Alpha-synuclein Regulates Dopamine Transporter Functions

多巴胺(DA)转运体(DAT)活性改变与帕金森病有关。误会 DAT突变与成人早发性帕金森病和进行性帕金森病直接相关 多巴胺能神经退行性变。增加的α-突触核蛋白，DAT的蛋白质伙伴，也是 与帕金森病和其他神经退行性疾病有牵连。超过80%的患者 患有长期帕金森病的人会发展成痴呆。α-突触核蛋白基因在 人类参与了帕金森病和/或路易体痴呆的发生。长期的 这项研究的目的是确定α-突触核蛋白过度表达后的DAT功能障碍 在细胞丢失之前，会破坏神经元和网络功能。我们的主要目标是确定 病理进展的潜在机制/S和治疗方案的确定 目标。帕金森病和其他疾病中DA信号功能障碍的病因研究 神经疾病一直是具有挑战性的，因为DAT调节时空 DA传递的调节特征：1)吸收释放的DA；2)自发 DA神经元的放电活动；3)非囊泡性DA的释放(外流)。因此，至关重要的是 首先在单个神经元上剖析这些功能的病理规律，然后确定 疾病状态下相互关联的功能变化。我们的初步数据和公布的数据 提示DAT和α-突触核蛋白之间存在双向相互作用，其中仅 α-突触核蛋白在神经细胞膜上的存在使其重新聚集到细胞膜上。我们发现 膜招募的α-突触核蛋白直接与DAT相互作用，改变DAT的离子偶联 增加向内去极化的Na+电流，抑制DAT介导的DA摄取，增加 多巴胺能神经元钙尖峰的幅度和持续时间并导致多巴胺的7倍增加 外流导致DA循环减少。这些都有效地挑战了突触的调节 DA水平在短期内表现为神经元的完整性，长期表现为神经元的完整性。我们的试点数据表明 问题会迅速扩展到蜂窝活动和网络功能的级别。总而言之， 这些数据支持最重要的假设，即DA神经元中α-突触核蛋白增加 通过DAT和钙依赖机制增加DA神经元的放电活动和DA外流 导致多巴胺传递和神经元通讯中断。要解决这个问题 假设，我们将使用分子、药理学和电生理方法 特别强调多巴胺的神经化学和分子机制 神经传递。

Altered dopamine (DA) transporter (DAT) activity is implicated in Parkinson disease. Missense DAT mutations are directly associated with adult early-onset Parkinsonism and progressive dopaminergic neurodegeneration. Increased α-synuclein, a protein partner of DAT, is also implicated in Parkinson disease and other neurodegenerative diseases. Over 80% of patients with longstanding Parkinson disease will develop dementia. Multiplication of α-synuclein gene in human is involved in the development of PD and/or dementia with Lewy bodies. The long-term goal of this study is to determine how DAT dysfunction following α-synuclein overexpression disrupts neuronal and network function, prior to cell loss. Our primary objective is to determine the underlying mechanism/s of the progression of pathology and identification of therapeutic targets. Determining the etiology of DA signaling dysfunction in Parkinson disease and other neurological disorders have been challenging as DAT regulates the spatiotemporal characteristics of DA transmission by regulating: 1) uptake of released DA, 2) spontaneous firing activity of DA neurons and 3) non-vesicular DA release (efflux). Therefore, it is critical to first dissect the pathological regulations of these functions at a single neuron, then determine the interrelated functional changes in the diseased state. Our preliminary and published data suggest there is a bidirectional interaction between DAT and α-synuclein, where the mere existence of DAT at the neuronal membrane recruits α-synuclein to the membrane. We found membrane recruited α-synuclein directly interacts with DAT, alters the ionic coupling of DAT by increasing an inward depolarizing Na+ current, inhibits the DAT mediated DA uptake, increases the magnitude and duration of Ca2+ spikes in DA neurons and causes a 7-fold increase in DA efflux resulting in diminished DA recycling. These effectively challenge the regulation of synaptic DA levels in the short-term and neuronal integrity in the long-term. Our pilot data suggest this problem quickly scales up to the level of cellular activity and network function. Collectively, these data support the overarching hypothesis that increased α-synuclein in DA neurons increases firing activity of DA neurons and DA efflux via a DAT and Ca2+-dependent mechanism leading to disruption of DA transmission and neuronal communication. To address this hypothesis, we will use molecular, pharmacological and electrophysiological approaches with particular emphasis on neurochemical and molecular mechanisms of dopamine neurotransmission.