Amplification of distinct α-synuclein fibril conformers through protein misfolding cyclic amplification

Amyloid fibril formation has been implicated in the pathogenesis of neurodegenerative diseases. Fibrillation generates numerous conformers. Presumably, the conformers may possess specific biological properties, thus providing a biochemical framework for strains of prions. However, the precise relationship between various fibril conformers and their pathogenic functions has not been determined because of limited accessibility to adequate amounts of fibrils from tissue samples. α-Synuclein is one such protein, and it has been implicated in Parkinson disease. Using a technique known as protein misfolding cyclic amplification, originally developed for amplifying prions, we established a procedure through which the amplification of α-synuclein fibrils is possible. With a trace amount of seeds, we succeeded in amplifying α-synuclein fibrils. The replication of the seeds was faithful in terms of conformation even after multiple rounds of cyclic amplification. Moreover, two transgenic mouse strains each representing a distinct synucleinopathy were used to investigate different conformers by using this technique. The amplified α-synuclein fibrils derived from the tissue extracts of these two strains led to the production of two different fibril conformers with distinct proteinase K digestion profiles. Together, our results demonstrated that a trace amount of α-synuclein fibrils in tissue extracts could be amplified with their conformations conserved. This procedure should be useful in amplifying α-synuclein fibrils from the brains and body fluids of patients afflicted with synucleinopathies and may serve as a potential diagnostic tool for Parkinson disease and other synucleinopathies. Neurodegeneration: Copying misfolded proteins A method to copy fibrous protein structures associated with neurodegenerative diseases could aid diagnosis and basic research. Specific protein molecules fold and aggregate to form deposits known as amyloid fibrils in brain cells in conditions such as Alzheimer's and Parkinson's diseases. Studying these misfolded proteins in patients' brains or animal models has been hampered by difficulties in obtaining adequate supplies. Seung-Jae Lee and colleagues at Seoul National University, with co-workers elsewhere in Korea and in the USA, have developed a way to use a small sample of one such protein as a “seed” that can be amplified into larger quantities of protein molecules with the same disease-linked folding pattern as the seed. They demonstr