DIRAS3 (ARHI) Blocks RAS/MAPK Signaling by Binding Directly to RAS and Disrupting RAS Clusters.

Oncogenic RAS mutations drive cancers at many sites. Recent reports suggest that RAS dimerization, multimerization, and clustering correlate strongly with activation of RAS signaling. We have found that re-expression of DIRAS3, a RAS-related small GTPase tumor suppressor that is downregulated in multiple cancers, inhibits RAS/mitogen-activated protein kinase (MAPK) signaling by interacting directly with RAS-forming heteromers, disrupting RAS clustering, inhibiting Raf kinase activation, and inhibiting transformation and growth of cancer cells and xenografts. Disruption of K-RAS cluster formation requires the N terminus of DIRAS3 and interaction of both DIRAS3 and K-RAS with the plasma membrane. Interaction of DIRAS3 with both K-RAS and H-RAS suggests a strategy for inhibiting oncogenic RAS function.