2. Academic Validation
  3. BRAF inhibitors promote intermediate BRAF(V600E) conformations and binary interactions with activated RAS

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

  • Sci Adv. 2019 Aug 14;5(8):eaav8463. doi: 10.1126/sciadv.aav8463.
Ruth Röck 1,  Johanna E Mayrhofer 1,  Omar Torres-Quesada 1,  Florian Enzler 1,  Andrea Raffeiner 1,  Philipp Raffeiner 1,  Andreas Feichtner 1,  Roland G Huber 2,  Shohei Koide 3,  Susan S Taylor 4,  Jakob Troppmair 5,  Eduard Stefan 1
Affiliations

Affiliations

  • 1 Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria.
  • 2 Bioinformatics Institute (BII), Agency for Science Technology and Research (ASTAR), Singapore 138671, Singapore.
  • 3 Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine and Laura and Isaac Perlmutter Cancer Center, New York University Langone Medical Center, New York, NY 10016, USA.
  • 4 Department of Pharmacology, Department of Chemistry and Biochemistry, and Howard Hughes Medical Institute, University of California, San Diego, San Diego, CA 92093, USA.
  • 5 Daniel Swarovski Research Laboratory, Department of Visceral, Transplant and Thoracic Surgery, Innsbruck Medical University, Innrain 66, 6020 Innsbruck, Austria.
PMID: 31453322 DOI: 10.1126/sciadv.aav8463
Abstract

Oncogenic BRaf mutations initiate tumor formation by unleashing the autoinhibited kinase conformation and promoting RAS-decoupled proliferative RAF-MEK-ERK signaling. We have engineered luciferase-based biosensors to systematically track full-length BRaf conformations and interactions affected by tumorigenic kinase mutations and GTP loading of Ras. Binding of structurally diverse αC-helix-OUT BRaf inhibitors (BRAFi) showed differences in specificity and efficacy by shifting patient mutation-containing BRaf reporters from the definitive opened to more closed conformations. Unexpectedly, BRAFi engagement with the catalytic pocket of V600E-mutated BRaf stabilized an intermediate and inactive kinase conformation that enhanced binary RAS:RAF interactions, also independently of Raf dimerization in melanoma cells. We present evidence that the interference with Ras interactions and nanoclustering antagonizes the sequential formation of drug-induced RAS:RAF tetramers. This suggests a previously unappreciated allosteric effect of Anticancer drug-driven intramolecular communication between the kinase and RAS-binding domains of mutated BRaf, which may further promote paradoxical kinase activation and drug resistance mechanisms.

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