Understanding the Modulation of α-Synuclein Fibrillation by -Acetyl Aspartate: A Brain Metabolite.

α-Synuclein (α-Syn) fibrillation is a prominent contributor to neuronal deterioration and plays a significant role in the advancement of Parkinson's Disease (PD). Considering this, the exploration of novel compounds that can inhibit or modulate the aggregation of α-Syn is a topic of significant research. This study, for the first time, elucidated the effect of -acetyl aspartate (NAA), a brain osmolyte, on α-Syn aggregation using spectroscopic and microscopic approaches. Thioflavin T (ThT) assay revealed that a lower concentration of NAA inhibits α-Syn aggregation, whereas higher concentrations of NAA accelerate the aggregation. Further, this paradoxical effect of NAA was complemented by ANS, RLS, and the turbidity assay. The secondary structure transition was more pronounced at higher concentrations of NAA by circular dichroism, corroborating the fluorescence spectroscopic observations. Confocal microscopy also confirmed the paradoxical effect of NAA on α-Syn aggregation. Interaction studies including fluorescence quenching and molecular docking were employed to determine the binding affinity and critical residues involved in the α-Syn-NAA interaction. The explanation for this paradoxical nature of NAA could be a solvophobic effect. The results offer a profound understanding of the modulatory mechanism of α-Syn aggregation by NAA, thereby suggesting the potential role of NAA at lower concentrations in therapeutics against α-Syn aggregation-related disorders.