title: The role of cyclic AMP response element binding protein in transactivation of scavenger receptor class B type I promoter in transfected cells and in primary cultures of rat theca-interstitial cells.
abstract: In the ovary, lutropin (LH) stimulates the selective uptake and transport of cholesterol for steroid biosynthesis from HDL particles via the scavenger receptor class B type I (SR-BI). Furthermore the expression of SR-BI mRNA in the ovary is stimulated by LH and cyclic AMP (cAMP). Since the promoter of the rat SR-BI gene is devoid of consensus cyclic AMP response element (CRE) sequences, this study examined if cAMP response element binding protein (CREB) plays a role in the transactivation of SR-BI promoter (SR-BIpr). The transactivation of SR-BIpr was examined in transfected 293T cells and human granulosa SVOG-4o cells, and in primary cultures of rat theca-interstitial cells infected with adenoviral constructs containing the SR-BIpr and a luciferase reporter gene. Dose-related increases in SR-BRpr activity ranging from 2- to 4-fold was induces by 293T cells co-transfected with the catalytic subunit of protein kinase A (cPKA). Co-transfections with CREB and cPKA produced a concentration-dependent increase ranging from 6- to 32-fold. The cAMP-mediated transactivation was significantly attenuated by co-transfection with CREB M1, a non-phosphorylatable, dominant-negative form of CREB. An increase in transactivation of SR-BIpr activity was also seen in SVOG-4o cells co-transfected with CREB. In primary cultures of rat theca-interstitial (T-I) cells infected with an adenoviral construct of SR-BIpr, forskolin produced a marked increase in promoter activity. These data indicate that stimulation of the cAMP-PKA-CREB pathway enhances rat SR-BIpr activity and substantiate the role of CREB as an intermediary in this process. The absence of canonical CRE sequences in the rat SR-BIpr suggests that the activation of SR-BI by CREB may occur either through non-canonical CRE sequences or through additional transcription factors that cooperate with CREB in the activation of SR-BI promoter activity.
authors.affiliation: Department of Obstetrics and Gynecology, 6428 Medical Science I, 1150 West Medical Center Drive, University of Michigan Medical School, Ann Arbor, 48109-0617, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Towns
authors.forename: K M J
authors.initials: KM
authors.lastname: Menon
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D008076:Cholesterol, HDL / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007986:Luteinizing Hormone / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D051122:Scavenger Receptors, Class B / Q000235:genetics* / Q000502:physiology; D013799:Theca Cells / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D008076:Cholesterol, HDL; D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; C495124:SCARB1 protein, human; D051122:Scavenger Receptors, Class B; D005576:Colforsin; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases