SNCA and Parkinson disease: The elevation of oxidative stress, due to the ROS-mediated oxidation of methionine residues, facilitates the aggregation of α-synuclein into amyloid fibrils, reduces proteasomal degradation, and promotes the formation of Lewy bodies, the main histopathological hallmark of PD, responsible for various neurotoxic effects on neurons of the dopaminergic pathways.