Targeting the α4-α5 interface of RAS results in multiple levels of inhibition

Small GTPases. 2019 Sep;10(5):378-387. doi: 10.1080/21541248.2017.1333188. Epub 2017 Dec 31.


Generation of RAS-targeted therapeutics has long been considered a "holy grail" in cancer research. However, a lack of binding pockets on the surface of RAS and its picomolar affinity for guanine nucleotides have made isolation of inhibitors particularly challenging. We recently described a monobody, termed NS1, that blocks RAS signaling and oncogenic transformation. NS1 binds to the α4-β6-α5 interface of H-RAS and K-RAS thus preventing RAS dimerization and nanoclustering, which in turn prevents RAS-stimulated dimerization and activation of RAF. Interestingly, NS1 reduces interaction of oncogenic K-RAS, but not H-RAS, with RAF and reduces K-RAS plasma membrane localization. Here, we show that these isoform specific effects of NS1 on RAS:RAF are due to the distinct hypervariable regions of RAS isoforms. NS1 inhibited wild type RAS function by reducing RAS GTP levels. These findings reveal that NS1 disrupts RAS signaling through a mechanism that is more complex than simply inhibiting RAS dimerization and nanoclustering.

Keywords: H-RAS; K-RAS; NS1 monobody; RAS chimera; RAS dimerization; RAS inhibitor; RAS nanoclustering.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Video-Audio Media

MeSH terms

  • Cell Membrane* / chemistry
  • Cell Membrane* / enzymology
  • Cell Membrane* / genetics
  • HEK293 Cells
  • Humans
  • Protein Kinase Inhibitors / chemistry*
  • Protein Multimerization*
  • Protein Structure, Secondary
  • Proto-Oncogene Proteins p21(ras)* / antagonists & inhibitors
  • Proto-Oncogene Proteins p21(ras)* / chemistry
  • Proto-Oncogene Proteins p21(ras)* / genetics
  • Proto-Oncogene Proteins p21(ras)* / metabolism
  • Signal Transduction*


  • KRAS protein, human
  • Protein Kinase Inhibitors
  • HRAS protein, human
  • Proto-Oncogene Proteins p21(ras)