Structure, Turnover and Safeguard of Mitochondria

总结 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，当它们最终受损时， 经历降解线粒体分裂由动力蛋白相关的GTP酶，DRP 1， 而融合是由两种动力蛋白相关的GTP酶OPA 1和mitofusin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、夏科氏病、 Marie-Tooth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、心血管疾病和与年龄相关的神经退行性疾病有关。我 该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措施。在过去的二十年里，我们 已经确定并表征了三种基本的GTP酶的核心反应， 膜融合和分裂。线粒体动力学的作用正在不断扩大， 现在包括线粒体的大小控制，它们的分布和周转， 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，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。新兴的生物学正在改变线粒体领域 结构和动力学。在未来五年，我们将解决由 这种智力进化。 首先，令我们惊讶的是，我们发现DRP 1将内质网（ER）塑造成 与线粒体形成接触点的小管。DRP 1产生的ER-线粒体接触 位点强烈促进线粒体分裂。我们将研究DRP 1如何创建ER- 在线粒体分裂中特异性起作用的线粒体接触位点， 使ER膜变形。其次，我们发现了一条生理途径 通过DRP 1控制的，Parkin/PINK 1独立的线粒体自噬在小鼠中的线粒体周转。 该途径的最上游事件是识别和标记受损的线粒体， 线粒体蛋白的泛素化。我们最初的实验表明， 发生在两个阶段-可逆的启动和承诺的扩增。我们将确定 在每一个阶段，什么泛素化线粒体，以及泛素连接酶如何复合 识别和标记体内受损的线粒体。第三，我们发现了第一个例子， 应激反应（MitoSafe），其通过控制线粒体结构来感知和调节线粒体结构。 融合与分裂之间的平衡我们将探索MitoSafe的分子基础 及其在小鼠中的生理作用。MIRA的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.