Role of PS1 in neurodegeneration

描述(由申请者提供)：突触功能障碍和A？堆积是阿尔茨海默病(AD)的主要病理特征。大量研究表明，Aç可以以活性依赖的方式产生，这与突触小泡的胞吐作用有关。PS1/g-分泌酶存在于突触终末，我们的初步数据表明，随着突触的活动和钙(Ca~(2+))的内流，PS1/g-分泌酶迅速和可逆地改变其构象。早老素1(Ps1)是γ分泌酶的催化成分，它释放了A？多肽的C-末端，从而决定了A？的数量和将产生的A？种：A？40或更长的、高度纤溶和神经毒性的A？42。然而，控制Ps1/γ-分泌酶裂解位点的精确度和突触局部产生的细胞生物学机制仍不清楚。目前已经报道了几种蛋白水解酶对PS1的磷酸化作用，但其作用机制尚不清楚。目的1确定神经元活性/钙离子诱导的PS1/γ分泌酶的磷酸化是否代表突触中PS1构象和功能的调节机制。此外，我们最近对有无钙的小鼠脑裂解产物的蛋白质组学筛选发现，两种新的PS1相互作用蛋白，突触素1(SYN1)和突触素1(Syt1)，显示出强烈但相反的钙依赖结合PS1的特征。SYN1将突触小泡锚定在肌动蛋白细丝上，但在钙离子诱导SYN1磷酸化后释放它们。Syt1在神经递质释放中起着钙离子感受器的作用。目的2将探讨钙离子内流是否可能作为控制PS1构象和与SYN1和Syt1相互作用的开关。此外，我们将测试PS1与SYN1和SyT1的相互作用是否以一种活动控制的方式调节突触上的PS1/γ分泌酶和APP的处理。目的3验证新发现的PS1与体内突触蛋白相互作用的生理学相关性，以确定它是否在老年人和/或疾病的脑中受到影响，以及这些相互作用是否可以被药理学操纵。本研究将提供PS1构象变化的机制数据，探索PS1与突触囊泡机械蛋白的新的相互作用，并阐明PS1在突触中的新的依赖和独立的作用。理解这些问题非常重要，因为对PS1构象和突触相互作用的操纵可能会转化为新的治疗策略。

DESCRIPTION (provided by applicant): Synaptic dysfunction and Aß accumulation are the key features of Alzheimer's disease (AD) pathology. Numerous studies have shown that Aß can be produced in activity-dependent manner, and this correlates with synaptic vesicle exocytosis. PS1/g-secretase is present at the synaptic terminals, and our preliminary data show that it changes its conformation rapidly and reversibly in concert with synaptic activity and calcium (Ca2+) influx. Presenilin 1 (PS1) is the catalytic component of γ-secretase, which liberates the C-terminus of Aß peptide, and thus determines both amount of Aß and which Aß species will be produced: Aß40 or the longer, highly fibrillogenic and neurotoxic Aß42. However, the cell biological mechanisms that control precision of the PS1/γ-secretase cleavage site and local Aß production at the synapse remains unknown. PS1 phosphorylation by several kinases has been reported; however mechanistic effect of the PS1 phosphorylation remains unclear. Aim 1 will determine whether neuronal activity/Ca2+-induced phosphorylation of PS1/γ-secretase represents the regulatory mechanism of PS1 conformation and function at the synapse. Furthermore, our recent proteomics screen of mouse brain lysates in the presence or absence of calcium identified two novel PS1 interacting proteins, synapsin1 (Syn1) and synaptotagmin1 (Syt1), that showed strong but opposing Ca2+-dependent profiles of binding to PS1. Syn1 anchors synaptic vesicles to actin filaments, but releases them after Ca2+-induced Syn1 phosphorylation. Syt1 acts as Ca2+sensor in neurotransmitter release. Aim 2 will explore whether, Ca2+ influx may function as a switch controlling PS1 conformation and interactions with Syn1 and Syt1. In addition, we will test if PS1 interactions with Syn1 and Syt1 modulate PS1/γ-secretase and APP processing at the synapse in an activity-controlled manner. Aim 3 will validate physiological relevance of the newly found PS1 interaction with synaptic proteins in vivo by establishing if it is affected in aged and/or diseased brain, and whether these interactions can be manipulated pharmacologically. This study will provide mechanistic data for PS1 conformational changes, will explore novel PS1 interactions with synaptic vesicle machinery proteins, and will elucidate novel Aß-dependent and independent role of PS1 at the synapse. Understanding these issues is of high importance because manipulation of the PS1 conformation and synaptic interactions may translate into novel therapeutic strategies.