Fibroblast growth factor receptor-1 mediates chemotaxis independently of direct SH2-domain protein binding

Abstract

Endothelial cells expressing ®broblast growth factor receptor-1 (FGFR-1) migrate and proliferate in response to treatment with FGF. We analysed ligand-induced migration and proliferation of porcine aortic endothelial cells expressing wild-type FGFR-1, point-mutated Y766F FGFR-1, unable to activate phospholipase C-g1 (PLCg1), or carboxyl-terminally truncated FGFR-1, lacking either 48 (from amino acid 774 in the FGFR-1 sequence) or 63 (from amino acid 759) amino acid residues of the C-terminal tail. The truncated CT63 FGFR-1 mutant failed to mediate chemotaxis, but was in response to ligand stimulation capable of mediating proliferation of the cells, stimulation of MAP kinase activity and tyrosine phosphorylation of FRS2, an FGFR-1 speci®c signaling molecule. The defect in migration-capacity of CT63 was not due to loss of Y766, and thereby PLC-g1 activation, since cells expressing the mutant Y766F FGFR-1 migrated as e ciently as the wild-type receptor cells. Induction of phospholipase A 2 (PLA 2 ) activity by the activated FGFR-1 was dependent on the presence of Y766, and was therefore also not critical for the chemotactic response. Although the FGFR-1 only very ine ciently mediates activation of phosphatidylinositol 3' kinase (PI 3-kinase), the PI 3-kinase inhibitor wortmannin suppressed wild-type FGFR-1 mediated migration. We conclude that the signal transduction pathway for FGFR-1 mediated migration is independent of phosphotyrosine residues in the receptor and requires activation of a wortmannin-sensitive enzyme.

Suppression of autocrine cell proliferation and tumorigenesis of human melanoma cells and fibroblast growth factor transformed fibroblasts by a kinase-deficient FGF receptor 1: evidence for the involvement of Src-family kinases

“…As shown in Figure 6a, bFGF or HGF/SF caused a 2.5-fold increase in Src-kinase activity in normal human melanocytes. The magnitude of the change in activity is similar to that observed in Src autophosphorylation in response to bFGF in lung endothelial cells (Landgren et al, 1995), as well as Srcinduced kinase activity by HGF/SF in carcinoma and osteoclastic cells (Grano et al, 1996;Ponzetto et al, 1994). Parallel assays employing member-speci®c antibodies against Src, Fyn or Yes, failed to detect any activity above control antibody (data not shown).…”

“…The observation that the truncated-mutant¯g is more e ective in suppressing tumor growth in nude mice than proliferation in culture, suggests that serum supplemented medium facilitates growth in the absence of receptor activity. (Kremer et al, 1991;Landgren et al, 1995;Zhan et al, 1994), prompted us to assess changes in the activity of this intracellular kinase. Src kinase activity was ®rst measured in resting and bFGF stimulated normal human melanocytes (Figure 6a).…”

Fibroblast growth factor/fibroblast growth factor receptor system in angiogenesis

“…Similar to cell proliferation, the chemotactic effect of FGF2 requires the activation of the MAPK signaling pathway [30] and is abolished by PKC down-regulation [31]. The capacity of FGFR1 to mediate chemotaxis resides in the amino acid stretch 759-773 of its cytoplasmic tail [32]. However, the biological response is independent of tyrosine phosphorylation and requires the activation of a Wortmannin-sensitive pathway [32].…”

“…The capacity of FGFR1 to mediate chemotaxis resides in the amino acid stretch 759-773 of its cytoplasmic tail [32]. However, the biological response is independent of tyrosine phosphorylation and requires the activation of a Wortmannin-sensitive pathway [32]. Expression of a kinase-inactive c-Fes mutant interferes with FGF2-induced chemotaxis in endothelial cells [33].…”

Induction of Mdm2 and enhancement of cell survival by bFGF

“…Identi®ed intermediates include phospholipase C (Mohammadi et al, 1991), ERK1 and ERK2 (Bogoyevitch et al, 1994;Creuzet et al, 1995), cortactin , Src (Landgren et al, 1995;, Shc and a 90 kDa protein identi®ed as 80K-H (Klint et al, 1995;Goh et al, 1996).…”