Insulin-like growth factor-I-mediated neurite outgrowth in vitro requires mitogen-activated protein kinase activation

J Biol Chem. 1997 Aug 22;272(34):21268-73. doi: 10.1074/jbc.272.34.21268.

Abstract

Insulin-like growth factor-I (IGF-I) induces neuronal differentiation in vitro. In the present study, we examined the signaling pathway underlying IGF-I-mediated neurite outgrowth. In SH-SY5Y human neuroblastoma cells, treatment with IGF-I induced concentration- and time-dependent tyrosine phosphorylation of the type I IGF receptor (IGF-IR) and extracellular signal-regulated protein kinases (ERK) 1 and 2. These effects of IGF-I were blocked by a neutralizing antibody against IGF-IR. Whereas IGF-IR phosphorylation was observed within 1 min, maximal phosphorylation of ERKs was not reached for 30 min. Both IGF-IR and ERK phosphorylation were maintained for at least 24 h. Also, the concentration dependence of IGF-I-stimulated IGF-IR and ERK tyrosine phosphorylation paralleled that of IGF-I-mediated neurite outgrowth. We further examined the role of mitogen-activated protein kinase activation in IGF-I-stimulated neuronal differentiation using the mitogen-activated protein kinase/ERK kinase inhibitor PD98059. Whereas PD98059 had no effect on IGF-IR phosphorylation, PD98059 reduced IGF-I-mediated ERK tyrosine phosphorylation and ERK phosphorylation of the substrate Elk-1. PD98059 also produced a parallel reduction of IGF-I-stimulated neurite outgrowth. Finally, consistent with its ability to block neuronal differentiation, PD98059 inhibited IGF-I-dependent changes of GAP-43 and c-myc gene expression. Together these results suggest that activation of ERKs is essential for IGF-I-stimulated neuronal differentiation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Differentiation / drug effects
  • Cells, Cultured
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Flavonoids / pharmacology
  • GAP-43 Protein
  • Gene Expression Regulation, Developmental / drug effects
  • Genes, myc
  • Humans
  • Insulin-Like Growth Factor I / physiology*
  • Membrane Glycoproteins / genetics
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase Kinases
  • Nerve Tissue Proteins / genetics
  • Neurites / ultrastructure*
  • Phosphoproteins / metabolism
  • Phosphotyrosine / metabolism
  • Protein Kinase Inhibitors
  • Receptor, IGF Type 1 / metabolism
  • Signal Transduction

Substances

  • Enzyme Inhibitors
  • Flavonoids
  • GAP-43 Protein
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • Phosphoproteins
  • Protein Kinase Inhibitors
  • Phosphotyrosine
  • Insulin-Like Growth Factor I
  • Receptor, IGF Type 1
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase Kinases
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one