Regulation of the cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin mRNAs in cultured choriocarcinoma cells.
Cytochrome P-450scc (P-450scc) catalyzes the cholesterol side-chain cleavage reaction, a rate-limiting enzymatic step for progesterone synthesis in trophoblastic and other steroidogenic cells. Adrenodoxin is the iron/sulfur protein donating electrons to P-450scc during this reaction. We examined the effects of cholera toxin (CT), an activator of adenylate cyclase, and 12-O-tetradecanoylphorbol acetate (TPA), a phorbol ester protein kinase C activator, on the levels of mRNAs encoding P-450scc and adrenodoxin in JEG-3 choriocarcinoma cells. CT induced in a concentration- and time-dependent manner P-450scc and adrenodoxin mRNA levels to 8-fold and 1.5-fold above that of control, respectively. TPA also increased P-450scc and adrenodoxin mRNA levels about 3-fold and 1.5-fold above that of control, respectively. Epidermal growth factor (EGF) was found to weakly induce P-450scc mRNA accumulation with a maximal 20% stimulation above basal levels. The effects of CT and TPA were apparently additive on both mRNAs. The protein synthesis inhibitor cycloheximide diminished basal, CT-, TPA-, and EGF-stimulated P-450scc mRNA accumulation whereas the opposite was observed for the adrenodoxin mRNA. Insulin-like growth factor I (IGF-I) appeared to have no effect on either mRNA. These data indicate that: (1) the accumulation of P-450scc and adrenodoxin mRNAs is mainly controlled by the cyclic adenosine 3',5'-monophosphate (cAMP)-dependent pathway but their stimulation by TPA- and EGF-induced signals may also play a weaker synergistic role; (2) the protein synthesis inhibitor cycloheximide inhibits basal, CT-, TPA- and EGF-stimulated P-450scc mRNA levels while it increases the expression of adrenodoxin mRNA suggesting that in the malignant trophoblasts these two enzyme mRNAs are differentially controlled.
Ritvos
O
O
Department of Pathology, University of Helsinki, Finland.
Voutilainen
R
R
D000325:Adrenodoxin / Q000096:biosynthesis* / Q000235:genetics; D000704:Analysis of Variance; D015152:Blotting, Northern; D002772:Cholera Toxin / Q000494:pharmacology; D002784:Cholesterol / Q000378:metabolism; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000096:biosynthesis* / Q000235:genetics; D002822:Choriocarcinoma / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D000325:Adrenodoxin; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D002772:Cholera Toxin; D002784:Cholesterol; D003513:Cycloheximide; D000242:Cyclic AMP; D002786:Cholesterol Side-Chain Cleavage Enzyme; D013755:Tetradecanoylphorbol Acetate