alpha-synuclein (α-synuclein), particularly oligomers and protofibrils. Alpha-synuclein is a presynaptic neuronal protein that, in its native state, is soluble and involved in synaptic function. In Parkinson's disease, it misfolds and aggregates into soluble oligomers and insoluble fibrils, which are the main components of Lewy bodies—the pathological hallmark of the disease. These aggregated species are believed to be toxic, contributing to neuronal dysfunction, inflammation, and cell-to-cell transmission of pathology.