Cellular prion protein neither binds to alpha-synuclein oligomers nor mediates their detrimental effects

Abstract

α-Synuclein oligomers are crucial players in the pathogenesis of Parkinson's disease. Some mechanisms involved in α-synuclein oligomer detrimental effects include membrane damage, neuroinflammation and protein-protein interactions. Recently, the cellular prion protein (PrPC) emerged as an interactor of α-synuclein oligomers, apparently mediating their detrimental activities. Through direct in vivo and in vitro approaches we herein investigated the existence of a direct cross-talk between α-synuclein oligomers and PrPC. In vitro, we assessed α-synuclein oligomer toxicity by comparing the effect in Prnp+/+ versus PrPC knockout (Prnp0/0) hippocampal neurons. Through an in vivo acute mouse model, where α-synuclein oligomers injected intracerebroventricularly induce memory impairment and neuroinflammation, we verified whether these detrimental effects were preserved in Prnp0/0 mice. In addition, PrPC-α-synuclein oligomer direct binding was investigated through surface plasmon resonance. We found that PrPC was not mandatory to mediate α-synuclein oligomer detrimental effects in vitro or in vivo. Indeed, α-synuclein oligomer toxicity was comparable in Prnp+/+ and Prnp0/0 neurons and both Prnp+/+ and Prnp0/0 mice injected with α-synuclein oligomers displayed memory deficit and hippocampal gliosis. Moreover, surface plasmon resonance analyses ruled out PrPC-α-synuclein oligomer binding. Our findings indicate that PrPC neither binds α-synuclein oligomers nor mediates their detrimental actions. Therefore, it is likely that PrPC-dependent and PrPC-independent pathways co-exist in Parkinson's disease.