Amyloid-like phase transition of Junctophilin-2 protein in heart aging

摘要 超过90%的心力衰竭死亡发生在65岁以上的患者中。在许多情况下，细胞老化与 蛋白相转变为细胞毒性淀粉样聚集体，可导致器官功能障碍 和退化性疾病。人们已经认识到心脏中淀粉样蛋白的沉积会造成损害。 并导致侵袭性的心力衰竭。因此，很有必要扩大我们的 潜在的心脏淀粉样蛋白的知识。JPH2是一种心脏兴奋调节因子。 收缩偶联和转录是心肌病相关突变的热门靶点，包括 突变与老年心脏淀粉样变性的诊断表型相关。我们的出版物是为 首次发现JPH2具有形成淀粉样聚集体的内在能力。我们已经确定了 导致JPH2聚集的突变和可能的翻译后修饰。重要的是，我们 在小鼠心脏中检测到JPH2的年龄依赖性相变到不溶于SDS的状态。基于这些 初步数据，我们假设心肌细胞中淀粉样JPH2聚集可以由衰老或 突变，并相应地导致心脏功能障碍。这项建议专门针对1. 表征JPH2聚合体的淀粉样蛋白性质；2.定义JPH2聚集体的总体后果 对心脏功能的影响；3.确定几种与人类心肌病相关的jph2突变对心脏功能的影响 这种蛋白质的淀粉样相变。这项建议意义重大，因为定义与年龄相关的 JPH2的异常相变将为衰老提供新的机制和潜在的治疗靶点 相关的心脏功能不全。JPH2通常被认为对心脏有益，而过度表达JPH2 这种蛋白质被认为是一种治疗策略。这项研究将揭示这种蛋白质的病理作用。 作为细胞内淀粉样蛋白的来源，并评估JPH2在老化心脏中过度表达的潜在隐藏风险。 这一提议是新颖的，因为它为定义一种新的心脏淀粉样变蛋白提供了机会 在与衰老相关的心脏病理中。我们预计，分子工具、方法和通过 建议的研究将使我们能够争取长期资金，系统地探索病理 JPH2淀粉样蛋白相变在衰老心脏中的意义及机制。

Abstract Over 90% of heart failure deaths occur in patients over the age of 65. In many cases, cell aging is associated with aberrant protein phase transition to cytotoxic amyloid-like aggregates, which can cause organ dysfunction and degenerative diseases. It has been acknowledged that cardiac deposition of amyloids can cause damage to the heart and result in an aggressive form of heart failure. Therefore, there is a great need to expand our knowledge of potential cardiac amyloidogenic proteins. Junctophilin-2 (JPH2), a regulator of cardiac excitation- contraction coupling and transcription, is a hot target for cardiomyopathy associated mutations, including a mutation associated with diagnostic phenotypes of cardiac amyloidosis in aged patient. Our publication for the first time discovered that JPH2 has an intrinsic capability to form amyloid-like aggregates. We have identified mutations and possible posttranslational modifications that induce the aggregation of JPH2. Importantly, we detected age-dependent phase transition of JPH2 into SDS insoluble state in mouse hearts. Based on these preliminary data, we hypothesize amyloid-like JPH2 aggregation in cardiomyocytes can be induced by aging or mutations, and consequentially contribute to cardiac dysfunction. This proposal specifically aims at 1. characterize the amyloid nature of JPH2 aggregates; 2. defining the overall consequences of JPH2 aggregation for cardiac function; 3. determining the effect of several human cardiomyopathy associated JPH2 mutations on amyloid-like phase transition of this protein. This proposal is significant because defining the age-dependent aberrant phase transition of JPH2 would provide new mechanisms and potential therapeutic targets for the aging related heart dysfunction. JPH2 is conventionally considered to be beneficial for heart, and overexpression of this protein is considered to be a therapeutic strategy. This study would reveal a pathological role of this protein as a source of intracellular amyloids, and evaluate a potential hidden risk of overexpressing JPH2 in aging hearts. This proposal is novel, because it offers an opportunity to define a novel cardiac amyloidogenic protein involved in aging related cardiac pathology. We anticipate that the molecular tools, methods, and data generated through the proposed studies will enable us to compete for long-term funding to systematically explore the pathological significance and mechanisms of JPH2 amyloid phase transition in aging hearts.