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Becker HM, Deitmer JW. Proton Transport in Cancer Cells: The Role of Carbonic Anhydrases. Int J Mol Sci 2021; 22:ijms22063171. [PMID: 33804674 PMCID: PMC8003680 DOI: 10.3390/ijms22063171] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 02/06/2023] Open
Abstract
Intra- and extracellular pH regulation is a pivotal function of all cells and tissues. Net outward transport of H+ is a prerequisite for normal physiological function, since a number of intracellular processes, such as metabolism and energy supply, produce acid. In tumor tissues, distorted pH regulation results in extracellular acidification and the formation of a hostile environment in which cancer cells can outcompete healthy local host cells. Cancer cells employ a variety of H+/HCO3−-coupled transporters in combination with intra- and extracellular carbonic anhydrase (CA) isoforms, to alter intra- and extracellular pH to values that promote tumor progression. Many of the transporters could closely associate to CAs, to form a protein complex coined “transport metabolon”. While transport metabolons built with HCO3−-coupled transporters require CA catalytic activity, transport metabolons with monocarboxylate transporters (MCTs) operate independently from CA catalytic function. In this article, we assess some of the processes and functions of CAs for tumor pH regulation and discuss the role of intra- and extracellular pH regulation for cancer pathogenesis and therapeutic intervention.
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Affiliation(s)
- Holger M. Becker
- Zoology and Animal Physiology, Institute of Zoology, TU Dresden, D-01217 Dresden, Germany
- Correspondence:
| | - Joachim W. Deitmer
- Department of Biology, University of Kaiserslautern, D-67653 Kaiserslautern, Germany;
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Duscha K, Martins Rodrigues C, Müller M, Wartenberg R, Fliegel L, Deitmer JW, Jung M, Zimmermann R, Neuhaus HE. 14-3-3 Proteins and Other Candidates form Protein-Protein Interactions with the Cytosolic C-terminal End of SOS1 Affecting Its Transport Activity. Int J Mol Sci 2020; 21:ijms21093334. [PMID: 32397251 PMCID: PMC7246916 DOI: 10.3390/ijms21093334] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 04/30/2020] [Accepted: 05/06/2020] [Indexed: 01/18/2023] Open
Abstract
The plasma membrane transporter SOS1 (SALT-OVERLY SENSITIVE1) is vital for plant survival under salt stress. SOS1 activity is tightly regulated, but little is known about the underlying mechanism. SOS1 contains a cytosolic, autoinhibitory C-terminal tail (abbreviated as SOS1 C-term), which is targeted by the protein kinase SOS2 to trigger its transport activity. Here, to identify additional binding proteins that regulate SOS1 activity, we synthesized the SOS1 C-term domain and used it as bait to probe Arabidopsis thaliana cell extracts. Several 14-3-3 proteins, which function in plant salt tolerance, specifically bound to and interacted with the SOS1 C-term. Compared to wild-type plants, when exposed to salt stress, Arabidopsis plants overexpressing SOS1 C-term showed improved salt tolerance, significantly reduced Na+ accumulation in leaves, reduced induction of the salt-responsive gene WRKY25, decreased soluble sugar, starch, and proline levels, less impaired inflorescence formation and increased biomass. It appears that overexpressing SOS1 C-term leads to the sequestration of inhibitory 14-3-3 proteins, allowing SOS1 to be more readily activated and leading to increased salt tolerance. We propose that the SOS1 C-term binds to previously unknown proteins such as 14-3-3 isoforms, thereby regulating salt tolerance. This finding uncovers another regulatory layer of the plant salt tolerance program.
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Affiliation(s)
- Kerstin Duscha
- Department of Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany; (K.D.); (C.M.R.); (M.M.); (R.W.)
| | - Cristina Martins Rodrigues
- Department of Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany; (K.D.); (C.M.R.); (M.M.); (R.W.)
| | - Maria Müller
- Department of Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany; (K.D.); (C.M.R.); (M.M.); (R.W.)
| | - Ruth Wartenberg
- Department of Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany; (K.D.); (C.M.R.); (M.M.); (R.W.)
| | - Larry Fliegel
- Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, 347 Medical Sciences Building, Edmonton, AB T6G 2H7, Canada;
| | - Joachim W. Deitmer
- Department of Zoology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany;
| | - Martin Jung
- Department of Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, D-66421 Homburg, Germany; (M.J.); (R.Z.)
| | - Richard Zimmermann
- Department of Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, D-66421 Homburg, Germany; (M.J.); (R.Z.)
| | - H. Ekkehard Neuhaus
- Department of Plant Physiology, University of Kaiserslautern, Erwin-Schrödinger-Str., D-67653 Kaiserslautern, Germany; (K.D.); (C.M.R.); (M.M.); (R.W.)
- Correspondence: ; Tel.: +49-631-2052372; Fax: +49-631-205-2600
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3
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Becker HM, Deitmer JW. Transport Metabolons and Acid/Base Balance in Tumor Cells. Cancers (Basel) 2020; 12:cancers12040899. [PMID: 32272695 PMCID: PMC7226098 DOI: 10.3390/cancers12040899] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 02/07/2023] Open
Abstract
Solid tumors are metabolically highly active tissues, which produce large amounts of acid. The acid/base balance in tumor cells is regulated by the concerted interplay between a variety of membrane transporters and carbonic anhydrases (CAs), which cooperate to produce an alkaline intracellular, and an acidic extracellular, environment, in which cancer cells can outcompete their adjacent host cells. Many acid/base transporters form a structural and functional complex with CAs, coined "transport metabolon". Transport metabolons with bicarbonate transporters require the binding of CA to the transporter and CA enzymatic activity. In cancer cells, these bicarbonate transport metabolons have been attributed a role in pH regulation and cell migration. Another type of transport metabolon is formed between CAs and monocarboxylate transporters, which mediate proton-coupled lactate transport across the cell membrane. In this complex, CAs function as "proton antenna" for the transporter, which mediate the rapid exchange of protons between the transporter and the surroundings. These transport metabolons do not require CA catalytic activity, and support the rapid efflux of lactate and protons from hypoxic cancer cells to allow sustained glycolytic activity and cell proliferation. Due to their prominent role in tumor acid/base regulation and metabolism, transport metabolons might be promising drug targets for new approaches in cancer therapy.
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Affiliation(s)
- Holger M. Becker
- Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559 Hannover, Germany
- Correspondence:
| | - Joachim W. Deitmer
- Department of Biology, University of Kaiserslautern, D-67653 Kaiserslautern, Germany;
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Deitmer JW, Theparambil SM, Ruminot I, Noor SI, Becker HM. Energy Dynamics in the Brain: Contributions of Astrocytes to Metabolism and pH Homeostasis. Front Neurosci 2019; 13:1301. [PMID: 31866811 PMCID: PMC6909239 DOI: 10.3389/fnins.2019.01301] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 11/20/2019] [Indexed: 12/17/2022] Open
Abstract
Regulation of metabolism is complex and involves enzymes and membrane transporters, which form networks to support energy dynamics. Lactate, as a metabolic intermediate from glucose or glycogen breakdown, appears to play a major role as additional energetic substrate, which is shuttled between glycolytic and oxidative cells, both under hypoxic and normoxic conditions. Transport of lactate across the cell membrane is mediated by monocarboxylate transporters (MCTs) in cotransport with H+, which is a substrate, a signal and a modulator of metabolic processes. MCTs form a “transport metabolon” with carbonic anhydrases (CAs), which not only provide a rapid equilibrium between CO2, HCO3– and H+, but, in addition, enhances lactate transport, as found in Xenopus oocytes, employed as heterologous expression system, as well as in astrocytes and cancer cells. Functional interactions between different CA isoforms and MCTs have been found to be isoform-specific, independent of the enzyme’s catalytic activity, and they require physical interaction between the proteins. CAs mediate between different states of metabolic acidosis, induced by glycolysis and oxidative phosphorylation, and play a relay function in coupling pH regulation and metabolism. In the brain, metabolic processes in astrocytes appear to be linked to bicarbonate transport and to neuronal activity. Here, we focus on physiological processes of energy dynamics in astrocytes as well as on the transfer of energetic substrates to neurons.
