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（LB）背后的机械病理生物学事件-一种影响超过一百万美国人的认知障碍痴呆症。LB痴呆中的一个既定分子参与者是小突触前蛋白α-突触核蛋白。在大量的证据中，α-突触核蛋白的基因组倍增和突变见于患有这些疾病的家族中;长期以来，人们一直认为理解导致LB痴呆中α-突触核蛋白介导的毒性的机制事件是至关重要的。十多年来，该领域的主要焦点一直是破译α-突触核蛋白的正常功能，最终目标是理解向病理状态的转变。 然而，尽管付出了相当大的努力，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因素仍然难以捉摸。我们的建议的基础是一系列的试点实验，我们发现了α-突触核蛋白的两个功能伙伴的新作用，我们假设这些关联的异常是LB痴呆的最初病理触发因素。我们和其他人以前的工作帮助形成了一个共识，即α-突触核蛋白是神经递质释放的生理衰减剂，尽管潜在的机制事件尚不清楚。在这些先前的研究中，我们提出了一个模型，其中α-syn组织成生理上束缚突触囊泡（SV）的高阶多聚体-导致SV动员，SV回收减少，因此，神经递质释放。在新的初步实验中，我们发现了另外两种突触前蛋白--VAMP 2和突触蛋白--在帮助α-突触核蛋白减弱神经传递中的新作用。最终，我们的数据引导我们建立了一个工作模型，其中突触蛋白和VAMP 2在执行α-突触核蛋白功能中发挥顺序作用。这一模式的原则将在目标1/2中得到检验。此外，该领域的一个新兴观点是，生理关联的破坏可能允许游离α-突触核蛋白单体聚集-触发病理-并且这可能是疾病中最早的病理事件之一;然而，缺乏体内证据。利用我们对功能性α-突触核蛋白伴侣的发现，目标2/3将询问这些关联的破坏是否也可能加速LB痴呆的细胞和动物模型的病理学。我们的目标是：目标#1：确定VAMP 2在α-突触核蛋白介导的突触衰减中的作用。目的#2：确定突触蛋白在α-突触核蛋白介导的突触衰减和病理学中的作用。目的#3：检验破坏生理关联可在体内触发α-突触核蛋白病理学的假设。完成后，我们的研究将揭示α-突触核蛋白正常功能的重要线索，以及在这些毁灭性疾病中引发痴呆和认知障碍的事件。

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.