Understanding the Mechanism of Pathological alpha-Synuclein Transmission

α-突触核蛋白病是神经退行性疾病的一个子集，包括帕金森病（PD）， 路易体痴呆（DLB）和多系统萎缩（MSA）（1），其特征在于： 神经元或神经胶质细胞中错误折叠的α-突触核蛋白（α-syn）蛋白的异常积累。新出现的证据 表明病理性α-syn的细胞-细胞传递实质上导致神经变性。 然而，α-syn传输的分子机制知之甚少。我们已经确定了三个 与α-syn PFF强结合的跨膜蛋白：（i）淋巴细胞活化基因-3（LAG 3），（ii） 淀粉样β受体样蛋白1（APLP 1），和（iii）neurexin 1-β。LAG 3是一种重要的受体，介导 α-syn PFF的内化;然而，大量的α-syn PFF与LAG 3-/-（敲除）神经元结合，表明 未鉴定的候选物（例如APLP 1）与病理性α-syn结合，并促进内化。 在这个提议中，我们假设：（i）APLP 1是一个重要的受体，介导α-syn传递;（ii） APLP 1-LAG 3复合物协同介导α-syn传递;（iii）APLP 1、LAG 3或APLP 1-LAG 3的耗竭 LAG 3复合物可减轻α-syn转基因小鼠的神经退行性变。因此，委员会认为， 实验提出了表征APLP 1，LAG 3和AL复合物在介导的作用， α-突触核蛋白病的发病机制，在细胞间传播模型和α-syn转基因 小鼠模型在患有α-突触核蛋白病的两种小鼠模型中进行的实验将通过以下研究进行补充： 细胞和无细胞实验，从而允许破译的相互作用中的每个扩散步骤， APLP 1、LAG 3或AL与病理性α-syn的复合物。这些研究的成功完成将 大大提高了我们对α-syn细胞间传递的分子机制的理解， 受体，通过：（i）确定APLP 1作为一种新的受体，介导α-syn传播，（ii）了解 AL复合物对介导α-syn PFF的结合和内化的协同作用，（iii）提供 抗LAG 3抗体作为PD及相关疾病潜在治疗药物的基本初步评价 α-突触核蛋白病，以及（iv）了解APLP 1，LAG 3和AL复合物在介导 α-syn转基因小鼠的神经变性。

α-Synucleinopathies are a subset of neurodegenerative diseases, including Parkinson's disease (PD), dementia with Lewy Bodies (DLB) and multiple system atrophy (MSA) (1), which are characterized by abnormal accumulation of misfolded α-synuclein (α-syn) protein in neurons or glial cells. Emerging evidence suggests that the cell-to-cell transmission of pathological α-syn substantially cause neurodegeneration. However, the molecular mechanism of α-syn transmission is poorly understood. We have identified three transmembrane proteins that strongly bind with α-syn PFF: (i) lymphocyte activation gene-3 (LAG3), (ii) amyloid β precursor-like protein 1 (APLP1), and (iii) neurexin 1-β. LAG3 is an essential receptor, mediating internalization of α-syn PFF; however, substantial α-syn PFF binds to LAG3-/- (knockout) neurons, suggesting that a unidentified candidate(s) (e.g. APLP1) binds with pathologic α-syn, and facilitate the internalization. In this proposal, we hypothesize: (i) APLP1 is an essential receptor, that mediates α-syn transmission; (ii) APLP1-LAG3 complex synergistically mediates α-syn transmission; (iii) depletion of APLP1, LAG3, or APLP1- LAG3 complex, can reduce α-syn-induced neurodegeneration of α-syn transgenic mice. Accordingly, experiments are proposed to characterize the roles of APLP1, LAG3 and the AL complex in mediating the pathogenesis of α-synucleinopathies, in cell-to-cell transmission models and the α-syn transgenic mouse model. Experiments in two mice models with α-synucleinopathies, will be complemented by studies in cells and cell-free experiments, thus allowing the deciphering of each spreading step in the interaction of APLP1, LAG3, or the AL complex with pathologic α-syn. The successful completion of these studies will greatly enhance our understanding of the molecular mechanisms of α-syn cell-to-cell transmission via receptors, by: (i) identifying APLP1 as a novel receptor that mediates α-syn spreading, (ii) understanding the synergistic effect of the AL complex on mediating binding and internalization of α-syn PFF, (iii) providing essential preliminary evaluation of anti-LAG3 antibody as a potential therapeutic agent against PD and related α-synucleinopathies, and (iv) understanding the roles of APLP1, LAG3, and the AL complex in mediating neurodegeneration of α-syn transgenic mice.