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 receptors (FGFRs) in mediating uPA up-regulation in these cells. The results show that FGF-2 antagonists suramin, protamine, heparin, the synthetic peptide FGF-2(112-155), and a soluble form of FGFR-1 do not inhibit FGF-2-mediated uPA up-regulation at concentrations that affect growth factor binding to cell surface receptors and mitogenic activity. In contrast, tyrosine phosphorylation inhibitors and overexpression of a dominant negative TK- mutant of FGFR-1 abolish the uPA-inducing activity of FGF-2, indicating that FGFR and its TK activity are essential in mediating uPA induction. Accordingly, FGF-2 induces uPA up-regulation in Chinese hamster ovary cells transfected with wild-type FGFR-1, -2, -3, or -4 but not with TK- FGFR-1 mutant. Small unilamellar phosphatidyl choline:cholesterol vesicles loaded with FGF-2 increased uPA production in GM 7373 cells in the absence of a mitogenic response. Liposome-encapsulated FGF-2 showed a limited but significant capacity, relative to free FGF-2, to interact with FGFR both at 4 degrees C and 37 degrees C and to be internalized within the cell. uPA up-regulation by liposome-encapsulated FGF-2 was quenched by neutralizing anti-FGF-2 antibodies, indicating that the activity of liposome-delivered FGF-2 is mediated by an extracellular action of the growth factor. Taken together, 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 growth factor.
Rusnati
M
M
Department of Biomedical Sciences and Biotechnology, University of Brescia, Italy.
Dell'Era
P
P
Urbinati
C
C
Tanghetti
E
E
Massardi
M L
ML
Nagamine
Y
Y
Monti
E
E
Presta
M
M
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000196:embryology; D016466:CHO Cells; D002417:Cattle; D002460:Cell Line; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology; D016222:Fibroblast Growth Factor 2 / Q000819:agonists / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008934:Mitogens; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism*; D015854:Up-Regulation; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D008081:Liposomes; D008934:Mitogens; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; D011505:Protein-Tyrosine Kinases; D014568:Urokinase-Type Plasminogen Activator