Glycoprotein 330/Low Density Lipoprotein Receptor-related Protein-2 Mediates Endocytosis of Low Density Lipoproteins via Interaction with Apolipoprotein B100 (*)
- Steingrimur Stefansson(1),
- David A. Chappell(2),
- Kelley M. Argraves(1),
- Dudley K. Strickland(1) and
- W. Scott Argraves(1)(§)
- From the (1)Biochemistry Department, J. H. Holland Laboratory, American Red Cross, Rockville, Maryland 20855 and the
- (2) Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242
- § To whom correspondence should be addressed: Biochemistry Dept., J. H. Holland Laboratory, American Red Cross, 15601 Crabbs Branch Way, Rockville, MD 20855. Tel.: 301-738-0725; Fax: 301-738-0794; argraves{at}hlsun.red-cross.org
Abstract
The ability of glycoprotein 330/low density lipoprotein receptor-related protein-2 (LRP-2) to function as a lipoprotein receptor
was investigated using cultured mouse F9 teratocarcinoma cells. Treatment with retinoic acid and dibutyryl cyclic AMP, which
induces F9 cells to differentiate into endoderm-like cells, produced a 50-fold increase in the expression of LRP-2. Levels
of the other members of the low density lipoprotein (LDL) receptor (LDLR) family, including LDLR, the very low density lipoprotein
receptor, and LRP-1, were reduced. When LDL catabolism was examined in these cells, it was found that the treated cells endocytosed
and degraded at 10-fold higher levels than untreated cells. The increased LDL uptake coincided with increased LRP-2 activity
of the treated cells, as measured by uptake of both 
I-labeled monoclonal LRP-2 antibody and the LRP-2 ligand prourokinase. The ability of LDL to bind to LRP-2 was demonstrated
by solid-phase binding assays. This binding was inhibitable by LRP-2 antibodies, receptor-associated protein (the antagonist
of ligand binding for all members of the LDLR family), or antibodies to apoB100, the major apolipoprotein component of LDL.
In cell assays, LRP-2 antibodies blocked the elevated 
I-LDL internalization and degradation observed in the retinoic acid/dibutyryl cyclic AMP-treated F9 cells. A low level of
LDL endocytosis existed that was likely mediated by LDLR since it could not be inhibited by LRP-2 antibodies, but was inhibited
by excess LDL, receptor-associated protein, or apoB100 antibody. The results indicate that LRP-2 can function to mediate cellular
endocytosis of LDL, leading to its degradation. LRP-2 represents the second member of the LDLR family identified as functioning
in the catabolism of LDL.
Footnotes
-
↵* This work was supported by National Institutes of Health Grants DK45598 (to W. S. A.), HL49264 (to D. A. C.), and GM42581 and HL50787 (to D. K. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- LDL
-
low density lipoprotein
- LDLR
-
low density lipoprotein receptor
- VLDL
-
very low density lipoprotein
- VLDLR
-
very low density lipoprotein receptor
- LRP-1
-
α2-macroglobulin receptor low density lipoprotein receptor-related protein
- LRP-2
-
glycoprotein 330/low density lipoprotein receptor-related protein-2
- RA
-
retinoic acid
- Bt2cAMP
-
dibutyryl cyclic AMP
- RAP
-
receptor-associated protein
- DMEM
-
Dulbecco's modified Eagle's medium
- BSA
-
bovine serum albumin
- mAb
-
monoclonal antibody.
-
↵2Glycoprotein 330 is synonymous with gp330, brushin, megalin, gp600, and LRP-2.
-
- Received May 10, 1995.
- Revision received June 16, 1995.
- © 1995 by The American Society for Biochemistry and Molecular Biology, Inc.
