Prostaglandin F2α-induced Expression of 20α-Hydroxysteroid Dehydrogenase Involves the Transcription Factor NUR77

Abstract

Prostaglandin F 2 ␣ (PGF 2 ␣) binding to its receptor on the rat corpus luteum triggers various signal transduction pathways that lead to the activation of a steroidogenic enzyme, 20␣-hydroxysteroid dehydrogenase (20␣-HSD), which in turn catabolizes progesterone. The molecular mechanism underlying PGF 2 ␣-induced 20␣-HSD enzyme activity has not yet been explored. In this report we show, using mice lacking PGF 2 ␣ receptor and pregnant rats, that PGF 2 ␣ is responsible for the rapid and massive expression of the 20␣-HSD gene at the end of pregnancy leading to a decrease in progesterone secretion. We also present evidence that PGF 2 ␣ enhances 20␣-HSD promoter activity. We have determined a region upstream of the ؊1590 position in the 20␣-HSD promoter that confers regulation by PGF 2 ␣ in ovarian primary cells. This region encompasses a unique transcription factor-binding site with a sequence of a NUR77 response element. Deletion of this motif or overexpression of a NUR77 dominant negative protein caused a complete loss of 20␣-HSD promoter activation by PGF 2 ␣. NUR77 also transactivated the 20␣-HSD promoter in transient transfection experiments in corpus luteumderived cells (GG-CL). This induction required the NUR77-transactivating domain. We also show that PGF 2 ␣ induces a very rapid expression of NUR77 that binds to a distal response element located at ؊1599/ ؊1606 but does not interact with another proximal putative NUR77 response element located downstream in the promoter. A rapid increase in NUR77 mRNA was observed in mice corpora lutea just before parturition at a time when 20␣-HSD becomes expressed. This increase in the expression of both genes was not seen in PGF 2 ␣ receptor knockout mice. By using cyclosporin A and PGF 2 ␣ treatment, we established that inhibition of NUR77 DNA binding in vivo prevents PGF 2 ␣ induction of the 20␣-HSD gene in the corpus luteum. Taken together, our results demonstrate, for the first time, that PGF 2 ␣ induces in the corpus luteum the expression of the nuclear orphan receptor and transcription factor, NUR77, which in turn leads to the transcriptional stimulation of 20␣-HSD, triggering the decrease in serum progesterone essential for parturition.In all mammalian species, progesterone plays an essential role in reproduction. The precise timing of both the synthesis and degradation of this steroid hormone is crucial for reproductive success. The expression of enzymes implicated in the synthesis and catabolism of progesterone, therefore, needs to be accurately regulated during the different reproductive states of the animal. In rodents, the corpus luteum, which is the only source of progesterone throughout pregnancy (1), is also able to express the enzyme 20␣-hydroxysteroid dehydrogenase (20␣-HSD)1 that converts progesterone into a biologically inactive steroid, thus playing a key role in the termination of pregnancy and allowing parturition to occur (2). Due to the detrimental effect of 20␣-HSD on luteal progesterone secretion, the corpus luteum of pregnancy does not express...

Human chorionic gonadotropin-dependent induction of an equine aldo-keto reductase (AKR1C23) with 20α-hydroxysteroid dehydrogenase activity during follicular luteinization in vivo

“…However, most ovarian studies remained largely at the level of the corpus luteum. Early investigations on the luteolytic effects of PGF 2 showed that 20 -HSD activity is induced 150-fold in the rat ovary (Strauss & Stambaugh 1974), this being consistent with more recent findings that demonstrate that rat 20 -HSD (AKR1C8) is induced by PGF 2 (Stocco et al 2000). The transcription factor Nur77 was shown to play a key role in the PGF 2 -dependent induction of 20 -HSD (AKR1C8) in rat luteal cells (Stocco et al 2000).…”

“…Moreover, because of confusion regarding nomenclature, difficulties lie in identifying precisely which AKR was being studied in previous publications. Many reports addressed the regulation of AKRs speculated to have 20 -HSD activity in various tissues, including the ovary (Strauss & Stambaugh 1974, Lacy et al 1993, Albarracin et al 1994, Stocco et al 2000, Pelletier et al 2003. However, most ovarian studies remained largely at the level of the corpus luteum.…”

“…Although the precise molecular control of AKR1C23 induction in preovulatory follicles remains to be elucidated, it is interesting to note that the luteinization/ovulatory process is accompanied by an induction of PGF 2 and Nur77 (Sirois & Doré 1997, Park et al 2003. Given their putative role in 20 -HSD expression (Strauss & Stambaugh 1974, Stocco et al 2000, it will be interesting to determine whether they Figure 7 Immunohistochemical localization of AKR1C23 in equine preovulatory follicles. Immunohistochemistry was performed on formalin-fixed sections of preovulatory follicles isolated at 0 and 39 h after hCG treatment and of equine testicular tissues, as described in Materials and methods.…”

Anti-steroidogenic Factor ARR19 Inhibits Testicular Steroidogenesis through the Suppression of Nur77 Transactivation

“…Regulation of testicular steroidogenesis in Leydig cells is mediated through multiple signaling pathways and nuclear factors that generate both positive and negative effects on steroidogenic response (8,(37)(38)(39). The cAMP-dependent protein kinase A signaling pathway is a major pathway for testicular steroidogenesis, which is primarily controlled by the pituitary gonadotropin LH in Leydig cells.…”

“…LH/cAMP stimulates steroidogenesis by increasing the expression of steroidogenic enzyme genes (1). Recently, it was demonstrated that LH induces Nur77 gene expression in Leydig cells (2), and Nur77 in turn regulates the expression of steroidogenic enzyme genes (3-6) such as cytochrome P450 protein 17, the steroid 21-hydroxylase, and 20-␣-hydroxysteroid dehydrogenase (7,8), suggesting an important role for Nur77 in testicular steroidogenesis.…”