Regulation of Neuronal Clearance Pathways via Nuclear Calcium Signaling in Alzheimer's Disease

摘要 抑制自体溶酶体系统最近被描述为阿尔茨海默氏症的最早变化之一， 疾病（AD）大脑中的蛋白质，并可能有助于AD的病理学标志：淀粉样蛋白斑块和 导致神经退行性变的神经元Tau缠结。自体溶酶体系统受损， 随后的分子清除的破坏与增加的神经元脆弱性有因果关系， 神经变性我们最近发表的研究表明，转录因子EB的核活性 （TFEB）和许多细胞清除机制，在早老素（PS）缺乏症中大大减弱， 早发性家族性AD（FAD）的主要原因。在我们的初步研究中，我们发现， 钙水平，从而cAMP反应元件结合蛋白（CREB）介导的表达，其 与自体溶酶体途径相关的靶基因是减毒分子的潜在机制， 在PS和Tau突变体中的清除和降低的神经保护。CREB靶基因sestrin的表达 2（sesn 2）在人类AD神经元促进自噬清除和应激条件下的神经元存活。 我们假设PS1和Tau突变体损害Ryanodine受体（RyR）介导的核调控， 钙，促进清除AD大脑中积累的神经毒性蛋白。如果我们假设 正确的，这些研究将确定一种新的途径，推动形成相关的病理标志， 与AD诱导多能干细胞（iPSC）衍生的人前脑神经元和果蝇 将用于评估细胞核钙耗竭和pCREB信号转导减少对分子生物学的影响。 在AD发作和进展期间清除。我们试图评估我们的发现在死后的相关性 早期、中期和晚期AD患者的人脑组织。使用补充模型系统 使我们能够评估因果关系：在表达疾病相关生理水平的人类神经元中， 聚集倾向的蛋白质，并在果蝇，一个模式生物具有较低的复杂性， 比人类基因组冗余，可以遗传操纵和生理老化。整体 本建议的目的是1）了解导致AD中分子清除抑制的机制 脑，和2）确定衰老和AD神经元中神经元清除功能障碍的后果， 促进未来开发增强神经元清除和预防神经变性的干预措施。

Abstract Inhibition of the autolysosomal system has recently been described among the earliest changes in Alzheimer’s disease (AD) brains and likely contributes to the pathological hallmarks of AD: amyloid plaques and neurofibrillary Tau tangles that drive neurodegeneration. Impairment of the autolysosomal system and consequent disruption of molecular clearance are causally linked to increased neuronal vulnerability and neurodegeneration. Our recently published studies show that nuclear activity of the transcription factor EB (TFEB) and many cellular clearance mechanisms, are greatly attenuated in Presenilin (PS) deficiency, which is the leading cause for early onset familial AD (FAD). In our preliminary studies, we find that a decrease of nuclear calcium levels and consequently cAMP response element-binding protein (CREB)-mediated expression of its target genes associated with the autolysosomal pathway is the underlying mechanism for attenuated molecular clearance and decreased neuroprotection in PS and Tau mutants. Expression of the CREB-target gene sestrin 2 (sesn2) in human AD neurons promotes autophagic clearance and neuronal survival under stress conditions. We hypothesize that PS1 and Tau mutants impair Ryanodine Receptor (RyR)-mediated control of nuclear calcium, which promotes clearance of neurotoxic proteins that accumulate in the AD brain. If our hypothesis is correct, these studies will identify a novel pathway that drives formation of the pathological hallmarks associated with AD. Induced pluripotent stem cell (iPSC)-derived human forebrain neurons and Drosophila melanogaster will be used to assess the impact of nuclear calcium depletion and reduced pCREB signaling in molecular clearance during AD onset and progression. We seek to assess the relevance of our findings in postmortem human brain tissues from patients with early, mid and advanced AD. The use of complementary model systems allows us to assess causality: in human neurons that express physiological levels of disease-associated, aggregation-prone proteins, and in Drosophila melanogaster, a model organism with less complexity and redundancy than the human genome that can be genetically manipulated and physiologically aged. The overall goal of this proposal is 1) to understand the mechanisms leading to inhibition of molecular clearance in AD brains, and 2) to identify consequences of functional failure of neuronal clearance in aging and AD neurons to facilitate future development of interventions enhancing neuronal clearance and prevent neurodegeneration.