Identification of an atypical Grb2 carboxyl-terminal SH3 domain binding site in Gab docking proteins reveals Grb2-dependent and -independent recruitment of Gab1 to receptor tyrosine kinases.
The Gab family of docking proteins is phosphorylated in response to various growth factors and cytokines and serves to recruit multiple signaling proteins. Gab1 acts downstream from the Met-hepatocyte growth factor receptor, and Gab1 overexpression promotes Met-dependent morphogenesis of epithelial cells. Recruitment of Gab1 to Met or epidermal growth factor (EGF) receptors requires a receptor-binding site for the Grb2 adapter protein and a proline-rich domain in Gab1, defined as the Met-binding domain. To determine the requirement for Grb2 in Gab1 recruitment, we have mapped two Grb2 carboxyl-terminal SH3 domain binding sites conserved in Gab1 and related protein Gab2. One corresponds to a canonical Grb2-binding motif, whereas the second, located within the Gab1 Met-binding domain, requires the proline and arginine residues of an atypical PXXXR motif. The PXXXR motif is required but not sufficient for Grb2 binding, whereas an extended motif, PX3RX2KPX7PLD, conserved in Gab proteins as well as the Grb2/Gads-docking protein, Slp-76, efficiently competes binding of Grb2 or Gads adapter proteins. The association of Gab1 with Grb2 is required for Gab1 recruitment to the EGF receptor but not the Met receptor. Hence different mechanisms of Gab1 recruitment may reflect the distinct biological functions for Gab1 downstream from the EGF and Met receptors.
Lock
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Departments of Biochemistry, Medicine, and Oncology, Molecular Oncology Group, McGill University Health Centre, Montreal, Quebec H3A 1A1, Canada.
Royal
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Naujokas
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Park
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D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry*; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; C490895:GAB2 protein, human; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D010455:Peptides; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met