title: CREM confers cAMP responsiveness in human steroidogenic acute regulatory protein expression in NCI-H295R cells rather than SF-1/Ad4BP.
abstract: Steroidogenic acute regulatory (StAR) protein plays a critical role in steroid hormone synthesis. Tropic hormones induce human StAR gene expression by a cAMP-dependent pathway. Steroidogenic factor-1/adrenal-4-binding protein (SF-1/Ad4BP) plays an important role in the expression of human StAR gene. We investigated the mechanism of cAMP responsiveness in human StAR gene expression in NCI-H295R cells. The StAR promoter activity and protein levels in cells subjected to various treatments were examined. Anti-SF-1/Ad4BP IgG transfection treatment resulted in decreases in the basal StAR promoter activity and StAR protein levels, but did not affect cAMP-stimulated promoter activity and protein levels. The basal and cAMP-stimulated StAR promoter activity levels were reduced in SF-1/Ad4BP mutant (G35E)-transfected cells, but the cAMP induction of StAR promoter activity in response to 1 mM 8-Br-cAMP was not inhibited when G35E SF-1/Ad4BP mutant expression vectors were co-transfected with cAMP-response element-binding (CREB) expression vectors. Although the basal StAR mRNA expression and protein levels were decreased by SF-1/Ad4BP-siRNA treatment, the cAMP-stimulated StAR mRNA expression and protein levels did not change. The basal StAR promoter activity level was not decreased by cAMP-response element modulator (CREM)-siRNA treatment, but the cAMP-stimulated StAR promoter activity level, the magnitude of cAMP induction of StAR promoter, and the cAMP-stimulated StAR protein level were decreased. The cAMP induction of StAR promoter activity in cells was inhibited when S117ACREM mutant expressionvectors were transfected. We conclude that inhibition of the function of SF-1/Ad4BP does not reduce the cAMP induction of StAR promoter activity and protein level. CREM is needed to confer cAMP responsiveness in human StAR protein expression.
authors.affiliation: Department of Biochemistry, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Sugawara
authors.forename: Noriaki
authors.initials: N
authors.lastname: Sakuragi
authors.forename: Hisanori
authors.initials: H
authors.lastname: Minakami
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000302:Adrenal Cortex / Q000378:metabolism*; D000704:Analysis of Variance; D015153:Blotting, Western / Q000379:methods; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D015870:Gene Expression; D005818:Genetic Engineering; D018398:Homeodomain Proteins / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000235:genetics; D006801:Humans; D009154:Mutation; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000235:genetics; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000235:genetics; D014162:Transfection / Q000379:methods; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D018398:Homeodomain Proteins; C515057:NR5A1 protein, human; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; D000098682:Steroidogenic Acute Regulatory Protein; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP