Synaptic vesicle changes in synucleinopathies

本研究的中心目标是量化突触囊泡（SV）池和组成随年龄增长和阿尔茨海默病相关痴呆（如路易体痴呆和帕金森病）的变化。sv介导突触的神经递质释放。SV蛋白的丰度和均匀大小使广泛的生化研究成为可能，约15%的SV蛋白与中枢神经系统疾病有关，其中许多与阿尔茨海默病相关的痴呆和帕金森病有关。然而，目前还没有研究分析SV亚型，这些亚型是由它们的水泡神经递质转运体定义的，也没有研究分析SV组成或池随着年龄的增长以及帕金森病和阿尔茨海默病相关痴呆（如路易体痴呆）的变化。大多数SV蛋白丰度较低，每个SV的拷贝数<1。这表明SV的分子和功能多样性，需要对SV池和组成进行彻底的机制分析。α-突触核蛋白（αSyn）以sv结合状态和胞浆状态存在，在这两个池之间进行动态平衡交换。sv结合αSyn介导其在突触上的生理功能。αSyn聚集是帕金森病、路易体痴呆和其他阿尔茨海默病相关痴呆的病理标志，αSyn聚集的很大一部分发生在突触前钮扣。病理已被认为与αSyn：脂质相互作用的改变有关，一些SV蛋白与帕金森病、路易体痴呆和其他阿尔茨海默病相关痴呆有关。因此，SV脂质或蛋白质的变化可能改变αSyn与SV的结合。假设αSyn的SV结合减少是αSyn相关病理的沉淀因素，SV数量、蛋白质和/或脂质组成的变化是αSyn结合减少的原因。在我们强有力的初步数据的指导下，我们发现在两种帕金森病小鼠模型以及帕金森病和路易体痴呆患者的脑组织中αSyn的SV结合减少，以及人源化αSyn小鼠模型中SV密度的年龄依赖性降低，这一假设将在两个特定目的上得到验证：1)确定突触囊泡数量和池的变化，2)确定SV组成的变化。该研究有望系统地了解SV池和组成在衰老过程中以及在帕金森病、路易体痴呆等阿尔茨海默病相关痴呆中的变化，为进一步深入机制研究奠定基础。这项工作是创新的，因为它将在衰老和α syn相关病理过程中生成不同神经递质亚型的SVs的高分辨率地图。这项工作意义重大，因为它(1)首次确定了SV组成在衰老过程中的变化，(2)首次确定了SV亚型的组成，(3)对帕金森病、路易体痴呆和其他阿尔茨海默病相关痴呆具有重要意义，(4)可能为路易体痴呆和帕金森病等阿尔茨海默病相关痴呆的细胞类型特异性易感性提供线索。

The central objective of this proposal is to quantify changes in synaptic vesicle (SV) pools and composition over aging and in Alzheimer's Disease Related Dementias such as Lewy body dementia and Parkinson’s dis-ease. SVs mediate neurotransmitter release at the synapse. Their abundance and uniform size have enabled extensive biochemical studies, and ~15% of SV proteins have been linked to CNS diseases, with numerous of them in Alzheimer's Disease Related Dementias and Parkinson’s disease. Yet, no study has analyzed SV sub-types, defined by their vesicular neurotransmitter transporter, or changes in SV composition or pools with aging and in Parkinson’s disease and Alzheimer's Disease Related Dementias such as Lewy body dementia. Most SV proteins are low abundant, with a copy number of <1 per SV. This suggests molecular and functional SV diversity, necessitating a thorough and mechanistic analysis of SV pools and composition. α-Synuclein (αSyn) exists in a SV-bound and a cytosolic state, exchanging between these pools in a dynamic equilibrium. SV-bound αSyn mediates its physiological functions at the synapse. Aggregation of αSyn is a pathological hallmark of Parkinson’s disease, Lewy body dementia and other Alzheimer's Disease Related Dementias, and a large fraction of αSyn aggregates occurs in presynaptic boutons. Pathology has been suggested to be associated with altered αSyn:lipid interactions, and several SV proteins are linked to Parkinson’s disease, Lewy body dementia and other Alzheimer's Disease Related Dementias. Thus, changes in SV lipids or proteins could alter binding of αSyn to SVs. The hypothesis is that reduced SV-binding of αSyn is a precipitating factor for αSyn-linked pathology, and that changes in SV numbers, protein and/or lipid composition account for the reduction in αSyn binding. Guided by our strong preliminary data, revealing reduced SV-binding of αSyn in two Parkinson’s disease mouse models and in brain tissue of Parkinson’s disease and Lewy body dementia patients in addition to an age-dependent reduction of SV density in our humanized αSyn mouse model, this hypothesis will be tested in two specific aims: 1) Determine changes in synaptic vesicle numbers and pools, and 2) Determine changes in SV composition. The study is expected to provide a systematic understanding of the changes in SV pools and composition during aging and in Parkinson’s disease, Lewy body dementia and other Alzheimer's Disease Related Dementias, which lays the foundation to dive further into mechanistic studies. This work is innovative because it will generate high-resolution maps of SVs of different neurotransmitter subtypes over the course of aging and αSyn-linked pathology. The work is significant because it (1) determines for the first time changes in SV composition during aging, (2) determines for the first time the composition of SV subtypes, (3) has important implications for Parkinson’s disease, Lewy body dementia and other Alzheimer's Disease Related Dementias, (4) may provide clues towards cell-type specific vulnerability in Alzheimer's Disease Related Dementias such as Lewy body dementia and in Parkinson’s disease.