ARC REGULATES MITOCHONDRIAL DEATH SIGNALING IN HEART

描述（由申请人提供）：心脏细胞丢失是与许多心血管疾病相关的显著病理学特征，包括心肌梗死、缺血/再灌注、慢性缺血和心力衰竭。ARC（Apoptosis Repressor with CARD/Caspase Recruitment Domain）是新近发现的一种肌肉特异性细胞死亡抑制因子。它最初被鉴定为与死亡受体（TNFa，Fas）信号传导相关的起始剂胱天蛋白酶8相互作用并调节其活性的蛋白质。我们已发表的和初步的数据表明，有额外的目标，心脏保护ARC涉及半胱天冬酶依赖性和非依赖性途径。这些目标是两个主要的细胞内细胞器，线粒体和内质网/高尔基复合体的内在死亡信号通路。ARC存在于含有这些细胞器的亚细胞组分中，并且染色揭示了ARC与新生心肌细胞的ER/发育中的肌浆网（SR）的关联以及与SR广泛重叠的成年心肌纤维中的横纹横向分布。SR及其与线粒体的密切功能联系是其抑制各种内在死亡刺激的能力的原因，通常在死亡信号的最早阶段进行干预。在线粒体中，我们假设ARC干扰BAX易位/激活，而在ER/SR中，它作为内源性ER应激反应程序的保护臂的组成部分。为了验证这些假设，我们提出了以下具体目标：具体目标#1将定义ARC抑制BAX诱导的和BAX相关的细胞死亡的分子机制，以及其与线粒体融合/分裂装置的关键调节因子相关的功能意义。具体目标#2将确定ARC是否是ER应激反应（称为未折叠蛋白反应（UPR））的一部分，它在ER预处理中起什么作用，以及它是否抑制ER特异性起始剂胱天蛋白酶12。具体目标#3将定义ARC在调节ER/SR和线粒体死亡途径之间的细胞凋亡串扰中的作用，其通过其对钙动力学和响应于缺氧的引发剂半胱天冬酶活化的影响。提出的研究将确定ARC在管理线粒体和ER/高尔基体应激反应对心脏细胞损伤的关键作用。

DESCRIPTION (provided by applicant): Cardiac cell loss is a prominent pathological feature associated with a number of cardiovascular disorders, including myocardial infarction, ischemia/reperfusion, chronic ischemia, and heart failure. ARC (Apoptosis Repressor with CARD/Caspase Recruitment Domain) is a recently identified muscle-specific repressor of cell death. It was originally identified as a protein that interacts with and regulates the activity of initiator caspase 8 which is associated with death receptor (TNFa, Fas) signaling. Our published and preliminary data indicate that there are additional targets for cardioprotection by ARC involving both caspase-dependent and -independent pathways. These targets are the intrinsic death signaling pathways of two major intracellular organelles, the mitochondria and the endoplasmic reticulum/Golgi complex. ARC is present in both subcellular fractions containing these organelles and staining reveals an association of ARC with the ER/developing sarcoplasmic reticulum (SR) of neonatal cardiomyocytes and a striated transverse distribution in adult cardiac muscle fibers that overlaps extensively with the SR. We hypothesize that ARCs structural association with the ER/SR and its close functional association with mitochondria are what is responsible for its ability to suppress a variety of intrinsic death stimuli, often intervening at the earliest stages in death signaling. In the mitochondria, we hypothesize that ARC interferes with BAX translocation/activation, while in the ER/SR it acts as an integral component of the protective arm of the endogenous ER stress response program. To test these hypotheses, we propose the following specific aims: Specific Aim #1 will define the molecular mechanism by which ARC inhibits BAX-induced and BAX associatedcell death as well as the functional significance of its association with a critical regulator of the mitochondrial fusion/fission apparatus. Specific Aim #2 will establish whether ARC is part of the ER stress response known as the unfolded protein response (UPR), what role it plays in ER preconditioning, and whether it suppresses the ER-specific initiator caspase 12. Specific Aim #3 will define ARC's role in regulating the apoptotic crosstalk between the ER/SR and mitochondrial death pathways through its effects on calcium dynamics and initiator caspase activation in response to hypoxia. The studies proposed will define the critical role of ARC in the management of the mitochondrial and ER/Golgi stress responses to cellular injury in the heart.