Prion diseases are caused by the conformational transition of the native -helical cellular prion protein (PrP^C) into a -sheet pathogenic isoform. However, the normal physiological function of PrP^C remains elusive. We report here that copper induces PrP^C expression in primary hippocampal and cortical neurons. PrP^C induced by copper has a normal glycosylation pattern, is proteinase K-sensitive and reaches the cell surface attached by a glycosyl phosphatidylinositol anchor. Immunofluorescence analysis revealed that copper induces PrP^C levels in the cell surface and in an intracellular compartment that we identified as the Golgi complex. In addition, copper induced the activity of a reporter vector driven by the rat PrP^C gene (Prnp) promoter stably transfected into PC12 cells, while no effect was observed in glial C6 clones. Also cadmium but not zinc or manganese, up-regulated Prnp promoter activity in PC12 clones. Progressive deletions of the promoter revealed that the region essential for copper modulation contains a putative metal responsive element (MRE). Although electrophoretic mobility shift assay demonstrated nuclear protein binding to this element, supershift analysis showed that this is not a binding site for the metal-responsive transcription factor-1 (MTF-1). The MTF-1-independent transcriptional activation of Prnp is supported by the lack of Prnp promoter activation by zinc. These findings demonstrate that Prnp expression is up-regulated by copper in neuronal cells by an MTF-1-independent mechanism, and suggest a metal-specific modulation of Prnp in neurons.