Cardiac Myocyte Apoptosis: Mechanism and Significance

长时间缺血伴或不伴再灌流触发心肌细胞凋亡性和非凋亡性死亡 肌细胞。这些细胞的死亡是心肌梗死发病机制的主要组成部分。 细胞凋亡和一些非凋亡形式的细胞死亡是主动调节的过程，这表明它们 可抑制对心脏病的治疗优势。我们和其他人已经证明，抑制 完整小鼠缺血再灌注期心肌细胞死亡可限制心肌梗死范围并保护心脏 功能。细胞凋亡由两条中枢通路介导，这两条通路在心肌细胞中都起着重要的作用 缺血再灌注期死亡。ARC是一种内源性的细胞凋亡抑制物，在心脏中大量存在 肌细胞。ARC是一种独特的细胞凋亡抑制药，它能拮抗两种中枢细胞凋亡途径 通过我们已经阐明的机制。ARC还通过未知的方式抑制坏死性细胞死亡。 鉴于ARC的丰富和效力，为什么大量的心肌细胞在缺血期间死亡- 再灌流？ARC蛋白水平在缺血期间的急剧下降表明了一种可能性- 再灌流。我们已经证明，这些减少是结果单元格的触发因素，而不是结果 死亡，因为ARC即使维持在低于基线水平也会抑制细胞死亡。我们已经确定 脑缺血再灌流过程中ARC蛋白水平下降主要是由于ARC蛋白的增加 ARC蛋白通过泛素-蛋白酶体途径和溶酶体被降解 通过自噬。这个项目的目标是确定调节ARC的分子机制。 在体缺血再灌流过程中的降解及其在ARC丢失中的作用 蛋白质和由此导致的心肌细胞死亡。目的1研究本病的泛素-蛋白酶体途径。 进程。特别是，将描述E3连接酶MDM2作用于ARC的机制 我们已经确定了一种新的磷酸降解子在ARC中的潜在作用。目标2专注于溶酶体 并试图确定介导ARC降解的自噬形式(S)。值得注意的是，我们有 在ARC中发现了一个新的基序，该基序可能针对ARC进行伴侣介导的自噬。AIM 3测试 在基因工程小鼠中发现关键蛋白缺陷的早期AIMS的机制发现 退化机制。这些机制在ARC降解和心肌发生中的作用 活体内的梗塞将被勾画出来。这些研究将为触发事件提供新的见解 心肌梗死时的心肌细胞死亡。此外，它们还可以为 心肌梗死期间维持ARC水平的小分子治疗靶点的确定 以(A)限制梗塞范围和(B)扩大直接血管成形术再灌注治疗的时间窗。

Prolonged ischemia with or without reperfusion triggers the apoptotic and non-apoptotic death of cardiac myocytes. The death of these cells is a major component in the pathogenesis of myocardial infarction. Apoptosis and some non-apoptotic forms of cell death are actively mediated processes, suggesting that they can be inhibited to therapeutic advantage in heart disease. We and others have shown that inhibition of cardiac myocyte death during ischemia-reperfusion in the intact mouse limits infarct size and preserves cardiac function. Apoptosis is mediated by two central pathways, both of which play important roles in cardiac myocyte death during ischemia-reperfusion. ARC is an endogenous inhibitor of apoptosis that is abundant in cardiac myocytes. ARC is unique among apoptosis inhibitors in that it antagonizes both central apoptosis pathways through mechanisms that we have elucidated. ARC also inhibits necrotic cell death through unknown means. Given the abundance and potency of ARC, why do large numbers of cardiac myocytes die during ischemia- reperfusion? A possibility is suggested by the dramatic decreases in ARC protein levels during ischemia- reperfusion. We have shown that these decreases are the trigger - not the consequence - of the resulting cell death because maintenance of ARC even at sub-baseline levels inhibits cell death. We have determined that ARC protein levels decrease during ischemia-reperfusion primarily because of increases in ARC protein degradation, and that ARC protein is degraded by both the ubiquitin-proteasomal pathway and in the lysosome via autophagy. The objective of this project is to define the molecular mechanisms that mediate ARC degradation during ischemia-reperfusion in vivo and to determine the contribution of each to the loss of ARC protein and resulting cardiac myocyte death. Aim 1 investigates the ubiquitin-proteasomal pathway in this process. In particular, the mechanisms by which the E3 ligase MDM2 act on ARC will be delineated, as will the potential role of a novel phosphodegron in ARC that we have identified. Aim 2 focuses on the lysosomal pathway and seeks to identify the form(s) of autophagy that mediate ARC degradation. Of note, we have identified a novel motif in ARC that may target ARC for chaperone-mediated autophagy. Aim 3 tests the mechanistic findings from the earlier aims in mice genetically engineered to have defects in key protein degradation mechanisms. The roles of these mechanisms in ARC degradation and the genesis of myocardial infarction in vivo will be delineated. These studies will provide novel insights into the events that trigger cardiac myocyte death during myocardial infarction. In addition, they may provide the conceptual basis for the identification of targets for small molecule therapies to maintain ARC levels during myocardial infarction so as to (a) limit infarct size and (b) expand the time window for reperfusion therapy with primary angioplasty.