StarD7 gene expression in trophoblast cells: contribution of SF-1 and Wnt-beta-catenin signaling

Mol Endocrinol. 2011 Aug;25(8):1364-75. doi: 10.1210/me.2010-0503. Epub 2011 May 26.

Abstract

Steroidogenic acute regulatory protein-related lipid transfer domain containing 7 (StarD7) is a poorly characterized member of the steroidogenic acute regulatory protein-related lipid transfer proteins, up-regulated in JEG-3 cells, involved in intracellular transport and metabolism of lipids. Previous studies dealing with the mechanisms underlying the human StarD7 gene expression led us to define the cis-acting regulatory sequences in the StarD7 promoter using as a model JEG-3 cells. These include a functional T cell-specific transcription factor 4 (TCF4) site involved in Wnt-β-catenin signaling. To understand these mechanisms in more depth, we examined the steroidogenic factor 1 (SF-1) contribution to StarD7 expression. Cotransfection experiments in JEG-3 cells point out that the StarD7 promoter is activated by SF-1, and this effect is increased by forskolin. EMSA using JEG-3 nuclear proteins demonstrated that SF-1 binds to the StarD7 promoter. Additionally, chromatin immunoprecipitation analysis indicated that SF-1 and β-catenin are bound in vivo to the StarD7 promoter. Reporter gene assays in combination with mutations in the SF-1 and TCF4 binding sites revealed that the StarD7 promoter is synergistically activated by SF-1 and β-catenin and that the TCF4 binding site (-614/-608) plays an important role in this activation. SF-1 amino acid mutations involved in the physical interaction with β-catenin abolished this activation; thus demonstrating that the contact between the two proteins is necessary for an efficient StarD7 transcriptional induction. Finally, these data suggest that β-catenin could function as a bridge between SF-1 and TCF4 forming a ternary complex, which would stimulate StarD7 expression. The SF-1 and β-catenin pathway convergence on StarD7 expression may have important implications in the phospholipid uptake and transport, contributing to the normal trophoblast development.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Flanking Region / genetics
  • Animals
  • Binding Sites
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cattle
  • Cell Line
  • Cyclic AMP / pharmacology
  • Gene Expression Regulation* / drug effects
  • Humans
  • Ligands
  • Mutagenesis, Site-Directed
  • Promoter Regions, Genetic / genetics
  • Protein Binding / drug effects
  • Protein Structure, Tertiary
  • Protein Transport / drug effects
  • Signal Transduction* / drug effects
  • Steroidogenic Factor 1 / chemistry
  • Steroidogenic Factor 1 / genetics
  • Steroidogenic Factor 1 / metabolism*
  • Trophoblasts / cytology
  • Trophoblasts / drug effects
  • Trophoblasts / metabolism*
  • Wnt Proteins / metabolism*
  • Wnt Signaling Pathway
  • beta Catenin / metabolism*

Substances

  • Carrier Proteins
  • Ligands
  • STARD7 protein, human
  • Steroidogenic Factor 1
  • Wnt Proteins
  • beta Catenin
  • Cyclic AMP