Differentiation of central nervous system neuronal cells by fibroblast-derived growth factor requires at least two signaling pathways: roles for Ras and Src

Mol Cell Biol. 1997 Aug;17(8):4633-43. doi: 10.1128/MCB.17.8.4633.


To evaluate the role of mitogen-activated protein (MAP) kinase and other signaling pathways in neuronal cell differentiation by basic fibroblast-derived growth factor (bFGF), we used a conditionally immortalized cell line from rat hippocampal neurons (H19-7). Previous studies have shown that activation of MAP kinase kinase (MEK) is insufficient to induce neuronal differentiation of H19-7 cells. To test the requirement for MEK and MAP kinase (ERK1 and ERK2), H19-7 cells were treated with the MEK inhibitor PD098059. Although the MEK inhibitor blocked the induction of differentiation by constitutively activated Raf, the H19-7 cells still underwent differentiation by bFGF. These results suggest that an alternative pathway is utilized by bFGF for differentiation of the hippocampal neuronal cells. Expression in the H19-7 cells of a dominant-negative Ras (N17-Ras) or Raf (C4-Raf) blocked differentiation by bFGF, suggesting that Ras and probably Raf are required. Expression of dominant-negative Src (pcSrc295Arg) or microinjection of an anti-Src antibody blocked differentiation by bFGF in H19-7 cells, indicating that bFGF also signals through a Src kinase-mediated pathway. Although neither constitutively activated MEK (MEK-2E) nor v-Src was sufficient individually to differentiate the H19-7 cells, coexpression of constitutively activated MEK and v-Src induced neurite outgrowth. These results suggest that (i) activation of MAP kinase (ERK1 and ERK2) is neither necessary nor sufficient for differentiation by bFGF; (ii) activation of Src kinases is necessary but not sufficient for differentiation by bFGF; and (iii) differentiation of H19-7 neuronal cells by bFGF requires at least two signaling pathways activated by Ras and Src.

Publication types

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

MeSH terms

  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Cell Differentiation
  • Cell Line
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Fibroblast Growth Factor 2 / pharmacology*
  • Flavonoids / pharmacology
  • Hippocampus / cytology
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases*
  • Neurites
  • Neurons / cytology*
  • Neurons / physiology
  • Oncogene Protein pp60(v-src) / genetics
  • Oncogene Protein pp60(v-src) / physiology
  • Protein Serine-Threonine Kinases / physiology
  • Proto-Oncogene Proteins / physiology
  • Proto-Oncogene Proteins c-raf
  • Proto-Oncogene Proteins pp60(c-src) / genetics
  • Proto-Oncogene Proteins pp60(c-src) / physiology*
  • Rats
  • Signal Transduction / physiology*
  • ras Proteins / physiology*


  • Enzyme Inhibitors
  • Flavonoids
  • Proto-Oncogene Proteins
  • Fibroblast Growth Factor 2
  • Oncogene Protein pp60(v-src)
  • Proto-Oncogene Proteins pp60(c-src)
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • ras Proteins
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one