Ash/Grb-2, a SH2/SH3-containing protein, couples to signaling for mitogenesis and cytoskeletal reorganization by EGF and PDGF.
The Src homology (SH) region 2 binds to phosphorylated tyrosine residues and SH3 domains may interact with cytoskeletal molecules and GTPase-activating proteins for Rho/Rac proteins (the small GTP-binding proteins related to Ras). The recently cloned Ash/Grb-2 protein, a 25-28 kDa molecule composed entirely of SH2 and SH3 domains, is a mammalian homolog of the Caenorhabditis elegans Sem-5 protein, which communicates between a receptor protein tyrosine kinase and a Ras protein. In the present study the function of Ash/Grb-2 was investigated by microinjecting cells with an anti-Ash antibody. The antibody abolished both S phase entry and the reorganization of actin assembly to ruffle formation upon stimulation with epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). On the other hand, anti-Ash antibody had no effect on S phase entry or actin stress fiber formation induced by either serum or lysophosphatidic acid. Since the induction of DNA synthesis, ruffle induction and stress fiber formation involve a function of Ras, Rac activation and Rho activation respectively, the findings strongly suggest that Ash plays a critical role in the signaling of both pathways downstream from growth factor receptors to Ras and Rac. Consistent with this, Ash co-precipitated with EGF receptor from EGF-stimulated cells. Other proteins of approximately 21, 29, 135 and 160 kDa were also detected in the anti-Ash antibody immunoprecipitates, suggesting a role of Ash as a linker molecule in signal transduction downstream of growth factor receptors.
Matuoka
K
K
Department of Biosignal Research, Tokyo Metropolitan Institute of Gerontology, Japan.
Shibasaki
F
F
Shibata
M
M
Takenawa
T
T
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D000077214:Becaplermin; D002294:Carcinoma, Squamous Cell; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D051380:GRB2 Adaptor Protein; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007668:Kidney; D008845:Microinjections; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011506:Proteins / Q000276:immunology / Q000502:physiology*; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495950:Grb2 protein, rat; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D020574:Proto-Oncogene Proteins c-sis; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D000077214:Becaplermin; D004815:Epidermal Growth Factor; D019204:GTP-Binding Proteins