A DISTINCT BASIC FIBROBLAST GROWTH-FACTOR (FGF-2) FGF RECEPTOR INTERACTION DISTINGUISHES UROKINASE-TYPE PLASMINOGEN-ACTIVATOR INDUCTION FROM MITOGENICITY IN ENDOTHELIAL-CELLS/

Basic fibroblast growth factor (FGF-2) induces cell proliferation and urokinase-type plasminogen activator (uPA) production in fetal bovine aortic endothelial GM 7373 cells. In the present paper we investigated the role of the interaction of FGF-2 with tyrosine-kinase (TK) FGF re ceptors (FGFRs) in mediating uPA up-regulation in these cells. The res ults show that FGF-2 antagonists suramin, protamine, heparin, the synt hetic peptide FGF-2(112-155), and a soluble form of FGFR-1 do not inhi bit FGF-2-mediated uPA up-regulation at concentrations that affect gro wth factor binding to cell surface receptors and mitogenic activity. I n contrast, tyrosine phosphorylation inhibitors and overexpression of a dominant negative TK- mutant of FGFR-1 abolish the uPA-inducing acti vity of FGF-2, indicating that FGFR and its TK activity are essential in mediating uPA induction. Accordingly, FGF-2 induces uPA up-regulati on in Chinese hamster ovary cells transfected with wild-type FGFR-1, - 2, -3, or -4 but not with TK- FGFR-1 mutant. Small unilamellar phospha tidyl choline:cholesterol vesicles loaded with FGF-2 increased uPA pro duction in GM 7373 cells in the absence of a mitogenic response. Lipos ome-encapsulated FGF-2 showed a limited but significant capacity, rela tive to free FGF-2, to interact with FGFR both at 4 degrees C and 37 d egrees C and to be internalized within the cell. uPA up-regulation by liposome-encapsulated FGF-2 was quenched by neutralizing anti-FGF-2 an tibodies, indicating that the activity of liposome-delivered FGF-2 is mediated by an extracellular action of the growth factor. Taken togeth er, the data indicate that a distinct interaction of FGF-2 with FGFR, quantitatively and/or qualitatively different from the one that leads to mitogenicity, is responsible for the uPA-inducing activity of the g rowth factor.