title: Bicarbonate enhances alpha-synuclein oligomerization and nitration: intermediacy of carbonate radical anion and nitrogen dioxide radical.
abstract: alpha-Synuclein, a neuronal presynaptic protein, has been reported to undergo oligomerization to form toxic Lewy bodies in neurodegenerative disorders. One of the proposed mechanisms for aggregation of alpha-synuclein involves oxidative and nitrative modifications. In the present study, we show that addition of 3-morpholino-sydnonimine chloride (SIN-1) or slow infusion of pre-formed peroxynitrite (ONOO-) to mixtures containing alpha-synuclein and HCO3- markedly enhanced both nitration and aggregation of alpha-synuclein through dityrosine formation. Bicarbonate-dependent peroxidase activity of Cu,Zn-superoxide dismutase (SOD1) also induced covalent aggregation of alpha-synuclein via a CO3*--dependent mechanism. Nitrone spin traps completely inhibited CO3*--mediated oxidation/nitration and aggregation of alpha-synuclein. Conversely, alpha-synuclein inhibited CO3*--induced spin adduct formation. Independent evidence for CO3*--mediated oxidation and dimerization of alpha-synuclein was obtained from UV photolysis of [(NH3)5CoCO3]+, which generates authentic CO3*-. Irradiation of [(NH3)5CoCO3]+ and NO2- in the presence of alpha-synuclein yielded nitration and aggregation products that were similar to those obtained from a SIN-1 (or slowly infused ONOO-) and HCO3- or a myeloperoxidase/H2O2/NO2- system. Hydrophobic membranes greatly influenced alpha-synuclein aggregation and nitration in these systems. We conclude that both CO3*- and NO2* could play a major role in the nitration/aggregation of alpha-synuclein.
authors.affiliation: Department of Biophysics, Free Radical Research Center, Medical College of Wisconsin, 8701 Watertown Plank Road, P.O. Box 26509, Milwaukee, WI 53226, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Andrekopoulos
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Joy
authors.initials: J
authors.lastname: Joseph
authors.forename: Shasi
authors.initials: S
authors.lastname: Kalivendi
authors.forename: B
authors.initials: B
authors.lastname: Kalyanaraman
mesh_terms: D000838:Anions / Q000737:chemistry / Q000494:pharmacology; D001639:Bicarbonates / Q000737:chemistry* / Q000494:pharmacology*; D003497:Cyclic N-Oxides; D019281:Dimerization; D005609:Free Radicals / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D006900:Hydroxylation; D008081:Liposomes; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009585:Nitrogen Dioxide / Q000737:chemistry* / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000737:chemistry; D010084:Oxidation-Reduction / Q000187:drug effects; D009195:Peroxidase / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000494:pharmacology; D026361:Reactive Nitrogen Species / Q000737:chemistry / Q000378:metabolism*; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D051843:Synucleins; D014443:Tyrosine / Q000737:chemistry; D051844:alpha-Synuclein
chemical_list: D000838:Anions; D001639:Bicarbonates; D003497:Cyclic N-Oxides; D005609:Free Radicals; D008081:Liposomes; D009419:Nerve Tissue Proteins; D020030:Nitric Oxide Donors; D009589:Nitrogen Oxides; D026361:Reactive Nitrogen Species; D013113:Spin Labels; D051843:Synucleins; D051844:alpha-Synuclein; D030421:Peroxynitrous Acid; C029217:phenyl-N-tert-butylnitrone; D014443:Tyrosine; D006861:Hydrogen Peroxide; D009195:Peroxidase; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D009585:Nitrogen Dioxide