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

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Liver X receptors (LXRs) and their cofactors regulate macrophage cholesterol efflux, a process crucial for preventing atherosclerosis.
• Inflammation disrupts this process, leading to foam cell formation, but the underlying molecular mechanisms are not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms by which inflammation antagonizes LXR-mediated cholesterol efflux.
• To identify key regulatory proteins involved in the repression of the Abca1 gene promoter.

Main Methods:

• Promoter enrichment-quantitative mass spectrometry (PE-QMS) was employed to analyze protein complexes at the Abca1 promoter.
• LXR ligand and binding assays were used to assess protein-DNA interactions.
• RNA polymerase II recruitment and cholesterol efflux assays were performed.

Main Results:

• A subset of proteins was identified that associate with the Abca1 promoter in an LXR-dependent manner.
• Nuclear receptor coactivator 5 (NCOA5) was identified and linked to Toll-like receptor (TLR) signaling.
• NCOA5 functions as an LXR corepressor, attenuating Abca1 expression and cholesterol efflux, particularly under TLR3 stimulation.

Conclusions:

• NCOA5 plays a central role in mediating crosstalk between inflammatory and anti-inflammatory pathways at the Abca1 promoter.
• TLR3-LXR signaling promotes NCOA5 recruitment, leading to the repression of macrophage cholesterol efflux and contributing to atherosclerosis development.