STAT3在tau蛋白异常聚积导致学习记忆障碍中的作用及其机制研究

The intracellular accumulation of abnormal tau protein induced learning and memory deficits. Tau is a cytoskeleton protein, however, the underlying mechanisms of cognitive deficits induced by tau is still unclear. The applicants found that overexpression of tau significantly changed the mRNA levels of 520 genes, and the activity of signal transducer and activator of transcription-3 (STAT3) decreased to 0.27 fold compared with the control. The total phosphorylated level of STAT3 increased, while the protein level of STAT3 in the nuclear fraction decreased with the total level of acetylated STAT1 increased. Previous studies have reported that STAT3 regulated the learning and memory abilities through remodeling the dendritic plasticity. Above all, the applicants speculated that the intracellular accumulation of abnormal tau protein may increase STAT1 acetylation, and the increased acetylated STAT1 binds more STAT3 protein to inhibit STAT3 from transporting into the nucleus. The inactivation of STAT3 impairs dendritic plasticity to induce cognitive deficits. The purpose of this project is to investigate the key roles of STAT3 inhibition in the learning and memory impairments induced by the intracellular abnormal accumulation of tau, and elucidate the underlying mechanisms of tau accumulation inhibiting STAT3 and impairing cognition through STAT3 inactivation in the cell lines and animal models by gene transfection, behavior tests and electrophysiology, and so on. The results will help to reveal the molecular mechanisms of the learning and memory deficits induced by the abnormal accumulation of tau protein, and also provide new molecular target for protecting against tau-related cognitive deficits.

Tau蛋白在细胞内异常聚积损害学习记忆功能，但其机制尚不清楚。申请者发现：过表达tau导致520个基因mRNA水平发生显著变化；转录因子STAT3（信号转导及转录激活因子3）磷酸化水平上升，但核内STAT3水平降低，STAT3转录活性明显下降；STAT1乙酰化水平升高。由于STAT3可调节学习记忆能力，其机制可能与突触可塑性有关。我们推测，tau蛋白异常聚积可能通过乙酰化STAT1，从而使STAT1与STAT3结合增多，抑制STAT3入核，引起STAT3转录活性降低，通过损害突触可塑性而导致行为学障碍。本项目拟通过基因转染、行为学、电生理等技术，在细胞及整体水平确定STAT3活性抑制在tau蛋白聚积所致行为学障碍中的关键作用；阐明tau聚积抑制STAT3活性及STAT3抑制后介导tau引起学习记忆损伤的分子机制。研究结果将揭示tau损害学习记忆的新分子机制，并为药物研发提供新分子靶标。

背景：Tau蛋白在大脑中的异常聚集与神经退行性变和记忆退化呈正相关，但tau蛋白相关突触和认知损害的机制尚不清楚。我们之前的工作已经发现，人类全长tau(hTau)异常聚集通过激活转录因子STAT1，抑制NMDARs的表达，进而导致记忆障碍。STAT3也属于STAT蛋白家族，据研究报道STAT3参与突触可塑性和认知的调节。探讨转录因子STAT3在AD模型小鼠中的活性变化情况、对突触复杂性和学习记忆的作用及分子机制。.目的：探索STAT3在hTau异常聚集诱导的认知缺陷中的作用.方法：在体外实验中采用HEK293细胞，通过EMSA、荧光素酶报告基因、免疫沉淀等方法检测STAT3活性。在体内实验中，将AAV病毒注射到C57小鼠的海马CA3区。采用免疫印迹试验、实时定量聚合酶链反应和免疫荧光检测突触蛋白水平。通过电生理、行为学检测和高尔基染色等方法检测过表达STAT3或非乙酰化STAT1后突触可塑性和记忆能力的恢复情况。.结果：细胞hTau异常聚集后通过增加STAT1与STAT3的结合，使STAT1发生乙酰化，将STAT3滞留在细胞质中，从而使STAT3失活。过表达STAT3或非乙酰化的STAT1可通过增加NMDARs的表达来改善hTau诱导的突触丢失和学习记忆障碍。.结论： hTau异常聚集通过降低STAT3活性抑制NMDARs的表达和突触可塑性，导致突触损伤和记忆障碍。