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Noreng S, Ota N, Sun Y, Ho H, Johnson M, Arthur CP, Schneider K, Lehoux I, Davies CW, Mortara K, Wong K, Seshasayee D, Masureel M, Payandeh J, Yi T, Koerber JT. Structure of the core human NADPH oxidase NOX2. Nat Commun 2022; 13:6079. [PMID: 36241643 DOI: 10.1038/s41467-022-33711-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 09/27/2022] [Indexed: 12/24/2022] Open
Abstract
NOX2 is the prototypical member of the NADPH oxidase NOX superfamily and produces superoxide (O2•-), a key reactive oxygen species (ROS) that is essential in innate and adaptive immunity. Mutations that lead to deficiency in NOX2 activity correlate with increased susceptibility to bacterial and fungal infections, resulting in chronic granulomatous disease. The core of NOX2 is formed by a heterodimeric transmembrane complex composed of NOX2 (formerly gp91) and p22, but a detailed description of its structural architecture is lacking. Here, we present the structure of the human NOX2 core complex bound to a selective anti-NOX2 antibody fragment. The core complex reveals an intricate extracellular topology of NOX2, a four-transmembrane fold of the p22 subunit, and an extensive transmembrane interface which provides insights into NOX2 assembly and activation. Functional assays uncover an inhibitory activity of the 7G5 antibody mediated by internalization-dependent and internalization-independent mechanisms. Overall, our results provide insights into the NOX2 core complex architecture, disease-causing mutations, and potential avenues for selective NOX2 pharmacological modulation.
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2
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CUI Z, SHU Y, XIE X, JIN Y. Light-driven activation of NADPH oxidases. Sci Sin -Vitae 2022. [DOI: 10.1360/ssv-2022-0134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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3
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Gansemer ER, Rutkowski DT. Pathways Linking Nicotinamide Adenine Dinucleotide Phosphate Production to Endoplasmic Reticulum Protein Oxidation and Stress. Front Mol Biosci 2022; 9:858142. [PMID: 35601828 PMCID: PMC9114485 DOI: 10.3389/fmolb.2022.858142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 04/04/2022] [Indexed: 11/13/2022] Open
Abstract
The endoplasmic reticulum (ER) lumen is highly oxidizing compared to other subcellular compartments, and maintaining the appropriate levels of oxidizing and reducing equivalents is essential to ER function. Both protein oxidation itself and other essential ER processes, such as the degradation of misfolded proteins and the sequestration of cellular calcium, are tuned to the ER redox state. Simultaneously, nutrients are oxidized in the cytosol and mitochondria to power ATP generation, reductive biosynthesis, and defense against reactive oxygen species. These parallel needs for protein oxidation in the ER and nutrient oxidation in the cytosol and mitochondria raise the possibility that the two processes compete for electron acceptors, even though they occur in separate cellular compartments. A key molecule central to both processes is NADPH, which is produced by reduction of NADP+ during nutrient catabolism and which in turn drives the reduction of components such as glutathione and thioredoxin that influence the redox potential in the ER lumen. For this reason, NADPH might serve as a mediator linking metabolic activity to ER homeostasis and stress, and represent a novel form of mitochondria-to-ER communication. In this review, we discuss oxidative protein folding in the ER, NADPH generation by the major pathways that mediate it, and ER-localized systems that can link the two processes to connect ER function to metabolic activity.
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Affiliation(s)
- Erica R. Gansemer
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - D. Thomas Rutkowski
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
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4
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Vermot A, Petit-Härtlein I, Smith SME, Fieschi F. NADPH Oxidases (NOX): An Overview from Discovery, Molecular Mechanisms to Physiology and Pathology. Antioxidants (Basel) 2021; 10:890. [PMID: 34205998 PMCID: PMC8228183 DOI: 10.3390/antiox10060890] [Citation(s) in RCA: 201] [Impact Index Per Article: 67.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/21/2021] [Accepted: 05/26/2021] [Indexed: 01/17/2023] Open
Abstract
The reactive oxygen species (ROS)-producing enzyme NADPH oxidase (NOX) was first identified in the membrane of phagocytic cells. For many years, its only known role was in immune defense, where its ROS production leads to the destruction of pathogens by the immune cells. NOX from phagocytes catalyzes, via one-electron trans-membrane transfer to molecular oxygen, the production of the superoxide anion. Over the years, six human homologs of the catalytic subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the NOX2/gp91phox component present in the phagocyte NADPH oxidase assembly itself, the homologs are now referred to as the NOX family of NADPH oxidases. NOX are complex multidomain proteins with varying requirements for assembly with combinations of other proteins for activity. The recent structural insights acquired on both prokaryotic and eukaryotic NOX open new perspectives for the understanding of the molecular mechanisms inherent to NOX regulation and ROS production (superoxide or hydrogen peroxide). This new structural information will certainly inform new investigations of human disease. As specialized ROS producers, NOX enzymes participate in numerous crucial physiological processes, including host defense, the post-translational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. These diversities of physiological context will be discussed in this review. We also discuss NOX misregulation, which can contribute to a wide range of severe pathologies, such as atherosclerosis, hypertension, diabetic nephropathy, lung fibrosis, cancer, or neurodegenerative diseases, giving this family of membrane proteins a strong therapeutic interest.
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Affiliation(s)
- Annelise Vermot
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, 38000 Grenoble, France; (A.V.); (I.P.-H.)
| | - Isabelle Petit-Härtlein
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, 38000 Grenoble, France; (A.V.); (I.P.-H.)
| | - Susan M. E. Smith
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA 30144, USA;
| | - Franck Fieschi
- Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale, 38000 Grenoble, France; (A.V.); (I.P.-H.)
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Wu X, Hénin J, Baciou L, Baaden M, Cailliez F, de la Lande A. Mechanistic Insights on Heme-to-Heme Transmembrane Electron Transfer Within NADPH Oxydases From Atomistic Simulations. Front Chem 2021; 9:650651. [PMID: 34017816 PMCID: PMC8129163 DOI: 10.3389/fchem.2021.650651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 04/06/2021] [Indexed: 11/13/2022] Open
Abstract
NOX5 is a member of the NADPH oxidase family which is dedicated to the production of reactive oxygen species. The molecular mechanisms governing transmembrane electron transfer (ET) that permits to shuttle electrons over the biological membrane have remained elusive for a long time. Using computer simulations, we report conformational dynamics of NOX5 embedded within a realistic membrane environment. We assess the stability of the protein within the membrane and monitor the existence of cavities that could accommodate dioxygen molecules. We investigate the heme-to-heme electron transfer. We find a reaction free energy of a few tenths of eV (ca. −0.3 eV) and a reorganization free energy of around 1.1 eV (0.8 eV after including electrostatic induction corrections). The former indicates thermodynamically favorable ET, while the latter falls in the expected values for transmembrane inter-heme ET. We estimate the electronic coupling to fall in the range of the μeV. We identify electron tunneling pathways showing that not only the W378 residue is playing a central role, but also F348. Finally, we reveal the existence of two connected O2−binding pockets near the outer heme with fast exchange between the two sites on the nanosecond timescale. We show that when the terminal heme is reduced, O2 binds closer to it, affording a more efficient tunneling pathway than when the terminal heme is oxidized, thereby providing an efficient mechanism to catalyze superoxide production in the final step. Overall, our study reveals some key molecular mechanisms permitting reactive oxygen species production by NOX5 and paves the road for further investigation of ET processes in the wide family of NADPH oxidases by computer simulations.
