Molecular and Cell Biological Foundations of Proteostress-Induced Neuronal Extrusion

大脑的健康衰老高度依赖于一系列蛋白质质量控制系统，而这种质量 在神经退行性疾病中，控制能力经常被破坏。最近发现了一种疾病， 神经元可以将有毒产物，如聚集的蛋白质，转移到邻近的细胞，可能导致 病理在大脑中的传播。神经元在体内如何产生和发出细胞外物质是一个 当我们考虑治疗干预时必须解决的问题。基础研究可以提供信息 与迟发性神经退行性疾病相关的机制，并可提出治疗途径。 我们的研究利用了简单动物模型线虫的巨大技术优势 允许进行实验，以获得对神经退行性变和神经保护的机械性见解 生物学。通过高度保守的分子功能和自然透明的身体计划，吸取了经验教训 从单个神经元动力学的直接可视化和测量中，完整的成年动物提供高 了解包括人类在内的更复杂系统中的关键亚细胞过程的预测能力。 我们发现，一些受到压力的线虫神经元可以排出我们称之为“外显”的巨大囊泡，这种囊泡可以 装载着人类疾病蛋白质聚集体。Exopher的形成在增加后急剧增加 对这些神经元蛋白质质量控制的挑战，包括人类阿尔茨海默病的过度表达 片段Aβ1-42或与亨廷顿病相关的多聚Q蛋白。胞外挤出的聚集蛋白 被与邻近细胞的神经胶质修剪样的相互作用所占据，试图降解。 我们假设，外溢物的产生是成年神经元以前未被认识到的替代途径 蛋白质聚集体清晰，细胞器受损。巨大囊泡萌发和巨大囊泡萌发的过程高度相似 最近有报道称，线虫肌肉中有聚集体、脂质和受损细胞器的转移， 小鼠心肌细胞，以及小鼠和人脑，强烈地暗示了我们关于如何 这一过程在线虫中运行，将在不同物种之间广泛相关，包括告知难以捉摸的 神经退行性疾病在人脑中的传播机制。 我们建议利用线虫模型的相当大的优势(透明的身体，容易的遗传 操控，精致的神经系统，强大的细胞生物学，短的寿命)来推进根本 了解外星人生物学。我们的目标是定义遗传和细胞生物学机制 在外生形成中操作，重点是细胞骨架在外生中的作用：1)定义遗传 和微管动力学的细胞生物学机制，介导胞外形成；2)解决如何 神经元完成分裂，释放出一个大的充满聚集体的区域，留下一个完整的神经元。 我们的工作应该揭示一种与健康大脑老化和蛋白质平衡控制相关的新途径 神经退行性疾病，为研究和开发临床干预措施定义了一个新的领域。

Healthy aging of the brain is highly dependent upon a range of protein quality control systems, and such quality control capacity is often disrupted in neurodegenerative disease. Recently it has come to light that diseased neurons can transfer toxic products, such as aggregated proteins, to neighboring cells, likely leading to the spread of pathology within the brain. How neurons generate and send out extracellular material in vivo is a question that must be addressed as we consider therapeutic intervention. Basic research can inform on mechanisms relevant to late onset neurodegenerative disease and can suggest avenues of treatment. Our studies take advantage of the enormous technical advantages in the simple animal model C. elegans permissive of experimentation that can yield mechanistic insight into neurodegeneration and neuroprotection biology. With high conservation of molecular function and a naturally transparent body plan, lessons learned from individual neuronal dynamics directly visualized and measured within the intact adult animal provides high predictive power for understanding key subcellular processes in more complex systems, including humans. We discovered that some stressed C. elegans neurons can extrude giant vesicles we call “exophers” that can be loaded with human disease protein aggregates. Exopher formation dramatically increases upon increased challenge to protein quality control in those neurons, including over-expressing human Alzheimer’s disease fragment Aβ1-42 or Huntington’s disease-associated polyQ protein. Aggregated proteins extruded in exophers are taken up by a glial pruning-like interaction with the neighboring cell, which attempts degradation. We hypothesize that exopher production is a previously unrecognized alternative route for adult neurons to clear protein aggregates and damaged organelles. Highly similar processes of giant vesicle budding and transfer of aggregates, lipids, and damaged organelles have been recently reported in C. elegans muscle, mouse cardiomyocytes, and mouse and human brain, strongly implying that discoveries we make about how this process operates in C. elegans will be widely relevant across species, including informing on elusive spreading mechanisms operating in human brain in neurodegenerative disease. We propose to exploit the considerable advantages of the C. elegans model (transparent body, facile genetic manipulation, exquisitely defined nervous system, powerful cell biology, short lifespan) to advance fundamental understanding of exopher biology. Our goals are to define the genetic and cell biological mechanisms operative in exopher formation with a focus on the cytoskeletal roles in exophergenesis: 1) define the genetic and cell biological mechanisms of microtubule dynamics that mediate exopher formation; 2) address how a neuron accomplishes scission that releases a large aggregate-filled domain, leaving behind an intact neuron. Our work should inform on a novel pathway of proteostasis control relevant to both healthy brain aging and neurodegenerative disease, defining a new area for study and for development of clinical interventions.