Differential Interactions of the Growth Factor Receptor-bound Protein 2 N-SH3 Domain with Son of Sevenless and Dynamin

In this paper, we show that the 36-45 surface-exposed sequence WYKAELNGKD of growth factor receptor-bound protein 2 (Grb2) N-SH3 domain inhibits the interaction between Grb2 and a 97-kDa protein identified as dynamin. Moreover, the peptide GPPPQVPSRPNR from dynamin also blocks the binding of dynamin to the proline-rich recognition platform of Grb2. Mutations in the 36-45 motif show that Glu-40 is critical for dynamin recognition. These observations were confirmed by immunoprecipitation experiments, carried out using ER 22 cells. It was also observed that the proline-rich peptide from dynamin was unable to dissociate the Grb2.Sos complex, whereas the proline-rich peptide from Son of sevenless (Sos) inhibited Grb2. dynamin interaction. A time-dependent stimulation of epidermal growth factor receptor overexpressing clone 22 (ER 22) cells by epidermal growth factor resulted in an immediate increase of the Grb2.Sos complex and a concomitant decrease in Grb2.dynamin. This suggests that the recruitment of Grb2.Sos to the membrane, triggered by epidermal growth factor stimulation, activates the Ras-dependent signaling and simultaneously enhances free dynamin levels, leading to both receptor internalization and endocytotic processes.