Structural features of α-synuclein amyloid fibrils revealed by Raman spectroscopy.
Parkinson's disease (PD) is associated with the formation of α-synuclein amyloid fibrils. Elucidating the role of these β-sheet-rich fibrils in disease progression is crucial; however, collecting detailed structural information on amyloids is inherently difficult because of their insoluble, non-crystalline, and polymorphic nature. Here, we show that Raman spectroscopy is a facile technique for characterizing structural features of α-synuclein fibrils. Combining Raman spectroscopy with aggregation kinetics and transmission electron microscopy, we examined the effects of pH and ionic strength as well as four PD-related mutations (A30P, E46K, G51D, and A53T) on α-synuclein fibrils. Raman spectral differences were observed in the amide-I, amide-III, and fingerprint regions, indicating that secondary structure and tertiary contacts are influenced by pH and to a lesser extent by NaCl. Faster aggregation times appear to facilitate unique fibril structure as determined by the highly reproducible amide-I band widths, linking aggregation propensity and fibril polymorphism. Importantly, Raman spectroscopy revealed molecular-level perturbations of fibril conformation by the PD-related mutations that are not apparent through transmission electron microscopy or limited proteolysis. The amide-III band was found to be particularly sensitive, with G51D exhibiting the most distinctive features, followed by A53T and E46K. Relating to a cellular environment, our data would suggest that fibril polymorphs can be formed in different cellular compartments and potentially result in distinct phenotypes. Our work sets a foundation toward future cellular Raman studies of amyloids.
['Flynn|Jessica D|JD|0000-0002-9310-4882', 'McGlinchey|Ryan P|RP|', 'Walker|Robert L|RL|', 'Lee|Jennifer C|JC|0000-0003-0506-8349']
D000682:Amyloid D006863:Hydrogen-Ion Concentration D046529:Microscopy, Electron, Transmission D009154:Mutation D010300:Parkinson Disease D011487:Protein Conformation D012965:Sodium Chloride D013059:Spectrum Analysis, Raman D051844:alpha-Synuclein
amyloid fibril Parkinson's disease electron microscopy (EM) mutant