• 5 August 1989
    • journal article
    • research article
    • Vol. 264  (22) , 12867-12871
Abstract
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 encodoing normal subunits 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.

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