糖基化异常在高尔基体破碎诱导的tau蛋白过度磷酸化中的作用及机制

Microtuble associated protein tau plays important role in the stabilization of structure and function of neuron and hyperphosphorylation of tau is one key marker of neurodegeneration in Alzheimer's disease(AD). AD tau is abnormally glycosylated and the mechanism involved is still unclear. Golgi apparatus is important for glycosylation and the damage signal conducting in neuron and the fragmentation of Golgi is the key link. Golgi fragmentation has been found in the early stage of AD and there is no report to explain how Golgi fragmentation is involved in the hyperphosphorylation and abnormal glycosylation of tau. Previously, we found Golgi fragmentation induced tau hyperphosphorylation In this research we will find out the abnormal Golgi matrix proteins in AD pathogenesis and figure out which matrix protein(s) highly correlated with tau hyperphosphorylation. Furtherly, we will study which key signaling molecules are involved in the hyperphosphorylation and abnormal glycosylation of tau.and if tau hyperphosphorylation could be rescued by regulation those important Golgi matrix proteins.There is no report explaining these questions. Our results will contribute to understanding the mechanism of tau hyperphosphorylation and seeking for the effective target.

微管相关蛋白tau过度磷酸化是老年性痴呆症（AD）神经元退行性变性的重要标志，但其分子细胞机制尚不清楚；AD tau也发生了异常糖基化。高尔基体是蛋白质糖基化修饰（包括N-糖基化、O-糖基化）的重要场所，高尔基体破碎能介导神经元损伤，且在AD早期神经元内便可见高尔基体破碎，关于高尔基体破碎能否诱导tau过度磷酸化、及其与异常糖基化的关系。申请者最近的研究显示高尔基体破碎导致tau过度磷酸化。本项目拟采用AD转基因小鼠和转基因细胞，深入研究 AD发病过程中哪些高尔基体基质蛋白发生改变；其中哪些与tau蛋白过度磷酸化密切相关；高尔基体破碎是否通过诱导糖基化紊乱而促使tau发生过度磷酸化；调节关键的高尔基体基质蛋白能否改善tau异常糖基化、过度磷酸化。结果将首次揭示高尔基体破碎在tau蛋白过度磷酸化中的作用及机制，为理解AD tau蛋白病理改变的上游机制提供新信息，为减缓tau毒性提供新思路。

高尔基体是蛋白质糖基化修饰（包括N-糖基化、O-糖基化）的重要场所，高尔基体破碎能介导神经元损伤，老年性痴呆症（Alzheimer's disease， AD）早期神经元内便可见高尔基体破碎。异常聚积的微管相关蛋白tau是AD神经元退行性变性的重要分子标志，过度磷酸化、异常糖基化是tau异常聚积的关键环节之一。本项目旨在深入研究神经元高尔基体破碎诱导tau 过度磷酸化的机制、及其与异常糖基化的关系。本项目发现，老化过程中神经元高尔基体破碎显著增多，AD动物脑中神经元高尔基体破碎比例显著高于同龄对照动物。进一步发现工具药诱导高尔基体破碎的同时发生了tau 过度磷酸化，而通过过表达特定的高尔基体基质蛋白稳定高尔基体形态（防止破碎）能显著减轻tau磷酸化水平。证实神经元高尔基体破碎是的tau 过度磷酸化的关键机制之一，明确了高尔基体破碎参与AD tau 蛋白过度磷酸化的机制，并筛选出参与AD 发病的关键高尔基体基质蛋白（Golgin 84）、关键信号分子（CDK5，ERK）；确定N-乙酰葡糖胺基转移酶I（N-acetylglucosamine transferase-I，NAGTI）、N-乙酰半乳糖胺基转移酶2（N-acetylgalactosyltransferase-2，GalNAc-T2）在高尔基体破碎诱导tau异常糖基化、过度磷酸化中的关键作用。以上说明高尔基体形态的改变能充分反映老化/AD过程中神经元的活性情况变化，同时还能作为上游因子引发 tau 蛋白过度磷酸化。研究结果为理解AD 样tau 蛋白过度磷酸化机制提供新信息，为减缓tau 毒性提供新分子靶标。