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Affiliation(s)
- Joachim W Deitmer
- Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | | | - Sina I Noor
- Centre for Organismal Studies, Heidelberg University, Heidelberg, Germany
| | - Holger M Becker
- Institute of Physiological Chemistry, University of Veterinary Medicine Hanover, Hanover, Germany
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Khakipoor S, Giannaki M, Theparambil SM, Zecha J, Küster B, Heermann S, Deitmer JW, Roussa E. Functional expression of electrogenic sodium bicarbonate cotransporter 1 (NBCe1) in mouse cortical astrocytes is dependent on S255‐257 and regulated by mTOR. Glia 2019; 67:2264-2278. [DOI: 10.1002/glia.23682] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 06/23/2019] [Accepted: 07/03/2019] [Indexed: 01/14/2023]
Affiliation(s)
- Shokoufeh Khakipoor
- Department of Molecular Embryology, Faculty of Medicine Institute of Anatomy and Cell Biology, Albert‐Ludwigs‐Universität Freiburg Freiburg Germany
| | - Marina Giannaki
- Department of Molecular Embryology, Faculty of Medicine Institute of Anatomy and Cell Biology, Albert‐Ludwigs‐Universität Freiburg Freiburg Germany
| | - Shefeeq M. Theparambil
- Department of General Zoology, FB Biology University of Kaiserslautern Kaiserslautern Germany
| | - Jana Zecha
- Chair of Proteomics and Bioanalytics Technical University of Munich Freising Germany
| | - Bernhard Küster
- Chair of Proteomics and Bioanalytics Technical University of Munich Freising Germany
- Bavarian Biomolecular Mass Spectrometry Center (BayBioMS) Technical University of Munich Freising Germany
| | - Stephan Heermann
- Department of Molecular Embryology, Faculty of Medicine Institute of Anatomy and Cell Biology, Albert‐Ludwigs‐Universität Freiburg Freiburg Germany
| | - Joachim W. Deitmer
- Department of General Zoology, FB Biology University of Kaiserslautern Kaiserslautern Germany
| | - Eleni Roussa
- Department of Molecular Embryology, Faculty of Medicine Institute of Anatomy and Cell Biology, Albert‐Ludwigs‐Universität Freiburg Freiburg Germany
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Aspatwar A, Tolvanen MEE, Schneider HP, Becker HM, Narkilahti S, Parkkila S, Deitmer JW. Catalytically inactive carbonic anhydrase-related proteins enhance transport of lactate by MCT1. FEBS Open Bio 2019; 9:1204-1211. [PMID: 31033227 PMCID: PMC6609565 DOI: 10.1002/2211-5463.12647] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/22/2019] [Accepted: 04/26/2019] [Indexed: 11/12/2022] Open
Abstract
Carbonic anhydrases (CA) catalyze the reversible hydration of CO2 to protons and bicarbonate and thereby play a fundamental role in the epithelial acid/base transport mechanisms serving fluid secretion and absorption for whole‐body acid/base regulation. The three carbonic anhydrase‐related proteins (CARPs) VIII, X, and XI, however, are catalytically inactive. Previous work has shown that some CA isoforms noncatalytically enhance lactate transport through various monocarboxylate transporters (MCT). Therefore, we examined whether the catalytically inactive CARPs play a role in lactate transport. Here, we report that CARP VIII, X, and XI enhance transport activity of the MCT MCT1 when coexpressed in Xenopus oocytes, as evidenced by the rate of rise in intracellular H+ concentration detected using ion‐sensitive microelectrodes. Based on previous studies, we suggest that CARPs may function as a ‘proton antenna’ for MCT1, to drive proton‐coupled lactate transport across the cell membrane.
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Affiliation(s)
- Ashok Aspatwar
- Faculty of Medicine and Health Technology, Tampere University, Finland
| | | | | | - Holger M Becker
- Division of General Zoology, FB Biologie, TU Kaiserslautern, Germany
| | | | - Seppo Parkkila
- Faculty of Medicine and Health Technology, Tampere University, Finland
| | - Joachim W Deitmer
- Division of General Zoology, FB Biologie, TU Kaiserslautern, Germany
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Ruminot I, Schmälzle J, Leyton B, Barros LF, Deitmer JW. Tight coupling of astrocyte energy metabolism to synaptic activity revealed by genetically encoded FRET nanosensors in hippocampal tissue. J Cereb Blood Flow Metab 2019; 39:513-523. [PMID: 29083247 PMCID: PMC6421254 DOI: 10.1177/0271678x17737012] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The potassium ion, K+, a neuronal signal that is released during excitatory synaptic activity, produces acute activation of glucose consumption in cultured astrocytes, a phenomenon mediated by the sodium bicarbonate cotransporter NBCe1 ( SLC4A4). We have explored here the relevance of this mechanism in brain tissue by imaging the effect of neuronal activity on pH, glucose, pyruvate and lactate dynamics in hippocampal astrocytes using BCECF and FRET nanosensors. Electrical stimulation of Schaffer collaterals produced fast activation of glucose consumption in astrocytes with a parallel increase in intracellular pyruvate and biphasic changes in lactate . These responses were blocked by TTX and were absent in tissue slices prepared from NBCe1-KO mice. Direct depolarization of astrocytes with elevated extracellular K+ or Ba2+ mimicked the metabolic effects of electrical stimulation. We conclude that the glycolytic pathway of astrocytes in situ is acutely sensitive to neuronal activity, and that extracellular K+ and the NBCe1 cotransporter are involved in metabolic crosstalk between neurons and astrocytes. Glycolytic activation of astrocytes in response to neuronal K+ helps to provide an adequate supply of lactate, a metabolite that is released by astrocytes and which acts as neuronal fuel and an intercellular signal.
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Affiliation(s)
- Iván Ruminot
- 1 Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany.,2 Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - Jana Schmälzle
- 1 Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Belén Leyton
- 2 Centro de Estudios Científicos (CECs), Valdivia, Chile.,3 Universidad Austral de Chile, Valdivia, Chile
| | | | - Joachim W Deitmer
- 1 Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
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8
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Hiremath SA, Surulescu C, Jamali S, Ames S, Deitmer JW, Becker HM. Modeling of pH regulation in tumor cells: Direct interaction between proton-coupled lactate transporters and cancer-associated carbonic anhydrase. Math Biosci Eng 2018; 16:320-337. [PMID: 30674122 DOI: 10.3934/mbe.2019016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The most aggressive tumor cells, which often reside in a hypoxic environment, can release vast amounts of lactate and protons via monocarboxylate transporters (MCTs). This additional proton efflux exacerbates extracellular acidification and supports the formation of a hostile environment. In the present study we propose a novel, data-based model for this proton-coupled lactate transport in cancer cells. The mathematical settings involve systems coupling nonlinear ordinary and stochastic differential equations describing the dynamics of intra- and extracellular proton and lactate concentrations. The data involve time series of intracellular proton concentrations of normoxic and hypoxic MCF-7 breast cancer cells. The good agreement of our final model with the data suggests the existence of proton pools near the cell membrane, which can be controlled by intracellular and extracellular carbonic anhydrases to drive proton-coupled lactate transport across the plasma membrane of hypoxic cancer cells.
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Affiliation(s)
- Sandesh Athni Hiremath
- Technische Universität Kaiserslautern (TUK) Felix-Klein-Zentrum für Mathematik Paul-Ehrlich-Str. 31, 67663 Kaiserslautern, Germany
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Forero-Quintero LS, Ames S, Schneider HP, Thyssen A, Boone CD, Andring JT, McKenna R, Casey JR, Deitmer JW, Becker HM. Membrane-anchored carbonic anhydrase IV interacts with monocarboxylate transporters via their chaperones CD147 and GP70. J Biol Chem 2018; 294:593-607. [PMID: 30446621 DOI: 10.1074/jbc.ra118.005536] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 11/12/2018] [Indexed: 12/20/2022] Open
Abstract
Monocarboxylate transporters (MCTs) mediate the proton-coupled exchange of high-energy metabolites, including lactate and pyruvate, between cells and tissues. The transport activity of MCT1, MCT2, and MCT4 can be facilitated by the extracellular carbonic anhydrase IV (CAIV) via a noncatalytic mechanism. Combining physiological measurements in HEK-293 cells and Xenopus oocytes with pulldown experiments, we analyzed the direct interaction between CAIV and the two MCT chaperones basigin (CD147) and embigin (GP70). Our results show that facilitation of MCT transport activity requires direct binding of CAIV to the transporters chaperones. We found that this binding is mediated by the highly conserved His-88 residue in CAIV, which is also the central residue of the enzyme's intramolecular proton shuttle, and a charged amino acid residue in the Ig1 domain of the chaperone. Although the position of the CAIV-binding site in the chaperone was conserved, the amino acid residue itself varied among different species. In human CD147, binding of CAIV was mediated by the negatively charged Glu-73 and in rat CD147 by the positively charged Lys-73. In rat GP70, we identified the positively charged Arg-130 as the binding site. Further analysis of the CAIV-binding site revealed that the His-88 in CAIV can either act as H donor or H acceptor for the hydrogen bond, depending on the charge of the binding residue in the chaperone. Our results suggest that the CAIV-mediated increase in MCT transport activity requires direct binding between CAIV-His-88 and a charged amino acid in the extracellular domain of the transporter's chaperone.
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Affiliation(s)
- Linda S Forero-Quintero
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany
| | - Samantha Ames
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany
| | - Hans-Peter Schneider
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany
| | - Anne Thyssen
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany
| | - Christopher D Boone
- the Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
| | - Jacob T Andring
- the Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
| | - Robert McKenna
- the Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
| | - Joseph R Casey
- the Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2E1, Canada, and
| | - Joachim W Deitmer
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany
| | - Holger M Becker
- From the Division of General Zoology, Department of Biology, University of Kaiserlautern, D-67653 Kaiserslautern, Germany, .,the Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559 Hannover, Germany
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10
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Noor ZN, Deitmer JW, Theparambil SM. Cytosolic sodium regulation in mouse cortical astrocytes and its dependence on potassium and bicarbonate. J Cell Physiol 2018; 234:89-99. [PMID: 30132845 DOI: 10.1002/jcp.26824] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 04/30/2018] [Indexed: 11/10/2022]
Abstract
Sodium plays a major role in different astrocytic functions, including maintenance of ion homeostasis and uptake of neurotransmitters and metabolites, which are mediated by different Na+ -coupled transporters. In the current study, the role of an electrogenic sodium-bicarbonate cotransporter (NBCe1), a sodium-potassium-chloride transporter 1 (NKCC1) and sodium-potassium ATPase (Na+ -K+ -ATPase) for the maintenance of [Na+ ]i was investigated in cultured astrocytes of wild-type (WT) and of NBCe1-deficient (NBCe1-KO) mice using the Na+ -sensitive dye, asante sodium green-2. Our results suggest that cytosolic Na+ was higher in the presence of CO2 /HCO3 - (15 mM) than CO2 /HCO3 - -free, HEPES-buffered solution in WT, but not in NBCe1-KO astrocytes (12 mM). Surprisingly, there was a strong dependence of cytosolic [Na+ ] on the extracellular [HCO3 - ] attributable to NBCe1 activity. Pharmacological blockage of NKCC1 with bumetanide led to a robust drop in cytosolic Na+ in both WT and NBCe1-KO astrocytes by up to 6 mM. There was a strong dependence of the cytosolic [Na+ ] on the extracellular [K+ ]. Inhibition of the Na+ -K+ -ATPase led to larger increase in cytosolic Na+ , both in the absence of K+ as compared with the presence of ouabain and in NBCe1-KO astrocytes as compared with WT astrocytes. Our results show that cytosolic Na+ in mouse cortical astrocytes can vary considerably and depends greatly on the concentrations of HCO3 - and K+ , attributable to the activity of the Na+ -K+ -ATPase, of NBCe1 and NKCC1.
