Chicken ovalbumin upstream promoter-transcription factor is a negative regulator of steroidogenesis in bovine adrenal glomerulosa cells.
The octapeptide hormone, angiotensin II (AngII) and ACTH stimulate mineralocorticoid biosynthesis in the zona glomerulosa of the adrenal cortex in part by promoting the transcription of the gene coding for the steroidogenic acute regulatory (StAR) protein. We have examined whether chicken ovalbumin upstream promoter-transcription factor (COUP-TF), a member of the orphan nuclear receptor family of transcription factors, is involved in this transcriptional regulation. We analyzed COUP-TF and StAR mRNA and protein levels in bovine adrenal glomerulosa cells in primary culture. COUP-TF protein was readily detectable in nonstimulated cells, and AngII markedly reduced its expression in a time- and concentration-dependent manner (IC50 = 1 nm), to 46 +/- 4.4% of control levels after 6 h, (n = 3; P < 0.01). This repression was paralleled by a marked decrease in COUP-TF mRNA levels, reaching 18 +/- 8.8% of controls (n = 3, P < 0.01) after 6 h and by a 20-fold increase in aldosterone output. In bovine glomerulosa cells overexpressing COUP-TFI and -II, the induction of StAR mRNA and protein elicited by AngII was completely suppressed to control levels, and the aldosterone response was significantly reduced (from 4.8 +/- 1.1-fold the basal value in mock-infected cells to 1.9 +/- 0.5-fold and 2.2 +/- 0.7-fold in COUP-TFI- and COUP-TFII-expressing cells, respectively; n = 3; P < 0.01 for both differences). Finally, by using electrophoretic mobility shift assays and chromatin immunoprecipitation, we have shown a direct interaction between COUP-TF and the proximal StAR promoter. These results suggest that COUP-TF exerts a tonic inhibition on steroidogenesis by repressing StAR protein expression and that activators of aldosterone biosynthesis lift this inhibition in part by repressing COUP-TF levels.
Buholzer
Carine F
CF
Division of Endocrinology, Diabetology, and Nutrition, University Hospital, 24 rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland.
Arrighi
Jean-François
JF
Abraham
Shahnaz
S
Piguet
Vincent
V
Capponi
Alessandro M
AM
Casal
Andérs J
AJ
D000450:Aldosterone / Q000096:biosynthesis* / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D051838:COUP Transcription Factor I; D051837:COUP Transcription Factor II; D051836:COUP Transcription Factors; D002417:Cattle; D002478:Cells, Cultured; D002645:Chickens; D005576:Colforsin / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D008901:Mineralocorticoids / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015384:Zona Glomerulosa / Q000187:drug effects / Q000378:metabolism*; D000098682:Steroidogenic Acute Regulatory Protein
D051838:COUP Transcription Factor I; D051837:COUP Transcription Factor II; D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins; D008901:Mineralocorticoids; D010750:Phosphoproteins; D012333:RNA, Messenger; D011987:Receptors, Steroid; D014157:Transcription Factors; D000098682:Steroidogenic Acute Regulatory Protein; D000804:Angiotensin II; D005576:Colforsin; D000450:Aldosterone