1
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Wei CC, Razzak AA, Ghasemi H, Khedri R, Fraase A. Ca 2+ binding shifts dimeric dual oxidase's truncated EF-hand domain to monomer. Biophys Chem 2024; 312:107271. [PMID: 38852484 DOI: 10.1016/j.bpc.2024.107271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 04/17/2024] [Accepted: 05/22/2024] [Indexed: 06/11/2024]
Abstract
Hydrogen peroxide, produced by Dual Oxidase (Duox), is essential for thyroid hormone synthesis. Duox activation involves Ca2+ binding to its EF-hand Domain (EFD), which contains two EF-hands (EFs). In this study, we characterized a truncated EFD using spectrometry, calorimetry, electrophoretic mobility, and gel filtration to obtain its Ca2+ binding thermodynamic and kinetics, as well as to assess the associated conformational changes. Our results revealed that its 2nd EF-hand (EF2) exhibits a strong exothermic Ca2+ binding (Ka = 107 M-1) while EF1 shows a weaker binding (Ka = 105 M-1), resulting in the burial of its negatively charged residues. The Ca2+ binding to EFD results in a stable structure with a melting temperature shifting from 67 to 99 °C and induces a structural transition from a dimeric to monomeric form. EF2 appears to play a role in dimer formation in its apo form, while the hydrophobic exposure of Ca2+-bound-EF1 is crucial for dimer formation in its holo form. The result is consistent with structures obtained from Cryo-EM, indicating that a stable structure of EFD with hydrophobic patches upon Ca2+ binding is vital for its Duox's domain-domain interaction for electron transfer.
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Affiliation(s)
- Chin-Chuan Wei
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA; Department of Pharmaceutical Sciences, College of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA.
| | - Amena Abdul Razzak
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Hadis Ghasemi
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Rahil Khedri
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Alexandria Fraase
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
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2
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Miyano K, Kajikawa M. Ca 2+ -binding-region-dependent cell surface localization of NADPH oxidase Nox5. FEBS Lett 2023; 597:702-713. [PMID: 36653838 DOI: 10.1002/1873-3468.14577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/29/2022] [Accepted: 01/08/2023] [Indexed: 01/20/2023]
Abstract
Six gene splice variants of superoxide-generating NADPH oxidase 5 (Nox5) have been identified in humans, and they differ in the sequence of their N-terminal cytoplasmic domains, which comprise four EF-hand motifs. Here, we demonstrated that the Ca2+ -dependent association and dissociation between the N- and C-terminal cytoplasmic domains of the Nox5β variant are affected by the alanine substitution of the conserved Ile-113 or Leu-115 at the connecting loop between the third and fourth EF-hand motifs. These substitutions impair the cell surface localization of Nox5β. In addition, the Nox5ε/S variant, lacking all EF-hand motifs, does not localize to the plasma membrane. Thus, the Ca2+ -sensitive intramolecular interaction determines the Nox5 subcellular localization, that is, whether Nox5 variants generate superoxide in the extracellular or intracellular space.
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Affiliation(s)
- Kei Miyano
- Department of Natural Sciences, Kawasaki Medical School, Okayama, Japan
- Department of Biochemistry, Kawasaki Medical School, Okayama, Japan
| | - Mizuho Kajikawa
- Laboratory of Microbiology, Showa Pharmaceutical University, Tokyo, Japan
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3
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Conner GE. Regulation of dual oxidase hydrogen peroxide synthesis results in an epithelial respiratory burst. Redox Biol 2021; 41:101931. [PMID: 33743241 PMCID: PMC8010520 DOI: 10.1016/j.redox.2021.101931] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/19/2021] [Accepted: 03/01/2021] [Indexed: 12/23/2022] Open
Abstract
Redox status is a central determinant of cellular activities and redox imbalance is correlated with numerous diseases. NADPH oxidase activity results in formation of H2O2, that, in turn, sets cellular redox status, a key regulator of cellular homeostasis and responses to external stimuli. Hydrogen peroxide metabolism regulates cell redox status by driving changes in protein cysteine oxidation often via cycling of thioredoxin/peroxiredoxin and glutathione; however, regulation of enzymes controlling synthesis and utilization of H2O2 is not understood beyond broad outlines. The data presented here show that calcium-stimulated epithelial Duox H2O2 synthesis is transient, independent of intracellular calcium renormalization, H2O2 scavenging by antioxidant enzymes, or substrate depletion. The data support existence of a separate mechanism that restricts epithelial H2O2 synthesis to a burst and prevents harmful changes in redox tone following continuous stimulation. Elucidation of this H2O2 synthesis tempering mechanism is key to understanding cellular redox regulation and control of downstream effectors, and this observation provides a starting point for investigation of the mechanism that controls H2O2-mediated increases in redox tone. DUOX1 and DUOX2 H2O2 synthesis decreases after calcium stimulation even in the continued presence of elevated calcium. Decreasing DUOX1 and DUOX2 activity in elevated calcium is not due to substrate depletion or assay limitations. Calcium activation of DUOX1 and DUOX2 H2O2 synthesis results in a respiratory burst independent of calcium renormalization. The data support a mechanism that limits Duox H2O2 synthesis in the presence of continually elevated calcium stimulation.
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Affiliation(s)
- Gregory E Conner
- Department of Cell Biology, University of Miami Miller School of Medicine, 1600 NW 10(th) Avenue, Miami, Fl, 33136, USA.
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4
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Millana Fañanás E, Todesca S, Sicorello A, Masino L, Pompach P, Magnani F, Pastore A, Mattevi A. On the mechanism of calcium-dependent activation of NADPH oxidase 5 (NOX5). FEBS J 2020; 287:2486-2503. [PMID: 31785178 PMCID: PMC7317449 DOI: 10.1111/febs.15160] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 11/27/2019] [Indexed: 12/15/2022]
Abstract
It is now accepted that reactive oxygen species (ROS) are not only dangerous oxidative agents but also chemical mediators of the redox cell signaling and innate immune response. A central role in ROS-controlled production is played by the NADPH oxidases (NOXs), a group of seven membrane-bound enzymes (NOX1-5 and DUOX1-2) whose unique function is to produce ROS. Here, we describe the regulation of NOX5, a widespread family member present in cyanobacteria, protists, plants, fungi, and the animal kingdom. We show that the calmodulin-like regulatory EF-domain of NOX5 is partially unfolded and detached from the rest of the protein in the absence of calcium. In the presence of calcium, the C-terminal lobe of the EF-domain acquires an ordered and more compact structure that enables its binding to the enzyme dehydrogenase (DH) domain. Our spectroscopic and mutagenesis studies further identified a set of conserved aspartate residues in the DH domain that are essential for NOX5 activation. Altogether, our work shows that calcium induces an unfolded-to-folded transition of the EF-domain that promotes direct interaction with a conserved regulatory region, resulting in NOX5 activation.
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Affiliation(s)
- Elisa Millana Fañanás
- Department of Biology and Biotechnology “Lazzaro Spallanzani”University of PaviaItaly
| | - Sofia Todesca
- Department of Biology and Biotechnology “Lazzaro Spallanzani”University of PaviaItaly
| | - Alessandro Sicorello
- UK Dementia Research Institute at King's College LondonUK
- The Wohl Institute at King's College LondonUK
| | | | - Petr Pompach
- Institute of BiotechnologyCzech Academy of SciencesVestecCzech Republic
- Institute of MicrobiologyCzech Academy of SciencesPragueCzech Republic
| | - Francesca Magnani
- Department of Biology and Biotechnology “Lazzaro Spallanzani”University of PaviaItaly
| | - Annalisa Pastore
- UK Dementia Research Institute at King's College LondonUK
- The Wohl Institute at King's College LondonUK
| | - Andrea Mattevi
- Department of Biology and Biotechnology “Lazzaro Spallanzani”University of PaviaItaly
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5
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Wei CC, Hay E, Smith D, Lloyd L, Acharya G, Ngo R. Binding of Nox5's EF-Hand domain to the peptides corresponding to the phosphorylatable region and regulatory inhibitory loop in its dehydrogenase domain. Biophys Chem 2020; 262:106379. [PMID: 32339785 DOI: 10.1016/j.bpc.2020.106379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/21/2020] [Accepted: 04/13/2020] [Indexed: 12/13/2022]
Abstract
Reactive oxygen species (ROS) produced by NADPH oxidase 5 (Nox5) are regulated by Ca2+ flux through the interactions of its self-contained EF-hand domain (EFD), dehydrogenase domain (DH), and transmembrane domain. Studies suggest that the regulatory EF-hand binding domain (REFBD) and phosphorylatable (PhosR) sequences within DH play an important role in Nox5's superoxide-generating activity. However, the interplay of the EFD-DH interaction is largely unclear. Here, we used two synthetic peptides corresponding to the putative REFBD and PhosR sequences, as well as DH construct proteins, and separately studied their binding to EFD by fluorescence spectroscopy and calorimetry. With mutagenesis, we revealed that the C-terminal half domain of EFD binds specifically to REFBD in a Ca2+-dependent manner, which is driven primarily by hydrophobic interactions to form a more compact structure. On the other hand, the interaction between EFD and PhosR is not Ca2+-dependent and is primarily dominated by electrostatic interactions. The binding constants (Ka) for both peptides to EFD were calculated to be in the range of 105 M-1. The formation of the binary complex EFD/REFBD and ternary complex EFD/REFBD/PhosR was demonstrated by fluorescence resonance energy transfer (FRET). However, EFD binding to PhosR appears to be not biologically important while the conformational change on its C-terminal half domain resembles a major factor in EFD-DH domain-domain interactions.
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Affiliation(s)
- Chin-Chuan Wei
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA; Department of Pharmaceutical Sciences, College of Pharmacy, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA.
| | - Evan Hay
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Dustin Smith
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Laura Lloyd
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Ganesh Acharya
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
| | - Rebecca Ngo
- Department of Chemistry, College of Arts and Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA
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6
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Wei CC, Fabry E, Hay E, Lloyd L, Kaufman N, Yang YP, Stuehr DJ. Metal binding and conformational studies of the calcium binding domain of NADPH oxidase 5 reveal its similarity and difference to calmodulin. J Biomol Struct Dyn 2019; 38:2352-2368. [DOI: 10.1080/07391102.2019.1633409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Chin-Chuan Wei
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA
| | - Emily Fabry
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA
| | - Evan Hay
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA
| | - Laura Lloyd
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA
| | - Nichole Kaufman
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois, USA
| | - Ya-Ping Yang
- Department of Pathobiology, the Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Dennis J. Stuehr
- Department of Pathobiology, the Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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7
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Chen F, Yin C, Dimitropoulou C, Fulton DJR. Cloning, Characteristics, and Functional Analysis of Rabbit NADPH Oxidase 5. Front Physiol 2016; 7:284. [PMID: 27486403 PMCID: PMC4950256 DOI: 10.3389/fphys.2016.00284] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 06/23/2016] [Indexed: 12/31/2022] Open
Abstract
Background: Nox5 was the last member of the Nox enzyme family to be identified. Functionally distinct from the other Nox isoforms, our understanding of its physiological significance has been hampered by the absence of Nox5 in mouse and rat genomes. Nox5 is present in the genomes of other species such as the rabbit that have broad utility as models of cardiovascular disease. However, the mRNA sequence, characteristics, and functional analysis of rabbit Nox5 has not been fully defined and were the goals of the current study. Methods: Rabbit Nox5 was amplified from rabbit tissue, cloned, and sequenced. COS-7 cells were employed for expression and functional analysis via Western blotting and measurements of superoxide. We designed and synthesized miRNAs selectively targeting rabbit Nox5. The nucleotide and amino acid sequences of rabbit Nox5 were aligned with those of putative rabbit isoforms (X1, X2, X3, and X4). A phylogenetic tree was generated based on the mRNA sequence for Nox5 from rabbit and other species. Results: Sequence alignment revealed that the identified rabbit Nox5 was highly conserved with the predicted sequence of rabbit Nox5. Cell based experiments reveal that rabbit Nox5 was robustly expressed and produced superoxide at rest and in a calcium and PMA-dependent manner that was susceptible to superoxide dismutase and the flavoprotein inhibitor, DPI. miRNA-1 was shown to be most effective in down-regulating the expression of rabbit Nox5. Phylogenetic analysis revealed a close relationship between rabbit and armadillo Nox5. Rabbit Nox5 was relatively closely related to human Nox5, but lies in a distinct cluster. Conclusion: Our study establishes the suitability of the rabbit as a model organism to further our understanding of the role of Nox5 in cardiovascular and other diseases and provides new information on the genetic relationship of Nox5 genes in different species.