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Affiliation(s)
- Zinnia N Noor
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Kaiserslautern, Germany
| | - Shefeeq M Theparambil
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Kaiserslautern, Germany
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11
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Noor SI, Jamali S, Ames S, Langer S, Deitmer JW, Becker HM. A surface proton antenna in carbonic anhydrase II supports lactate transport in cancer cells. eLife 2018; 7:35176. [PMID: 29809145 PMCID: PMC5986270 DOI: 10.7554/elife.35176] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 05/17/2018] [Indexed: 01/08/2023] Open
Abstract
Many tumor cells produce vast amounts of lactate and acid, which have to be removed from the cell to prevent intracellular lactacidosis and suffocation of metabolism. In the present study, we show that proton-driven lactate flux is enhanced by the intracellular carbonic anhydrase CAII, which is colocalized with the monocarboxylate transporter MCT1 in MCF-7 breast cancer cells. Co-expression of MCTs with various CAII mutants in Xenopus oocytes demonstrated that CAII facilitates MCT transport activity in a process involving CAII-Glu69 and CAII-Asp72, which could function as surface proton antennae for the enzyme. CAII-Glu69 and CAII-Asp72 seem to mediate proton transfer between enzyme and transporter, but CAII-His64, the central residue of the enzyme's intramolecular proton shuttle, is not involved in proton shuttling between the two proteins. Instead, this residue mediates binding between MCT and CAII. Taken together, the results suggest that CAII features a moiety that exclusively mediates proton exchange with the MCT to facilitate transport activity.
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Affiliation(s)
- Sina Ibne Noor
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Somayeh Jamali
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Samantha Ames
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Silke Langer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Holger M Becker
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany.,Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
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12
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Khakipoor S, Ophoven C, Schrödl‐Häußel M, Feuerstein M, Heimrich B, Deitmer JW, Roussa E. TGF-β signaling directly regulates transcription and functional expression of the electrogenic sodium bicarbonate cotransporter 1, NBCe1 (SLC4A4), via Smad4 in mouse astrocytes. Glia 2017; 65:1361-1375. [PMID: 28568893 PMCID: PMC5518200 DOI: 10.1002/glia.23168] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 04/27/2017] [Accepted: 05/04/2017] [Indexed: 02/06/2023]
Abstract
The electrogenic sodium bicarbonate cotransporter NBCe1 (SLC4A4) expressed in astrocytes regulates intracellular and extracellular pH. Here, we introduce transforming growth factor beta (TGF-β) as a novel regulator of NBCe1 transcription and functional expression. Using hippocampal slices and primary hippocampal and cortical astrocyte cultures, we investigated regulation of NBCe1 and elucidated the underlying signaling pathways by RT-PCR, immunoblotting, immunofluorescence, intracellular H(+ ) recording using the H(+ ) -sensitive dye 2',7'-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein, mink lung epithelial cell (MLEC) assay, and chromatin immunoprecipitation. Activation of TGF-β signaling significantly upregulated transcript, protein, and surface expression of NBCe1. These effects were TGF-β receptor-mediated and suppressed following inhibition of JNK and Smad signaling. Moreover, 4-aminopyridine (4AP)-dependent NBCe1 regulation requires TGF-β. TGF-β increased the rate and amplitude of intracellular H+ changes upon challenging NBCe1 in wild-type astrocytes but not in cortical astrocytes from Slc4a4-deficient mice. A Smad4 binding sequence was identified in the NBCe1 promoter and Smad4 binding increased after activation of TGF-β signaling. The data show for the first time that NBCe1 is a direct target of TGF-β/Smad4 signaling. Through activation of the canonical pathway TGF-β acts directly on NBCe1 by binding of Smad4 to the NBCe1 promoter and regulating its transcription, followed by increased protein expression and transport activity.
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Affiliation(s)
- Shokoufeh Khakipoor
- Department of Molecular EmbryologyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
| | - Christian Ophoven
- Department of Molecular EmbryologyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
| | - Magdalena Schrödl‐Häußel
- Department of Molecular EmbryologyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
| | - Melanie Feuerstein
- Department of Molecular EmbryologyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
| | - Bernd Heimrich
- Department of NeuroanatomyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
| | - Joachim W. Deitmer
- Department of General ZoologyFB Biology, University of KaiserslauternP.B. 3049D‐67653KaiserslauternGermany
| | - Eleni Roussa
- Department of Molecular EmbryologyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
- Department of NeuroanatomyInstitute for Anatomy and Cell Biology, Faculty of Medicine, University of FreiburgAlbertstrasse 17D‐79104FreiburgGermany
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13
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Forero-Quintero LS, Deitmer JW, Becker HM. Reduction of epileptiform activity in ketogenic mice: The role of monocarboxylate transporters. Sci Rep 2017; 7:4900. [PMID: 28687765 PMCID: PMC5501801 DOI: 10.1038/s41598-017-05054-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 05/23/2017] [Indexed: 02/05/2023] Open
Abstract
Epilepsy is a chronic neurological disorder that affects approximately 50 million people worldwide. Ketogenic diet (KD) can be a very effective treatment for intractable epilepsy. Potential mechanisms of action for KD have been proposed, including the re-balance among excitatory and inhibitory neurotransmission and decrease in the glycolytic rate in brain cells. KD has been shown to have an effect on the expression pattern of monocarboxylate transporters (MCT), however, it is unknown whether MCT transport activity is affected by KD and linked to the reduction of seizures during KD. Therefore, we studied the influence of KD on MCT transport activity and the role of MCTs during epileptiform activity. Our results showed a decrease in the epileptiform activity in cortical slices from mice fed on KD and in the presence of beta-hydroxybutyrate. KD increased transport capacity for ketone bodies and lactate in cortical astrocytes by raising the MCT1 expression level. Inhibition of MCT1 and MCT2 in control conditions decreases epileptiform activity, while in KD it induced an increase in epileptiform activity. Our results suggest that MCTs not only play an important role in the transport of ketone bodies, but also in the modulation of brain energy metabolism under normal and ketogenic conditions.
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Affiliation(s)
- Linda S Forero-Quintero
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany
| | - Holger M Becker
- Division of General Zoology, Department of Biology, University of Kaiserslautern, P.O. Box 3049, D-67653, Kaiserslautern, Germany.
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14
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Theparambil SM, Naoshin Z, Defren S, Schmaelzle J, Weber T, Schneider HP, Deitmer JW. Bicarbonate sensing in mouse cortical astrocytes during extracellular acid/base disturbances. J Physiol 2017; 595:2569-2585. [PMID: 27981578 DOI: 10.1113/jp273394] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 11/30/2016] [Indexed: 12/18/2022] Open
Abstract
KEY POINTS The present study suggests that the electrogenic sodium-bicarbonate cotransporter, NBCe1, supported by carbonic anhydrase II, CAII, provides an efficient mechanism of bicarbonate sensing in cortical astrocytes. This mechanism is proposed to play a major role in setting the pHi responses to extracellular acid/base challenges in astrocytes. A decrease in extracellular [HCO3- ] during isocapnic acidosis and isohydric hypocapnia, or an increase in intracellular [HCO3- ] during hypercapnic acidosis, was effectively sensed by NBCe1, which carried bicarbonate out of the cells under these conditions, and caused an acidification and sodium fall in WT astrocytes, but not in NBCe1-knockout astrocytes. Isocapnic acidosis, hypercapnic acidosis and isohydric hypocapnia evoked inward currents in NBCe1- and CAII-expressing Xenopus laevis oocytes, but not in native oocytes, suggesting that NBCe1 operates in the outwardly directed mode under these conditions consistent with our findings in astrocytes. We propose that bicarbonate sensing of astrocytes may have functional significance during extracellular acid/base disturbances in the brain, as it not only alters intracellular pH/[HCO3- ]-dependent functions of astrocytes, but also modulates the extracellular pH/[HCO3- ] in brain tissue. ABSTRACT Extracellular acid/base status of the mammalian brain undergoes dynamic changes during many physiological and pathological events. Although intracellular pH (pHi ) of astrocytes responds to extracellular acid/base changes, the mechanisms mediating these changes have remained unresolved. We have previously shown that the electrogenic sodium-bicarbonate cotransporter, NBCe1, is a high-affinity bicarbonate carrier in cortical astrocytes. In the present study, we investigated whether NBCe1 plays a role in bicarbonate sensing in astrocytes, and in determining the pHi responses to extracellular acid/base challenges. We measured changes in intracellular H+ and Na+ in astrocytes from wild-type (WT) and from NBCe1-knockout (KO) mice, using ion-selective dyes, during isocapnic acidosis, hypercapnic acidosis and hypocapnia. We also analysed NBCe1-mediated membrane currents in Xenopus laevis oocytes under similar conditions. Comparing WT and NBCe1-KO astrocytes, we could dissect the contribution of NBCe1, of diffusion of CO2 across the cell membrane and, after blocking carbonic anhydrase (CA) activity with ethoxyzolamide, of the role of CA, for the amplitude and rate of acid/base fluxes. Our results suggest that NBCe1 transport activity in astrocytes, supported by CA activity, renders astrocytes bicarbonate sensors in the mouse cortex. NBCe1 carried bicarbonate into and out of the cell by sensing the variations of transmembrane [HCO3- ], irrespective of the changes in intra- and extracellular pH, and played a major role in setting pHi responses to the extracellular acid/base challenges. We propose that bicarbonate sensing of astrocytes may have potential functional significance during extracellular acid/base alterations in the brain.
