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NERVOUS SYSTEM CELL BIOLOGY

Induction of cellular prion protein gene expression by copper in neurons

¹Centro de Regulación Celular y Patología "Joaquín V. Luco", and ²Millenium Institute for Fundamental and Applied Biology, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile; ³Ludwig Institute for Cancer Research, São Paulo; and ⁴Departamento de Bioquímica, Instituto de Química da Universidade de São Paulo, São Paulo, Brazil

Submitted 6 April 2005 ; accepted in final form 31 August 2005

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 herein 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, whereas no effect was observed in glial C6 clones. Also cadmium, but not zinc or manganese, upregulated 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. 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 upregulated by copper in neuronal cells by an MTF-1-independent mechanism, and suggest a metal-specific modulation of Prnp in neurons.

neuronal cells; Prnp; phosphatidylinositol-specific phospholipase; metal responsive element; metal responsive transcription factor-1

This article has been cited by other articles:

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