title: Phosphorylation of Dok1 by Abl family kinases inhibits CrkI transforming activity.
abstract: The Crk SH2/SH3 adaptor and the Abl nonreceptor tyrosine kinase were first identified as oncoproteins, and both can induce tumorigenesis when overexpressed or mutationally activated. We previously reported the surprising finding that inhibition or knockdown of Abl family kinases enhanced transformation of mouse fibroblasts by CrkI. Abl family inhibitors are currently used or are being tested for treatment of human malignancies, and our finding raised concerns that such inhibitors might actually promote the growth of tumors overexpressing CrkI. Here, we identify the Dok1 adaptor as the key effector for the enhancement of CrkI transformation by Abl inhibition. We show that phosphorylation of tyrosines 295 and 361 of Dok1 by Abl family kinases suppresses CrkI transforming activity, and that upon phosphorylation these tyrosines bind the SH2 domains of the Ras inhibitor p120 RasGAP. Knockdown of RasGAP resulted in a similar enhancement of CrkI transformation, consistent with a critical role for Ras activity. Imaging studies using a FRET sensor of Ras activation revealed alterations in the localization of activated Ras in CrkI-transformed cells. Our results support a model in which Dok1 phosphorylation normally suppresses localized Ras pathway activity in Crk-transformed cells via recruitment and/or activation of RasGAP, and that preventing this negative feedback mechanism by inhibiting Abl family kinases leads to enhanced transformation by Crk.
authors.affiliation: Raymond and Beverly Sackler Laboratory of Genetics and Molecular Medicine, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: K Y
authors.initials: KY
authors.lastname: Ng
authors.affiliation: Richard D. Berlin Center for Cell Analysis and Modeling, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: T
authors.initials: T
authors.lastname: Yin
authors.affiliation: Raymond and Beverly Sackler Laboratory of Genetics and Molecular Medicine, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: K
authors.initials: K
authors.lastname: Machida
authors.affiliation: Richard D. Berlin Center for Cell Analysis and Modeling, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: Y I
authors.initials: YI
authors.lastname: Wu
authors.affiliation: 1] Raymond and Beverly Sackler Laboratory of Genetics and Molecular Medicine, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA [2] Richard D. Berlin Center for Cell Analysis and Modeling, Department of Genetics and Developmental Biology, University of Connecticut Health Center, Farmington, CT, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Mayer
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016315:Proto-Oncogene Proteins c-abl / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020729:p120 GTPase Activating Protein / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C489561:Dok1 protein, mouse; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D050737:Proto-Oncogene Proteins c-crk; D016601:RNA-Binding Proteins; D020729:p120 GTPase Activating Protein; D016315:Proto-Oncogene Proteins c-abl; D018631:ras Proteins