title: SH2 domain proteins as high-affinity receptor tyrosine kinase substrates.
abstract: Activation of a growth factor receptor tyrosine kinase (RTK) is accompanied by a rapid autophosphorylation of the receptor on tyrosine residues. Receptor activation has been shown to promote the association of signal-transducing proteins containing SH2 domains (second domain of src homology). These receptor-associated proteins can, in turn, be phosphorylated by the RTK, an event which presumably regulates their activities. It has been suggested that SH2 domains in signal-transducing proteins target these proteins as substrates of the activated RTK. To test this hypothesis, recombinant proteins were generated that contained tyrosine phosphorylation sites of the erbB3 receptor and/or the SH2 domain of c-src. Incorporation of the SH2 domain led to a decrease in KM and an increase in Vmax for the substrate. The KM determined for one chimeric SH2/erbB3 substrate was among the lowest reported for epidermal growth factor RTK substrates. Experiments with a truncated kinase lacking C-terminal autophosphorylation sites indicated that the reduction in KM for these substrates was mediated by interactions between the substrate SH2 domain and phosphotyrosine residues of the RTK. These interactions could also inhibit RTK activity. These results demonstrate that the SH2 domain can effectively target substrates to a RTK and that SH2 domain proteins can regulate RTK activity.
authors.affiliation: Department of Pharmacology, The University of Iowa, Iowa City 52242-1109.
authors.forename: S L
authors.initials: SL
authors.lastname: Sierke
authors.forename: J G
authors.initials: JG
authors.lastname: Koland
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D002460:Cell Line; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D066246:ErbB Receptors / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D009036:Moths; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D011993:Recombinant Fusion Proteins; D013438:Sulfhydryl Compounds; C461599:maltose transport system, E coli; D005982:Glutathione Transferase; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src)