IGFs stimulate zebrafish cell proliferation by activating MAP kinase and PI3-kinase-signaling pathways.
Am J Physiol Regul Integr Comp Physiol
; 280(4): R1230-9, 2001 Apr.
Article
em En
| MEDLINE
| ID: mdl-11247849
ABSTRACT
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.
Buscar no Google
Base de dados:
MEDLINE
Assunto principal:
Fator de Crescimento Insulin-Like I
/
Fator de Crescimento Insulin-Like II
/
Transdução de Sinais
/
Receptor IGF Tipo 2
/
Receptor IGF Tipo 1
/
Fosfatidilinositol 3-Quinases
/
Sistema de Sinalização das MAP Quinases
Idioma:
En
Ano de publicação:
2001
Tipo de documento:
Article