ProSAAS-mediated neuroprotective mechanisms in Alzheimer's and Parkinson's diseases: the role of secretory chaperones in neurodegeneration

人口统计因素预测，美国医疗保健系统将在 在接下来的几十年里，由于老年神经退行性疾病患者的涌入。最多的 据预测，阿尔茨海默氏症和帕金森氏症(AD和PD)是其中的常见病 到2040年，数以百万计的美国人。这两种疾病都涉及到越来越多的异常大脑。 蛋白平衡，与大量神经细胞死亡有关。多种胞浆和分泌性脑 伴侣有助于维持这些和其他神经退行性变患者的神经元蛋白平衡 蛋白质病；在这些疾病中，分泌伴侣prosaas有许多引人注目的特征。ProSAAS是 仅在神经元和内分泌细胞中表达；因为它通过调节的分泌进行运输 途径中，它集中在致密的核心突触颗粒中，并在神经元中释放 活动。ProSAAS已被五个蛋白质组学小组确定为潜在的生物标志物 神经退行性疾病，发现与黑质聚集蛋白有关 帕金森病患者以及阿尔茨海默病患者的淀粉样斑块。ProSAAS阻止 Abeta和α突触核蛋白在高度亚化学计量比下的聚集，并且两者 内源性过表达和外源性应用降低了Abeta和α突触核蛋白在原代神经元和细胞系中的神经毒性。最近，我们已经证明了ProSAAS 在α-突触核蛋白过度表达的大鼠模型中，过度表达在体内也具有功能保护作用。 在拟议的工作中，我们将调查prosa可能通过的共同机制 保护神经元免受神经毒性聚集蛋白和多肽的影响，如α-突触核蛋白和A-β 1-42。我们假设分泌的ProSAAS隔离物是细胞外的细胞毒性低聚物和纤维， 减少它们在突触处的浓度。其次，我们假设内吞的ProSAAS起作用 细胞内类似地隔离细胞毒蛋白，加速它们的降解。使用培养的 原代海马和黑质神经元，我们将确定ProSAAS是否参与 细胞内和细胞外Abeta和α突触核蛋白的隔离。我们还将确定 ProSAAS的细胞内表达是否具有细胞保护优势 胞外加成。最后，我们将评估内吞的proSAAs是否加速细胞内 Abeta和α-突触核蛋白的降解。 同时，我们将扩大我们激动人心的体内结果，以包括预制的α-突触核蛋白 梳理黑质和纹状体中prosas潜在作用部位的纤维模型。使用快速扫描循环伏安法评估的多巴胺稳态的退变前变化将是 与ProSAAS介导的神经保护相关。类似地，AD的小鼠模型将用于 检测proSAAS AAV介导的高表达和低表达对淀粉样蛋白发育的影响 病理学。总的来说，这些实验将提供对生化机制的洞察。 潜在的强大的细胞保护作用的prosaas伴侣蛋白。

Demographic considerations predict an overwhelming burden on the U.S. health care system within the next few decades due to an influx of elderly patients with neurodegenerative disease. The most prevalent of these, Alzheimer's and Parkinson's diseases (AD and PD), are predicted to affect tens of millions of Americans by 2040. Both of these diseases involve progressively more aberrant brain proteostasis, associated with massive neuronal cell death. A variety of cytosolic and secreted brain chaperones contribute to maintenance of neuronal proteostasis in these and other neurodegenerative proteinopathies; of these, the secretory chaperone proSAAS has many compelling features. ProSAAS is expressed only in neurons and endocrine cells; because it traffics through the regulated secretory pathway, it becomes concentrated within dense core synaptic granules, and is released during neuronal activity. ProSAAS has been identified by five proteomics groups as a potential biomarker in neurodegenerative disease, and is found associated with aggregated proteins in the substantia nigra of PD patients as well as with amyloid plaques in AD‐affected individuals. ProSAAS blocks the aggregation of both Abeta and alpha synuclein at highly substoichiometric ratios, and both endogenous overexpression as well as exogenous application reduce Abeta‐ and alpha synuclein‐mediated neurotoxicity in primary neurons and cell lines. Most recently, we have shown that proSAAS overexpression is also functionally protective in vivo in a rat model of alpha‐synuclein overexpression. In the proposed work, we will investigate the likely common mechanisms by which proSAAS protects neurons from neurotoxic aggregating proteins and peptides such as alpha synuclein and Abeta 1‐42. We hypothesize that secreted proSAAS sequesters cytotoxic oligomers and fibrils extracellularly, reducing their concentrations at the synapse. Secondly, we hypothesize that endocytosed proSAAS acts intracellularly to similarly sequester cytotoxic proteins, speeding their degradation. Using cultured primary hippocampal and nigral neurons, we will determine whether proSAAS is involved in intracellular and extracellular Abeta and alpha synuclein sequestration. We will also determine whether intracellular expression of proSAAS confers a cytoprotective advantage compared to extracellular addition. Lastly we will assess whether endocytosed proSAAS accelerates the intracellular degradation of Abeta and alpha synuclein. In parallel, we will expand our exciting in vivo results to include the alpha‐synuclein preformed fibril model to tease apart the potential sites of action of proSAAS in substantia nigra and striatum. Pre‐degenerative changes in dopamine homeostasis, assessed using fast‐scan‐cyclic‐voltammetry, will be correlated with proSAAS‐mediated neuroprotection. Similarly, a mouse model of AD will be used to test the effects of proSAAS AAV‐mediated over‐ and underexpression on the development of amyloid pathology. Collectively, these experiments will provide insight into biochemical mechanisms underlying the potent cytoprotective effects of the proSAAS chaperone protein.