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| Autor | Karen Bedard, Karl-Heinz Krause |
| Titel | The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology |
| Zeitschrift | Physiological Reviews |
| Herausgeber | American Physiological Society |
| Ausgabe | 87 |
| Jahr | 2007 |
| Seiten | 245–313 |
| DOI | 10.1152/physrev.00044.2005 |
| URL | http://physrev.physiology.org/content/87/1/245.full.pdf |
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| Fußnoten | yes |
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| ROS are oxygen-derived small molecules, including oxygen radicals [superoxide (O2•–), hydroxyl (•OH), peroxyl (RO2•), and alkoxyl (RO•) radicals] and certain non-radicals that are either oxidizing agents and/or are easily converted into radicals, such as hypochlorous acid (HOCl), ozone (O3), singlet oxygen (1O2), and hydrogen peroxide (H2O2). ROS generation is generally a cascade of reactions that starts with the production of superoxide. Superoxide rapidly dismutates to hydrogen peroxide either spontaneously (at low pH) or catalyzed by superoxide dismutase (SOD). Other elements in the cascade of ROS generation include the reaction of superoxide with nitric oxide to form peroxynitrite (ONOO–), the peroxidase-catalyzed formation of hypochlorous acid [(HOCl) from hydrogen peroxide, and the iron-catalyzed Fenton reaction leading to the generation of hydroxyl radical58.]
Thannickal VJ, Fanburg BL. Reactive oxygen species in cell signaling. Am J Physiol Lung Cell Mol Physiol. 2000;279:L1005-1028. |
Reactive oxygen species (ROS) are oxygen-derived small molecules, including oxygen radicals [superoxide (O2•–), hydroxyl (•OH), peroxyl (RO2•), and alkoxyl (RO•)] and certain nonradicals that are either oxidizing agents and/or are easily converted into radicals, such as hypochlorous acid (HOCl), ozone (O3), singlet oxygen (1O2), and hydrogen peroxide (H2O2). Nitrogen-containing oxidants, such as nitric oxide, are called reactive nitrogen species (RNS). ROS generation is generally a cascade of reactions that starts with the production of superoxide. Superoxide rapidly dismutates to hydrogen peroxide either spontaneously, particularly at low pH or catalyzed by superoxide dismutase. Other elements in the cascade of ROS generation include the reaction of superoxide with nitric oxide to form peroxynitrite, the peroxidase-catalyzed formation of hypochlorous acid from hydrogen peroxide, and the iron-catalyzed Fenton reaction leading to the generation of hydroxyl radical (468, 874).
468. Klebanoff SJ. Oxygen metabolism and the toxic properties of phagocytes. Ann Intern Med 93: 480–489, 1980. 874. Thannickal VJ, Fanburg BL. Reactive oxygen species in cell signaling. Am J Physiol Lung Cell Mol Physiol 279: L1005–L1028, 2000. |
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| [Other elements in the cascade of ROS generation include the reaction of superoxide with nitric oxide to form peroxynitrite (ONOO-), the peroxidase-catalyzed formation of hypochlorous acid] (HOCl) from hydrogen peroxide, and the iron-catalyzed Fenton reaction leading to the generation of hydroxyl radical58. ROS avidly interact with a large number of molecules including other small inorganic molecules as well as proteins, lipids, carbohydrates, and nucleic acids. Through such interactions, ROS may irreversibly destroy or alter the function of the target molecule and consequently, ROS have been increasingly identified as major contributors to damage in biological organisms. However, ROS are involved not only in cellular damage and killing of pathogens, but also in a large number of reversible regulatory signalling processes in virtually all cells and tissues59. The physiological generation of ROS can occur as a result of other biological reactions. For example, ROS generation occurs as a byproduct in the mitochondria, peroxisomes, cytochrome P-450, and other cellular elements58. The phagocyte NADPH oxidase was the first identified example of a system that generates ROS not as a byproduct, but rather as the primary function of this enzyme system59.
