Regulation of myocardial growth and death by autophagy

描述（由申请人提供）：自噬是长寿命蛋白质和细胞内细胞器降解的主要机制。自噬在能量饥饿（如心肌缺血）下起适应性作用，从而介导细胞存活，而自噬在某些病理条件下（如再灌注损伤）与程序性细胞死亡相关。因此，有必要阐明自噬在各种病理生理条件下的功能，并确定自噬在心脏中是如何调节的。在由永久性冠状动脉结扎（PCL）诱导的心肌梗死（MI）的小鼠模型中，尽管自噬的过度激活增加了急性期的死亡率，但自噬的下调导致慢性期的心脏功能障碍。哺乳动物无菌20样激酶1（Mst 1），一个有效的刺激细胞凋亡和心力衰竭，强烈抑制自噬，而FoxO 1，这是激活的营养饥饿和心脏卸载，刺激自噬。该项目的总体目标是阐明应激下心脏自噬的生理和病理功能，以及自噬如何通过心脏中的应激反应信号机制进行调节。我们假设：A）Beclin 1在MI急性期强烈诱导自噬是有害的，而FoxO 1在MI慢性期诱导的自噬是适应性的。B）Mst 1通过与Beclin 1的直接蛋白质-蛋白质相互作用作为自噬的内源性抑制剂，从而通过p62（一种泛素相互作用蛋白）引起蛋白质聚集体的积累。C）FoxO通过饥饿和心脏卸载被去乙酰化或上调，并且在介导适应性自噬中起重要作用。将使用（1）体外和体内评价自噬体形成和自噬通量的已建立的实验方法，（2）独特的遗传改变的小鼠模型，包括心脏特异性和诱导性Beclin 1敲低、atg 7 KO和FoxO 1 KO小鼠以及全身性p62 KO小鼠，（3）PCL和主动脉去带的小鼠模型，（4）shRNA介导的敲除和蛋白质组学。我们的研究将阐明自噬在应激下介导生理和病理功能的作用，以及调节心脏自噬的潜在信号机制。 公共卫生相关性：自噬是蛋白质通过溶酶体降解的重要机制，在多种病理生理条件下发挥适应性作用。我们的研究将阐明自噬在应激下介导生理和病理功能的作用，以及调节心脏自噬的潜在信号机制。从这项研究中获得的知识可能会导致更好地了解心肌损伤和心力衰竭的机制，并开发新的策略来治疗心肌梗死和心肌病患者。

DESCRIPTION (provided by applicant): Autophagy is a major mechanism of degradation for long-lived proteins and intracellular organelles. Autophagy plays an adaptive role under energy starvation, such as myocardial ischemia, thereby mediating cell survival, whereas autophagy associates with programmed cell death under some pathological conditions, such as reperfusion injury. Thus, it is essential to elucidate the function of autophagy in various pathophysiological conditions and to determine how autophagy is regulated in the heart. In a mouse model of myocardial infarction (MI), induced by permanent coronary ligation (PCL), although excessive activation of autophagy increases the mortality at an acute phase, downregulation of autophagy leads to cardiac dysfunction at a chronic phase. Mammalian sterile 20 like kinase 1 (Mst1), a potent stimulator of apoptosis and heart failure, strongly inhibits autophagy whereas FoxO1, which is activated by nutrient starvation and cardiac unloading, stimulates autophagy. The overall goal of this project is to elucidate both physiological and pathological functions of autophagy in the heart under stress and how autophagy is regulated by stress responsive signaling mechanisms in the heart. We hypothesize that: A) Strong induction of autophagy by Beclin 1 at an acute phase of MI is detrimental, whereas autophagy induced by FoxO1 at a chronic phase of MI is adaptive. B) Mst1 acts as an endogenous inhibitor of autophagy through direct protein-protein interaction with Beclin1, thereby causing an accumulation of protein aggregates through p62, an ubiquitin interacting protein. C) FoxOs are either deacetylated or upregulated by starvation and cardiac unloading and plays an essential role in mediating adaptive autophagy. These hypotheses will be tested, using (1) established experimental methods to evaluate autophagosome formation and autophagic flux in vitro and in vivo, (2) unique genetically altered mouse models, including cardiac specific and inducible Beclin1 knock down, atg7 KO, and FoxO1 KO mice and systemic p62 KO mice, (3) the mouse models of PCL and aortic debanding, (4) shRNA-mediated knock- down and proteomics. Our study will elucidate the role of autophagy in mediating both physiological and pathological functions under stresses and underlying signaling mechanisms regulating autophagy in the heart. PUBLIC HEALTH RELEVANCE: Autophagy, an important mechanism of protein degradation through lysosomes, plays an adaptive role in various pathophysiological conditions. Our study will elucidate the role of autophagy in mediating both physiological and pathological functions under stresses and underlying signaling mechanisms regulating autophagy in the heart. The knowledge obtained from this study may lead to better understanding of the mechanism of myocardial injury and heart failure and the development of novel strategies to treat patients with myocardial infarction and cardiomyopathy.