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Dias DA, de Barros Penteado B, Dos Santos LD, Dos Santos PM, Arruda CCP, Schetinger MRC, Leal DBR, Dos Santos Jaques JA. Characterization of ectonucleoside triphosphate diphosphohydrolase (E-NTPDase; EC 3.6.1.5) activity in mouse peritoneal cavity cells. Cell Biochem Funct 2017; 35:358-363. [PMID: 28871607 DOI: 10.1002/cbf.3281] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 07/05/2017] [Accepted: 07/05/2017] [Indexed: 12/20/2022]
Abstract
This study aimed to characterize the activity of ectonucleoside triphosphate diphosphohydrolase (E-NTPDase; EC 3.6.1.5) in peritoneal cavity cells from BALB/c mice. E-NTPDase was activated in the presence of both calcium (1.5mM) and magnesium (1.5mM) ions. However, the activity was higher in the presence of Ca2+ . A pH of 8.5 and temperature of 37°C were the optimum conditions for catalysis. The apparent Km values were 0.51mM and 0.66mM for the hydrolysis of adenosine triphosphate (ATP) and adenosine diphosphate (ADP), respectively. The Vmax values were 136.4 and 120.8 nmol Pi/min/mg of protein for ATPase and ADPase activity, respectively. Nucleotide hydrolysis was inhibited in the presence of sodium azide (20mM, ATP: P < .05; ADP: P < .001), sodium fluoride (20mM; ATP and ADP: P < .001), and suramin (0.3mM; ATP: P < .01; ADP: P < .05), which is a known profile for NTPDase inhibition. Although all of the diphosphate and triphosphate nucleotides that were tested were hydrolyzed, enzyme activity was increased when adenine nucleotides were used as substrates. Finally, we stress that knowledge of the E-NTPDase catalytic biochemical properties in mouse peritoneal cavity cells is indispensable for properly determining its activity, as well as to fully understand the immune response profile in both healthy and sick cells.
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Affiliation(s)
- Dhébora Albuquerque Dias
- Laboratório de Bioquímica Geral e de Microrganismos, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.,Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia Alimentos e Nutrição, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Bruna de Barros Penteado
- Laboratório de Bioquímica Geral e de Microrganismos, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.,Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia Alimentos e Nutrição, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Lucas Derbocio Dos Santos
- Laboratório de Bioquímica Geral e de Microrganismos, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.,Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia Alimentos e Nutrição, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
| | | | - Carla Cardozo Pinto Arruda
- Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia Alimentos e Nutrição, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.,Laboratório de Parasitologia Humana, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Maria Rosa Chitolina Schetinger
- Laboratório de Enzimologia Toxicológica, Departamento de Bioquímica, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Daniela Bitencourt Rosa Leal
- Laboratório de Imunobiologia Experimental e Aplicada, Departamento de Microbiologia e Parasitologia, Centro de Ciências da Saúde, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Jeandre Augusto Dos Santos Jaques
- Laboratório de Bioquímica Geral e de Microrganismos, Instituto de Biociências, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.,Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia Alimentos e Nutrição, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
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Rueda N, dos Santos JCS, Ortiz C, Torres R, Barbosa O, Rodrigues RC, Berenguer-Murcia Á, Fernandez-Lafuente R. Chemical Modification in the Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities. CHEM REC 2016; 16:1436-55. [DOI: 10.1002/tcr.201600007] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Nazzoly Rueda
- Departamento de Biocatálisis; ICP-CSIC C/Marie Curie 2, Campus UAM-CSIC; Cantoblanco 28049 Madrid Spain
- Escuela de Química, Grupo de investigación en Bioquímica y Microbiología (GIBIM) Edificio Camilo Torres 210, Universidad Industrial de Santander; CEP 680001 Bucaramanga Colombia
| | - Jose C. S. dos Santos
- Departamento de Biocatálisis; ICP-CSIC C/Marie Curie 2, Campus UAM-CSIC; Cantoblanco 28049 Madrid Spain
- Instituto de Engenharias e Desenvolvimento Sustentável Universidade da Integração Internacional da Lusofonia Afro-Brasileira; CEP 62785-000 Acarape CE Brazil
| | - Claudia Ortiz
- Escuela de Microbiología, Universidad Industrial de Santander; Bucaramanga Colombia
| | - Rodrigo Torres
- Escuela de Química, Grupo de investigación en Bioquímica y Microbiología (GIBIM) Edificio Camilo Torres 210, Universidad Industrial de Santander; CEP 680001 Bucaramanga Colombia
| | - Oveimar Barbosa
- Departamento de Química; Facultad de Ciencias Universidad del Tolima; Ibagué Colombia
| | - Rafael C. Rodrigues
- Biocatalysis and Enzyme Technology Laboratory; Institute of Food Science and Technology Federal University of Rio Grande do Sul; Av. Bento Gonçalves 9500 P.O. Box 15090 Porto Alegre RS Brazil
| | - Ángel Berenguer-Murcia
- Instituto Universitario de Materiales Departamento de Química Inorgánica Universidad de Alicante Campus de San Vicente del Raspeig; Ap. 99 - 03080 Alicante Spain
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Flores-Herrera O, Olvera-Sánchez S, Esparza-Perusquía M, Pardo JP, Rendón JL, Mendoza-Hernández G, Martínez F. Membrane potential regulates mitochondrial ATP-diphosphohydrolase activity but is not involved in progesterone biosynthesis in human syncytiotrophoblast cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:143-152. [PMID: 25444704 DOI: 10.1016/j.bbabio.2014.10.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 09/17/2014] [Accepted: 10/07/2014] [Indexed: 11/26/2022]
Abstract
ATP-diphosphohydrolase is associated with human syncytiotrophoblast mitochondria. The activity of this enzyme is implicated in the stimulation of oxygen uptake and progesterone synthesis. We reported previously that: (1) the detergent-solubilized ATP-diphosphohydrolase has low substrate specificity, and (2) purine and pyrimidine nucleosides, tri- or diphosphates, are fully dephosphorylated in the presence of calcium or magnesium (Flores-Herrera 1999, 2002). In this study we show that ATP-diphosphohydrolase hydrolyzes first the nucleoside triphosphate to nucleoside diphosphate, and then to nucleotide monophosphate, in the case of all tested nucleotides. The activation energies (Ea) for ATP, GTP, UTP, and CTP were 6.06, 4.10, 6.25, and 5.26 kcal/mol, respectively; for ADP, GDP, UDP, and CDP, they were 4.67, 5.42, 5.43, and 6.22 kcal/mol, respectively. The corresponding Arrhenius plots indicated a single rate-limiting step for each hydrolyzed nucleoside, either tri- or diphosphate. In intact mitochondria, the ADP produced by ATP-diphosphohydrolase activity depolarized the membrane potential (ΔΨm) and stimulated oxygen uptake. Mitochondrial respiration showed the state-3/state-4 transition when ATP was added, suggesting that ATP-diphosphohydrolase and the F1F0-ATP synthase work in conjunction to avoid a futile cycle. Substrate selectivity of the ATP-diphosphohydrolase was modified by ΔΨm (i.e. ATP was preferred over GTP when the inner mitochondrial membrane was energized). In contrast, dissipation of ΔΨm by CCCP produced a loss of substrate specificity and so the ATP-diphosphohydrolase was able to hydrolyze ATP and GTP at the same rate. In intact mitochondria, ATP hydrolysis increased progesterone synthesis as compared with GTP. Although dissipation of ΔΨm by CCCP decreased progesterone synthesis, NADPH production restores steroidogenesis. Overall, our results suggest a novel physiological role for ΔΨm in steroidogenesis.
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Affiliation(s)
- Oscar Flores-Herrera
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico.
| | - Sofia Olvera-Sánchez
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
| | - Mercedes Esparza-Perusquía
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
| | - Juan Pablo Pardo
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
| | - Juan Luis Rendón
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
| | - Guillermo Mendoza-Hernández
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
| | - Federico Martínez
- Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Bioquímica y Biología Molecular, México City, Mexico
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Barbosa O, Ortiz C, Berenguer-Murcia Á, Torres R, Rodrigues RC, Fernandez-Lafuente R. Glutaraldehyde in bio-catalysts design: a useful crosslinker and a versatile tool in enzyme immobilization. RSC Adv 2014. [DOI: 10.1039/c3ra45991h] [Citation(s) in RCA: 571] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Giudici AM, Molina ML, Ayala JL, Montoya E, Renart ML, Fernández AM, Encinar JA, Ferrer-Montiel AV, Poveda JA, González-Ros JM. Detergent-labile, supramolecular assemblies of KcsA: Relative abundance and interactions involved. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:193-200. [DOI: 10.1016/j.bbamem.2012.09.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 08/22/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
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Zimmermann H, Zebisch M, Sträter N. Cellular function and molecular structure of ecto-nucleotidases. Purinergic Signal 2012; 8:437-502. [PMID: 22555564 PMCID: PMC3360096 DOI: 10.1007/s11302-012-9309-4] [Citation(s) in RCA: 768] [Impact Index Per Article: 64.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 02/01/2012] [Indexed: 12/12/2022] Open
Abstract
Ecto-nucleotidases play a pivotal role in purinergic signal transmission. They hydrolyze extracellular nucleotides and thus can control their availability at purinergic P2 receptors. They generate extracellular nucleosides for cellular reuptake and salvage via nucleoside transporters of the plasma membrane. The extracellular adenosine formed acts as an agonist of purinergic P1 receptors. They also can produce and hydrolyze extracellular inorganic pyrophosphate that is of major relevance in the control of bone mineralization. This review discusses and compares four major groups of ecto-nucleotidases: the ecto-nucleoside triphosphate diphosphohydrolases, ecto-5'-nucleotidase, ecto-nucleotide pyrophosphatase/phosphodiesterases, and alkaline phosphatases. Only recently and based on crystal structures, detailed information regarding the spatial structures and catalytic mechanisms has become available for members of these four ecto-nucleotidase families. This permits detailed predictions of their catalytic mechanisms and a comparison between the individual enzyme groups. The review focuses on the principal biochemical, cell biological, catalytic, and structural properties of the enzymes and provides brief reference to tissue distribution, and physiological and pathophysiological functions.
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Affiliation(s)
- Herbert Zimmermann
- Institute of Cell Biology and Neuroscience, Molecular and Cellular Neurobiology, Biologicum, Goethe-University Frankfurt, Max-von-Laue-Str. 13, 60438, Frankfurt am Main, Germany.
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Bringmann A, Wiedemann P. Müller glial cells in retinal disease. ACTA ACUST UNITED AC 2011; 227:1-19. [PMID: 21921569 DOI: 10.1159/000328979] [Citation(s) in RCA: 278] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 04/27/2011] [Indexed: 11/19/2022]
Abstract
Virtually all pathogenic stimuli activate Müller cells. Reactive Müller cells exert protective and toxic effects on photoreceptors and neurons. They contribute to oxidative stress and glutamate toxicity due to malfunctions of glutamate uptake and glutathione synthesis. Downregulation of potassium conductance disrupts transcellular potassium and water transport, resulting in neuronal hyperexcitability and edema. Protective effects of reactive Müller cells include upregulation of adenosine 5'-triphosphate (ATP)-degrading ectoenzymes, which enhances the extracellular availability of the neuroprotectant adenosine, abrogation of the osmotic release of ATP, which might protect retinal ganglion cells from apoptosis, and the release of antioxidants and neurotrophic factors. The dedifferentiation of reactive Müller cells to progenitor-like cells might have an impact on future therapeutic approaches. A better understanding of the gliotic mechanisms will be helpful in developing efficient therapeutic strategies aiming at increased protective and regenerative properties and decreased toxicity of reactive Müller cells.
