Isolation and characterization of the apolipoprotein E receptor from canine and human liver

J Biol Chem. 1986 Mar 25;261(9):4256-67.

Abstract

Previous results have demonstrated that liver membranes possess two distinct lipoprotein receptors: a low density lipoprotein (LDL) receptor that binds lipoproteins containing either apolipoprotein (apo-) B or apo-E, and an apo-E-specific receptor that binds apo-E-containing lipoproteins, but not the apo-B-containing LDL. This study reports the isolation and purification of apo-B,E(LDL) and apo-E receptors from canine and human liver membranes. The receptors were solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate and were partially purified by DEAE-cellulose chromatography. The apo-B,E(LDL) receptor was isolated by affinity chromatography on LDL-Sepharose. The apo-E receptor, which did not bind to the LDL-Sepharose column, was then purified by using an HDLc (cholesterol-induced high density lipoprotein)-Sepharose affinity column and an immunoaffinity column. Characterization of the receptors revealed that the hepatic apo-B,E(LDL) receptor is similar to the extrahepatic LDL receptor with an apparent Mr = 130,000 on non-reducing sodium dodecyl sulfate-polyacrylamide gels. The apo-E receptor was found to be distinct from the apo-B,E(LDL) receptor, with an apparent Mr = 56,000. The purified apo-E receptor displayed Ca2+-dependent binding to apo-E-containing lipoproteins and did not bind to LDL or chemically modified apo-E HDLc. Antibodies raised against the apo-B,E(LDL) receptor cross-reacted with the apo-E receptor. However, an antibody prepared against the apo-E receptor did not react with the apo-B,E(LDL) receptor. The apo-E receptor also differed from the apo-B,E(LDL) receptor in amino acid composition, indicating that the apo-E receptor and the apo-B,E(LDL) receptor are two distinct proteins. Immunoblot characterization with anti-apo-E receptor immunoglobulin G indicated that the apo-E receptor is present in the hepatic membranes of man, dogs, rats, and mice and is localized to the rat liver parenchymal cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Animals
  • Apolipoproteins B / metabolism
  • Apolipoproteins E / metabolism
  • Binding, Competitive
  • Cattle
  • Chromatography, Affinity
  • Chromatography, DEAE-Cellulose
  • DNA / analysis
  • Dogs
  • Humans
  • Immunosorbent Techniques
  • Lipoproteins, HDL / metabolism
  • Lipoproteins, LDL / metabolism
  • Liver / analysis*
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Molecular Weight
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / isolation & purification*
  • Receptors, LDL / analysis

Substances

  • Amino Acids
  • Apolipoproteins B
  • Apolipoproteins E
  • Lipoproteins, HDL
  • Lipoproteins, LDL
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Receptors, Cell Surface
  • Receptors, LDL
  • DNA