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.[1]References
- EPS8 and E3B1 transduce signals from Ras to Rac. Scita, G., Nordstrom, J., Carbone, R., Tenca, P., Giardina, G., Gutkind, S., Bjarnegård, M., Betsholtz, C., Di Fiore, P.P. Nature (1999) [Pubmed]
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