Clustering of human prion protein and α-synuclein oligomers requires the prion protein N-terminus

The interaction of prion protein (PrP) and α-synuclein (αSyn) oligomers causes synaptic impairment that might trigger Parkinson’s disease and other synucleinopathies. Here, we report that αSyn oligomers (αSynO) cluster with human PrP (huPrP) into micron-sized condensates. Multivalency of αSyn within oligomers is required for condensation, since clustering with huPrP is not observed for monomeric αSyn. The stoichiometry of the heteroassemblies is well defined with an αSyn:huPrP molar ratio of about 1:1. The αSynO−huPrP interaction is of high affinity, signified by slow dissociation. The huPrP region responsible for condensation of αSynO, residues 95−111 in the intrinsically disordered N-terminus, corresponds to the region required for αSynO-mediated cognitive impairment. HuPrP, moreover, achieves co-clustering of αSynO and Alzheimer’s disease-associated amyloid-β oligomers, providing a case of a cross-interaction of two amyloidogenic proteins through an interlinking intrinsically disordered protein region. The results suggest that αSynO-mediated condensation of huPrP is involved in the pathogenesis of synucleinopathies. Nadine S. Rösener et al. show that α-synuclein oligomers can cluster with human prion protein (huPrP) into condensates. The intrinsically disordered N-terminus of huPrP is necessary for this high-affinity interaction, suggesting a link between cluster formation and toxicity.