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Bernard Moussian - One of the best experts on this subject based on the ideXlab platform.
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The putative C-type lectin Schlaff ensures epidermal barrier compactness in Drosophila.
Scientific reports, 2019Co-Authors: Renata Zuber, Khaleelulla Saheb Shaik, Frauke Meyer, Anna Speidel, Nicole Gehring, Slawomir Bartoszewski, Heinz Schwarz, Bernard MoussianAbstract:The stability of extracellular matrices is in general ensured by cross-linking of its components. Previously, we had shown that the integrity of the layered Drosophila cuticle relies on the presence of a covalent cuticular Dityrosine network. Production and composition of this structure remained unstudied. In this work, we present our analyses of the schlaff (slf) gene coding for a putative C-type lectin that is needed for the adhesion between the horizontal cuticle layers. The Slf protein mainly localizes between the two layers called epicuticle and procuticle that separate from each other when the function of Slf is reduced or eliminated paralleling the phenotype of a cuticle with reduced extracellular Dityrosine. Localisation of the dityrosinylated protein Resilin to the epicuticle-procuticle interface suggests that the Dityrosine network mediates the adhesion of the epicuticle to the procuticle. Ultimately, compromised Slf function is associated with massive water loss. In summary, we propose that Slf is implied in the stabilisation of a Dityrosine layer especially between the epicuticle and the procuticle that in turn constitutes an outward barrier against uncontrolled water flow.
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The C-type lectin Schlaff ensures epidermal barrier compactness in Drosophila
2018Co-Authors: Renata Zuber, Khaleelulla Saheb Shaik, Frauke Meyer, Anna Speidel, Nicole Gehring, Slawomir Bartoszewski, Heinz Schwarz, Bernard MoussianAbstract:The stability of extracellular matrices is in general ensured by cross-linking of its components. Previously, we had shown that the integrity of the layered Drosophila cuticle relies on the presence of a covalent cuticular Dityrosine network. Production and composition of this structure remained unstudied. In this work, we present our analyses of the schlaff (slf) gene coding for a C-type lectin that is needed for the adhesion between the horizontal cuticle layers. The Slf protein mainly localizes between the two layers called epicuticle and procuticle that separate from each other when the function of Slf is reduced or eliminated paralleling the phenotype of a cuticle with reduced extracellular Dityrosine. Localisation of the dityrosinylated protein Resilin to the epicuticle-procuticle interface suggests that the Dityrosine network mediates the adhesion of the epicuticle to the procuticle. Ultimately, compromised Slf function is associated with massive water loss. In summary, we propose that Slf is implied in the stabilisation of a Dityrosine layer especially between the epicuticle and the procuticle that in turn constitutes an outward barrier against uncontrolled water flow.
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δ aminolevulinate synthase is required for apical transcellular barrier formation in the skin of the drosophila larva
European Journal of Cell Biology, 2012Co-Authors: Khaleelulla Saheb Shaik, Frauke Meyer, Angel Vizoso Vazquez, Matthias Flotenmeyer, Maria Esperanza Cerdan, Bernard MoussianAbstract:Abstract Animals construct a layered skin to prevent dehydration and pathogen entrance. The barrier function of the skin relies on the extensive cross-linking of specialised components. In insects, for instance, epidermal cells produce an apical extracellular cuticle that consists of a network of proteins, chitin and lipids. We have identified mutations in the Drosophila gene coding for the δ-aminolevulinate synthase (Alas) that cause massive water loss. The cuticle of alas mutant larvae detaches from the epidermis and its basal region is frayed suggesting that an Alas dependent pathway is needed to organise the contact between the cuticle and the epidermis and anchor the cuticle to the apical surface of epidermal cells. Concomitantly, reduction of Alas function results in weakening of the extracellular Dityrosines network in the cuticle, whereas glutamyl–lysine isopeptide bonds are not affected. The lateral septate junctions of epidermal cells that serve as a paracellular plug are intact, as well. Taken together, we hypothesise that Alas activity, which initiates heme biosynthesis in the mitochondrion, is needed for the formation of a Dityrosine-based barrier that confers resistance to the internal hydrostatic pressure protecting both the cuticle from transcellular infiltration of body fluid and the animal from dehydration. We conclude that at least two modules – an apical protein–chitin lattice and the lateral septate junctions, act in parallel to ensure Drosophila skin impermeability.
