Mitochondrial Quality Control in the Aging Myocardium

 描述（由申请人提供）：心血管疾病仍然是老年人的一个重大健康风险，衰老本身会显著增加心血管疾病的发病率。因此，更好地了解衰老的病理生理机制至关重要。细胞中功能失调的线粒体的积累被认为是衰老过程和许多与年龄相关的病理学的原因，但为什么这些线粒体在衰老细胞中积累目前尚不清楚。在心脏中，线粒体的主要功能是满足 通过氧化磷酸化提供ATP，满足跳动的心肌细胞的高能量需求。然而，线粒体可以迅速变成促进死亡的细胞器。它们可以成为活性氧的过度生产者，并释放促死亡蛋白。毫不奇怪，细胞已经发展出一种防御机制来对抗可能对细胞造成伤害的异常线粒体。研究发现，功能障碍的线粒体被自噬体迅速隔离，随后被递送到溶酶体进行降解。最近的研究表明，E3泛素连接酶帕金在标记细胞中功能障碍的线粒体降解中起着重要作用。帕金将外膜中的蛋白质泛素化，作为自噬体吞噬它们的标记。虽然有研究报道帕金在适应急性应激中起着重要作用，但迄今为止还没有研究关注帕金在衰老肌细胞中的作用。在这个探索性的建议中，我们将调查的假设，帕金森介导的线粒体自噬在预防年龄相关性心肌病的发展中起着重要作用。不幸的是，线粒体清除率随着年龄的增长而降低，这导致功能障碍的线粒体的积累。我们推测老年心肌线粒体清除率的降低是由氧化修饰和帕金失活引起的。这些假设将以两个目的进行检验。目的1探讨帕金森介导的线粒体清除在预防年龄相关性心肌病中的重要性。使用携带校正缺陷型线粒体DNA聚合酶γPOLGm/m）的小鼠模型，我们将研究Parkin在体外和体内清除线粒体中积累的mtDNA突变的重要性。我们还将POLGm/m小鼠与Parkin缺陷小鼠和心脏特异性Parkin转基因小鼠杂交，以探索对线粒体清除和年龄相关性心肌病的影响。在目标2中，我们将研究衰老心肌中氧化应激的增加是否有助于帕金蛋白的错误折叠和失活。这些研究将提供重要的新的见解帕金森介导的线粒体自噬在预防年龄相关性心肌病的作用。

 DESCRIPTION (provided by applicant): Cardiovascular disease remains a significant health risk for the elderly and aging itself significantly increases cardiovascular morbidity. Therefore, better understanding of the pathophysiological mechanisms underlying aging is critical. Accumulation of dysfunctional mitochondria in cells has been implicated as a cause of the aging process and a number of age-related pathologies but why these mitochondria accumulate in aging cells is currently unclear. In the heart, the primary function of mitochondria is to meet the high energy demand of the beating myocytes by providing ATP through oxidative phosphorylation. However, mitochondria can quickly change into death-promoting organelles. They can become excessive producers of reactive oxygen species and release pro-death proteins. Not surprisingly, cells have developed a defense mechanism against aberrant mitochondria that can cause harm to the cell. Studies have found that dysfunctional mitochondria are rapidly sequestered by autophagosomes and subsequently delivered to lysosomes for degradation. Recent studies have demonstrated that the E3 ubiquitin ligase Parkin plays an important role in marking dysfunctional mitochondria for degradation in cells. Parkin ubiquitinates proteins in the outer membrane which serves as labels for the autophagosomes to engulf them. Although studies have reported that Parkin plays an important role in adapting to acute stress, no studies to date have focused on Parkin's role in aging myocytes. In this exploratory proposal, we will investigate the hypothesis that Parkin-mediated mitophagy plays an important role in preventing development of age-related cardiomyopathy. Unfortunately, mitochondrial clearance is decreased with age which leads to accumulation of dysfunctional mitochondria. We hypothesize that the reduced mitochondrial clearance in the aged myocardium is caused by oxidative modification and inactivation of Parkin. These hypotheses will be tested with two aims. Aim 1 will explore the importance of Parkin-mediated mitochondrial clearance in preventing age-related cardiomyopathy. Using a mouse model carrying a proofreading defective mitochondrial DNA polymerase γPOLGm/m), we will investigate the importance of Parkin in clearing mitochondria with accumulating mtDNA mutations in vitro and in vivo. We have also crossed the POLGm/m mice with Parkin deficient mice and cardiac specific Parkin transgenic mice to explore the effect on mitochondrial clearance and age-related cardiomyopathy. In aim 2, we will investigate whether increased oxidative stress in the aging myocardium contributes to misfolding and inactivation of Parkin. These studies will provide important novel insight into the role of Parkin-mediated mitophagy in preventing age-related cardiomyopathy.