Innate Immunity Pathways in Autophagy Signaling in Cardiac Myocytes

 描述（由申请人提供）：通过自噬-溶酶体机制有效去除受损的亚细胞器对于维持心肌细胞在稳态和缺血-再灌注（IR）损伤中的活力至关重要。新出现的证据表明，先天免疫蛋白作为细胞内“损伤传感器”协调其自噬清除的重要作用。一种这样的蛋白质，TRAF 2（肿瘤坏死因子受体相关因子-2），激活两种TNF受体下游的细胞保护信号传导以防止IR诱导的心肌细胞死亡。我们最近发现TRAF 2作为E3泛素连接酶在自噬去除心肌细胞中受损线粒体中的新作用。线粒体损伤触发PINK 1（一种丝氨酸-苏氨酸激酶）在线粒体外膜上的稳定化，其募集PARKIN（一种E3泛素连接酶）至泛素标记的线粒体蛋白进行降解。PINK 1信号传导是否也将TRAF 2募集到受损的线粒体;以及TRAF 2是否在体内线粒体自噬中维斯PARKIN起非冗余作用尚不清楚。在平行的研究中，我们也发现了内质网（ER）的压力和心脏IR损伤的条件下，内质网（ER）透化的证据。ER损伤激活IRE 1 α，IRE 1 α是一种ER定位的丝氨酸-苏氨酸激酶和RNA酶，与TRAF 2相互作用;体外研究表明，线粒体相关膜（MAM）上的IRE 1 α-TRAF 2信号传导协调受损线粒体和ER的自噬。在这个建议中，我们将测试的假设，TRAF 2信号介导的内质网和线粒体的选择性自噬，以调节心肌细胞的生存在稳态和压力下，在三个特定的目标。在目标1中，我们将确定TRAF 2在稳态和应激下心肌细胞存活中的作用。在目标2中，我们将研究TRAF 2维斯PARKIN在心肌细胞线粒体自噬中的作用。目的3：研究IRE 1 α-TRAF 2信号轴在心肌细胞ER吞噬中的作用。这些研究将阐明靶向TRAF 2作为先天免疫传感器的细胞基础，该传感器协调自噬去除在心肌细胞-ER界面（MAM）处受损的细胞器，以增强心肌梗死中的心肌细胞存活并预防心力衰竭，这是NIH的关键使命。

 DESCRIPTION (provided by applicant): Efficient removal of damaged sub-cellular organelles via the autophagy-lysosome machinery is critical for maintaining cardiac myocyte viability in homeostasis and with ischemia-reperfusion (IR) injury. Emerging evidence implicates an essential role for innate immunity proteins as intracellular `damage sensors' to orchestrate their autophagic removal. One such protein, TRAF2 (Tumor necrosis factor Receptor-Associated Factor-2), activates cytoprotective signaling downstream of both TNF receptors to prevent IR-induced cardiomyocyte death. We have recently discovered a novel role for TRAF2 as an E3 ubiquitin ligase in autophagic removal of damaged mitochondria in cardiac myocytes. Mitochondrial damage triggers stabilization of PINK1, a serine-threonine kinase, on the outer mitochondrial membrane, which recruits PARKIN, an E3 ubiquitin ligase to ubiquitin- tag mitochondrial proteins for degradation. Whether PINK1 signaling also recruits TRAF2 to damaged mitochondria; and whether TRAF2, plays a non-redundant role vis-à-vis PARKIN in mitochondrial autophagy, in vivo, is not known. In parallel studies, we have also uncovered evidence for endoplasmic reticulum (ER) permeabilization under conditions of ER stress and in cardiac IR injury. ER damage activates IRE1α, an ER-localized serine-threonine kinase and RNAase, which interacts with TRAF2; and in-vitro studies indicate that IRE1α-TRAF2 signaling at the mitochondria associated membranes (MAM) orchestrates autophagy of damaged mitochondria and ER. In this proposal, we will test the hypothesis that TRAF2 signaling mediates selective autophagy of endoplasmic reticulum and mitochondria to regulate cardiac myocyte survival in homeostasis and under stress; under three specific aims. In aim 1, we will determine the role of TRAF2 in cardiac myocyte survival in homeostasis and under stress. In aim 2, we will examine the role of TRAF2 vis-à-vis PARKIN in mitochondrial autophagy in cardiac myocytes. In aim 3, we will determine the role of IRE1α-TRAF2 signaling axis in ER-phagy in cardiac myocytes. These studies will elucidate the cellular basis for targeting TRAF2 as an innate immunity sensor that coordinates autophagic removal of damaged organelles at the mitochondria-ER interface (MAM) to enhance cardiomyocyte survival in myocardial infarction and prevent heart failure, a key mission of the NIH.