title: A nuclear export signal and phosphorylation regulate Dok1 subcellular localization and functions.
abstract: Dok1 is believed to be a mainly cytoplasmic adaptor protein which down-regulates mitogen-activated protein kinase activation, inhibits cell proliferation and transformation, and promotes cell spreading and cell migration. Here we show that Dok1 shuttles between the nucleus and cytoplasm. Treatment of cells with leptomycin B (LMB), a specific inhibitor of the nuclear export signal (NES)-dependent receptor CRM1, causes nuclear accumulation of Dok1. We have identified a functional NES (348LLKAKLTDPKED359) that plays a major role in the cytoplasmic localization of Dok1. Src-induced tyrosine phosphorylation prevented the LMB-mediated nuclear accumulation of Dok1. Dok1 cytoplasmic localization is also dependent on IKKbeta. Serum starvation or maintaining cells in suspension favor Dok1 nuclear localization, while serum stimulation, exposure to growth factor, or cell adhesion to a substrate induce cytoplasmic localization. Functionally, nuclear NES-mutant Dok1 had impaired ability to inhibit cell proliferation and to promote cell spreading and cell motility. Taken together, our results provide the first evidence that Dok1 transits through the nucleus and is actively exported into the cytoplasm by the CRM1 nuclear export system. Nuclear export modulated by external stimuli and phosphorylation may be a mechanism by which Dok1 is maintained in the cytoplasm and membrane, thus regulating its signaling functions.
authors.affiliation: Infections and Cancer Biology Group, International Agency for Research on Cancer, 150 cours Albert-Thomas, 69008 Lyon, France.
authors.forename: Yamei
authors.initials: Y
authors.lastname: Niu
authors.forename: François
authors.initials: F
authors.lastname: Roy
authors.forename: Frédéric
authors.initials: F
authors.lastname: Saltel
authors.forename: Charlotte
authors.initials: C
authors.lastname: Andrieu-Soler
authors.forename: Wen
authors.initials: W
authors.lastname: Dong
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Chantegrel
authors.forename: Rosita
authors.initials: R
authors.lastname: Accardi
authors.forename: Amélie
authors.initials: A
authors.lastname: Thépot
authors.forename: Nadège
authors.initials: N
authors.lastname: Foiselle
authors.forename: Massimo
authors.initials: M
authors.lastname: Tommasino
authors.forename: Pierre
authors.initials: P
authors.lastname: Jurdic
authors.forename: Bakary S
authors.initials: BS
authors.lastname: Sylla
mesh_terms: D021581:Active Transport, Cell Nucleus; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D051379:Mice; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D049790:Nuclear Export Signals / Q000502:physiology*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D041701:Swiss 3T3 Cells; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004268:DNA-Binding Proteins; C489561:Dok1 protein, mouse; D006133:Growth Substances; D049790:Nuclear Export Signals; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D019000:Phosphotyrosine; D019061:src-Family Kinases; D051550:I-kappa B Kinase