The impact of glycation on fibrillation and stability of α-synuclein: An introspection into the role of dietary AGEs in cellular amyloidogenesis

Non-enzymatic protein glycation from dietary carbohydrate sources leads to misfolding and aggregation of cellular proteins often enhancing their amyloidogenic behaviour. In the present work, we investigated the fibrillation potential and other biophysical attributes of glycated α-synuclein, a presynaptic chaperone whose misfolding is implicated in neurodegenerative disorders. Glycation was carried out in vitro with Methyl glyoxal (MG), a highly reactive dicarbonyl formed as a metabolic by-product from carbohydrates, lipids and proteins. α-synuclein was glycated maximally within 96 hrs with a concomitant increase in thermostability and fibrillation potential. Dynamic Light Scattering and native PAGE indicated that glycated α-synuclein formed bigger aggregates, and the monomeric protein was barely detectable. In FTIR spectra, the amide I vibrational bands for the control protein incubated for 48 hrs and 96 hrs were obtained at 1645 cm -1 and 1643 cm -1 respectively characteristic of random coil conformation due to thermal denaturation. In the corresponding glycated samples, the same bands were shifted to 1642 cm -1 and 1632 cm -1 indicative of transition to β-pleated sheet. In the CD spectra, both the control as well as the glycated alpha-synuclein revealed an extended conformation typical of the α to β transition. Glycated α-synuclein also demonstrated increased fibrillation as assessed by Thioflavin-T fluorescence. The results provide useful insights to understand the strong clinical correlation between diabetes and neurodegeneration in the perspective of glycated α-synuclein.