title: Headgroup-specific exposure of phospholipids in ABCA1-expressing cells.
abstract: ABCA1 has been established to be required for the efflux of cholesterol and phospholipids to apolipoproteins such as apoA-I. At present, it is unclear whether ABCA1-mediated lipid exposure is specific with regard to lipid headgroups and whether it requires calcium activation and the presence of a lipid acceptor. In the present work, we found exofacial exposure of endogenous phosphatidylserine in the absence of apoA-I to be enhanced in ABCA1-GFP expressing MDCKII and HeLa cells compared with control cells. By using C6-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) (NBD)-labeled phospholipid analogues, we observed elevated redistribution of phosphatidylserine and phosphatidylethanolamine but not of phosphatidylcholine analogues from the cytoplasmic to the exoplasmic leaflet of the plasma membrane of ABCA1-GFP expressing cells. Whereas glyburide affected neither the level of exofacial endogenous PS nor the outward movement of the amino phospholipid analogues, the latter was sensitive to intracellular Ca2+ in ABCA1-GFP expressing cells, further enhancing outward analogue redistribution with respect to control cells. Both receptor-mediated endocytosis and fluidphase endocytosis were reduced in MDCKII cells expressing ABCA1-GFP. Glyburide raised the level of receptor-mediated endocytosis in the ABCA1-GFP expressing cell to the level of control cells in the absence of glyburide. In control cells, however, fluid-phase endocytosis but not receptor-mediated endocytosis was significantly reduced upon glyburide treatment.
authors.affiliation: Humboldt University of Berlin, Institute of Biology, Center of Biophysics and Bioinformatics, Invalidenstrasse 42, 10115 Berlin, Germany.
authors.forename: Nele
authors.initials: N
authors.lastname: Alder-Baerens
authors.forename: Peter
authors.initials: P
authors.lastname: Müller
authors.forename: Antje
authors.initials: A
authors.lastname: Pohl
authors.forename: Thomas
authors.initials: T
authors.lastname: Korte
authors.forename: Yannick
authors.initials: Y
authors.lastname: Hamon
authors.forename: Giovanna
authors.initials: G
authors.lastname: Chimini
authors.forename: Thomas
authors.initials: T
authors.lastname: Pomorski
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000502:physiology*; D000818:Animals; D017302:Annexins / Q000378:metabolism; D001053:Apolipoproteins / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D004285:Dogs; D004705:Endocytosis; D005434:Flow Cytometry; D005905:Glyburide / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D049294:Phospholipid Transfer Proteins / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013696:Temperature; D013997:Time Factors; D014168:Transferrin / Q000737:chemistry
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D017302:Annexins; D001053:Apolipoproteins; D008055:Lipids; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D014168:Transferrin; D049452:Green Fluorescent Proteins; D005905:Glyburide; D002118:Calcium