Syndecan-4 contributes to endothelial tubulogenesis through interactions with two motifs inside the pro-angiogenic N-terminal domain of thrombospondin-1
✍ Scribed by Sara Santana Nunes; Marianna A. Ferrari do Outeiro-Bernstein; Luiz Juliano; Francisco Vardiero; Helena B. Nader; Anne Woods; Chantal Legrand; Verônica Morandi
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 457 KB
- Volume
- 214
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
Thrombospondin‐1 (TSP‐1) is an extracellular matrix protein that modulates focal adhesion in mammalian cells and exhibits dual roles in angiogenesis. In a previous work, we showed that a recombinant 18 kDa protein encompassing the N‐terminal residues 1‐174 of human TSP‐1 (TSP18) induced tubulogenesis of human umbilical vein endothelial cells and protected them from apoptosis. Our results indicated that these effects were possibly mediated by syndecan‐4 proteoglycan, since binding of TSP18 to endothelial extracts was inhibited by anti‐syndecan‐4 antibody. Syndecan‐4 is a heparan‐sulfate proteoglycan that regulates cell–matrix interactions and is the only member of its family present in focal adhesions. In this report, we demonstrate that a monoclonal antibody against syndecan‐4 blocks TSP18‐induced tubulogenesis. Furthermore, through 2D adhesion and 3D angiogenic assays, we demonstrate that two sequences, TSP Hep I and II, retain the major pro‐angiogenic activity of TSP18. These TSP‐1 motifs also compete with the fibronectin Hep II domain for binding to syndecan‐4 on endothelial cell surface, indicating that they may exert their effects by interfering with the recognition of fibronectin by syndecan‐4. Additionally, TSP18 and its derived peptides activate the PKC‐dependent Akt‐PKB signaling pathway. Blockage of PKC activation prevented HUVEC spreading when seeded on TSP18 fragment, and on TSP Hep I and TSP Hep II peptides, but not on gelatin‐coated substrates. Our results identify syndecan‐4 as a novel receptor for the N‐terminus of TSP‐1 and suggest that TSP‐1 N‐terminal pro‐angiogenic activity is linked to its capacity of interfering with syndecan‐4 functions in the course of cell adhesion. J. Cell. Physiol. 214: 828–837, 2008. © 2007 Wiley‐Liss, Inc.