SNCA and Parkinson disease: Alpha-synuclein (α-syn) is a 14-kDa synaptic protein with a key role in PD progression (Maroteaux et al., 1988) and it has a high propensity to misfold and aggregate as a response to an increase in its concentration, post-translational modifications, mutations, oxidative stress, pH, and metal ions (Hoyer et al., 2002; Jomova et al., 2010; Oueslati et al., 2010).