title: Growth factors stimulate tyrosine dephosphorylation of p75 and its dissociation from the SH2 domain of Grb2.
abstract: The growth factor receptor-binding protein (Grb2) has a key role in initiating the mitogen-activated protein kinase signaling cascade in major cell regulatory pathways. The binding of proteins to the SH2 domain of Grb2 has been reported to occur mainly after they are tyrosine-phosphorylated following receptor activation. Using an in vitro binding assay, immunoprecipitation, and Far Western techniques, we report that in quiescent cells a 75-kDa protein binds directly to the SH2 domain of Grb2. All of the tyrosine-phosphorylated p75 protein co-localizes with Grb2.Sos complex in the cytosolic fraction of the cell in vivo and undergoes tyrosine dephosphorylation when cells are treated with mitogenic ligands such as epidermal, platelet-derived, and fibroblast growth factors, endothelin-1, and bombesin but not tumor necrosis factor-alpha, interferon-alpha and -gamma, interleukein-6, and leukemic inhibitory factor, which are either cell growth inhibitory or not significantly mitogenic. The dephosphorylation of p75 and the ensuing dissociation from Grb2 is rapid, occurring within 30 s following mitogenic stimulation by ligands such as epidermal growth factor, suggesting p75 to be an early component in the signal transduction pathways involving Grb2.
authors.affiliation: Signal Transduction Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Singapore 119076, Republic of Singapore.
authors.forename: Y P
authors.initials: YP
authors.lastname: Lim
authors.forename: B C
authors.initials: BC
authors.lastname: Low
authors.forename: S H
authors.initials: SH
authors.lastname: Ong
authors.forename: G R
authors.initials: GR
authors.lastname: Guy
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D051380:GRB2 Adaptor Protein; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D006133:Growth Substances; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D019000:Phosphotyrosine; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D066246:ErbB Receptors