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Affiliation(s)
- Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany
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Wurm A, Pannicke T, Iandiev I, Francke M, Hollborn M, Wiedemann P, Reichenbach A, Osborne NN, Bringmann A. Purinergic signaling involved in Müller cell function in the mammalian retina. Prog Retin Eye Res 2011; 30:324-42. [DOI: 10.1016/j.preteyeres.2011.06.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 06/06/2011] [Accepted: 06/06/2011] [Indexed: 10/18/2022]
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Kukulski F, Lévesque SA, Sévigny J. Impact of ectoenzymes on p2 and p1 receptor signaling. ADVANCES IN PHARMACOLOGY 2011; 61:263-99. [PMID: 21586362 DOI: 10.1016/b978-0-12-385526-8.00009-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
P2 receptors that are activated by extracellular nucleotides (e.g., ATP, ADP, UTP, UDP, Ap(n)A) and P1 receptors activated by adenosine control a diversity of biological processes. The activation of these receptors is tightly regulated by ectoenzymes that metabolize their ligands. This review presents these enzymes as well as their roles in the regulation of P2 and P1 receptor activation. We focus specifically on the role of ectoenzymes in processes of our interest, that is, inflammation, vascular tone, and neurotransmission. An update on the development of ectonucleotidase inhibitors is also presented.
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Affiliation(s)
- Filip Kukulski
- Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, Québec, Canada
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Papanikolaou A, Papafotika A, Christoforidis S. CD39 Reveals Novel Insights into the Role of Transmembrane Domains in Protein Processing, Apical Targeting and Activity. Traffic 2011; 12:1148-65. [DOI: 10.1111/j.1600-0854.2011.01224.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Lavoie EG, Gulbransen BD, Martín-Satué M, Aliagas E, Sharkey KA, Sévigny J. Ectonucleotidases in the digestive system: focus on NTPDase3 localization. Am J Physiol Gastrointest Liver Physiol 2011; 300:G608-20. [PMID: 21233276 DOI: 10.1152/ajpgi.00207.2010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Extracellular nucleotides and adenosine are biologically active molecules that bind members of the P2 and P1 receptor families, respectively. In the digestive system, these receptors modulate various functions, including salivary, gastric, and intestinal epithelial secretion and enteric neurotransmission. The availability of P1 and P2 ligands is modulated by ectonucleotidases, enzymes that hydrolyze extracellular nucleotides into nucleosides. Nucleoside triphosphate diphosphohydrolases (NTPDases) and ecto-5'-nucleotidase are the dominant ectonucleotidases at physiological pH. While there is some information about the localization of ecto-5'-nucleotidase and NTPDase1 and -2, the distribution of NTPDase3 in the digestive system is unknown. We examined the localization of these ectonucleotidases, with a focus on NTPDase3, in the gastrointestinal tract and salivary glands. NTPDase1, -2, and -3 are responsible for ecto-ATPase activity in these tissues. Semiquantitative RT-PCR, immunohistochemistry, and in situ enzyme activity revealed the presence of NTPDase3 in some epithelial cells in serous acini of salivary glands and mucous acini and duct cells of sublingual salivary glands, in cells from the stratified esophageal and forestomach epithelia, and in some enteroendocrine cells of the gastric antrum. Interestingly, NTPDase2 and ecto-5'-nucleotidase are coexpressed with NTPDase3 in salivary gland cells and stratified epithelia. In the colon, neurons express NTPDase3 and glial cells express NTPDase2. Ca(2+) imaging experiments demonstrate that NTPDases regulate P2 receptor ligand availability in the enteric nervous system. In summary, the specific localization of NTPDase3 in the digestive system suggests functional roles of the enzyme, in association with NTPDase2 and ecto-5'-nucleotidase, in epithelial functions such as secretion and in enteric neurotransmission.
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Affiliation(s)
- Elise G Lavoie
- Centre de Recherche en Rhumatologie et Immunologie, Centre Hospitalier Universitaire de Québec, QC, Canada
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Knowles AF. The GDA1_CD39 superfamily: NTPDases with diverse functions. Purinergic Signal 2011; 7:21-45. [PMID: 21484095 DOI: 10.1007/s11302-010-9214-7] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Accepted: 12/21/2010] [Indexed: 01/05/2023] Open
Abstract
The first comprehensive review of the ubiquitous "ecto-ATPases" by Plesner was published in 1995. A year later, a lymphoid cell activation antigen, CD39, that had been cloned previously, was shown to be an ecto-ATPase. A family of proteins, related to CD39 and a yeast GDPase, all containing the canonical apyrase conserved regions in their polypeptides, soon started to expand. They are now recognized as members of the GDA1_CD39 protein family. Because proteins in this family hydrolyze nucleoside triphosphates and diphosphates, a unifying nomenclature, nucleoside triphosphate diphopshohydrolases (NTPDases), was established in 2000. Membrane-bound NTPDases are either located on the cell surface or membranes of intracellular organelles. Soluble NTPDases exist in the cytosol and may be secreted. In the last 15 years, molecular cloning and functional expression have facilitated biochemical characterization of NTPDases of many organisms, culminating in the recent structural determination of the ecto-domain of a mammalian cell surface NTPDase and a bacterial NTPDase. The first goal of this review is to summarize the biochemical, mutagenesis, and structural studies of the NTPDases. Because of their ability in hydrolyzing extracellular nucleotides, the mammalian cell surface NTPDases (the ecto-NTPDases) which regulate purinergic signaling have received the most attention. Less appreciated are the functions of intracellular NTPDases and NTPDases of other organisms, e.g., bacteria, parasites, Drosophila, plants, etc. The second goal of this review is to summarize recent findings which demonstrate the involvement of the NTPDases in multiple and diverse physiological processes: pathogen-host interaction, plant growth, eukaryote cell protein and lipid glycosylation, eye development, and oncogenesis.
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Affiliation(s)
- Aileen F Knowles
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Drive, San Diego, CA, 92182-1030, USA,
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Flittiger B, Klapperstück M, Schmalzing G, Markwardt F. Effects of protons on macroscopic and single-channel currents mediated by the human P2X7 receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:947-57. [PMID: 20138022 DOI: 10.1016/j.bbamem.2010.01.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 01/18/2010] [Accepted: 01/28/2010] [Indexed: 01/28/2023]
Abstract
Human P2X7 receptors (hP2X7Rs) belong to the P2X family, which opens an intrinsic cation channel when challenged by extracellular ATP. hP2X7Rs are expressed in cells of the inflammatory and immune system. During inflammation, ATP and protons are secreted into the interstitial fluid. Therefore, we investigated the effect of protons on the activation of hP2X7Rs. hP2X7Rs were expressed in Xenopus laevis oocytes and activated by the agonists ATP or benzoyl-benzoyl-ATP (BzATP) at different pH values. The protons reduced the hP2X7R-dependent cation current amplitude and slowed the current deactivation depending on the type and concentration of the agonist used. These effects can be explained by (i) the protonation of ATP, which reduces the effective concentration of the agonist ATP(4-) at the high- and low-affinity ATP activation site of the hP2XR, and (ii) direct allosteric inhibition of the hP2X7R channel opening that follows ATP(4-) binding to the low-affinity activation site. Due to the hampered activation via the low-affinity activation site, a low pH (as observed in inflamed tissues) leads to a relative increase in the contribution of the high-affinity activation site for hP2X7R channel opening.
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Affiliation(s)
- B Flittiger
- Julius-Bernstein-Institute for Physiology, Martin-Luther-University Halle, Magdeburger Strasse 6, D-06097 Halle/Saale, Germany
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Gaddie KJ, Kirley TL. Conserved polar residues stabilize transmembrane domains and promote oligomerization in human nucleoside triphosphate diphosphohydrolase 3. Biochemistry 2009; 48:9437-47. [PMID: 19743837 DOI: 10.1021/bi900909g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polar residues play essential roles in the functions of transmembrane helices by mediating and stabilizing their helical interactions. To investigate the structural and functional roles of the conserved polar residues in the N- and C-terminal transmembrane helices of human nucleoside triphosphate diphosphohydrolase 3 (NTPDase3) (N-terminus, S33, S39, T41, and Q44; C-terminus, T490, T495, and C501), each was singly mutated to alanine. The mutant proteins were analyzed for enzymatic activities, glycosylation status, expression level, and Triton X-100 detergent sensitivity. The Q44A mutation decreased Mg-ATPase activity by approximately 70% and abolished Triton X-100 detergent inhibition of Ca-dependent nucleotidase activities while greatly attenuating Triton X-100 inhibition of Mg-dependent nucleotidase activities. The polar residues were also mutated to cysteine, singly and in pairs, to allow a disulfide cross-linking strategy to map potential inter- and intramolecular hydrogen bond interactions. The results support the centrality of Q44 for the strong intermolecular interactions driving the association of the N-terminal helices of two NTPDase3 monomers in a dimer, and the possibility that T41 may play a role in the specificity of this interaction. In addition, S33 and C501 form an intramolecular association, while S39 and T495 may contribute to helical interactions involved in forming higher-order oligomers. Lastly, Tween 20 substantially and selectively increases NTPDase3 activity, mediated by the transmembrane helices containing the conserved polar residues. Taken together, the data suggest a model for putative hydrogen bond interactions of the conserved polar residues in the transmembrane domain of native, oligomeric NTPDase3. These interactions are important for proper protein expression, full enzymatic activity, and susceptibility to membrane perturbations.
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Affiliation(s)
- Keith J Gaddie
- Department of Pharmacology and Cell Biophysics, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0575, USA
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Role of retinal glial cells in neurotransmitter uptake and metabolism. Neurochem Int 2009; 54:143-60. [DOI: 10.1016/j.neuint.2008.10.014] [Citation(s) in RCA: 171] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 10/15/2008] [Accepted: 10/20/2008] [Indexed: 11/30/2022]
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Wurm A, Iandiev I, Hollborn M, Wiedemann P, Reichenbach A, Zimmermann H, Bringmann A, Pannicke T. Purinergic receptor activation inhibits osmotic glial cell swelling in the diabetic rat retina. Exp Eye Res 2008; 87:385-93. [DOI: 10.1016/j.exer.2008.07.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 06/23/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
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Structure-activity relationships of anthraquinone derivatives derived from bromaminic acid as inhibitors of ectonucleoside triphosphate diphosphohydrolases (E-NTPDases). Purinergic Signal 2008; 5:91-106. [PMID: 18528783 PMCID: PMC2721768 DOI: 10.1007/s11302-008-9103-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2008] [Accepted: 04/10/2008] [Indexed: 12/03/2022] Open
Abstract
Reactive blue 2 (RB-2) had been characterized as a relatively potent ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) inhibitor with some selectivity for NTPDase3. In search for the pharmacophore and to analyze structure-activity relationships we synthesized a series of truncated derivatives and analogs of RB-2, including 1-amino-2-sulfo-4-ar(alk)ylaminoanthraquinones, 1-amino-2-methyl-4-arylaminoanthraquinones, 1-amino-4-bromoanthraquinone 2-sulfonic acid esters and sulfonamides, and bis-(1-amino-4-bromoanthraquinone) sulfonamides, and investigated them in preparations of rat NTPDase1, 2, and 3 using a capillary electrophoresis assay. Several 1-amino-2-sulfo-4-ar(alk)ylaminoanthraquinone derivatives inhibited E-NTPDases in a concentration-dependent manner. The 2-sulfonate group was found to be required for inhibitory activity, since 2-methyl-substituted derivatives were inactive. 1-Amino-2-sulfo-4-p-chloroanilinoanthraquinone (18) was identified as a nonselective competitive blocker of NTPDases1, 2, and 3 (Ki 16–18 μM), while 1-amino-2-sulfo-4-(2-naphthylamino)anthraquinone (21) was a potent inhibitor with preference for NTPDase1 (Ki 0.328 μM) and NTPDase3 (Ki 2.22 μM). Its isomer, 1-amino-2-sulfo-4-(1-naphthylamino)anthraquinone (20), was a potent and selective inhibitor of rat NTPDase3 (Ki 1.5 μM).
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19
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Detro-Dassen S, Schänzler M, Lauks H, Martin I, zu Berstenhorst SM, Nothmann D, Torres-Salazar D, Hidalgo P, Schmalzing G, Fahlke C. Conserved dimeric subunit stoichiometry of SLC26 multifunctional anion exchangers. J Biol Chem 2007; 283:4177-88. [PMID: 18073211 DOI: 10.1074/jbc.m704924200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The SLC26 gene family encodes multifunctional transport proteins in numerous tissues and organs. Some paralogs function as anion exchangers, others as anion channels, and one, prestin (SLC26A5), represents a membrane-bound motor protein in outer hair cells of the inner ear. At present, little is known about the molecular basis of this functional diversity. We studied the subunit stoichiometry of one bacterial, one teleost, and two mammalian SLC26 isoforms expressed in Xenopus laevis oocytes or in mammalian cells using blue native PAGE and chemical cross-linking. All tested SLC26s are assembled as dimers composed of two identical subunits. Co-expression of two mutant prestins with distinct voltage-dependent capacitances results in motor proteins with novel electrical properties, indicating that the two subunits do not function independently. Our results indicate that an evolutionarily conserved dimeric quaternary structure represents the native and functional state of SLC26 transporters.
