Features of Cross-Seeding of Wild-Type Alpha-Synuclein and Its Mutant Form A53T Potentially Useful for the Development of Test Systems.

Since the features of cross-seeding of alpha-synuclein forms may affect the sensitivity and specificity of the test systems, we developed a modified approach to obtain alpha-synuclein amyloid seeds with particle sizes from 20 to 50 nm prepared from either the wild-type protein (α-synWT) or its more fibrillation-prone form A53T (α-synA53T). These seeds had optimal properties for subsequent initiation of fibrillation. Our data showed that the elevated efficiency of alpha-synuclein A53T monomer transformation was hardly affected by the type of used seeds, whereas the addition of the seeds obtained from the alpha-synuclein mutant form to wild-type protein monomers had a significantly smaller effect than α-synWT seeds. Transmission electron microscopy data revealed that in the presence of α-synWT seeds the wild-type alpha-synuclein formed long and wide fibrils, while the addition of α-synA53T seeds led to the formation of long, but thin fibrils. Since the lag period of α-synA53T monomer fibrillation was significantly reduced compared to the wild-type protein, the replacing of α-synWT with α-synA53T in current assay systems designed to detect aberrant forms of α-synuclein in biological fluid samples (e.g., RT-QuIC) could substantially cut the time of analysis. In the future, a set of alpha-synuclein mutant forms could be used for the differential diagnosis of synucleinopathies caused by the different mutations of this protein.