BRAF oncogenic mutants evade autoinhibition through a common mechanism

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.