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Affiliation(s)
- Silvia Detro-Dassen
- Abteilung Molekulare Pharmakologie, Rheinisch-Westfälische Technische Hochschule Aachen University, Wendlingweg 2, Aachen 52074, Germany
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20
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Zebisch M, Sträter N. Characterization of Rat NTPDase1, -2, and -3 ectodomains refolded from bacterial inclusion bodies. Biochemistry 2007; 46:11945-56. [PMID: 17910474 DOI: 10.1021/bi701103y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ecto-nucleoside triphosphate diphosphohydrolases or NTPDases are a family of membrane-bound enzymes that catalyze the sequential removal of gamma- and beta-phosphate from ATP, ADP, and other nucleotides. NTPDase1, -2, -3, and -8 are the enzymes responsible for signal conversion and termination in purinergic signaling. They are anchored to the cytoplasmic membrane by two transmembrane helices with a large catalytic domain pointing toward the extracellular space. Here we report the first successful expression and purification of the soluble extracellular domains of rat NTPDase1, -2, and -3 from bacterial inclusion bodies. The refolded proteins show characteristics similar to the wild type enzymes, for example in that they are dependent on divalent metal ions for catalysis and hydrolyze a wide variety of nucleoside tri- and diphosphates, whereas the monophosphate AMP is not further degraded. Nucleoside triphosphates are hydrolyzed at a higher rate than the corresponding diphosphates. Other characteristics of the recombinant enzymes however reflect the absence of transmembrane regions and side chain glycosylation. For example all three enzymes are monomeric and only subtly activated by Mg2+ ions as compared to Ca2+ ions. Although having a considerably higher specificity constant kcat/Km for ADP as for ATP, the bacterially expressed variant of NTPDase1 in contrast to its wild type counterpart releases intermediate ADP to a substantial amount. The presented expression system will allow large scale production of active protein suitable for structural studies, development of inhibitors, and even clinical application.
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Affiliation(s)
- Matthias Zebisch
- Center for Biotechnology and Biomedicine, Institute of Bioanalytical Chemistry, Faculty of Chemistry and Mineralogy, University of Leipzig, Deutscher Platz 5, 04103 Leipzig, Germany
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21
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Iandiev I, Wurm A, Pannicke T, Wiedemann P, Reichenbach A, Robson SC, Zimmermann H, Bringmann A. Ectonucleotidases in Müller glial cells of the rodent retina: Involvement in inhibition of osmotic cell swelling. Purinergic Signal 2007; 3:423-33. [PMID: 18404455 PMCID: PMC2072913 DOI: 10.1007/s11302-007-9061-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 07/10/2007] [Indexed: 11/20/2022] Open
Abstract
Extracellular nucleotides mediate glia-to-neuron signalling in the retina and are implicated in the volume regulation of retinal glial (Müller) cells under osmotic stress conditions. We investigated the expression and functional role of ectonucleotidases in Müller cells of the rodent retina by cell-swelling experiments, calcium imaging, and immuno- and enzyme histochemistry. The swelling of Müller cells under hypoosmotic stress was inhibited by activation of an autocrine purinergic signalling cascade. This cascade is initiated by exogenous glutamate and involves the consecutive activation of P2Y1 and adenosine A1 receptors, the action of ectoadenosine 5′-triphosphate (ATP)ases, and a nucleoside-transporter-mediated release of adenosine. Inhibition of ectoapyrases increased the ATP-evoked calcium responses in Müller cell endfeet. Müller cells were immunoreactive for nucleoside triphosphate diphosphohydrolases (NTPDase)2 (but not NTPDase1), ecto-5′-nucleotidase, P2Y1, and A1 receptors. Enzyme histochemistry revealed that ATP but not adenosine 5′-diphosphate (ADP) is extracellularly metabolised in retinal slices of NTPDase1 knockout mice. NTPDase1 activity and protein is restricted to blood vessels, whereas activity of alkaline phosphatase is essentially absent at physiological pH. The data suggest that NTPDase2 is the major ATP-degrading ectonucleotidase of the retinal parenchyma. NTPDase2 expressed by Müller cells can be implicated in the regulation of purinergic calcium responses and cellular volume.
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Affiliation(s)
- Ianors Iandiev
- Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany
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22
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Grinthal A, Guidotti G. Bilayer mechanical properties regulate the transmembrane helix mobility and enzymatic state of CD39. Biochemistry 2007; 46:279-90. [PMID: 17198399 PMCID: PMC2536646 DOI: 10.1021/bi061052p] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
CD39 can exist in at least two distinct functional states depending on the presence and intact membrane integration of its two transmembrane helices. In native membranes, the transmembrane helices undergo dynamic rotational motions that are required for enzymatic activity and are regulated by substrate binding. In this study, we show that bilayer mechanical properties regulate conversion between the two enzymatic functional states by modulating transmembrane helix dynamics. Alteration of membrane properties by insertion of cone-shaped or inverse cone-shaped amphiphiles or by cholesterol removal switches CD39 to the same enzymatic state that removal or solubilization of the transmembrane domains does. The same membrane alterations increase the propensity of both transmembrane helices to rotate within the packed structure, resulting in a structure with greater mobility but not an altered primary conformation. Membrane alteration also abolishes the ability of the substrate to stabilize the helices in their primary conformation, indicating a loss of coupling between substrate binding and transmembrane helix dynamics. Removal of either transmembrane helix mimics the effect of membrane alteration on the mobility and substrate sensitivity of the remaining helix, suggesting that the ends of the extracellular domain have intrinsic flexibility. We suggest that a mechanical bilayer property, potentially elasticity, regulates CD39 by altering the balance between the stability and flexibility of its transmembrane helices and, in turn, of its active site.
