title: A functional cross-talk between liver X receptor-α and constitutive androstane receptor links lipogenesis and xenobiotic responses.
abstract: The liver X receptor (LXR) and constitutive androstane receptor (CAR) are two nuclear receptors postulated to have distinct functions. LXR is a sterol sensor that promotes lipogenesis, whereas CAR is a xenosensor that controls xenobiotic responses. Here, we show that LXRα and CAR are functionally related in vivo. Loss of CAR increased the expression of lipogenic LXR target genes, leading to increased hepatic triglyceride accumulation, whereas activation of CAR inhibited the expression of LXR target genes and LXR ligand-induced lipogenesis. On the other hand, a combined loss of LXR α and β increased the basal expression of xenobiotic CAR target genes, whereas activation of LXR inhibited the expression of CAR target genes and sensitized mice to xenobiotic toxicants. The mutual suppression between LXRα and CAR was also observed in cell culture and reporter gene assays. LXRα, like CAR, exhibited constitutive activity in the absence of an exogenously added ligand by recruiting nuclear receptor coactivators. Interestingly, although CAR competed with LXRα for coactivators, the constitutive activity and recruitment of coactivators was not required for CAR to suppress the activity of LXRα. In vivo chromatin immunoprecipitation assay showed that cotreatment of a CAR agonist compromised the LXR agonist responsive recruitment of LXRα to Srebp-1c, whereas an LXR agonist inhibited the CAR agonist-responsive recruitment of CAR to Cyp2b10. In conclusion, our results have revealed dual functions of LXRα and CAR in lipogenesis and xenobiotic responses, establishing a unique role of these two receptors in integrating xenobiotic and endobiotic homeostasis.
authors.affiliation: Key Laboratory for Cell Proliferation and Regulation Biology, Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China.
authors.forename: Yonggong
authors.initials: Y
authors.lastname: Zhai
authors.forename: Tara
authors.initials: T
authors.lastname: Wada
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Shaheen
authors.initials: S
authors.lastname: Khadem
authors.forename: Songrong
authors.initials: S
authors.lastname: Ren
authors.forename: Ramalinga
authors.initials: R
authors.lastname: Kuruba
authors.forename: Song
authors.initials: S
authors.lastname: Li
authors.forename: Wen
authors.initials: W
authors.lastname: Xie
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000090702:Constitutive Androstane Receptor; D005260:Female; D050155:Lipogenesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000071518:Liver X Receptors; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D057093:Orphan Nuclear Receptors / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D020239:Receptor Cross-Talk / Q000187:drug effects / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D015262:Xenobiotics / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000090702:Constitutive Androstane Receptor; D000071518:Liver X Receptors; C000605214:Nr1h3 protein, mouse; D057093:Orphan Nuclear Receptors; D011725:Pyridines; D018160:Receptors, Cytoplasmic and Nuclear; D015262:Xenobiotics; C028474:1,4-bis(2-(3,5-dichloropyridyloxy))benzene