title: Apo AI/ABCA1-dependent and HDL3-mediated lipid efflux from compositionally distinct cholesterol-based microdomains.
abstract: We have investigated whether a raft heterogeneity exists in human monocyte-derived macrophages and fibroblasts and whether these microdomains are modulated by lipid efflux. Triton X-100 (Triton) or Lubrol WX (Lubrol) detergent-resistant membranes from cholesterol-loaded monocytes were associated with the following findings: (i) Lubrol-DRM contained most of the cellular cholesterol and at least 75% of Triton-detergent-resistant membranes. (ii) 'Lubrol rafts', defined by their solubility in Triton but insolubility in Lubrol, were enriched in unsaturated phosphatidylcholine and showed a lower cholesterol to choline-phospholipid ratio compared to Triton rafts. (iii) CD14 and CD55 were recovered in Triton- and Lubrol-detergent-resistant membranes, whereas CD11b was found exclusively in Triton DRM. ABCA1 implicated in apo AI-mediated lipid efflux and CDC42 were partially localized in Lubrol- but not in Triton-detergent-resistant membranes. (iv) Apo AI preferentially depleted cholesterol and choline-phospholipids from Lubrol rafts, whereas HDL3 additionally decreased the cholesterol content of Triton rafts. In fibroblasts, neither ABCA1 nor CDC42 was found in Lubrol rafts, and both apo AI and HDL3 reduced the lipid content in Lubrol- as well as in Triton-detergent-resistant membranes. In summary, we provide evidence for the existence of compositionally distinct membrane microdomains in human cells and their modulation by apo AI/ABCA1-dependent and HDL3-mediated lipid efflux.
authors.affiliation: Institute for Clinical Chemistry and Laboratory Medicine, University of Regensburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Drobnik
authors.forename: Hana
authors.initials: H
authors.lastname: Borsukova
authors.forename: Alfred
authors.initials: A
authors.lastname: Böttcher
authors.forename: Alexandra
authors.initials: A
authors.lastname: Pfeiffer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Liebisch
authors.forename: Gerhard J
authors.initials: GJ
authors.lastname: Schütz
authors.forename: Hansgeorg
authors.initials: H
authors.lastname: Schindler
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmitz
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D016632:Apolipoprotein A-I / Q000378:metabolism*; D001692:Biological Transport; D018958:CD55 Antigens / Q000096:biosynthesis; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D050356:Lipid Metabolism; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008871:Microvilli / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D020764:cdc42 GTP-Binding Protein / Q000096:biosynthesis
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D018958:CD55 Antigens; D003902:Detergents; D018950:Lipopolysaccharide Receptors; D008075:Lipoproteins, HDL; D010455:Peptides; D017830:Octoxynol; D002784:Cholesterol; D020764:cdc42 GTP-Binding Protein; D002794:Choline