Structure, Turnover and Safeguard of Mitochondria

摘要 线粒体是控制细胞生死的重要细胞器。线粒体 是高度动态的：它们生长、分裂和融合，当它们最终被损坏时， 经历降解线粒体分裂是由动力蛋白相关的GTP酶DRP1介导的， 而融合是由两个动力蛋白相关的GTP酶，OPA1和丝裂原介导的。这些 GTP酶在人类疾病中发生突变，包括神经发育障碍、夏科特- 玛丽-牙齿神经病和视神经萎缩。这些蛋白质的活性也发生了变化 与代谢综合征、心血管疾病和年龄相关的神经退行性变有关。我的 实验室的目标是破译控制线粒体结构的分子机制 并将基础生物学转化为疾病干预。在过去的二十年里，我们 已经确定并表征了在核心反应中的三种重要的GTP酶 膜的融合和分裂。线粒体动力学的作用正在不断扩大，而且 现在包括线粒体的大小控制、它们的分布和周转以及线粒体的分化 神经元、心肌细胞、干细胞和免疫细胞。最近，很明显， 线粒体分裂和融合的机制比最初复杂得多。 想象的，涉及细胞器间的相互作用和反馈反应，监测和 调整他们的平衡。新兴的新生物学正在改变线粒体领域 结构和动力学。在未来5年，我们将解决以下重要问题 这种智力进化。 首先，令我们惊讶的是，我们发现Drp1将内质网(ER)塑造成 与线粒体形成收缩部位的小管。DRP1产生的内质网-线粒体接触 位点强烈促进线粒体分裂。我们将调查Drp1如何创建ER- 在线粒体分裂中起特殊作用的线粒体接触部位 与内质网结合，使内质网膜变形。第二，我们发现了一条生理途径 通过Drp1控制的、Parkin/PINK1不依赖的有丝分裂吞噬作用影响小鼠的线粒体周转。 这条途径最上游的事件是识别和标记受损的线粒体 线粒体蛋白泛素化。我们最初的实验表明，泛素化 发生在两个阶段-可逆的启动和承诺的扩增。我们将决定 是什么使线粒体在每个阶段泛素化，以及泛素连接酶复合体是如何 识别和标记体内受损的线粒体。第三，我们发现了第一个示例 应激反应(MitoSafe)，通过控制线粒体结构来感知和调整线粒体结构 融合与分化之间的平衡。我们将探索MitoSafe的分子基础 以及它在小鼠身上的生理作用。米拉资助将使我们能够发现新的逻辑 线粒体结构及其在体内的生理作用和调节。

Summary Mitochondria are essential organelles that control the life and death of cells. Mitochondria are highly dynamic: They grow, divide, and fuse, and when they eventually become damaged, undergo degradation Mitochondrial division is mediated by a dynamin-related GTPase, DRP1, while fusion is mediated by two dynamin-related GTPases, OPA1 and mitofusin. These GTPases are mutated in human diseases, including neurodevelopmental disorder, Charcot- Marie-Tooth neuropathy, and optic atrophy. Altered activities of these proteins have also been linked to metabolic syndrome, cardiovascular disease, and age-related neurodegeneration. My laboratory’s goal is to decipher the molecular mechanisms that control mitochondrial structure and translate the fundamental biology to disease interventions. In the past two decades, we have identified and characterized the three essential GTPases in the core reactions of membrane fusion and division. The roles of mitochondrial dynamics are ever-expanding, and now include size control of mitochondria, their distribution and turnover, and differentiation of neurons, cardiomyocytes, stem cells, and immune cells. Most recently, it became evident that the mechanisms of mitochondrial division and fusion are much more complex than initially imagined, involving inter-organelle interactions and a feedback response that monitors and tunes their balance. The emerging new biology is transforming the field of mitochondrial structure and dynamics. In the next 5 years, we will address the important questions raised by this intellectual evolution. First, to our surprise, we found that DRP1 shapes the endoplasmic reticulum (ER) into tubules that form contract sites with mitochondria. DRP1-produced ER-mitochondria contact sites strongly promote mitochondrial division. We will investigate how DRP1 creates ER- mitochondria contact sites that specifically function in mitochondrial division, associates with the ER, and deforms the ER membrane. Second, we discovered a physiological pathway of mitochondrial turnover via DRP1-controlled, Parkin/PINK1-independent mitophagy in mice. This pathway’s most upstream event is to recognize and mark damaged mitochondria by ubiquitination of mitochondrial proteins. Our initial experiments suggested that ubiquitination occurs in two phases – reversible initiation and committed amplification. We will determine what ubiquitinates mitochondria in each phase, and how the ubiquitin ligase complexes recognize and label damaged mitochondria in vivo. Third, we found the first example of a stress response (MitoSafe) that senses and adjusts the mitochondrial structure by controlling the balance between fusion and division. We will explore the molecular basis of MitoSafe and its physiological roles in mice. The MIRA grant will enable us to discover the new logics of mitochondrial structure and its physiological role and regulation in vivo.