Glypican-1 Is a VEGF165 Binding Proteoglycan That Acts as an Extracellular Chaperone for VEGF165*
- From the ‡Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel, the §Center for Human Genetics, University of Leuven and Flanders Interuniversity, Institute for Biotechnology, Campus Gasthuisberg O & N6, Herestraat, B-3000 Leuven, Belgium, and the ¶ImClone Systems Inc., New York, New York 10014
Abstract
Glypican-1 is a member of a family of glycosylphosphatidylinositol anchored cell surface heparan sulfate proteoglycans implicated in the control of cellular growth and differentiation. The 165-amino acid form of vascular endothelial growth factor (VEGF165) is a mitogen for endothelial cells and a potent angiogenic factor in vivo. Heparin binds to VEGF165 and enhances its binding to VEGF receptors. However, native HSPGs that bind VEGF165 and modulate its receptor binding have not been identified. Among the glypicans, glypican-1 is the only member that is expressed in the vascular system. We have therefore examined whether glypican-1 can interact with VEGF165. Glypican-1 from rat myoblasts binds specifically to VEGF165 but not to VEGF121. The binding has an apparent dissociation constant of 3 × 10−10 m. The binding of glypican-1 to VEGF165 is mediated by the heparan sulfate chains of glypican-1, because heparinase treatment abolishes this interaction. Only an excess of heparin or heparan sulfates but not other types of glycosaminoglycans inhibited this interaction. VEGF165 interacts specifically not only with rat myoblast glypican-1 but also with human endothelial cell-derived glypican-1. The binding of125I-VEGF165 to heparinase-treated human vascular endothelial cells is reduced following heparinase treatment, and addition of glypican-1 restores the binding. Glypican-1 also potentiates the binding of 125I-VEGF165 to a soluble extracellular domain of the VEGF receptor KDR/flk-1. Furthermore, we show that glypican-1 acts as an extracellular chaperone that can restore the receptor binding ability of VEGF165, which has been damaged by oxidation. Taken together, these results suggest that glypican-1 may play an important role in the control of angiogenesis by regulating the activity of VEGF165, a regulation that may be critical under conditions such as wound repair, in which oxidizing agents that can impair the activity of VEGF are produced, and in situations were the concentrations of active VEGF are limiting.
Footnotes
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↵* This work was supported by an angiogenesis research center grant from the Israel Science Foundation (to G. N. and D. R.), by a grant from the German Israeli Binational Foundation (to G. N.), and by a grant from the German Foundation for Biotechnological Research (to D. R.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‖ To whom correspondence should be addressed. Tel.: 972-4-8294217; Fax: 972-4-8225-153; E-mail:dinar{at}techunix.technion.ac.il.
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↵2 D. Ron, unpublished results.
- Abbreviations:
- HSPG
-
heparan sulfate proteoglycan
- BSA
-
bovine serum albumin
- FGF
-
fibroblast growth factor
- FGF-1
-
acidic fibroblast growth factor
- FGF-2
-
basic fibroblast growth factor
- FGF-7
-
keratinocyte growth factor
- GAGs
-
glycosaminoglycans
- HS
-
heparan sulfate
- PBS
-
Dulbecco’s phosphate-buffered saline
- VEGF
-
vascular endothelial growth factor
- ELISA
-
enzyme-linked immunosorbent assay
- HUVEC
-
human umbilical vein endothelial cell
- PF4
-
platelet factor 4
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- Received March 2, 1998.
- Revision received January 8, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