Jay W Heinecke - One of the best experts on this subject based on the ideXlab platform.
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Rapid Publication Tyrosyl Radical Generated by Myeloperoxidase Catalyzes the Oxidative Cross-linking of Proteins
2016Co-Authors: Jay W Heinecke, Gordon A. Francis, Jeffrey A GoldsteinAbstract:Phagocytes generate H202 for use by a secreted heme enzyme, myeloperoxidase, to kill invading bacteria, viruses, and fungi. We have explored the possibility that myeloperoxidase might also convert L-tyrosine to a radical catalyst that cross-links proteins. Protein-bound tyrosyl residues exposed to myeloper-oxidase, H202, and L-tyrosine were oxidized to oo'-Dityrosine, a stable product of the tyrosyl radical. The cross-linking reac-tion required L-tyrosine but was independent of halide and free transition metal ions; the heme poisons azide and aminotriazole were inhibitory. Activated neutrophils likewise converted poly-peptide tyrosines to Dityrosine. The pathway for oxidation of peptide tyrosyl residues was dependent upon L-tyrosine and was inhibited by heme poisons and catalase. Dityrosine synthe-sis was little affected by plasma concentrations of Cl- and amino acids, suggesting that the reaction pathway might be physiologically relevant. The requirement for free L-tyrosine and H202 for Dityrosine formation and the inhibition by heme poisons support the hypothesis that myeloperoxidase catalyzes the cross-linking of proteins by a peroxidative mechanism in-volving tyrosyl radical. In striking contrast to the pathways generally used to study protein oxidation in vitro, the reaction does not require free metal ions. We speculate that protein Dityrosine cross-linking by myeloperoxidase may play a role in bacterial killing or injuring normal tissue. The intense fluores-cence and stability of biphenolic compounds may allow dityro-sine to act as a marker for proteins oxidatively damaged by myeloperoxidase in phagocyte-rich inflammatory lesions. (J. Clin. Invest. 1993. 91:2866-2872.) Key words: Dityrosine. heme protein * neutrophil * phenoxyl radical- protein oxidatio
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a hydroxyl radical like species oxidizes cynomolgus monkey artery wall proteins in early diabetic vascular disease
Journal of Clinical Investigation, 2001Co-Authors: Subramaniam Pennathur, Janice D Wagner, Christiaan Leeuwenburgh, K N Litwak, Jay W HeineckeAbstract:Recent evidence argues strongly that the marked increase in risk for atherosclerotic heart disease seen in diabetics cannot be explained by a generalized increase in oxidative stress. Here, we used streptozotocin to induce hyperglycemia in cynomolgus monkeys for 6 months and tested whether high glucose levels promote localized oxidative damage to artery wall proteins. We focused on three potential agents of oxidative damage: hydroxyl radical, tyrosyl radical, and reactive nitrogen species. To determine which pathways operate in vivo, we quantified four stable end products of these reactants -- ortho-tyrosine, meta-tyrosine, o,o'-Dityrosine, and 3-nitrotyrosine -- in aortic proteins. Levels of ortho-tyrosine, meta-tyrosine, and o,o'-Dityrosine, but not of 3-nitrotyrosine, were significantly higher in aortic tissue of hyperglycemic animals. Of the oxidative agents we tested, only hydroxyl radical mimicked this pattern of oxidized amino acids. Moreover, tissue levels of ortho-tyrosine and meta-tyrosine correlated strongly with serum levels of glycated hemoglobin, a measure of glycemic control. We conclude that short-term hyperglycemia in primates promotes oxidation of artery wall proteins by a species that resembles hydroxyl radical. Our observations suggest that glycoxidation reactions in the arterial microenvironment contribute to early diabetic vascular disease, raising the possibility that antioxidant therapies might interrupt this process.
