O-GlcNAcylation of tau: a link between glucose metabolism and neurodegeneration

描述（由申请人提供）：大脑中tau蛋白的异常过度磷酸化和聚集是阿尔茨海默病（AD）神经退行性变的关键。葡萄糖摄取/代谢在AD大脑中受损，这被认为是导致神经变性的原因。然而，这种损伤如何导致神经退行性变尚不清楚。该项目的具体目标是揭示tau o - glcn酰化的性质和功能作用[一种独特类型的o -糖基化，β - n -乙酰氨基葡萄糖（GlcNAc）与蛋白质的丝氨酸或苏氨酸残基相连]，并揭示AD脑葡萄糖摄取/代谢受损导致神经变性的机制。这项建议的长期目标是了解阿尔茨海默病神经退行性变的机制，并在此基础上制定预防和治疗该疾病的策略。因此，具体目的是：(1)绘制tau蛋白的o - glcnac酰化位点，确定AD脑中tau蛋白o - glcnac酰化的变化。我们还将通过比较AD和对照组脑内UDP-GlcNAc水平、O-GlcNAc转移酶和O-GlcNAcase活性来研究tau - o - glcnac酰化变化的潜在原因。(2)在体外和分化的PC12细胞中研究o - glcnac酰化和tau磷酸化的相互作用。通过测量tau o - glcn酰化的微管结合和组装活性，以及检测tau o - glcn酰化改变后的细胞形态和细胞器运输，将研究tau o - glcn酰化的功能作用。(3)探讨脑葡萄糖摄取/代谢障碍导致阿尔茨海默病神经变性的分子机制。采用脑葡萄糖摄取/代谢受损小鼠和脑室内注射细胞松弛素b后小鼠两种动物模型，研究其对tau o - glcn酰化和磷酸化的影响。o - glcn酰化在tau过度磷酸化和低葡萄糖摄取/代谢诱导的神经变性中的确切作用也将在小鼠大脑中得到阐明。这些研究将揭示AD脑中tau o - glcn酰化及其失调的性质和功能作用，揭示AD脑葡萄糖摄取/代谢受损导致神经退行性变的机制。这些研究的完成将为阿尔茨海默病的神经变性机制提供新的见解，并有助于制定预防和治疗阿尔茨海默病以及其他神经退行性疾病的新策略。

DESCRIPTION (provided by applicant): Abnormal hyperphosphorylation and aggregation of tau protein in the brain are critical to neurodegeneration of Alzheimer Disease (AD). Glucose uptake/metabolism is impaired in AD brain, which is believed to cause neurodegeneration. However, how this impairment contributes to neurodegeneration is unknown. The specific goal of this project is to reveal the nature and functional role of tau O-GlcNAcylation [a unique type of O-glycosylation by which beta-N-acetylglucosamine (GlcNAc) is linked to serine or threonine residues of proteins] and to uncover the mechanism by which impaired brain glucose uptake/metabolism of AD contributes to neurodegeneration. The long-term objective of this proposal is to understand the mechanism of neurodegeneration in AD and, based on this knowledge, to develop strategies to prevent and treat the disease. Hence, the Specific Aims are: (1) Map the O-GlcNAcylation sites of tau and determine the change of tau O-GlcNAcylation in AD brain. The underlying cause of the change in tau O-GlcNAcylation will also be studied by comparing brain level of UDP-GlcNAc and activities of O-GlcNAc transferase and O-GlcNAcase between AD and controls. (2) Study the interactions between O-GlcNAcylation and phosphorylation of tau both in vitro and in differentiated PC12 cells. The functional role of tau O-GlcNAcylation will be studied by measuring its microtubule-binding and -assembly activities and examining cell morphology and organelle transport upon alteration of tau O-GlcNAcylation. (3) Investigate the molecular mechanism by which impaired brain glucose uptake/metabolism contributes to neurodegeneration of Alzheimer's disease. Two animal models of impaired brain glucose uptake/metabolism-fasted mice and mice after intracerebroventricular injection of cytochalasin B-will be used to study its effects on tau O-GlcNAcylation and phosphorylation. The exact role of O-GlcNAcylation in tau hyperphosphorylation and neurodegeneration induced by low glucose uptake/metabolism will also be elucidated in the mouse brains. These studies will reveal the nature and functional role of tau O-GlcNAcylation and its dysregulation in AD brain and uncover the mechanism by which impaired brain glucose uptake/metabolism of AD contributes to neurodegeneration. Completion of these studies will provide new insight into the mechanism of neurodegeneration of AD and help develop novel strategies to prevent and treat Alzheimer's disease and probably other neurodegenerative disorders.