EXPRESSION OF GLUTATHIONE AND GAMMA-GLUTAMYLCYSTEINE SYNTHETASE MESSENGER-RNA IS JUN DEPENDENT

The gene GLCLC encodes the catalytic subunit of gamma-glutamylcysteine synthetase (glutamate-cysteine ligase E.C. 6.3.2.2), the rate limitin g enzyme for glutathione synthesis. When HepGP cells were exposed to t he serine/threonine phosphatase inhibitor okadaic acid (OA), increased expression of GLCLC was observed, as was the development of resistanc e to xenobiotic induced GSH depletion. Okadaic acid is known to activa te both NF-kappa B and AP-1 activity. Inhibition of NF-kappa B activit y by overexpression of an I kappa B alpha transdominant inhibitor or e xposure to the protease inhibitor TLCK did not inhibit the OA mediated increase in GLCLC transcripts. Fibroblasts derived from a mouse conta ining a c-Jun null mutation exhibited diminished AP-1 binding activity , reduced levels of GLCLC message, and a correspondingly low GSH conce ntration compared to wild type cells. When the null cells, which expre ss Jun B and Jun D, were exposed to OA, AP-1 binding activity increase d, as did expression of GLCLC message. These results indicate that AP- 1 transcription factors participate in the regulation of glutathione m etabolism. (C) 1997 Academic Press.