STAT3 Ameliorates Cognitive Deficits Via Regulation Of NMDARs' Expression In An Animal Model Of Alzheimer's Disease

Background: Alzheimer's disease(AD)is one of neurodegenerative diseases,which has two typical pathological features-plaques formed by beta-amyloid peptides outside neurons,and neurofibrillary tangles(NFTs)formed by abnormal aggregates of hyperphosphorylated h Tau proteins in neurons.The P301 L mutation of Tau protein occurred on exon 10 of 4R Tau,significantly increased the level of Tau filaments formed by 4R Tau.The level of tau phosphorylation in the brain of Tau-P301 L mice increased gradually and accumulatively,leading to extensive pathological changes of neurofibrils.Studies showed that abnormal aggregation of h Tau induced synaptic damage and neurodegenerative diseases,thus damaging learning and memory ability.However,the molecular mechanisms are still unclear at present.Our previous study showed that h Tau could induce gene transcription disorders and increase the transcription activity of STAT1,which inducing transcriptional inhibition of NMDA receptor,and then resulting in synaptic damage and learning and memory impairment.The transcription activity of STAT3 also decreased while h Tau overexpressed.It's known that STAT3 and STAT1 belong to protein family of STAT,and they can form heterodimer.Therefore,we explore the changes in STAT3 activity and the role of STAT3 in synaptic toxicity and learning and memory impairment induced by P301L-h Tau and the underlying molecular mechanisms.Objective: To investigate the changes in STAT3 activity and the role of STAT3 in synaptic complexity and learning and memory impairment induced by P301L-h Tau and the underlying molecular mechanisms.Methods: In the cell model of over expressing P301L-h Tau,the transcriptional factor activity of STAT3 was detected by fluorescein reporter gene assay and gel electrophoresis migration assay.We injected AAV-cre into the CA3 region of STAT3flox/flox mice to conditionally knock down STAT3.or infected P301L-h Tau protein adeno-associated virus into the CA3 region of 2-month-old male mice.The protein level and phosphorylation level of STAT3 were detected by Western Blot.The abilities of learning and memory in mice were observed by behavioral tests,such as Morris Water Maze,New novel recognition and Fear condition test.The transcription level and expression level of synaptic proteins were detected by q PCR and Western blot.The synaptic plasticity was detected by LTP,and the density of synaptic dendritic splines was detected by Golgi staining.Bioinformatics was used to predict the target genes that STAT3 might bind to,and luciferase reporter assay was used to identify the mechanism of STAT3 regulating NMDA receptor gene transcription.Results: Overexpression of P301L-h Tau significantly decreased the transcription factor activity of STAT3 by EMSA and dual-luciferase reporting experiments.In vitro and in vivo,the protein level of STAT3 and p S727-STAT3 in the nucleus fraction was significantly decreased and p Y705-STAT3 in the total extracts was increased.P301L-h Tau activated JAK2,and then,JAK2 phosphorylated Y705-STAT3.Co-IP assay in HEK293 cells showed that the binding of STAT1 and STAT3 was enhanced in whole cells and cytoplasm fraction,but weakened in nucleus fraction.Mass spectrometry showed that P301L-h Tau enhanced the acetylation signal of STAT1 at K410 and K413.Co-IP assay showed that P301L-h Tau can directly combine with STAT1 to acetylate it in vitro,and acetylated STAT1 combined with STAT3 to inhibit it transfer to the nucleus.P301L-h Tau virus was injected into the CA3 regionof 2 months old C57 mice,and the transcription and expression of protein involved in synaptic proteins were suppressed,synaptic plasticity and cognitive functions impaired.The conditional knock out of STAT3 simulated the phenotypic changes in mice infected with P301L-h Tau.Overexpression of STAT3 reversed P301L-h Tau induced synaptic and learning and memory damages.Suppression of STAT1 acetylation could not reverse P301L-h Tau-induced synaptic toxicity and improve learning and memory.STAT3 could directly bind the promoter of NMDARs by chromatin immunoprecipitation,and the luciferase report assay showed that STAT3 regulated NMDARs expression.Conclusions: STAT3 could regulate the transcription and expression of NMDARs.The decrease activity of STAT3 induced by P301L-h Tau would lead to decreased hippocampal synaptic plasticity and impaired learning and memory.Overexpression of STAT3 reverses P301L-h Tau-induced synaptic toxicity and improves learning and memory abilities.Inhibition STAT1 acetylation could not reverse P301L-h Tau-induced synaptic toxicity and improves learning and memory.