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Affiliation(s)
- Alison Grinthal
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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23
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Musi E, Islam N, Drosopoulos JHF. Constraints imposed by transmembrane domains affect enzymatic activity of membrane-associated human CD39/NTPDase1 mutants. Arch Biochem Biophys 2007; 461:30-9. [PMID: 17374358 DOI: 10.1016/j.abb.2007.02.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Revised: 02/02/2007] [Accepted: 02/03/2007] [Indexed: 01/30/2023]
Abstract
Human CD39/NTPDase1 is an endothelial cell membrane-associated nucleotidase. Its large extracellular domain rapidly metabolizes nucleotides, especially ADP released from activated platelets, inhibiting further platelet activation/recruitment. Previous studies using our recombinant soluble CD39 demonstrated the importance of residues S57, D54, and D213 for enzymatic/biological activity. We now report effects of S57A, D54A, and D213A mutations on full-length (FL)CD39 function. Enzymatic activity of alanine modified FLCD39s was less than wild-type, contrasting the enhanced activity of their soluble counterparts. Furthermore, conservative substitutions D54E and D213E led to enzymes with activities greater than the alanine modified FLCD39s, but less than wild-type. Reductions in mutant activities were primarily associated with reduced catalytic rates. Differences in enzymatic activity were not attributable to gross changes in the nucleotide binding pocket or the enzyme's ability to multimerize. Thus, composition of the active site of wild-type CD39 appears optimized for ADPase function in the context of the transmembrane domains.
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Affiliation(s)
- Elgilda Musi
- Thrombosis Research Laboratory, Research Service, Room 13026W, VA New York Harbor Healthcare System, 423 East 23rd Street, New York, NY 10010-5050, USA
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24
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Krause F. Detection and analysis of protein–protein interactions in organellar and prokaryotic proteomes by native gel electrophoresis: (Membrane) protein complexes and supercomplexes. Electrophoresis 2006; 27:2759-81. [PMID: 16817166 DOI: 10.1002/elps.200600049] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
It is an essential and challenging task to unravel protein-protein interactions in their actual in vivo context. Native gel systems provide a separation platform allowing the analysis of protein complexes on a rather proteome-wide scale in a single experiment. This review focus on blue-native (BN)-PAGE as the most versatile and successful gel-based approach to separate soluble and membrane protein complexes of intricate protein mixtures derived from all biological sources. BN-PAGE is a charge-shift method with a running pH of 7.5 relying on the gentle binding of anionic CBB dye to all membrane and many soluble protein complexes, leading to separation of protein species essentially according to their size and superior resolution than other fractionation techniques can offer. The closely related colorless-native (CN)-PAGE, whose applicability is restricted to protein species with intrinsic negative net charge, proved to provide an especially mild separation capable of preserving weak protein-protein interactions better than BN-PAGE. The essential conditions determining the success of detecting protein-protein interactions are the sample preparations, e.g. the efficiency/mildness of the detergent solubilization of membrane protein complexes. A broad overview about the achievements of BN- and CN-PAGE studies to elucidate protein-protein interactions in organelles and prokaryotes is presented, e.g. the mitochondrial protein import machinery and oxidative phosphorylation supercomplexes. In many cases, solubilization with digitonin was demonstrated to facilitate an efficient and particularly gentle extraction of membrane protein complexes prone to dissociation by treatment with other detergents. In general, analyses of protein interactomes should be carried out by both BN- and CN-PAGE.
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Affiliation(s)
- Frank Krause
- Department of Chemistry, Physical Biochemistry, Darmstadt University of Technology, Germany.
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25
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Faudry E, Santana J, Ebel C, Vernet T, Teixeira A. Salivary apyrases of Triatoma infestans are assembled into homo-oligomers. Biochem J 2006; 396:509-15. [PMID: 16542158 PMCID: PMC1482816 DOI: 10.1042/bj20052019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Apyrase activity is present in the saliva of haematophagous arthropods. It is related to blood-feeding because of the apyrase ability to hydrolyse ADP, a key component of platelet aggregation. Five apyrases with apparent molecular masses of 88, 82, 79, 68 and 67 kDa were identified in the saliva of the vector of Chagas disease, Triatoma infestans. The large size observed during purification of these enzymes suggested oligomerization. In the present study, we confirmed, using gel-filtration and analytical ultracentrifugation, the presence of apyrase oligomers with molecular masses of 200 kDa in the saliva. Electrophoretic analyses showed that disulphide bonds were involved in homo-oligomerization. In addition, heterogeneity in disulphide bonds and in pI was detected, with the pI ranging from 4.9 to 5.4. The present study gives the first insights into the quaternary structure of soluble apyrases.
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Affiliation(s)
- Eric Faudry
- *Chagas Disease Multidisciplinary Research Laboratory, Faculty of Medicine, University of Brasilia, Brazil 70.910-900
- †Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale J.P. Ebel UMR5075 CEA/CNRS/UJF, 38027 Grenoble cedex 1, France
| | - Jaime M. Santana
- *Chagas Disease Multidisciplinary Research Laboratory, Faculty of Medicine, University of Brasilia, Brazil 70.910-900
| | - Christine Ebel
- ‡Laboratoire de Biophysique Moléculaire, Institut de Biologie Structurale J.P. Ebel UMR5075 CEA/CNRS/UJF, 38027 Grenoble cedex 1, France
| | - Thierry Vernet
- †Laboratoire d'Ingénierie des Macromolécules, Institut de Biologie Structurale J.P. Ebel UMR5075 CEA/CNRS/UJF, 38027 Grenoble cedex 1, France
| | - Antonio R. L. Teixeira
- *Chagas Disease Multidisciplinary Research Laboratory, Faculty of Medicine, University of Brasilia, Brazil 70.910-900
- To whom correspondence should be addressed (email )
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Robson SC, Sévigny J, Zimmermann H. The E-NTPDase family of ectonucleotidases: Structure function relationships and pathophysiological significance. Purinergic Signal 2006; 2:409-30. [PMID: 18404480 PMCID: PMC2254478 DOI: 10.1007/s11302-006-9003-5] [Citation(s) in RCA: 712] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 01/23/2006] [Indexed: 12/17/2022] Open
Abstract
Ectonucleotidases are ectoenzymes that hydrolyze extracellular nucleotides to the respective nucleosides. Within the past decade, ectonucleotidases belonging to several enzyme families have been discovered, cloned and characterized. In this article, we specifically address the cell surface-located members of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase/CD39) family (NTPDase1,2,3, and 8). The molecular identification of individual NTPDase subtypes, genetic engineering, mutational analyses, and the generation of subtype-specific antibodies have resulted in considerable insights into enzyme structure and function. These advances also allow definition of physiological and patho-physiological implications of NTPDases in a considerable variety of tissues. Biological actions of NTPDases are a consequence (at least in part) of the regulated phosphohydrolytic activity on extracellular nucleotides and consequent effects on P2-receptor signaling. It further appears that the spatial and temporal expression of NTPDases by various cell types within the vasculature, the nervous tissues and other tissues impacts on several patho-physiological processes. Examples include acute effects on cellular metabolism, adhesion, activation and migration with other protracted impacts upon developmental responses, inclusive of cellular proliferation, differentiation and apoptosis, as seen with atherosclerosis, degenerative neurological diseases and immune rejection of transplanted organs and cells. Future clinical applications are expected to involve the development of new therapeutic strategies for transplantation and various inflammatory cardiovascular, gastrointestinal and neurological diseases.
