p85S6K sustains synaptic GluA1 to ameliorate cognitive deficits in Alzheimer’s disease

Background Ribosomal protein S6 kinase 1(S6K1)is a serine-threonine kinase that has two main isoforms:p70S6K(70-kDa isoform)and p85S6K(85-kDa isoform).p70S6K,with its upstream mammalian target of rapamycin(mTOR),has been shown to be involved in learning and memory and participate in the pathophysiology of Alzheimer’s dis-ease(AD).However,the function of p85S6K has long been neglected due to its high similarity to p70S6k.The role of p85S6K in learning and memory is still largely unknown.Methods We fractionated the postsynaptic densities to illustrate the differential distribution of p85S6K and p70S6K.Coimmunoprecipitation was performed to unveil interactions between p85S6K and the GluA1 subunit of AMPA receptor.The roles of p85S6K in synaptic targeting of GluA1 and learning and memory were evaluated by specific knockdown or overexpression of p85S6K followed by a broad range of methodologies including immunofluorescence,Western blot,in situ proximity ligation assay,morphological staining and behavioral examination.Further,the expression level of p85S6K was measured in brains from AD patients and AD model mice.Results p85S6K,but not p70S6K,was enriched in the postsynaptic densities.Moreover,knockdown of p85S6K resulted in defective spatial and recognition memory.In addition,p85S6K could interact with the GluA1 subunit of AMPA receptor through synapse-associated protein 97 and A-kinase anchoring protein 79/150.Mechanistic studies demonstrated that p85S6K could directly phosphorylate GluA1 at Ser845 and increase the amount of GluA1 in syn-apses,thus sustaining synaptic function and spine densities.Moreover,p85S6K was found to be specifically decreased in the synaptosomal compartment in the brains of AD patients and AD mice.Overexpression of p85S6K ameliorated the synaptic deficits and cognitive impairment in transgenic AD model mice.Conclusions These results strongly imply a significant role for p85S6K in maintaining synaptic and cognitive function by interacting with GluA1.The findings provide an insight into the rational targeting of p85S6K as a therapeutic potential for AD.

Oral everolimus inhibits intimal proliferation in injured carotid artery in rats

Background Everolimus, a derivative of sirolimus, is a potent immunosuppressant that has important anti-proliferative properties. In the present study, we demonstrated the inhibiting neointimal hyperplasia in injured carotid arteries in rats by using two different doses of everolimus administrated via the oral route for a long time. Methods A rat model of carotid artery injury was established by balloon inflation. Eighty rats were randomly divided into the sham-operated group （n=20）, injury group （n=20）, low dosage of everolimus group （n=20）, and high dosage of everolimus group （n=20）. The low close of everolimus （1.5 mg/kg） was given one day before injuring the carotid artery by balloon, followed by 0.75 mg/kg per day for 28 days via intragastric gavage. High dose everolimus （2.5 mg/kg） was given one day before injuring the carotid artery by balloon, followed by 1 mg/kg per day for 28 days. Expression of eukaryotic translation initiation factor 4E （elF-4E） and phosphorylation of ribosomal proteinS6 kinase 1 （P70S6K） were determined by reverse transcription-polymerase chain reaction and Western blotting analysis. Results In the injured carotid artery, neointimal hyperplasia was normally observed four weeks after injury. Everolimus inhibited neointimal hyperplasia after balloon injury in a dose dependent manner. At the same time, the study demonstrated that everolimus reduced the expression of P-P70S6K, elF-4E, transforming growth factor （TGF）-131 and of proliferating cell nuclear antigen （PCNA）. Conclusions Everolimus significantly inhibited neointimal hyperplasia of the injured carotid artery. The effect depended on dosaqe and was associated with the reduction of phosphorylation of P70S6K and the elF-4E expression level.