A hepatocyte receptor for high-density lipoproteins specific for apolipoprotein A-I.
Apolipoprotein (apo) E-deficient rat high-density lipoproteins (HDL) bind to isolated rat hepatocytes at 4 degrees C by a process shown to be saturable and competed for by an excess of unlabeled HDL. Uptake (binding and internalization) at 37 degrees C was also saturable and competed for by an excess of unlabeled HDL. At 37 degrees C the HDL apoprotein was degraded as evidenced by the appearance of trichloroacetic acid-soluble radioactivity in the incubation media. The binding of a constant amount of 125I-apo-E-deficient HDL was measured in the presence of increasing concentrations of various lipoproteins. HDL and dimyristoyl phosphatidylcholine (DMPC) X apo-A-I complexes decreased binding by 80 and 65%, respectively. Human low-density lipoproteins, DMPC X apo-E complexes, and DMPC vesicles alone did not compete for apo-E-deficient HDL binding. However, DMPC X apo-E complexes did compete for the binding of the total HDL fraction that contained apo-E but to a lesser extent than did DMPC X apo-A-I. DMPC X 125I-apo-A-I complexes also bound to hepatocytes, and this binding was competed for by excess HDL (70%) and DMPC X apo-A-I complexes (65%), but there was no competition for binding by DMPC vesicles or DMPC X apo-E complexes. It thus appears that hepatocytes have a specific receptor for HDL and that apo-A-I is the ligand for this receptor.
D000818:Animals; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000378:metabolism*; D002352:Carrier Proteins; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008075:Lipoproteins, HDL; D008099:Liver / Q000378:metabolism*; D008297:Male; D008985:Monensin / Q000494:pharmacology; D016601:RNA-Binding Proteins; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018110:Receptors, Lipoprotein; D013379:Substrate Specificity; D013997:Time Factors
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D002352:Carrier Proteins; D008075:Lipoproteins, HDL; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface; D018110:Receptors, Lipoprotein; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein; D008985:Monensin; D004134:Dimyristoylphosphatidylcholine