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Affiliation(s)
- Xiaojing Wu
- CNRS, Université de Paris, UPR 9080, Laboratoire de Biochimie Théorique, Paris, France.,Institut de Biologie Physico-Chimique-Fondation Edmond de Rotschild, PSL Research University, Paris, France
| | - Jérôme Hénin
- CNRS, Université de Paris, UPR 9080, Laboratoire de Biochimie Théorique, Paris, France.,Institut de Biologie Physico-Chimique-Fondation Edmond de Rotschild, PSL Research University, Paris, France
| | - Laura Baciou
- Institut de Chimie Physique, Université Paris Saclay, CNRS (UMR 8000), Orsay, France
| | - Marc Baaden
- CNRS, Université de Paris, UPR 9080, Laboratoire de Biochimie Théorique, Paris, France.,Institut de Biologie Physico-Chimique-Fondation Edmond de Rotschild, PSL Research University, Paris, France
| | - Fabien Cailliez
- Institut de Chimie Physique, Université Paris Saclay, CNRS (UMR 8000), Orsay, France
| | - Aurélien de la Lande
- Institut de Chimie Physique, Université Paris Saclay, CNRS (UMR 8000), Orsay, France
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6
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Kobayashi K, Kim J, Fukuda Y, Kozawa T, Inoue T. Fields, biochemistry fast autooxidation of a Bis-Histidyl-ligated globin from the anhydrobiotic tardigrade, ramazzottius varieornatus, by molecular oxygen. J Biochem 2021; 169:663-673. [PMID: 33479760 DOI: 10.1093/jb/mvab003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 12/27/2020] [Indexed: 01/11/2023] Open
Abstract
Tardigrades, a phylum of meiofaunal organisms, exhibit extraordinary tolerance to various environmental conditions, including extreme temperatures (-272 to 151 °C) and exposure to ionizing radiation. Proteins from anhydrobiotic tardigrades with homology to known proteins from other organisms are new potential targets for structural genomics. Recently, we reported spectroscopic and structural characterization of a hexacoordinated hemoglobin (Kumaglobin [Kgb]) found in an anhydrobiotic tardigrade. In the absence of its exogenous ligand, Kgb displays hexacoordination with distal and proximal histidines. In this work, we analyzed binding of the molecular oxygen ligand following reduction of heme in Kgb using a pulse radiolysis technique. Radiolytically generated hydrated electrons (eaq-) reduced the heme iron of Kgb within 20 µs. Subsequently, ferrous heme reacted with O2 to form a ferrous-dioxygen intermediate with a second-order rate constant of 3.0 × 106 M-1 s-1. The intermediate was rapidly (within 0.1 s) autooxidized to the ferric form. Redox potential measurements revealed an E'0 of -400 mV (vs. SHE) in the ferric/ferrous couple. Our results suggest that Kgb may serve as a physiological generator of O2·- via redox signaling and/or electron transfer.
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Affiliation(s)
- Kazuo Kobayashi
- The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
| | - JeeEun Kim
- Graduate School of Pharmaceutical Science, Osaka University, Suita, Japan
| | - Yohta Fukuda
- Graduate School of Pharmaceutical Science, Osaka University, Suita, Japan
| | - Takahiro Kozawa
- The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
| | - Tsuyoshi Inoue
- Graduate School of Pharmaceutical Science, Osaka University, Suita, Japan
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7
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Magnani F, Mattevi A. Structure and mechanisms of ROS generation by NADPH oxidases. Curr Opin Struct Biol 2019; 59:91-7. [PMID: 31051297 DOI: 10.1016/j.sbi.2019.03.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 02/14/2019] [Accepted: 03/04/2019] [Indexed: 12/31/2022]
Abstract
NADPH oxidases (NOXs) are integral membrane enzymes that produce reactive oxygen species. Humans have seven NOX enzymes that feature a very similar catalytic core but distinct regulatory mechanisms. The recent structural elucidation of the NOX catalytic domains has been a step forward in the field. NADPH, FAD, and two hemes form a linear array of redox cofactors that transfer electrons across to the two sides of the membrane. Oxygen is reduced through an unusual outer sphere mechanism that does not involve any covalent intermediate with the heme iron. Several recent studies have expanded the roles of NOXs in cell signaling, innate immune response, and cell proliferation including oncogenic transformation. This work reinforces NOX-generated ROS as powerful signaling molecules. A challenging question is to understand the specific mechanisms of enzyme regulation and to harness the growing insight on NOXs' structure and biochemistry to generate more powerful small-molecule modulators of NOX activities.
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Huetsch JC, Suresh K, Shimoda LA. Regulation of Smooth Muscle Cell Proliferation by NADPH Oxidases in Pulmonary Hypertension. Antioxidants (Basel) 2019; 8:antiox8030056. [PMID: 30841544 PMCID: PMC6466559 DOI: 10.3390/antiox8030056] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 02/25/2019] [Accepted: 03/01/2019] [Indexed: 02/07/2023] Open
Abstract
Hyperproliferation of pulmonary arterial smooth muscle cells is a key component of vascular remodeling in the setting of pulmonary hypertension (PH). Numerous studies have explored factors governing the changes in smooth muscle cell phenotype that lead to the increased wall thickness, and have identified various potential candidates. A role for reactive oxygen species (ROS) has been well documented in PH. ROS can be generated from a variety of sources, including mitochondria, uncoupled nitric oxide synthase, xanthine oxidase, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In this article, we will review recent data supporting a role for ROS generated from NADPH oxidases in promoting pulmonary arterial smooth muscle cell proliferation during PH.
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Affiliation(s)
- John C Huetsch
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21224, USA.
| | - Karthik Suresh
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21224, USA.
| | - Larissa A Shimoda
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Johns Hopkins School of Medicine, Baltimore, MD 21224, USA.
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9
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Abstract
Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.
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Affiliation(s)
- Jesús Tejero
- Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania ; Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania ; Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania ; and Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Sruti Shiva
- Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania ; Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania ; Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania ; and Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
| | - Mark T Gladwin
- Pittsburgh Heart, Lung, Blood and Vascular Medicine Institute, University of Pittsburgh , Pittsburgh, Pennsylvania ; Pulmonary, Allergy and Critical Care Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania ; Department of Pharmacology and Chemical Biology, University of Pittsburgh , Pittsburgh, Pennsylvania ; and Department of Medicine, Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh , Pittsburgh, Pennsylvania
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10
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Abstract
NADPH oxidases (NOXs) are membrane enzymes whose sole function is the generation of reactive oxygen species. Humans have seven NOX isoenzymes that feature distinct functions in immune response and cell signaling but share the same catalytic core comprising a FAD-binding dehydrogenase domain and a heme-binding transmembrane domain. We previously described a mutation that stabilizes the dehydrogenase domain of a prokaryotic homolog of human NOX5. The thermostable mutant exhibited a large 19 °C increase in the apparent melting temperature (app Tm) and a much tighter binding of the FAD cofactor, which allowed the crystallization and structure determination of the domain holo-form. Here, we analyze the transferability of this mutation onto prokaryotic and eukaryotic full-length NOX enzymes. We found that the mutation exerts a significative stabilizing effect on the full-length NOX5 from both Cylindrospermum stagnale (app Tm increase of 8 °C) and Homo sapiens (app ΔTm of 2 °C). Enhanced thermal stability resulted in more homogeneous preparations of the bacterial NOX5 with less aggregation problems. Moreover, we also found that the mutation increases the overall expression of recombinant human NOX4 and NOX5 in mammalian cells. Such a 2-5-fold increase is mainly due to the lowered cell toxicity, which leads to higher biomasses. Because of the high sequence identity of the catalytic core within this family of enzymes, this strategy can be a general tool to boost the production of all NOXs.
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Affiliation(s)
- Marta Ceccon
- a Department of Biology and Biotechnology , University of Pavia , Pavia , Italy
| | | | - Marta Massari
- a Department of Biology and Biotechnology , University of Pavia , Pavia , Italy
| | - Andrea Mattevi
- a Department of Biology and Biotechnology , University of Pavia , Pavia , Italy
| | - Francesca Magnani
- a Department of Biology and Biotechnology , University of Pavia , Pavia , Italy
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11
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Kim J, Fukuda Y, Inoue T. Crystal structure of Kumaglobin: a hexacoordinated heme protein from an anhydrobiotic tardigrade,
Ramazzottius varieornatus. FEBS J 2018; 286:1287-1304. [DOI: 10.1111/febs.14713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 09/28/2018] [Accepted: 11/29/2018] [Indexed: 01/05/2023]
Affiliation(s)
- JeeEun Kim
- Department of Applied Chemistry Graduate School of Engineering Osaka University Suita Japan
| | - Yohta Fukuda
- Department of Applied Chemistry Graduate School of Engineering Osaka University Suita Japan
| | - Tsuyoshi Inoue
- Department of Applied Chemistry Graduate School of Engineering Osaka University Suita Japan
- Graduate School of Pharmaceutical Science Suita Japan
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12
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Abstract
One of the most fascinating and exciting periods in my scientific career entailed dissecting the symbiotic relationship between two membrane transporters, the Nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase complex and voltage-gated proton channels (HV 1). By the time I entered this field, there had already been substantial progress toward understanding NADPH oxidase, but HV 1 were known only to a tiny handful of cognoscenti around the world. Having identified the first proton currents in mammalian cells in 1991, I needed to find a clear function for these molecules if the work was to become fundable. The then-recent discoveries of Henderson, Chappell, and colleagues in 1987-1988 that led them to hypothesize interactions of both molecules during the respiratory burst of phagocytes provided an excellent opportunity. In a nutshell, both transporters function by moving electrical charge across the membrane: NADPH oxidase moves electrons and HV 1 moves protons. The consequences of electrogenic NADPH oxidase activity on both membrane potential and pH strongly self-limit this enzyme. Fortunately, both consequences specifically activate HV 1, and HV 1 activity counteracts both consequences, a kind of yin-yang relationship. Notwithstanding a decade starting in 1995 when many believed the opposite, these are two separate molecules that function independently despite their being functionally interdependent in phagocytes. The relationship between NADPH oxidase and HV 1 has become a paradigm that somewhat surprisingly has now extended well beyond the phagocyte NADPH oxidase - an industrial strength producer of reactive oxygen species (ROS) - to myriad other cells that produce orders of magnitude less ROS for signaling purposes. These cells with their seven NADPH oxidase (NOX) isoforms provide a vast realm of mechanistic obscurity that will occupy future studies for years to come.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL, USA
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Magnani F, Nenci S, Millana Fananas E, Ceccon M, Romero E, Fraaije MW, Mattevi A. Crystal structures and atomic model of NADPH oxidase. Proc Natl Acad Sci U S A 2017; 114:6764-9. [PMID: 28607049 DOI: 10.1073/pnas.1702293114] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
NADPH oxidases (NOXs) are the only enzymes exclusively dedicated to reactive oxygen species (ROS) generation. Dysregulation of these polytopic membrane proteins impacts the redox signaling cascades that control cell proliferation and death. We describe the atomic crystal structures of the catalytic flavin adenine dinucleotide (FAD)- and heme-binding domains of Cylindrospermum stagnale NOX5. The two domains form the core subunit that is common to all seven members of the NOX family. The domain structures were then docked in silico to provide a generic model for the NOX family. A linear arrangement of cofactors (NADPH, FAD, and two membrane-embedded heme moieties) injects electrons from the intracellular side across the membrane to a specific oxygen-binding cavity on the extracytoplasmic side. The overall spatial organization of critical interactions is revealed between the intracellular loops on the transmembrane domain and the NADPH-oxidizing dehydrogenase domain. In particular, the C terminus functions as a toggle switch, which affects access of the NADPH substrate to the enzyme. The essence of this mechanistic model is that the regulatory cues conformationally gate NADPH-binding, implicitly providing a handle for activating/deactivating the very first step in the redox chain. Such insight provides a framework to the discovery of much needed drugs that selectively target the distinct members of the NOX family and interfere with ROS signaling.
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Kobayashi K, Nakagaki M, Ishikawa H, Iwai K, O’Brian MR, Ishimori K. Redox-Dependent Dynamics in Heme-Bound Bacterial Iron Response Regulator (Irr) Protein. Biochemistry 2016; 55:4047-54. [DOI: 10.1021/acs.biochem.6b00512] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kazuo Kobayashi
- The
Institute of Scientific and Industrial Research, Osaka University, Mihogaoka
8-1, Ibaraki, Osaka 567-0047, Japan
| | - Megumi Nakagaki
- Department
of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Haruto Ishikawa
- Department
of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Kazuhiro Iwai
- Molecular
and Cellular Physiology, Graduate School of Medicine, Kyoto University, Kyoto 606-8561, Japan
| | - Mark R. O’Brian
- Department
of Microbiology and Immunology, State University of New York at Buffalo, Buffalo, New York 14214, United States
| | - Koichiro Ishimori
- Department
of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
- Department
of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
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15
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Souabni H, Wien F, Bizouarn T, Houée-Levin C, Réfrégiers M, Baciou L. The physicochemical properties of membranes correlate with the NADPH oxidase activity. Biochim Biophys Acta Gen Subj 2016; 1861:3520-3530. [PMID: 27378459 DOI: 10.1016/j.bbagen.2016.06.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 05/25/2016] [Accepted: 06/28/2016] [Indexed: 01/01/2023]
Abstract
BACKGROUND Phagocytes kill ingested microbes by exposure to high concentrations of toxic reactive species generated by NADPH-oxidases. This membrane-bound electron-transferring enzyme is tightly regulated by cellular signaling cascades. So far, molecular and biophysical studies of the NADPH-oxidase were performed over limited temperature ranges, which weaken our understanding of immune response or inflammatory events. In this work, we have inspected the influence of temperature and lipid membrane properties on the NADPH-oxidase activity using a system free of cell complexity. METHODS We have extended the experimental conditions of the accepted model for NADPH-oxidase activity, the so-called cell-free assay, to a large temperature range (10-40°C) using different membrane compositions (subcellular compartments or liposomes). RESULTS A remarkable increase of superoxide production rate was observed with rising temperature. Synchrotron radiation circular dichroism data showed that this is not correlated with protein secondary structure changes. When lipid bilayers are in fluid phase, Arrhenius plots of the oxidase activity showed linear relationships with small activation energy (Ea), while when in solid phase, high Ea was found. The sterol content modulates kinetic and thermodynamic parameters. CONCLUSION High temperature promotes the rate of superoxide production. The key element of this enhancement is related to membrane properties such as thickness and viscosity and not to protein structural changes. Membrane viscosity that can be driven by sterols is a paramount parameter of Ea of NADPH oxidase activity. The membrane bilayer state modulated by its sterol content may be considered locally as an enzyme regulator. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.
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Affiliation(s)
- Hager Souabni
- Laboratoire de Chimie Physique UMR 8000, Univ. Paris-Sud, CNRS, Université Paris Saclay, 91405 Orsay Cedex, France
| | - Frank Wien
- Synchrotron SOLEIL, Campus Paris-Saclay, 91192 Gif-sur-Yvette Cedex, France
| | - Tania Bizouarn
- Laboratoire de Chimie Physique UMR 8000, Univ. Paris-Sud, CNRS, Université Paris Saclay, 91405 Orsay Cedex, France
| | - Chantal Houée-Levin
- Laboratoire de Chimie Physique UMR 8000, Univ. Paris-Sud, CNRS, Université Paris Saclay, 91405 Orsay Cedex, France
| | | | - Laura Baciou
- Laboratoire de Chimie Physique UMR 8000, Univ. Paris-Sud, CNRS, Université Paris Saclay, 91405 Orsay Cedex, France.
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17
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18
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Roehlecke C, Schumann U, Ader M, Brunssen C, Bramke S, Morawietz H, Funk RHW. Stress reaction in outer segments of photoreceptors after blue light irradiation. PLoS One 2013; 8:e71570. [PMID: 24039718 PMCID: PMC3770596 DOI: 10.1371/journal.pone.0071570] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 07/07/2013] [Indexed: 12/26/2022] Open
Abstract
The retina is prone to oxidative stress from many factors which are also involved in the pathogenesis of degenerative diseases. In this study, we used the application of blue light as a physiological stress factor. The aim of this study was to identify the major source of intracellular ROS that mediates blue light-induced detrimental effects on cells which may lead to cytotoxicity. We hypothesized that outer segments are the major source of blue light induced ROS generation. In photoreceptors, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzymes and the recently found respiratory chain complexes may represent a major source for reactive oxygen species (ROS), beside mitochondria and chromophores. Therefore, we investigated this hypothesis and analysed the exact localization of the ROS source in photoreceptors in an organotypic culture system for mouse retinas. Whole eyeball cultures were irradiated with visible blue light (405 nm) with an output power of 1 mW/cm2. Blue light impingement lead to an increase of ROS production (detected by H2DCFDA in live retinal explants), which was particularly strong in the photoreceptor outer segments. Nox-2 and Nox-4 proteins are sources of ROS in blue light irradiated photoreceptors; the Nox inhibitor apocynin decreased ROS stimulated by blue light. Concomitantly, enzyme SOD-1, a member of the antioxidant defense system, indicator molecules of protein oxidation (CML) and lipid oxidation (MDA and 4-HNE) were also increased in the outer segments. Interestingly, outer segments showed a mitochondrial-like membrane potential which was demonstrated using two dyes (JC-1 and TMRE) normally exclusively associated with mitochondria. As in mitochondria, these dyes indicated a decrease of the membrane potential in hypoxic states or cell stress situations. The present study demonstrates that ROS generation and oxidative stress occurs directly in the outer segments of photoreceptors after blue light irradiation.
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Affiliation(s)
- Cora Roehlecke
- Institute of Anatomy, Technische Universität (TU) Dresden, Dresden, Germany
- * E-mail:
| | - Ulrike Schumann
- Institute of Anatomy, Technische Universität (TU) Dresden, Dresden, Germany
| | - Marius Ader
- Center for Regenerative Therapies Dresden (CRTD) DFG – Cluster of Excellence, Biotechnology Center, Dresden, Germany
| | - Coy Brunssen
- Division of Vascular Endothelium and Microcirculation, Department of Medicine III, TU Dresden, Dresden, Germany
| | - Silvia Bramke
- Institute of Anatomy, Technische Universität (TU) Dresden, Dresden, Germany
| | - Henning Morawietz
- Center for Regenerative Therapies Dresden (CRTD) DFG – Cluster of Excellence, Biotechnology Center, Dresden, Germany
- Division of Vascular Endothelium and Microcirculation, Department of Medicine III, TU Dresden, Dresden, Germany
| | - Richard H. W. Funk
- Institute of Anatomy, Technische Universität (TU) Dresden, Dresden, Germany
- Center for Regenerative Therapies Dresden (CRTD) DFG – Cluster of Excellence, Biotechnology Center, Dresden, Germany
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Abstract
Reactive oxygen and nitrogen species are currently considered not only harmful byproducts of aerobic respiration but also critical mediators of redox signaling. The molecules and the chemical principles sustaining the network of cellular redox regulated processes are described. Special emphasis is placed on hydrogen peroxide (H(2)O(2)), now considered as acting as a second messenger, and on sulfhydryl groups, which are the direct targets of the oxidant signal. Cysteine residues of some proteins, therefore, act as sensors of redox conditions and are oxidized in a reversible reaction. In particular, the formation of sulfenic acid and disulfide, the initial steps of thiol oxidation, are described in detail. The many cell pathways involved in reactive oxygen species formation are reported. Central to redox signaling processes are the glutathione and thioredoxin systems controlling H(2)O(2) levels and, hence, the thiol/disulfide balance. Lastly, some of the most important redox-regulated processes involving specific enzymes and organelles are described. The redox signaling area of research is rapidly expanding, and future work will examine new pathways and clarify their importance in cellular pathophysiology.
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Affiliation(s)
- Alberto Bindoli
- Institute of Neuroscience (CNR), Department of Biomedical Sciences, University of Padova, Padova, Italy.
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20
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Abstract
Nitric oxide (NO) research has expanded rapidly in the past 20 years, and the role of NO in physiology and pathology has been extensively studied. This review focuses on the pathways of NO synthesis and metabolism in vascular biological systems. Healthy vascular homeostasis is dependent on the integrity of the endothelium, which is a very large dynamic autocrine and paracrine organ with vasodilator, anti-inflammatory, and antithrombotic properties. The importance and relevance of NO signaling is stressed in this review. The potential role of nitrotyrosine formation with vascular pathological conditions is discussed. The use of pharmacologic, biochemical, and molecular biological approaches to characterize, purify, and reconstitute these regulatory pathways should lead to the development of new therapies for various pathological conditions that are characterized by an insufficient production of NO. With more than 77,000 publications in the field of NO signaling, this brief review can only focus on some aspects of the field as it applies to vascular biology. Many molecular targets have been identified for drug development dealing with NO and cyclic guanosine monophosphate formation, metabolism, and function. Many agents have been identified that are in pre-clinical evaluation or in clinical trials. Certainly, many should prove to be important therapeutic additions during the next decade.
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Affiliation(s)
- Ka Bian
- The Institute of Molecular Medicine, The University of Texas-Houston Medical School, Houston, Texas, USA; The Murad Research Institute for Modernized Chinese Medicine and Shanghai University of Traditional Chinese Medicine, Shanghai, China; E-Research Institute of Nitric Oxide and Inflammatory Medicine of Shanghai Universities, Shanghai, China
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21
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Prasad A, Pospišil P. Two-dimensional imaging of spontaneous ultra-weak photon emission from the human skin: role of reactive oxygen species. J Biophotonics 2011; 4:840-849. [PMID: 22012922 DOI: 10.1002/jbio.201100073] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 09/14/2011] [Accepted: 09/30/2011] [Indexed: 05/31/2023]
Abstract
In the human skin, reactive oxygen species (ROS) produced continuously during oxidative metabolic processes (cellular respiration, oxidative burst) are essential for various cellular processes such as defense against infection, cellular signaling and apoptosis. On the other hand, when the formation of ROS exceeds a capacity of the non-enzymatic and the enzymatic antioxidant defense system, ROS cause the damage to the human skin known to initiate premature skin aging and skin cancer. In this study, two-dimensional spontaneous ultra-weak photon emission from the human skin has been measured using a highly sensitive charged coupled device (CCD) camera. It is demonstrated here that two-dimensional ultra-weak photon emission from the human skin increases with the topical application of exogenous ROS in the following order: hydrogen peroxide (H₂O₂) < superoxide anion radical (O₂•⁻) < hydroxyl radical (HO•). We propose here that the two-dimensional ultra-weak photon emission can be used as a non-invasive tool for the spatial and temporal monitoring of oxidative stress in the human skin.
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Affiliation(s)
- Ankush Prasad
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Šlechtitelů 11, 78371 Olomouc, Czech Republic
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22
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Pospíšil P. Enzymatic function of cytochrome b559 in photosystem II. Journal of Photochemistry and Photobiology B: Biology 2011; 104:341-7. [DOI: 10.1016/j.jphotobiol.2011.02.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Revised: 02/10/2011] [Accepted: 02/11/2011] [Indexed: 11/22/2022]
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Affiliation(s)
| | | | - David D. Roberts
- To whom correspondence should be addressed: NIH, Building 10, Room 2A33, 10 Center Dr, MSC1500, Bethesda, Maryland 20892,
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24
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Usui S, Oveson BC, Lee SY, Jo YJ, Yoshida T, Miki A, Miki K, Iwase T, Lu L, Campochiaro PA. NADPH oxidase plays a central role in cone cell death in retinitis pigmentosa. J Neurochem 2009; 110:1028-37. [PMID: 19493169 DOI: 10.1111/j.1471-4159.2009.06195.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Retinitis pigmentosa (RP) is a collection of diseases in which rod photoreceptors die from a variety of mutations. After rods die, the level of tissue oxygen in the outer retina becomes elevated and there is progressive oxidative damage to cones that ultimately triggers apoptosis. In this study, we investigated the hypothesis that NADPH oxidase (Nox) and/or xanthine oxidase serve as critical intermediaries between increased tissue oxygen and the generation of excessive reactive oxygen species that cause oxidative damage to cones. Apocynin, a blocker of Nox, but not allopurinol, a blocker of xanthine oxidase, markedly reduced the superoxide radicals visualized by hydroethidine in the outer retina in the retinal degeneration-1 (rd1(+/+)) model of RP. Compared to rd1(+/+) mice treated with vehicle, those treated with apocynin, but not those treated with allopurinol, had significantly less oxidative damage in the retina measured by ELISA for carbonyl adducts. Apocynin-treated, but not allopurinol-treated, rd1(+/+) mice had preservation of cone cell density, increased mRNA levels for m- and s-cone opsin, and increased mean photopic b-wave amplitude. In Q344ter mice, a model of dominant RP in which mutant rhodopsin is expressed, apocynin treatment preserved photopic electroretinogram b-wave amplitude compared to vehicle-treated controls. These data indicate that Nox, but not xanthine oxidase, plays a critical role in generation of the oxidative stress that leads to cone cell death in RP and inhibition of Nox provides a new treatment strategy.
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Affiliation(s)
- Shinichi Usui
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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25
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Pospísil P. Production of reactive oxygen species by photosystem II. Biochim Biophys Acta 2009; 1787:1151-60. [PMID: 19463778 DOI: 10.1016/j.bbabio.2009.05.005] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Revised: 05/05/2009] [Accepted: 05/07/2009] [Indexed: 11/29/2022]
Abstract
Photosysthetic cleavage of water molecules to molecular oxygen is a crucial process for all aerobic life on the Earth. Light-driven oxidation of water occurs in photosystem II (PSII) - a pigment-protein complex embedded in the thylakoid membrane of plants, algae and cyanobacteria. Electron transport across the thylakoid membrane terminated by NADPH and ATP formation is inadvertently coupled with the formation of reactive oxygen species (ROS). Reactive oxygen species are mainly produced by photosystem I; however, under certain circumstances, PSII contributes to the overall formation of ROS in the thylakoid membrane. Under limitation of electron transport reaction between both photosystems, photoreduction of molecular oxygen by the reducing side of PSII generates a superoxide anion radical, its dismutation to hydrogen peroxide and the subsequent formation of a hydroxyl radical terminates the overall process of ROS formation on the PSII electron acceptor side. On the PSII electron donor side, partial or complete inhibition of enzymatic activity of the water-splitting manganese complex is coupled with incomplete oxidation of water to hydrogen peroxide. The review points out the mechanistic aspects in the production of ROS on both the electron acceptor and electron donor side of PSII.
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Affiliation(s)
- Pavel Pospísil
- Laboratory of Biophysics, Department of Experimental Physics, Faculty of Science, Palacký University, Olomouc, Czech Republic.
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26
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Selemidis S, Sobey CG, Wingler K, Schmidt HH, Drummond GR. NADPH oxidases in the vasculature: Molecular features, roles in disease and pharmacological inhibition. Pharmacol Ther 2008; 120:254-91. [DOI: 10.1016/j.pharmthera.2008.08.005] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Accepted: 08/06/2008] [Indexed: 02/07/2023]
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28
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Abstract
The oxidation chemistry of thiols and disulfides of biologic relevance is described. The review focuses on the interaction and kinetics of hydrogen peroxide with low-molecular-weight thiols and protein thiols and, in particular, on sulfenic acid groups, which are recognized as key intermediates in several thiol oxidation processes. In particular, sulfenic and selenenic acids are formed during the catalytic cycle of peroxiredoxins and glutathione peroxidases, respectively. In turn, these enzymes are in close redox communication with the thioredoxin and glutathione systems, which are the major controllers of the thiol redox state. Oxidants formed in the cell originate from several different sources, but the major producers are NADPH oxidases and mitochondria. However, a different role of the oxygen species produced by these sources is apparent as oxidants derived from NADPH oxidase are involved mainly in signaling processes, whereas those produced by mitochondria induce cell death in pathways including also the thioredoxin system, presently considered an important target for cancer chemotherapy.
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Affiliation(s)
- Alberto Bindoli
- Institute of Neurosciences (CNR) c/o Department of Biological Chemistry, University of Padova (Italy).
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29
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Abstract
NADPH oxidases of the Nox family exist in various supergroups of eukaryotes but not in prokaryotes, and play crucial roles in a variety of biological processes, such as host defense, signal transduction, and hormone synthesis. In conjunction with NADPH oxidation, Nox enzymes reduce molecular oxygen to superoxide as a primary product, and this is further converted to various reactive oxygen species. The electron-transferring system in Nox is composed of the C-terminal cytoplasmic region homologous to the prokaryotic (and organelle) enzyme ferredoxin reductase and the N-terminal six transmembrane segments containing two hemes, a structure similar to that of cytochrome b of the mitochondrial bc(1) complex. During the course of eukaryote evolution, Nox enzymes have developed regulatory mechanisms, depending on their functions, by inserting a regulatory domain (or motif) into their own sequences or by obtaining a tightly associated protein as a regulatory subunit. For example, one to four Ca(2+)-binding EF-hand motifs are present at the N-termini in several subfamilies, such as the respiratory burst oxidase homolog (Rboh) subfamily in land plants (the supergroup Plantae), the NoxC subfamily in social amoebae (the Amoebozoa), and the Nox5 and dual oxidase (Duox) subfamilies in animals (the Opisthokonta), whereas an SH3 domain is inserted into the ferredoxin-NADP(+) reductase region of two Nox enzymes in Naegleria gruberi, a unicellular organism that belongs to the supergroup Excavata. Members of the Nox1-4 subfamily in animals form a stable heterodimer with the membrane protein p22(phox), which functions as a docking site for the SH3 domain-containing regulatory proteins p47(phox), p67(phox), and p40(phox); the small GTPase Rac binds to p67(phox) (or its homologous protein), which serves as a switch for Nox activation. Similarly, Rac activates the fungal NoxA via binding to the p67(phox)-like protein Nox regulator (NoxR). In plants, on the other hand, this GTPase directly interacts with the N-terminus of Rboh, leading to superoxide production. Here I describe the regulation of Nox-family oxidases on the basis of three-dimensional structures and evolutionary conservation.
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Affiliation(s)
- Hideki Sumimoto
- Medical Institute of Bioregulation, Kyushu University, Fukuoka CREST, Japan Science and Technology Agency, Tokyo, Japan.
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30
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Abstract
In recent years, it has become clear that reactive oxygen species (ROS, which include superoxide, hydrogen peroxide, and other metabolites) are produced in biological systems. Rather than being simply a by-product of aerobic metabolism, it is now recognized that specific enzymes--the Nox (NADPH oxidase) and Duox (Dual oxidase) enzymes--seem to have the sole function of generating ROS in a carefully regulated manner, and key roles in signal transduction, immune function, hormone biosynthesis, and other normal biological functions are being uncovered. The prototypical Nox is the respiratory burst oxidase or phagocyte oxidase, which generates large amounts of superoxide and other reactive species in the phagosomes of neutrophils and macrophages, playing a central role in innate immunity by killing microbes. This enzyme system has been extensively studied over the past two decades, and provides a basis for comparison with the more recently described Nox and Duox enzymes, which generate ROS in a variety of cells and tissues. This review first considers the structure and regulation of the respiratory burst oxidase, and then reviews recent studies relating to the regulation of the activity of the novel Nox/Duox enzymes. The regulation of Nox and Duox expression in tissues and by specific stimuli is also considered here. An accompanying review considers biological and pathological roles of the Nox family of enzymes.
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Affiliation(s)
- J David Lambeth
- Department of Pathology and Laboratory Medicine, 148 Whitehead Biomedical Research Building, Emory University, 615 Michael Street, Atlanta, GA 30322, USA.
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Kochel B, Vocks A, Arnhold J. Chemiluminescent picture of diphenyleneiodonium-inhibited NADPH oxidase: a bimodal process and its logistic-exponential model-based description. LUMINESCENCE 2007; 22:275-93. [PMID: 17373025 DOI: 10.1002/bio.961] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 11/07/2022]
Abstract
A chemiluminescence (CL) study of diphenyleneiodonium-inhibited NADPH oxidase was performed on a cellular system containing neutrophils stimulated by phorbol myristate acetate, indicating a complex bimodal structure of CL processes corresponding to different stages of the inhibition. The complex structure of these processes was described by a superposition of two logistic-exponential (LE) models, characterizing these processes as bimodal ones. To determine the mechanistic foundation of the LE model-described processes, a generalized form of the second-order dynamic system of CL reactions, the solution to which corresponds to the LE model, was constructed. The diphenyleneiodonium effects on neutrophil NADPH oxidase were separated from the total bimodal CL of the whole measurement system by the use of difference CL processes. These difference processes were also found to be bimodal; thus, inhibitor-induced reduction of CL could be described by a second-order dynamic system. The rate constants and initial concentrations in this dynamic system were determined by the least squares method applied to numerical solutions approximating the difference processes. Using interrelations between the parameters of the dynamic system, cooperative effects in the inhibitor reactions with NADPH oxidase were found and described quantitatively. Other evidences of cooperativity were obtained from integral characteristics of the CL reduction process, i.e. dose-response and progress curves, determined by numerical integration of the LE models constituting the superposition. On this basis, it was also possible to detect a specific binding of the inhibitor to the enzyme. Finally, putative reaction mechanisms suggested by the model obtained were considered and compared with those known at present.
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Affiliation(s)
- Bonawentura Kochel
- Department of Toxicology, Wroclaw Medical University, Traugutta 57/59, PL-50417 Wroclaw, Poland.
