The Human 3β-Hydroxysteroid Dehydrogenase/Δ5-Δ4 Isomerase Type 2 Promoter Is a Novel Target for the Immediate Early Orphan Nuclear Receptor Nur77 in Steroidogenic Cells

Abstract

The human (h) 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase type 2 (3beta-HSD2) enzyme, encoded by the hHSD3B2 gene, is mainly found in gonads and adrenals. This enzyme catalyzes an essential early step in the biosynthesis of all classes of steroid hormones. The critical nature of the enzyme is supported by the occurrence of human syndromes that are associated with insufficient 3beta-HSD2 expression and/or activity. Although the need for a functional 3beta-HSD2 enzyme is indisputable, the molecular mechanisms that regulate HSD3B2 expression (both basal and hormone-induced) in steroidogenic cells remain poorly understood. A role for the Nur77 family of immediate-early orphan nuclear receptors in steroidogenesis has received recent interest. For example, Nur77 is present in gonads and adrenals, where its expression is robustly and rapidly induced by hormones that stimulate steroidogenic gene expression. Moreover, the expression patterns of Nur77 and at least one key steroidogenic gene (hHSD3B2) closely parallel one another. We now report that the hHSD3B2 promoter is indeed a novel target for Nur77 in both testicular Leydig cells and adrenal cells. We have mapped a novel response element located at -130 bp specific for Nur77 and not other orphan nuclear receptors (steroidogenic factor-1 and liver receptor homolog-1) previously shown to regulate hHSD3B2 promoter activity. This Nur77 element is essential and sufficient to confer Nur77 responsiveness to the hHSD3B2 promoter, and its mutation blunts basal and hormone-induced hHSD3B2 promoter activity in steroidogenic cells. We also show that Nur77 synergizes with all members of the steroid receptor coactivator family of coactivators on the hHSD3B2 promoter. Taken together, our identification of Nur77 as an important regulator of HSD3B2 promoter activity helps us to better define the tissue-specific and hormonal regulation of the HSD3B2 gene in steroidogenic cells.

Modulation of steroidogenic gene expression and hormone synthesis in H295R cells exposed to PCP and TCP

“…Most steroidogenic genes, including StAR, CYP11A, CYP11B, CYP17 and CYP21 are cAMPdependent (Sewer and Waterman, 2001). 3ˇHSD2 in H295R cells can be induced in H295R cells by stimulation of cAMP (Martin and Tremblay, 2005). In the study reported upon here, concentra-tion of cAMP in H295R cells was significantly less and expression of several key steroidogenic genes was down-regulated.…”

Adrenocortical LDL receptor function negatively influences glucocorticoid output

“…Although other transcription factors such as GATA family members and the nuclear receptor liver receptor homolog 1 (NR5A2) are also able to modulate the promoter activity of HSD3B2, it has been established that the growth-factorinducible immediate early gene nur/77 (NUR77) and steroidogenic factor 1 (SF1 (NR5A1)) are essential for maintaining basal HSD3B2 transcription in human adrenocortical cells (Leers-Sucheta et al 1997, Martin & Tremblay 2005, Udhane et al 2013). The relative mRNA expression level of NUR77 and SF1 was not significantly different between our two adrenal transplants (data not shown).…”

Glucocorticoids antagonize cAMP-induced Star transcription in Leydig cells through the orphan nuclear receptor NR4A1

“…Martin et al 2008. Of all these factors, the orphan nuclear receptor NR4A1 was shown to be rapidly and strongly induced in response to LH/cAMP in Leydig cells (Song et al 2001, Martin & Tremblay 2005, Martin et al 2008.…”

“…Their expression is rapidly and strongly induced by various stimuli in numerous tissues, including hormonally stimulated steroidogenic cells (Davis & Lau 1994, Song et al 2001, Li et al 2004, Martin & Tremblay 2005. NR4A1 transactivation potential is also modulated by posttranslational modifications (Davis et al 1993, Hirata et al 1993, Li & Lau 1997, Wingate & Arthur 2006 and/ or modulation of its intracellular localization in response to certain stimuli (Klopotowska et al 2005).…”

“…NR4A1 binds DNA as a monomer to the sequence AAAAGGTCA, called NR4A1 response element (NBRE), that is very similar to that recognized by the nuclear receptor steroidogenic factor 1 (NR5A1, SF1; Wilson et al 1993), an essential regulator of expression of many steroidogenic genes (reviewed in Parker et al 2002, Val et al 2003. In Leydig cells, NR4A1 has been found to regulate genes involved in steroidogenesis (Zhang & Mellon 1997, Bassett et al 2004, Havelock et al 2005, Martin & Tremblay 2005, including Star (Martin et al 2008).…”