Distinct α-Synuclein Strains Differentially Promote Tau Inclusions in Neurons

Many neurodegenerative diseases are characterized by the accumulation of insoluble protein aggregates, including neurofibrillary tangles comprised of tau in Alzheimer’s disease and Lewy bodies composed of α-synuclein in Parkinson’s disease. Moreover, different pathological proteins frequently codeposit in disease brains. To test whether aggregated α-synuclein can directly cross-seed tau fibrillization, we administered preformed α-synuclein fibrils assembled from recombinant protein to primary neurons and transgenic mice. Remarkably, we discovered two distinct strains of synthetic α-synuclein fibrils that demonstrated striking differences in the efficiency of cross-seeding tau aggregation, both in neuron cultures and in vivo. Proteinase K digestion revealed conformational differences between the two synthetic α-synuclein strains and also between sarkosyl-insoluble α-synuclein extracted from two subgroups of Parkinson’s disease brains. We speculate that distinct strains of pathological α-synuclein likely exist in neurodegenerative disease brains and may underlie the tremendous heterogeneity of synucleinopathies. [Display omitted] •In vitro fibrillization can generate conformationally distinct α-synuclein fibrils•These distinct fibril strains differ in their ability to cross-seed tau aggregation•N and C termini of α-synuclein contribute to dynamics of strain conformations•Conformationally different α-synuclein can be detected in Parkinson’s disease brains Two distinct conformers of alpha-synuclein fibrils differ in their ability to seed native alpha-synuclein and to cross-seed another protein, tau. The findings suggest that conformational variations of seed aggregates may underlie diversity in the pathology of synucleinopathies.