Increased AP-1 DNA binding activity in PC12 cells treated with lead

The possibility that the mechanism of lead neurotoxicity may be at the level of transcription was investigated in PC12 cells. In electrophoretic mobility gel shift assays Pb²⁺ was found to increase activator protein-1 complex (AP-1) DNA binding activity in PC12 cells; the increase was time- and concentration-dependent. Exposure to Pb²⁺ also resulted in an increase in AP-1-driven transcription in cerebellar granule cells transfected with a luciferase gene reporter construct. The increase in AP-1 DNA binding activity by Pb²⁺ required protein synthesis. The increase was mediated by protein kinase C because depletion of protein kinase C and an inhibitor of protein kinase C prevented the increase in AP-1 DNA binding activity by Pb²⁺. Fra- 2 and JunD were found in supershift assays to be the major-components of the AP-1 that was increased by Pb²⁺. In summary, our studies indicate that Pb²⁺ increases AP-1 DNA binding activity in PC12 cells by a pathway that requires protein kinase C and new protein synthesis.