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Affiliation(s)
- Simon C. Robson
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts USA
| | - Jean Sévigny
- Centre de Recherche en Rhumatologie et Immunologie, Université Laval, Québec, Québec Canada
| | - Herbert Zimmermann
- Institut fuer Zellbiologie und Neurowissenschaft, Biozentrum der J.W. Goethe-Universitaet, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
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27
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CD39, NTPDase 1, is attached to the plasma membrane by two transmembrane domains. Why? Purinergic Signal 2006; 2:391-8. [PMID: 18404478 PMCID: PMC2254477 DOI: 10.1007/s11302-005-5907-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Revised: 12/14/2005] [Accepted: 12/14/2005] [Indexed: 11/20/2022] Open
Abstract
Since the identification of CD39 and other members of the e-NTPDase (ecto-nucleoside triphosphate diphosphohydrolase) family as the primary enzymes responsible for cell surface nucleotide hydrolysis, one of their most intriguing features has been their unusual topology. The active site lies in the large extracellular region, but instead of being anchored in the membrane by a single transmembrane domain or lipid link like other ectoenzymes, CD39 has two transmembrane domains, one at each end. In this review we discuss evidence that the structure and dynamics of the transmembrane helices are intricately connected to enzymatic function. Removal of either or both transmembrane domains or disruption of their native state by detergent solubilization reduces activity by 90%, indicating that native function requires both transmembrane domains to be present and in the membrane. Enzymatic and mutational analysis of the native and truncated forms has shown that the active site can exist in distinct functional states characterized by different total activities, substrate specificities, hydrolysis mechanisms, and intermediate ADP release during ATP hydrolysis, depending on the state of the transmembrane domains. Disulfide crosslinking of cysteines introduced within the transmembrane helices revealed that they interact within and between molecules, in particular near the extracellular domain, and that activity depends on their organization. Both helices exhibit a high degree of rotational mobility, and the ability to undergo dynamic motions is required for activity and regulated by substrate binding. Recent reports suggest that membrane composition can regulate NTPDase activity. We propose that mechanical bilayer properties, potentially elasticity, might regulate CD39 by altering the balance between stability and mobility of its transmembrane domains.
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28
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Sahoo D, Darlington YF, Pop D, Williams DL, Connelly MA. Scavenger receptor class B Type I (SR-BI) assembles into detergent-sensitive dimers and tetramers. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1771:807-17. [PMID: 16624615 DOI: 10.1016/j.bbalip.2006.03.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Revised: 01/09/2006] [Accepted: 03/06/2006] [Indexed: 12/13/2022]
Abstract
High density lipoproteins (HDL) are protective against cardiovascular disease due to their important role in the reverse cholesterol transport (RCT) pathway. The selective transfer of cholesteryl ester (CE) from the HDL core to cells, the last step in RCT, is mediated by scavenger receptor class B type I (SR-BI). SR-BI is a heavily glycosylated cell surface receptor that is highly expressed in the liver, ovaries, testes and adrenal glands, where selective uptake of HDL-CE is most prevalent. Previous studies have shown that SR-BI oligomerizes with itself in steroidogenic tissues as well as in diverse cell lines. In the present study, we provide further evidence for the homo-oligomerization of SR-BI. We show by FPLC and blue native PAGE that SR-BI forms complexes whose sizes suggest the formation of monomers, dimers, and tetramers. Interestingly, homo-oligomerization occurs even with the absence of SR-BI's C-terminal cytoplasmic domain. Finally, we report that an inhibitor of SR-BI-mediated cholesterol transport, BLT-1, and mutations in the putative leucine zipper region of SR-BI have profound effects on SR-BI function, however, they do not affect receptor self-association. These observations indicate that SR-BI homo-oligomerization occurs even when the receptor is non-functional.
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Affiliation(s)
- Daisy Sahoo
- Department of Pharmacological Sciences, University Medical Center, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
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Comparative hydrolysis of P2 receptor agonists by NTPDases 1, 2, 3 and 8. Purinergic Signal 2005; 1:193-204. [PMID: 18404504 PMCID: PMC2096530 DOI: 10.1007/s11302-005-6217-x] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Accepted: 10/19/2004] [Indexed: 11/16/2022] Open
Abstract
Nucleoside triphosphate diphosphohydrolases 1, 2, 3 and 8 (NTPDases 1, 2, 3 and 8) are the dominant ectonucleotidases and thereby expected to play important roles in nucleotide signaling. Distinct biochemical characteristics of individual NTPDases should allow them to regulate P2 receptor activation differentially. Therefore, the biochemical and kinetic properties of these enzymes were compared. NTPDases 1, 2, 3 and 8 efficiently hydrolyzed ATP and UTP with Km values in the micromolar range, indicating that they should terminate the effects exerted by these nucleotide agonists at P2X1- and P2Y2,4,11 receptors. Since NTPDase1 does not allow accumulation of ADP, it should terminate the activation of P2Y1,12,13 receptors far more efficiently than the other NTPDases. In contrast, NTPDases 2, 3 and 8 are expected to promote the activation of ADP specific receptors, because in the presence of ATP they produce a sustained (NTPDase2) or transient (NTPDases 3 and 8) accumulation of ADP. Interestingly, all plasma membrane NTPDases dephosphorylate UTP with a significant accumulation of UDP, favoring P2Y6 receptor activation. NTPDases differ in divalent cation and pH dependence, although all are active in the pH range of 7.0-.5. Various NTPDases may also distinctly affect formation of extracellular adenosine and therefore adenosine receptor-mediated responses, since they generate different amounts of the substrate (AMP) and inhibitor (ADP) of ecto-5-nucleotidase, the rate limiting enzyme in the production of adenosine. Taken together, these data indicate that plasma membrane NTPDases hydrolyze nucleotides in a distinctive manner and may therefore differentially regulate P2 and adenosine receptor signaling.