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Affiliation(s)
- Feng Chen
- Department of Forensic Medicine, Nanjing Medical UniversityNanjing, Jiangsu, China; Vascular Biology Center, Medical College of Georgia at Augusta UniversityAugusta, GA, USA
| | - Caiyong Yin
- Department of Forensic Medicine, Nanjing Medical University Nanjing, Jiangsu, China
| | | | - David J R Fulton
- Vascular Biology Center, Medical College of Georgia at Augusta University Augusta, GA, USA
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8
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Jensen D, Reynolds N, Yang YP, Shakya S, Wang ZQ, Stuehr DJ, Wei CC. The exchanged EF-hands in calmodulin and troponin C chimeras impair the Ca²⁺-induced hydrophobicity and alter the interaction with Orai1: a spectroscopic, thermodynamic and kinetic study. BMC BIOCHEMISTRY 2015; 16:6. [PMID: 25888318 PMCID: PMC4349623 DOI: 10.1186/s12858-015-0036-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 01/27/2015] [Indexed: 12/18/2022]
Abstract
Background Calmodulin (CaM) plays an important role in Ca2+-dependent signal transduction. Ca2+ binding to CaM triggers a conformational change, forming a hydrophobic patch that is important for target protein recognition. CaM regulates a Ca2+-dependent inactivation process in store-operated Ca2+ entry, by interacting Orai1. To understand the relationship between Ca2+-induced hydrophobicity and CaM/Orai interaction, chimera proteins constructed by exchanging EF-hands of CaM with those of Troponin C (TnC) are used as an informative probe to better understand the functionality of each EF-hand. Results ANS was used to assess the context of the induced hydrophobic surface on CaM and chimeras upon Ca2+ binding. The exchanged EF-hands from TnC to CaM resulted in reduced hydrophobicity compared with wild-type CaM. ANS lifetime measurements indicated that there are two types of ANS molecules with rather distinct fluorescence lifetimes, each specifically corresponding to one lobe of CaM or chimeras. Thermodynamic studies indicated the interaction between CaM and a 24-residue peptide corresponding to the CaM-binding domain of Orail1 (Orai-CMBD) is a 1:2 CaM/Orai-CMBD binding, in which each peptide binding yields a similar enthalpy change (ΔH = −5.02 ± 0.13 kcal/mol) and binding affinity (Ka = 8.92 ± 1.03 × 105 M−1). With the exchanged EF1 and EF2, the resulting chimeras noted as CaM(1TnC) and CaM(2TnC), displayed a two sequential binding mode with a one-order weaker binding affinity and lower ΔH than that of CaM, while CaM(3TnC) and CaM(4TnC) had similar binding thermodynamics as CaM. The dissociation rate constant for CaM/Orai-CMBD was determined to be 1.41 ± 0.08 s−1 by rapid kinetics. Stern-Volmer plots of Orai-CMBD Trp76 indicated that the residue is located in a very hydrophobic environment but becomes more solvent accessible when EF1 and EF2 were exchanged. Conclusions Using ANS dye to assess induced hydrophobicity showed that exchanging EFs for all Ca2+-bound chimeras impaired ANS fluorescence and/or binding affinity, consistent with general concepts about the inadequacy of hydrophobic exposure for chimeras. However, such ANS responses exhibited no correlation with the ability to interact with Orai-CMBD. Here, the model of 1:2 binding stoichiometry of CaM/Orai-CMBD established in solution supports the already published crystal structure.
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Affiliation(s)
- Drake Jensen
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA.
| | - Nicole Reynolds
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA.
| | - Ya-Ping Yang
- Department of Pathobiology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, 44195, USA.
| | - Shubha Shakya
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA.
| | - Zhi-Qiang Wang
- Department of Chemistry, Kent State University at Tuscarawas, New Philadelphia, OH, 44663, USA.
| | - Dennis J Stuehr
- Department of Pathobiology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, 44195, USA.
| | - Chin-Chuan Wei
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, IL, 62026, USA.
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9
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Martínez-Oliván J, Rozado-Aguirre Z, Arias-Moreno X, Angarica VE, Velázquez-Campoy A, Sancho J. Low-density lipoprotein receptor is a calcium/magnesium sensor - role of LR4 and LR5 ion interaction kinetics in low-density lipoprotein release in the endosome. FEBS J 2014; 281:2638-58. [PMID: 24720672 DOI: 10.1111/febs.12811] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/25/2014] [Accepted: 04/08/2014] [Indexed: 11/28/2022]
Abstract
The low-density lipoprotein receptor (LDLR) captures circulating lipoproteins and delivers them in the endosome for degradation. Its function is essential for cholesterol homeostasis, and mutations in the LDLR are the major cause of familiar hypercholesterolemia. The release of LDL is usually attributed to endosome acidification. As the pH drops, the affinity of the LDLR/LDL complex is reduced, whereas the strength of a self-complex formed between two domains of the receptor (i.e. the LDL binding domain and the β-propeller domain) increases. However, an alternative model states that, as a consequence of a drop in both pH and Ca(2+) concentration, the LDLR binding domain is destabilized in the endosome, which weakens the LDLR/LDL complex, thus liberating the LDL particles. In the present study, we test a key underlying assumption of the second model, namely that the lipoprotein binding repeats of the receptor (specifically repeats 4 and 5, LR4 and LR5) rapidly sense endosomal changes in Ca(2+) concentration. Our kinetic and thermodynamic analysis of Ca(2+) and Mg(2+) binding to LR4 and LR5, as well as to the tandem of the two (LR4-5), shows that both repeats spontaneously release Ca(2+) in a time scale much shorter than endosomal delivery of LDL, thus acting as Ca(2+) sensors that become unfolded under endosomal conditions. Our analysis additionally explains the lower Ca(2+) affinity of repeat LR4, compared to LR5, as arising from a very slow Ca(2+) binding reaction in the former, most likely related to the lower conformational stability of apolipoprotein LR4, compared to apolipoprotein LR5, as determined from thermal unfolding experiments and molecular dynamics simulations.
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Affiliation(s)
- Juan Martínez-Oliván
- Biocomputation and Complex Systems Physics Institute (BIFI) - Joint Unit BIFI-IQFR (CSIC), Universidad de Zaragoza, Spain; Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Spain
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10
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Characterization of the 1st and 2nd EF-hands of NADPH oxidase 5 by fluorescence, isothermal titration calorimetry, and circular dichroism. Chem Cent J 2012; 6:29. [PMID: 22490336 PMCID: PMC3386892 DOI: 10.1186/1752-153x-6-29] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 04/10/2012] [Indexed: 11/16/2022] Open
Abstract
Background Superoxide generated by non-phagocytic NADPH oxidases (NOXs) is of growing importance for physiology and pathobiology. The calcium binding domain (CaBD) of NOX5 contains four EF-hands, each binding one calcium ion. To better understand the metal binding properties of the 1st and 2nd EF-hands, we characterized the N-terminal half of CaBD (NCaBD) and its calcium-binding knockout mutants. Results The isothermal titration calorimetry measurement for NCaBD reveals that the calcium binding of two EF-hands are loosely associated with each other and can be treated as independent binding events. However, the Ca2+ binding studies on NCaBD(E31Q) and NCaBD(E63Q) showed their binding constants to be 6.5 × 105 and 5.0 × 102 M-1 with ΔHs of -14 and -4 kJ/mol, respectively, suggesting that intrinsic calcium binding for the 1st non-canonical EF-hand is largely enhanced by the binding of Ca2+ to the 2nd canonical EF-hand. The fluorescence quenching and CD spectra support a conformational change upon Ca2+ binding, which changes Trp residues toward a more non-polar and exposed environment and also increases its α-helix secondary structure content. All measurements exclude Mg2+-binding in NCaBD. Conclusions We demonstrated that the 1st non-canonical EF-hand of NOX5 has very weak Ca2+ binding affinity compared with the 2nd canonical EF-hand. Both EF-hands interact with each other in a cooperative manner to enhance their Ca2+ binding affinity. Our characterization reveals that the two EF-hands in the N-terminal NOX5 are Ca2+ specific. Graphical abstract
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11
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Bedard K, Jaquet V, Krause KH. NOX5: from basic biology to signaling and disease. Free Radic Biol Med 2012; 52:725-34. [PMID: 22182486 DOI: 10.1016/j.freeradbiomed.2011.11.023] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 11/10/2011] [Accepted: 11/12/2011] [Indexed: 02/07/2023]
Abstract
In mammals, the NADPH oxidase family of enzymes comprises seven members: NOXs 1-5, DUOX1, and DUOX2. All of these enzymes function to move an electron across cellular membranes, transferring it to oxygen to generate the superoxide anion. This generation of reactive oxygen species has important physiological and pathophysiological roles. NOX5 is perhaps the least well understood of these NOX isoforms, in part because the gene is not present in mice or rats. In recent years, however, there has been a rapid increase in our understanding of the NOX5 gene, the structural and biochemical aspects of the NOX5 enzyme, the role NOX5 plays in health and disease, and the development of novel NOX inhibitors. This review takes a look back at some historical aspects of the discovery of NOX5 and summarizes our current understanding of the enzyme.
