The gene products of two DEGs, measured in blood, have been reported to be associated with PD: PSMC4 (26S proteasome AAA-ATPase subunit Rpt3, a component of the proteasome complex) [83] and COPZ1 (COPI coat complex subunit zeta 1, encoding a subunit of the cytoplasmic coatamer protein complex, which is involved in autophagy and intracellular protein trafficking) [99]. This evidence concerns the gene PSMC4 and Parkinson disease.