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Raf-1 is not a major upstream regulator of MAP kinases in rat fibroblasts

S Kizaka-Kondoh1, H Okayama

  • 1Okayama Cell Switching Project, Erato, Kyoto, Japan.

FEBS Letters
|December 27, 1993
PubMed

Insights

Raf-1 kinase is not the primary upstream activator of MAP kinases (ERK1 and ERK2) in NRK cells. These findings suggest ERK1 and ERK2 do not mediate oncogenic signals from Raf-1 kinase.

Area of Science:

  • Cell biology
  • Molecular oncology
  • Signal transduction

Background:

  • Rat kidney (NRK) cells are susceptible to oncogene-induced transformation.
  • Raf-1 kinase is a key signaling molecule in cellular transformation pathways.
  • Antisense RNA can be used to block specific gene expression, such as Raf-1.

Purpose of the Study:

  • To investigate the role of Raf-1 kinase in the activation of MAP kinases (ERK1 and ERK2) in NRK cells.
  • To determine if ERK1 and ERK2 mediate oncogenic signals from Raf-1 kinase.
  • To understand the signaling pathways involved in oncogene-induced cell transformation.

Main Methods:

  • Generation of NRK cell clones (RCR cells) with blocked Raf-1 production using antisense RNA.
  • Stimulation of RCR and NRK cells with oncogenic and non-oncogenic stimuli.
  • Analysis of MAP kinase (ERK1 and ERK2) activation levels and time courses in response to stimuli.

Main Results:

  • MAP kinases (ERK1 and ERK2) were activated similarly in RCR and NRK cells, regardless of the stimulus.
  • Blocking Raf-1 production in RCR cells did not prevent ERK1/ERK2 activation.
  • No significant elevation of ERK activities was observed in oncogene-transformed NRK cells.

Conclusions:

  • Raf-1 kinase is not the major upstream activator of ERK1 and ERK2 in NRK cells.
  • ERK1 and ERK2 are unlikely to mediate oncogenic signals originating from Raf-1 kinase.
  • Alternative signaling pathways may be involved in Raf-1-mediated oncogenic transformation.

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