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Affiliation(s)
- Shefeeq M Theparambil
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Zinnia Naoshin
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Sabrina Defren
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Jana Schmaelzle
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Tobias Weber
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Hans-Peter Schneider
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Pb 3049, D-67653, Kaiserslautern, Germany
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15
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Noor SI, Pouyssegur J, Deitmer JW, Becker HM. Integration of a 'proton antenna' facilitates transport activity of the monocarboxylate transporter MCT4. FEBS J 2016; 284:149-162. [PMID: 27860283 DOI: 10.1111/febs.13964] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 09/20/2016] [Accepted: 11/11/2016] [Indexed: 12/22/2022]
Abstract
Monocarboxylate transporters (MCTs) mediate the proton-coupled transport of high-energy metabolites like lactate and pyruvate and are expressed in nearly every mammalian tissue. We have shown previously that transport activity of MCT4 is enhanced by carbonic anhydrase II (CAII), which has been suggested to function as a 'proton antenna' for the transporter. In the present study, we tested whether creation of an endogenous proton antenna by introduction of a cluster of histidine residues into the C-terminal tail of MCT4 (MCT4-6xHis) could facilitate MCT4 transport activity when heterologously expressed in Xenopus oocytes. Our results show that integration of six histidines into the C-terminal tail does indeed increase transport activity of MCT4 to the same extent as did coexpression of MCT4-WT with CAII. Transport activity of MCT4-6xHis could be further enhanced by coexpression with extracellular CAIV, but not with intracellular CAII. Injection of an antibody against the histidine cluster into MCT4-expressing oocytes decreased transport activity of MCT4-6xHis, while leaving activity of MCT4-WT unaltered. Taken together, these findings suggest that transport activity of the proton-coupled monocarboxylate transporter MCT4 can be facilitated by integration of an endogenous proton antenna into the transporter's C-terminal tail.
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Affiliation(s)
- Sina Ibne Noor
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Germany
| | - Jacques Pouyssegur
- Centre Scientifique de Monaco (CSM), Monaco.,Institute for Research on Cancer & Aging (IRCAN), INSERM, Centre A. Lacassagne, CNRS, University of Nice-Sophia Antipolis, France
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Germany
| | - Holger M Becker
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Germany
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16
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Valdebenito R, Ruminot I, Garrido-Gerter P, Fernández-Moncada I, Forero-Quintero L, Alegría K, Becker HM, Deitmer JW, Barros LF. Targeting of astrocytic glucose metabolism by beta-hydroxybutyrate. J Cereb Blood Flow Metab 2016; 36:1813-1822. [PMID: 26661221 PMCID: PMC5076786 DOI: 10.1177/0271678x15613955] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 07/14/2015] [Indexed: 11/17/2022]
Abstract
The effectiveness of ketogenic diets and intermittent fasting against neurological disorders has brought interest to the effects of ketone bodies on brain cells. These compounds are known to modify the metabolism of neurons, but little is known about their effect on astrocytes, cells that control the supply of glucose to neurons and also modulate neuronal excitability through the glycolytic production of lactate. Here we have used genetically-encoded Förster Resonance Energy Transfer nanosensors for glucose, pyruvate and ATP to characterize astrocytic energy metabolism at cellular resolution. Our results show that the ketone body beta-hydroxybutyrate strongly inhibited astrocytic glucose consumption in mouse astrocytes in mixed cultures, in organotypic hippocampal slices and in acute hippocampal slices prepared from ketotic mice, while blunting the stimulation of glycolysis by physiological and pathophysiological stimuli. The inhibition of glycolysis was paralleled by an increased ability of astrocytic mitochondria to metabolize pyruvate. These results support the emerging notion that astrocytes contribute to the neuroprotective effect of ketone bodies.
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Affiliation(s)
| | - Iván Ruminot
- General Zoology/University of Kaiserslautern, Kaiserslautern, Germany
| | - Pamela Garrido-Gerter
- Centro de Estudios Científicos, Valdivia, Chile Universidad Austral de Chile, Valdivia, Chile
| | | | | | | | - Holger M Becker
- General Zoology/University of Kaiserslautern, Kaiserslautern, Germany
| | - Joachim W Deitmer
- General Zoology/University of Kaiserslautern, Kaiserslautern, Germany
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17
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Theparambil SM, Weber T, Schmälzle J, Ruminot I, Deitmer JW. Proton Fall or Bicarbonate Rise: GLYCOLYTIC RATE IN MOUSE ASTROCYTES IS PAVED BY INTRACELLULAR ALKALINIZATION. J Biol Chem 2016; 291:19108-17. [PMID: 27422823 PMCID: PMC5009280 DOI: 10.1074/jbc.m116.730143] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/12/2016] [Indexed: 01/08/2023] Open
Abstract
Glycolysis is the primary step for major energy production in the cell. There is strong evidence suggesting that glucose consumption and rate of glycolysis are highly modulated by cytosolic pH/[H(+)], but those can also be stimulated by an increase in the intracellular [HCO3 (-)]. Because proton and bicarbonate shift concomitantly, it remained unclear whether enhanced glucose consumption and glycolytic rate were mediated by the changes in intracellular [H(+)] or [HCO3 (-)]. We have asked whether glucose metabolism is enhanced by either a fall in intracellular [H(+)] or a rise in intracellular [HCO3 (-)], or by both, in mammalian astrocytes. We have recorded intracellular glucose in mouse astrocytes using a FRET-based nanosensor, while imposing different intracellular [H(+)] and [CO2]/[HCO3 (-)]. Glucose consumption and glycolytic rate were augmented by a fall in intracellular [H(+)], irrespective of a concomitant rise or fall in intracellular [HCO3 (-)]. Transport of HCO3 (-) into and out of astrocytes by the electrogenic sodium bicarbonate cotransporter (NBCe1) played a crucial role in causing changes in intracellular pH and [HCO3 (-)], but was not obligatory for the pH-dependent changes in glucose metabolism. Our results clearly show that it is the cytosolic pH that modulates glucose metabolism in cortical astrocytes, and possibly also in other cell types.
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Affiliation(s)
- Shefeeq M Theparambil
- From the Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserlautern, P. B. 3049, D-67653 Kaiserslautern, Germany and
| | - Tobias Weber
- From the Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserlautern, P. B. 3049, D-67653 Kaiserslautern, Germany and
| | - Jana Schmälzle
- From the Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserlautern, P. B. 3049, D-67653 Kaiserslautern, Germany and
| | - Ivàn Ruminot
- From the Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserlautern, P. B. 3049, D-67653 Kaiserslautern, Germany and the Centro de Estudios Científicos (CECs), Valdivia 5110466, Chile
| | - Joachim W Deitmer
- From the Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserlautern, P. B. 3049, D-67653 Kaiserslautern, Germany and
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18
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Loganathan SK, Schneider HP, Morgan PE, Deitmer JW, Casey JR. Functional assessment of SLC4A11, an integral membrane protein mutated in corneal dystrophies. Am J Physiol Cell Physiol 2016; 311:C735-C748. [PMID: 27558157 DOI: 10.1152/ajpcell.00078.2016] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 08/17/2016] [Indexed: 12/19/2022]
Abstract
SLC4A11, a member of the SLC4 family of bicarbonate transporters, is a widely expressed integral membrane protein, abundant in kidney and cornea. Mutations of SLC4A11 cause some cases of the blinding corneal dystrophies, congenital hereditary endothelial dystrophy, and Fuchs endothelial corneal dystrophy. These diseases are marked by fluid accumulation in the corneal stroma, secondary to defective fluid reabsorption by the corneal endothelium. The role of SLC4A11 in these corneal dystrophies is not firmly established, as SLC4A11 function remains unclear. To clarify the normal function(s) of SLC4A11, we characterized the protein following expression in the simple, low-background expression system Xenopus laevis oocytes. Since plant and fungal SLC4A11 orthologs transport borate, we measured cell swelling associated with accumulation of solute borate. The plant water/borate transporter NIP5;1 manifested borate transport, whereas human SLC4A11 did not. SLC4A11 supported osmotically driven water accumulation that was electroneutral and Na+ independent. Studies in oocytes and HEK293 cells could not detect Na+-coupled HCO3- transport or Cl-/HCO3- exchange by SLC4A11. SLC4A11 mediated electroneutral NH3 transport in oocytes. Voltage-dependent OH- or H+ movement was not measurable in SLC4A11-expressing oocytes, but SLC4A11-expressing HEK293 cells manifested low-level cytosolic acidification at baseline. In mammalian cells, but not oocytes, OH-/H+ conductance may arise when SLC4A11 activates another protein or itself is activated by another protein. These data argue against a role of human SLC4A11 in bicarbonate or borate transport. This work provides additional support for water and ammonia transport by SLC4A11. When expressed in oocytes, SLC4A11 transported NH3, not NH3/H.
