Phosphorylation of phospholipase C gamma 1 and its association with the FGF receptor is developmentally regulated and occurs during mesoderm induction in Xenopus laevis.
We have examined phosphorylation of phospholipase C gamma 1 (PLC gamma 1) and its association with FGFR1 during mesoderm induction in animal pole explants and during early development in Xenopus embryos. In explants, PLC gamma 1 became associated with FGFR1 during mesoderm induction by FGF or by vegetal cells, the source of the natural inducer. Both PLC gamma 1 and FGFR1 were phosphorylated on tyrosine, indicating that both proteins were activated. Phosphorylation of these two proteins occurred very early during the induction process (within 0.5 hr), providing evidence that a member of the FGF family is a component of the vegetal inducing signal. PLC gamma 1 was also associated with FGFR1 in Xenopus blastulae and this association was specific to presumptive mesoderm cells. Examination of the PLC gamma 1 phosphorylation pattern during early Xenopus development and its association with FGFR1 revealed that maximum phosphorylation and association of these two proteins occurred during early- to mid-blastula stages, concurrent with mesoderm induction in vivo. This spatiotemporal pattern PLC gamma 1-FGFR1 association and phosphorylation suggests that PLC gamma 1 is involved in intracellular signaling during mesoderm induction in Xenopus. Seven additional phosphotyrosyl bands were coimmunoprecipitated with either PLC gamma 1 or FGFR1 from Xenopus blastulae; these bands may represent additional components of an FGFR1 signaling complex. One of these phosphotyrosyl bands was identified as NCK. In addition, growth factor receptor-binding protein, and son-of-sevenless two upstream regulators of RAS signaling, were co-immunoprecipitated with FGFR1.
Terry Fox Cancer Research Laboratories, Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada.
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Gillespie
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001755:Blastocyst / Q000502:physiology*; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004625:Embryo, Nonmammalian / Q000378:metabolism / Q000502:physiology*; D005314:Embryonic and Fetal Development; D051380:GRB2 Adaptor Protein; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology*; D008970:Molecular Weight; D009924:Organ Culture Techniques; D010766:Phosphorylation; D011485:Protein Binding; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000302:isolation & purification / Q000378:metabolism*; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000302:isolation & purification / Q000378:metabolism*; D014982:Xenopus laevis
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; D007527:Isoenzymes; D011506:Proteins; D017468:Receptors, Fibroblast Growth Factor; D010738:Type C Phospholipases