α(V)β₃ integrin mediates the cell-adhesive capacity and biological activity of basic fibroblast growth factor (FGF-2) in cultured endothelial cells

Fibroblast growth factor-2 (FGF-2) immobilized on non-tissue culture plastic promotes adhesion and spreading of bovine and human endothelial cells that are inhibited by anti-FGF-2 antibody. Heat-inactivated FGF-2 retains its cell-adhesive activity despite its incapacity to bind to tyrosine-kinase FGF receptors or to cell-surface heparan sulfate proteoglycans. Recombinant glutathione-S-transferase-FGF-2 chimeras and synthetic FGF-2 fragments identify two cell-adhesive domains in FGF-2 corresponding to amino acid sequences 38-61 and 82-101. Both regions are distinct from the FGF-receptor- binding domain of FGF-2 and contain a DGR sequence that is the inverse of the RGD cell-recognition sequence. Calcium deprivation, RGD-containing eptapeptides, soluble vitronectin (VN), but not fibronectin (FN), inhibit cell adhesion to FGF-2. Conversely, soluble FGF-2 prevents cell adhesion to VN but not FN, thus implicating VN receptor in the cell-adhesive activity of FGF-2. Accordingly, monoclonal and polyclonal anti-α(v)β₃ antibodies prevent cell adhesion to FGF-2. Also, purified human α(v)β₃ binds to immobilized FGF-2 in a cation-dependent manner, and this interaction is competed by soluble VN but not by soluble FN. Finally, anti-α(v)β₃ monoclonal and polyclonal antibodies specifically inhibit mitogenesis and urokinase-type plasminogen activator (uPA) up-regulation induced by free FGF- 2 in endothelial cells adherent to tissue culture plastic. These data demonstrate that FGF-2 interacts with α(v)β₃ integrin and that this interaction mediates the capacity of the angiogenic growth factor to induce cell adhesion, mitogenesis, and uPA up-regulation in endothelial cells.