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Affiliation(s)
- Sampath K Loganathan
- Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Hans-Peter Schneider
- Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Technische Universtät Kaiserslautern, Kaiserslautern, Germany; and
| | - Patricio E Morgan
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Technische Universtät Kaiserslautern, Kaiserslautern, Germany; and
| | - Joseph R Casey
- Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada;
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19
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Kazokaitė J, Ames S, Becker HM, Deitmer JW, Matulis D. Selective inhibition of human carbonic anhydrase IX in Xenopus oocytes and MDA-MB-231 breast cancer cells. J Enzyme Inhib Med Chem 2016; 31:38-44. [PMID: 27557419 DOI: 10.1080/14756366.2016.1217854] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Human carbonic anhydrase IX (CA IX) is overexpressed in the most aggressive and invasive tumors. Therefore, CA IX has become the promising antitumor drug target. Three inhibitors have been shown to selectively and with picomolar affinity inhibit human recombinant CA IX. Their inhibitory potencies were determined for the CA IX, CA II, CA IV and CA XII in Xenopus oocytes and MDA-MB-231 cancer cells. The inhibition IC50 value of microelectrode-monitored intracellular and extracellular acidification reached 15 nM for CA IX, but with no effect on CA II expressed in Xenopus oocytes. Results were confirmed by mass spectrometric gas analysis of lysed oocytes, when an inhibitory effect on CA IX catalytic activity was found after the injection of 1 nM VD11-4-2. Moreover, VD11-4-2 inhibited CA activity in MDA-MB-231 cancer cells at nanomolar concentrations. This combination of high selectivity and potency renders VD11-4-2, an auspicious therapeutic drug for target-specific tumor therapy.
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Affiliation(s)
- Justina Kazokaitė
- a Department of Biothermodynamics and Drug Design , Institute of Biotechnology, Vilnius University , Vilnius , Lithuania and
| | - Samantha Ames
- b Division of General Zoology , FB Biologie, TU Kaiserslautern , Kaiserslautern , Germany
| | - Holger M Becker
- b Division of General Zoology , FB Biologie, TU Kaiserslautern , Kaiserslautern , Germany
| | - Joachim W Deitmer
- b Division of General Zoology , FB Biologie, TU Kaiserslautern , Kaiserslautern , Germany
| | - Daumantas Matulis
- a Department of Biothermodynamics and Drug Design , Institute of Biotechnology, Vilnius University , Vilnius , Lithuania and
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Abstract
Ammonia is a biologically potent molecule, and the regulation of ammonia levels in the mammalian body is, therefore, strictly controlled. The molecular paths of ammonia permeation across plasma membranes remain ill-defined, but the structural similarity of water and NH3 has pointed to the aquaporins as putative NH3-permeable pores. Accordingly, a range of aquaporins from mammals, plants, fungi, and protozoans demonstrates ammonia permeability. Aquaporin 4 (AQP4) is highly expressed at perivascular glia end-feet in the mammalian brain and may, with this prominent localization at the blood-brain-interface, participate in the exchange of ammonia, which is required to sustain the glutamate-glutamine cycle. Here we observe that AQP4-expressing Xenopus oocytes display a reflection coefficient <1 for NH4Cl at pH 8.0, at which pH an increased amount of the ammonia occurs in the form of NH3 Taken together with an NH4Cl-mediated intracellular alkalization (or lesser acidification) of AQP4-expressing oocytes, these data suggest that NH3 is able to permeate the pore of AQP4. Exposure to NH4Cl increased the membrane currents to a similar extent in uninjected oocytes and in oocytes expressing AQP4, indicating that the ionic NH4 (+) did not permeate AQP4. Molecular dynamics simulations revealed partial pore permeation events of NH3 but not of NH4 (+) and a reduced energy barrier for NH3 permeation through AQP4 compared with that of a cholesterol-containing lipid bilayer, suggesting AQP4 as a favored transmembrane route for NH3 Our data propose that AQP4 belongs to the growing list of NH3-permeable water channels.
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Affiliation(s)
- Mette Assentoft
- From the Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Shreyas Kaptan
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Gottingen, Germany, and
| | - Hans-Peter Schneider
- Division of General Zoology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Bert L de Groot
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Gottingen, Germany, and
| | - Nanna MacAulay
- From the Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark,
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21
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Rudolph R, Jahn HM, Courjaret R, Messemer N, Kirchhoff F, Deitmer JW. The inhibitory input to mouse cerebellar Purkinje cells is reciprocally modulated by Bergmann glial P2Y1 and AMPA receptor signaling. Glia 2016; 64:1265-80. [PMID: 27144942 DOI: 10.1002/glia.22999] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/06/2016] [Accepted: 04/13/2016] [Indexed: 11/10/2022]
Abstract
Synaptic transmission has been shown to be modulated by glial functions, but the modes of specific glial action may vary in different neural circuits. We have tested the hypothesis, if Bergmann GLIA (BG) are involved in shaping neuronal communication in the mouse cerebellar cortex, using acutely isolated cerebellar slices of wild-type (WT) and of glia-specific receptor knockout mice. Activation of P2Y1 receptors by ADP (100 µM) or glutamatergic receptors by AMPA (0.3 µM) resulted in a robust, reversible and repeatable rise of evoked inhibitory input in Purkinje cells by 80% and 150%, respectively. The ADP-induced response was suppressed by prior application of AMPA, and the AMPA-induced response was suppressed by prior application of ADP. Genetic deletion or pharmacological blockade of either receptor restored the response to the other receptor agonist. Both ADP and AMPA responses were sensitive to Rose Bengal, which blocks vesicular glutamate uptake, and to the NMDA receptor antagonist D-AP5. Our results provide strong evidence that activation of both ADP and AMPA receptors, located on BGs, results in the release of glutamate, which in turn activates inhibitory interneurons via NMDA-type glutamate receptors. This infers that BG cells, by means of metabotropic signaling via their AMPA and P2Y1 receptors, which mutually suppress each other, would interdependently contribute to the fine-tuning of Purkinje cell activity in the cerebellar cortex. GLIA 2016. GLIA 2016;64:1265-1280.
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Affiliation(s)
- Ramona Rudolph
- General Zoology, FB Biology, University of Kaiserslautern, P.B. 3049, D-67653, Kaiserslautern, Germany
| | - Hannah M Jahn
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, D-66421 Homburg/Saar, Germany
| | - Raphael Courjaret
- General Zoology, FB Biology, University of Kaiserslautern, P.B. 3049, D-67653, Kaiserslautern, Germany.,Weill Cornell Medical College, Doha, Qatar
| | - Nanette Messemer
- General Zoology, FB Biology, University of Kaiserslautern, P.B. 3049, D-67653, Kaiserslautern, Germany
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine, University of Saarland, D-66421 Homburg/Saar, Germany
| | - Joachim W Deitmer
- General Zoology, FB Biology, University of Kaiserslautern, P.B. 3049, D-67653, Kaiserslautern, Germany
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Klier M, Jamali S, Ames S, Schneider HP, Becker HM, Deitmer JW. Catalytic activity of human carbonic anhydrase isoform IX is displayed both extra- and intracellularly. FEBS J 2015; 283:191-200. [PMID: 26470855 DOI: 10.1111/febs.13562] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 09/30/2015] [Accepted: 10/13/2015] [Indexed: 11/30/2022]
Abstract
Most carbonic anhydrases catalyse the reversible conversion of carbon dioxide to protons and bicarbonate, either as soluble cytosolic enzymes, in or at intracellular organelles, or at the extracellular face of the cell membrane as membrane-anchored proteins. Carbonic anhydrase isoform IX (CA IX), a membrane-bound enzyme with catalytic activity at the extracellular membrane surface, has come to prominence in recent years because of its association with hypoxic tissue, particularly tumours, often indicating poor prognosis. We have evaluated the catalytic activity of CA IX heterologously expressed in Xenopus laevis oocytes by measuring the amplitude and rate of cytosolic pH changes as well as pH changes at the outer membrane surface (pHs ) during addition and removal of 5% CO2 /25 mm HCO3-, and by mass spectrometry. Our results indicate both extracellular and intracellular catalytic activity of CA IX. Reduced rates of CO2 -dependent intracellular pH changes after knockdown of CA IX confirmed these findings in two breast cancer cell lines: MCF-7 and MDA-MB-231. Our results demonstrate a new function of CA IX that may be important in the search for therapeutic cancer drugs targeting CA IX.
