A shift from a proteinopathy to a proteinopenia paradigm in neurodegenerative diseases [4] is important in PD since α-synuclein has been attributed to many functions in presynaptic, postsynaptic, and dopaminergic neurotransmission, and has role in neurodegeneration and neuroinflammatory processes [85] (Figure 2). This evidence concerns the gene SNCA and Parkinson disease.