title: Regulation of ATP-binding cassette sterol transporters ABCG5 and ABCG8 by the liver X receptors alpha and beta.
abstract: Mutations in the ATP-binding cassette (ABC) transporters ABCG5 and ABCG8 have recently been shown to cause the autosomal recessive disorder sitosterolemia. Here we demonstrate that the ABCG5 and ABCG8 genes are direct targets of the oxysterol receptors liver X receptor (LXR) alpha and LXRbeta. Diets containing high cholesterol markedly increased the expression of ABCG5/G8 mRNA in mouse liver and intestine. This increase was also observed using synthetic ligands of LXR and its heterodimeric partner, the retinoid X receptor. In situ hybridization analyses of tissues from LXR agonist-treated mice revealed that ABCG5/G8 mRNA is located in hepatocytes and enterocytes and is increased upon LXR activation. In addition, expression of the LXR target gene ABCA1, previously implicated in the control of cholesterol absorption, was also dramatically up-regulated in jejunal enterocytes upon exposure to LXR agonists. These changes in ABC transporter gene expression were not observed in mice lacking LXRs. Furthermore, in the rat hepatoma cell line FTO2B, LXR-dependent transcription of the ABCG5/G8 genes was cycloheximide-resistant, indicating that these genes are directly regulated by LXRs. The addition of ABCG5 and ABCG8 to the growing list of LXR target genes further supports the notion that LXRs serve as sterol sensors to coordinately regulate sterol catabolism, storage, efflux, and elimination.
authors.affiliation: Howard Hughes Medical Institute, Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 75390, USA.
authors.forename: Joyce J
authors.initials: JJ
authors.lastname: Repa
authors.forename: Knut E
authors.initials: KE
authors.lastname: Berge
authors.forename: Chris
authors.initials: C
authors.lastname: Pomajzl
authors.forename: James A
authors.initials: JA
authors.lastname: Richardson
authors.forename: Helen
authors.initials: H
authors.lastname: Hobbs
authors.forename: David J
authors.initials: DJ
authors.lastname: Mangelsdorf
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D015342:DNA Probes; D004268:DNA-Binding Proteins; D008074:Lipoproteins / Q000235:genetics / Q000502:physiology*; D000071518:Liver X Receptors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D057093:Orphan Nuclear Receptors; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D018168:Receptors, Retinoic Acid / Q000502:physiology*; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: C577836:ABCA1 protein, human; C416945:ABCG5 protein, human; C462600:ABCG5 protein, mouse; C416946:ABCG8 protein, human; C462601:ABCG8 protein, mouse; D064286:ATP Binding Cassette Transporter 1; D000071018:ATP Binding Cassette Transporter, Subfamily G, Member 5; D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; D015342:DNA Probes; D004268:DNA-Binding Proteins; D008074:Lipoproteins; D000071518:Liver X Receptors; C000605213:NR1H3 protein, human; C000605214:Nr1h3 protein, mouse; C000605215:Nr1h3 protein, rat; D057093:Orphan Nuclear Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone