title: Long-chain fatty acid uptake into adipocytes depends on lipid raft function.
abstract: This study investigates the role of lipid rafts and caveolae, a subclass of lipid raft microdomains, in the binding and uptake of long-chain fatty acids (LCFA) by 3T3-L1 cells during differentiation. Disruption of lipid rafts by beta-cyclodextrin (betaCD) or selective inhibition of caveolae by overexpression of a dominant-negative mutant of caveolin-3 (Cav(DGV)) resulted in disassembly of caveolae structures at the cell surface, as assessed by electron microscopy. While in 3T3-L1 fibroblasts, which express few caveolae, Cav(DGV) or betaCD had no effect on LCFA uptake, in 3T3-L1 adipocytes the same treatments decreased the level of [(3)H]oleic acid uptake by up to 55 +/- 8 and 49 +/- 7%, respectively. In contrast, cholesterol loading of 3T3-L1 adipocytes resulted in a 4-fold increase in the extent of caveolin-1 expression and a 1.7-fold increase in the level of LCFA uptake. Both the inhibitory and enhancing effects of these treatments were constantly increasing with the [(3)H]oleic acid incubation time up to 5 min. Incubation of 3T3-L1 adipocytes with [(3)H]stearate followed by isolation of a caveolin-1 positive detergent-resistant membrane (DRM) fraction revealed that [(3)H]stearate binds to caveolae. Fatty acid translocase (FAT/CD36) was found to be present in this DRM fraction as well. Our data thus strongly indicate a critical involvement of lipid rafts in the binding and uptake of LCFA into 3T3-L1 adipocytes. Furthermore, our findings suggest that caveolae play a pivotal role in lipid raft-dependent LCFA uptake. This transport mechanism is induced in conjunction with cell differentiation and might be mediated by FAT/CD36.
authors.affiliation: Department of Internal Medicine IV, Ruprechts-Karls-University, Heidelberg, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Pohl
authors.forename: Axel
authors.initials: A
authors.lastname: Ring
authors.forename: Robert
authors.initials: R
authors.lastname: Ehehalt
authors.forename: Henning
authors.initials: H
authors.lastname: Schulze-Bergkamen
authors.forename: Arno
authors.initials: A
authors.lastname: Schad
authors.forename: Paul
authors.initials: P
authors.lastname: Verkade
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Stremmel
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D018955:CD36 Antigens / Q000378:metabolism; D002210:Caprylates / Q000378:metabolism; D021941:Caveolae / Q000187:drug effects / Q000378:metabolism; D051244:Caveolin 3; D022461:Caveolins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D002784:Cholesterol / Q000378:metabolism / Q000494:pharmacology; D002793:Cholic Acids / Q000494:pharmacology; D003505:Cyclodextrins / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D019301:Oleic Acid / Q000378:metabolism; D013229:Stearic Acids / Q000378:metabolism; D047392:beta-Cyclodextrins
chemical_list: D018955:CD36 Antigens; D002210:Caprylates; C495548:Cav3 protein, mouse; D051244:Caveolin 3; D022461:Caveolins; D002793:Cholic Acids; D003505:Cyclodextrins; D003902:Detergents; D005227:Fatty Acids; D013229:Stearic Acids; D047392:beta-Cyclodextrins; D019301:Oleic Acid; C031183:stearic acid; D002784:Cholesterol; C031215:betadex; C031492:octanoic acid; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate