title: Differential regulation of human 3β-hydroxysteroid dehydrogenase type 2 for steroid hormone biosynthesis by starvation and cyclic AMP stimulation: studies in the human adrenal NCI-H295R cell model.
abstract: Human steroid biosynthesis depends on a specifically regulated cascade of enzymes including 3β-hydroxysteroid dehydrogenases (HSD3Bs). Type 2 HSD3B catalyzes the conversion of pregnenolone, 17α-hydroxypregnenolone and dehydroepiandrosterone to progesterone, 17α-hydroxyprogesterone and androstenedione in the human adrenal cortex and the gonads but the exact regulation of this enzyme is unknown. Therefore, specific downregulation of HSD3B2 at adrenarche around age 6-8 years and characteristic upregulation of HSD3B2 in the ovaries of women suffering from the polycystic ovary syndrome remain unexplained prompting us to study the regulation of HSD3B2 in adrenal NCI-H295R cells. Our studies confirm that the HSD3B2 promoter is regulated by transcription factors GATA, Nur77 and SF1/LRH1 in concert and that the NBRE/Nur77 site is crucial for hormonal stimulation with cAMP. In fact, these three transcription factors together were able to transactivate the HSD3B2 promoter in placental JEG3 cells which normally do not express HSD3B2. By contrast, epigenetic mechanisms such as methylation and acetylation seem not involved in controlling HSD3B2 expression. Cyclic AMP was found to exert differential effects on HSD3B2 when comparing short (acute) versus long-term (chronic) stimulation. Short cAMP stimulation inhibited HSD3B2 activity directly possibly due to regulation at co-factor or substrate level or posttranslational modification of the protein. Long cAMP stimulation attenuated HSD3B2 inhibition and increased HSD3B2 expression through transcriptional regulation. Although PKA and MAPK pathways are obvious candidates for possibly transmitting the cAMP signal to HSD3B2, our studies using PKA and MEK1/2 inhibitors revealed no such downstream signaling of cAMP. However, both signaling pathways were clearly regulating HSD3B2 expression.
authors.affiliation: Department of Pediatrics, Division of Pediatric Endocrinology and Diabetology, University Children's Hospital, Berne, Switzerland.
authors.forename: Sameer
authors.initials: S
authors.lastname: Udhane
authors.forename: Petra
authors.initials: P
authors.lastname: Kempna
authors.forename: Gaby
authors.initials: G
authors.lastname: Hofer
authors.forename: Primus E
authors.initials: PE
authors.lastname: Mullis
authors.forename: Christa E
authors.initials: CE
authors.lastname: Flück
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D050980:GATA Transcription Factors / Q000378:metabolism; D005786:Gene Expression Regulation; D023061:Gene Order; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1 / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics; D011375:Progesterone Reductase / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D000072260:RNA Splicing Factors; D020218:Response Elements; D015398:Signal Transduction; D013217:Starvation / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D050980:GATA Transcription Factors; D012739:Gonadal Steroid Hormones; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D000072260:RNA Splicing Factors; C107467:SF1 protein, human; D014157:Transcription Factors; D000242:Cyclic AMP; C533068:3 beta-hydroxysteroid dehydrogenase type II; D011375:Progesterone Reductase; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases