OSBP-related Protein 8 (ORP8) Suppresses ABCA1 Expression and Cholesterol Efflux from Macrophages*

ORP8 is a previously unexplored member of the family of oxysterol-binding protein-related proteins (ORP). We now report the expression pattern, the subcellular distribution, and data on the ligand binding properties and the physiological function of ORP8. ORP8 is localized in the endoplasmic reticulum (ER) via its C-terminal transmembrane span and binds 25-hydroxycholesterol, identifying it as a new ER oxysterol-binding protein. ORP8 is expressed at highest levels in macrophages, liver, spleen, kidney, and brain. Immunohistochemical analysis revealed ORP8 in the shoulder regions of human coronary atherosclerotic lesions, where it is present in CD68(+) macrophages. In advanced lesions the ORP8 mRNA was up-regulated 2.7-fold as compared with healthy coronary artery wall. Silencing of ORP8 by RNA interference in THP-1 macrophages increased the expression of ATP binding cassette transporter A1 (ABCA1) and concomitantly cholesterol efflux to lipid-free apolipoprotein A-I but had no significant effect on ABCG1 expression or cholesterol efflux to spherical high density lipoprotein HDL2. Experiments employing an ABCA1 promoter-luciferase reporter confirmed that ORP8 silencing enhances ABCA1 transcription. The silencing effect was partially attenuated by mutation of the DR4 element in the ABCA1 promoter and synergized with that of the liver X receptor agonist T0901317. Furthermore, inactivation of the E-box in the promoter synergized with ORP8 silencing, suggesting that the suppressive effect of ORP8 involves both the liver X receptor and the E-box functions. Our data identify ORP8 as a negative regulator of ABCA1 expression and macrophage cholesterol efflux. ORP8 may, thus, modulate the development of atherosclerosis.

[1]  V. Olkkonen,et al.  The mammalian oxysterol-binding protein-related proteins (ORPs) bind 25-hydroxycholesterol in an evolutionarily conserved pocket. , 2007, The Biochemical journal.

[2]  J. Gustafsson,et al.  Molecular basis for repression of liver X receptor-mediated gene transcription by receptor-interacting protein 140. , 2007, The Biochemical journal.

[3]  Joseph L. Goldstein,et al.  Sterol-regulated transport of SREBPs from endoplasmic reticulum to Golgi: Oxysterols block transport by binding to Insig , 2007, Proceedings of the National Academy of Sciences.

[4]  R. Hegele,et al.  Selective Up-regulation of LXR-regulated Genes ABCA1, ABCG1, and APOE in Macrophages through Increased Endogenous Synthesis of 24(S),25-Epoxycholesterol* , 2007, Journal of Biological Chemistry.

[5]  T. Terasaki,et al.  24S‐hydroxycholesterol induces cholesterol release from choroid plexus epithelial cells in an apical‐ and apoE isoform‐dependent manner concomitantly with the induction of ABCA1 and ABCG1 expression , 2007, Journal of neurochemistry.

[6]  D. Russell,et al.  Enzymatic reduction of oxysterols impairs LXR signaling in cultured cells and the livers of mice. , 2007, Cell metabolism.

[7]  Andrew J. Brown,et al.  SREBP-2 positively regulates transcription of the cholesterol efflux gene, ABCA1, by generating oxysterol ligands for LXR. , 2006, The Biochemical journal.

[8]  A. Vaughan,et al.  ATP-Binding cassette cholesterol transporters and cardiovascular disease. , 2006, Circulation research.

[9]  M. Mäyränpää,et al.  Desquamation of human coronary artery endothelium by human mast cell proteases: implications for plaque erosion , 2006, Coronary artery disease.

[10]  A. Tall,et al.  Decreased Atherosclerosis in Low-Density Lipoprotein Receptor Knockout Mice Transplanted With Abcg1−/− Bone Marrow , 2006, Arteriosclerosis, thrombosis, and vascular biology.

[11]  T. V. van Berkel,et al.  Macrophage ABCG1 Deletion Disrupts Lipid Homeostasis in Alveolar Macrophages and Moderately Influences Atherosclerotic Lesion Development in LDL Receptor-Deficient Mice , 2006, Arteriosclerosis, thrombosis, and vascular biology.

[12]  Andrew C. Li,et al.  Impaired Development of Atherosclerosis in Hyperlipidemic Ldlr−/− and ApoE−/− Mice Transplanted With Abcg1−/− Bone Marrow , 2006, Arteriosclerosis, thrombosis, and vascular biology.

[13]  Peter Libby,et al.  The immune response in atherosclerosis: a double-edged sword , 2006, Nature Reviews Immunology.

[14]  N. Ridgway,et al.  Oxysterol-binding protein and vesicle-associated membrane protein-associated protein are required for sterol-dependent activation of the ceramide transport protein. , 2006, Molecular biology of the cell.

[15]  M. Jauhiainen,et al.  The OSBP-related proteins (ORPs): global sterol sensors for co-ordination of cellular lipid metabolism, membrane trafficking and signalling processes? , 2006, Biochemical Society transactions.

[16]  M. Hayden,et al.  Macrophage ATP-Binding Cassette Transporter A1 Overexpression Inhibits Atherosclerotic Lesion Progression in Low-Density Lipoprotein Receptor Knockout Mice , 2006, Arteriosclerosis, thrombosis, and vascular biology.

[17]  P. Tontonoz,et al.  Liver X receptors as integrators of metabolic and inflammatory signaling. , 2006, The Journal of clinical investigation.

[18]  Joseph L. Goldstein,et al.  Protein Sensors for Membrane Sterols , 2006, Cell.

[19]  B. Nordestgaard,et al.  Mutation in ABCA1 predicted risk of ischemic heart disease in the Copenhagen City Heart Study Population. , 2005, Journal of the American College of Cardiology.

[20]  James H. Hurley,et al.  Structural mechanism for sterol sensing and transport by OSBP-related proteins , 2005, Nature.

[21]  P. Libby,et al.  Pathophysiology of Coronary Artery Disease , 2005, Circulation.

[22]  T. Langmann,et al.  Transcriptional regulatory networks in lipid metabolism control ABCA1 expression. , 2005, Biochimica et biophysica acta.

[23]  S. Yokoyama.  Assembly of high density lipoprotein by the ABCA1/apolipoprotein pathway. , 2005, Current opinion in lipidology.

[24]  Ping-yuan Wang,et al.  OSBP Is a Cholesterol-Regulated Scaffolding Protein in Control of ERK1/2 Activation , 2005, Science.

[25]  Andrew C. Li,et al.  PPAR- and LXR-dependent pathways controlling lipid metabolism and the development of atherosclerosis Published, JLR Papers in Press, October 16, 2004. DOI 10.1194/jlr.R400010-JLR200 , 2004, Journal of Lipid Research.

[26]  P. Kovanen,et al.  Proteolysis of pericellular matrix: a process linking inflammation to plaque destabilization and rupture. , 2004, Arteriosclerosis, thrombosis, and vascular biology.

[27]  Andrew J. Brown,et al.  Statins Inhibit Synthesis of an Oxysterol Ligand for the Liver X Receptor in Human Macrophages With Consequences for Cholesterol Flux , 2004, Arteriosclerosis, thrombosis, and vascular biology.

[28]  F. Foufelle,et al.  SREBP transcription factors: master regulators of lipid homeostasis. , 2004, Biochimie.

[29]  L. Csiba,et al.  Transcriptional Regulation of Human CYP27 Integrates Retinoid, Peroxisome Proliferator-Activated Receptor, and Liver X Receptor Signaling in Macrophages , 2004, Molecular and Cellular Biology.

[30]  V. Olkkonen.  Oxysterol binding protein and its homologues: new regulatory factors involved in lipid metabolism , 2004, Current opinion in lipidology.

[31]  V. Olkkonen,et al.  Oxysterols and oxysterol binding proteins: role in lipid metabolism and atherosclerosis , 2004, Annals of medicine.

[32]  A. Tall,et al.  Retinoic Acid Receptor-Mediated Induction of ABCA1 in Macrophages , 2003, Molecular and Cellular Biology.

[33]  C. Argmann,et al.  Enhanced Synthesis of the Oxysterol 24(S),25-Epoxycholesterol in Macrophages by Inhibitors of 2,3-Oxidosqualene:Lanosterol Cyclase: A Novel Mechanism for the Attenuation of Foam Cell Formation , 2003, Circulation research.

[34]  Kenneth R Feingold,et al.  Endotoxin down-regulates ABCG5 and ABCG8 in mouse liver and ABCA1 and ABCG1 in J774 murine macrophages: differential role of LXR. , 2003, Journal of lipid research.

[35]  C. Glass,et al.  Promoter-Specific Roles for Liver X Receptor/Corepressor Complexes in the Regulation of ABCA1 and SREBP1 Gene Expression , 2003, Molecular and Cellular Biology.

[36]  M. Hayden,et al.  Efflux and Atherosclerosis: The Clinical and Biochemical Impact of Variations in the ABCA1 Gene , 2003, Arteriosclerosis, thrombosis, and vascular biology.

[37]  X. Hu,et al.  Liver X receptors interact with corepressors to regulate gene expression. , 2003, Molecular endocrinology.

[38]  D. Mangelsdorf,et al.  Liver X receptor signaling pathways in cardiovascular disease. , 2003, Molecular endocrinology.

[39]  V. Olkkonen,et al.  The OSBP-related proteins: a novel protein family involved in vesicle transport, cellular lipid metabolism, and cell signalling. , 2003, Biochimica et biophysica acta.

[40]  S. Wright,et al.  Bacterial lipopolysaccharide induces expression of ABCA1 but not ABCG1 via an LXR-independent pathway. , 2002, Journal of lipid research.

[41]  I. Björkhem,et al.  Oxysterols: Friends, Foes, or Just Fellow Passengers? , 2002, Arteriosclerosis, thrombosis, and vascular biology.

[42]  W. Fung-Leung,et al.  Leukocyte ABCA1 controls susceptibility to atherosclerosis and macrophage recruitment into tissues , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[43]  O. Francone,et al.  Increased Atherosclerosis in Hyperlipidemic Mice With Inactivation of ABCA1 in Macrophages , 2002, Arteriosclerosis, thrombosis, and vascular biology.

[44]  H. Brewer,et al.  The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene. , 2002, Journal of lipid research.

[45]  A. Li,et al.  A family of 12 human genes containing oxysterol-binding domains. , 2001, Genomics.

[46]  Gaochao Zhou,et al.  27-Hydroxycholesterol Is an Endogenous Ligand for Liver X Receptor in Cholesterol-loaded Cells* , 2001, The Journal of Biological Chemistry.

[47]  E. Ikonen,et al.  The OSBP-related protein family in humans. , 2001, Journal of lipid research.

[48]  I. Rodriguez,et al.  Molecular and Biochemical Characterization of a Novel Oxysterol-binding Protein (OSBP2) Highly Expressed in Retina* , 2001, The Journal of Biological Chemistry.

[49]  M. Pfaffl,et al.  A new mathematical model for relative quantification in real-time RT-PCR. , 2001, Nucleic acids research.

[50]  G. Chisolm,et al.  Oxidized LDL-induced injury and apoptosis in atherosclerosis. Potential roles for oxysterols. , 2001, Trends in cardiovascular medicine.

[51]  A. Tall,et al.  Sterol-dependent transactivation of the ABC1 promoter by the liver X receptor/retinoid X receptor. , 2000, The Journal of biological chemistry.

[52]  Andrew J. Brown,et al.  Oxysterols and atherosclerosis. , 1999, Atherosclerosis.

[53]  Timothy M. Willson,et al.  Activation of the Nuclear Receptor LXR by Oxysterols Defines a New Hormone Response Pathway* , 1997, The Journal of Biological Chemistry.

[54]  D. Mangelsdorf,et al.  An oxysterol signalling pathway mediated by the nuclear receptor LXRα , 1996, Nature.

[55]  R. Lees,et al.  Homozygous Tangier disease and cardiovascular disease. , 1994, Atherosclerosis.

[56]  C. Slaughter,et al.  cDNA cloning and expression of oxysterol-binding protein, an oligomer with a potential leucine zipper. , 1989, The Journal of biological chemistry.

[57]  P. Dawson,et al.  Purification of oxysterol binding protein from hamster liver cytosol. , 1989, The Journal of biological chemistry.

[58]  F. Taylor,et al.  Use of oxygenated sterols to probe the regulation of 3-hydroxy-3-methylglutaryl-CoA reductase and sterologenesis. , 1985, Methods in enzymology.

[59]  F. Taylor,et al.  Correlation between oxysterol binding to a cytosolic binding protein and potency in the repression of hydroxymethylglutaryl coenzyme A reductase. , 1984, Journal of Biological Chemistry.

[60]  R. Havel,et al.  The distribution and chemical composition of ultracentrifugally separated lipoproteins in human serum. , 1955, The Journal of clinical investigation.