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mass spectrometric quantification of 3 nitrotyrosine ortho tyrosine and o o Dityrosine in brain tissue of 1 methyl 4 phenyl 1 2 3 6 tetrahydropyridine treated mice a model of oxidative stress in parkinson s disease
Journal of Biological Chemistry, 1999Co-Authors: Subramaniam Pennathur, Vernice Jacksonlewis, Serge Przedborski, Jay W HeineckeAbstract:Oxidative stress is implicated in the death of dopaminergic neurons in Parkinson's disease and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease. Oxidative species that might mediate this damage include hydroxyl radical, tyrosyl radical, or reactive nitrogen species such as peroxynitrite. In mice, we showed that MPTP markedly increased levels of o,o′-Dityrosine and 3-nitrotyrosine in the striatum and midbrain but not in brain regions resistant to MPTP. These two stable compounds indicate that tyrosyl radical and reactive nitrogen species have attacked tyrosine residues. In contrast, MPTP failed to alter levels of ortho-tyrosine in any brain region we studied. This marker accumulates when hydroxyl radical oxidizes protein-bound phenylalanine residues. We also showed that treating whole-brain proteins with hydroxyl radical markedly increased levels of ortho-tyrosine in vitro. Under identical conditions, tyrosyl radical, produced by the heme protein myeloperoxidase, selectively increased levels ofo,o′-Dityrosine, whereas peroxynitrite increased levels of 3-nitrotyrosine and, to a lesser extent, of ortho-tyrosine. These in vivo and in vitro findings implicate reactive nitrogen species and tyrosyl radical in MPTP neurotoxicity but argue against a deleterious role for hydroxyl radical in this model. They also show that reactive nitrogen species and tyrosyl radical (and consequently protein oxidation) represent an early and previously unidentified biochemical event in MPTP-induced brain injury. This finding may be significant for understanding the pathogenesis of Parkinson's disease and developing neuroprotective therapies.
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mass spectrometric quantification of markers for protein oxidation by tyrosyl radical copper and hydroxyl radical in low density lipoprotein isolated from human atherosclerotic plaques
Journal of Biological Chemistry, 1997Co-Authors: Christiaan Leeuwenburgh, Dianne M Mueller, Subramaniam Pennathur, Jane E Rasmussen, Fongfu Hsu, Jay W HeineckeAbstract:Lipoprotein oxidation has been implicated in the pathogenesis of atherosclerosis. However, the physiologically relevant pathways mediating oxidative damage have not yet been identified. Three potential mechanisms are tyrosyl radical, hydroxyl radical, and redox active metal ions. Tyrosyl radical forms o,o′-Dityrosine cross-links in proteins. The highly reactive hydroxyl radical oxidizes phenylalanine residues to o-tyrosine and m-tyrosine. Metal ions oxidize low density lipoprotein (LDL) by poorly understood pathways. To explore the involvement of tyrosyl radical, hydroxyl radical, and metal ions in atherosclerosis, we developed a highly sensitive and quantitative method for measuring levels of o,o′-Dityrosine, o-tyrosine, and m-tyrosine in proteins, lipoproteins, and tissue, using stable isotope dilution gas chromatography-mass spectrometry. We showed that o,o′-Dityrosine was selectively produced in LDL oxidized with tyrosyl radical. Both o-tyrosine and o,o′-Dityrosine were major products when LDL was oxidized with hydroxyl radical. Only o-tyrosine was formed in LDL oxidized with copper. Similar profiles of oxidation products were observed in bovine serum albumin oxidized with the three different systems. Applying these findings to LDL isolated from human atherosclerotic lesions, we detected a 100-fold increase in o,o′-Dityrosine levels compared to those in circulating LDL. In striking contrast, levels of o-tyrosine and m-tyrosine were not elevated in LDL isolated from atherosclerotic tissue. Analysis of fatty streaks revealed a similar pattern of oxidation products; compared with normal aortic tissue, there was a selective increase in o,o′-Dityrosine with no change in o-tyrosine. The detection of a selective increase of o,o′-Dityrosine in LDL isolated from vascular lesions is consistent with the hypothesis that oxidative damage in human atherosclerosis is mediated in part by tyrosyl radical. In contrast, these observations do not support a role for free metal ions as catalysts of LDL oxidation in the artery wall.
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tyrosyl radical generated by myeloperoxidase is a physiological catalyst for the initiation of lipid peroxidation in low density lipoprotein
Journal of Biological Chemistry, 1994Co-Authors: Marina I Savenkova, Dianne M Mueller, Jay W HeineckeAbstract:Abstract Myeloperoxidase, a heme protein secreted by activated phagocytes, is expressed in human atherosclerotic lesions. The enzyme uses H2O2 generated by the cells to oxidize L-tyrosine to tyrosyl radical, a catalyst for protein Dityrosine synthesis. We have explored the possibility that tyrosyl radical initiates lipid peroxidation, which may be of pivotal importance in transforming low density lipoprotein (LDL) into atherogenic particles. Exposure of LDL to L-tyrosine and activated human neutrophils caused peroxidation of LDL lipids. LDL oxidation required L-tyrosine but was independent of free metal ions; catalase and heme poisons were inhibitory. Incubation of LDL with L-tyrosine, myeloperoxidase, and H2O2 likewise caused lipid peroxidation, and this reaction was inhibited by heme poisons and catalase. Replacement of L-tyrosine with O-methyltyrosine, which cannot form tyrosyl radical, inhibited LDL oxidation by both activated neutrophils and myeloperoxidase. The antioxidants ascorbate and probucol, but not vitamin E, inhibited LDL oxidation by myeloperoxidase, H2O2, and L-tyrosine. Ascorbate blocked Dityrosine synthesis, while probucol scavenged chain-propagating peroxyl radicals in the lipid phase of LDL. These results indicate that tyrosyl radical stimulates LDL lipid peroxidation. In striking contrast to other cell-mediated mechanisms for LDL oxidation, the myeloperoxidase-catalyzed reaction is independent of free metal ions. This raises the possibility that tyrosyl radical generated by myeloperoxidase is of physiological importance in making LDL atherogenic.
Khaleelulla Saheb Shaik - One of the best experts on this subject based on the ideXlab platform.
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The putative C-type lectin Schlaff ensures epidermal barrier compactness in Drosophila.
Scientific reports, 2019Co-Authors: Renata Zuber, Khaleelulla Saheb Shaik, Frauke Meyer, Anna Speidel, Nicole Gehring, Slawomir Bartoszewski, Heinz Schwarz, Bernard MoussianAbstract:The stability of extracellular matrices is in general ensured by cross-linking of its components. Previously, we had shown that the integrity of the layered Drosophila cuticle relies on the presence of a covalent cuticular Dityrosine network. Production and composition of this structure remained unstudied. In this work, we present our analyses of the schlaff (slf) gene coding for a putative C-type lectin that is needed for the adhesion between the horizontal cuticle layers. The Slf protein mainly localizes between the two layers called epicuticle and procuticle that separate from each other when the function of Slf is reduced or eliminated paralleling the phenotype of a cuticle with reduced extracellular Dityrosine. Localisation of the dityrosinylated protein Resilin to the epicuticle-procuticle interface suggests that the Dityrosine network mediates the adhesion of the epicuticle to the procuticle. Ultimately, compromised Slf function is associated with massive water loss. In summary, we propose that Slf is implied in the stabilisation of a Dityrosine layer especially between the epicuticle and the procuticle that in turn constitutes an outward barrier against uncontrolled water flow.
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The C-type lectin Schlaff ensures epidermal barrier compactness in Drosophila
2018Co-Authors: Renata Zuber, Khaleelulla Saheb Shaik, Frauke Meyer, Anna Speidel, Nicole Gehring, Slawomir Bartoszewski, Heinz Schwarz, Bernard MoussianAbstract:The stability of extracellular matrices is in general ensured by cross-linking of its components. Previously, we had shown that the integrity of the layered Drosophila cuticle relies on the presence of a covalent cuticular Dityrosine network. Production and composition of this structure remained unstudied. In this work, we present our analyses of the schlaff (slf) gene coding for a C-type lectin that is needed for the adhesion between the horizontal cuticle layers. The Slf protein mainly localizes between the two layers called epicuticle and procuticle that separate from each other when the function of Slf is reduced or eliminated paralleling the phenotype of a cuticle with reduced extracellular Dityrosine. Localisation of the dityrosinylated protein Resilin to the epicuticle-procuticle interface suggests that the Dityrosine network mediates the adhesion of the epicuticle to the procuticle. Ultimately, compromised Slf function is associated with massive water loss. In summary, we propose that Slf is implied in the stabilisation of a Dityrosine layer especially between the epicuticle and the procuticle that in turn constitutes an outward barrier against uncontrolled water flow.
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δ aminolevulinate synthase is required for apical transcellular barrier formation in the skin of the drosophila larva
European Journal of Cell Biology, 2012Co-Authors: Khaleelulla Saheb Shaik, Frauke Meyer, Angel Vizoso Vazquez, Matthias Flotenmeyer, Maria Esperanza Cerdan, Bernard MoussianAbstract:Abstract Animals construct a layered skin to prevent dehydration and pathogen entrance. The barrier function of the skin relies on the extensive cross-linking of specialised components. In insects, for instance, epidermal cells produce an apical extracellular cuticle that consists of a network of proteins, chitin and lipids. We have identified mutations in the Drosophila gene coding for the δ-aminolevulinate synthase (Alas) that cause massive water loss. The cuticle of alas mutant larvae detaches from the epidermis and its basal region is frayed suggesting that an Alas dependent pathway is needed to organise the contact between the cuticle and the epidermis and anchor the cuticle to the apical surface of epidermal cells. Concomitantly, reduction of Alas function results in weakening of the extracellular Dityrosines network in the cuticle, whereas glutamyl–lysine isopeptide bonds are not affected. The lateral septate junctions of epidermal cells that serve as a paracellular plug are intact, as well. Taken together, we hypothesise that Alas activity, which initiates heme biosynthesis in the mitochondrion, is needed for the formation of a Dityrosine-based barrier that confers resistance to the internal hydrostatic pressure protecting both the cuticle from transcellular infiltration of body fluid and the animal from dehydration. We conclude that at least two modules – an apical protein–chitin lattice and the lateral septate junctions, act in parallel to ensure Drosophila skin impermeability.
Hunter N B Moseley - One of the best experts on this subject based on the ideXlab platform.
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entropy based analysis of vertebrate sperm protamines sequences evidence of potential Dityrosine and cysteine tyrosine cross linking in sperm protamines
BMC Genomics, 2020Co-Authors: Christian D Powell, Jason E Derouchey, Daniel C Kirchoff, Hunter N B MoseleyAbstract:Spermatogenesis is the process by which germ cells develop into spermatozoa in the testis. Sperm protamines are small, arginine-rich nuclear proteins which replace somatic histones during spermatogenesis, allowing a hypercondensed DNA state that leads to a smaller nucleus and facilitating sperm head formation. In eutherian mammals, the protamine-DNA complex is achieved through a combination of intra- and intermolecular cysteine cross-linking and possibly histidine-cysteine zinc ion binding. Most metatherian sperm protamines lack cysteine but perform the same function. This lack of dicysteine cross-linking has made the mechanism behind metatherian protamines folding unclear. Protamine sequences from UniProt’s databases were pulled down and sorted into homologous groups. Multiple sequence alignments were then generated and a gap weighted relative entropy score calculated for each position. For the eutherian alignments, the cysteine containing positions were the most highly conserved. For the metatherian alignment, the tyrosine containing positions were the most highly conserved and corresponded to the cysteine positions in the eutherian alignment. High conservation indicates likely functionally/structurally important residues at these positions in the metatherian protamines and the correspondence with cysteine positions within the eutherian alignment implies a similarity in function. One possible explanation is that the metatherian protamine structure relies upon Dityrosine cross-linking between these highly conserved tyrosines. Also, the human protamine P1 sequence has a tyrosine substitution in a position expecting eutherian dicysteine cross-linking. Similarly, some members of the metatherian Planigales genus contain cysteine substitutions in positions expecting plausible metatherian Dityrosine cross-linking. Rare cysteine-tyrosine cross-linking could explain both observations.
