Localization and regulation of corticotropin receptor expression in the midgestation human fetal adrenal cortex: implications for in utero homeostasis.

Abstract

Developmental changes in the responsiveness of the fetal adrenals to corticotropin (ACTH) play an important role in the regulation of the fetal hypothalamic-pituitary-adrenal axis. Responsiveness of adrenal cortical cells to ACTH is dependent on the extent of ACTH receptor expression. Therefore, we examined the localization and regulation of ACTH receptor expression in the midgestation (16-24 weeks) human fetal adrenal cortex. In situ hybridization analysis was used to localize messenger RNA (mRNA) encoding the ACTH receptor in sections of human fetal adrenal glands. Messenger RNA encoding the ACTH receptor was localized in cells from all cortical zones; abundance was higher in definitive zone than in fetal zone cells and was least abundant in the more central portions of the cortex. Regulation of ACTH receptor expression was studied using Northern blot analysis of total RNA extracted from primary cultures of fetal and definitive zone cells. Two major (1.5 and 3.5 kilobases) and, upon stimulation with ACTH, 3 minor (4.0, 6.0 and 10.0 kb) ACTH receptor mRNA transcripts were detected in RNA from fetal and definitive zone cells. In both cell types, ACTH-(1-24) increased the abundance of mRNA encoding the ACTH receptor 10- to 20-fold compared with untreated cells. The effects of ACTH-(1-24) on ACTH receptor expression in fetal zone cells were time- and dose-dependent. The ED50 for the stimulation of ACTH receptor expression by ACTH-(1-24) was 1-10 pM, and maximal response to 0.1 nm ACTH-(1-24) was detected after 12-16 h. Eight-bromoadenosine cAMP and forskolin also stimulated ACTH receptor expression in fetal zone cells and closely mimicked the effects of ACTH-(1-24). In contrast, stimulation of protein kinase C with 12-O-tetradecanoyl phorbol 13-acetate had no effect on ACTH receptor expression. Changes in ACTH receptor expression in response to ACTH-(1-24), cAMP and forskolin were paralleled by changes in expression of the P450 cholesterol side chain cleavage (P450scc) enzyme. These data demonstrate that expression of the ACTH receptor by the human fetal adrenal cortex is up-regulated by its own ligand and that this effect is mediated by a cAMP-dependent mechanism. In addition, the coordinate stimulation of ACTH receptor and P450scc expression by ACTH indicates that the gene for the ACTH receptor is one of a specific cohort of genes regulated by ACTH that are required to facilitate fetal adrenal cortical response to ACTH. ACTH regulation of its own receptor may represent a mechanism by which fetal adrenal responsiveness to ACTH is maintained and possibly enhanced during fetal development.

The Transcriptional Regulating Protein of 132 kDa (TReP-132) Enhances P450scc Gene Transcription through Interaction with Steroidogenic Factor-1 in Human Adrenal Cells

“…60). It is clear that the temporal and spatial specific expression of this gene is required for steroid synthesis, which is necessary for many physiological processes (6,10,(61)(62)(63). However, relatively little is known about the mechanism(s) of its regulation and the factors involved therein.…”

ACTH-receptor expression, regulation and role in adrenocortial tumor formation

“…Possible involvement of ACTH-receptor expression in adrenocortical development was underlined in recent studies of in situ hybridization experiments in human (44) and baboon fetuses (45). In human fetal adrenal tissue from midgestation, mRNA encoding the ACTH receptor was localized in cells from all cortical zones, with higher abundance in the definite zone (which corresponds to the zona glomerulosa) compared with the fetal zone (reflecting the zona reticularis).…”

A Novel Zinc Finger Protein TReP-132 Interacts with CBP/p300 to Regulate Human CYP11A1 Gene Expression

“…DISCUSSION The regulation of P450scc gene expression is a key determinant of steroid synthesis in steroidogenic tissues, considering that the encoded cytochrome P450scc catalyzes the first step in the steroid synthesis pathway. The tissue-specific expression of P450scc transcript (2, 31) and its regulated expression in response to peptide hormones (8,32,33) demonstrate the importance of transcriptional regulation on P450scc levels. Previous analysis of the 5Ј-flanking region of the human P450scc gene isolated a cis-acting element between nucleotides Ϫ155 and Ϫ131, which activated transcription from the P450scc gene promoter and from the heterologous hsv thymidine kinase gene promoter, when reporter plasmids were transfected into human placental JEG-3 cells.…”