58. Thannickal VJ, Fanburg BL. Reactive oxygen species in cell signaling. Am J Physiol Lung Cell Mol Physiol. 2000;279:L1005-1028. 59. Bedard K, Krause K-H. The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology. Physiol. Rev. 2007;87:245-313. |
Other elements in the cascade of ROS generation include the reaction of superoxide with nitric oxide to form peroxynitrite, the peroxidase-catalyzed formation of hypochlorous acid from hydrogen peroxide, and the iron-catalyzed Fenton reaction leading to the generation of hydroxyl radical (468, 874).
ROS avidly interact with a large number of molecules including other small inorganic molecules as well as proteins, lipids, carbohydrates, and nucleic acids. Through such interactions, ROS may irreversibly destroy or alter the function of the target molecule. Consequently, ROS have been increasingly identified as major contributors to damage in biological organisms. [...] In fact, ROS are involved not only in cellular damage and killing of pathogens, but also in a large number of reversible regulatory processes in virtually all cells and tissues. [...] [...] The physiological generation of ROS can occur as a byproduct of other biological reactions. ROS generation as a byproduct occurs with mitochondria, peroxisomes, cytochrome P-450, and other cellular elements (50, 307, 314, 356, 588, 636, 715, 791, 874). However, the phagocyte NADPH oxidase was the first identified example of a system that generates ROS not as a byproduct, but rather as the primary function of the enzyme system. [...] 874. Thannickal VJ, Fanburg BL. Reactive oxygen species in cell signaling. Am J Physiol Lung Cell Mol Physiol 279: L1005–L1028, 2000. [...] |
The copied text starts on the previous page: see: Arc/Fragment_021_22. The source is given twice, but still it is not clear to the reader that everything is taken more or less verbatim from the source, including the reference to Thannickal & Fanburg (2000). |
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Table 1 – A: Nox enzymes and subunits: alternative names, chromosomal localization, gene length, number of amino acids, and total number of single-nucleotide polymorphisms (total SNP). B: Tissue distribution of Nox enzymes: Nox enzymes are expressed in a small number of tissues at high levels (readily detected by Northern blotting) but show intermediate- to low-level expression in many other tissues57. 57. Roos D, Bruggena Rv, Meischl C. Oxidative killing of microbes by neutrophils. Microbes and Infection. 2003;5:1307-1315. |
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Alternative names, chromosomal localization, gene length, number of amino acids, total number of single-nucleotide polymorphisms (total SNP), number of coding nonsynonymous single-nucleotide polymorphisms (cnSNP), amino acid changes in cnSNPs, and nucleotide substitutions in cnSNPs are shown. The number of SNPs is based on presently available NCBI databank entries. The position of the nucleotide substitution is given relative to the start codon (207). * C214T in p22phox was originally called C242T (411), a name still widely used in the literature. [page 252]
NOX enzymes are expressed in a small number of tissues at high levels (readily detected by Northern blotting) but show intermediate- to low-level expression in many other tissues. 207. Den Dunnen JT, Antonarakis SE. Nomenclature for the description of human sequence variations. Hum Genet 109: 121–1 411. Inoue N, Kawashima S, Kanazawa K, Yamada S, Akita H, Yokoyama M. Polymorphism of the NADH/NADPH oxidase p22phox gene in patients with coronary artery disease. Circulation 97: 135–137, 1998. |
The two tables are copied verbatim from the source, which is not referenced. The source given, Roos et al. (2003). does not contain any of the copied material. |
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| The activation of Nox2 occurs through a complex series of protein/protein interactions, where Nox2 constitutively associates with p22phox, forming a heterodimeric complex known as cytochrome b558 (Cyt b558)58. NADPH oxidase activation requires translocation of cytosolic factors to the Nox2/p22phox complex and the present working model functions in the following way (Fig. 4): First, phosphorylation of p47phox leads to a conformational change allowing its interaction with p22phox. It is thought that p47phox organizes the translocation of other cytosolic factors, hence its designation as “organizer subunit.” The relocalization of p47phox to the membrane brings the “activator subunit” p67phox into contact with Nox2 and also brings the small subunit p40phox to the complex. Finally, the GTPase Rac interacts with Nox2 via a two-step mechanism involving an initial direct interaction with Nox2, followed by a subsequent interaction with p67phox. Once assembled, the complex is active and generates superoxide by transferring an electron from NADPH in the cytosol to oxygen on the luminal or extracellular space59.
Fig. 4 - Assembly of the phagocyte NADPH oxidase Nox2. Nox2 and p22phox are found primarily in the membrane of intracellular vesicles. Upon activation, there is an exchange of GDP for GTP on Rac leading to its activation. Phosphorylation of the cytosolic p47phox subunit leads to conformational changes allowing interaction with p22phox. The movement of p47phox brings with it the other cytoplasmic subunits, p67phox and p40phox, to form the active Nox2 enzyme complex. Once activated, there is a fusion of Nox2-containing vesicles with the plasma membrane or the phagosomal membrane. The active enzyme complex transports electrons from cytoplasmic NADPH to extracellular or phagosomal oxygen to generate superoxide57 57. Roos D, Bruggena Rv, Meischl C. Oxidative killing of microbes by neutrophils. Microbes and Infection. 2003;5:1307-1315. 58. Thannickal VJ, Fanburg BL. Reactive oxygen species in cell signaling. Am J Physiol Lung Cell Mol Physiol. 2000;279:L1005-1028. 59. Bedard K, Krause K-H. The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology. Physiol. Rev. 2007;87:245-313. |
The activation of NOX2 occurs through a complex series of protein/protein interactions (Fig. 2; for more detailed recent reviews, see Refs. 328, 652, 844). NOX2 constitutively associates with p22phox. [...] Activation of NOX2 requires translocation of cytosolic factors to the NOX2/p22phox complex (Fig. 3). The present working model is as follows. Phosphorylation of p47phox leads to a conformational change allowing its interaction with p22phox(327, 843). It is thought that p47phox organizes the translocation
[page 250]
FIG. 3. Assembly of the phagocyte NADPH oxidase NOX2. [...] In resting neutrophil granulocytes, NOX2 and p22phox are found primarily in the membrane of intracellular vesicles. They exist in close association, costabilizing one another. Upon activation, there is an exchange of GDP for GTP on Rac leading to its activation. Phosphorylation of the cytosolic p47phox subunit leads to conformational changes allowing interaction with p22phox. The movement of p47phox brings with it the other cytoplasmic subunits, p67phox and p40phox, to form the active NOX2 enzyme complex. Once activated, there is a fusion of NOX2-containing vesicles with the plasma membrane or the phagosomal membrane. The active enzyme complex transports electrons from cytoplasmic NADPH to extracellular or phagosomal oxygen to generate superoxide (O2-). of other cytosolic factors, hence its designation as “organizer subunit.” The localization of p47phox to the membrane brings the “activator subunit” p67phox into contact with NOX2 (342) and also brings the small subunit p40phox to the complex. Finally, the GTPase Rac interacts with NOX2 via a two-step mechanism involving an initial direct interaction with NOX2 (214), followed by a subsequent interaction with p67phox (476, 508). Once assembled, the complex is active and generates superoxide by transferring an electron from NADPH in the cytosol to oxygen on the luminal or extracellular space. [...] |
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| Through such interactions, ROS may irreversibly destroy or alter the function of the target molecule and consequently, ROS have been identified as major contributors to damage in biological organisms. | Through such interactions, ROS may irreversibly destroy or alter the function of the target molecule. Consequently, ROS have been increasingly identified as major contributors to damage in biological organisms. |
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