title: Endoplasmic reticulum stress and unfolded protein response in Atm-deficient thymocytes and thymic lymphoma cells are attributable to oxidative stress.
abstract: Both oxidative stress and endoplasmic reticulum (ER) stress have been implicated in carcinogenesis. It is well documented that cells deficient in the ataxia-telangiectasia mutated (ATM) gene undergo oxidative stress, which is critically involved in thymic lymphomagenesis in Atm-/- mice. Here we demonstrate that undifferentiated Atm-/- thymocytes show signs of ER stress and of the unfolded protein response (UPR). Using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis, we identified 22 differentially expressed proteins, including the ER stress marker glucose-regulated protein 78 (GRP78), in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells relative to Atm+/+ thymocytes. The phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2alpha), a UPR marker, was also increased in Atm-/- thymocytes. Cells of the ATL-1 line, which were derived from an Atm-/- mouse thymic lymphoma, were more sensitive to the ER stress inducer tunicamycin than were Atm+/+ thymic leukemia ASL-1 cells. Notably, treatment with hydrogen peroxide duplicated the effects of ATM deficiency in cultured thymocytes, and treatment with the novel cell-permeable thiol antioxidant N-acetylcysteine amide (AD4) reduced elevated p-eIF2alpha levels in thymocytes of Atm-/- mice. Thus, we propose that ER stress and the UPR are secondary to oxidative stress in Atm-/- thymocytes.
authors.affiliation: Department of Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, TX 78957, USA. mingyan@mdanderson.org
authors.forename: Mingshan
authors.initials: M
authors.lastname: Yan
authors.forename: Jianjun
authors.initials: J
authors.lastname: Shen
authors.forename: Maria D
authors.initials: MD
authors.lastname: Person
authors.forename: Xianghong
authors.initials: X
authors.lastname: Kuang
authors.forename: William S
authors.initials: WS
authors.lastname: Lynn
authors.forename: Daphne
authors.initials: D
authors.lastname: Atlas
authors.forename: Paul K Y
authors.initials: PK
authors.lastname: Wong
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D053148:Caspase 3 / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D018832:Molecular Chaperones / Q000378:metabolism; D018384:Oxidative Stress; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency* / Q000235:genetics; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D013953:Thymus Neoplasms / Q000378:metabolism* / Q000473:pathology; D025521:Tumor Suppressor Proteins / Q000172:deficiency* / Q000235:genetics; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008565:Membrane Proteins; D018832:Molecular Chaperones; D025521:Tumor Suppressor Proteins; C018551:glucose-regulated proteins; D014415:Tunicamycin; D006861:Hydrogen Peroxide; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases; D053148:Caspase 3