title: Disulfide bond as a switch for copper-zinc superoxide dismutase activity in asthma.
abstract: OBJECTIVE
  Loss of superoxide dismutase (SOD) activity is a defining biochemical feature of asthma. However, mechanisms for the reduced activity are unknown. We hypothesized that loss of asthmatic SOD activity is due to greater susceptibility to oxidative inactivation.
  
  
  RESULTS
  Activity assays of blood samples from asthmatics and healthy controls revealed impaired dismutase activity of copper-zinc SOD (CuZnSOD) in asthma. CuZnSOD purified from erythrocytes or airway epithelial cells from asthmatic was highly susceptible to oxidative inactivation. Proteomic analyses identified that inactivation was related to oxidation of cysteine 146 (C146), which is usually disulfide bonded to C57. The susceptibility of cysteines pointed to an alteration in protein structure, which is likely related to the loss of disulfide bond. We speculated that a shift to greater intracellular reducing potential might account for the change. Strikingly, measures of reduced and oxidized glutathione confirmed greater reducing intracellular state in asthma, compared with controls. Similarly, greater free thiol in CuZnSOD was confirmed by ~2-fold greater N-ethylmaleimide binding to C146 in asthma as compared with controls.
  
  
  METHODS
  Greater reducing potential under a chronic inflammatory state of asthma, thus, leads to susceptibility of CuZnSOD to oxidative inactivation due to cleavage of C57-C146 disulfide bond and exposure of usually unavailable cysteines.
  
  
  CONCLUSIONS
  Vulnerability of CuZnSOD influenced by redox likely amplifies injury and inflammation during acute asthma attacks when reactive oxygen species are explosively generated. Overall, this study identifies a new paradigm for understanding the chemical basis of inflammation, in which redox regulation of thiol availability dictates protein susceptibility to environmental and endogenously generated reactive species.
authors.affiliation: Department of Pathobiology, Lerner Research Institute, Cleveland, OH 44195, USA.
authors.forename: Sudakshina
authors.initials: S
authors.lastname: Ghosh
authors.forename: Belinda
authors.initials: B
authors.lastname: Willard
authors.forename: Suzy A A
authors.initials: SA
authors.lastname: Comhair
authors.forename: Patricia
authors.initials: P
authors.lastname: Dibello
authors.forename: Weiling
authors.initials: W
authors.lastname: Xu
authors.forename: Sruti
authors.initials: S
authors.lastname: Shiva
authors.forename: Kulwant S
authors.initials: KS
authors.lastname: Aulak
authors.forename: Michael
authors.initials: M
authors.lastname: Kinter
authors.forename: Serpil C
authors.initials: SC
authors.lastname: Erzurum
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D001249:Asthma / Q000097:blood* / Q000201:enzymology; D001792:Blood Platelets / Q000201:enzymology; D016022:Case-Control Studies; D003553:Cystine / Q000737:chemistry*; D004229:Dithiothreitol / Q000737:chemistry; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D008297:Male; D008969:Molecular Sequence Data; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010446:Peptide Fragments / Q000737:chemistry; D019163:Reducing Agents / Q000737:chemistry; D013482:Superoxide Dismutase / Q000097:blood* / Q000737:chemistry
chemical_list: D016877:Oxidants; D010446:Peptide Fragments; D019163:Reducing Agents; D003553:Cystine; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D005978:Glutathione; D004229:Dithiothreitol