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

Mol Cell Endocrinol. 2005 Dec 21;245(1-2):23-30. doi: 10.1016/j.mce.2005.09.013. Epub 2005 Nov 18.

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.

MeSH terms

  • Animals
  • Cell Line
  • Cells, Cultured
  • Cholesterol, HDL / physiology
  • Colforsin / pharmacology
  • Cyclic AMP / physiology
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Cyclic AMP Response Element-Binding Protein / physiology*
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / physiology
  • Female
  • Gene Expression Regulation* / drug effects
  • Humans
  • Luteinizing Hormone / physiology
  • Promoter Regions, Genetic / drug effects
  • Promoter Regions, Genetic / genetics
  • Promoter Regions, Genetic / physiology
  • RNA, Messenger / genetics
  • RNA, Messenger / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Scavenger Receptors, Class B / genetics*
  • Scavenger Receptors, Class B / physiology
  • Theca Cells / physiology*
  • Transcriptional Activation*
  • Transfection

Substances

  • Cholesterol, HDL
  • Cyclic AMP Response Element-Binding Protein
  • RNA, Messenger
  • SCARB1 protein, human
  • Scavenger Receptors, Class B
  • Colforsin
  • Luteinizing Hormone
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases