title: Oxidative stress-induced modifications of histidyl-tRNA synthetase affect its tRNA aminoacylation activity but not its immunoreactivity.
abstract: The aminoacyl-tRNA synthetases are ubiquitously expressed enzymes that catalyze the esterification of amino acids to their cognate tRNAs. Autoantibodies against several aminoacyl-tRNA synthetases are found in autoimmune polymyositis and dermatomyositis patients. Because necrosis is often found in skeletal muscle biopsies of these patients, we hypothesized that cell-death-induced protein modifications may help in breaking immunological tolerance. Since cell death is associated with oxidative stress, the effect of oxidative stress on the main myositis-specific autoantibody target Jo-1 (histidyl-tRNA synthetase; HisRS) was studied in detail. The exposure of Jurkat cells to hydrogen peroxide resulted in the detection of several oxidized methionines and one oxidized tryptophan residue in the HisRS protein, as demonstrated by mass spectrometry. Unexpectedly, the tRNA aminoacylation activity of HisRS appeared to be increased upon oxidative modification. The analysis of myositis patient sera did not lead to the detection of autoantibodies that are specifically reactive with the modified HisRS protein. The results of this study demonstrate that the Jo-1/HisRS autoantigen is modified under oxidative stress conditions. The consequences of these modifications for the function of HisRS and its autoantigenicity are discussed.
authors: Department of Biomolecular Chemistry, Institute for Molecules and Materials, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, 271 Department of Biomolecular Chemistry, NL-6500 HB Nijmegen, The Netherlands.
authors: Sander H J
authors: SH
authors: van Dooren
authors: Reinout
authors: R
authors: Raijmakers
authors: Helma
authors: H
authors: Pluk
authors: Angelique M C
authors: AM
authors: Lokate
authors: Tom S
authors: TS
authors: Koemans
authors: Richelle E C
authors: RE
authors: Spanjers
authors: Albert J R
authors: AJ
authors: Heck
authors: Wilbert C
authors: WC
authors: Boelens
authors: Walther J
authors: WJ
authors: van Venrooij
authors: Ger J M
authors: GJ
authors: Pruijn
mesh_terms: D000595:Amino Acid Sequence; D000918:Antibody Specificity; D017209:Apoptosis; D001323:Autoantibodies / Q000097:blood / Q000378:metabolism; D003882:Dermatomyositis / Q000097:blood / Q000276:immunology; D004789:Enzyme Activation; D006643:Histidine-tRNA Ligase / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D019169:Jurkat Cells; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D017285:Polymyositis / Q000097:blood / Q000276:immunology; D053719:Tandem Mass Spectrometry; D046249:Transfer RNA Aminoacylation; D014364:Tryptophan / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D014364:Tryptophan; D008715:Methionine; D006861:Hydrogen Peroxide; D006643:Histidine-tRNA Ligase