Molecular Determinants of MG53 in Heart Structure and Function

项目总结 在亚细胞水平测量的心力衰竭是心肌细胞兴奋收缩受损的结果。 (E-C)耦合。E-C偶联的一个关键结构成分是肌细胞横行(T)-小管系统。T- 小管在协调膜兴奋和肌肉收缩方面起着至关重要的作用，它通过促进 肌浆网钙的同步释放。我们和其他人一样，都有 提供了强有力的证据表明，来自患者和动物模型的衰竭心肌细胞的特征是 T小管系统退化和紊乱导致细胞内钙动力学和 肌丝收缩。我们研究的长期目标是识别并利用 心脏病T小管重建过程中T小管重建的基本机制 正直和减缓心力衰竭的进展，如果不是逆转的话。我们已经确认了三明市53号 (MG53/TRIM72)作为一种潜在的T-小管修复酶。我们发现MG53已知参与了损伤诱导 膜泡在横纹肌中的运输和修复，定位于T管，在人类中上调 心脏衰竭和慢性心力衰竭的动物模型。我们的初步数据显示MG53拥有 心脏功能明显分化，MG53缺失加剧T小管变性 当外源性MG53过度表达时，应激心脏会促进进行性和严重的T小管破裂。 有趣的是，我们已经将过度表达效应映射到其鲜为人知的E3-连接酶结构域。这是我们的 因此，假设MG53的膜修复与E3-泛素连接酶活性决定 健康和疾病期间心肌细胞T管完整性和E-C偶联功能。我们最近做了 建立了两种新的敲门动物，分别检测内源性MG53 E3-连接酶和膜 心脏应激反应中的修复功能。我们将通过首先确定 MG53 E3-泛素连接酶及其膜的生理作用(目的1)和分子作用(目的2) 修复(目标3)，T管结构中的区域和在基线和对心脏应激的反应中的钙处理。 我们将把明显不一致的泛素依赖的蛋白分解和膜修复功能归因于 MG53与整体T小管完整性、E-C偶联和心脏重构过程有关。了解 MG53促进T小管重塑而不是修复的机制将使我们能够设计出高度有针对性的 以及治疗心力衰竭的有效疗法。

PROJECT SUMMARY Heart failure, measured at the subcellular level, is the result of impaired cardiomyocyte excitation-contraction (E-C) coupling. One key structural component of E–C coupling is the myocyte transverse (T)-tubule system. T- tubules play an essential role in coordinating membrane excitation with muscle contraction by facilitating the synchronized release of Ca2+ from the sarcoplasmic reticulum. Our group, as well as those of others, have provided strong evidence that failing myocytes from patients and animal models are characterized by a degenerated and disorganized T-tubule system resulting in impaired intracellular Ca2+ dynamics and myofilament contraction. The long-term goal of our research is to discern and take advantage of the fundamental mechanisms underlying T-tubule remodeling processes in heart disease toward restoring T-tubule integrity and slowing, if not reversing, heart failure progression. We have identified Mitsugumin 53 (MG53/TRIM72) as a potential T-tubule repair enzyme. We find MG53, known to be involved in injury-induced membrane vesicle trafficking and repair in striated muscle, localizes to T-tubules and is upregulated in human failing hearts and animal models of chronic heart failure. Our preliminary data indicate MG53 possesses apparent divergent functions in the heart, MG53 deletion of MG53 exacerbates T-tubule degeneration in stressed hearts while exogenous MG53 overexpression promotes progressive and severe T-tubule disruption. Interestingly, we have mapped overexpression effects to its little-studied E3-ligase domain. It is our hypothesis, therefore, that the membrane repair versus E3-ubiquitin ligase activities of MG53 determine cardiomyocyte T-tubule integrity and E-C coupling function during health and in disease. We have recently generated two novel knockin animals for separately examining endogenous MG53 E3-ligase and membrane repair functions during cardiac stress responses. We will test our hypothesis by first determining the physiological (Aim 1) and molecular (Aim 2) actions of the MG53 E3-ubiquitin ligase, as well as its membrane repair (Aim 3), domains in T-tubule structure and Ca2+ handling at baseline and in response to cardiac stress. We will attribute apparently discordant ubiquitin-dependent proteolysis and membrane healing functions of MG53 to overall T-tubule integrity, E-C coupling and cardiac remodeling processes. Understanding the mechanisms by which MG53 facilitates T-tubule remodeling versus repair will allow us design highly targeted and efficacious therapeutics for heart failure treatment.