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MDR1 P-glycoprotein is a lipid translocase of broad specificity, while MDR3 P-glycoprotein specifically translocates phosphatidylcholine.

van Helvoort A., Smith A.J., Sprong H., Fritzsche I., Schinkel A.H., Borst P., van Meer G.

The human MDR1 P-glycoprotein (Pgp) extrudes a variety of drugs across the plasma membrane. The homologous MDR3 Pgp is required for phosphatidylcholine secretion into bile. After stable transfection of epithelial LLC-PK1 cells, MDR1 and MDR3 Pgp were localized in the apical membrane. At 15 degrees C, newly synthesized short-chain analogs of various membrane lipids were recovered in the apical albumin-containing medium of MDR1 cells but not control cells. MDR inhibitors and energy depletion reduced apical release. MDR3 cells exclusively released a short-chain phosphatidylcholine. Since no vesicular secretion occurs at 15 degrees C, the short-chain lipids must have been translocated by the Pgps across the plasma membrane before extraction into the medium by the lipid-acceptor albumin.

Cell 87:507-517(1996) [PubMed] [Europe PMC]