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32
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Abstract
The role of nitric oxide (NO) in cellular signaling has become one of the most rapidly growing areas in biology during the past two decades. As a gas and free radical with an unshared electron, nitric oxide participates in various biological processes. The interaction between NO and proteins may be roughly divided into two categories. In many instances, NO mediates its biological effects by activating guanylyl cyclase and elevates intracellular cyclic GMP synthesis from GTP. However, the list of cGMP-independent effects of NO is also growing at a rapid rate. In this review, the importance and relevance of nitrotyrosine formation are stressed. The utilization of intact cell cultures, tissues, and cell-free preparations along with the use of pharmacological, biochemical, and molecular biological approaches to characterize, purify, and reconstitute these NO regulatory pathways could lead to the development of new therapies for various pathological conditions that are characterized by unbalanced production of NO.
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Affiliation(s)
- Ka Bian
- The Institute of Molecular Medicine, The University of Texas-Houston Medical School, Houston, TX 77030, USA.
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Marchal S, Gorren ACF, Andersson KK, Lange R. Hunting oxygen complexes of nitric oxide synthase at low temperature and high pressure. Biochem Biophys Res Commun 2005; 338:529-35. [PMID: 16126163 DOI: 10.1016/j.bbrc.2005.08.090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Indexed: 11/28/2022]
Abstract
The reaction of nitric oxide synthase (NOS) with oxygen is fast and takes place within several steps, separated by ephemeral intermediates. The use of extreme experimental conditions, such as low temperature and high pressure, associated to rapid kinetic analysis, has proven to be a convenient tool to study this complex reaction. Stopped-flow experiments under high pressure indicated that oxygen binding occurred in more than one step. This was further corroborated by the detection of two short-lived oxy-compounds, differing in their spectral and electronic properties. Oxy-I resembles the ferrous oxygen complex known for cytochrome P450, whereas oxy-II appears to be locked in the superoxide form. Subzero temperature spectroscopy, together with an analytical separation method, revealed that the subsequent one-electron reduction of the oxygen complex is carried out by the NOS cofactor tetrahydrobiopterin (BH4). The low-temperature stabilized oxidation product of BH4 was found to be a protonated BH3 radical. Finally, work in the presence of a BH4 analog indicated that proton transfer to the activated oxygen complex is a second essential function of BH4.
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Affiliation(s)
- Stéphane Marchal
- INSERM U710, Place Eugène Bataillon, Université Montpellier II, Montpellier, France
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Groemping Y, Rittinger K. Activation and assembly of the NADPH oxidase: a structural perspective. Biochem J 2005; 386:401-16. [PMID: 15588255 PMCID: PMC1134858 DOI: 10.1042/bj20041835] [Citation(s) in RCA: 421] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Revised: 12/02/2004] [Accepted: 12/10/2004] [Indexed: 11/17/2022]
Abstract
The NADPH oxidase of professional phagocytes is a crucial component of the innate immune response due to its fundamental role in the production of reactive oxygen species that act as powerful microbicidal agents. The activity of this multi-protein enzyme is dependent on the regulated assembly of the six enzyme subunits at the membrane where oxygen is reduced to superoxide anions. In the resting state, four of the enzyme subunits are maintained in the cytosol, either through auto-inhibitory interactions or through complex formation with accessory proteins that are not part of the active enzyme complex. Multiple inputs are required to disrupt these inhibitory interactions and allow translocation to the membrane and association with the integral membrane components. Protein interaction modules are key regulators of NADPH oxidase assembly, and the protein-protein interactions mediated via these domains have been the target of numerous studies. Many models have been put forward to describe the intricate network of reversible protein interactions that regulate the activity of this enzyme, but an all-encompassing model has so far been elusive. An important step towards an understanding of the molecular basis of NADPH oxidase assembly and activity has been the recent solution of the three-dimensional structures of some of the oxidase components. We will discuss these structures in the present review and attempt to reconcile some of the conflicting models on the basis of the structural information available.
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Key Words
- nadph oxidase
- oxidase assembly
- phosphorylation
- protein–protein interaction
- reactive oxygen species
- ac, acidic cluster
- bc, basic cluster
- cgd, chronic granulomatous disease
- gap, gtpase-activating protein
- gdi, gdp-dissociation inhibitor
- gef, guanine-nucleotide-exchange factor
- gst, glutathione s-transferase
- itc, isothermal titration calorimetry
- mapk, mitogen-activated protein kinase
- pb1, phox and bem1
- pc, phox and cdc24
- phox, phagocytic oxidase
- ppii helix, polyproline type ii helix
- px, phox homology
- prr, proline-rich region
- rms, root mean square
- ros, reactive oxygen species
- sh3, src homology 3
- spr, surface plasmon resonance
- tpr, tetratricopeptide repeat
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Affiliation(s)
- Yvonne Groemping
- *Abteilung Biomolekulare Mechanismen, Max-Planck-Institut für medizinische Forschung, Heidelberg, Germany
| | - Katrin Rittinger
- †Division of Protein Structure, National Institute for Medical Research, London, U.K
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35
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Abstract
Neutrophils play an essential role in the body's innate defense against pathogens and are one of the primary mediators of the inflammatory response. To defend the host, neutrophils use a wide range of microbicidal products, such as oxidants, microbicidal peptides, and lytic enzymes. The generation of microbicidal oxidants by neutrophils results from the activation of a multiprotein enzyme complex known as the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which is responsible for transferring electrons from NADPH to O2, resulting in the formation of superoxide anion. During oxidase activation, cytosolic oxidase proteins translocate to the phagosome or plasma membrane, where they assemble around a central membrane-bound component known as flavocytochrome b. This process is highly regulated, involving phosphorylation, translocation, and multiple conformational changes. Originally, it was thought that the NADPH oxidase was restricted to phagocytes and used solely in host defense. However, recent studies indicate that similar NADPH oxidase systems are present in a wide variety of nonphagocytic cells. Although the nature of these nonphagocyte NADPH oxidases is still being defined, it is clear that they are functionally distinct from the phagocyte oxidases. It should be noted, however, that structural features of many nonphagocyte oxidase proteins do seem to be similar to those of their phagocyte counterparts. In this review, key structural and functional features of the neutrophil NADPH oxidase and its protein components are described, including a consideration of transcriptional and post-translational regulatory features. Furthermore, relevant details about structural and functional features of various nonphagocyte oxidase proteins will be included for comparison.
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Affiliation(s)
- Mark T Quinn
- Department of Veterinary Molecular Biology, Montana State University, Bozeman 59717-3610, USA.
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Cross AR, Segal AW. The NADPH oxidase of professional phagocytes--prototype of the NOX electron transport chain systems. Biochim Biophys Acta 2004; 1657:1-22. [PMID: 15238208 PMCID: PMC2636547 DOI: 10.1016/j.bbabio.2004.03.008] [Citation(s) in RCA: 325] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2003] [Revised: 03/16/2004] [Accepted: 03/16/2004] [Indexed: 02/06/2023]
Abstract
The NADPH oxidase is an electron transport chain in "professional" phagocytic cells that transfers electrons from NADPH in the cytoplasm, across the wall of the phagocytic vacuole, to form superoxide. The electron transporting flavocytochrome b is activated by the integrated function of four cytoplasmic proteins. The antimicrobial function of this system involves pumping K+ into the vacuole through BKCa channels, the effect of which is to elevate the vacuolar pH and activate neutral proteases. A number of homologous systems have been discovered in plants and lower animals as well as in man. Their function remains to be established.
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Affiliation(s)
- Andrew R. Cross
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Anthony W. Segal
- Centre for Molecular Medicine, Department of Medicine, University College London, 5 University Street, London WC1E 6JJ, UK
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Zhu H, Larade K, Jackson TA, Xie J, Ladoux A, Acker H, Berchner-Pfannschmidt U, Fandrey J, Cross AR, Lukat-Rodgers GS, Rodgers KR, Bunn HF. NCB5OR is a novel soluble NAD(P)H reductase localized in the endoplasmic reticulum. J Biol Chem 2004; 279:30316-25. [PMID: 15131110 PMCID: PMC3045664 DOI: 10.1074/jbc.m402664200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [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
The NAD(P)H cytochrome b5 oxidoreductase, Ncb5or (previously named b5+b5R), is widely expressed in human tissues and broadly distributed among the animal kingdom. NCB5OR is the first example of an animal flavohemoprotein containing cytochrome b5 and chrome b5 reductase cytodomains. We initially reported human NCB5OR to be a 487-residue soluble protein that reduces cytochrome c, methemoglobin, ferricyanide, and molecular oxygen in vitro. Bioinformatic analysis of genomic sequences suggested the presence of an upstream start codon. We confirm that endogenous NCB5OR indeed has additional NH2-terminal residues. By performing fractionation of subcellular organelles and confocal microscopy, we show that NCB5OR colocalizes with calreticulin, a marker for endoplasmic reticulum. Recombinant NCB5OR is soluble and has stoichiometric amounts of heme and flavin adenine dinucleotide. Resonance Raman spectroscopy of NCB5OR presents typical signatures of a six-coordinate low-spin heme similar to those found in other cytochrome b5 proteins. Kinetic measurements showed that full-length and truncated NCB5OR reduce cytochrome c actively in vitro. However, both full-length and truncated NCB5OR produce superoxide from oxygen with slow turnover rates: kcat = approximately 0.05 and approximately 1 s(-1), respectively. The redox potential at the heme center of NCB5OR is -108 mV, as determined by potentiometric titrations. Taken together, these data suggest that endogenous NCB5OR is a soluble NAD(P)H reductase preferentially reducing substrate(s) rather than transferring electrons to molecular oxygen and therefore not an NAD(P)H oxidase for superoxide production. The subcellular localization and redox properties of NCB5OR provide important insights into the biology of NCB5OR and the phenotype of the Ncb5or-null mouse.
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Affiliation(s)
- Hao Zhu
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
- To whom correspondence may be addressed: Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, 221 Longwood Ave., Boston, MA 02115. Tel.: 617-278-0870; Fax: 617-739-0748;
| | - Kevin Larade
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Timothy A. Jackson
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Jianxin Xie
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Annie Ladoux
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Helmut Acker
- Labor fuer optische Systemphysiologie, Max-Planck-Institut fuer molekulare Physiologie, 44227 Dortmund, Germany
| | - Utta Berchner-Pfannschmidt
- Labor fuer optische Systemphysiologie, Max-Planck-Institut fuer molekulare Physiologie, 44227 Dortmund, Germany
- Universitätsklinikum Essen, Institut fuer Physiologie, 45122 Essen, Germany
| | - Joachim Fandrey
- Universitätsklinikum Essen, Institut fuer Physiologie, 45122 Essen, Germany
| | - Andrew R. Cross
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037
| | | | - Kenton R. Rodgers
- Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105-5516
| | - H. Franklin Bunn
- Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115
- To whom correspondence may be addressed: Hematology Division, Brigham and Women’s Hospital, Harvard Medical School, 221 Longwood Ave., Boston, MA 02115. Tel.: 617-732-5841; Fax: 617-739-0748;
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38
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Abstract
The phagocyte NADPH oxidase helps kill pathogens by producing superoxide anion, O2-. This enzyme is electrogenic because it translocates electrons across the membrane, generating an electron current, Ie. Using the permeabilized patch voltage-clamp technique, we studied the temperature dependence of Ie in human eosinophils stimulated by phorbol myristate acetate (PMA) from room temperature to >37 degrees C. For comparison, NADPH oxidase activity was assessed by cytochrome c reduction. The intrinsic temperature dependence of the assembled, functioning NADPH oxidase complex measured during rapid temperature increases to 37 degrees C was surprisingly weak: the Arrhenius activation energy Ea was only 14 kcal mol(-1) (Q10, 2.2). In contrast, steady-state NADPH oxidase activity was strongly temperature dependent at 20-30 degrees C, with Ea 25.1 kcal mol(-1) (Q10, 4.2). The maximum Ie measured at 34 degrees C was -30.5 pA. Above 30 degrees C, the temperature dependence of both Ie and O2- production was less pronounced. Above 37 degrees C, Ie was inhibited reversibly. After rapid temperature increases, a secondary increase in Ie ensued, suggesting that high temperature promotes assembly of additional NADPH oxidase complexes. Evidently, about twice as many NADPH oxidase complexes are active near 37 degrees C than at 20 degrees C. Thus, the higher Q10 of steady-state Ie reflects both increased activity of each NADPH oxidase complex and preferential assembly of NADPH oxidase complexes at high temperature. In summary, NADPH oxidase activity in intact human eosinophils is maximal precisely at 37 degrees C.
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Affiliation(s)
- Deri Morgan
- Department of Molecular Biophysics and Physiology, Rush Presbyterian St Luke's Medical Center, Chicago, IL 60612, USA
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39
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Abstract
Recently, substantial evidence has emerged that revealed a very close association between the formation of nitrotyrosine and the presence of activated granulocytes containing peroxidases, such as myeloperoxidase. Peroxidases share heme-containing homology and can use H(2)O(2) to oxidize substrates. Heme is a complex of iron with protoporphyrin IX, and the iron-containing structure of heme has been shown to be an oxidant in several model systems where the prooxidant effects of free iron, heme, and hemoproteins may be attributed to the formation of hypervalent states of the heme iron. In the current study, we have tested the hypothesis that free heme and iron play a crucial role in NO(2)-Tyr formation. The data from our study indicate that: (i) hemeiron catalyzes nitration of tyrosine residues by using hydrogen peroxide and nitrite, a reaction that revealed the mechanism underlying the protein nitration by peroxidase, H(2)O(2), and NO(2)(-); (ii) H(2)O(2) plays a key role in the protein oxidation that forms the basis for the protein nitration, whereas nitrite is an essential element that facilitates nitration by the heme(Fe), H(2)O(2), and the NO(2)(-) system; (iii) the formation of a Fe(IV) hypervalent compound may be essential for heme(Fe)-catalyzed nitration, whereas O(2)(*-) (ONOO(-) formation), (*)OH (Fenton reaction), and compound III are unlikely to contribute to the reaction; and (iv) hemoprotein-rich tissues such as cardiac muscle are vulnerable to protein nitration in pathological conditions characterized by the overproduction of H(2)O(2) and NO(2)(-), or nitric oxide.
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Affiliation(s)
- Ka Bian
- Department of Integrative Biology and Pharmacology, Institute of Molecular Medicine, University of Texas Medical School, 6431 Fannin, Houston, TX 77030, USA
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40
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Foubert TR, Bleazard JB, Burritt JB, Gripentrog JM, Baniulis D, Taylor RM, Jesaitis AJ. Identification of a spectrally stable proteolytic fragment of human neutrophil flavocytochrome b composed of the NH2-terminal regions of gp91(phox) and p22(phox). J Biol Chem 2001; 276:38852-61. [PMID: 11504718 DOI: 10.1074/jbc.m104373200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [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
A heme-bearing polypeptide core of human neutrophil flavocytochrome b(558) was isolated by applying high performance, size exclusion, liquid chromatography to partially purified Triton X-100-solubilized flavocytochrome b that had been exposed to endoproteinase Glu-C for 1 h. The fragment was composed of two polypeptides of 60-66 and 17 kDa by SDS-polyacrylamide gel electrophoresis and retained a native heme absorbance spectrum that was stable for several days when stored at 4 degrees C in detergent-containing buffer. These properties suggested that the majority of the flavocytochrome b heme environment remained intact. Continued digestion up to 4.5 h yielded several heme-associated fragments that were variable in composition between experiments. Digestion beyond 4.5 h resulted in a gradual loss of recoverable heme. N-Linked deglycosylation and reduction and alkylation of the 1-h digestion fragment did not affect the electrophoretic mobility of the 17-kDa fragment but reduced the 60-66-kDa fragment to 39 kDa. Sequence and immunoblot analyses identified the fragments as the NH(2)-terminal 320-363 amino acid residues of gp91(phox) and the NH(2)-terminal 169-171 amino acid residues of p22(phox). These findings provide direct evidence that the primarily hydrophobic NH(2)-terminal regions of flavocytochrome b are responsible for heme ligation.
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Affiliation(s)
- T R Foubert
- Department of Microbiology, Montana State University, Bozeman, Montana 59717-3520, USA
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41
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Metzler DE, Metzler CM, Sauke DJ. Electron Transport, Oxidative Phosphorylation, and Hydroxylation. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50021-0] [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: 11/28/2022]
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42
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Gibney BR, Isogai Y, Rabanal F, Reddy KS, Grosset AM, Moser CC, Dutton PL. Self-assembly of heme A and heme B in a designed four-helix bundle: implications for a cytochrome c oxidase maquette. Biochemistry 2000; 39:11041-9. [PMID: 10998241 DOI: 10.1021/bi000925r] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [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: 11/30/2022]
Abstract
Heme A, a prosthetic group of cytochrome c oxidase [EC 1.9.3.1], has been introduced into two de novo designed four helix bundle proteins, [H10A24](2) and [H10H24](2), known to bind 2-4 equiv of heme B, respectively [Robertson, D. E., Farid, R. S., Moser, C. C., Mulholland, S. E., Pidikiti, R., Lear, J. D., Wand, A., J., DeGrado, W. F., and Dutton, P. L. (1994) Nature 368, 425-432]. [H10A24](2), [Ac-CGGGELWKL x HEELLKK x FEELLKL x AEERLKK x L-CONH(2)](2)(2), binds two heme A molecules per four-helix unit via bis-histidine ligation at the 10,10' positions with measured K(d) values of <0.1 and 5 nM, values much lower than those measured for heme B (K(d) values of 50 and 800 nM). The heme A-protein complex, [heme A-H10A24](2), exhibits well-defined absorption spectra in both the ferric and ferrous states, and an electron paramagnetic resonance spectrum characteristic of a low spin heme in the ferric form. A single midpoint redox potential (E(m8)) was determined for [heme A-H10A24](2) at -45 mV (vs SHE), which is significantly higher than that of the protein bound heme B (-130 and -200 mV). The observation of a single midpoint redox potential for [heme A-H10A24](2) and a pair of midpoints for [heme B-H10A24](2) indicates that the di-alpha-helical monomers are oriented in an anti topology (disulfides on opposite sides of bundle) in the former (lacking heme-heme electrostatic interaction) and syn in the latter. A mixture of global topologies was indicated by the potentiometric titration of the related [heme A-H10H24](2) which possess two distinct reduction potentials of +41 (31%) and -65 mV (69%). Self-assembly of the mixed cofactor heme A-heme B-[H10A24](2) was accomplished by addition of a single equivalent of each heme A and heme B to [H10A24](2). The single midpoint redox potential of heme B, E(m8) = -200 mV, together with the split midpoint redox potential of heme A in heme A-heme B-[H10A24](2), E(m8) = +28 mV (33%) and -65 mV (67%), indicated the existence of both syn and anti topologies of the two di-alpha-helical monomers in this four helix bundle. Synthesis of the mixed cofactor [heme A-heme B-H10H24](2) was accomplished by addition of a 2 equiv of each heme A and heme B to [H10H24](2) and potentiometry indicated the pair of hemes B resided in the 10,10' sites and heme A occupied the 24,24' sites. The results indicate that heme peripheral structure controls the orientation of the di-alpha-helical monomers in the four-helix bundle which are interchangeable between syn and anti topologies. In the reduced form, [heme A-H10A24](2), reacts quantitatively to form [carbonmonoxy-heme A-H10A24](2) as evidenced by optical spectroscopy. The synthetic [heme A-H10A24](2) can be enzymatically reduced by NAD(P)H with natural reductases under anaerobic conditions, and reversibly oxidized by dioxygen to the ferric form.
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Affiliation(s)
- B R Gibney
- The Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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43
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Hoshino M, Baba T. Laser Photolysis of Iron(III) Tetraphenylporphyrin in Methanol. A Kinetic Study on the Formation of the Superoxide Anion Radical from the Dioxygen Adduct of Iron(II) Tetraphenylporphyrin. J Am Chem Soc 1998. [DOI: 10.1021/ja9806783] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mikio Hoshino
- The Institute of Physical and Chemical Research Wako, Saitama 351, Japan
| | - Tomoya Baba
- The Institute of Physical and Chemical Research Wako, Saitama 351, Japan
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44
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Affiliation(s)
- Masanori Sono
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
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45
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Doussière J, Gaillard J, Vignais PV. Electron transfer across the O2- generating flavocytochrome b of neutrophils. Evidence for a transition from a low-spin state to a high-spin state of the heme iron component. Biochemistry 1996; 35:13400-10. [PMID: 8873608 DOI: 10.1021/bi960916b] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [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: 02/02/2023]
Abstract
The NADPH oxidase complex of activated neutrophils consists of a membrane-bound flavocytochrome b and cytosolic activation factors. Despite its ability to react with O2, the heme b component of the flavocytochrome is insensitive to cyanide and CO2, and slowly reactive to butyl isocyanide. We report here that arachidonic acid, an anionic amphophil which elicits oxidase activation in a cell-free system induces a transition of the heme iron of the neutrophil flavocytochrome b from a low-spin hexacoordinated state to a high-spin pentacoordinated state and promotes the binding of butyl isocyanide to the heme b. Low-temperature EPR spectra of air-oxidized flavocytochrome b either purified or in its membrane-bound form showed a low-spin signal at g = 3.26 and a high-spin signal at g = 6.0. Upon addition of arachidonic acid, the g = 3.26 signal vanished; a low-spin signal at g = 2.23 appeared, and the signal at g = 6.0 progressively increased. The subsequent addition of butyl isocyanide resulted in the decrease of the g = 6.0 and g = 2.23 signals and in the appearance of a new low-spin signal at g = 2.33. Consistent with the EPR results, upon addition of arachidonic acid to oxidized flavocytochrome b, a 2.5 nm blue shift of the Soret peak was detected in low-temperature optical spectra. The subsequent addition of butyl isocyanide resulted in the emergence of a peak at 432 nm reflecting the formation of a butyl isocyanide-oxidized heme b complex. In the case of sodium dithionite-reduced flavocytochrome b, arachidonic acid promoted the binding of butyl isocyanide to the reduced heme b, as shown by the emergence of a peak at 434 nm and the decrease of the alpha band at 558 nm. The same promoting effect was encountered with sodium dodecyl sulfate, an anionic amphophil capable of eliciting oxidase activation like arachidonic acid. In contrast to arachidonic acid, arachidonic acid methyl ester was ineffective and counteracted the effect of arachidonic acid. Butyl isocyanide added to intact neutrophils was found to bind to heme b, only after the cells have been activated. These data demonstrate the transient accumulation of a pentacoordinated form of the heme iron of flavocytochrome b under in vitro and in vivo conditions; the pentacoordinated form of the reduced heme b is postulated to react with O2 to generate the superoxide anion.
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Affiliation(s)
- J Doussière
- Laboratoire de Biochimie (CNRS/URA 1130), Département de Biologie Moléculaire et Structurale, Grenoble, France
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46
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Abstract
Oxygen is poisonous, but we cannot live without it. The high oxidizing potential of oxygen molecules (dioxygen) is a valuable source of energy for the organism and its reactivity is low; that is, spin forbidden. However, the dioxygen itself is a 'free radical' and, especially in the presence of transition metals, it is a major promoter of radical reactions in the cell. Humans survive only by virtue of their elaborate defense mechanisms against oxygen toxicity. Iron is the most abundant transition metal in the human body. Because iron shows wide variation in redox potential with different co-ordination ligands, it may be used as a redox intermediate in many biological mechanism. However, it is precisely this redox activeness that makes iron a key participant in free radical production. The current research on the relationship between iron and cancer is briefly reviewed. Research results are reported here which indicate that iron, when bound to certain ligands, can cause free-radical mediated tissue damage and become carcinogenic. The present study also suggests that iron may also have a significant role in spontaneous human cancer.
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Affiliation(s)
- S Okada
- First Department of Pathology, Okayama University Medical School, Japan
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47
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Abstract
Phagocytic cells such as neutrophils generate superoxide anions (O2-) within phagocytic vacuoles for killing and digesting microorganisms. Here we report the simultaneous observation of morphological changes and O2- generation in single phagocytic cells during phagocytosis. Point stimulation of a cell by contact with an opsonized microelectrode at the cell surface induced significant deformation to engulf the electrode, and also induced the O2- generation which was measured by the electrode. Periodic fluctuations in the magnitude of the O2- generation were observed in the time course. These oscillations may be caused by metabolic regulation of the formation of NADPH, which is the substrate for the O2- generation
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Affiliation(s)
- Y Isogai
- Laboratory of Biophysical Chemistry, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan
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