Increased expression of prion protein is associated with changes in dopamine metabolism and MAO activity in PC12 cells

Prion diseases of humans and animals occur following infection with infectious agents containing PrPSc or in situations in which there is a mutation of the prion protein (PrP) gene. The cellular prion protein (PrPC) is a sialoglycoprotein that is expressed predominantly in neurons. PrPC is converted into a pathogenic form of PrP (PrPSc), which is distinguishable from PrPC by its relative resistance to protease digestion. A number of postulates have been advanced for the function of normal PrP (PrPC), but this issue has not been resolved. To investigate the function(s) of PrPC, we established clonal PC12 cell lines, which have elevated PrPC expression. The results show that there were alterations in dopamine metabolism and in monoamine oxidase (MAO) activity in transfected PC12 cells that overexpress PrPC. There was an increase in concentration of DOPAC, a metabolite of dopamine, and in MAO activity in cells overexpressing PrPC. MAO is involved in oxidative degradation of dopamine (DA). Our data suggest that PrPC plays a role in DA metabolism by regulating MAO activity.