Glucocorticoid and cyclic adenosine 3'5'-monophosphate-mediated induction of cholesterol side-chain cleavage cytochrome P450 (P450scc) in MA-10 tumor Leydig cells. Increases in mRNA are cycloheximide sensitive.
The regulation of cholesterol side-chain cleavage enzyme (P450scc) was investigated in MA-10 tumor Leydig cells. We recently demonstrated that the constitutive and cAMP-stimulated expression of P450scc in normal mouse Leydig cells is negatively regulated by glucocorticoids. We now report that glucocorticoids have the opposite effect in MA-10 cells causing a 1.7-fold increase in the rate of P450scc synthesis and a 2.1-fold increase in the amount of P450scc mRNA. Treatment of MA-10 cells with 10 microM 8-bromo-cAMP (8-Br-cAMP) (cAMP) resulted in a 1.7-fold increase in P450scc synthesis and a 3-fold increase in P450scc mRNA. Combined treatment with dexamethasone and cAMP resulted in additive increases in synthesis (2.8-fold) and mRNA (5.3-fold). Increases in de novo synthesis and mRNA levels were reflected by modest increases in the amount of immunoreactive P450scc enzyme protein. Dexamethasone-mediated stimulation in synthesis and accumulation of P450scc mRNA were blocked by the antiglucocorticoid RU-486. Cycloheximide blocked both cAMP- and dexamethasone-induced increases but had no effect on constitutive levels of P450scc mRNA. Treatment of MA-10 cells with 10 microM 8-Br-cAMP had no effect on cell morphology and stimulated progesterone accumulation to a minor degree. Treatment of MA-10 cells with 1 mM 8-Br-cAMP resulted in cell rounding and loss of cells from culture dishes. The results of this study demonstrate that: 1) dexamethasone increases P450scc de novo synthesis and mRNA levels in MA-10 tumor Leydig cells, opposite to the effect in normal Leydig cells; 2) dexamethasone- and cAMP-stimulated increases occur via distinct mechanisms; 3) and synthesis of protein factor(s) is required to mediate the action of both dexamethasone and cAMP.
Hales
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Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor 48109-0278.
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Payne
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D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000096:biosynthesis* / Q000235:genetics; D000242:Cyclic AMP / Q000494:pharmacology*; D003513:Cycloheximide / Q000494:pharmacology*; D015342:DNA Probes; D003907:Dexamethasone / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007984:Leydig Cell Tumor / Q000201:enzymology*; D015735:Mifepristone / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D011374:Progesterone / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis*; D011965:Receptors, Glucocorticoid / Q000502:physiology; D013739:Testosterone / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015342:DNA Probes; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D015124:8-Bromo Cyclic Adenosine Monophosphate; D015735:Mifepristone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D003907:Dexamethasone; D003513:Cycloheximide; D000242:Cyclic AMP; D002786:Cholesterol Side-Chain Cleavage Enzyme