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Affiliation(s)
- Michael Klier
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Somayeh Jamali
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Samantha Ames
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Hans-Peter Schneider
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Holger M Becker
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
| | - Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Germany
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Stavermann M, Meuth P, Doengi M, Thyssen A, Deitmer JW, Lohr C. Calcium-induced calcium release and gap junctions mediate large-scale calcium waves in olfactory ensheathing cells in situ. Cell Calcium 2015; 58:215-25. [DOI: 10.1016/j.ceca.2015.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 05/04/2015] [Accepted: 05/26/2015] [Indexed: 02/06/2023]
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Theparambil SM, Naoshin Z, Thyssen A, Deitmer JW. Reversed electrogenic sodium bicarbonate cotransporter 1 is the major acid loader during recovery from cytosolic alkalosis in mouse cortical astrocytes. J Physiol 2015; 593:3533-47. [PMID: 25990710 DOI: 10.1113/jp270086] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 05/17/2015] [Indexed: 12/29/2022] Open
Abstract
KEY POINTS The regulation of H(+) i from cytosolic alkalosis has generally been attributed to the activity of Cl(-) -coupled acid loaders/base extruders in most cell types, including brain cells. The present study demonstrates that outwardly-directed sodium bicarbonate cotransport via electrogenic sodium bicarbonate cotransporter 1 (NBCe1) mediates the major fraction of H(+) i regulation from cytosolic alkalosis in mouse cortical astrocytes. Cl(-) -coupled acid-loading transporters play only a minor role in the regulation of H(+) i from alkalosis in mouse cortical astrocytes. NBCe1-mediated H(+) i regulation from alkalosis was dominant, with the support of intracellular carbonic anhydrase II, even when the intra- and extracellular [HCO3 (-) ] was very low (<1mM), as in nominally CO2 /HCO3 (-) free condition. A reversed NBCe1 in astrocytes may also be significant for stabilizing extracellular pH in brain tissue. ABSTRACT Recovery of intracellular pH from cytosolic alkalosis has been attributed primarily to Cl(-) coupled acid loaders/base extruders such as Cl(-) /HCO3 (-) or Cl(-) /OH(-) exchangers. We have studied this process in cortical astrocytes from wild-type and transgenic mouse models with gene deletion for the electrogenic sodium bicarbonate cotransporter 1 (NBCe1) and for carbonic anhydrase (CA) isoform II. An acute cytosolic alkalosis was induced by the removal of either CO2 /HCO3 (-) or butyric acid, and the subsequent acid loading was analysed by monitoring changes in cytosolic H(+) or Na(+) using ion-sensitive fluorescent dyes. We have identified that NBCe1 reverses during alkalosis and contributes more than 70% to the rate of recovery from alkalosis by extruding Na(+) and HCO3 (-) . After CA inhibition or in CAII-knockout (KO) cells, the rate of recovery was reduced by 40%, and even by 70% in the nominal absence of CO2 /HCO3 (-) . Increasing the extracellular K(+) concentration modulated the rate of acid loading in wild-type cells, but not in NBCe1-KO cells. Removing chloride had only a minor effect on the recovery from alkalosis. Reversal of NBCe1 by reducing pH/[HCO3 (-) ] was demonstrated in astrocytes and in Xenopus oocytes, in which human NBCe1 was heterologously expressed. The results obtained suggest that reversed NBCe1, supported by CAII activity, plays a major role in acid-loading cortical astrocytes to support recovery from cytosolic alkalosis.
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Affiliation(s)
- Shefeeq M Theparambil
- Department of General Zoology, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Zinnia Naoshin
- Department of General Zoology, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Anne Thyssen
- Department of General Zoology, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Joachim W Deitmer
- Department of General Zoology, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany
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Heidtmann H, Ruminot I, Becker HM, Deitmer JW. Inhibition of monocarboxylate transporter by N-cyanosulphonamide S0859. Eur J Pharmacol 2015; 762:344-9. [PMID: 26027796 DOI: 10.1016/j.ejphar.2015.05.049] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/19/2015] [Accepted: 05/26/2015] [Indexed: 12/31/2022]
Abstract
The synthetic compound N-cyanosulphonamide S0859 has been described as a selective inhibitor of sodium-bicarbonate cotransporters (NBC, SLC4) in mammalian heart (Ch'en et al., 2008). First, for comparison, the electrogenic human NBCe1 (SLC4A4) was heterologously expressed in Xenopus laevis oocytes, where its transport activity was inhibited by S0859 with an IC50 of 9µM. The activity of monocarboxylate transporter (MCT) isoforms 1, 2, and 4 (SLC16A1, SLC16A7, SLC16A3), which transport lactate, pyruvate and ketone bodies, were also heterologously expressed in Xenopus oocytes, and their transport activity was similarly and reversibly inhibited by S0859 with an IC50 of 4-10µM. Partial inhibition of lactate transport by S0859 (50µM) was also obtained in cultured astrocytes of mice. Thus, S0859 appears to be an inhibitor of anion transport with a broader spectrum than previously thought, and may also interfere with cellular metabolite uptake/release.
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Affiliation(s)
- Hella Heidtmann
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, P.B. 3049, D-67653 Kaiserslautern, Germany
| | - Iván Ruminot
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, P.B. 3049, D-67653 Kaiserslautern, Germany
| | - Holger M Becker
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, P.B. 3049, D-67653 Kaiserslautern, Germany
| | - Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, P.B. 3049, D-67653 Kaiserslautern, Germany.
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26
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Theparambil SM, Deitmer JW. High effective cytosolic H+ buffering in mouse cortical astrocytes attributable to fast bicarbonate transport. Glia 2015; 63:1581-94. [PMID: 25820238 DOI: 10.1002/glia.22829] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 03/03/2015] [Accepted: 03/13/2015] [Indexed: 11/09/2022]
Abstract
Cytosolic H(+) buffering plays a major role for shaping intracellular H(+) shifts and hence for the availability of H(+) for biochemical reactions and acid/base-coupled transport processes. H(+) buffering is one of the prime means to protect the cell from large acid/base shifts. We have used the H(+) indicator dye BCECF and confocal microscopy to monitor the cytosolic H(+) concentration, [H(+)]i, in cultured cortical astrocytes of wild-type mice and of mice deficient in sodium/bicarbonate cotransporter NBCe1 (NBCe1-KO) or in carbonic anhydrase isoform II (CAII-KO). The steady-state buffer strength was calculated from the amplitude of [H(+)]i transients as evoked by CO2/HCO3(-) and by butyric acid in the presence and absence of CO2/HCO3(-). We tested the hypotheses if, in addition to instantaneous physicochemical H(+) buffering, rapid acid/base transport across the cell membrane contributes to the total, "effective" cytosolic H(+) buffering. In the presence of 5% CO2/26 mM HCO3(-), H(+) buffer strength in astrocytes was increased 4-6 fold, as compared with that in non-bicarbonate, HEPES-buffered solution, which was largely attributable to fast HCO3 (-) transport into the cells via NBCe1, supported by CAII activity. Our results show that within the time frame of determining physiological H(+) buffering in cells, fast transport and equilibration of CO2/H(+)/HCO3(-) can make a major contribution to the total "effective" H(+) buffer strength. Thus, "effective" cellular H(+) buffering is, to a large extent, attributable to membrane transport of base equivalents rather than a purely passive physicochemical process, and can be much larger than reported so far. Not only physicochemical H(+) buffering, but also rapid import of HCO3(-) via the electrogenic sodium-bicarbonate cotransporter NBCe1, supported by carbonic anhydrase II (CA II), was identified to enhance cytosolic H(+) buffer strength substantially.
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Affiliation(s)
- Shefeeq M Theparambil
- Abteilung Für Allgemeine Zoologie, Fachbereich Biologie, University of Kaiserslautern, Kaiserslautern, D-67653, Germany
| | - Joachim W Deitmer
- Abteilung Für Allgemeine Zoologie, Fachbereich Biologie, University of Kaiserslautern, Kaiserslautern, D-67653, Germany
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27
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Schrödl-Häußel M, Theparambil SM, Deitmer JW, Roussa E. Regulation of functional expression of the electrogenic sodium bicarbonate cotransporter 1, NBCe1 (SLC4A4), in mouse astrocytes. Glia 2015; 63:1226-39. [DOI: 10.1002/glia.22814] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 02/17/2015] [Accepted: 02/18/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Magdalena Schrödl-Häußel
- Department of Molecular Embryology; Institute for Anatomy and Cell Biology, University of Freiburg; Freiburg Germany
| | - Shefeeq M. Theparambil
- Department of General Zoology; FB Biology, University of Kaiserslautern; Kaiserslautern Germany
| | - Joachim W. Deitmer
- Department of General Zoology; FB Biology, University of Kaiserslautern; Kaiserslautern Germany
| | - Eleni Roussa
- Department of Molecular Embryology; Institute for Anatomy and Cell Biology, University of Freiburg; Freiburg Germany
- Department of Neuroanatomy; University of Freiburg; Freiburg Germany
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28
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Noor SI, Dietz S, Heidtmann H, Boone CD, McKenna R, Deitmer JW, Becker HM. Analysis of the binding moiety mediating the interaction between monocarboxylate transporters and carbonic anhydrase II. J Biol Chem 2015; 290:4476-86. [PMID: 25561737 DOI: 10.1074/jbc.m114.624577] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proton-coupled monocarboxylate transporters (MCTs) mediate the exchange of high energy metabolites like lactate between different cells and tissues. We have reported previously that carbonic anhydrase II augments transport activity of MCT1 and MCT4 by a noncatalytic mechanism, while leaving transport activity of MCT2 unaltered. In the present study, we combined electrophysiological measurements in Xenopus oocytes and pulldown experiments to analyze the direct interaction between carbonic anhydrase II (CAII) and MCT1, MCT2, and MCT4, respectively. Transport activity of MCT2-WT, which lacks a putative CAII-binding site, is not augmented by CAII. However, introduction of a CAII-binding site into the C terminus of MCT2 resulted in CAII-mediated facilitation of MCT2 transport activity. Interestingly, introduction of three glutamic acid residues alone was not sufficient to establish a direct interaction between MCT2 and CAII, but the cluster had to be arranged in a fashion that allowed access to the binding moiety in CAII. We further demonstrate that functional interaction between MCT4 and CAII requires direct binding of the enzyme to the acidic cluster (431)EEE in the C terminus of MCT4 in a similar fashion as previously shown for binding of CAII to the cluster (489)EEE in the C terminus of MCT1. In CAII, binding to MCT1 and MCT4 is mediated by a histidine residue at position 64. Taken together, our results suggest that facilitation of MCT transport activity by CAII requires direct binding between histidine 64 in CAII and a cluster of glutamic acid residues in the C terminus of the transporter that has to be positioned in surroundings that allow access to CAII.
