PKA-CREB Signaling Suppresses The Expression Of Tau

Objective Alzheimer disease,also known as senile dementia, is the most common neurodegenerative diseases in old people.Abnormal hyperphosphorylation of tau protein is the main component of neurofibrillary tangles (NFTs) in AD brains, while the number of NFTs in patients positive correlation with the degree of dementia symptoms significantly.Tau proteins’ pathological aggregation is one of the main features in neurodegenerative diseases.CREB is a nuclear transcription factor about constitutive expression, plays a crucial role in protecting neuronal transcription system.According to the previous studies,we found that compared with the normal brain,the content of total tau is rised and the content of the full-length CREB is decreased in AD brain.Sir CREB is a crucial transcription factor and PKA-CREB signaling pathway becomes weaker in the brains of AD patients. Therefore, this study aimed to explore whether CREB affects the transcription of tau protein and how affects the transcription of tau protein at the molecular level, cellular level and animal level respectively.Methods We injected the intracerebroventricular of two-year old mice by forskolin with different concentrations and determined the expression level of tau protein and tau mRNA by Western blots and qPCR; Adding forskolin to neuronal cells of two-month-old ICR mice in primary culture with different concentrations,then determined the expression level of tau protein and tau mRNA by Western blots and qPCR; PCI-neo/CREB was transformed into SH-SY5Y cell and then we determined the expression level of tau protein and tau mRNA by Western blots and qPCR;we constructed serial deletion mutations, site-mutations and the promoter of tau plasmid into pGL3 to drive the luciferase to determine the role of CREB on tau expression; we explored whether CREB acted on the CRE elements by using electrophoretic mobility shift assay (EMSA) and Chromatin immunoprecipitation (ChIP) in intracellular and extracellular.Results After injected the intracerebroventricular of two-year old mice by forskolin with different concentrations,we found that tau protein and tau mRNA levels were all decreased;After added forskolin to neuronal cells of two-month-old ICR mice in primary culture with different concentrations,we found that tau protein and tau mRNA levels were all decreased; After transformed PCI-neo/CREB into SH-SY5Y cell, we found that tau protein and tau mRNA levels were all decreased;Based on MatInspector software, we found that the promoter region of tau had three cAMP response elements (CRE) and we named them CRE-1, CRE-2, and CRE-3 respectively, on the other hand,overexpression of CREB could decrease luciferase activity which was driven by tau promoter region remarkably,this result suggested that CREB could suppress tau expression; we demonstrated that CREB could bind to CRE1 and CRE3 elements by using EMSA and ChIP assays;we determined that CRE1, but not CRE2 and CRE3,played a crucially suppressant role on the expression of tau by serial deletion mutations and site-mutations of the promoter region of tau.Conclusions CREB mainly binds on CRE1 and CRE3 which were located at the promoter region of tau to suppress the expression of tau,rather than CRE2;CRE1, but not CRE2 and CRE3,played a crucially suppressant role on the expression of tau;CREB regulates the express of tau protein by suppress the transcription of tau when CREB was activated by PKA signaling pathway.