title: Integrin-mediated signal transduction linked to Ras pathway by GRB2 binding to focal adhesion kinase.
abstract: The cytoplasmic focal adhesion protein-tyrosine kinase (FAK) localizes with surface integrin receptors at sites where cells attach to the extracellular matrix. Increased FAK tyrosine phosphorylation occurs upon integrin engagement with fibronectin. Here we show that adhesion of murine NIH3T3 fibroblasts to fibronectin promotes SH2-domain-mediated association of the GRB2 adaptor protein and the c-Src protein-tyrosine kinase (PTK) with FAK in vivo, and also results in activation of mitogen-activated protein kinase (MAPK). In v-Src-transformed NIH3T3, the association of v-Src, GRB2 and Sos with FAK is independent of cell adhesion to fibronectin. The GRB2 SH2 domain binds directly to tyrosine-phosphorylated FAK. Mutation of tyrosine residue 925 of FAK (YENV motif) to phenylalanine blocks GRB2 SH2-domain binding to FAK in vitro. Our results show that fibronectin binding to integrins on NIH3T3 fibroblasts promotes c-Src and FAK association and formation of an integrin-activated signalling complex. Phosphorylation of FAK at Tyr 925 upon fibronectin stimulation creates an SH2-binding site for GRB2 which may link integrin engagement to the activation of the Ras/MAPK signal transduction pathway.
authors.affiliation: Molecular Biology and Virology Laboratory, Salk Institute, San Diego, California 92186.
authors.forename: D D
authors.initials: DD
authors.lastname: Schlaepfer
authors.forename: S K
authors.initials: SK
authors.lastname: Hanks
authors.forename: T
authors.initials: T
authors.lastname: Hunter
authors.forename: P
authors.initials: P
authors.lastname: van der Geer
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002645:Chickens; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D051380:GRB2 Adaptor Protein; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D016023:Integrins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D011494:Protein Kinases; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; D019061:src-Family Kinases; C000631346:CSK protein, human