Kowal R C, Herz J, Weisgraber K H, Mahley R W, Brown M S, Goldstein J L
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
J Biol Chem. 1990 Jun 25;265(18):10771-9.
The low density lipoprotein receptor-related protein (LRP) from rat liver membranes binds apoprotein E (apoE)-enriched rabbit beta-migrating very low density lipoproteins (beta-VLDL) in a ligand blotting assay on nitrocellulose membranes. Binding was markedly activated when the beta-VLDL was preincubated with recombinant human apoE-3, native human apoE-3 or E-4, or native rabbit apoE. Human apoE-2, which binds poorly (1-2% of apo E-3 binding) to low density lipoprotein receptors, was approximately 40% as effective as apoE-3 or apoE-4 in binding to LRP. Stimulation of apoE-dependent binding to LRP was blocked by the inclusion of a mixture of human apoC proteins, but not apoA-I or A-II, in the preincubation reaction. High concentrations of apoE did not overcome the apoC inhibition. The effects of apoE and apoC on the ligand blotting assay were paralleled by similar effects in the ability of beta-VLDL to stimulate cholesteryl ester synthesis in mutant human fibroblasts that lack low density lipoprotein receptors. These properties of LRP are consistent with the known effects of apoE and apoC on uptake of chylomicron and very low density lipoprotein remnants in the liver and raise the possibility that LRP functions as a receptor for apoE-enriched forms of these lipoproteins in intact animals.
在硝酸纤维素膜上进行的配体印迹分析中，大鼠肝细胞膜上的低密度脂蛋白受体相关蛋白（LRP）能结合富含载脂蛋白E（apoE）的兔β迁移极低密度脂蛋白（β-VLDL）。当β-VLDL与重组人apoE-3、天然人apoE-3或E-4或天然兔apoE预孵育时，结合显著增强。人apoE-2与低密度脂蛋白受体的结合能力较差（仅为apoE-3结合能力的1-2%），但其与LRP结合的效力约为apoE-3或apoE-4的40%。在预孵育反应中加入人载脂蛋白C蛋白混合物可阻断apoE依赖的与LRP的结合，但加入apoA-I或A-II则无此作用。高浓度的apoE不能克服apoC的抑制作用。apoE和apoC对配体印迹分析的影响，在β-VLDL刺激缺乏低密度脂蛋白受体的突变型人成纤维细胞中胆固醇酯合成的能力方面也有类似表现。LRP的这些特性与apoE和apoC对肝脏中乳糜微粒和极低密度脂蛋白残粒摄取的已知作用一致，并增加了LRP在完整动物中作为这些富含apoE的脂蛋白受体发挥作用的可能性。
