Cardiac Myocyte Apoptosis: Mechanism and Significance

心肌细胞凋亡：机制和意义

• 批准号: 8054918
• 负责人: Richard N Kitsis
• 金额: $ 41.5万
• 依托单位: ALBERT EINSTEIN COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8054918
• 关键词: Alleles; Angioplasty; Apoptosis; Apoptosis Inhibitor; Apoptotic; Autophagocytosis; Cardiac; Cardiac Myocytes; Cell Death; Cell surface; Cessation of life; Defect; Degradation Pathway; Depressed mood; Event; Genetic; Genetically Engineered Mouse; Heart; Heart Diseases; Infarction; Inhibition of Apoptosis; Ischemia; Laboratories; Learning; Lysosomes; MDM2 gene; Maintenance; Mediating; Mitochondria; Molecular; Molecular Chaperones; Mus; Myocardial; Myocardial Infarction; Necrosis; Oxidative Stress; Pathogenesis; Pathway interactions; Pharmaceutical Preparations; Physiological; Play; Polyubiquitination; Process; Proteins; Reperfusion Therapy; Research; Role; Testing; Therapeutic; Time; Transgenic Mice; Ubiquitin-Proteasomal Pathway; Ubiquitination; base; heart dimension/size; in vivo; indexing; insight; knowledge of results; multicatalytic endopeptidase complex; mutant; novel; prevent; protein degradation; public health relevance; receptor; response; small molecule; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): 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. PUBLIC HEALTH RELEVANCE: ARC is a protein that protects heart muscle cells from dying, but at the beginning of a heart attack ARC is destroyed allowing heart muscle cells to die. The purpose of this research is to determine why and how ARC gets destroyed. The resulting knowledge may be useful in devising a medication to prevent ARC destruction and lessen the damage from heart attacks.

描述（由申请人提供）：有或没有再灌注的长期缺血会触发心肌细胞的凋亡和非凋亡死亡。这些细胞的死亡是心肌梗塞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介导的过程，这表明它们可以被抑制以在心脏病中发挥治疗优势。我们和其他人已经证明，在完整小鼠的缺血再灌注过程中抑制心肌细胞死亡可以限制梗死面积并保留心脏功能。细胞凋亡由两条中心途径介导，这两条途径在缺血再灌注期间的心肌细胞死亡中发挥重要作用。 ARC 是一种内源性细胞凋亡抑制剂，在心肌细胞中含量丰富。 ARC 在细胞凋亡抑制剂中是独一无二的，因为它通过我们已阐明的机制拮抗两条中枢细胞凋亡途径。 ARC 还通过未知的方式抑制坏死细胞死亡。鉴于 ARC 的丰富性和效力，为什么在缺血再灌注过程中大量心肌细胞死亡？缺血再灌注期间 ARC 蛋白水平的急剧下降表明了一种可能性。我们已经证明，这些减少是所导致的细胞死亡的触发因素，而不是结果，因为即使在亚基线水平维持 ARC 也会抑制细胞死亡。我们已经确定，缺血再灌注期间 ARC 蛋白水平降低，主要是因为 ARC 蛋白降解增加，并且 ARC 蛋白通过泛素蛋白酶体途径和溶酶体中的自噬降解。该项目的目的是确定体内缺血再灌注过程中介导 ARC 降解的分子机制，并确定每种机制对 ARC 蛋白丢失和导致的心肌细胞死亡的贡献。目标 1 研究该过程中的泛素-蛋白酶体途径。特别是，我们将描述 E3 连接酶 MDM2 作用于 ARC 的机制，以及我们已经确定的新型磷酸降解子在 ARC 中的潜在作用。目标 2 重点关注溶酶体途径，并寻求确定介导 ARC 降解的自噬形式。值得注意的是，我们在 ARC 中发现了一个新的基序，它可能针对 ARC 进行分子伴侣介导的自噬。目标 3 在基因工程小鼠中测试了早期目标的机制发现，这些小鼠的关键蛋白质降解机制存在缺陷。这些机制在 ARC 降解和体内心肌梗塞发生中的作用将被描述。这些研究将为心肌梗塞期间引发心肌细胞死亡的事件提供新的见解。此外，它们还可以为确定小分子疗法的靶标提供概念基础，以在心肌梗塞期间维持 ARC 水平，从而 (a) 限制梗塞面积和 (b) 扩大初次血管成形术再灌注治疗的时间窗口。公共卫生相关性：ARC 是一种保护心肌细胞免于死亡的蛋白质，但在心脏病发作初期，ARC 会被破坏，导致心肌细胞死亡。这项研究的目的是确定 ARC 被破坏的原因和方式。由此产生的知识可能有助于设计一种药物来防止 ARC 破坏并减轻心脏病发作造成的损害。