LuXuRies of Lipid Homeostasis: The Unity of Nuclear Hormone Receptors, Transcription Regulation, and Cholesterol Sensing

  Figure 2.
Figure 2.

LXR and FXR as the regulatory yin and yang of intracellular cholesterol turnover. The RXR–LXR dimer becomes a functional transcription factor when either protomeric constituent binds ligand; the blue circle associated with the LXR in the schematic represents 24(S),25-epoxycholesterol. The dimer therefore binds to its cognate nucleotide sequence (i.e., the LXRE) in the promoter of Cyp7a1, a gene crucial to cholesterol catabolism. Activation of the LXRE by the dimer is enabled through an interaction with LRH-1. As cholesterol is shuttled into bile acid (represented by white circle) production, FXR becomes functional as a transcription factor in the expression of the SHP-encoding gene. SHP binds to LRH-1 and limits the effectiveness of the RXR–LXR dimer. For a list of genes that are activated by LXR, see Table 1.

This Article

  1. MI April 2002 vol. 2 no. 2 78-87