Characterization of the FGF receptor signaling complex in Xenopus laevis during early embryonic development

Ryan, Paula (1999) Characterization of the FGF receptor signaling complex in Xenopus laevis during early embryonic development. Masters thesis, Memorial University of Newfoundland.

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Abstract

A stable complex is formed between the fibroblast growth factor receptor (FGFR) and SH2-containing proteins, during early development in Xenopus laevis. The results presented in this thesis demonstrate that phosphorylation of PLCγ1 and its association with FGFR1 occurs during mesoderm induction in vitro. PLCγ1 is involved in intracellular signaling pathway of FGF during the time mesoderm induction is occurring in the embryo. PLCγ1 is specifically phosphorylated during early- to mid-blastula stages, yet the expression level of PLCγ1 protein is constant throughout these stages of development. It is speculated that PLCγ1 is involved in a negative feedback loop, down-regulating the FGFR. The timing of the in vitro experiments (30-minute treatment of FGF) provides evidence that FGF may be a component of the vegetal inducing signal. There were seven other phosphorylated bands co-immoprecipated with PLCγ1 or FGFR during early embryo development. These substrates were identified as phosphatidylinositol 3-kinase (PI3'K), GTPase-activating protein (Gap), SHP2 phosphatase, Nck and three nck-associated proteins: NAP123, NAP 81 and NAP65. Son of Sevenless (SOS) and growth factor receptor binding protein2 (GRB2) were identified in this complex. Neither SOS nor GRB was phosphorylated. This report provides evidence for the importance of these substrates for FGFR signaling during early embryonic development.

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