The roles of cAMP and cAMP-dependent protein kinase in the expression of cholesterol side chain cleavage and steroid 11 beta-hydroxylase genes in mouse adrenocortical tumor cells.
The expression of the genes encoding cholesterol side chain cleavage enzyme (SCC) and steroid 11 beta-hydroxylase (11 beta-OHase) was examined in Y1 mouse adrenocortical tumor cells and in derivative cell lines defective in cAMP-dependent protein kinase activity. Y1 cells expressed both genes constitutively, and treatment with 8-bromo-cAMP (8-Br-cAMP) increased expression 5-10-fold. In three independent protein kinase mutants, expression of SCC and 11 beta-OHase was impaired to degrees dependent upon the severity of defect in cAMP-dependent protein kinase activity. In Kin-2, the least impaired mutant clone, basal expression of SCC was the same as in Y1 cells. Treatment of Kin-2 with 8-Br-cAMP increased SCC RNA to the levels seen in stimulated Y1 cells. In contrast, clone Kin-8, the most severe mutant, expressed markedly diminished basal and 8-Br-cAMP-stimulated levels of SCC mRNA. Kin-7 had basal and 8-Br-cAMP-stimulated levels of SCC mRNA which were intermediate to Kin-2 and Kin-8. None of the Kin mutants constitutively expressed detectable levels of 11 beta-OHase transcripts, and only Kin-2 responded to treatment with 8-Br-cAMP with increased expression of 11 beta-OHase; however, the time course of induction in Kin-2 was significantly delayed. The disparate patterns of expression of SCC and 11 beta-OHase in the Kin mutants suggest that these genes differ in their absolute requirement for cAMP-dependent protein kinase activity. Experiments also were performed in which Kin-7 and Kin-8 mutants were restored to cAMP-responsive states by transfection with genes encoding normal sub-units of cAMP-dependent protein kinase. These phenotypic revertants recovered 8-Br-cAMP-inducible expression of SCC and 11 beta-OHase. These results strongly support the hypothesis that impaired expression of steroidogenic enzymes in the Kin mutants results directly from defects in cAMP-dependent protein kinase activity.
Wong
M
M
Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
Rice
D A
DA
Parker
K L
KL
Schimmer
B P
BP
D000306:Adrenal Cortex Neoplasms / Q000201:enzymology* / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics*; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000502:physiology*; D005786:Gene Expression Regulation; D051379:Mice; D009154:Mutation; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000502:physiology*; D013252:Steroid 11-beta-Hydroxylase / Q000235:genetics*; D013250:Steroid Hydroxylases / Q000235:genetics*; D014407:Tumor Cells, Cultured / Q000201:enzymology
D000242:Cyclic AMP; D013250:Steroid Hydroxylases; D013252:Steroid 11-beta-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D011494:Protein Kinases