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Fibroblast growth factor receptor-1 regulation of Src family kinases
E Landgren1, P Blume-Jensen, S A Courtneidge
1Ludwig Institute for Cancer Research, Uppsala Branch, Sweden.
Abstract:
Fibroblast growth factors (FGFs) induce proliferation and differentiation of a wide variety of cells by stimulation of cell surface expressed high affinity-binding receptor tyrosine kinases. Members of the Src family of cytoplasmic tyrosine kinases are substrates for certain growth factor receptors. We have examined interactions between FGF receptor-1 (FGFR-1) and Src, Fyn and Yes. In lung capillary endothelial cells and murine fibroblasts, bFGF stimulation led to increased autophosphorylation of Src family members. In contrast, in porcine aortic endothelial cells (FGFR-1/PAE) and lung fibroblasts from chinese hamster (CCL 39), activation of FGFR caused reduced autophosphorylation of Src and Fyn. In neither case could complex-formation between Src members and FGFR be seen. Analysis of a panel of mutated FGFR-1 expressed in PAE cells showed that FGFR-1/Y766F mediated an increased autophosphorylation of Src members and upregulation of their kinase activities. Y766 in FGFR-1 has been shown to serve as a binding site for phospholipase C-gamma, which regulates Ca2+ fluxes and protein kinase C (PKC) activity. The negative effect on Src kinase activity upon FGFR stimulation was mimicked by activation of PKC in FGFR-1/PAE or CCL 39 cells using phorbol 12-myristate 13-acetate (PMA) and Src was phosphorylated in vitro by purified recombinant PKC alpha. Moreover, inhibition of PKC attenuated the bFGF induced decrease in autophosphorylation of Src family members. These data indicate a negative regulatory role for PKC on Src kinase activity in certain cell types.
Insights
Fibroblast growth factors (FGFs) impact Src family kinases differently based on cell type. Protein kinase C (PKC) activation by FGF receptor-1 (FGFR-1) can negatively regulate Src kinase activity.
Area of Science:
- Cellular signaling pathways
- Receptor tyrosine kinases
- Protein kinase regulation
Background:
- Fibroblast growth factors (FGFs) bind to receptor tyrosine kinases (RTKs) like FGFR-1, initiating cellular responses.
- Src family kinases are cytoplasmic tyrosine kinases known to interact with growth factor receptors.
Purpose of the Study:
- To investigate the interaction between Fibroblast Growth Factor Receptor-1 (FGFR-1) and Src family kinases (Src, Fyn, Yes).
- To elucidate the role of specific FGFR-1 residues and downstream signaling pathways in modulating Src kinase activity.
Main Methods:
- Stimulation of various cell types with bFGF and analysis of Src family member autophosphorylation.
- Expression of mutated FGFR-1 in PAE cells to assess the impact of specific tyrosine residues.
- Investigating the role of Protein Kinase C (PKC) activation and inhibition on Src kinase activity.
Main Results:
- FGFR-1 stimulation differentially affected Src family member autophosphorylation across cell types, with some showing increases and others decreases.
- A mutation at Y766 in FGFR-1 (FGFR-1/Y766F) led to increased Src autophosphorylation and kinase activity.
- Activation of PKC mimicked the negative effect of FGFR stimulation on Src activity, and PKC inhibition attenuated bFGF-induced decreases in Src autophosphorylation.
Conclusions:
- FGFR-1 signaling can lead to both positive and negative regulation of Src family kinases depending on the cellular context.
- The Y766 residue in FGFR-1 plays a critical role in mediating the effects of FGFR activation on Src kinase activity, likely through PKC-dependent pathways.
- Protein Kinase C (PKC) acts as a negative regulator of Src kinase activity in certain cell types upon FGFR stimulation.