ERK signalling and oncogene transformation are not impaired in cells lacking A-Raf.
Previous studies have indicated an important role for the Raf family of protein kinases in controlling cellular responses to extracellular stimuli and activated oncogenes, through their ability to activate the MEK/ERKs. To investigate the specific role of A-Raf in this process we generated A-Raf deficient mouse embryonic fibroblasts (MEFs) and embryonic stem (ES) cells by gene targeting and characterized their ability to undergo proliferation, differentiation, apoptosis, ERK activation, and transformation by oncogenic Ras and Src. The A-Raf deficient cells are not disrupted for any of these processes, despite the fact that this protein is normally expressed at high levels in both cell types. This implies either that A-Raf plays no role in MEK/ERK activation, that its function is fully compensated by other Raf proteins or MEK kinases or that its role in MEK/ERK activation is highly tissue-specific. Interestingly, B-Raf and Raf-1 activity towards MEK as measured by the immunoprecipitation kinase cascade assay are both significantly increased in the A-Raf deficient MEFs.
Mercer
Kathryn
K
Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, UK.
Chiloeches
Antonio
A
Hüser
Martin
M
Kiernan
Michelle
M
Marais
Richard
R
Pritchard
Catrin
C
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D019070:Cell Lineage; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000473:pathology*; D004789:Enzyme Activation; D005347:Fibroblasts; D011905:Genes, ras / Q000235:genetics; D016391:Genes, src / Q000235:genetics; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009857:Oncogenes / Q000235:genetics*; D016133:Polymerase Chain Reaction; D048491:Proto-Oncogene Proteins A-raf; D019908:Proto-Oncogene Proteins c-raf / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D013234:Stem Cells; D013724:Teratoma / Q000235:genetics / Q000473:pathology
D048491:Proto-Oncogene Proteins A-raf; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases