Thrombospondin-1 (TSP) inhibits the angiogenic activity of basic fibroblast growth factor (bFGF). Here we address the hypothesis of a direct interaction between TSP and bFGF. Gel permeation chromatography and cross- linking experiments demonstrated that bFGF binds to TSP in solution. bFGF also bound to immobilized TSP in a solid-phase assay. Binding was dose- dependent, with a K(d) in the nanomolar range, and was inhibited by anti-TSP antibodies. The 140-kDa carboxyl-terminal fragment of TSP, but not the 25- kDa heparin-binding fragment, fully retained the bFGF binding capacity. Accordingly, binding was inhibited by monoclonal antibodies directed against this fragment. Heparin completely blocked bFGF binding to TSP and to the 140- kDa fragment. TSP and its 140-kDa fragment inhibited the binding of bFGF to endothelial cells at concentrations (≤ 100 nM) that inhibited endothelial cell proliferation but not motility. Low-affinity binding was inhibited more than high-affinity binding (up to 76 and 41% inhibition, respectively), and the inhibition was reversed by anti-TSP antibodies. Vitronectin and transforming growth factor β, potentially associated with TSP, did not affect bFGF binding to endothelial cells. Although TSP did not affect the activation of the high-affinity receptors, it reduced the long-term internalization of bFGF. We conclude that TSP binds to bFGF through a domain within its 140-kDa fragment, a mechanism that might affect bFGF interaction with endothelial cells, activity, and association with the extracellular matrix.
|Number of pages||9|
|Journal||Cell Growth and Differentiation|
|Publication status||Published - Apr 1997|
ASJC Scopus subject areas
- Cell Biology
- Molecular Biology