p75NTR在阿尔茨海默病tau蛋白病变扩散中的作用和机制研究

Abnormal hyperphosphorylation of tau is a key factor in Alzheimer’s disease. The newly discovered shows trans-synaptic spread of tau pathology, however, the underlying mechanisms are still unclear. We found that p75NTR and tau could bind directly to each other and spreading of tau pathology reduced in the p75NTR knockout mouse brain. The reported showed that the field of tauopathy proganation is consistent with p75NTR positive neurons fiber projection area in Alzheimer's disease brain. We hypothesise that p75NTR may play an important role in trans-synaptic spread of tau pathology. In order to investigate the effect of p75NTR on tauopathy proganation, distribution and the levels of tau including total tau, phosphorylated tau and neurofibrillary tangles in cells will be detected at the presence or absence of p75NTR in vivo and in vitro including cell culture, primary neuron culture. To explore the underlying mechanisms, co-immunoprecipitation, FRET, SNAP-Tag, IAsys system will be applied to detect the relation of p75NTR combined with tau. To investigate the role of p75NTR mediated tau endocytosis, electron microscopy and Laser confocal live cell imaging system will be applied. And computer simulation of the molecules will be used to analyze the field combined with tau on p75NTR. Dot mutation and gene transfection expression will be used to verifythe effect of p75NTR in the process of tau endocytosis. Here, we are about to reveal the mechanism of tauopathy proganation, which will be important for blocking spread of tau pathology in Alzheimer's disease.

Tau蛋白过度磷酸化引起的神经原纤维缠结是阿尔茨海默病（AD）的主要病理特征之一，AD脑内tau蛋白病变扩散对AD发展起重要作用，其分子机制不清楚。我们发现p75NTR与tau蛋白相互结合、敲除p75NTR基因小鼠脑内tau蛋白病变扩散减少。而AD脑内tau蛋白病变扩散与p75NTR阳性神经元纤维投射分布一致。我们提出，p75NTR很可能是介导tau蛋白病变扩散的关键受体途径。拟采用表达或敲除p75NTR基因，检测tau蛋白磷酸化、NFTs的改善，探讨p75NTR在tau蛋白扩散中的作用；采用免疫共沉淀、FRET技术、IAsys分析系统检测tau与p75NTR特异性结合，采用激光共聚焦活细胞成像等技术检测p75NTR介导tau蛋白的内吞作用；采用计算机模拟p75NTR的tau结合部位，探讨转染表达p75NTR结合部位突变基因对防治AD的作用。本项目对揭示AD发生机制及AD防治具有重要意义。

阿尔茨海默病（AD）是痴呆最常见的类型，也是最常见的tau蛋白病。AD的发病机制仍未阐明，缺乏有效防治措施。 .Tau病变是AD主要病理特征之一。AD脑内异常磷酸化tau聚集，形成神经纤维缠结，导致神经元变性、丢失。AD在显著临床症状前20多年，内嗅皮层就出现了异常磷酸化tau的神经元，AD病理改变最早也是内嗅皮层，随着AD病理改变从内嗅皮层向外扩散，AD症状逐渐加剧。揭示AD脑内tau病变逐渐扩展机制，有可能遏制AD进展。.该项目探讨了p75NTR对tau病变的影响，并揭示其机制；并通过阻断p75NTR的作用，探讨了对tau病变的影响和行为障碍的改善作用。结果（一）、p75NTR影响P301L小鼠脑内不同脑区tau磷酸化。（二）、p75NTR影响Aβ诱导tau过度磷酸化，敲除P75NTR基因后，Aβ诱导的tau磷酸化显著降低、Aβ诱导的突触损害和神经元丢失降低、calpain/CDK5和AKT/GSK3β信号通路参与了其调控作用。（三）、proNGF/p75NTR影响tau磷酸化。AD脑内AT8阳性神经元p75NTR的水平显著增加；P301L小鼠脑内p75NTR、proNGF显著增加；不同月龄P301L/p75+/-小鼠脑内海马和内嗅皮层tau磷酸化程度明显减少；敲除p75NTR基因后proNGF诱导的tau磷酸化显著降低，AKT/GSK3β信号通路参与了调控作用。（四）、阻断p75NTR改善P301L小鼠学习记忆。P301L小鼠敲除p75NTR基因后学习记忆能力显著改善；转染表达p75NTR胞外段后P301L小鼠的学习记忆行为学显著改善，同时，小鼠脑内海马和内嗅皮层区tau磷酸化显著降低。.本项目结果提示p75NTR影响脑内不同脑区tau病变，阻断p75NTR的作用能改善脑内不同脑区tau病变；因此，p75NTR可能在tau病变扩散中起重要作用，是AD防治的一个新靶点，具有潜在AD防治价值。