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Low-density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor on murine peritoneal macrophages mediates the binding and catabolism of low-density lipoprotein.

Publication ,  Journal Article
Wu, SM; Pizzo, SV
Published in: Arch Biochem Biophys
February 1, 1996

Low-density lipoprotein receptor-related protein (LRP)/alpha 2-macroglobulin receptor is a member of the low-density lipoprotein receptor family. It is known to bind a wide variety of unrelated ligands including alpha 2-macroglobulin-proteinase complexes, tissue plasminogen activator, apolipoprotein E-enriched very low density lipoprotein, lipoprotein lipase, and Pseudomonas exotoxin A. Receptor-associated protein (RAP), a protein which copurifies with LRP, can inhibit the binding and internalization of all known ligands to LRP. Recent studies have shown that some ligands can bind to more than one receptor in this family. However, the ability of low-density lipoprotein (LDL) to bind to LRP in addition to the LDL receptor has not been demonstrated consistently. In this study we demonstrate that LDL binds with high affinity to macrophage cell surface receptors at 4 degrees C (Kd = 1.8 nM) and competes for the binding of a receptor-recognized form of alpha 2-macroglobulin (alpha 2M*) (Ki = 3 nM). alpha 2M* and RAP can inhibit the binding of LDL to macrophages completely (96 and 100% inhibition, respectively), after cell surface heparin has been removed by treatment with heparinase. Using a solid-phase assay, we show that LDL binds specifically, saturably, and with high affinity to purified LRP (Kd = 5 nM). LDL can also completely inhibit the binding of alpha 2M* to purified LRP. These results indicate that LDL binds directly to LRP. The ability of LDL to cross-compete with alpha 2M* for binding to LRP suggests that LDL binds to a similar or overlapping site as alpha 2M*. In addition, the ability of alpha 2M* to inhibit most of the receptor-mediated binding of LDL to macrophages suggests that LDL receptors on murine peritoneal macrophages are predominantly LRP.

Duke Scholars

Published In

Arch Biochem Biophys

DOI

ISSN

0003-9861

Publication Date

February 1, 1996

Volume

326

Issue

1

Start / End Page

39 / 47

Location

United States

Related Subject Headings

  • Receptors, Immunologic
  • Radioligand Assay
  • Mice, Inbred C57BL
  • Mice
  • Macrophages, Peritoneal
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Lipoproteins, LDL
  • Female
  • Cell Membrane
  • Biochemistry & Molecular Biology
 
Journal cover image

Published In

Arch Biochem Biophys

DOI

ISSN

0003-9861

Publication Date

February 1, 1996

Volume

326

Issue

1

Start / End Page

39 / 47

Location

United States

Related Subject Headings

  • Receptors, Immunologic
  • Radioligand Assay
  • Mice, Inbred C57BL
  • Mice
  • Macrophages, Peritoneal
  • Low Density Lipoprotein Receptor-Related Protein-1
  • Lipoproteins, LDL
  • Female
  • Cell Membrane
  • Biochemistry & Molecular Biology