Identification of Grb2 as a novel binding partner of tumor necrosis factor (TNF) receptor I.
Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine. Its pleiotropic biological properties are signaled through two distinct cell surface receptors: the TNF receptor type I (TNFR-I) and the TNF receptor type II. Neither of the two receptors possesses tyrosine kinase activity. A large majority of TNF-alpha-dependent activities can be mediated by TNFR-I. Recently, c-Raf-1 kinase was identified as an intracellular target of a signal transduction cascade initiated by binding of TNF-alpha to TNFR-I. However, the mechanism engaged in TNF-alpha-dependent activation of c-Raf-1 kinase is still enigmatic. Here we report that the cytosolic adapter protein Grb2 is a novel binding partner of TNFR-I. Grb2 binds with its COOH-terminal SH3 domain to a PLAP motif within TNFR-I and with its NH2-terminal SH3 domain to SOS (son of sevenless). A PLAP deletion mutant of TNFR-I fails to bind Grb2. The TNFR-I/Grb2 interaction is essential for the TNF-alpha-dependent activation of c-Raf-1 kinase; activation of c-Raf-1 kinase by TNF-alpha can be blocked by coexpression of Grb2 mutants harboring inactivating point mutations in the NH2- or COOH-terminal SH3 domain, cell-permeable peptides that disrupt the Grb2/TNFR-I interaction or transdominant negative Ras. Functionality of the TNFR-I/Grb2/SOS/Ras interaction is a prerequisite but not sufficient for TNF-alpha-dependent activation of c-Raf-1 kinase. Inhibition of the TNFR-I/FAN (factor associated with neutral sphingomyelinase) interaction, which is essential for TNF-alpha-dependent activation of the neutral sphingomyelinase, either by cell-permeable peptides or by deletion of the FAN binding domain, prevents activation of c-Raf-1 kinase. In conclusion, binding of the Grb2 adapter protein via its COOH-terminal SH3 domain to the nontyrosine kinase receptor TNFR-I results in activation of a signaling cascade known so far to be initiated, in the case of the tyrosine kinase receptors, by binding of the SH2 domain of Grb2 to phosphotyrosine.
Hildt
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Klinikum der Universität Ulm, Ulm, 89081 Germany.
Oess
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D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004789:Enzyme Activation; D051380:GRB2 Adaptor Protein; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D015398:Signal Transduction; D020664:Son of Sevenless Proteins; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D015703:Antigens, CD; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D008565:Membrane Proteins; D011506:Proteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D011994:Recombinant Proteins; D020664:Son of Sevenless Proteins; D014409:Tumor Necrosis Factor-alpha; D019908:Proto-Oncogene Proteins c-raf