ADRENOCORTICOTROPIC-HORMONE-DEPENDENT REGULATION OF A MU-CLASS GLUTATHIONE TRANSFERASE IN MOUSE ADRENOCORTICAL-CELLS

Three different forms of glutathione transferase (GST) have been resol ved in the two mouse adrenal tumour cell lines Y1 and Kin 8. Two of th ese belong to the mu and pi classes respectively. The third form is so far unidentified. In the Y1 cells, the levels of the mu form (mGTmul) and the unidentified form, are both downregulated in the presence of adrenocorticotrophic hormone (ACTH) while the pi form is unaffected. T he Kin 8 cell line is derived from Y1 cells and harbours a defect in t he cyclic AMP (cAMP)-dependent protein kinase, making it refractory to cAMP-dependent regulation of several enzymes. The GST levels in this cell line were unaffected by ACTH. Also, the steady-state levels of mG Tmul mRNA were much lower in Y1 cells treated with forskolin (which ac tivates adenylate cyclase) compared with control cells, but there was no difference in mGTmul mRNA levels between control and forskolin-trea ted Kin 8 cells. This indicates that the ACTH-dependent regulation of the LL class GST is pre-translational and that a functional cAMP-depen dent protein kinase is required for the regulation. We have further sh own that the difference in mRNA steady-state levels between control an d forskolin-treated Y1 cells is abolished when transcription is inhibi ted by actinomycin D. In light of the stability of mGTmul mRNA, it wou ld appear most likely that actinomycin D inhibits the transcription of short-lived factors which regulate the turn-over of mGTmul transcript s in response to changes in intracellular cAMP levels.