Prion diseases are infectious and fatal
neurodegenerative diseases affecting humans and animals. Transmission is possible within and between species with zoonotic potential. Currently, no prophylaxis or treatment exists.
Prions are composed of the misfolded
isoform PrPSc of the cellular
prion protein PrPC. Expression of PrPC is a prerequisite for
prion infection, and conformational conversion of PrPC is induced upon its direct interaction with PrPSc. Inhibition of this interaction can abrogate
prion propagation, and we have previously established
peptide aptamers (PAs) binding to PrPC as new anti-
prion compounds. Here, we mapped the interaction site of PA8 in PrP and modeled the complex in silico to design targeted mutations in PA8 which presumably enhance binding properties. Using these PA8 variants, we could improve PA-mediated inhibition of PrPSc replication and de novo
infection of neuronal cells. Furthermore, we demonstrate that binding of PA8 and its variants increases PrPC α-cleavage and interferes with its internalization. This gives rise to high levels of the membrane-anchored PrP-C1 fragment, a transdominant negative inhibitor of
prion replication. PA8 and its variants interact with PrPC at its central and most highly conserved domain, a region which is crucial for
prion conversion and facilitates toxic signaling of Aβ oligomers characteristic for
Alzheimer's disease. Our strategy allows for the first time to induce α-cleavage, which occurs within this central domain, independent of targeting the responsible
protease. Therefore, interaction of PAs with PrPC and enhancement of α-cleavage represent mechanisms that can be beneficial for the treatment of
prion and other
neurodegenerative diseases.