Epidermal Growth Factor Induces Coupling of Protein-tyrosine Phosphatase 1D to GRB2 via the COOH-terminal SH3 Domain of GRB2

The Src homology 2 (SH2) and SH3 domain-containing adaptor protein GRB2 and the SH2 domain-containing protein-tyrosine phosphatase 1D (PTP1D, also called SHPTP2, PTP2C, SHPTP3, Syp, or SHP-2) function as positive mediators of growth factor-induced mitogenesis. Epidermal growth factor (EGF) is a potent mitogen for MCF-10A human mammary epithelial cells and EGF receptor-expressing mouse NR6 fibroblasts. Western blot analysis of anti-PTP1D immune complexes derived from EGF-treated cells demonstrated a ligand-dependent coupling between the phosphatase and GRB2 in vivo. Probing of lysates from these cells with glutathione S-transferase (GST) fusion proteins corresponding to the individual domains of GRB2 revealed that this interaction was mediated exclusively by the COOH-terminal SH3 domain of GRB2. Importantly, a GST fusion protein containing the PTP1D SH2 domains was not capable of generating the EGF-induced linkage to GRB2. Additional experiments indicated that neither the binding of the nucleotide exchange factor Sos to GRB2 nor tyrosine phosphorylation of PTP1D was required for EGF-stimulated coupling of PTP1D to GRB2. This is the first demonstration of a growth factor- or cytokine-induced coupling of a protein through an SH3 domain and suggests that GRB2 functions to target PTP1D, in addition to Sos, to the plasma membrane in response to EGF.