IGFs stimulate zebrafish cell proliferation by activating MAP kinase and PI3-kinase-signaling pathways

Pozios, K.C., Ding, J., Degger, B., Upton, Z., and Duan, C.
American journal of physiology. Regulatory, integrative and comparative physiology   280(4): R1230-R1239 (Journal)
Registered Authors
Duan, Cunming
insulin-like growth factor; insulin-like growth factor I receptor; mitogen-activated protein kinase; phosphatidylinositol 3-kinase; protein kinase B; zebrafish embryos; deoxyribonucleic acid synthesis
MeSH Terms
  • Animals
  • Cell Division/drug effects
  • Cell Division/physiology
  • Cells, Cultured
  • Chromones/pharmacology
  • Embryo, Nonmammalian
  • Flavonoids/pharmacology
  • Humans
  • Insulin/pharmacology
  • Insulin-Like Growth Factor I/pharmacology*
  • Insulin-Like Growth Factor II/pharmacology*
  • Kinetics
  • MAP Kinase Signaling System/drug effects
  • MAP Kinase Signaling System/physiology*
  • Mitogen-Activated Protein Kinases/metabolism
  • Morpholines/pharmacology
  • Phosphatidylinositol 3-Kinases/metabolism*
  • Receptor, IGF Type 1/drug effects
  • Receptor, IGF Type 1/physiology*
  • Receptor, IGF Type 2/drug effects
  • Receptor, IGF Type 2/physiology*
  • Recombinant Proteins/pharmacology
  • Salmon
  • Signal Transduction/drug effects
  • Signal Transduction/physiology*
  • Zebrafish
11247849 Full text @ Am. J. Physiol. Regul. Integr. Comp. Physiol.
Insulin-like growth factor (IGF)-I and -II have been cloned from a number of teleost species, but their cellular actions in fish are poorly defined. In this study, we show that both IGF-I and -II stimulated zebrafish embryonic cell proliferation and DNA synthesis in a concentration-dependent manner, whereas insulin had little mitogenic activity. Affinity cross-linking and immunoblotting studies revealed the presence of IGF receptors with the characteristics of the mammalian type I IGF receptor. Competitive binding assay results indicated that the binding affinities of the zebrafish IGF-I receptors to IGF-I, IGF-II, and insulin are 1.9, 2.6, and >190 nM, indicating that IGF-I and -II bind to the IGF-I receptor(s) with approximately equal high affinity. To further investigate the cellular mechanism of IGF actions, we have studied the effects of IGFs on two major signal transduction pathways: mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3 kinase). IGFs activated MAPK in zebrafish embryonic cells in a dose-dependent manner. This activation occurred within 5 min of IGF-I stimulation and disappeared after 1 h. IGF-I also caused a concentration-dependent activation of protein kinase B, a downstream target of PI3 kinase, this activation being sustained for several hours. Inhibition of MAPK activation by the MAPK kinase inhibitor PD-98059 inhibited the IGF-I-stimulated DNA synthesis. Similarly, use of the PI3 kinase inhibitor LY-294002 also inhibited IGF-I-stimulated DNA synthesis. When both the MAPK and PI3 kinase pathways were inhibited using a combination of these compounds, the IGF-I-stimulated DNA synthesis was completely negated. These results indicate that both IGF-I and -II are potent mitogens for zebrafish embryonic cells and that activation of both the MAPK and PI3 kinase-signaling pathways is required for the mitogenic action of IGFs in zebrafish embryonic cells.
Genes / Markers
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes