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.

心律失常性心脏性猝死 (SCD) 是美国的一个主要原因，可能由以下原因引起： 遗传性心律失常综合征或获得性心脏病（如心脏病）中发生的离子电流异常 该项目重点关注心脏内向整流电流 (IK1) 对 β-肾上腺素能依赖性的影响。 遗传性和获得性室性心律失常 IK1 维持静息膜电位，有助于第 3 相。 KCNJ2 编码形成 KIR2.1 的离子通道。 人类心室中显性 IK1 的蛋白孔亚基存在功能丧失 KCNJ2 突变。 具有两种临床表型，Adersen-Tawil 综合征 (ATS)，由室性心律失常三联征组成， 畸形特征和周期性麻痹，或儿茶酚胺能多形性室性心动过速 (CPVT)，表现为肾上腺素依赖性室性心律失常，包括多形性室性心律失常 心动过速 (PMVT) 和双向 VT (BiVT) 缺乏非心脏 CPVT 功能。 归因于与 Ca2+ 处理基因和特征突变相关的异常钙 (Ca2+) 处理 CPVT（BiVT）心律失常是由 Ca2+ 过载引起的，与其他 CPVT 目标不同，Kir2.1 并不直接导致。 参与 Ca2+ 稳态，但 Ca2+ 通过特异性阻断向外的 Kir2.1 电流来调节 Kir2.1。 -肾上腺素能刺激激活蛋白激酶 A (PKA)，磷酸化 Kir2.1，随后 外向 Kir2.1 电流增加 具有引起 CPVT 的突变的 Kir2.1 如何无法对 PKA 做出反应。 未知，特别是因为已知的 CPVT 突变不是磷酸化位点。 在  肾上腺素能刺激下，引起 CPVT 的 Kir2.1 突变通道由于以下原因而失去外向电流 两者都缺乏 PKA 反应，并且对 Ca2+ 阻断的敏感性增加，从而减少外向电流，从而 复极化驱动导致膜电位不稳定，有利于延迟后去极化（DAD） 此外，收缩性心力衰竭中 IK1 的降低被认为是心室疾病的一个关键特征。 我们勇敢地说，IK1 主要在  肾上腺素能刺激期间下降。 以类似于 CPVT 引起的 KCNJ2 突变的方式导致 Ca2+ 升高。在本研究中，我们将解决这些问题。 使用各种细胞模型和转基因小鼠模型来确定生物物理问题 KCNJ2突变相关的特性、Ca2+敏感性、磷酸化状态和心律失常机制 CPVT 或 ATS 表型，并将其与心力衰竭模型进行比较。 包括高清质谱、光学测绘和钙成像。 研究将使我们能够阐明  肾上腺素依赖性 IK1 缺失导致的机制 CPVT 和心力衰竭中的室性心律失常，并将其与 ATS 心律失常机制进行比较。 阐明 β-肾上腺素能应激下 IK1 功能障碍和 Ca2+ 处理的细微差别将导致更多 基于证据的治疗方法和 SCD 的预防。