title: Reevaluation of the role of the multidrug-resistant P-glycoprotein in cellular cholesterol homeostasis.
abstract: The multidrug resistance P-glycoprotein (P-gp) was recently proposed to redistribute cholesterol in the plasma membrane, suggesting that P-gp could modulate cholesterol efflux to cholesterol acceptors. To address this hypothesis and to reevaluate the role of P-gp in cholesterol homeostasis, we first analyzed the role of P-gp expression on cholesterol efflux in P-gp stably transfected drug-selected LLC-MDR1 cells. Cholesterol efflux to methyl-beta-cyclodextrin (CD) was 4-fold higher in LLC-MDR1 cells compared with control LLC-PK1 cells, indicating that the accessible pool of plasma membrane cholesterol was increased by P-gp expression. However, using the P-gp-inducible cells lines HeLa MDR-Tet and 77.1 MDR-Tet, cholesterol efflux to CD, apolipoprotein A-I, or HDL was not associated with P-gp expression. In addition, we did not observe any effect of P-gp expression on cellular free and esterified cholesterol content, cholesteryl ester uptake from LDL and HDL particles, or acyl-CoA:cholesterol acyltransferase activity. Therefore, we conclude that P-gp expression does not play a major role in cholesterol homeostasis in P-gp-inducible cells and that the effects of P-gp on cholesterol homeostasis previously described in drug-selected cells might result from non-P-gp pathways that were also induced by selection for drug resistance.
authors.affiliation: Department of Cell Biology NC10, Cleveland Clinic Foundation, Cleveland, OH, USA.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Le Goff
authors.forename: Megan
authors.initials: M
authors.lastname: Settle
authors.forename: Diane J
authors.initials: DJ
authors.lastname: Greene
authors.forename: Richard E
authors.initials: RE
authors.lastname: Morton
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Smith
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D018374:LLC-PK1 Cells; D008563:Membrane Lipids / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013552:Swine; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D008563:Membrane Lipids; D011994:Recombinant Proteins; D002784:Cholesterol; D013752:Tetracycline