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EPS8 and E3B1 transduce signals from Ras to Rac.

The small guanine nucleotide (GTP)-binding protein Rac regulates mitogen-induced cytoskeletal changes and c-Jun amino-terminal kinase (JNK), and its activity is required for Ras-mediated cell transformation. Epistatic analysis placed Rac as a key downstream target in Ras signalling; however, the biochemical mechanism regulating the cross-talk among these small GTP-binding proteins remains to be elucidated. Eps8 (relative molecular mass 97,000) is a substrate of receptors with tyrosine kinase activity which binds, through its SH3 domain, to a protein designated E3b1/Abi-1. Here we show that Eps8 and E3b1/Abi-1 participate in the transduction of signals from Ras to Rac, by regulating Rac-specific guanine nucleotide exchange factor (GEF) activities. We also show that Eps8, E3b1 and Sos-1 form a tri-complex in vivo that exhibits Rac-specific GEF activity in vitro. We propose a model in which Eps8 mediates the transfer of signals between Ras and Rac, by forming a complex with E3b1 and Sos-1.

Pubmed ID: 10499589


  • Scita G
  • Nordstrom J
  • Carbone R
  • Tenca P
  • Giardina G
  • Gutkind S
  • Bjarneg√•rd M
  • Betsholtz C
  • Di Fiore PP



Publication Data

September 16, 1999

Associated Grants


Mesh Terms

  • 3T3 Cells
  • Adaptor Proteins, Signal Transducing
  • Animals
  • COS Cells
  • Carrier Proteins
  • Cloning, Molecular
  • Cytoskeletal Proteins
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • Genetic Vectors
  • Guanine Nucleotide Exchange Factors
  • Guanosine Triphosphate
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Protein Binding
  • Proteins
  • Signal Transduction
  • rac GTP-Binding Proteins
  • ras Guanine Nucleotide Exchange Factors
  • ras Proteins