Pathophysiologic roles of alpha-synuclein at the synapse

这项提案的总体目标是澄清路易体痴呆症(路易体痴呆)背后的机械性病理生物学事件-一种影响100多万美国人的伴有认知障碍的痴呆疾病。在LB型痴呆中，一个公认的分子参与者是小突触前蛋白α-突触核蛋白。在大量的相关证据中，α-突触核蛋白的基因组倍增和突变在患有这些疾病的家族中被发现；长期以来，人们已经认识到，了解导致α-突触核蛋白介导的毒性在LB型痴呆中的机制事件是至关重要的。十多年来，该领域的一个主要焦点一直是破译α-突触核蛋白的正常功能，最终目的是了解向病理状态的转变。然而，尽管做出了相当大的努力，α-突触核蛋白正常功能的确切机制以及导致病理性聚集的早期触发机制仍然难以捉摸。我们的建议的基础是一系列的试点实验，在这些实验中，我们发现了α-突触核蛋白的两个功能伙伴的新角色，我们假设这些关联中的异常是LB痴呆的初始病理触发因素。我们和其他人之前的工作帮助形成了一种共识，即α-突触核蛋白是神经递质释放的生理衰减器，尽管潜在的机制尚不清楚。在这些先前的研究中，我们提出了一个模型，其中α-SYN组织成更高阶的多聚体，生理上拴住突触小泡(SV)，导致SV动员、SV再循环减少，从而导致神经递质的释放。在新的试点实验中，我们发现了另外两种突触前蛋白--VAMP2和突触素--在帮助α-突触核蛋白减弱神经传递方面的新作用。最终，我们的数据将我们带到了一个工作模型，在这个模型中，突触素和VAMP2在执行α-突触核蛋白功能方面扮演着连续的角色。这一模型的原理将在AIMS 1/2中得到测试。此外，该领域的一个新兴想法是，生理联系的破坏可能允许自由α-突触核蛋白单体聚集并触发病理-这可能是疾病中最早的病理事件之一；然而，体内证据不足。利用我们在功能性α-突触核蛋白伙伴方面的发现，AIMS 2/3将询问这些关联的破坏是否也可能加速细胞和动物模型的LB痴呆的病理。我们的目标是：目标1：确定VAMP2在α-突触核蛋白介导的突触衰减中的作用。目的#2：确定突触素在α-突触核蛋白介导的突触衰减和病理中的作用。目的#3：验证破坏生理联系可在体内触发α-Synuclein病理的假说。完成后，我们的研究应该会揭示α-突触核蛋白的正常功能以及在这些毁灭性疾病中引发痴呆症和认知障碍的事件的重要线索。

The overall goal of this proposal is to clarify mechanistic pathobiological events underlying Lewy body (LB) dementias – a dementing illness with cognitive impairment that affects more than a million Americans. An established molecular player in LB dementia is the small presynaptic protein α-synuclein. Amongst a plethora of incriminating evidence, genomic multiplications and mutations of α-synuclein are seen in families harboring these diseases; and it has been long recognized that understanding the mechanistic events that lead to α-synuclein-mediated toxicity in LB dementia is of utmost importance. For over a decade, a primary focus in the field has been to decipher the normal function of α-synuclein, with the ultimate goal of understanding transition to pathologic states. However, despite considerable effort, the precise mechanisms underlying the normal function of α-synuclein, and early triggers leading to pathologic aggregation remain elusive. The basis of our proposal is a series of pilot experiments, where we uncovered novel roles for two functional partners of α-synuclein, and we hypothesize that abnormalities in these associations are the initial pathologic triggers for LB dementias. Previous work from us and others has helped shape a consensus that α-synuclein is a physiologic attenuator of neurotransmitter release, though underlying mechanistic events are unclear. In these previous studies, we proposed a model where α-syn organizes into higher-order multimers that physiologically tether synaptic vesicles (SVs) – leading to a diminution in SV-mobilization, SV-recycling, and consequently, neurotransmitter release. In new pilot experiments, we discovered novel roles for two other presynaptic proteins – VAMP2 and synapsin – in helping α-synuclein attenuate neurotransmission. Eventually, our data led us to a working model where synapsin and VAMP2 play sequential roles in executing α-synuclein function. Tenets of this model will be tested in Aims 1/2. Additionally, an emerging idea in the field is that disruption of physiologic associations might allow free α-synuclein monomers to aggregate – triggering pathology – and that this might be one of the earliest pathologic events in disease; however, in vivo evidence is lacking. Leveraging our discoveries on functional α-synuclein partners, Aims 2/3 will ask if a disruption of these associations might also accelerate pathology in cellular and animal models of LB dementias. Our aims are: Aim #1: Identify the role of VAMP2 in α-synuclein mediated synaptic attenuation. Aim #2: Identify the role of synapsin in α-synuclein mediated synaptic attenuation and pathology. Aim #3: Test the hypothesis that disrupting physiologic associations can trigger α-synuclein pathology in vivo. Upon completion, our studies should reveal vital clues into the normal function of α-synuclein, as well as events that trigger dementia and cognitive impairment in these devastating illnesses.