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Hodara R, Weiss D, Joseph G, Velasquez-Castano JC, Landázuri N, Han JW, Yoon YS, Taylor WR. Overexpression of catalase in myeloid cells causes impaired postischemic neovascularization. Arterioscler Thromb Vasc Biol 2011; 31:2203-9. [PMID: 21799178 DOI: 10.1161/atvbaha.111.233247] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
OBJECTIVE Myeloid lineage cells (MLCs) such as macrophages are known to play a key role in postischemic neovascularization. However, the role of MLC-derived reactive oxygen species in this process and their specific chemical identity remain unknown. METHODS AND RESULTS Transgenic mice with MLC-specific overexpression of catalase (Tg(Cat-MLC) mice) were created on a C57BL/6 background. Macrophage catalase activity was increased 3.4-fold compared with wild-type mice. After femoral artery ligation, laser Doppler perfusion imaging revealed impaired perfusion recovery in Tg(Cat-MLC) mice. This was associated with fewer collateral vessels, as assessed by microcomputed tomography angiography, and decreased capillary density. Impaired functional recovery of the ischemic limb was also evidenced by a 50% reduction in spontaneous running activity. The deficient neovascularization was associated with a blunted inflammatory response, characterized by decreased macrophage infiltration of ischemic tissues, and lower mRNA levels of inflammatory markers, such as tumor necrosis factor-α, osteopontin, and matrix mettaloproteinase-9. In vitro macrophage migration was impaired in Tg(Cat-MLC) mice, suggesting a role for H(2)O(2) in regulating the ability of macrophages to infiltrate ischemic tissues. CONCLUSIONS MLC-derived H(2)O(2) plays a key role in promoting neovascularization in response to ischemia and is a necessary factor for the development of ischemia-induced inflammation.
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Affiliation(s)
- Roberto Hodara
- Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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2
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Martinez-Vicente M, Talloczy Z, Kaushik S, Massey AC, Mazzulli J, Mosharov EV, Hodara R, Fredenburg R, Wu DC, Follenzi A, Dauer W, Przedborski S, Ischiropoulos H, Lansbury PT, Sulzer D, Cuervo AM. Dopamine-modified alpha-synuclein blocks chaperone-mediated autophagy. J Clin Invest 2008; 118:777-88. [PMID: 18172548 DOI: 10.1172/jci32806] [Citation(s) in RCA: 310] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 10/22/2007] [Indexed: 11/17/2022] Open
Abstract
Altered degradation of alpha-synuclein (alpha-syn) has been implicated in the pathogenesis of Parkinson disease (PD). We have shown that alpha-syn can be degraded via chaperone-mediated autophagy (CMA), a selective lysosomal mechanism for degradation of cytosolic proteins. Pathogenic mutants of alpha-syn block lysosomal translocation, impairing their own degradation along with that of other CMA substrates. While pathogenic alpha-syn mutations are rare, alpha-syn undergoes posttranslational modifications, which may underlie its accumulation in cytosolic aggregates in most forms of PD. Using mouse ventral medial neuron cultures, SH-SY5Y cells in culture, and isolated mouse lysosomes, we have found that most of these posttranslational modifications of alpha-syn impair degradation of this protein by CMA but do not affect degradation of other substrates. Dopamine-modified alpha-syn, however, is not only poorly degraded by CMA but also blocks degradation of other substrates by this pathway. As blockage of CMA increases cellular vulnerability to stressors, we propose that dopamine-induced autophagic inhibition could explain the selective degeneration of PD dopaminergic neurons.
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Affiliation(s)
- Marta Martinez-Vicente
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Yeshiva University, New York, New York 10461, USA
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3
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Heijnen HFG, van Donselaar E, Slot JW, Fries DM, Blachard-Fillion B, Hodara R, Lightfoot R, Polydoro M, Spielberg D, Thomson L, Regan EA, Crapo J, Ischiropoulos H. Subcellular localization of tyrosine-nitrated proteins is dictated by reactive oxygen species generating enzymes and by proximity to nitric oxide synthase. Free Radic Biol Med 2006; 40:1903-13. [PMID: 16716892 DOI: 10.1016/j.freeradbiomed.2005.09.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Revised: 09/02/2005] [Accepted: 09/02/2005] [Indexed: 10/25/2022]
Abstract
Using high-resolution immuno-electron microscopy the steady-state subcellular distribution of tyrosine-nitrated proteins in different cells and tissues was evaluated. In quiescent eosinophils and neutrophils in the bone marrow intracellular nitrated proteins were mainly restricted to the peroxidase-containing secretory granules. The inducible nitric oxide synthase (iNOS) was expressed in the same granules. Proteins nitrated on tyrosine residues were also abundant in the cytosol of circulating erythrocytes. In the vasculature, nitrated proteins were mainly located in mitochondria and endoplasmic reticulum of the endothelial cells, fibroblasts, and smooth muscle cells. Endogenous nitrated proteins were also found in chondrocytes in cartilage, where it was typically associated with the cytoplasmic interface of the endoplasmic reticulum membrane. Nitrated proteins were also prominent in the peroxisomes of liver hepatocytes and of secretory cells in the lacrimal gland. Challenge of mouse dendritic cells with lipopolysaccharide induced iNOS protein expression in cytosol and peroxisomes and was associated with an increased 3-nitrotyrosine formation in cytosol, mitochondria, and peroxisomes. These data indicate that nitric oxide-dependent protein tyrosine nitration is a physiologically relevant process localized within specific subcellular compartments in close proximity to iNOS and to enzymes capable of peroxidative chemistry and reactive oxygen species production.
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Affiliation(s)
- Harry F G Heijnen
- Thrombosis and Hemostasis Laboratory, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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4
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Greco TM, Hodara R, Parastatidis I, Heijnen HFG, Dennehy MK, Liebler DC, Ischiropoulos H. Identification of S-nitrosylation motifs by site-specific mapping of the S-nitrosocysteine proteome in human vascular smooth muscle cells. Proc Natl Acad Sci U S A 2006; 103:7420-5. [PMID: 16648260 PMCID: PMC1464354 DOI: 10.1073/pnas.0600729103] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
S-nitrosylation, the selective modification of cysteine residues in proteins to form S-nitrosocysteine, is a major emerging mechanism by which nitric oxide acts as a signaling molecule. Even though nitric oxide is intimately involved in the regulation of vascular smooth muscle cell functions, the potential protein targets for nitric oxide modification as well as structural features that underlie the specificity of protein S-nitrosocysteine formation in these cells remain unknown. Therefore, we used a proteomic approach using selective peptide capturing and site-specific adduct mapping to identify the targets of S-nitrosylation in human aortic smooth muscle cells upon exposure to S-nitrosocysteine and propylamine propylamine NONOate. This strategy identified 20 unique S-nitrosocysteine-containing peptides belonging to 18 proteins including cytoskeletal proteins, chaperones, proteins of the translational machinery, vesicular transport, and signaling. Sequence analysis of the S-nitrosocysteine-containing peptides revealed the presence of acid/base motifs, as well as hydrophobic motifs surrounding the identified cysteine residues. High-resolution immunogold electron microscopy supported the cellular localization of several of these proteins. Interestingly, seven of the 18 proteins identified are localized within the ER/Golgi complex, suggesting a role for S-nitrosylation in membrane trafficking and ER stress response in vascular smooth muscle.
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Affiliation(s)
- Todd M. Greco
- *Stokes Research Institute and Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104
| | - Roberto Hodara
- *Stokes Research Institute and Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104
| | - Ioannis Parastatidis
- *Stokes Research Institute and Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104
| | - Harry F. G. Heijnen
- Thrombosis and Haemostasis Laboratory, Department of Cell Biology, University Medical Center Utrecht, and Institute for Biomembranes, 3584 CH, Utrecht, The Netherlands; and
| | - Michelle K. Dennehy
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Daniel C. Liebler
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Harry Ischiropoulos
- *Stokes Research Institute and Departments of Pediatrics and Pharmacology, Children’s Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA 19104
- To whom correspondence should be addressed. E-mail:
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5
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Trostchansky A, Lind S, Hodara R, Oe T, Blair I, Ischiropoulos H, Rubbo H, Souza J. Interaction with phospholipids modulates alpha-synuclein nitration and lipid-protein adduct formation. Biochem J 2006; 393:343-9. [PMID: 16146428 PMCID: PMC1383693 DOI: 10.1042/bj20051277] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Intracellular aggregates of alpha-syn (alpha-synuclein) represent pathoanatomical hallmarks of neurodegenerative disorders (synucleinopathies). The molecular mechanisms underlying alpha-syn aggregation into filamentous inclusions may involve oxidation and nitration of the protein. Whereas the effects of oxidants and nitrating species on soluble alpha-syn have been studied in detail, the effect of these reactive species on alpha-syn associated with lipids is still unknown. In the present paper, we report that alpha-syn bound to small unilamellar liposomes composed of phosphatidylcholine/phosphatidic acid is resistant to oxidation and nitration when compared with soluble alpha-syn. Additionally, increasing concentrations of unsaturated fatty acids diminished the oxidation and nitration of alpha-syn upon exposure to fluxes of peroxynitrite (8-20 microM x min(-1)). To investigate the effect of oxidized lipids on alpha-syn, the protein was incubated with the bifunctional electrophile 4-HNE [4-hydroxy-2(E)-nonenal]. MS analysis showed the formation of three major products corresponding to the native protein and alpha-syn plus one or two 4-HNE molecules. Trypsin digestion of the modified protein followed by peptide 'finger-printing' revealed that 4-HNE modified the peptide E46GVVHGVATVAEK58. Further analysis of the peptides with liquid chromatography-tandem MS identified the modified residue as His50. The data indicate that the association of alpha-syn with biological membranes protects the protein from oxidation and nitration and thus diminishes the formation of protein molecules capable of forming aggregates. However, products of lipid peroxidation can also modify alpha-syn, generating novel protein adducts that could serve as biomarkers for documenting oxidative processes in human as well as animal and cellular models of alpha-syn aggregation and pathology.
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Affiliation(s)
- Andrés Trostchansky
- *Center for Free Radical and Biomedical Research, Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Avenida General Flores 2125, CP 11800, Montevideo, Uruguay
| | - Summer Lind
- †Stokes Research Institute and Department of Pharmacology, Children's Hospital of Philadelphia and the University of Pennsylvania, PA 19104, U.S.A
| | - Roberto Hodara
- †Stokes Research Institute and Department of Pharmacology, Children's Hospital of Philadelphia and the University of Pennsylvania, PA 19104, U.S.A
| | - Tomoyuki Oe
- ‡Center for Cancer Pharmacology, University of Pennsylvania School of Medicine, PA 19104, U.S.A
| | - Ian A. Blair
- ‡Center for Cancer Pharmacology, University of Pennsylvania School of Medicine, PA 19104, U.S.A
| | - Harry Ischiropoulos
- †Stokes Research Institute and Department of Pharmacology, Children's Hospital of Philadelphia and the University of Pennsylvania, PA 19104, U.S.A
| | - Homero Rubbo
- *Center for Free Radical and Biomedical Research, Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Avenida General Flores 2125, CP 11800, Montevideo, Uruguay
| | - José M. Souza
- *Center for Free Radical and Biomedical Research, Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Avenida General Flores 2125, CP 11800, Montevideo, Uruguay
- To whom correspondence should be addressed (email )
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Mishizen-Eberz AJ, Norris EH, Giasson BI, Hodara R, Ischiropoulos H, Lee VMY, Trojanowski JQ, Lynch DR. Cleavage of alpha-synuclein by calpain: potential role in degradation of fibrillized and nitrated species of alpha-synuclein. Biochemistry 2005; 44:7818-29. [PMID: 15909996 DOI: 10.1021/bi047846q] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Alpha-synuclein (alpha-syn) is a major protein component of the neuropathological hallmarks of Parkinson's disease and related neurodegenerative disorders termed synucleinopathies. Neither the mechanism of alpha-syn fibrillization nor the degradative process for alpha-syn has been elucidated. Previously, we showed that wild-type, mutated, and fibrillar alpha-syn proteins are substrates of calpain I in vitro. In this study, we demonstrate that calpain-mediated cleavage near and within the middle region of soluble alpha-syn with/without tyrosine nitration and oxidation generates fragments that are unable to self-fibrillize. More importantly, these fragments prevent full-length alpha-syn from fibrillizing. Calpain-mediated cleavage of alpha-syn fibrils composed of wild-type or nitrated alpha-syn generate C-terminally truncated fragments that retain their fibrillar structure and induce soluble full-length alpha-syn to co-assemble. Therefore, calpain-cleaved soluble alpha-syn inhibits fibrillization, whereas calpain-cleaved fibrillar alpha-syn promotes further co-assembly. These results provide insight into possible disease mechanisms underlying synucleinopathies since the formation of alpha-syn fibrils could be causally linked to the onset/progression of these disorders.
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Affiliation(s)
- Amanda J Mishizen-Eberz
- Department of Neurology, University of Pennsylvania and The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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7
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Norris EH, Giasson BI, Hodara R, Xu S, Trojanowski JQ, Ischiropoulos H, Lee VMY. Reversible Inhibition of α-Synuclein Fibrillization by Dopaminochrome-mediated Conformational Alterations. J Biol Chem 2005; 280:21212-9. [PMID: 15817478 DOI: 10.1074/jbc.m412621200] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies demonstrated that alpha-synuclein (alpha-syn) fibrillization is inhibited by dopamine, and studies to understand the molecular basis of this process were conducted (Conway, K. A., Rochet, J. C., Bieganski, R. M., and Lansbury, P. T., Jr. (2001) Science 294, 1346-1349). Dopamine inhibition of alpha-syn fibrillization generated exclusively spherical oligomers that depended on dopamine autoxidation but not alpha-syn oxidation, because mutagenesis of Met, His, and Tyr residues in alpha-syn did not abrogate this inhibition. However, truncation of alpha-syn at residue 125 restored the ability of alpha-syn to fibrillize in the presence of dopamine. Mutagenesis and competition studies with specific synthetic peptides identified alpha-syn residues 125-129 (i.e. YEMPS) as an important region in the dopamine-induced inhibition of alpha-syn fibrillization. Significantly, the dopamine oxidation product dopaminochrome was identified as a specific inhibitor of alpha-syn fibrillization. Dopaminochrome promotes the formation of spherical oligomers by inducing conformational changes, as these oligomers regained the ability to fibrillize by simple denaturation/renaturation. Taken together, these data indicate that dopamine inhibits alpha-syn fibrillization by inducing structural changes in alpha-syn that can occur through the interaction of dopaminochrome with the 125YEMPS129 motif of alpha-syn. These results suggest that the dopamine autoxidation can prevent alpha-syn fibrillization in dopaminergic neurons through a novel mechanism. Thus, decreased dopamine levels in substantia nigra neurons might promote alpha-syn aggregation in Parkinson's disease.
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Affiliation(s)
- Erin H Norris
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, Institute on Aging, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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8
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Hodara R, Norris EH, Giasson BI, Mishizen-Eberz AJ, Lynch DR, Lee VMY, Ischiropoulos H. Functional Consequences of α-Synuclein Tyrosine Nitration. J Biol Chem 2004; 279:47746-53. [PMID: 15364911 DOI: 10.1074/jbc.m408906200] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have shown the presence of nitrated alpha-synuclein (alpha-syn) in human Lewy bodies and other alpha-syn inclusions. Herein, the effects of tyrosine nitration on alpha-syn fibril formation, lipid binding, chaperone-like function, and proteolytic degradation were systematically examined by employing chromatographically isolated nitrated monomeric, dimeric, and oligomeric alpha-syn. Nitrated alpha-syn monomers and dimers but not oligomers accelerated the rate of fibril formation of unmodified alpha-syn when present at low concentrations. Immunoelectron microscopy revealed that nitrated monomers and dimers are incorporated into the fibrils. However, the purified nitrated alpha-syn monomer by itself was unable to form fibrils. Nitration of the tyrosine residue at position 39 was largely responsible for decreased binding of nitrated monomeric alpha-syn to synthetic vesicles, which correlated with an impairment of the nitrated protein to adopt alpha-helical conformation in the presence of liposomes. The chaperone-like activity of alpha-syn was not inhibited by nitration or oxidation. Furthermore, the 20 S proteasome and calpain I degraded nitrated monomeric alpha-syn, although at a slower rate compared with control alpha-syn. Collectively, these data suggest that post-translational modification of alpha-syn by nitration can promote the formation of intracytoplasmic inclusions that constitute the hallmark of Parkinson disease and other synucleinopathies.
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Affiliation(s)
- Roberto Hodara
- Stokes Research Institute and Department of Biochemistry and Biophysics, Children's Hospital of Philadelphia and the University of Pennsylvania, 19104, USA
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9
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Norris EH, Giasson BI, Xu S, Hodara R, Trojanowski JQ, Ischiropoulos H, Lee V. P1-302 Implications of dopamine-induced modificationsof alpha-synuclein protein in the pathogenesis of Parkinson's disease. Neurobiol Aging 2004. [DOI: 10.1016/s0197-4580(04)80615-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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10
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Mishizen-Eberz AJ, Guttmann RP, Giasson BI, Day GA, Hodara R, Ischiropoulos H, Lee VMY, Trojanowski JQ, Lynch DR. Distinct cleavage patterns of normal and pathologic forms of alpha-synuclein by calpain I in vitro. J Neurochem 2003; 86:836-47. [PMID: 12887682 DOI: 10.1046/j.1471-4159.2003.01878.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) is characterized by fibrillary neuronal inclusions called Lewy bodies (LBs) consisting largely of alpha-synuclein (alpha-syn), the protein mutated in some patients with familial PD. The mechanisms of alpha-syn fibrillization and LB formation are unknown, but may involve aberrant degradation or turnover. We examined the ability of calpain I to cleave alpha-syn in vitro. Calpain I cleaved wild-type alpha-syn predominantly after amino acid 57 and within the non-amyloid component (NAC) region. In contrast, calpain I cleaved fibrillized alpha-syn primarily in the region of amino acid 120 to generate fragments like those that increase susceptibility to dopamine toxicity and oxidative stress. Further, while calpain I cleaved wild-type alpha-syn after amino acid 57, this did not occur in mutant A53T alpha-syn. This paucity of proteolysis could increase the stability of A53T alpha-syn, suggesting that calpain I might protect cells from forming LBs by specific cleavages of soluble wild-type alpha-syn. However, once alpha-syn has polymerized into fibrils, calpain I may contribute to toxicity of these forms of alpha-syn by cleaving at aberrant sites within the C-terminal region. Elucidating the role of calpain I in the proteolytic processing of alpha-syn in normal and diseased brains may clarify mechanisms of neurodegenerative alpha-synucleinopathies.
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Abstract
Mitochondria constitute a primary locus for the intracellular formation and reactions of peroxynitrite, and these interactions are recognized to contribute to the biological and pathological effects of both nitric oxide ((*)NO) and peroxynitrite. Extra- or intramitochondrially formed peroxynitrite can diffuse through mitochondrial compartments and undergo fast direct and free radical-dependent target molecule reactions. These processes result in oxidation, nitration, and nitrosation of critical components in the matrix, inner and outer membrane, and intermembrane space. Mitochondrial scavenging and repair systems for peroxynitrite-dependent oxidative modifications operate but they can be overwhelmed under enhanced cellular (*)NO formation as well as under conditions that lead to augmented superoxide formation by the electron transport chain. Peroxynitrite can lead to alterations in mitochondrial energy and calcium homeostasis and promote the opening of the permeability transition pore. The effects of peroxynitrite in mitochondrial physiology can be largely rationalized based on the reactivities of peroxynitrite and peroxynitrite-derived carbonate, nitrogen dioxide, and hydroxyl radicals with critical protein amino acids and transition metal centers of key mitochondrial proteins. In this review we analyze (i) the existing evidence for the intramitochondrial formation and reactions of peroxynitrite, (ii) the key reactions and fate of peroxynitrite in mitochondria, and (iii) their impact in mitochondrial physiology and signaling of cell death.
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Affiliation(s)
- Rafael Radi
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
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Abstract
Nitric oxide (*NO) and peroxynitrite (ONOO-) avidly interact with mitochondrial components, leading to a range of biological responses spanning from the modulation of mitochondrial respiration, mitochondrial dysfunction to the signaling of apoptotic cell death. Physiological levels of *NO primarily interact with cytochrome c oxidase, leading to a competitive and reversible inhibition of mitochondrial oxygen uptake. In turn, this leads to alterations in electrochemical gradients, which affect calcium uptake and may regulate processes such as mitochondrial transition pore (MTP) opening and the release of pro-apoptotic proteins. Large or persistent levels of *NO in mitochondria promote mitochondrial oxidant formation. Peroxynitrite formed either extra- or intra-mitochondrially leads to oxidative damage, most notably at complexes I and II of the electron transport chain, ATPase, aconitase and Mn-superoxide dismutase. Mitochondrial scavenging systems for peroxynitrite and peroxynitrite-derived radicals such as carbonate (CO3*-) and nitrogen dioxide radicals (*NO2) include cytochrome c oxidase, glutathione and ubiquinol and serve to partially attenuate the reactions of these oxidants with critical mitochondrial targets. Detection of nitrated mitochondrial proteins in vivo supports the concept that mitochondria constitute central loci of the toxic effects of excess reactive nitrogen species. In this review we will provide an overview of the biochemical mechanisms by which *NO and ONOO- regulate or alter mitochondrial functions.
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Affiliation(s)
- Rafael Radi
- Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
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Abstract
Peroxynitrite (ONOO(-)), the product of superoxide (O(2)) and nitric oxide (.NO) reaction, inhibits mitochondrial respiration and can stimulate apoptosis. Cytochrome c, a mediator of these two aspects of mitochondrial function, thus represents an important potential target of ONOO(-) during conditions involving accelerated rates of oxygen radical and.NO generation. Horse heart cytochrome c(3+) was nitrated by ONOO(-), as indicated by spectral changes, Western blot analysis, and mass spectrometry. A dose-dependent loss of cytochrome c(3+) 695 nm absorption occurred, inferring that nitration of a critical heme-vicinal tyrosine (Tyr-67) promoted a conformational change, displacing the Met-80 heme ligand. Nitration was confirmed by cross-reactivity with a specific antibody against 3-nitrotyrosine and by increased molecular mass compatible with the addition of a nitro-(-NO(2)) group. Mass analysis of tryptic digests indicated the preferential nitration of Tyr-67 among the four conserved tyrosine residues in cytochrome c. Cytochrome c(3+) was more extensively nitrated than cytochrome c(2+) because of the preferential oxidation of the reduced heme by ONOO(-). Similar protein nitration patterns were obtained by ONOO(-) reaction in the presence of carbon dioxide, whereupon secondary nitrating species arise from the decomposition of the nitroso-peroxocarboxylate (ONOOCO(2)(-)) intermediate. Peroxynitrite-nitrated cytochrome c displayed significant changes in redox properties, including (a) increased peroxidatic activity, (b) resistance to reduction by ascorbate, and (c) impaired support of state 4-dependent respiration in intact rat heart mitochondria. These results indicate that cytochrome c nitration may represent both oxidative and signaling events occurring during .NO- and ONOO(-)-mediated cell injury.
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Affiliation(s)
- A M Cassina
- Departamento de Bioquimica, Facultad de Medicina and Laboratorio de Enzimologia, Instituto de Quimica Biológica, Facultad de Ciencias, Universidad de la República, 11800 Montevideo, Uruguay
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