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Affiliation(s)
- Sina Ibne Noor
- From the Department of Biology, Division of Zoology/Membrane Transport and
| | - Steffen Dietz
- From the Department of Biology, Division of Zoology/Membrane Transport and
| | - Hella Heidtmann
- From the Department of Biology, Division of Zoology/Membrane Transport and the Department of Biology, Division of General Zoology, University of Kaiserslautern, D-67653 Kaiserslautern, Germany and
| | - Christopher D Boone
- the Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
| | - Robert McKenna
- the Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610
| | - Joachim W Deitmer
- the Department of Biology, Division of General Zoology, University of Kaiserslautern, D-67653 Kaiserslautern, Germany and
| | - Holger M Becker
- From the Department of Biology, Division of Zoology/Membrane Transport and
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29
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Deitmer JW, Theparambil SM, Ruminot I, Becker HM. The role of membrane acid/base transporters and carbonic anhydrases for cellular pH and metabolic processes. Front Neurosci 2015; 8:430. [PMID: 25601823 PMCID: PMC4283522 DOI: 10.3389/fnins.2014.00430] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 12/09/2014] [Indexed: 11/17/2022] Open
Affiliation(s)
- Joachim W Deitmer
- General Zoology, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
| | | | - Iván Ruminot
- General Zoology, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
| | - Holger M Becker
- Zoology/Membrane Transport, FB Biology, University of Kaiserslautern Kaiserslautern, Germany
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30
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Klier M, Andes FT, Deitmer JW, Becker HM. Intracellular and extracellular carbonic anhydrases cooperate non-enzymatically to enhance activity of monocarboxylate transporters. J Biol Chem 2013; 289:2765-75. [PMID: 24338019 DOI: 10.1074/jbc.m113.537043] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Proton-coupled monocarboxylate transporters (MCTs) are carriers of high-energy metabolites such as lactate, pyruvate, and ketone bodies and are expressed in most tissues. It has previously been shown that transport activity of MCT1 and MCT4 is enhanced by the cytosolic carbonic anhydrase II (CAII) independent of its catalytic activity. We have now studied the influence of the extracellular, membrane-bound CAIV on transport activity of MCT1/4, heterologously expressed in Xenopus oocytes. Coexpression of CAIV with MCT1 and MCT4 resulted in a significant increase in MCT transport activity, even in the nominal absence of CO2/HCO3(-). CAIV-mediated augmentation of MCT activity was independent of the CAIV catalytic function, since application of the CA-inhibitor ethoxyzolamide or coexpression of the catalytically inactive mutant CAIV-V165Y did not suppress CAIV-mediated augmentation of MCT transport activity. The interaction required CAIV at the extracellular surface, since injection of CAIV protein into the oocyte cytosol did not augment MCT transport function. The effects of cytosolic CAII (injected as protein) and extracellular CAIV (expressed) on MCT transport activity, were additive. Our results suggest that intra- and extracellular carbonic anhydrases can work in concert to ensure rapid shuttling of metabolites across the cell membrane.
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Affiliation(s)
- Michael Klier
- From the Division of General Zoology, Department of Biology, University of Kaiserslautern D-67653 Kaiserslautern, Germany and
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31
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Affiliation(s)
- Joachim W Deitmer
- General Zoology, University of Kaiserslautern Kaiserslautern, Germany
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32
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Bonar P, Schneider HP, Becker HM, Deitmer JW, Casey JR. Three-dimensional model for the human Cl-/HCO3- exchanger, AE1, by homology to the E. coli ClC protein. J Mol Biol 2013; 425:2591-608. [PMID: 23583773 DOI: 10.1016/j.jmb.2013.04.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 03/20/2013] [Accepted: 04/03/2013] [Indexed: 01/19/2023]
Abstract
AE1 mediates electroneutral 1:1 exchange of bicarbonate for chloride across the plasma membrane of erythrocytes and type A cells of the renal collecting duct. No high-resolution structure is available for the AE1 membrane domain, which alone is required for its transport activity. A recent electron microscopy structure of the AE1 membrane domain was proposed to have a similar protein fold to ClC chloride channels. We developed a three-dimensional homology model of the AE1 membrane domain, using the Escherichia coli ClC channel structure as a template. This model agrees well with a long list of biochemically established spatial constraints for AE1. To investigate the AE1 transport mechanism, we created point mutations in regions corresponding to E. coli ClC transport mechanism residues. When expressed in HEK293 cells, several mutants had Cl(-)/HCO3(-) exchange rates significantly different from that of wild-type AE1. When further assessed in Xenopus laevis oocytes, there were significant changes in the transport activity of several AE1 point mutants as assessed by changes in pH. None of the mutants, however, added an electrogenic component to AE1 transport activity. This indicates that the AE1 point mutants altered the transport activity of AE1, without changing its electrogenicity and stoichiometry. The homology model successfully identified residues in AE1 that are critical to AE1 transport activity. Thus, we conclude that AE1 has a similar protein fold to ClC chloride channels.
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Affiliation(s)
- Pamela Bonar
- Membrane Protein Disease Research Group, Department of Biochemistry, University of Alberta, Edmonton, Canada T6G 2H7
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33
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Thyssen A, Stavermann M, Buddrus K, Doengi M, Ekberg JA, St John JA, Deitmer JW, Lohr C. Spatial and developmental heterogeneity of calcium signaling in olfactory ensheathing cells. Glia 2012; 61:327-37. [PMID: 23109369 DOI: 10.1002/glia.22434] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 09/11/2012] [Indexed: 12/24/2022]
Abstract
Olfactory ensheathing cells (OECs) are specialized glial cells in the mammalian olfactory system supporting growth of axons from the olfactory epithelium into the olfactory bulb. OECs in the olfactory bulb can be subdivided into OECs of the outer nerve layer and the inner nerve layer according to the expression of marker proteins and their location in the nerve layer. In the present study, we have used confocal calcium imaging of OECs in acute mouse brain slices and olfactory bulbs in toto to investigate physiological differences between OEC subpopulations. OECs in the outer nerve layer, but not the inner nerve layer, responded to glutamate, ATP, serotonin, dopamine, carbachol, and phenylephrine with increases in the cytosolic calcium concentration. The calcium responses consisted of a transient and a tonic component, the latter being mediated by store-operated calcium entry. Calcium measurements in OECs during the first three postnatal weeks revealed a downregulation of mGluR(1) and P2Y(1) receptor-mediated calcium signaling within the first 2 weeks, suggesting that the expression of these receptors is developmentally controlled. In addition, electrical stimulation of sensory axons evoked calcium signaling via mGluR(1) and P2Y(1) only in outer nerve layer OECs. Downregulation of the receptor-mediated calcium responses in postnatal animals is reflected by a decrease in amplitude of stimulation-evoked calcium transients in OECs from postnatal days 3 to 21. In summary, the results presented reveal striking differences in receptor responses during development and in axon-OEC communication between the two subpopulations of OECs in the olfactory bulb.
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Affiliation(s)
- Anne Thyssen
- Abteilung für Allgemeine Zoologie, TU Kaiserslautern, Germany
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Stavermann M, Buddrus K, St John JA, Ekberg JA, Nilius B, Deitmer JW, Lohr C. Temperature-dependent calcium-induced calcium release via InsP3 receptors in mouse olfactory ensheathing glial cells. Cell Calcium 2012; 52:113-23. [DOI: 10.1016/j.ceca.2012.04.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2011] [Revised: 03/22/2012] [Accepted: 04/24/2012] [Indexed: 02/07/2023]
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Saab AS, Neumeyer A, Jahn HM, Cupido A, Šimek AAM, Boele HJ, Scheller A, Le Meur K, Götz M, Monyer H, Sprengel R, Rubio ME, Deitmer JW, De Zeeuw CI, Kirchhoff F. Bergmann glial AMPA receptors are required for fine motor coordination. Science 2012; 337:749-53. [PMID: 22767895 DOI: 10.1126/science.1221140] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The impact of glial neurotransmitter receptors in vivo is still elusive. In the cerebellum, Bergmann glial (BG) cells express α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs) composed exclusively of GluA1 and/or GluA4 subunits. With the use of conditional gene inactivation, we found that the majority of cerebellar GluA1/A4-type AMPARs are expressed in BG cells. In young mice, deletion of BG AMPARs resulted in retraction of glial appendages from Purkinje cell (PC) synapses, increased amplitude and duration of evoked PC currents, and a delayed formation of glutamatergic synapses. In adult mice, AMPAR inactivation also caused retraction of glial processes. The physiological and structural changes were accompanied by behavioral impairments in fine motor coordination. Thus, BG AMPARs are essential to optimize synaptic integration and cerebellar output function throughout life.
