Alpha-Synuclein, PUFA and Membrane Vesicles in Health and Parkinson's Disease

描述（由申请人提供）：帕金森病是第二种最常见的神经退行性疾病，以进行性功能障碍和黑质多巴胺能神经元丢失为特征。这种主要特征伴随着多巴胺能神经元及其过程（路易体和神经突）中蛋白质内含物的积累，其主要成分是α-突触核蛋白（aS）。aS具有7个类似于载脂蛋白的脂质结合α-螺旋结构域的重复序列，并且其与磷脂膜的结合显著改变了其二级结构。我们最近：a）发现了aS与脂肪酸（FA）结合蛋白（FABP）家族的同源性; B）发现了纯的aS可逆地结合游离FA; c）在多巴胺能细胞、正常小鼠和人脑中检测到了一组高度可溶的、脂质相关的aS寡聚体，并且在PD和DLB脑中检测到了升高的水平; d）显示活的中脑神经元暴露于多不饱和脂肪酸增强可溶性α 5寡聚体的形成，而暴露于饱和脂肪酸延迟可溶性α 5寡聚体的形成;和e）在α S过表达的神经元中证实了内源性PUFA水平和膜流动性增加，而在α S敲除小鼠中相反。基于这些发现，我们假设，在细胞质的水和膜磷脂隔室中，aS通常与FA相互作用，并有助于调节脂质组成（特别是PUFA含量）的各个方面，从而调节膜特性，并且aS-FA相互作用有助于调节aS的寡聚化，从而可以启动aS组装成第一可溶性寡聚体，然后是不溶性寡聚体。为了追求这个关于aS功能和功能障碍的分子假设，我们现在提出了一系列相互关联的目标。1)试图证明改变内源性PUFA水平（例如，在用A6去饱和酶抑制剂处理的细胞中降低或在Zellweger综合征模型小鼠中升高）诱导脑细胞中内源性aS寡聚体的相应减少或增加。2）。研究α S-FA相互作用对活细胞膜囊泡的形成、超微结构和生物物理性质的影响。3)为了确定PUFA-ctS相互作用是否以及如何影响到目前为止记录的aS的一个离散的生化功能：抑制磷脂酶D。我们的重点是在脂质代谢和膜囊泡的形成/稳定性的关键作用，从一组新的观察两个主要研究人员。此外，它是强烈支持最近的无偏见的遗传筛选在AS表达酵母或果蝇，涉及的功能，在脂质调节和膜运输的aS。这项资助的新发现应该同时阐明aS的生理学及其病理性寡聚化的最早阶段，以及随之而来的治疗见解。

DESCRIPTION (provided by applicant): Parkinson's disease, the second most common neurodegenerative disorder, is marked by progressive dysfunction and loss of nigral dopaminergic neurons. This cardinal feature is accompanied by the accumulation of protein inclusions in dopaminergic neurons and their processes (Lewy bodies and neurites), the major constituent of which is a-synuclein (aS). aS has 7 repeats resembling the lipid-binding a-helical domains of apolipoproteins, and its binding to phospholipid membranes markedly alters its secondary structure. We have recently: a) discovered homologies of aS with the fatty acid (FA) binding protein (FABP) family; b) found that pure aS binds free FAs reversibly; c) detected a pool of highly soluble, lipid-associated aS oligomers in dopaminergic cells, normal mouse and human brains and, at elevated levels, in PD and DLB brains; d) shown that exposure of living mesencephalic neurons to polyunsaturated FAs enhances ~ and to saturated FAs retards ~ the formation of soluble aS oligomers; and e) documented increased endogenous PUFA levels and membrane fluidity in aS-overexpressing neurons, and the opposite in aS knock-out mice. Based on these findings, we hypothesize that aS normally interacts with FAs in both the aqueous and membrane-phospholipid compartments of the cytoplasm and helps regulate aspects of lipid composition (particularly PUFA content) and thus membrane properties, and that aS-FA interactions help regulate the oligomerization of aS and can thus initiate aS assembly into first soluble and then insoluble oligomers. To pursue this molecular hypothesis about aS function and dysfunction, we now propose a series of interrelated goals. 1) To attempt to prove that altering endogenous PUFA levels (e.g., lowered in cells treated with a A6 desaturase inhibitor or elevated in mice modeling Zellweger's syndrome) induces corresponding decreases or increases in endogenous aS oligomers in brain cells. 2). To examine the effects of aS-FA interactions on the formation, ultrastructure and biophysical properties of membrane vesicles in living cells. 3) To ascertain whether and how PUFA-ctS interactions affect the one discrete biochemical function of aS documented to date: inhibiting Phospholipase D. Our focus on a key role for aS in lipid metabolism and membrane vesicle formation/stability derives from a novel set of observations made by the two principal investigators. Moreover, it is strongly supported by recent unbiased genetic screens in aS-expressing yeast or Drosophila that implicated a function of aS in lipid regulation and membrane trafficking. New findings emanating from this grant should simultaneously shed light on the physiology of aS and the earliest steps in its pathological oligomerization, with attendant therapeutic insights.