In PD, numerous proteins associated with protein degradation and ubiquitination were identified: HGS (β = −0.35, P = 2.1 × 10−118), ARRDC3 (β = 0.80, P = 8.9 × 10−82), PSMC5 (β = 0.36, P = 1.4 × 10−56) and USP19 (β = −0.41, P = 1.1 × 10−48) as well as various proteasomes (PSME1, PSMD11 and PSMB4) and kinases (MAPK11, MAPK13 and IRAK4), reinforcing the critical role of the ubiquitin–proteasome system and improper protein phosphorylation in PD pathogenesis20. This evidence concerns the gene PSMB4 and Parkinson disease.