OVEREXPRESSION OF GLIA MATURATION FACTOR IN C6 CELLS PROMOTES DIFFERENTIATION AND ACTIVATES SUPEROXIDE-DISMUTASE

In order to evaluate the intracellular function of glia maturation fac tor (GMF), we overexpressed GMF in C6 rat glioma cells using two metho ds: stable transfection using the pcDNA3 plasmid, and transient transf ection using replication-defective human adenovirus. With both methods , C6 cells transfected with GMF and overexpressing the protein exhibit a lower saturation density in culture compared to non-transfected or vector alone controls. Transfected cells also exhibit morphological di fferentiation as shown by the outgrowth of cell processes. When inocul ated into nude mice, transfected cells are less tumorigenic than contr ols, and express the mature astrocytic marker glial fibrillary acidic protein. In tissue culture, transfected cells show a 3.5-fold increase in CuZn-dependent superoxide dismutase (CuZnSOD) activity. Western bl ot analysis reveals a 3.5-fold increase in CuZnSOD protein, suggesting an induction of the enzyme. In view of recent findings that reactive oxygen species (ROS) and the antioxidant enzymes are intricately invol ved in key physiologic processes such as proliferation, differentiatio n and apoptosis, the study raises the possibility that CuZnSOD may be a mediator of GMF function.