1. Differentiation of central nervous system neuronal cells by fibroblast-derived growth factor requires at least two signaling pathways: roles for Ras and Src.
- Author
-
Kuo WL, Chung KC, and Rosner MR
- Subjects
- Animals, Calcium-Calmodulin-Dependent Protein Kinases antagonists & inhibitors, Calcium-Calmodulin-Dependent Protein Kinases metabolism, Cell Differentiation, Cell Line, Enzyme Activation, Enzyme Inhibitors pharmacology, Flavonoids pharmacology, Hippocampus cytology, Mitogen-Activated Protein Kinase 1, Mitogen-Activated Protein Kinase 3, Neurites, 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, Rats, Fibroblast Growth Factor 2 pharmacology, Mitogen-Activated Protein Kinases, Neurons cytology, Proto-Oncogene Proteins pp60(c-src) physiology, Signal Transduction physiology, ras Proteins physiology
- Abstract
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.
- Published
- 1997
- Full Text
- View/download PDF