title: Nuclear localization of Lyn tyrosine kinase mediated by inhibition of its kinase activity.
abstract: Src-family kinases, cytoplasmic enzymes that participate in various signaling events, are found at not only the plasma membrane but also subcellular compartments, such as the nucleus, the Golgi apparatus and late endosomes/lysosomes. Lyn, a member of the Src-family kinases, is known to play a role in DNA damage response and cell cycle control in the nucleus. However, it is still unclear how the localization of Lyn to the nucleus is regulated. Here, we investigated the mechanism of the distribution of Lyn between the cytoplasm and the nucleus in epitheloid HeLa cells and hematopoietic THP-1 cells. Lyn was definitely detected in purified nuclei by immunofluorescence and immunoblotting analyses. Nuclear accumulation of Lyn was enhanced upon treatment of cells with leptomycin B (LMB), an inhibitor of Crm1-mediated nuclear export. Moreover, Lyn mutants lacking the sites for lipid modification were highly accumulated in the nucleus upon LMB treatment. Intriguingly, inhibition of the kinase activity of Lyn by SU6656, Csk overexpression, or point mutation in the ATP-binding site induced an increase in nuclear Lyn levels. These results suggest that Lyn being imported into and rapidly exported from the nucleus preferentially accumulates in the nucleus by inhibition of the kinase activity and lipid modification.
authors.affiliation: Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675, Japan.
authors.forename: Kikuko
authors.initials: K
authors.lastname: Ikeda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Togashi
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Obata
authors.forename: Takahisa
authors.initials: T
authors.lastname: Kuga
authors.forename: Kousuke
authors.initials: K
authors.lastname: Kasahara
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Fukumoto
authors.forename: Naoto
authors.initials: N
authors.lastname: Yamaguchi
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology*; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D003593:Cytoplasm / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D009154:Mutation; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; C038753:leptomycin B