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

Abstract

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. α-Synuclein is involved in pathogenesis of PD and there are limited studies on the role of AGE-α-synuclein in neurodegeneration. We studied the aggregation and DNA binding ability of AGE-α-synuclein in vitro. α-Synuclein is glycated using methylglyoxal and formation of AGE-α-synuclein is characterized using fluorescence studies, intrinsic tyrosine fluorescence, and fructosamine estimation. The results indicated that AGE-α-synuclein aggregates into smaller globular-like aggregates compared to fibrils formed with native α-synuclein. Further, it is found that AGE-α-synuclein induced conformational changes in scDNA from B-form to B-C-A mixed conformation. Additionally, AGE-α-synuclein altered DNA integrity as evidenced by the melting temperature, ethidium bromide, and DNAse I sensitivity studies. AGE-α-synuclein converted biphasic Tm to higher monophasic Tm. The Tm of AGE-α-synuclein-scDNA complex is more than that of native α-synuclein-scDNA complex, indicating that AGE-α-synuclein stabilized the uncoiled scDNA. AGE-α-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-α-synuclein-scDNA and α-synuclein-scDNA are resistant to DNAse I digestion. The relevance of these findings to neuronal cell death is discussed.

Structural, morphological, and functional diversity of amyloid oligomers

“…Addition of EGCG to the preformed b-sheet-rich oligomers did not lead to their disaggregation or loss of secondary structure but did inhibit their interaction with membranes [51]. Chemical modifications of a-synuclein, such as methionine oxidation [66,67], intramolecular crosslinking by transglutaminase [68,69], and formation of AGE adducts [70,71], also promoted formation of the disordered oligomers. However, other types of chemical modification (e.g.…”

The role of advanced glycation end products in various types of neurodegenerative disease: a therapeutic approach

“…The AGEs are co-localized with α-syn and accelerate the aggregation process of the protein [61]. Alpha-syn has a total of 15 lysine residues and these are all candidate sites for glycation [61]. The glycation of α-syn influences the nucleation of protein aggregates [61] and induces α-syn oligomerization, thereby stabilizing oligomers.…”

“…RAGE was also found to be expressed in PD patients. The AGEs are co-localized with α-syn and accelerate the aggregation process of the protein [61]. Alpha-syn has a total of 15 lysine residues and these are all candidate sites for glycation [61].…”

“…Alpha-syn has a total of 15 lysine residues and these are all candidate sites for glycation [61]. The glycation of α-syn influences the nucleation of protein aggregates [61] and induces α-syn oligomerization, thereby stabilizing oligomers. This is an important pathological modification of α-syn, because oligomeric species of α-syn are now considered to be more toxic than α-syn aggregates [53].…”

Similarities and interactions between the ageing process and high chronic intake of added sugars

“…Also, neuronal accumulation of AGE has been found in senile plaques and neurofibrillary tangles of Alzheimer's patients (185) and in Lewy's body of Parkinson's patients (186) . Moreover, some proteins implied in neurodegenerative diseases can directly undergo the glycation reaction, which promotes their aggregation; this is the case for Aβ, τ protein and α-synuclein as studied post-mortem or in vitro (187)(188)(189) . AGE, when added in vitro in neuroblastoma cells or injected in vivo in mice, could also raise Aβ level by inducing the expression of precursor protein APP (190) .…”