Abstract: The 17‐kDa endogenous brain protein glia maturation factor (GMF) was transfected into C6 rat glioma cells using a replication‐defective human adenovirus vector. The cells overexpressed GMF but did not secrete the protein into the medium. Transfection with GMF led to the activation of the transcription factor nuclear factor‐κB (NF‐κB), as evidenced by electrophoretic mobility shift assay of the nuclear extract, using a double‐stranded oligonucleotide probe containing the consensus binding sequence for NF‐κB. The specificity of binding was demonstrated by competition with unlabeled probe and by the nonbinding of the mutant probe. Binding was detectable as early as 3 h after transfection, peaked at 6 and 12 h, and gradually declined thereafter. The observed NF‐κB activation was reduced by cotransfection with catalase and by the presence of high concentrations of pyruvate in the medium, suggesting the involvement of H₂O₂. The p38 mitogen‐activated protein kinase inhibitor SB‐203580 also suppressed the GMF‐activated NF‐κB, suggesting the involvement of the p38 signal transduction cascade. On the other hand, the phorbol ester phorbol 12‐myristate 13‐acetate activated NF‐κB whether or not GMF was overexpressed. Along with NF‐κB activation was an enhanced expression of superoxide dismutase (SOD), which was suppressed if NF‐κB nuclear translocation was blocked by its specific decoy DNA, implicating NF‐κB as an upstream mediator of this anti‐oxidant enzyme. The p38 inhibitor SB‐203580 also blocked the GMF‐activated SOD. As NF‐κB and SOD are both pro‐survival signals, the results suggest a cytoprotective role for endogenous GMF in glial cells.