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Updated: Mar 7, 2026
Characterize Disease-related Mutants of RAF Family Kinases by Using a Set of Practical and Feasible Methods
Published on: July 17, 2019
BRAF oncogenic mutants evade autoinhibition through a common mechanism
Hugo Lavoie1, Ting Jin1, Driss Lajoie1
1Institute for Research in Immunology and Cancer, Laboratory of Intracellular Signaling, Université de Montréal, Montréal, QC, Canada.
Abstract:
Uncontrolled activation of the rat sarcoma (RAS)-extracellular signal-regulated kinase (ERK) pathway drives tumor growth, often because of oncogenic BRAF mutations. BRAF regulation, involving monomeric autoinhibition and activation by dimerization, has been intensely scrutinized, but mechanisms enabling oncogenic mutants to evade regulation remain unclear. By using cryo-electron microscopy, we solved the three-dimensional structures of the three oncogenic BRAF mutant classes, including the common V600E variant. These mutations disrupted wild-type BRAF's autoinhibited state, mediated by interactions between the cysteine-rich domain and kinase domain, thereby shifting the kinase domain into a preactivated conformation. This structural change likely results from helix αC displacement. PLX8394, a BRAF inhibitor that stabilizes helix αC in an inactive conformation, restored the autoinhibited conformation of oncogenic BRAF, explaining the properties of this class of compounds.
Insights
Oncogenic BRAF mutations disrupt normal regulation, leading to uncontrolled tumor growth. Structural analysis revealed how these mutations activate BRAF, and how inhibitors like PLX8394 restore its inactive state.
Area of Science:
- Molecular biology
- Structural biology
- Cancer research
Background:
- The RAS-ERK pathway is crucial for cell signaling, and its uncontrolled activation by BRAF mutations drives tumor growth.
- Understanding BRAF regulation and how oncogenic mutants evade it is key to developing targeted therapies.
Purpose of the Study:
- To elucidate the structural mechanisms by which oncogenic BRAF mutants evade normal regulatory processes.
- To understand the mechanism of action of BRAF inhibitors like PLX8394.
Main Methods:
- Cryo-electron microscopy was used to determine the 3D structures of oncogenic BRAF mutants.
- Structural analysis focused on interactions between the cysteine-rich domain and kinase domain.
Main Results:
- Oncogenic BRAF mutations disrupt the autoinhibited state by altering interactions between the cysteine-rich and kinase domains.
- Mutations shift the kinase domain to a preactivated conformation, likely due to helix αC displacement.
- The BRAF inhibitor PLX8394 was shown to stabilize helix αC, restoring the autoinhibited conformation in oncogenic BRAF.
Conclusions:
- BRAF mutations promote a preactivated kinase conformation by disrupting autoinhibition.
- BRAF inhibitors targeting helix αC can restore the wild-type autoinhibited state, offering a therapeutic strategy.
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