Headgroup-specific Exposure of Phospholipids in ABCA1-expressing Cells

• Published in: The Journal of biological chemistry 2005-07, Vol.280 (28), p.26321-26329
• Main Authors: Alder-Baerens, Nele, Müller, Peter, Pohl, Antje, Korte, Thomas, Hamon, Yannick, Chimini, Giovanna, Pomorski, Thomas, Herrmann, Andreas
• Format: Article
• Language: English
• Subjects: Animals; Annexins - metabolism; Apolipoproteins - chemistry; ATP Binding Cassette Transporter 1; ATP-Binding Cassette Transporters - chemistry; ATP-Binding Cassette Transporters - physiology; Calcium - metabolism; Cell Line; Cytoplasm - metabolism; Dogs; Endocytosis; Flow Cytometry; Glyburide - chemistry; Green Fluorescent Proteins - chemistry; Green Fluorescent Proteins - metabolism; HeLa Cells; Humans; Kinetics; Lipid Metabolism; Lipids - chemistry; Phospholipid Transfer Proteins - chemistry; Phospholipids - chemistry; Protein Binding; Protein Structure, Tertiary; Temperature; Time Factors; Transferrin - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M413993200

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.