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entropy based analysis of vertebrate sperm protamine sequences evidence of Dityrosine and cysteine tyrosine cross linking in sperm protamines
bioRxiv, 2019Co-Authors: Christian D Powell, Jason E Derouchey, Daniel C Kirchoff, Hunter N B MoseleyAbstract:Background: Spermatogenesis is the process by which germ cells develop into spermatozoa in the testis. Sperm protamines are small, arginine-rich nuclear proteins which replace somatic histones during spermatogenesis, allowing a hypercondensed DNA state that leads to a smaller nucleus and facilitating sperm head formation. In eutherian mammals, the protamine-DNA complex is achieved through a combination of intra- and intermolecular cysteine cross-linking and possibly histidine-cysteine zinc ion binding. Most metatherian sperm protamines lack cysteine but perform the same function. This lack of dicysteine cross-linking has made the mechanism behind metatherian protamines folding unclear. Results: Protamine sequences from UniProt9s databases were pulled down and sorted into homologous groups. Multiple sequence alignments were then generated and a gap weighted relative entropy score calculated for each position. For the eutherian alignments, the cysteine containing positions were the most highly conserved. For the metatherian alignment, the tyrosine containing positions were the most highly conserved and corresponded to the cysteine positions in the eutherian alignment. Conclusions: High conservation indicates likely functionally/structurally important residues at these positions in the metatherian protamines and the correspondence with cysteine positions within the eutherian alignment implies a similarity in function. One explanation is that the metatherian protamine structure relies upon Dityrosine cross-linking between these highly conserved tyrosines. Also, the human protamine P1 sequence has a tyrosine substitution in a position expecting eutherian dicysteine cross-linking. Similarly, some members of the metatherian Planigales genus contain cysteine substitutions in positions expecting plausible metatherian Dityrosine cross-linking. Rare cysteine-tyrosine cross-linking could explain both observations.
Kevin J. Barnham - One of the best experts on this subject based on the ideXlab platform.
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Characterization and Identification of Dityrosine Cross-Linked Peptides Using Tandem Mass Spectrometry
2017Co-Authors: Soumya Mukherjee, Craig A Hutton, Eugene A. Kapp, Amber Lothian, Anne M. Roberts, Yury V. Vasil’ev, Berin A. Boughton, Kevin J. Barnham, Mei W. Kok, Colin L. MastersAbstract:The use of mass spectrometry coupled with chemical cross-linking of proteins has become a powerful tool for proteins structure and interactions studies. Unlike structural analysis of proteins using chemical reagents specific for lysine or cysteine residues, identification of gas-phase fragmentation patterns of endogenous Dityrosine cross-linked peptides have not been investigated. Dityrosine cross-linking in proteins and peptides are clinical markers of oxidative stress, aging, and neurodegenerative diseases including Alzheimer’s disease and Parkinson’s disease. In this study, we investigated and characterized the fragmentation pattern of a synthetically prepared Dityrosine cross-linked dimer of Aβ(1–16) using ESI tandem mass spectrometry. We then detailed the fragmentation pattern of Dityrosine cross-linked Aβ(1–16), using collision induced dissociation (CID), higher-energy collision induced dissociation (HCD), electron transfer dissociation (ETD), and electron capture dissociation (ECD). Application of these generic fragmentation rules of Dityrosine cross-linked peptides allowed for the identification of Dityrosine cross-links in peptides of Aβ and α-synuclein generated in vitro by enzymatic peroxidation. We report, for the first time, the Dityrosine cross-linked residues in human hemoglobin and α-synuclein under oxidative conditions. Together these tools open up the potential for automated analysis of this naturally occurring post-translation modification in neurodegenerative diseases as well as other pathological conditions
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Characterization and Identification of Dityrosine Cross-Linked Peptides Using Tandem Mass Spectrometry
'American Chemical Society (ACS)', 2017Co-Authors: Mukherjee S, Kevin J. Barnham, Ea Kapp, Lothian A, Am Roberts, Yv Vasil'ev, Ba Boughton, Wm Kok, Ca Hutton, Cl MastersAbstract:The use of mass spectrometry coupled with chemical cross-linking of proteins has become a powerful tool for proteins structure and interactions studies. Unlike structural analysis of proteins using chemical reagents specific for lysine or cysteine residues, identification of gas-phase fragmentation patterns of endogenous Dityrosine cross-linked peptides have not been investigated. Dityrosine cross-linking in proteins and peptides are clinical markers of oxidative stress, aging, and neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. In this study, we investigated and characterized the fragmentation pattern of a synthetically prepared Dityrosine cross-linked dimer of Aβ(1-16) using ESI tandem mass spectrometry. We then detailed the fragmentation pattern of Dityrosine cross-linked Aβ(1-16), using collision induced dissociation (CID), higher-energy collision induced dissociation (HCD), electron transfer dissociation (ETD), and electron capture dissociation (ECD). Application of these generic fragmentation rules of Dityrosine cross-linked peptides allowed for the identification of Dityrosine cross-links in peptides of Aβ and α-synuclein generated in vitro by enzymatic peroxidation. We report, for the first time, the Dityrosine cross-linked residues in human hemoglobin and α-synuclein under oxidative conditions. Together these tools open up the potential for automated analysis of this naturally occurring post-translation modification in neurodegenerative diseases as well as other pathological conditions
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the redox chemistry of the alzheimer s disease amyloid β peptide
Biochimica et Biophysica Acta, 2007Co-Authors: Danielle G Smith, Kevin J. Barnham, Roberto CappaiAbstract:There is a growing body of evidence to support a role for oxidative stress in Alzheimer's disease (AD), with increased levels of lipid peroxidation, DNA and protein oxidation products (HNE, 8-HO-guanidine and protein carbonyls respectively) in AD brains. The brain is a highly oxidative organ consuming 20% of the body's oxygen despite accounting for only 2% of the total body weight. With normal ageing the brain accumulates metals ions such iron (Fe), zinc (Zn) and copper (Cu). Consequently the brain is abundant in antioxidants to control and prevent the detrimental formation of reactive oxygen species (ROS) generated via Fenton chemistry involving redox active metal ion reduction and activation of molecular oxygen. In AD there is an over accumulation of the Amyloid beta peptide (Abeta), this is the result of either an elevated generation from amyloid precursor protein (APP) or inefficient clearance of Abeta from the brain. Abeta can efficiently generate reactive oxygen species in the presence of the transition metals copper and iron in vitro. Under oxidative conditions Abeta will form stable Dityrosine cross-linked dimers which are generated from free radical attack on the tyrosine residue at position 10. There are elevated levels of urea and SDS resistant stable linked Abeta oligomers as well as Dityrosine cross-linked peptides and proteins in AD brain. Since soluble Abeta levels correlate best with the degree of degeneration [C.A. McLean, R.A. Cherny, F.W. Fraser, S.J. Fuller, M.J. Smith, K. Beyreuther, A.I. Bush, C.L. Masters, Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer's disease, Ann. Neurol. 46 (1999) 860-866] we suggest that the toxic Abeta species corresponds to a soluble Dityrosine cross-linked oligomer. Current therapeutic strategies using metal chelators such as clioquinol and desferrioxamine have had some success in altering the progression of AD symptoms. Similarly, natural antioxidants curcumin and ginkgo extract have modest but positive effects in slowing AD development. Therefore, drugs that target the oxidative pathways in AD could have genuine therapeutic efficacy.