Chylomicron remnant metabolism. Role of hepatic lipoprotein receptors in mediating uptake

Arteriosclerosis. Jan-Feb 1989;9(1 Suppl):I14-8.

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)

MeSH terms

  • Animals
  • Apolipoproteins E / metabolism
  • Blotting, Western
  • Chylomicrons / metabolism*
  • Dogs
  • Endocytosis
  • Ligands
  • Liver / metabolism*
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Molecular Weight
  • Proton-Translocating ATPases / metabolism
  • Receptors, Cell Surface / isolation & purification
  • Receptors, Cell Surface / metabolism*

Substances

  • Apolipoproteins E
  • Chylomicrons
  • Ligands
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Receptors, Cell Surface
  • Proton-Translocating ATPases