Raf-1 and p21v-ras cooperate in the activation of mitogen-activated protein kinase.
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.
Dana-Farber Cancer Institute, Boston, MA.
N G
NG
Williams
H
H
Paradis
S
S
Agarwal
D L
DL
Charest
S L
SL
Pelech
T M
TM
Roberts
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex / Q000378:metabolism; D016367:Baculoviridae / Q000235:genetics; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002460:Cell Line; D003001:Cloning, Molecular; D004789:Enzyme Activation; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D009036:Moths; D016296:Mutagenesis; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D014162:Transfection
D000906:Antibodies; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D015689:Oncogene Protein p21(ras)