ИСТИНА

Aims We studied the effect of posttranslational modifications (glycation and oxidation) of alpha-synuclein and point substitution of a tyrosine residue for a cysteine residue on the amyloid transformation of alpha-synuclein. Method Methods: The wild-type and Cys136-containing fractions of alpha-synuclein were separated using thiol-Sepharose. Results Results: In the absence of reducing agents, Cys136-alpha-synuclein forms dimers due to the disulfide bonding. Both wild-type and Cys136 alpha-synuclein preparations are prone to aggregate during prolonged incubation under shaking at pH 4 and 37°C, but the aggregates produced by either monomeric or dimeric Cys136-AS do not exhibit amyloid properties according to the test with Thioflavin T. Moreover, an admixture of dimeric Cys136-AS prevents the amyloid transformation of the wild-type alpha-synuclein. Wild-type α-synuclein was modified with different sugars methylglyoxal, glyceraldehyde-3-phosphate, glucose, galactose, fructose and ribose-5- phosphate). Most effective glycation of amino acid residues of α-synuclein occurred in the case of 1 mM methylglyoxal or glyceraldehyde-3-phoshate. Glycation of alpha-synuclein by methylglyoxal stimulates protein aggregation, but prevents it amyloid transformation. Conclusion Conclusions: Thus, glycation of α-synuclein which might occur at elevated concentrations of sugars (especially, glyceraldehyde-3-phosphate) in the blood can affect the transformation and aggregation process. We suppose that the effect of point substitutions of amino acids stimulating the formation of dimers of alpha-synuclein should be taken into account to avoid erroneous interpretation of experi ments on amyloid transformation of this protein. This work was supported by Russian Scientific Foundation (grant No 16-14-10027)