Determining the Role of Junctophilin-2 in Cardiac Disease

确定 Junctophilin-2 在心脏病中的作用

• 批准号: 8828771
• 负责人: Xander H.T. Wehrens
• 金额: $ 57.93万
• 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/8828771
• 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; Health; 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; 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）：肥厚型心肌病（HCM）是最常见的遗传性心脏病，其特征是左心室壁增厚、收缩功能障碍和潜在致命的心律失常。大量证据表明，兴奋-收缩耦合 (ECC) 缺陷会导致心肌病和心律失常的发病机制。称为“连接膜复合物”(JMC) 的特殊膜连接是质膜上 L 型 Ca 通道 (LTCC) 中的重要亚细胞结构，与肌质网 (SR) 上的兰尼碱受体 (RyR2) 通讯以启动收缩。关于 JMC 内控制 Ca2+ 通道正确亚细胞靶向的蛋白质知之甚少，但 junctophilin-2 (JPH2) 已被确定为关键候选者。在人类中，JPH2 的错义突变会导致 HCM，尽管其分子机制尚未解决。我们最近证明 JPH2 还结合并调节 JMC 中的 RyR2 通道，但参与这些相互作用的确切蛋白质结构域仍然未知。此外，据报道，HCM 患者和心力衰竭动物模型中 JPH2 的表达降低，但尚不清楚 JPH2 的缺失是否与衰竭心脏的收缩力受损和/或心律失常直接相关。我们已经生成了几种具有 HCM 相关 JPH2 突变或心脏中 JPH2 表达水平增加/减少的小鼠模型。该项目的长期目标是确定 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，以及异常的 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，在正常心脏中，JPH2 是 JMC 完整性和其中 Ca2+ 通道调节所必需的，而由于下调或突变而导致 JPH2 功能丧失，则会导致心肌病、心力衰竭和心律失常。为了检验这一假设，我们建议：在目标 1 中，确定 JPH2 在组织 JMC 内关键 Ca 处理蛋白中的作用。 - 在目标 2 中，揭示 JPH2 遗传变异导致 HCM 的机制。 - 在目标 3 中，确定 JPH2 下调是否是心力衰竭中 TT/JMC 丢失的原因。