An LXR-NCOA5 gene regulatory complex directs inflammatory crosstalk-dependent repression of macrophage cholesterol efflux

EMBO J. 2015 May 5;34(9):1244-58. doi: 10.15252/embj.201489819. Epub 2015 Mar 9.

Abstract

LXR-cofactor complexes activate the gene expression program responsible for cholesterol efflux in macrophages. Inflammation antagonizes this program, resulting in foam cell formation and atherosclerosis; however, the molecular mechanisms underlying this antagonism remain to be fully elucidated. We use promoter enrichment-quantitative mass spectrometry (PE-QMS) to characterize the composition of gene regulatory complexes assembled at the promoter of the lipid transporter Abca1 following downregulation of its expression. We identify a subset of proteins that show LXR ligand- and binding-dependent association with the Abca1 promoter and demonstrate they differentially control Abca1 expression. We determine that NCOA5 is linked to inflammatory Toll-like receptor (TLR) signaling and establish that NCOA5 functions as an LXR corepressor to attenuate Abca1 expression. Importantly, TLR3-LXR signal crosstalk promotes recruitment of NCOA5 to the Abca1 promoter together with loss of RNA polymerase II and reduced cholesterol efflux. Together, these data significantly expand our knowledge of regulatory inputs impinging on the Abca1 promoter and indicate a central role for NCOA5 in mediating crosstalk between pro-inflammatory and anti-inflammatory pathways that results in repression of macrophage cholesterol efflux.

Keywords: LXR; NCOA5; atherosclerosis; inflammation; quantitative mass spectrometry.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter 1 / genetics*
  • ATP Binding Cassette Transporter 1 / metabolism
  • Animals
  • Cholesterol / metabolism*
  • Female
  • Gene Expression Regulation
  • Inflammation / genetics
  • Inflammation / metabolism
  • Liver X Receptors
  • Macrophages / metabolism*
  • Mass Spectrometry / methods
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Nuclear Receptor Coactivators / genetics*
  • Nuclear Receptor Coactivators / metabolism
  • Orphan Nuclear Receptors / genetics*
  • Orphan Nuclear Receptors / metabolism
  • Promoter Regions, Genetic
  • RNA Polymerase II / metabolism
  • Signal Transduction
  • Toll-Like Receptor 3 / genetics
  • Toll-Like Receptor 3 / metabolism

Substances

  • ABCA1 protein, mouse
  • ATP Binding Cassette Transporter 1
  • Liver X Receptors
  • NCOA5 protein, mouse
  • Nuclear Receptor Coactivators
  • Orphan Nuclear Receptors
  • TLR3 protein, mouse
  • Toll-Like Receptor 3
  • Cholesterol
  • RNA Polymerase II