title: Expression of the mouse gonadotropin-releasing hormone receptor gene in alpha T3-1 gonadotrope cells is stimulated by cyclic 3',5'-adenosine monophosphate and protein kinase A, and is modulated by Steroidogenic factor-1 and Nur77.
abstract: Regulation of GnRH receptor (GnRHR) expression levels in the pituitary is a crucial control point in reproduction. The promoter of the mouse GnRHR gene contains nuclear receptor half-sites (NRS) at -244/-236 and -15/-7 relative to the translation start site. Although binding of steroidogenic factor-1 (SF-1) to the -244/-236NRS is implicated in mediating basal and gonadotrope-specific expression, no function or protein-DNA interactions have previously been described for the -15/-7NRS. We report that levels of the endogenous GnRHR mRNA in alpha T3-1 cells are stimulated by forskolin and 8-bromo-cAMP. We also show that the orphan nuclear receptor Nur77 is expressed in alpha T3-1 cells, and that both SF-1 and Nur77 bind to the -15/-7NRS and -244/-236NRS in vitro. We show that the activity of the proximal (-579/+1) mouse GnRHR promoter is up-regulated by protein kinase A, via a mechanism that is modulated by SF-1, both positively and negatively, through binding to the -244/-236NRS or the -15/-7NRS, respectively. Nur77 appears to be capable of acting as a negative regulator of this response, via the -15/-7NRS. Furthermore, we show that forskolin up-regulates SF-1 mRNA levels in alpha T3-1 cells, indicating that the levels of SF-1 play a role in modulating the protein kinase A response.
authors.affiliation: Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa.
authors.forename: Hanél
authors.initials: H
authors.lastname: Sadie
authors.forename: Gustav
authors.initials: G
authors.lastname: Styger
authors.forename: Janet
authors.initials: J
authors.lastname: Hapgood
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D051717:Fushi Tarazu Transcription Factors; D005786:Gene Expression Regulation / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D018398:Homeodomain Proteins; D006801:Humans; D051379:Mice; D009479:Neuropeptides / Q000494:pharmacology; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D010902:Pituitary Gland / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D011966:Receptors, LHRH / Q000235:genetics*; D011987:Receptors, Steroid; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000502:physiology*; D024363:Transcription Initiation Site; D014407:Tumor Cells, Cultured
chemical_list: C495401:ADCYAP1 protein, human; C495402:Adcyap1 protein, mouse; D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; C539821:NR4A1 protein, human; C515057:NR5A1 protein, human; D009479:Neuropeptides; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011966:Receptors, LHRH; D011987:Receptors, Steroid; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse; D005576:Colforsin; D007987:Gonadotropin-Releasing Hormone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases