Raf-1 and p21v-ras cooperate in the activation of mitogen-activated protein kinase

Proc Natl Acad Sci U S A. 1993 Jun 15;90(12):5772-6. doi: 10.1073/pnas.90.12.5772.


Mitogen-activated protein (MAP) kinases Raf-1, pp60src, and p21ras all play important roles in the transfer of signals from the cell surface to the nucleus. We have used the baculovirus/Sf9 insect cell system to elucidate the regulatory relationships between pp60v-src, p21v-ras, MAP kinase (p44erk1/mapk), and Raf-1. In Sf9 cells, p44erk1/mapk is activated by coexpression with either v-Raf or a constitutively activated form of Raf-1 (Raf22W). In contrast, p44erk1/mapk is activated to only a limited extent by coexpression with either Raf-1 or p21v-ras alone. This activation of p44erk1/mapk is greatly enhanced by coexpression with both p21v-ras and Raf-1. Since we have previously shown that p21v-ras stimulates Raf-1 activity, the activation of p44erk1/mapk by p21v-ras may occur exclusively via a Raf-1-dependent pathway. However, a dominant-inhibitory mutant of Raf-1 (Raf301) does not block the activation of p44erk1/mapk by p21-v-ras. Further, pp60v-src, which activates Raf-1 at least as effectively as p21v-ras, fails to enhance p44erk1/mapk activity greatly when coexpressed with Raf-1. These data suggest that activation of p44erk1/mapk by p21v-ras may occur via both Raf-1-dependent and Raf-1-independent pathways.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies
  • Antibodies, Monoclonal
  • Antigen-Antibody Complex / metabolism
  • Baculoviridae / genetics
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Cell Line
  • Cloning, Molecular
  • Enzyme Activation
  • Genetic Vectors
  • Molecular Sequence Data
  • Moths
  • Mutagenesis
  • Oncogene Protein p21(ras) / metabolism*
  • Protein Kinases / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-raf
  • Rats
  • Recombinant Proteins / metabolism
  • Restriction Mapping
  • Transfection


  • Antibodies
  • Antibodies, Monoclonal
  • Antigen-Antibody Complex
  • Proto-Oncogene Proteins
  • Recombinant Proteins
  • Protein Kinases
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Oncogene Protein p21(ras)