Mutation-specific structural changes in BRAF: understanding dimerization and drug binding for targeted therapy.

Abstract

The dimerization of BRAF with CRAF is a critical regulatory mechanism within the MAPK/ERK signaling cascade, and its disruption by mutations in the BRAF kinase domain contributes to tumorigenesis across various cancers. While wild-type BRAF depends on RAS-mediated dimerization for activation, oncogenic mutations alter this dependency, impacting structural conformation, ATP/drug binding, and downstream signaling. Despite extensive functional data, the structural and biophysical consequences of these mutations remain poorly defined. Here, we examine five BRAF mutations oncogenic (V600E, G469E, D594G) and benign (N581S, E586K) through molecular dynamics simulations, ATP-binding assessments, and drug interaction analyses involving Sorafenib and U0126. Our results suggest that V600E stabilizes the activation loop in an active, monomeric form, bypassing dimerization and conferring resistance to Sorafenib. G469E retains dimerization dependence, shows intermediate activity, and exhibits moderate drug responsiveness. D594G, a kinase-inactive mutant, functions as a scaffold for CRAF activation, with transient ATP-induced stabilization but minimal Sorafenib sensitivity. Benign variants maintain wild-type-like structural integrity, dimer stability, and inhibitor response. Simulations highlight mutation-specific effects on key regions, including the P-loop, DFG motif, and catalytic loop, and reveal distinct conformational landscapes through free energy and compactness analyses. Our findings provide a mechanistic framework linking structure to function in BRAF mutants, supporting mutation-guided therapeutic strategies in precision oncology.