Related Experiment Videos
Intracellular signalling pathways involved in mesoderm induction by FGF
L L Gillespie1, G D Paterno, L C Mahadevan
1Terry Fox Cancer Research Laboratories, Faculty of Medicine, Memorial University, St. John's, NF, Canada.
Abstract:
We have examined the possible role of two signal transducing mechanisms, tyrosine phosphorylation and activation of protein kinase C (PKC), during fibroblast growth factor (FGF)-induced mesoderm induction in Xenopus. Tyrosine phosphorylation was examined through the use of a monoclonal anti-phosphotyrosine antibody. This antibody was shown to recognize the FGF receptor crosslinked to radioiodinated FGF. We also studied the response of Xenopus ectodermal explants to sodium orthovanadate, a compound that has been shown to elevate intracellular phosphotyrosine levels. Thirty percent of explants cultured in 100 microM vanadate were induced. In addition, vanadate synergized with FGF to give inductions that were more dorsal in nature than either vanadate or FGF alone. The role of PKC was evaluated by measuring PKC activity during mesoderm induction by FGF and by examining the effect of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) on explants. TPA did not induce mesoderm, however, activation of PKC was detected in FGF-treated explants. Therefore, activation of the PKC pathway alone is not sufficient for mesoderm induction. Simultaneous treatment with TPA and FGF resulted in a significant inhibition of mesoderm induction by FGF, suggesting that activation of PKC could be part of a negative feedback mechanism. In contrast, TPA had no effect on induction by activin A.
Insights
Fibroblast growth factor (FGF) induces mesoderm in Xenopus, involving tyrosine phosphorylation. Protein kinase C (PKC) activation alone is insufficient and may act as a negative feedback mechanism during FGF signaling.
Area of Science:
- Developmental Biology
- Cell Signaling
Background:
- Fibroblast growth factor (FGF) is crucial for mesoderm induction in Xenopus embryos.
- Signal transduction pathways, including tyrosine phosphorylation and protein kinase C (PKC) activation, are implicated in developmental processes.
Purpose of the Study:
- To investigate the roles of tyrosine phosphorylation and PKC activation in FGF-induced mesoderm induction in Xenopus.
- To determine if these pathways are sufficient or inhibitory for mesoderm formation.
Main Methods:
- Utilized a monoclonal anti-phosphotyrosine antibody to detect tyrosine phosphorylation.
- Administered sodium orthovanadate to elevate phosphotyrosine levels.
- Measured PKC activity and used phorbol ester (TPA) to activate PKC in ectodermal explants.
Main Results:
- Sodium orthovanadate induced mesoderm and synergized with FGF, enhancing dorsal induction.
- PKC activation was detected in FGF-treated explants, but TPA alone did not induce mesoderm.
- Simultaneous TPA and FGF treatment inhibited mesoderm induction, suggesting a negative feedback role for PKC.
Conclusions:
- Tyrosine phosphorylation is a key component of FGF-induced mesoderm induction.
- PKC activation is not sufficient for mesoderm induction and may negatively regulate the FGF signaling pathway.
- PKC activation does not affect mesoderm induction by activin A.