Role of Advanced Glycation on Aggregation and DNA Binding Properties of α-Synuclein

Parkinson's disease (PD) is a neurodegenerative disease with multiple etiologies. Advanced glycation end products (AGEs) accumulate in the aging brain and could be one of the reasons for age-related diseases like PD. Oxidative stress also leads to the formation of AGEs and may be involved in neurodegeneration by altering the properties of proteins. alpha-Synuclein is involved in pathogenesis of PD and there are limited studies on the role of AGE-alpha-synuclein in neurodegeneration. We studied the aggregation and DNA binding ability of AGE-alpha-synuclein in vitro. alpha-Synuclein is glycated using methylglyoxal and formation of AGE-alpha-synuclein is characterized using fluorescence studies, intrinsic tyrosine fluorescence, and fructosamine estimation. The results indicated that AGE-alpha-synuclein aggregates into smaller globular-like aggregates compared to fibrils formed with native alpha-synuclein. Further, it is found that AGE-alpha-synuclein induced conformational changes in scDNA from B-form to B-C-A mixed conformation. Additionally, AGE-alpha-synuclein altered DNA integrity as evidenced by the melting temperature, ethidium bromide, and DNAse I sensitivity studies. AGE-alpha-synuclein converted biphasic T-m to higher monophasic T-m. The T-m of AGE-alpha synuclein-scDNA complex is more than that of native alpha-synuclein-scDNA complex, indicating that AGE-alpha-synuclein stabilized the uncoiled scDNA. AGE-alpha-synuclein could stabilize the uncoiled scDNA, as shown by the decrease in the number of ethidium bromide binding molecules per base pair of DNA. DNAse I sensitive studies indicated that both AGE-alpha-synuclein-scDNA and alpha-synuclein-scDNA are resistant to DNAse I digestion. The relevance of these findings to neuronal cell death is discussed.