title: SCP-2/SCP-x gene ablation alters lipid raft domains in primary cultured mouse hepatocytes.
abstract: Although reverse cholesterol transport from peripheral cell types is mediated through plasma membrane microdomains termed lipid rafts, almost nothing is known regarding the existence, protein/lipid composition, or structure of these putative domains in liver hepatocytes, cells responsible for the net removal of cholesterol from the body. Lipid rafts purified from hepatocyte plasma membranes by a nondetergent affinity chromatography method were: i) present at 33 +/- 3% of total plasma membrane protein; ii) enriched in key proteins of the reverse cholesterol pathway [scavenger receptor class B type I (SR-B1), ABCA1, P-glycoprotein (P-gp), sterol carrier protein-2 (SCP-2)]; iii) devoid of caveolin-1; iv) enriched in cholesterol, sphingomyelin, GM1, and phospholipids low in polyunsaturated fatty acid and double bond index; and v) exhibited an intermediate liquid-ordered lipid phase with significant transbilayer fluidity gradient. Ablation of the gene encoding SCP-2 significantly altered lipid rafts to: i) increase the proportion of lipid rafts present, thereby increasing raft total content of ABCA1, P-gp, and SR-B1; ii) increase total phospholipids while decreasing GM1 in lipid rafts; iii) decrease the fluidity of lipid rafts, consistent with the increased intermediate liquid-ordered phase; and iv) abolish the lipid raft transbilayer fluidity gradient. Thus, despite the absence of caveolin-1 in liver hepatocytes, lipid rafts represented nearly one-third of the mouse hepatocyte plasma membrane proteins and displayed unique protein, lipid, and biophysical properties that were differentially regulated by SCP-2 expression.
authors.affiliation: Department of Physiology and Pharmacology, Texas A&M University, Texas Veterinary Medical Center, College Station, TX 77843-4466, USA.
authors.forename: Barbara P
authors.initials: BP
authors.lastname: Atshaves
authors.forename: Avery L
authors.initials: AL
authors.lastname: McIntosh
authors.forename: H Ross
authors.initials: HR
authors.lastname: Payne
authors.forename: Adalberto M
authors.initials: AM
authors.lastname: Gallegos
authors.forename: Kerstin
authors.initials: K
authors.lastname: Landrock
authors.forename: Nobuyo
authors.initials: N
authors.lastname: Maeda
authors.forename: Ann B
authors.initials: AB
authors.lastname: Kier
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Schroeder
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D001703:Biophysics / Q000379:methods; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D008954:Models, Biological
chemical_list: D064286:ATP Binding Cassette Transporter 1; D018435:ATP Binding Cassette Transporter, Subfamily B; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D005227:Fatty Acids; D008055:Lipids; C072087:sterol carrier proteins