O-GlcNAcylation of tau: glucose metabolism & neurodegen

描述（由申请人提供）：脑中tau蛋白的异常过度磷酸化和聚集对阿尔茨海默病（AD）的神经变性至关重要。葡萄糖摄取/代谢在AD脑中受损，这被认为导致神经变性。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-GlcNAc化的性质和功能作用[一种独特的O-糖基化类型，β-N-乙酰葡萄糖胺（GlcNAc）通过这种糖基化与蛋白质的丝氨酸或苏氨酸残基连接]，并揭示AD的脑葡萄糖摄取/代谢受损导致神经变性的机制。该提案的长期目标是了解AD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，本研究的具体目的是：（1）定位AD脑中tau蛋白的O-GlcNAc化位点，并确定AD脑中tau蛋白O-GlcNAc化的变化。还将通过比较AD和对照之间的UDP-GlcNAc的脑水平以及O-GlcNAc转移酶和O-GlcNAc酶的活性来研究tau O-GlcNAc化变化的根本原因。(2)在体外和分化的PC 12细胞中研究tau蛋白的O-GlcNAc化和磷酸化之间的相互作用。tau O-GlcNAc化的功能作用将通过测量其微管结合和组装活性以及检查tau O-GlcNAc化改变后的细胞形态和细胞器运输来研究。(3)研究脑葡萄糖摄取/代谢受损导致阿尔茨海默病神经退行性变的分子机制。两种脑葡萄糖摄取/代谢受损的动物模型-禁食小鼠和脑室内注射细胞松弛素B后的小鼠将用于研究其对tau O-GlcNAcylation和磷酸化的影响。还将在小鼠脑中阐明O-GlcNAc化在由低葡萄糖摄取/代谢诱导的tau过度磷酸化和神经变性中的确切作用。这些研究将揭示AD脑中tau O-GlcNAc化及其失调的性质和功能作用，并揭示AD脑葡萄糖摄取/代谢受损导致神经变性的机制。这些研究的完成将为AD的神经退行性变机制提供新的见解，并有助于开发预防和治疗阿尔茨海默病和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.