Tyrosine phosphorylation in Alzheimer's disease

描述（由申请人提供）：阿尔茨海默病（AD）影响75岁以上人群的20%和85岁以上人群的50%。很难识别AD的早期阶段，也没有方法定量跟踪疾病进展。减缓AD或治愈AD的疗法也不存在。AD的神经病理学特征之一是由异常磷酸化的tau蛋白组成的神经元缠结。在tau基因中发现导致年龄相关的神经退行性疾病（例如额颞叶痴呆）的突变，已经导致研究表明（1）异常磷酸化的tau足以引起疾病，以及（2）异常tau引起神经元死亡。此外，AD现在被认为是“tau蛋白病”。为了发现AD和其他tau蛋白病的新生物标志物和治疗方法，确定tau蛋白如何引起疾病至关重要。虽然许多研究人员专注于tau作为微管相关蛋白的众所周知的特性，但我们专注于确定tau的新特性，因为有许多微管相关蛋白与AD无关。我们已经发现tau蛋白与Src家族非受体酪氨酸激酶结合，并被酪氨酸磷酸化。我们还发现，tau蛋白可以上调激酶活性，并且tau蛋白的异常磷酸化和突变形式都可以与Fyn（一种Src家族激酶）更强烈地相关。事实上，其他研究人员已经表明，删除Fyn对神经系统有保护作用， AD小鼠模型。由于tau蛋白是酪氨酸磷酸化的，我们研究了tau蛋白可能作为信号转导蛋白的可能性。我们发现，tau蛋白增强神经元细胞中NGF诱导的MAPK和AP 1活化，tau蛋白在thr 231和tyr 18/tyr 29的磷酸化对于这种新特性至关重要。微管结合没有参与。此外，我们发现tau蛋白与蛋白酪氨酸磷酸酶SHP 2在一个神经生长因子依赖的方式。在本申请中，我们建议使用两种方法研究tau蛋白的酪氨酸磷酸化。在具体目标I中，我们将确定从tau蛋白病小鼠模型中删除Fyn是否会改变模型中的tau病理学和神经元活力。我们还将确定小鼠的行为是否改变。在具体目标II中，我们将研究 异常磷酸化tau的功能。具体而言，我们将研究磷酸化在tau和SHP 2之间的相互作用中的作用以及相互作用的功能意义。在具体目标III中，我们将确定SHP 2是否在AD中被激活。还将在小鼠tau蛋白病模型中研究SHP 2和MAPK活化。这些目标将（1）推进我们对异常磷酸化tau的机制的认识，（2）确定这些机制是否在神经退行性变中发生。异常磷酸化的tau蛋白是神经退行性疾病的最早迹象，我们的研究旨在确定朝着神经病理过程采取的最早步骤。我们的数据将有助于确定疾病治疗的新靶点和跟踪疾病进展的新生物标志物。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) affects 20% of those over the age of 75 and 50% over the age of 85. It is difficult to identify early stages of AD and there are no methods to quantitatively follow disease progression. Therapies to slow AD or to cure AD are also absent. One of the neuropathological features of AD is the neurofibrillary tangles made of abnormally phosphorylated tau protein. The discovery of mutations in the tau gene that cause age-related neurodegenerative diseases, such as frontotemporal dementia, has led to research showing that (1) abnormally phosphorylated tau is sufficient to cause disease and (2) neuronal death is caused by abnormal tau. Moreover, AD is now considered a "tauopathy". To discover new biomarkers and therapeutics for AD and other tauopathies, it is critical to determine how tau causes disease. While many investigators have focused in the well-known property of tau as a microtubule-associated protein, we have focused on identifying new properties for tau, as there are many microtubule-associated proteins that have no connection to AD. We have found that tau associates with Src-family non-receptor tyrosine kinases and is tyrosine phosphorylated. We have also found that tau can up-regulate kinase activity and that both abnormally phosphorylated and mutated forms of tau can associate more strongly with Fyn, a Src-family kinase. In fact, other investigators have shown that deleting Fyn is neuroprotective for AD in mouse models. Because tau is tyrosine phosphorylated, we investigated the possibility that tau might function as a signal transduction protein. We found that tau potentiated NGF-induced MAPK and AP1 activation in neuronal cells and that phosphorylation of tau at thr231 and tyr18/tyr29 were critical for this new property. Microtubule binding was not involved. In addition, we found that tau associated with the protein tyrosine phosphatase SHP2 in an NGF-dependent manner. In this application, we propose to investigate the tyrosine phosphorylation of tau using two approaches. In Specific Aim I, we will determine if deletion of Fyn from a tauopathy mouse model alters the tau pathology and neuronal viability in the model. We will also determine if the behavior of the mouse is altered. In Specific Aim II, we will investigate the function of abnormally phosphorylated tau. Specifically, we will investigate the role of phosphorylation in the interaction between tau and SHP2 as well as the functional significance of the interaction. In Specific Aim III, we will determine if SHP2 is activated in AD. SHP2 and MAPK activation will also be investigated in a mouse tauopathy model. These aims will (1) advance our knowledge of the mechanisms undertaken by abnormally phosphorylated tau and (2) determine if these mechanisms are taking place during neurodegeneration. Abnormally phosphorylated tau is the earliest sign of neurodegenerative disease and our investigation aims to identify the earliest steps taken towards the neuropathogenic process. Our data will aid in the identification of new targets for disease therapeutics and new biomarkers for tracking disease progress.