Slow axonal transport of cytosolic cargoes by dynamic-recruitment - a new traffic

描述（由申请人提供）：神经元中的绝大多数蛋白质在细胞体中合成，并通过称为轴突运输的过程沿轴突向上运输到突触。蛋白质如tau和突触核蛋白的缓慢轴突运输缺陷长期以来被认为与许多神经退行性疾病有关，包括阿尔茨海默病和帕金森病，然而这些（和其他）细胞质蛋白的缓慢轴突运输机制知之甚少。我们在培养的神经元中开发了一个模型系统来直接观察胞质蛋白（包括突触核蛋白）的运输，并发现这些货物以缓慢的、运动依赖的顺行偏倚一致地移动。这种类型的移动以前没有报道过，可能代表了细胞内贩运/运输的一种新形式。基于这些和其他来自大脑的体内数据，我们提出了一个新的模型，其中单个细胞质蛋白单体聚集并组装成多蛋白复合物，由分子马达在神经元中携带，我们称之为“动态聚类”。在这里，我们提出了一系列实验来检验这个模型产生的预测和假设。一旦完成，这些研究将回答长期存在的关于这些蛋白质运输的问题，也为研究它们在病理状态下的运输打开了大门。

DESCRIPTION (provided by applicant): The vast majority of proteins in a neuron are synthesized in the cell bodies and transported along axons and up-to synapses by a process called axonal transport. Defects in slow axonal transport of proteins such as tau and ¿-synuclein have long been implicated in many neurodegenerative diseases including Alzheimer's and Parkinson's disease, however mechanisms of slow axonal transport of these (and other) cytosolic proteins is very poorly understood. We developed a model-system in cultured neurons to directly visualize the transport of cytosolic proteins (including ¿-synuclein) and found that these cargoes move coherently with a slow, motor-dependent anterograde bias. This type of movement has not been reported before and likely represents a new form of trafficking/transport within cells. Based on these and other in-vivo data from brains, we propose a new model where individual cytosolic protein monomers cluster and assemble into multi-protein complexes that are carried in neurons by molecular motors, a process we call 'dynamic clustering'. Here we propose a series of experiments to test predictions and hypotheses generated by this model. Upon completion, these studies would answer long-standing questions about the transport of these proteins and also open the door for investigation of their transport in pathologic states. PUBLIC HEALTH RELEVANCE: Neurodegenerative diseases like Alzheimer's and Parkinson's disease are a huge burden on our society and economy. These diseases are characterized by early deficits in synapses - the 'communication hub' of the brain; as well as impairments in axonal transport - the mechanism that that actually delivers various proteins into these synapses thereby maintaining their physiology throughout life. In pathologic states, the axonal transport of many proteins like tau and ¿-synuclein are thought to be impaired, and yet the mechanisms that move these proteins in axons and deliver them to the synapses is unknown. We have now developed new models where we can directly visualize and quantify the slow axonal transport of these pathology-related proteins in neurons and we hope that increased knowledge of the normal physiology will lead to advances in pathologic mechanisms that operate in these diseases. In the very least, these models will finally allow us to test specific disease- related hypotheses that has not been possible due to our inability to assay this transport modality.