Phosphorylation of FE65 Ser(610) by serum- and glucocorticoid-induced kinase 1 modulates Alzheimer's disease amyloid precursor protein processing

Alzheimer's disease (AD) is a fatal neurodegenerative disease affecting 36 million people worldwide. Genetic and biochemical research indicate that the excessive generation of amyloid-beta peptide (A beta) from amyloid precursor protein (APP), is a major part of AD pathogenesis. FE65 is a brain-enriched adaptor protein that binds to APP. However, the role of FE65 in APP processing and the mechanisms that regulate binding of FE65 to APP are not fully understood. In the present study, we show that serum- and glucocorticoid-induced kinase 1 (SGK1) phosphorylates FE65 on Ser(610) and that this phosphorylation attenuates FE65 binding to APP. We also show that FE65 promotes amyloidogenic processing of APP and that FE65 Ser(610) phosphorylation inhibits this effect. Furthermore, we found that the effect of FE65 Ser(610) phosphorylation on APP processing is linked to a role of FE65 in metabolic turnover of APP via the proteasome. Thus FE65 influences APP degradation via the proteasome and phosphorylation of FE65 Ser(610) by SGK1 regulates binding of FE65 to APP, APP turnover and processing.