Interaction of lipoprotein Lp[a] with the B/E-receptor: a study using isolated bovine adrenal cortex and human fibroblast receptors.
The ability of different lipoprotein Lp[a] preparations to compete with LDL-binding to the B/E-receptor was investigated by ligand blot and filter assays. Lp[a] was purified from donors with various genetic polymorphic forms by affinity chromatography using lysine-Sepharose or specific immunoadsorbers. These preparations were free of "LDL-like" material. Part of Lp[a] was reduced and freed from specific apo[a] antigen yielding "Lpa-." 125I-labeled low density lipoproteins (LDL) were incubated with B/E-receptor preparations from bovine adrenal cortex or from human skin fibroblasts, and the competition with unlabeled LDL, Lp[a], Lpa-, apo[a], and apoE-free HDL was studied by a ligand blot or filter assay technique. The following results were obtained. 1) LDL and Lpa- were equally potent in displacing 125I-labeled from B/E-receptor in the ligand blot and the filter assay. Lpa + ( = Lp[a]) also displaced LDL but to a much lesser degree: 50% displacement was observed with LDL and Lpa- at a 1-fold excess, whereas a 7.5-fold excess was required of Lpa +. 2) Apo[a], as well as apoE-free HDL, did not compete with LDL binding. 3) Competition experiments using B/E-receptors from bovine adrenal cortex or from human skin fibroblasts were comparable. 4) There was no difference in the behavior of Lp[a] isolated from the two affinity chromatography methods. 5) Lp[a] of different genetic variants behaved virtually identically. The results are discussed from the point of view of the in vivo metabolism of Lp[a].
Steyrer
E
E
Institute of Medical Biochemisty, University of Graz, Austria.
Kostner
G M
GM
D000302:Adrenal Cortex / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D015153:Blotting, Western; D002417:Cattle; D002846:Chromatography, Affinity; D005347:Fibroblasts; D006801:Humans; D008024:Ligands; D017270:Lipoprotein(a); D008074:Lipoproteins / Q000302:isolation & purification / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D011973:Receptors, LDL / Q000378:metabolism*
D008024:Ligands; D017270:Lipoprotein(a); D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D011973:Receptors, LDL