title: Tyrosine phosphorylation of Shc proteins and formation of Shc/Grb2 complex correlate to the transformation of NIH3T3 cells mediated by the point-mutation activated neu.
abstract: PLC-gamma, ras-GAP and Shc have been proposed to be in vivo substrates for the neu-encoded p185neu receptor tyrosine kinases. We compared the tyrosine phosphorylation levels of PLC-gamma, ras-GAP and Shc in two NIH3T3 derived cell lines, transformed B104-1-1 and non-transformed DHFR/G8 cells in which point-mutation activated and normal rat neu genes were transfected and expressed, respectively. We found that tyrosine phosphorylation of Shc and formation of Shc/Grb2 complex were more significant in B104-1-1 cells than in DHFR/G8 cells, while no obvious difference could be detected for the tyrosine phosphorylation levels of ras-GAP and PLC-gamma between these two cell lines. Furthermore, we observed that association with Shc was severely impaired by deletion of most of the major autophosphorylation sites of the point-mutated neu. The truncated neu product, however, fully retained its ability to transform NIH3T3 cells, induce Shc tyrosine phosphorylation and Shc/Grb2 complex formation. Our results suggest that tyrosine phosphorylation of Shc which allows formation of Shc/Grb2 complex may play an important role for cell transformation induced by the point mutation-activated neu, and that stable binding to mutant p185neu may not be necessary for Shc to mediate this signaling pathway.
authors.affiliation: University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Xie
authors.forename: K
authors.initials: K
authors.lastname: Li
authors.forename: M C
authors.initials: MC
authors.lastname: Hung
mesh_terms: D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D051380:GRB2 Adaptor Protein; D020690:GTPase-Activating Proteins; D051379:Mice; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D013379:Substrate Specificity; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; D020690:GTPase-Activating Proteins; D011506:Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D010738:Type C Phospholipases; D014443:Tyrosine; D020703:ras GTPase-Activating Proteins; C495949:Grb2 protein, mouse