RAF inhibitors promote RAS-RAF interaction by allosterically disrupting RAF autoinhibition

Nat Commun. 2017 Oct 31;8(1):1211. doi: 10.1038/s41467-017-01274-0.

Abstract

First-generation RAF inhibitors paradoxically induce ERK signaling in normal and tumor cells exhibiting RAS activity. Compound-induced RAF dimerization through stabilization of the RAF ON/active state by inhibitors has emerged as a critical contributing factor. RAF inhibitors also enhance RAS-RAF association. Although this event is thought to play a key role in priming RAF activation, the underlying mechanism is not known. Here we report that RAF inhibitors induce the disruption of intramolecular interactions between the kinase domain and its N-terminal regulatory region independently of RAS activity. This provides a molecular basis to explain the induction of RAS-RAF association by RAF inhibitors, as well as the co-operativity observed between RAS activity and RAF kinase inhibitors in driving RAF activation. Profiling of second-generation RAF inhibitors confirmed their improved mode of action, but also revealed liabilities that allowed us to discern two properties of an ideal RAF inhibitor: high-binding affinity to all RAF paralogs and maintenance of the OFF/autoinhibited state of the enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation / drug effects
  • Cell Line, Tumor
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • HEK293 Cells
  • Humans
  • Models, Biological
  • Mutation / genetics
  • Phosphorylation / drug effects
  • Protein Binding / drug effects
  • Protein Kinase Inhibitors / chemistry
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Multimerization
  • Proto-Oncogene Proteins B-raf / metabolism
  • Proto-Oncogene Proteins c-raf / antagonists & inhibitors*
  • Proto-Oncogene Proteins p21(ras) / genetics

Substances

  • KRAS protein, human
  • Protein Kinase Inhibitors
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins c-raf
  • Extracellular Signal-Regulated MAP Kinases
  • Proto-Oncogene Proteins p21(ras)

Grants and funding