The COP9 SIgnalosome in the Heart

描述（由申请人提供）：泛素-蛋白酶体系统（UPS）和自噬功能障碍是两种主要的细胞内蛋白水解途径，已在多种心脏病中观察到，并与充血性心力衰竭（CHF）的发生有关，充血性心力衰竭是几乎所有心脏病的最后共同途径，折磨着数百万美国人的生活。COP9信号体（CSN）是由8个独特亚基（CSN1 ~ CSN8）组成的进化保守蛋白复合体。在之前的竞争周期中，我们发现Csn8/CSN不仅需要ups介导的蛋白质水解，还需要自噬来发挥其在小鼠心脏中的蛋白质质量控制作用。围产期心肌细胞限制性CSN亚单位8敲除（CR-Csn8KO）在完整小鼠中主要引起大量心肌细胞（CM）坏死，这在自噬-溶酶体途径受损之前，并伴有UPS功能障碍。CR-Csn8KO小鼠出现扩张性心肌病并过早死于CHF。基于这些令人兴奋的新发现，我们建议破译Csn8/CSN调节心脏自噬-溶酶体途径和心肌细胞存活的分子机制。在完整小鼠中，我们将采用创新的遗传操作和药理学研究相结合的方法，追求三个具体目标来验证Csn8/CSN通过Rab7促进AM并促进CM中的PQC，从而通过抑制RIP1/ rip3介导的坏死途径促进CM存活的中心假设。特异性目标1定义了Csn8/CSN促进自噬的分子机制。这将验证Csn8/CSN通过Rab7调控自噬体成熟（AM）的假设。特异性目的2探讨蛋白酶体抑制自噬激活的病理生理意义。这是为了验证蛋白酶体功能不全（PFI）激活心脏自噬的假设，这种激活补偿了PFI引起的蛋白质质量控制损伤。特异性目的3验证了损伤的AM损害蛋白酶体底物降解的假设，以及UPS和自噬的双重损伤通过RIP1-RIP3介导的途径触发CM坏死的假设。这项研究的完成有望显著提高我们对心脏中蛋白质质量控制和降解途径如何协调调节的理解，特别是通过CSN，这将有助于寻找预防和/或更有效治疗CHF的新策略，CHF是美国死亡和残疾的主要原因。

DESCRIPTION (provided by applicant): Dysfunction of the ubiquitin-proteasome system (UPS) and autophagy, two main intracellular proteolytic pathways, have been observed in a variety of heart diseases and implicated in the genesis of congestive heart failure (CHF), the final common pathway for virtually all heart diseases and afflicting the life of millions of Americans. The COP9 signalosome (CSN) is an evolutionarily conserved protein complex consisting of 8 unique subunits (CSN1 ~ CSN8). In the preceding competitive cycle, we have discovered that the Csn8/CSN is required for not only UPS-mediated proteolysis but also autophagy to exert their protein quality control roles in mouse hearts. Perinatal cardiomyocyte-restricted CSN subunit 8 knockout (CR-Csn8KO) causes primarily massive cardiomyocyte (CM) necrosis in intact mice and this is preceded by impairment in the autophagic- lysosomal pathway and accompanied by UPS malfunction. The CR-Csn8KO mice develop dilated cardiomyopathy and die of CHF prematurely. Building upon these exciting novel findings, we propose to decipher the molecular mechanisms by which Csn8/CSN regulates the autophagic-lysosomal pathway and cardiomyocyte survival in the heart. Using a combination of innovative genetic manipulations and pharmacological interrogations in intact mice, we will pursue three specific aims to test the central hypothesis that Csn8/CSN promotes AM via Rab7 and facilitates PQC in CMs, thereby promoting CM survival by suppressing the RIP1/RIP3-mediated necrosis pathway. Specific aim 1 defines molecular mechanisms by which Csn8/CSN promotes autophagy. This will test the hypothesis that Csn8/CSN regulates autophagosome maturation (AM) via Rab7. Specific aim 2 investigates the pathophysiological significance of autophagic activation by proteasome inhibition. This is to test the hypothesis that proteasome functional insufficiency (PFI) activates cardiac autophagy and this activation compensates for protein quality control impairment caused by PFI. Specific aim 3 tests the hypotheses that impaired AM compromises the degradation of proteasome substrates and that the duo-impairment in the UPS and autophagy triggers CM necrosis via the RIP1-RIP3 mediated pathway. The completion of this research is expected to significantly improve our understanding on how protein quality control and degradation pathways in the heart are coordinately regulated, especially by the CSN, which will facilitate the search for new strategies to prevent and/or more effectively treat CHF, a leading cause of death and disability in the US.