BRAF inhibitors promote intermediate BRAF(V600E) conformations and binary interactions with activated RAS

Area of Science:

• Molecular biology
• Cancer research
• Biochemistry

Background:

• Oncogenic BRAF mutations are key drivers of tumor formation.
• These mutations activate the RAF-MEK-ERK signaling pathway, promoting cell proliferation.
• Understanding BRAF conformational changes and interactions is crucial for targeted therapy.

Purpose of the Study:

• To systematically track full-length BRAF conformations and interactions.
• To investigate the effects of tumorigenic mutations and RAS GTP loading on BRAF.
• To analyze the specificity and efficacy of BRAF inhibitors (BRAFi).

Main Methods:

• Engineered luciferase-based biosensors to monitor BRAF.
• Studied BRAF conformation shifts upon BRAFi binding.
• Investigated RAS:RAF interactions and nanoclustering in melanoma cells.

Main Results:

• Structurally diverse BRAFi shifted BRAF reporters between open and closed conformations.
• BRAFi binding to V600E-mutated BRAF stabilized an inactive conformation.
• This stabilization enhanced binary RAS:RAF interactions, independent of RAF dimerization.

Conclusions:

• BRAFi can induce previously unappreciated allosteric effects on mutated BRAF.
• Interference with RAS interactions antagonizes drug-induced RAS:RAF tetramer formation.
• These findings suggest mechanisms for paradoxical kinase activation and drug resistance.