The Eps8 protein coordinates EGF receptor signalling through Rac and trafficking through Rab5

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Abstract

How epidermal growth factor receptor (EGFR) signalling is linked to EGFR trafficking is largely unknown. Signalling and trafficking involve small GTPases of the Rho and Rab families, respectively. But it remains unknown whether the signalling relying on these two classes of GTPases is integrated, and, if it is, what molecular machinery is involved. Here we report that the protein Eps8 connects these signalling pathways. Eps8 is a substrate of the EGFR1, which is held in a complex with Sos1 by the adaptor protein E3b1 (ref. 2), thereby mediating activation of Rac2. Through its src homology-3 domain, Eps8 interacts with RN-tre3. We show that RN-tre is a Rab5 GTPase-activating protein, whose activity is regulated by the EGFR. By entering in a complex with Eps8, RN-tre acts on Rab5 and inhibits internalization of the EGFR. Furthermore, RN-tre diverts Eps8 from its Rac-activating function, resulting in the attenuation of Rac signalling. Thus, depending on its state of association with E3b1 or RN-tre, Eps8 participates in both EGFR signalling through Rac, and trafficking through Rab5.

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Figure 1: RN-tre is a Rab5-GAP whose catalytic activity is encoded by the TrH domain.
Figure 2: RN-tre is a Rab5-GAP in vivo and its activity is negatively regulated by EGFR.
Figure 3: Binding to Eps8 regulates RN-tre in vivo.
Figure 4: Binding of RN-tre to Eps8 results in the attenuation of Rac-mediated signalling.

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Acknowledgements

We thank B. Matoskova for reagents and for helpful discussions, and N. Gholami-Shangolabad for technical assistance. This work was supported by grants from Associazione Italiana Ricerca sul Cancro, from the Armenise-Harvard Foundation and from the CNR (Progetto Biotecnologie).

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Correspondence to Pier Paolo Di Fiore.

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