title: Direct interaction of nuclear liver X receptor-beta with ABCA1 modulates cholesterol efflux.
abstract: Cholesterol is an essential component of eukaryotic cells; at the same time, however, hyperaccumulation of cholesterol is harmful. Therefore, the ABCA1 gene, the product of which mediates secretion of cholesterol, is highly regulated at both the transcriptional and post-transcriptional levels. The transcription of ABCA1 is regulated by intracellular oxysterol concentration via the nuclear liver X receptor (LXR)/retinoid X receptor (RXR); once synthesized, ABCA1 protein turns over rapidly with a half-life of 1-2 h. Here, we show that the LXRbeta/RXR complex binds directly to ABCA1 on the plasma membrane of macrophages and modulates cholesterol secretion. When cholesterol does not accumulate, ABCA1-LXRbeta/RXR localizes on the plasma membrane, but is inert. When cholesterol accumulates, oxysterols bind to LXRbeta, and the LXRbeta/RXR complex dissociates from ABCA1, restoring ABCA1 activity and allowing apoA-I-dependent cholesterol secretion. LXRbeta can exert an immediate post-translational response, as well as a rather slow transcriptional response, to changes in cellular cholesterol accumulation. Thus, we provide the first demonstration that protein-protein interaction suppresses ABCA1 function. Furthermore, we show that LXRbeta is involved in both the transcriptional and post-transcriptional regulation of the ABCA1 transporter.
authors.affiliation: Laboratory of Cellular Biochemistry, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Hozoji
authors.forename: Youichi
authors.initials: Y
authors.lastname: Munehira
authors.forename: Yuika
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Makishima
authors.forename: Michinori
authors.initials: M
authors.lastname: Matsuo
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kioka
authors.forename: Kazumitsu
authors.initials: K
authors.lastname: Ueda
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D001692:Biological Transport; D019921:Biotinylation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D000071518:Liver X Receptors; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D057093:Orphan Nuclear Receptors; D025941:Protein Interaction Mapping; D034622:RNA Interference; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D013997:Time Factors
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D002784:Cholesterol
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