title: Chylomicron remnant metabolism. Role of hepatic lipoprotein receptors in mediating uptake.
abstract: Chylomicron remnants are catabolized by the liver, and their uptake within this organ is mediated by the presence of apolipoprotein (apo) E on the surface of these particles. In addition to a receptor for low density lipoproteins (LDL), several lines of evidence suggest that a unique receptor, referred to as the chylomicron remnant or apo E receptor, may be involved in the uptake of these lipoproteins. A possible candidate for the apo E receptor was previously isolated by affinity chromatography and was shown to possess high-affinity binding to apo E-containing lipoproteins, including chylomicron remnants, but not to possess high-affinity binding to apo B-containing LDL. However, it is now known that this fraction contains at least three proteins, all of which bind apo E with high affinity. An Mr congruent to 56,000 fraction contains two proteins that have been identified as the alpha- and beta-subunits of mitochondrial F1-adenosine 5'-triphosphatase (F1-ATPase). Furthermore, purified F1-ATPase binds apo E-containing lipoproteins with high affinity. It is very unlikely that these proteins, presumably isolated from mitochondrial membranes, are involved in chylomicron remnant metabolism. An Mr congruent to 59,000 fraction contains a unique apo E-binding protein that is not an ATPase. This protein appears to be localized to the endoplasmic reticulum of liver cells, but it is unclear whether this protein plays a role in chylomicron remnant catabolism. Furthermore, a cDNA clone coding for a protein that is apparently distinct from the ATPase and the Mr congruent to 59,000 protein has been obtained from a lambda gt11 library.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Gladstone Foundation Laboratories for Cardiovascular Disease, University of California, San Francisco 94140.
authors.forename: R W
authors.initials: RW
authors.lastname: Mahley
authors.forename: D Y
authors.initials: DY
authors.lastname: Hui
authors.forename: T L
authors.initials: TL
authors.lastname: Innerarity
authors.forename: U
authors.initials: U
authors.lastname: Beisiegel
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000378:metabolism; D015153:Blotting, Western; D002914:Chylomicrons / Q000378:metabolism*; D004285:Dogs; D004705:Endocytosis; D008024:Ligands; D008099:Liver / Q000378:metabolism*; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008970:Molecular Weight; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D002914:Chylomicrons; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011956:Receptors, Cell Surface; D006180:Proton-Translocating ATPases