Glucocorticoid-mediated down regulation of c- fos mRNA in C6 glioma cells: lack of correlation with proenkephalin mRNA

Abstract

We investigated the linkage between the transcriptional factor, c- fos, and expression of proenkephalin in rat C6 glioma cells. C6 cells contained abundant levels of c- fos mRNA. Treatment of cells with dexamethasone resulted in a 10-fold decline in c- fos transcripts and a small increase in proenkephalin mRNA. Combined exposure to dexamethasone and isoproterenol also induced a decrease in c- fos mRNA while proenkephalin mRNA increased 8-fold. Treatment of the C6 cells with phorbol 12-myristate 13-acetate caused a 13-fold increase in c- fos expression 0.5 h after administration and a decrease in proenkephalin mRNA. These data indicate that c- fos and proenkephalin mRNA are not regulated in a sequential, parallel manner, that newly synthesized c- fos is not the determining factor controlling proenkephalin gene regulation, and that c- fos expression is under negative control by glucocorticoids.