Steroidogenic factor 1 differentially regulates basal and inducible steroidogenic gene expression and steroid synthesis in human adrenocortical H295R cells.
The significance of steroidogenic factor 1 (SF-1) in adrenal steroidogenesis was studied using adrenocortical cell lines transformed with a dominant negative mutant of SF-1. Constitutive expression of the mutant did not only impair the activity of endogenous SF-1 but also diminish its own expression, suggesting that SF-1 was under autoregulation. Inhibition of the endogenous SF-1 activity significantly reduced basal and inducible transcription of CYP17, CYP21B and CYP11B1, but exhibited little effects on StAR and CYP11A1 expression. Stimulating the transformed cells with potassium and cAMP freed CYP11B2 from the mutant-caused transcriptional inhibition, whereas the transformation abolished induction of CYP17 by both stimulants. Consistent with the transcriptional changes of steroidogenic genes, basal and inducible synthesis of cortisol and androgens drastically declined in the transformed cell lines. The relief of CYP11B2 repression following the potassium and cAMP stimulation removed the restraint the mutant exerted on aldosterone synthesis, and resulted in aldosterone overproduction in the stimulated transformed cells. SF-1 also plays a role in regulating the adrenocorticotrophic hormone (ACTH) responsiveness of the adrenocortical cells. Inhibition of SF-1 activity significantly decreased basal expression of ACTH receptor and its induction by potassium and cAMP.
Li
Lih-Ann
LA
Division of Environmental Health and Occupational Medicine, National Health Research Institutes, 100 Shih-Chuan 1st Rd, Kaohsiung 807, Taiwan, ROC. lihann@nhri.org.tw
Chang
Yu-Cheng
YC
Wang
Chien-Jen
CJ
Tsai
Feng-Yuan
FY
Jong
Shiang-Bin
SB
Chung
Bon-Chu
BC
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D002461:Cell Line, Transformed; D000242:Cyclic AMP / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D004789:Enzyme Activation; D051717:Fushi Tarazu Transcription Factors; D005786:Gene Expression Regulation; D005799:Genes, Dominant; D018398:Homeodomain Proteins; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D018043:Receptors, Corticotropin / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013252:Steroid 11-beta-Hydroxylase / Q000096:biosynthesis; D013254:Steroid 17-alpha-Hydroxylase / Q000096:biosynthesis; D054339:Steroidogenic Factor 1; D013256:Steroids / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D018043:Receptors, Corticotropin; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D013256:Steroids; D014157:Transcription Factors; D012313:RNA; D011189:Potassium Chloride; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D013254:Steroid 17-alpha-Hydroxylase; D013252:Steroid 11-beta-Hydroxylase; D011188:Potassium