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

Area of Science:

• Neuroscience
• Molecular Biology
• Toxicology

Background:

• Lead neurotoxicity is a significant public health concern.
• The precise molecular mechanisms underlying lead's effects on the nervous system are not fully understood.
• Investigating transcriptional regulation offers a potential pathway to elucidate lead's neurotoxic effects.

Purpose of the Study:

• To investigate whether lead affects neurotoxicity at the level of transcription.
• To identify the specific molecular pathways involved in lead-induced transcriptional changes.
• To determine the role of activator protein-1 (AP-1) in lead neurotoxicity.

Main Methods:

• Electrophoretic mobility gel shift assays (EMSA) were used to assess AP-1 DNA binding activity.
• Luciferase gene reporter assays were employed in cerebellar granule cells to measure AP-1-driven transcription.
• Experiments involved varying lead concentrations and exposure times.
• Protein kinase C (PKC) depletion and inhibition were utilized to probe signaling pathways.
• Supershift assays identified specific AP-1 components.

Main Results:

• Lead (Pb2+) significantly increased AP-1 DNA binding activity in PC12 cells in a time- and concentration-dependent manner.
• Pb2+ exposure led to enhanced AP-1-driven transcription in cerebellar granule cells.
• The observed increase in AP-1 DNA binding activity required de novo protein synthesis.
• Protein kinase C (PKC) mediated the Pb2+-induced increase in AP-1 DNA binding, as PKC depletion and inhibition blocked the effect.
• Fra-2 and JunD were identified as the primary AP-1 components upregulated by Pb2+.

Conclusions:

• Lead exposure modulates gene transcription by increasing activator protein-1 (AP-1) DNA binding activity.
• The mechanism involves a pathway requiring protein kinase C and new protein synthesis.
• These findings provide insights into the molecular basis of lead neurotoxicity at the transcriptional level.