Mechanism of activation of the RAF-ERK signaling pathway by oncogenic mutations of B-RAF.

Abstract

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.

• Authors: Paul T C Wan, Mathew J Garnett, S Mark Roe, Sharlene Lee, Dan Niculescu-Duvaz, Valerie M Good, C Michael Jones, Christopher J Marshall, Caroline J Springer, David Barford, Richard Marais, Cancer Genome Project
• Journal: Cell (Cell) Vol. 116 Issue 6 Pg. 855-67 (Mar 19 2004) ISSN: 0092-8674 [Print] United States
• PMID: 15035987 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Enzyme Inhibitors
• Phosphotransferases
• Braf protein, mouse
• Proto-Oncogene Proteins B-raf
• Proto-Oncogene Proteins c-raf
• Mitogen-Activated Protein Kinases
• MAP Kinase Kinase 1
• MAP2K1 protein, human
• Map2k1 protein, mouse
• Mitogen-Activated Protein Kinase Kinases

Topics

• Allosteric Regulation (genetics)
• Animals
• Catalytic Domain (genetics)
• Cell Transformation, Neoplastic (genetics)
• Enzyme Inhibitors (pharmacology)
• Gene Expression Regulation, Enzymologic (genetics)
• MAP Kinase Kinase 1
• MAP Kinase Signaling System (genetics)
• Mice
• Mitogen-Activated Protein Kinase Kinases (genetics, metabolism)
• Mitogen-Activated Protein Kinases (genetics)
• Models, Molecular
• Molecular Conformation
• Mutation (genetics)
• NIH 3T3 Cells
• Neoplasms (enzymology, genetics)
• Oncogenes (genetics)
• Oocytes
• Phosphorylation
• Phosphotransferases (genetics, metabolism)
• Proto-Oncogene Proteins B-raf
• Proto-Oncogene Proteins c-raf (antagonists & inhibitors, genetics, metabolism)
• Up-Regulation (genetics)
• Xenopus