Determining the Role of Junctophilin-2 in Cardiac Disease

确定 Junctophilin-2 在心脏病中的作用

• 批准号: 8710750
• 负责人: Xander H.T. Wehrens
• 金额: $ 52.17万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8710750
• 关键词: Acute; Affect; Alleles; Allosteric Regulation; Animal Model; Arrhythmia; Binding; Calcium; Cardiac; Cardiac Myocytes; Cardiomyopathies; Cell membrane; Complex; Coupling; Data; Defect; Development; Diffusion; Down-Regulation; Exhibits; Functional disorder; Gene Delivery; Gene Transfer; Genetic; Goals; Growth; Heart; Heart Diseases; Heart Hypertrophy; Heart failure; Human; Hypertrophic Cardiomyopathy; Inherited; Left; Life; Link; Magnetic Resonance Imaging; Mediating; Membrane; Missense Mutation; Molecular; Mus; Muscle Cells; Mutation; Organ; Pathogenesis; Patients; Phosphorylation; Play; Process; Protein Kinase; Proteins; Proteomics; Regulation; Reporting; Role; RyR2; Ryanodine Receptors; Sarcoplasmic Reticulum; Signal Pathway; Signal Transduction; Structural Protein; Structure; Subcellular structure; System; Tertiary Protein Structure; Testing; Transgenic Mice; Transgenic Organisms; Variant; Ventricular; Work; age related; atrioventricular node; constriction; improved; junctophilin; mouse model; mutant; novel; prevent; public health relevance; vector; voltage

DESCRIPTION (provided by applicant): Hypertrophic cardiomyopathy (HCM) is the most-common inherited form of heart disease, characterized by thickening of the left ventricular wall, contractile dysfunction, and potentially fatal arrhythmias. There is extensive evidence that defects in excitation-contraction coupling (ECC) contribute to the pathogenesis of both cardiomyopathy and arrhythmias. Specialized membrane junctions known as 'junctional membrane complexes' (JMC) are important subcellular structures in L-type Ca channels (LTCC) on the plasmalemma communicate with ryanodine receptors (RyR2) on the sarcoplasmic reticulum (SR) to initiate contraction. Little is known about the proteins that govern proper subcellular targeting of Ca channels within JMCs, but junctophilin-2 (JPH2) has been identified as a key candidate. In humans, missense mutations in JPH2 cause HCM, although the molecular mechanisms remain unresolved. We have recently demonstrated that JPH2 also binds to and modulates RyR2 channels in the JMC, but the exact protein domains involved in these interactions are still unknown. Moreover, reduced expression of JPH2 has been reported in patients with HCM and animal models of heart failure, but it is unclear whether loss of JPH2 is directly linked to impaired contractility and/or arrhythmias in failing hearts. We have generated several mouse models with HCM-linked JPH2 mutations or with increased/decreased JPH2 expression levels in the heart. The long-term goal of this project is to define the molecular mechanisms by which JPH2 and associated molecules regulate JMC integrity and EC coupling in normal hearts, and how aberrant JPH2 function causes HCM, heart failure, and arrhythmias. Our overall hypothesis is that in normal hearts JPH2 is required for JMC integrity and the regulation of Ca channels therein, whereas loss of JPH2 function due to downregulation or mutation causes cardiomyopathy, heart failure and arrhythmias. To test this hypothesis, we propose to: In Aim 1, determine the role of JPH2 in organizing key Ca handling proteins within the JMC. - In Aim 2, unravel the mechanisms by which genetic JPH2 variants cause HCM. - In Aim 3, determine if JPH2 downregulation is the cause of loss of TTs/JMCs in heart failure.

描述（由申请人提供）：肥厚性心肌病（HCM）是心脏病最常见的遗传形式，其特征是左心室壁增厚，收缩功能障碍和潜在的致命性心律不齐。有广泛的证据表明，激发收缩偶联（ECC）的缺陷有助于心肌病和心律不齐的发病机理。在血浆中与ryanodine受体（RyR2）在sycoplasmic neticulum（SR）上通信的血浆中L型CA通道（LTCC）中，称为“连接膜复合物”（JMC）的专门膜连接处是L型Ca通道（LTCC）中的重要亚细胞结构。关于控制JMC中CA通道的适当亚细胞靶向的蛋白质知之甚少，但联合素-2（JPH2）已被确定为关键候选者。在人类中，尽管分子机制仍未解决，但JPH2中的错义突变会导致HCM。我们最近证明，JPH2还与JMC中的RYR2通道结合并调节RYR2通道，但是这些相互作用中涉及的确切蛋白质结构域仍然未知。此外，在患有HCM的患者和心力衰竭的动物模型中，JPH2的表达降低，但尚不清楚JPH2的丧失是否与失败的心脏中的收缩力和/或心律不齐直接相关。我们已经生成了几种具有HCM连接JPH2突变的小鼠模型或心脏中JPH2表达水平升高/降低。该项目的长期目标是定义JPH2和相关分子调节正常心脏中JMC完整性和EC耦合的分子机制，以及异常JPH2功能如何导致HCM，心力衰竭和心律失常。我们的总体假设是，在正常的心脏中，JPH2是JMC完整性和其中的CA通道所必需的，而下调或突变引起的JPH2功能丧失会导致心肌病，心力衰竭和心律失常。为了检验这一假设，我们建议：在AIM 1中，确定JPH2在组织JMC中组织键处理蛋白质中的作用。 - 在AIM 2中，揭示了遗传JPH2变体引起HCM的机制。 - 在AIM 3中，确定JPH2下调是否是心力衰竭中TTS/JMC丧失的原因。