title: Hydrogen peroxide inhibition of nuclear protein import is mediated by the mitogen-activated protein kinase, ERK2.
abstract: H(2)O(2) alters gene expression in many cell types. Alterations in nuclear import of transcription factors or similar key proteins may be responsible for these changes. To investigate this possibility, a cytosolic nuclear import cocktail was treated with varying ¿H(2)O(2) and used in import assays. H(2)O(2) caused a dose- and time-dependent inhibition of import at concentrations as low as 100 microM. Catalase reversed this effect. H(2)O(2) treatment of permeablized cells did not affect import, suggesting that H(2)O(2) was acting on a cytosolic factor. Treatment of import cocktail with two different free radical generating systems had no effect, but treatment of permeablized cells inhibited import, suggesting H(2)O(2) works via a distinct process from hydroxyl or superoxide radicals. Pretreatment of import cocktail with genistein reversed the effect of H(2)O(2) on import. Western blotting revealed that H(2)O(2) activated ERK2. The specific MEK1/2 inhibitor, PD98059, completely blocked the effects of H(2)O(2) on import. Activated ERK2 mimicked H(2)O(2)'s effect on import. Immunocytochemistry revealed that H(2)O(2) treatment of whole cells increased cytosolic Ran/TC4 levels, an effect reversible by catalase or PD98059. These data demonstrate that H(2)O(2) inhibits nuclear protein import and that this effect is mediated by mitogen-activated protein (MAP) kinase activation, possibly by altering Ran/TC4 function.
authors.affiliation: Cell Biology Laboratory, Division of Stroke and Vascular Disease, St. Boniface General Hospital Research Centre and the Department of Physiology, University of Manitoba, Winnipeg, Manitoba, Canada R2H 2A6.
authors.forename: M P
authors.initials: MP
authors.lastname: Czubryt
authors.forename: J A
authors.initials: JA
authors.lastname: Austria
authors.forename: G N
authors.initials: GN
authors.lastname: Pierce
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001896:Boron Compounds / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D005456:Fluorescent Dyes / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D009687:Nuclear Proteins / Q000378:metabolism*; D010084:Oxidation-Reduction; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D005456:Fluorescent Dyes; D009687:Nuclear Proteins; D013481:Superoxides; D012710:Serum Albumin, Bovine; D006861:Hydrogen Peroxide; D019950:Mitogen-Activated Protein Kinase 1; D020931:ran GTP-Binding Protein