Binding of chylomicron remnants and beta-very low density lipoproteins to hepatic and extrahepatic lipoprotein receptors. A process independent of apolipoprotein B48.
The ability of apolipoprotein (apo-) B48 to interact with lipoprotein receptors was investigated using three different types of lipoproteins. First, canine chylomicron remnants, which contained apo-B48 as their primary apoprotein constituent, were generated by the hydrolysis of chylomicrons with milk lipoprotein lipase. These apo-B48-containing chylomicron remnants are deficient in apo-E and reacted very poorly with apo-E receptors on adult dog liver membranes and the low density lipoprotein (apo-B,E) receptors on human fibroblasts. Addition of normal human apo-E3 restored the receptor binding activity of these lipoproteins. Second, beta-very low density lipoproteins (beta-VLDL) from cholesterol-fed dogs were subfractionated into distinct classes containing apo-E along with either apo-B48 or apo-B100. Both classes bound to the apo-B,E and apo-E receptors. Their binding was almost completely mediated by apo-E, as evidenced by the ability of the anti-apo-E to inhibit the receptor interaction. Third, beta-VLDL from type III hyperlipoproteinemic patients were subfractionated by immunoaffinity chromatography into lipoproteins containing apo-E plus either apo-B48 or apo-B100. Both subfractions bound poorly to apo-B,E and apo-E receptors due to the presence of defective apo-E2. However, the residual binding of the apo-B48-containing and apo-B100-containing human beta-VLDL was inhibited by the anti-apo-E. After lipase hydrolysis, apo-B100 became a more prominant determinant responsible for mediating receptor binding to the apo-B,E receptor. By contrast, lipase hydrolysis did not increase the binding activity of the apo-B48-containing beta-VLDL. These results indicate that apo-B48 does not play a direct role in mediating the interaction of lipoproteins with receptors on fibroblasts or liver membranes.
D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001057:Apolipoproteins E / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002914:Chylomicrons / Q000378:metabolism*; D004285:Dogs; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007223:Infant; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008196:Lymph; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism*; D018110:Receptors, Lipoprotein
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D001057:Apolipoproteins E; D002914:Chylomicrons; D008079:Lipoproteins, VLDL; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; C036053:VLDL receptor; C028203:chylomicron receptor; D008071:Lipoprotein Lipase