Identification of Autophosphorylation Sites within Fibroblast Growth Factor (FGF) Receptor-1 Implicated in FGF-mediated Upregulation of Urokinase-Type Plasminogen Activator (uPA)

Dissociation of uPA induction from mitogenic signalling

    Patrizia Dell'Era§, Moosa Mohammadi^, and Marco Presta§
§Unit of General Pathology and Immunology, Department of Biomedical Sciences and Biotechnology, School of Medicine, University of Brescia, 25123 Brescia, Italy and ^Department of Pharmacology, New York University Medical Center, New York, New York, 10016, USA.


 
 
 

  3D structure of the Tyrosine-Kinase domain of FGFR-1 
(330 Kb, it may take few minutes to download) 
 
<font size=-1>3D structure of TK-FGFR1 
 

If the plug-in named ChemScape Chime is properly installed on your computer, you should see two FGFR1 molecules (their intracellular TK domain). The molecules can be moved by clicking them with the left button of your mouse and their characteristics, including automatic rotation, can be modified by clicking them with the right button. 

To download the plug-in: . 


 
 
 
 

3D structure of the intracellular TK domain of FGFR-1 dimer 


 

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 ABSTRACT

Among the seven tyrosine autophosphorylation sites identified in the intracellular domain of tyrosine kinase fibroblast growth factor receptor-1 (TK-FGFR1), five of them are dispensable for FGFR1-mediated mitogenic signaling (Mohammadi et al., 1996a, Mol. Cell. Biol. 16, 977-989). 

The possibility to dissociate the mitogenic activity of basic FGF (FGF2) from its urokinase-type plasminogen activator (uPA) inducing capacity both at pharmacological and structural levels (Rusnati et al., 1996, Mol. Biol. Cell 7, 369-381) prompted us to evaluate the role of these autophosphorylation sites in transducing FGF2-mediated uPA upregulation. 

To this purpose, L6 myoblasts transfected with either wild type (wt) or various FGFR1 mutants were evaluated for the capacity to upregulate uPA production by FGF2. 

uPA was induced in cells transfected with wt-FGFR1, FGFR1-Y463F, -Y585F, -Y730F, -Y766F, or -Y583/585F mutants. In contrast, uPA upregulation was prevented in L6 cells transfected with FGFR1-Y463/583/585/730F mutant (FGFR1-4F) or with FGFR1-Y463/583/585/730/766F mutant (FGFR1-5F) that retained instead a full mitogenic response to FGF2. However, preservation of residue Y730 in FGFR1-Y463/583/585F mutant (FGFR1-3F) and FGFR1-Y463/583/585/766F mutant (FGFR1-4Fbis) allows the receptor to transduce uPA upregulation. 

Wild type FGFR1, FGFR1-3F, and FGFR1-4F similarly bind to a 90 kDa tyrosine phosphorylated protein and activate Shc, ERK2, and JunD following stimulation with FGF2. 

These data, together with the capacity of the MEK1 inhibitor PD 098059  to prevent ERK2 activation and uPA upregulation in wt-FGFR1 cells, suggest that signaling through the Ras/Raf-1/MEK/ERK/JunD pathway is necessary but not sufficient for uPA induction in L6 transfectants. Accordingly, FGF2 was able to stimulate ERK1/2 phosphorylation and cell proliferation, but not uPA upregulation, in L6 cells transfected with the FGFR1-Y463/730F mutant, whereas the FGFR1-Y583/585/730F mutant was fully active. 

We conclude that different tyrosine autophosphorylation requirements in FGFR1 mediate cell proliferation and uPA upregulation induced by FGF2 in L6 cells. In particular, phosphorylation of either Y463 or Y730, dispensable for mitogenic signaling, represents an absolute requirement for FGF2-mediated uPA induction. 

Mol. Biol. Cell, 1999 Jan;10(1):23-33.


AIRC: Special Project Angiogenesis