Obligatory role of cholesterol and apolipoprotein E in the formation of large cholesterol-enriched and receptor-active high density lipoproteins

J Biol Chem. 1985 Oct 5;260(22):11934-43.


The formation of large cholesterol-enriched high density lipoproteins (HDL1/HDLc) from typical HDL3 requires lecithin:cholesterol acyltransferase activity, additional cholesterol, and a source of apolipoprotein (apo-) E. The present study explores the role of apo-E in promoting HDL1/HDLc formation and in imparting to these lipoprotein particles the ability to interact with the apo-B,E(low density lipoprotein (LDL] receptor. Incubation of normal canine serum with cholesterol-loaded mouse peritoneal macrophages resulted in the formation of HDL1/HDLc that competed with 125I-LDL for binding to the apo-B,E(LDL) receptors on cultured human fibroblasts. Cholesterol efflux from macrophages was necessary because incubation of normal canine serum with nonloaded macrophages did not cause HDL1/HDLc formation. However, cholesterol delivery to the serum was not sufficient to result in HDL1/HDLc formation. Apolipoprotein E had to be available. Incubation of apo-E-depleted canine serum with cholesterol-loaded J774 cells, a macrophage cell line that does not synthesize apo-E, demonstrated that no HDL1/HDLc formation was detected even in the presence of significant cholesterol efflux. However, addition of exogenous apo-E to the serum during the incubation with cholesterol-loaded J744 cells promoted the formation of large receptor-active HDL1/HDLc. The receptor binding activity of these particles produced in vitro correlated with the amount of apo-E incorporated into the HDL1/HDLc. Apolipoproteins A-I and C-III were ineffective in promoting HDL1/HDLc formation; thus, apo-E was unique in allowing HDL1/HDLc formation. These results demonstrate that when lecithin:cholesterol acyltransferase activity, cholesterol, and apo-E are present in serum, typical HDL can be transformed in vitro into large cholesterol-rich HDL1/HDLc that are capable of binding to lipoprotein receptors.

MeSH terms

  • Animals
  • Apolipoproteins E / metabolism*
  • Binding, Competitive
  • Carrier Proteins*
  • Cell Line
  • Cells, Cultured
  • Cholesterol / metabolism*
  • Female
  • Kinetics
  • Lipoproteins, HDL / biosynthesis
  • Lipoproteins, HDL / isolation & purification
  • Lipoproteins, HDL / metabolism*
  • Macrophages / metabolism
  • Mice
  • Molecular Weight
  • Protein Conformation
  • RNA-Binding Proteins*
  • Receptors, Cell Surface / metabolism*
  • Receptors, LDL / metabolism
  • Receptors, Lipoprotein*


  • Apolipoproteins E
  • Carrier Proteins
  • Lipoproteins, HDL
  • RNA-Binding Proteins
  • Receptors, Cell Surface
  • Receptors, LDL
  • Receptors, Lipoprotein
  • high density lipoprotein receptors
  • high density lipoprotein binding protein
  • Cholesterol