Tau-PI3Kalpha Complex in Regulation of PI3K/Akt-dependent Neuronal Function and Survival

项目摘要 包括阿尔茨海默病在内的Tau病理是最普遍和复杂的神经退行性疾病 到2050年，全球老龄化人口可能达到1.15亿（6），但没有治疗药物来治疗这一问题。 疾病，除了最近批准的有争议的药物（7）。虽然细胞内神经细胞的形成 在皮质和海马区，来自过度磷酸化tau蛋白的神经纤维缠结（NFT）是一个关键， tau病理学的病理标志，过度磷酸化tau如何影响 神经元中缺乏存活信号。最近，我们发现PI3K/Akt存活信号通路 非神经元型微管相关蛋白4（MAP 4）直接与神经元相互作用， 通过其微管结合域（MTBD）与PI3K结合（9）。PI3K β与MAP4的相互作用控制PI3K β的表达。 与PI3K β活化、PI3，4，5P3生成和 Akt激活（9）。结合PI3K β的MAP4的MTBD显示出与微管蛋白惊人的高同源性。 神经元微管相关蛋白tau和MAP 2的结合域，刺激了以下假设： tau和MAP 2替代MAP 4控制神经元中的PI3K/Akt存活信号传导。我们的初步数据显示 在原代神经元、诱导多能干细胞衍生的神经元和 神经元细胞系。siRNA介导的tau敲低阻断了胰岛素刺激的Akt活化。 我们假设tau沿着轴突和树突中的微管支撑PI 3 K以控制生长因子 刺激神经元的PI3K/Akt存活信号。tau蛋白过度磷酸化及其聚集增加 在阿尔茨海默病的发展过程中， 在生长因子刺激的PI3K/Akt信号传导的损失中，PI3K/Akt信号传导对神经元细胞存活和功能至关重要。 建议研究的重点是建立和理解tau蛋白在PI3K/Akt信号转导中的作用机制 并定义tau蛋白中的PI3K β相互作用位点。PI3K β和tau之间的相互作用将用于定义 在tau的MTBD中的PI3K相互作用位点，并研究这些位点是否与致病突变体一致 以及tau蛋白MTBD中的过度磷酸化位点。我们将定义tau损失对空间分布的影响， PI3K β与轴突和树突中活化受体的共定位和相互作用，以及对生长的影响 因子刺激PI3，4，5P3产生和Akt激活。这将通过一个系统的 研究表达对PI3K β结合缺陷的突变tau蛋白的影响， 细胞渗透性肽对空间PI3K/Akt信号传导和神经元存活的PI3K β-tau相互作用。

PROJECT SUMMARY Tau pathologies including Alzheimer’s disease are the most prevalent and complex neurodegenerative diseases of aging that will likely reach 115 million globally by 2050(6) yet, there are no therapeutic drugs to treat this disease, except a controversial recently approved drug(7). Though the formation of intracellular neurofibrillary tangles (NFTs) from the hyperphosphorylated tau protein in the cortical and hippocampal regions is a key pathological hallmark of tau pathologies, the precise mechanisms of how hyperphosphorylated tau impact survival signaling in neurons is lacking. Recently we have shown that the PI3K/Akt survival signaling pathway is controlled by the non-neuronal type microtubule-associated protein 4 (MAP4) that directly interacts with PI3K via its microtubule-binding domain (MTBD)(9). The PI3K interaction with MAP4 controls the PI3K association with activated receptor kinases that are required for PI3K activation, PI3,4,5P3 generation, and Akt activation(9). The MTBD of MAP4 that binds PI3K shows strikingly high homology with the microtubule- binding domain of the neuronal microtubule-associated proteins tau and MAP2, stimulating the hypothesis that tau and MAP2 substitute for MAP4 control of PI3K/Akt survival signaling in neurons. Our preliminary data shows the association between tau and PI3K in primary neurons, induced pluripotent stem cells-derived neurons, and a neuronal cell line. The siRNA-mediated knockdown of tau blocked insulin stimulated Akt activation. We hypothesize that tau scaffold the PI3K along microtubules in axons and dendrites to control growth factor stimulated PI3K/Akt survival signaling of neurons. Increased tau hyperphosphorylation and its aggregation during Alzheimer’s disease progression impairs the spatial organization of PI3K along microtubules resulting in loss of growth factor stimulated PI3K/Akt signaling that is critical for neuronal cell survival and function. The focus of proposed study is to establish and understand mechanistically tau’s role in the PI3K/Akt signaling and define the PI3K interaction sites in tau. The interaction between PI3K and tau will be used to define the interaction sites for PI3K in the MTBD of tau and investigate if these sites coincide with pathogenic mutants and hyperphosphorylation sites in the MTBD of tau. We will define the effect of tau loss on spatial distribution, co-localization and interaction of PI3K with activated receptors in axons and dendrites, and effect on growth factor stimulated PI3,4,5P3 generation and Akt activation. This will be further substantiated by a systemic investigation of the impact of expressing mutant tau that is deficient on PI3K binding and the disruption of PI3K-tau interaction by cell permeable peptides on spatial PI3K/Akt signaling and survival of neurons.