PSMC4 and neurodegenerative disease: Furthermore, a study on neurodegenerative diseases, Psmc4, was also found to be specifically distributed and accumulated in nigrostriatal dopaminergic neuronal cells of Parkinson's patients, suggesting that abnormalities in the ubiquitin-proteasome and autophagy systems may be major players in protein misfolding and aggregation in Parkinson's disease [71].