Epidermal growth factor regulates p21ras through the formation of a complex of receptor, Grb2 adapter protein, and Sos nucleotide exchange factor.
Antisera against murine Son of sevenless (Sos) recognize a protein of M(r) 155,000 in rat-1 fibroblasts with specific guanine nucleotide exchange activity toward p21c-Ha-ras. Epidermal growth factor (EGF) receptor coimmunoprecipitates with Sos from EGF-stimulated, but not quiescent, cells. The SH2 and SH3 domain-containing "adapter" protein Grb2 is also found in Sos immunoprecipitates in an EGF-inducible manner. In vitro reconstitution shows that Grb2 is required for the binding of activated EGF receptor to Sos. A phosphopeptide corresponding to tyrosine 1068 of the EGF receptor blocks both the assembly of the complex and EGF stimulation of nucleotide exchange on p21ras in a permeabilized cell system. These results suggest that EGF-induced activation of nucleotide exchange on p21ras proceeds through the recruitment of cytosolic Sos to a complex with EGF receptor and Grb2 at the plasma membrane.
Signal Transduction Laboratory, Imperial Cancer Research Fund, Lincoln's Inn Fields, London, England.
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Buday
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Downward
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000906:Antibodies; D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007106:Immune Sera; D015151:Immunoblotting; D007700:Kinetics; D008565:Membrane Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020664:Son of Sevenless Proteins; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D000906:Antibodies; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495950:Grb2 protein, rat; D007106:Immune Sera; D008565:Membrane Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D020664:Son of Sevenless Proteins; D004815:Epidermal Growth Factor; D005982:Glutathione Transferase; D066246:ErbB Receptors; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)