Alzheimer's amyloid-ß oligomers rescue cellular prion protein induced tau reduction via the Fyn pathway.

ABSTRACT

Amyloid-ß (Aß) and tau are the pathogenic hallmarks in Alzheimer's disease (AD). Aß oligomers are considered the actual toxic entities, and the toxicity relies on the presence of tau. Recently, Aß oligomers have been shown to specifically interact with cellular prion protein (PrP(C)) where the role of PrP(C) in AD is still not fully understood. To investigate the downstream mechanism of PrP(C) and Aß oligomer interaction and their possible relationships to tau, we examined tau expression in human neuroblastoma BE(2)-C cells transfected with murine PrP(C) and studied the effect under Aß oligomer treatment. By Western blotting, we found that PrP(C) overexpression down-regulated tau protein and Aß oligomer binding alleviated the tau reduction induced by wild type but not M128V PrP(C), the high AD risk polymorphic allele in human prion gene. PrP(C) lacking the Aß oligomer binding site was incapable of rescuing the level of tau reduction. Quantitative RT-PCR showed the PrP(C) effect was attributed to tau reduction at the transcription level. Treatment with Fyn pathway inhibitors, Fyn kinase inhibitor PP2 and MEK inhibitor U0126, reversed the PrP(C)-induced tau reduction and Aß oligomer treatment modulated Fyn kinase activity. The results suggested Fyn pathway regulated Aß-PrP(C)-tau signaling. Overall, our results demonstrated that PrP(C) down-regulated tau via the Fyn pathway and the effect can be regulated by Aß oligomers. Our study facilitated the understanding of molecular mechanisms among PrP(C), tau, and Aß oligomers.