Mechanism of activation of the RAF-ERK signaling pathway by oncogenic mutations of B-RAF.
Over 30 mutations of the B-RAF gene associated with human cancers have been identified, the majority of which are located within the kinase domain. Here we show that of 22 B-RAF mutants analyzed, 18 have elevated kinase activity and signal to ERK in vivo. Surprisingly, three mutants have reduced kinase activity towards MEK in vitro but, by activating C-RAF in vivo, signal to ERK in cells. The structures of wild type and oncogenic V599EB-RAF kinase domains in complex with the RAF inhibitor BAY43-9006 show that the activation segment is held in an inactive conformation by association with the P loop. The clustering of most mutations to these two regions suggests that disruption of this interaction converts B-RAF into its active conformation. The high activity mutants signal to ERK by directly phosphorylating MEK, whereas the impaired activity mutants stimulate MEK by activating endogenous C-RAF, possibly via an allosteric or transphosphorylation mechanism.
Wan
Paul T C
PT
Section of Structural Biology, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB, UK.
Garnett
Mathew J
MJ
Roe
S Mark
SM
Lee
Sharlene
S
Niculescu-Duvaz
Dan
D
Good
Valerie M
VM
Jones
C Michael
CM
Marshall
Christopher J
CJ
Springer
Caroline J
CJ
Barford
David
D
Marais
Richard
R
D000494:Allosteric Regulation / Q000235:genetics; D000818:Animals; D020134:Catalytic Domain / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000235:genetics*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation / Q000235:genetics*; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000201:enzymology / Q000235:genetics; D009857:Oncogenes / Q000235:genetics*; D009865:Oocytes; D010766:Phosphorylation; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics; D014981:Xenopus
D004791:Enzyme Inhibitors; D010770:Phosphotransferases; C482120:Braf protein, mouse; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases