Plasminogen gene expression is regulated by nerve growth factor.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Neurite outgrowth, crucial for neural development and repair, requires an intact plasminogen (Plg) activation system.
• Nerve growth factor (NGF) is a key regulator of neuronal survival, differentiation, and neurite outgrowth.

Purpose of the Study:

• To investigate the effect of NGF on Plg synthesis in NGF-responsive PC-12 cells.
• To elucidate the molecular mechanisms underlying NGF-induced Plg gene expression.

Main Methods:

• Western blotting, quantitative PCR, and luciferase reporter assays were used to assess Plg expression and promoter activity.
• Site-directed mutagenesis, electrophoretic mobility shift assays, and chromatin immunoprecipitation identified key regulatory elements and transcription factors.
• Signaling pathway inhibitors (PD98059, wortmannin) and dominant-negative Ras mutants were employed to dissect signaling cascades.

Main Results:

• NGF treatment significantly increased Plg expression (3-fold) and Plg mRNA levels (6.82-fold) in PC-12 cells and cortical neurons.
• NGF-induced Plg promoter activity was dependent on Ras/ERK and PI3K signaling pathways.
• Two Sp1 binding sites within the Plg promoter (-255 to -106) were identified as critical for the NGF response, with Sp1 binding to the endogenous promoter.

Conclusions:

• NGF upregulates plasminogen gene expression in neuronal cells.
• This upregulation involves Ras/ERK and PI3K signaling pathways and Sp1 transcription factor binding to the Plg promoter.
• The findings suggest a novel mechanism by which neurotrophins enhance their effects through the proteolytic activity of plasmin.