SNCA and Parkinson disease: Thus, to date, it has been demonstrated that proteolytic stress, which is responsible for the presynaptic accumulation of ubiquitinated, misfolded, aggregated and oxidized deposits of alpha synuclein in SN and STR, underlies the initial changes associated with the inevitable development of PD (Irwin et al. 2013; Yoritaka et al. 1996).