Alternatively spliced FGFR-1 isoforms differentially modulate endothelial cell activation of c-YES.
Ligand activation of fibroblast growth factor receptor-1 (FGFR-1) induces an angiogenic response following activation of multiple intracellular signaling substrates, including the Src family of nonreceptor tyrosine kinases (SFK). However, the direct association between FGFR-1 and SFK and the involvement of SFK in FGFR-1-dependent cell proliferation have been controversial. Structural variants of FGFR-1 are generated by alternative splicing which results in two major isoforms, containing either three (FGFR-1alpha) or two (FGFR-1beta) immunoglobulin-like domains in the extracellular region. To determine whether alternatively spliced FGFR-1 isoforms differentially activate SFK, we have examined FGF receptor-negative endothelial cells stably transfected with human cDNA encoding either FGFR-1alpha or FGFR-1beta. Transient activation of c-YES, the predominant SFK expressed in these endothelial cells, was restricted to FGFR-1beta transfectants following exposure to acidic fibroblast growth factor (FGF-1). Co-immunoprecipitation studies revealed that c-YES directly associated with FGFR-1beta. The Src homology (SH)2 domain (and not the SH3 domain) of c-YES was able to recognize tyrosine phosphorylated FGFR-1beta. FGFR-1beta-specific activation of c-YES was accompanied by its association with and activation of cortactin. FGF-1 treatment of both FGFR-1alpha and FGFR-1beta transfectants induced SFK-independent cellular proliferation and growth in low density cultures. At high density, under both anchorage-dependent and -independent conditions, FGF-1 failed to induce proliferation and growth of FGFR-1alpha transfectants. In contrast, FGF-1 induced proliferation, growth, and formation of cord-like structures in high density cultures of FGFR-1beta transfectants in an SFK-dependent manner. In vitro cord formation on Matrigel was restricted to FGFR-1beta transfectants in an SFK-dependent manner. Formation of vascular structures in vivo was limited to endothelial cells transfected with FGFR-1beta. Collectively, these results emphasize the roles of alternatively spliced FGFR-1 structural isoforms and activation of SFK as modulators of endothelial cell growth during the formation of neovascular structures.
Zhang
Pei
P
Department of Surgery and Biochemistry, The University of Alabama at Birmingham, 35294, USA.
Greendorfer
Jessica S
JS
Jiao
Jing
J
Kelpke
Stacey C
SC
Thompson
John A
JA
D017398:Alternative Splicing / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051575:Proto-Oncogene Proteins c-yes / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D018909:src Homology Domains / Q000502:physiology
D020033:Protein Isoforms; D016220:Fibroblast Growth Factor 1; C496348:FGFR1 protein, human; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051575:Proto-Oncogene Proteins c-yes