α-Synuclein Amyloids Hijack Prion Protein to Gain Cell Entry, Facilitate Cell-to-Cell Spreading and Block Prion Replication

The precise molecular mechanism of how misfolded α-synuclein (α-Syn) accumulates and spreads in synucleinopathies is still unknown. Here, we show the role of the cellular prion protein (PrP(C)) in mediating the uptake and the spread of recombinant α-Syn amyloids. The in vitro data revealed that the presence of PrP(C) fosters the higher uptake of α-Syn amyloid fibrils, which was also confirmed in vivo in wild type (Prnp (+/+)) compared to PrP knock-out (Prnp (-/-)) mice. Additionally, the presence of α-Syn amyloids blocked the replication of scrapie prions (PrP(Sc)) in vitro and ex vivo, indicating a link between the two proteins. Indeed, whilst PrP(C) is mediating the internalization of α-Syn amyloids, PrP(Sc) is not able to replicate in their presence. This observation has pathological relevance, since several reported case studies show that the accumulation of α-Syn amyloid deposits in Creutzfeldt-Jakob disease patients is accompanied by a longer disease course.