出版社：American Society for Biochemistry and Molecular Biology
摘要：Although reverse cholesterol transport from peripheral celltypes is mediated through plasma membrane microdomains termedlipid rafts, almost nothing is known regarding the existence,protein/lipid composition, or structure of these putative domainsin liver hepatocytes, cells responsible for the net removalof cholesterol from the body. Lipid rafts purified from hepatocyteplasma membranes by a nondetergent affinity chromatography methodwere: i) present at 33 ± 3% of total plasma membraneprotein; ii) enriched in key proteins of the reverse cholesterolpathway [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 phospholipidslow in polyunsaturated fatty acid and double bond index; andv) exhibited an intermediate liquid-ordered lipid phase withsignificant transbilayer fluidity gradient. Ablation of thegene encoding SCP-2 significantly altered lipid rafts to: i)increase the proportion of lipid rafts present, thereby increasingraft total content of ABCA1, P-gp, and SR-B1; ii) increase totalphospholipids while decreasing GM1 in lipid rafts; iii) decreasethe fluidity of lipid rafts, consistent with the increased intermediateliquid-ordered phase; and iv) abolish the lipid raft transbilayerfluidity gradient. Thus, despite the absence of caveolin-1 inliver hepatocytes, lipid rafts represented nearly one-thirdof the mouse hepatocyte plasma membrane proteins and displayedunique protein, lipid, and biophysical properties that weredifferentially regulated by SCP-2 expression.Supplementary key words sterol carrier protein • SR-B1 • reverse cholesterol transport • ABCA1
Abbreviations: apoA-I, apolipoprotein A-I; cis-parinaric acid, 9Z,11E,13E,15Z-octatetradecanoic acid; ConA, concanavalin A; DBI, double bond index; DHE, dehydroergosterol; DPH, 1,6-diphenyl-1,3,5-hexatriene; DPH-Pro, 3(1,6-diphenyl-1,3,5-hexatrienyl)-propionic acid; DPH-TMA, 1,6-diphyenyl-1,3,5-hexatrienyl-trimethylammonium; eNOS, endothelial nitic oxide synthase; L-FABP, liver fatty acid binding protein; NBD-stearic acid, 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-octadecanoic acid; PA, phosphatidic acid; PC, choline glycerophospholipid; PE, ethanolamine glycerophospholipid; P-gp, P-glycoprotein; PI, phosphatidylinositol; PS, phosphatidylserine; RCT, reverse cholesterol transport; SCP-2, sterol carrier protein-2; SM, sphingomyelin; SR-B1, scavenger receptor class B type I