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30
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Grinthal A, Guidotti G. Dynamic Motions of CD39 Transmembrane Domains Regulate and Are Regulated by the Enzymatic Active Site†. Biochemistry 2004; 43:13849-58. [PMID: 15504047 DOI: 10.1021/bi048644x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The two transmembrane domains flanking the active site of CD39 regulate its activity, but little is known about the structural and dynamic features underlying their importance. Here we use a disulfide crosslinking strategy to examine transmembrane helix interactions and dynamics and to correlate these features with activity and substrate binding. We find strong intrasubunit TM1-TM2 interactions, as well as TM1-TM1' and TM2-TM2' interactions between dimer subunits, near the extracellular side of the membrane but only weak interactions near the cytoplasmic end. The specific helix faces that constitute each interface are highly flexible, indicating a significant degree of rotational mobility within the packed structure. Analysis of activity after locking the helices in various orientations via disulfide bonds suggests that not only the arrangement but also the ability of the helices to move relative to each other is crucial for enzyme function. Helix mobility is in turn modulated by substrate binding. These results suggest that rather than playing a static structural role to support an optimal active site conformation, the transmembrane domains undergo dynamic motions that underlie their functional relationship with the active site.
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Affiliation(s)
- Alison Grinthal
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
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31
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Rettinger J, Schmalzing G. Desensitization masks nanomolar potency of ATP for the P2X1 receptor. J Biol Chem 2003; 279:6426-33. [PMID: 14625300 DOI: 10.1074/jbc.m306987200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP-gated P2X1 receptors feature fast activation and fast desensitization combined with slow recovery from desensitized states. Here, we exploited a non-desensitizing P2X2/P2X1 chimera that includes the entire P2X1 ectodomain (Werner, P., Seward, E. P., Buell, G. N., and North, R. A. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 15485-15490) to obtain a macroscopic representation of intrinsic receptor kinetics without bias arising from the overlap of channel activation and desensitization. From the stationary currents made amenable to analysis by this chimera, an EC50 for ATP of 3.3 nM was derived, representing a >200- and >7000-fold higher ATP potency than observed for the parental P2X1 and P2X2A receptors, respectively. Also, other agonists activated the P2X2/P2X1 chimera with nanomolar EC50 values ranging from 3.5 to 73 nM in the following rank order: 2-methylthio-ATP, 2',3'-O-(4-benzoylbenzoyl)-ATP, alpha,beta-methylene-ATP, adenosine 5'-O-(3-thiotriphosphate). Upon washout, the P2X2/P2X1 chimera deactivated slowly with a time constant (ranging from 63 to 2.5 s) that is inversely related to the EC50 value for the corresponding agonist. This suggests that deactivation time courses reflect unbinding rates, which by themselves define agonist potencies. The P2X2/P2X1 chimera and the P2X1 receptor possess virtually identical sensitivity to inhibition by the P2X1 receptor-selective antagonist NF279, a suramin analog. These results suggest that the P2X1 ectodomain confers nanomolar ATP sensitivity, which, within the wild-type P2X1 receptor, is obscured by desensitization such that only a micromolar ATP potency can be deduced from peak current measurements, representing an amalgam of activation and desensitization.
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Affiliation(s)
- Jürgen Rettinger
- Max Planck Institute of Biophysics, Marie-Curie-Strasse 13-15, D-60439 Frankfurt am Main, Germany
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32
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Mateo J, Kreda S, Henry CE, Harden TK, Boyer JL. Requirement of Cys399 for processing of the human ecto-ATPase (NTPDase2) and its implications for determination of the activities of splice variants of the enzyme. J Biol Chem 2003; 278:39960-8. [PMID: 12888562 DOI: 10.1074/jbc.m307854200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Ecto-ATPase (CD39L1) corresponds to the type 2 enzyme of the ecto-nucleoside triphosphate diphosphohydrolase family (E-NTPDase). We have isolated from human ECV304 cells three cDNAs with high homology with members of the E-NTPDase family that encode predicted proteins of 495, 472, and 450 amino acids. Sequencing of a genomic DNA clone confirmed that these three sequences correspond to splice variants of the human ecto-ATPase (NTPDase2 alpha,-2 beta, and -2 gamma). Although all three enzyme forms were expressed heterologously to similar levels in Chinese hamster ovary cells clone K-1 (CHO-K1) cells, only the 495-amino acid protein (NTPDase2 alpha exhibited ecto-ATPase activity. Immunolocalization studies demonstrated that NTPDase2 alpha is fully processed and trafficked to the plasma membrane, whereas the NTPDase2 beta and -2 gamma splice variants were retained in not fully glycosylated forms in the endoplasmic reticulum. The potential roles of two highly conserved residues, Cys399 and Asn443, in the activity and cellular trafficking of the ecto-ATPase were examined. Mutation of Cys399, which is absent in NTPDase2 beta and -2 gamma, produced a protein completely devoid of nucleotidase activity, while mutation of Asn443 to Asp resulted in substantial loss of activity. Neither the Cys399 nor Asn443 mutants were fully glycosylated, and both were retained in the endoplasmic reticulum. These results indicate that the lack of ecto-nucleotidase activity exhibited by NTPDase2 beta and -2 gamma and the C399S mutant, as well as the large reduction of activity in the N443D mutant are due to alterations in the folding/maturation of these proteins.
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Affiliation(s)
- Jesús Mateo
- Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7365, USA
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