Temperature-Dependent Structural Changes of Parkinson’s Alpha-Synuclein Reveal the Role of Pre- Existing Oligomers in Alpha-Synuclein Fibrillization

Amyloid fibrils of a-synuclein are the main constituent of Lewy bodies deposited in substantial nigra of Parkinson’s disease brains. a-Synuclein is an intrinsically disordered protein lacking compact secondary and tertiary structures. To enhance the understanding of its structure and function relationship, we utilized temperature treatment to study a-synuclein conformational changes and the subsequent effects. We found that after 1 hr of high temperature pretreatment,.80uC, a-synuclein fibrillization was significantly inhibited. However, the temperature melting coupled with circular dichroism spectra showed that a-synuclein was fully reversible and the NMR studies showed no observable structural changes of a-synuclein after 95uC treatment. By using cross-linking and analytical ultracentrifugation, rare amount of pre-existing a-synuclein oligomers were found to decrease after the high temperature treatment. In addition, a small portion of C-terminal truncation of a-synuclein also occurred. The reduction of pre-existing oligomers of a-synuclein may contribute to less seeding effect that retards the kinetics of amyloid fibrillization. Overall, our results showed that the pre-existing oligomeric species is a key factor contributing to a-synuclein fibrillization. Our results facilitate the understanding of a-synuclein fibrillization