Hap1 Regulates GR/CREB/BDNF Signaling Pathway In Learning And Memory Of APP/PS1 Mice

Background:Alzheimer’s disease（AD）is an insidious neurodegenerative disease,which is the main type of dementia.It is of great significance to elucidate the pathogenesis of AD and identify new therapeutic targets.More and more evidences show that the dysfunction of glucocorticoid receptor（GR）in AD hippocampus may be the key factor leading to the pathological and cognitive impairment in AD.However,the molecular mechanism of GR dysfunction is not clear.Huntingtin-associated protein1（Hap1）was the first protein identified to interact with huntingtin in yeast two-hybrid screening.Hap1 has neuroprotective effect.Substantial evidence suggests that the deficiency of its function is associated with neurodegenerative diseases.As a common neurodegenerative disease of AD,the role of Hap1 in AD has attracted increasing attention.Our previous results showed that Hap1 interacts with GR and can protect the level of GR protein.Therefore,the hypothesis is proposed that Hap1 may affect AD learning and memory by regulating GR signals.Methods:1.Using CRISPR/Cas9 gene splicing principle,the g RNA vectors targeting mouse Hap1 gene were prepared,and the constructed plasmid was used to package the virus.2.The expression of Hap1 in hippocampus of APP/PS1 mice was knocked down by stereotactic injection.Behavioral tests and Golgi staining were used to detect the effects of down-regulation of Hap1 expression on learning and memory-like behavior,hippocampus dendrite and dendritic spine morphology of APP/PS1 mice.3.AD cell model was prepared by exogenous addition of Aβ_25-35 to N2A cells.Specifically knockdown the expression of Hap1 in the hippocampus of APP/PS1 mice and AD model cells.Western-blot and q PCR were used to detect the changes of GR,CREB,BDNF protein levels and RNA levels.Results:In animal experiments:（1）Specific knockdown of Hap1 expression in the hippocampus of APP/PS1 mice resulted in learning and memory-like behavioral deficits,reduced hippocampal neurons,and decreased dendrite spine density.（2）Western-blot and q PCR showed that That deficit of Hap1 in AD hippocampus resulted in decreased GR,CREB,BDNF protein levels and RNA levels.Cell experiment:After knockdown of Hap1 in AD model cells by plasmid transfection,the protein levels and RNA levels of GR,CREB and BDNF were significantly decreased.Conclusion:The deficiency of Hap1 in the hippocampus of APP/PS1 mice leads to the down expression of GR,CREB and BDNF,as well as the decrease of neurons and dendrite spine density in the hippocampus,and finally results in the learning and memory impairment of APP/PS1 mice.