1,25-Dihydroxyvitamin D3 induces expression of the Wnt signaling co-regulator LRP5 via regulatory elements located significantly downstream of the gene's transcriptional start site

J Steroid Biochem Mol Biol. 2007 Mar;103(3-5):440-5. doi: 10.1016/j.jsbmb.2006.11.018. Epub 2007 Jan 16.

Abstract

Canonical Wnt signaling is essential for bone formation. Activation involves binding of secreted members of the Wnt family of proteins with a membrane receptor Frizzled on osteoblasts, an interaction that is facilitated by LRP5/LRP6 co-receptors. LRP5 is known to play a particularly important role in bone formation such that the loss of this protein results in a reduction in osteoblast number, a delay in mineralization and a reduction in peak BMD. During the course of a VDR ChIP-chip analysis we found that 1,25(OH)(2)D(3) could induce binding of the VDR to sites within the Lrp5 gene locus. Importantly, this interaction between 1,25(OH)(2)D(3)-activated VDR and the Lrp5 gene led to both a modification in chromatin structure within the Lrp5 locus and the induction of LRP5 mRNA transcripts in vivo as well as in vitro. One site within Lrp5 was discovered to confer 1,25(OH)(2)D(3) response to a heterologous promoter in osteoblastic cells, permitting both the identification and characterization of the component VDRE. While the regulatory region in Lrp5 was highly conserved in the human genome, the VDRE was not. Our studies show that 1,25(OH)(2)D(3) can enhance the expression of a critical component of the Wnt signaling pathway which is known to impact osteogenesis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Conserved Sequence
  • Gene Expression Regulation / drug effects*
  • Humans
  • LDL-Receptor Related Proteins / genetics
  • LDL-Receptor Related Proteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • RNA, Messenger / genetics
  • Rats
  • Regulatory Sequences, Nucleic Acid
  • Signal Transduction / drug effects*
  • Transcription, Genetic / genetics*
  • Vitamin D / analogs & derivatives*
  • Vitamin D / pharmacology
  • Wnt Proteins / metabolism*

Substances

  • LDL-Receptor Related Proteins
  • RNA, Messenger
  • Wnt Proteins
  • dihydroxy-vitamin D3
  • Vitamin D