title: Synergistic activities of multiple phosphotyrosine residues mediate full signaling from the Drosophila Torso receptor tyrosine kinase.
abstract: Here, we identify four tyrosine residues (Y644, Y698, Y767, and Y772) that become phosphorylated after activation of the Torso (Tor) receptor tyrosine kinase. Previously, we characterized phosphotyrosine sites (P-Y630 and P-Y918). Of the six P-Y sites identified, three (Y630, Y644, and Y698) are located in the kinase domain insert region, one (Y918) is located in the C-terminal tail region, and two (Y767 and Y772) are located in the activation loop of the kinase domain. To investigate the function of each P-Y residue in Tor signaling, we have generated transgenic Drosophila embryos expressing mutant Tor receptors containing either single or multiple tyrosine to phenylalanine substitutions. Single P-Y mutations were found to have either positive, negative, or no effect on the signaling activity of the receptor. Elimination of all P-Y sites within the kinase insert region resulted in the complete loss of receptor function, indicating that some combination of these sites is necessary for Tor signaling. Mutation of the C-terminal P-Y918 site revealed that this site is responsible for negative signaling or down-regulation of receptor activity. Mutation of the P-Y sites in the kinase domain activation loop demonstrated that these sites are essential for enzymatic activity. Our analysis provides a detailed in vivo example of the extent of cooperativity between P-Y residues in transducing the signal received by a receptor tyrosine kinase and in vivo data demonstrating the function of P-Y residues in the activation loop of the kinase domain.
authors.affiliation: Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: U
authors.initials: U
authors.lastname: Gayko
authors.forename: V
authors.initials: V
authors.lastname: Cleghon
authors.forename: T
authors.initials: T
authors.lastname: Copeland
authors.forename: D K
authors.initials: DK
authors.lastname: Morrison
authors.forename: N
authors.initials: N
authors.lastname: Perrimon
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D047108:Embryonic Development; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010748:Phosphopeptides / Q000032:analysis; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000235:genetics / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D013329:Structure-Activity Relationship
chemical_list: D029721:Drosophila Proteins; D019476:Insect Proteins; D010748:Phosphopeptides; D011994:Recombinant Proteins; D019000:Phosphotyrosine; D020794:Receptor Protein-Tyrosine Kinases; C080148:tor protein, Drosophila