Removal of damaged mitochondria by alternative autophagy

摘要 线粒体是细胞内的中心细胞器，调节新陈代谢和三磷酸腺苷的产生。为了 在应激过程中维持线粒体的功能，心肌细胞(CMS)具有多层质量 调节线粒体分裂/融合、降解和生物发生的控制机制。有丝分裂，一个 线粒体选择性自噬，是受损线粒体降解的主要机制 保护心脏免受心力衰竭之苦。一般来说，有丝分裂是由相同的分子机制引起的。 通常用于一般的自噬，包括“自噬相关”(ATG)分子，以及其他 分子，包括PINK1/Parkin。然而，越来越多的证据表明，有丝分裂也是 不依赖于传统的自噬而诱导。在过去的资金周期中，我们已经表明， 在缺血期间，非常规形式的有丝分裂在保护心脏方面发挥着比 传统形式的有丝分裂。这种非传统形式的有丝分裂吞噬，称为替代有丝分裂吞噬，利用 与传统的有丝分裂不同的分子机制，即Ulk1-Rab9-RIP1-Drp1 蛋白质复合体。目前，选择性有丝分裂吞噬的功能意义和分子机制 人们对此仍然知之甚少。我们的长期目标是展示替代方案的功能重要性 在慢性和更多与体内病理相关的情况下，心脏中的有丝分裂，阐明了 潜在的分子机制，并最终应用我们的知识通过刺激治疗心脏病 另一种有丝分裂。有趣的是，尽管传统的自噬和有丝分裂吞噬作为反应被激活 在糖尿病心肌病小鼠模型中，高脂饮食(HFD)的激活是短暂的 而且它们只在HFD消费的早期阶段保护心脏。另一方面，一个 非常规形式的有丝分裂以更持久的方式被激活，并似乎扮演着重要的角色 在HFD消费的慢性期保护心脏的作用。我们在这里假设 选择性有丝分裂是慢性期心脏中有丝分裂的主要形式。 Hfd的消耗，在保护心脏免受糖尿病心肌病的影响方面起着至关重要的作用。 选择性有丝分裂是通过依赖TFE3的转录程序激活的，并且直接 包含Drp1和Drp1相互作用蛋白的大型蛋白质复合体与 线粒体。我们将使用独特的吞噬有丝分裂的基因改变的小鼠的指标来检验我们的假设 模型，形态分析，包括免疫金分析，脂质组学，转录组分析，以及 芯片测序分析。我们的研究将展示一种新的和有针对性的线粒体质量控制 糖尿病心肌病慢性发展过程中的机制。我们的研究应该导致 开发新的干预措施以维持糖尿病患者线粒体的质量并缓解 他们的心脏并发症，包括心脏肥大/功能障碍、脂毒性和炎症。

Summary Mitochondria are central intracellular organelles that mediate metabolism and ATP production. In order to maintain the function of mitochondria during stress, cardiomyocytes (CMs) have multiple layers of quality control mechanisms mediating mitochondrial fission/fusion, degradation and biogenesis. Mitophagy, a mitochondria-selective form of autophagy, is a major mechanism of degradation of damaged mitochondria and protects the heart against heart failure. In general, mitophagy is induced by the same molecular mechanisms commonly used by general autophagy, including “autophagy-related” (Atg) molecules, and additional molecules, including Pink1/Parkin. However, increasing lines of evidence suggest that mitophagy is also induced independently of conventional autophagy. During the past funding cycle, we have shown that an unconventional form of mitophagy plays a more critical role in protecting the heart during ischemia than the conventional form of mitophagy. This unconventional form of mitophagy, called alternative mitophagy, utilizes molecular machinery distinct from that used by conventional mitophagy, namely the Ulk1-Rab9-Rip1-Drp1 protein complex. Currently, the functional significance and the molecular mechanisms of alternative mitophagy remain poorly understood. Our long-term goal is to demonstrate the functional significance of alternative mitophagy in the heart during chronic and more pathologically relevant conditions in vivo, elucidate the underlying molecular mechanisms, and eventually apply our knowledge to treat heart disease by stimulating alternative mitophagy. Interestingly, although conventional autophagy and mitophagy are activated in response to high fat diet (HFD) consumption in the mouse model of diabetic cardiomyopathy, their activation is transient and they protect the heart only during the early phase of HFD consumption. On the other hand, an unconventional form of mitophagy is activated in a more prolonged manner and appears to play an essential role in protecting the heart during the chronic phase of HFD consumption. We here hypothesize that alternative mitophagy is the predominant form of mitophagy in the heart during the chronic phase of HFD consumption and plays an essential role in protecting the heart against diabetic cardiomyopathy. Alternative mitophagy is activated through a TFE3-dependent transcriptional program and the direct association of a large protein complex, containing Drp1 and Drp1 interacting proteins, with mitochondria. We will test our hypothesis using unique indicators of mitophagy, genetically altered mouse models, morphological analyses, including immunogold analyses, lipidomics, transcriptome analyses, and ChIP-sequencing analyses. Our study will demonstrate a novel and targetable mitochondrial quality control mechanism during the chronic development of diabetic cardiomyopathy. Our study should lead to the development of novel interventions to maintain the quality of mitochondria in diabetic patients and alleviate their cardiac complications, including cardiac hypertrophy/dysfunction, lipotoxicity, and inflammation.