Prion-Like Seeding of Misfolded α-Synuclein in the Brains of Dementia with Lewy Body Patients in RT-QUIC

The prion-like seeding of misfolded alpha-synuclein (alpha Syn) involved in the pathogenesis of Lewy body diseases (LBD) remains poorly understood at the molecular level. Using the real-time quaking-induced conversion (RT-QUIC) seeding assay, we investigated whether brain tissues from cases of dementia with Lewy bodies (DLB), which contain serine 129 (Ser129)-phosphorylated insoluble aggregates of alpha Syn, can convert Escherichia coli-derived recombinant alpha Syn (r-alpha Syn) to fibrils. Diffuse neocortical DLB yielded 50% seeding dose (SD50) values of 10(7)similar to 10(10)/g brain. Limbic DLB was estimated to have an SD50 value of similar to 10(5)/g brain. Furthermore, RT-QUIC assay discriminated DLB from other neurological and neurodegenerative disorders. Unexpectedly, the prion-like seeding was reconstructed in reactions seeded with oligomer-like species, but not with insoluble aggregates of r-alpha Syn, regardless of Ser129 phosphorylation status. Our findings suggest that RT-QUIC using r-alpha Syn can be applied to detect seeding activity in LBD, and the culprit that causes prion-like seeding may be oligomeric forms of alpha Syn.