CPVT引起的突变无法响应PKA的Kir2.1是如何对PKA做出的 未知，特别是因为已知的CPVT突变不是磷酸化位点。我们的中心假设是 在-肾上腺素能刺激下，CPVT引起的Kir2.1突变通道由于 两者都缺乏PKA响应和对Ca2+块的敏感性提高，从而降低了向外电流，因此 重质驱动导致膜潜在的不稳定，有利于延迟depolarisis（dads） 触发活动。此外，收缩性心力衰竭中的IK1降低被认为是心室的关键特征 心律不齐和SCD。我们假设在肾上腺素能刺激期间，IK1主要降低 以类似于引起CPVT的KCNJ2突变的方式升高Ca2+。在这项研究中，我们将解决这些 使用多种细胞模型和转基因小鼠模型来确定生物物理的问题 与KCNJ2突变相关的特性，Ca2+灵敏度，磷酸化状态和心律不齐机理 使用CPVT或ATS表型，并将其与心力衰竭模型进行比较。我们的创新方法将 包括高清质谱，光学映射和钙成像。结果的结果 研究将使我们能够阐明-肾上腺素依赖性损失IK1的机制可以导致 CPVT和心力衰竭中的心室心律不齐，并将其与ATS心律失常机制进行比较。 阐明IK1功能障碍和Ca2+处理的细微差别在-肾上腺能力下将导致更多 基于证据的治疗方法和SCD的预防。