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Affiliation(s)
- Karen Bedard
- Department of Pathology, Dalhousie University, Halifax, Canada
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12
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Pandey D, Gratton JP, Rafikov R, Black SM, Fulton DJR. Calcium/calmodulin-dependent kinase II mediates the phosphorylation and activation of NADPH oxidase 5. Mol Pharmacol 2011; 80:407-15. [PMID: 21642394 DOI: 10.1124/mol.110.070193] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Excessive synthesis of reactive oxygen species contributes to the pathology of many human diseases and originates from changes in the expression and posttranslational regulation of the transmembrane NADPH oxidases (Noxes). Nox5 is a novel Nox isoform whose activity is regulated by intracellular calcium levels. We have reported that the activity and calcium-sensitivity of Nox5 can also be modulated by direct phosphorylation. However, the kinases that phosphorylate Nox5 have not been identified, and thus, the goal of this study was to determine whether calcium-activated kinases such as calcium/calmodulin-dependent kinase II (CAMKII) are involved. We found that Nox5 activity in bovine aortic endothelial cells was suppressed by two doses of the CAMKII inhibitor 2-(N-[2-hydroxyethyl])-N-(4-methoxybenzenesulfonyl)amino-N-(4-chlorocinnamyl)-N-methylamine (KN-93). In cotransfected COS-7 cells, wild-type and constitutively active CAMKII, but not a dominant-negative, robustly increased basal Nox5 activity. The ability of CAMKII to increase Nox5 activity was also observed with fixed calcium concentrations in an isolated enzyme activity assay. CAMKII did not elevate intracellular calcium or activate other Nox enzymes. In vitro phosphorylation assays revealed that CAMKII can directly phosphorylate Nox5 on Thr494 and Ser498 as detected by phosphorylation state-specific antibodies. Mass spectrometry (MS) analysis revealed the phosphorylation of additional, novel sites at Ser475, Ser502, and Ser675. Of these phosphorylation sites, mutation of only Ser475 to alanine prevented CAMKII-induced increases in Nox5 activity. The ability of CAMKIIα to phosphorylate Ser475 in intact cells was supported by the binding of Nox5 to phosphoprotein-affinity columns and via MS/MS analysis. Together, these results suggest that CAMKII can positively regulate Nox5 activity via the phosphorylation of Ser475.
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Affiliation(s)
- Deepesh Pandey
- Vascular Biology Center, Medical College of Georgia, Augusta, GA, USA
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13
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Abstract
The Noxes (NADPH oxidases) are a family of ROS (reactive oxygen species)-generating enzymes. Of the seven family members, four have been identified as important sources of ROS in the vasculature: Nox1, Nox2, Nox4 and Nox5. Although Nox isoforms can be influenced by the same stimulus and co-localize in cellular compartments, their tissue distribution, subcellular regulation, requirement for cofactors and NADPH oxidase subunits and ability to generate specific ROS differ, which may help to understand the multiplicity of biological functions of these oxidases. Nox4 and Nox5 are the newest isoforms identified in the vasculature. Nox4 is the major isoform expressed in renal cells and appear to produce primarily H2O2. The Nox5 isoform produces ROS in response to increased levels of intracellular Ca2+ and does not require the other NADPH oxidase subunits for its activation. The present review focuses on these unique Noxes, Nox4 and Nox5, and provides novel concepts related to the regulation and interaction in the vasculature, and discusses new potential roles for these isoforms in vascular biology.
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