title: Membrane targeting of Grb2-associated binder-1 (Gab1) scaffolding protein through Src myristoylation sequence substitutes for Gab1 pleckstrin homology domain and switches an epidermal growth factor response to an invasive morphogenic program.
abstract: The hepatocyte growth factor receptor tyrosine kinase Met promotes cell dissociation and the inherent morphogenic program of epithelial cells. In a search for substrates downstream from Met, we have previously identified the Grb2-associated binder-1 (Gab1) as critical for the morphogenic program. Gab1 is a scaffold protein that acts to diversify the signal downstream from the Met receptor through its ability to couple with multiple signal transduction pathways. Gab1 contains a pleckstrin homology (PH) domain with specificity for phosphatidylinositol 3,4,5-trisphosphate. The phospholipid binding capacity of the Gab1 PH domain is required for the localization of Gab1 at sites of cell-cell contact in colonies of epithelial cells and for epithelial morphogenesis, suggesting that PH domain-dependent subcellular localization of Gab1 is a prerequisite for function. We have investigated the requirement for membrane localization of Gab1 for biological activity. We show that substitution of the Gab1 PH domain with the myristoylation signal from the c-Src protein is sufficient to replace the Gab1 PH domain for epithelial morphogenesis. The membrane targeting of Gab1 enhances Rac activity in the absence of stimulation and switches a nonmorphogenic noninvasive response to epidermal growth factor to a morphogenic invasive program. These results suggest that the subcellular localization of Gab1 is a critical determinant for epithelial morphogenesis and invasiveness.
authors.affiliation: Department of Medicine, Molecular Oncology Group, McGill University Health Centre, McGill University, Montreal, Quebec, H3A 1A1, Canada.
authors.forename: Christiane R
authors.initials: CR
authors.lastname: Maroun
authors.forename: Monica A
authors.initials: MA
authors.lastname: Naujokas
authors.forename: Morag
authors.initials: M
authors.lastname: Park
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001798:Blood Proteins / Q000737:chemistry; D000081247:CSK Tyrosine-Protein Kinase; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004285:Dogs; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D007700:Kinetics; D009024:Morphogenesis; D009154:Mutation; D019814:Myristic Acid / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D019061:src-Family Kinases
chemical_list: D000199:Actins; D001798:Blood Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C039077:platelet protein P47; D019814:Myristic Acid; D004815:Epidermal Growth Factor; D011505:Protein-Tyrosine Kinases; D019859:Proto-Oncogene Proteins c-met; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases