USP19 and Parkinson disease: 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.