Deciphering Mechanisms of Mitochondrial Extrusion

蛋白质聚集和线粒体功能障碍是衰老和神经退行性疾病的关键因素， 比如老年痴呆症很明显，充分了解神经元用来对抗这些的机制， 毒性威胁对于临床神经保护策略的发展将是至关重要的。 Drivel实验室发现C.线虫的神经元可以分类并抛出神经元碎片， 在一个新的“细胞外垃圾消除”的战略降解。我们称这种挤压， 约0.4 μ m膜包围的囊泡，可包括蛋白质聚集体和线粒体，“外泌体”。我们 推测垃圾排出补充了已知细胞内蛋白质和细胞器降解途径， 帮助维持体内平衡。与这一观点相一致的是，挤压聚集填充的外泌体的神经元维持着 比不产生外泌体的神经元功能更好。我们还推测， 聚集体/线粒体传递到邻近细胞可能构成与细胞增殖相关的保守过程。 哺乳动物神经退行性疾病中病理物质的传播。促进对 因此，新发现的外泌体生物学可能在神经科学领域具有很高的影响。 我的兴趣集中在破译为什么以及如何选择线粒体驱逐在exophers。数据 这表明功能障碍的线粒体可能会优先被挤出，但对线粒体形成条件的了解， 分离特定的线粒体进入外泌区室，以及介导 这一区分尚处于初期阶段。我将利用C. elegans来调查 标记、移动和排出线粒体的主要机制。 我的第一个目标是确定诱导线粒体外泌体产生的条件，并验证 线粒体在这种条件下健康状况不佳。我会用遗传学的方法测试一系列 聚焦性损伤（异质性、嵴破坏、质量控制损害），以揭示 线粒体功能障碍的类型，引起远程降解的挤出。我也会调查 使用遗传学的线粒体超氧化物升高增加线粒体外泌体产生的细节， 光遗传学工具、线粒体评估工具和高分辨率显微镜。 我的第二个目标是确定线粒体外泌体产生所需的基因。我会用 RNAi方法来测试候选基因集（包括一些基于蛋白质组学的独特可用基因集）。 候选的哺乳动物尿道负载的外泌体）。如果时间允许，我也将参加一个公正的 筛选可以调节外泌体产生的基因。我将开始详细的机械研究1-2 保守的基因，有助于一些第一个分子理解的外泌体发生途径。 考虑到线粒体在所有生物学中的重要性，特别是在神经退行性疾病中， 老龄化，我计划的工作应该对开拓一个与人类健康高度相关的新研究领域具有重要意义。

Protein aggregation and mitochondrial dysfunction are key factors in aging and in neurodegenerative disease, like Alzheimer’s disease. It is clear that full understanding of mechanisms that neurons employ to combat these toxic threats will be critical for development of clinical neuroprotective strategies. The Driscoll lab has found that C. elegans neurons can sort and throw out neuronal debris for remote degradation in a novel “extracellular garbage elimination” strategy. We call such extrusions, which are large ~.4um membrane-surrounded vesicles that can include protein aggregates and mitochondria, “exophers”. We speculate that trash expulsion complements known intracellular protein and organelle degradation pathways to help maintain homeostasis. Consistent with this idea, neurons that extrude aggregate-filled exophers maintain better functionality than neurons that did not produce exophers. We also speculate that the mechanism of aggregate/mitochondrial hand-off to neighboring cells might constitute a conserved process relevant to the spread of pathological materials in mammalian neurodegenerative disease. Advancing understanding of the newly discovered exopher biology is thus likely to be of high impact in the neuroscience field. My interests is focused on deciphering why and how mitochondria are selected for expulsion in exophers. Data suggest that dysfunctional mitochondria may be preferentially extruded, but understanding of the conditions for segregation of particular mitochondria into the exopher compartment, and the cellular machinery that mediates this distinction is in its infancy. I will utilize the powerful molecular genetic tools of C. elegans to investigate principal mechanisms that mark, move, and expel mitochondria within exophers. My first aim is to define conditions that induce production of mitochondrial exophers and verify that mitochondria are of poor health under such conditions. I will use genetic means to test a range of mitochondrially-focused damage (heteroplasmy, cristae disruption, quality control impairment) to reveal the types of mitochondrial dysfunction that provoke extrusion for remote degradation. I will also investigate the details by which mitochondrial superoxide elevation increases the production of mito-exophers using genetics, optogenetics tools, mitochondrial assessment tools and high resolution microscopy. My second aim is to identify genes that are required for mitochondrial exopher production. I will use RNAi approaches to test candidate gene sets (including some uniquely available to us based on proteomics of candidate mammalian mitochondrial-loaded exophers). Time permitting, I will also participate in an unbiased screen for genes that can modulate production of exophers. I will initiate a detailed mechanistic study of 1-2 conserved genes to contribute some of the first molecular understanding of the exopher-genesis pathway. Given the profound importance of mitochondria in all of biology, especially in neurodegenerative disease and aging, the work I plan should be significant in carving out a new research area highly relevant to human health.