Expression of liver fatty acid binding protein alters plasma membrane lipid composition and structure in transfected L-cell fibroblasts.
Liver fatty acid binding protein, L-FABP, is an abundant protein that binds fatty acids in vitro. The effects of L-FABP on plasma membrane lipid composition, distribution, and physical structure were determined in intact L-cell fibroblasts transfected with cDNA encoding L-FABP. L-FABP expression altered plasma membrane phospholipids by decreasing both phosphatidylethanolamine and esterified oleic acid content, and increasing sphingomyelin. L-FABP also binds sterols and stimulates sterol uptake and esterification. The fluorescent sterol dehydroergosterol was used to examine sterol distribution in the transfected cell plasma membrane. Dehydroergosterol codistributed equally with the cholesterol in both the bulk membrane and the individual bilayer leaflets. The sterol/phospholipid ratio was decreased in the inner leaflet due to sterol depletion. Concomitantly, intermembrane sterol transfer from the rapidly exchangeable lateral sterol domains as measured by exchange of dehydroergosterol, was reduced. The fluidity of the plasma membrane was measured with the fluorescent molecule diphenylhexatriene by multifrequency (1-250 MHz) phase and modulation fluorometry. Both the bulk plasma membrane and the plasma membrane outer leaflet lipids were fluidized in transfected cells. These alterations of plasma membrane structure and composition are consistent with a role for L-FABP in regulating intracellular sterol and fatty acid distribution and thereby membrane lipid domain structure.
Woodford
J K
JK
Department of Pharmacology and Cell Biophysics, University of Cincinnati, OH 45267-0004.
Jefferson
J R
JR
Wood
W G
WG
Hubbell
T
T
Schroeder
F
F
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D004161:Diphenylhexatriene; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D007739:L Cells / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D015394:Molecular Structure; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000032:analysis; D010714:Phosphatidylethanolamines / Q000032:analysis; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D014162:Transfection
D002352:Carrier Proteins; C493320:Fabp1 protein, mouse; C082667:Fabp5 protein, mouse; C086936:Fabp7 protein, mouse; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D008563:Membrane Lipids; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D004161:Diphenylhexatriene; D019301:Oleic Acid