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

项目概要 包括阿尔茨海默氏病在内的 Tau 蛋白病理是最普遍、最复杂的神经退行性疾病 到 2050 年，全球老龄化人口可能将达到 1.15 亿人(6)，但目前还没有治疗药物可以治疗这一问题 疾病，但最近批准的有争议的药物除外(7)。虽然细胞内神经原纤维的形成 皮质和海马区过度磷酸化 tau 蛋白的缠结 (NFT) 是关键 tau 病理学的病理标志，过度磷酸化 tau 影响的精确机制 神经元中缺乏生存信号。最近我们发现 PI3K/Akt 生存信号 该通路由直接相互作用的非神经元型微管相关蛋白 4 (MAP4) 控制 通过其微管结合域 (MTBD) 与 PI3Kα 结合 (9)。 PI3K 与 MAP4 的交互控制 PI3K 与 PI3Kα 激活、PI3,4,5P3 生成和所需的激活受体激酶相关 Akt 激活(9)。结合 PI3Kα 的 MAP4 的 MTBD 与微管显示出惊人的高度同源性 神经元微管相关蛋白 tau 和 MAP2 的结合域，激发了以下假设： tau 和 MAP2 替代 MAP4 对神经元中 PI3K/Akt 存活信号的控制。我们的初步数据显示 原代神经元、诱导多能干细胞衍生的神经元中 tau 和 PI3K 之间的关联，以及 神经元细胞系。 siRNA 介导的 tau 蛋白敲除阻断了胰岛素刺激 Akt 的激活。 我们假设 tau 蛋白沿着轴突和树突中的微管支撑 PI3K 来控制生长因子 刺激神经元的 PI3K/Akt 存活信号传导。 tau 过度磷酸化及其聚集增加 在阿尔茨海默病进展过程中，PI3Kα沿着微管的空间组织受到损害，从而导致 生长因子刺激的 PI3K/Akt 信号传导的丧失对神经元细胞的存活和功能至关重要。 拟议研究的重点是从机制上建立和理解 tau 在 PI3K/Akt 信号传导中的作用 并定义 tau 中的 PI3K 相互作用位点。 PI3K 和 tau 之间的相互作用将用于定义 tau 的 MTBD 中 PI3K 的相互作用位点，并研究这些位点是否与致病突变体一致 tau 的 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 与轴突和树突中激活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 生成和 Akt 激活。这将通过系统的进一步证实 研究表达突变 tau 对 PI3Kα 结合缺陷的影响以及对 PI3Kα 结合的破坏 细胞渗透性肽对空间 PI3K/Akt 信号传导和神经元存活的 PI3Kα-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.