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Affiliation(s)
- Aiman S Saab
- Department of Molecular Physiology, University of Saarland, Homburg, Germany
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Stridh MH, Alt MD, Wittmann S, Heidtmann H, Aggarwal M, Riederer B, Seidler U, Wennemuth G, McKenna R, Deitmer JW, Becker HM. Lactate flux in astrocytes is enhanced by a non-catalytic action of carbonic anhydrase II. J Physiol 2012; 590:2333-51. [PMID: 22451434 DOI: 10.1113/jphysiol.2011.220152] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Rapid exchange of metabolites between different cell types is crucial for energy homeostasis of the brain. Besides glucose, lactate is a major metabolite in the brain and is primarily produced in astrocytes. In the present study, we report that carbonic anhydrase 2 (CAII) enhances both influx and efflux of lactate in mouse cerebellar astrocytes. The augmentation of lactate transport is independent of the enzyme's catalytic activity, but requires direct binding of CAII to the C-terminal of the monocarboxylate transporter MCT1, one of the major lactate/proton cotransporters in astrocytes and most tissues. By employing its intramolecular proton shuttle, CAII, bound to MCT1, can act as a ‘proton collecting antenna' for the transporter, suppressing the formation of proton microdomains at the transporter-pore and thereby enhancing lactate flux. By this mechanism CAII could enhance transfer of lactate between astrocytes and neurons and thus provide the neurons with an increased supply of energy substrate.
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Affiliation(s)
- Malin H Stridh
- Division of General Zoology, Department of Biology, University of Kaiserslautern, PO Box 3049, D-67653 Kaiserslautern, Germany
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37
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Schueler C, Becker HM, McKenna R, Deitmer JW. Transport activity of the sodium bicarbonate cotransporter NBCe1 is enhanced by different isoforms of carbonic anhydrase. PLoS One 2011; 6:e27167. [PMID: 22076132 PMCID: PMC3208603 DOI: 10.1371/journal.pone.0027167] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 10/11/2011] [Indexed: 12/31/2022] Open
Abstract
Transport metabolons have been discussed between carbonic anhydrase II (CAII) and several membrane transporters. We have now studied different CA isoforms, expressed in Xenopus oocytes alone and together with the electrogenic sodium bicarbonate cotransporter 1 (NBCe1), to determine their catalytic activity and their ability to enhance NBCe1 transport activity. pH measurements in intact oocytes indicated similar activity of CAI, CAII and CAIII, while in vitro CAIII had no measurable activity and CAI only 30% of the activity of CAII. All three CA isoforms increased transport activity of NBCe1, as measured by the transport current and the rate of intracellular sodium rise in oocytes. Two CAII mutants, altered in their intramolecular proton pathway, CAII-H64A and CAII-Y7F, showed significant catalytic activity and also enhanced NBCe1 transport activity. The effect of CAI, CAII, and CAII mutants on NBCe1 activity could be reversed by blocking CA activity with ethoxyzolamide (EZA, 10 µM), while the effect of the less EZA-sensitive CAIII was not reversed. Our results indicate that different CA isoforms and mutants, even if they show little enzymatic activity in vitro, may display significant catalytic activity in intact cells, and that the ability of CA to enhance NBCe1 transport appears to depend primarily on its catalytic activity.
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Affiliation(s)
- Christina Schueler
- Abteilung für Allgemeine Zoologie, FB Biologie, TU Kaiserslautern, Kaiserslautern, Germany.
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Klier M, Schüler C, Halestrap AP, Sly WS, Deitmer JW, Becker HM. Transport activity of the high-affinity monocarboxylate transporter MCT2 is enhanced by extracellular carbonic anhydrase IV but not by intracellular carbonic anhydrase II. J Biol Chem 2011; 286:27781-91. [PMID: 21680735 DOI: 10.1074/jbc.m111.255331] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The ubiquitous enzyme carbonic anhydrase isoform II (CAII) has been shown to enhance transport activity of the proton-coupled monocarboxylate transporters MCT1 and MCT4 in a non-catalytic manner. In this study, we investigated the role of cytosolic CAII and of the extracellular, membrane-bound CA isoform IV (CAIV) on the lactate transport activity of the high-affinity monocarboxylate transporter MCT2, heterologously expressed in Xenopus oocytes. In contrast to MCT1 and MCT4, transport activity of MCT2 was not altered by CAII. However, coexpression of CAIV with MCT2 resulted in a significant increase in MCT2 transport activity when the transporter was coexpressed with its associated ancillary protein GP70 (embigin). The CAIV-mediated augmentation of MCT2 activity was independent of the catalytic activity of the enzyme, as application of the CA-inhibitor ethoxyzolamide or coexpressing the catalytically inactive mutant CAIV-V165Y did not suppress CAIV-mediated augmentation of MCT2 transport activity. Furthermore, exchange of His-88, mediating an intramolecular H(+)-shuttle in CAIV, to alanine resulted only in a slight decrease in CAIV-mediated augmentation of MCT2 activity. The data suggest that extracellular membrane-bound CAIV, but not cytosolic CAII, augments transport activity of MCT2 in a non-catalytic manner, possibly by facilitating a proton pathway other than His-88.
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Affiliation(s)
- Michael Klier
- Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Technische Universität Kaiserslautern, P. O. Box 3049, 67653 Kaiserslautern, Germany
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Weise A, Schneider HP, McKenna R, Deitmer JW. Substrate-dependent interference of carbonic anhydrases with the glutamine transporter SNAT3-induced conductance. Cell Physiol Biochem 2011; 27:79-90. [PMID: 21325825 DOI: 10.1159/000325208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2010] [Indexed: 11/19/2022] Open
Abstract
The glutamine transporter SNAT3 (SLC38A3), which also transports asparagine and histidine, exchanges sodium for protons, and displays a non-stoichiometrical conductance, which is suppressed by the catalytic activity of carbonic anhydrase II (CAII). In this study, we show that this conductance of rat SNAT3, expressed in Xenopus oocytes, is also suppressed following co-expression with CAI, CAIII, CAIV, and CAII-H64A (mutant with impaired intramolecular H(+) shuttling). All CA isoforms and the CAII mutant displayed catalytic activity in intact oocytes, although in vitro studies had reported only very low catalytic activity of CAIII and CAII-H64A. The CA-mediated suppression of conductance was only observed, however, when glutamine, but not when asparagine, was the substrate. We hypothesized that this substrate specificity of the CA action might be due to the different ion selectivity induced by the different amino acid substrates, which induce currents carried by sodium and/or protons. The ion selectivity and conductance was dependent on both pH and extracellular sodium concentration for glutamine and asparagine; however the sodium dependence of the conductance, when asparagine was the substrate, was significantly greater at higher sodium concentrations, which might explain the difference in the sensitivity of the conductance to CAs. Given the presence of CAs in most cells, substrate sensing of SNAT3 would be indicated by different membrane potential changes.
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Affiliation(s)
- Alexandra Weise
- Abteilung für Allgemeine Zoologie, FB Biologie, University of Kaiserslautern, Kaiserslautern, Germany
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40
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Wandernoth PM, Raubuch M, Mannowetz N, Becker HM, Deitmer JW, Sly WS, Wennemuth G. Role of carbonic anhydrase IV in the bicarbonate-mediated activation of murine and human sperm. PLoS One 2010; 5:e15061. [PMID: 21124840 PMCID: PMC2991337 DOI: 10.1371/journal.pone.0015061] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 10/14/2010] [Indexed: 11/19/2022] Open
Abstract
HCO3− is the signal for early activation of sperm motility. In vivo, this occurs when sperm come into contact with the HCO3− containing fluids in the reproductive tract. The activated motility enables sperm to travel the long distance to the ovum. In spermatozoa HCO3− stimulates the atypical sperm adenylyl cyclase (sAC) to promote the cAMP-mediated pathway that increases flagellar beat frequency. Stimulation of sAC may occur when HCO3− enters spermatozoa either directly by anion transport or indirectly via diffusion of CO2 with subsequent hydration by intracellular carbonic anhydrase (CA). We here show that murine sperm possess extracellular CA IV that is transferred to the sperm surface as the sperm pass through the epididymis. Comparison of CA IV expression by qRT PCR analysis confirms that the transfer takes place in the corpus epididymidis. We demonstrate murine and human sperm respond to CO2 with an increase in beat frequency, an effect that can be inhibited by ethoxyzolamide. Comparing CA activity in sperm from wild-type and CA IV−/− mice we found a 32.13% reduction in total CA activity in the latter. The CA IV−/− sperm also have a reduced response to CO2. While the beat frequency of wild-type sperm increases from 2.86±0.12 Hz to 6.87±0.34 Hz after CO2 application, beat frequency of CA IV−/− sperm only increases from 3.06±0.20 Hz to 5.29±0.47 Hz. We show, for the first time, a physiological role of CA IV that supplies sperm with HCO3−, which is necessary for stimulation of sAC and hence early activation of spermatozoa.
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Affiliation(s)
- Petra M. Wandernoth
- Department of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany
| | - Michael Raubuch
- Department of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany
| | - Nadja Mannowetz
- Department of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany
| | - Holger M. Becker
- Division of Zoology/Membrane Transport, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Joachim W. Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - William S. Sly
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Gunther Wennemuth
- Department of Anatomy and Cell Biology, Saarland University, Homburg, Saar, Germany
- * E-mail:
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Deitmer JW, Steinhäuser C. Synaptic processes-The role of glial cells. Preface. ACTA ACUST UNITED AC 2010; 63:1. [PMID: 20434019 DOI: 10.1016/j.brainresrev.2010.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 12/09/2007] [Accepted: 12/15/2007] [Indexed: 11/25/2022]
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Deitmer JW, Rose CR. REMOVED: Ion changes and signalling in perisynaptic glia. Brain Res 2009:S0006-8993(09)02125-8. [PMID: 19835850 DOI: 10.1016/j.brainres.2009.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 09/23/2009] [Accepted: 10/01/2009] [Indexed: 10/20/2022]
Abstract
This article has been removed, consistent with Elsevier Policy on Article Withdrawal. Please see (http://www.elsevier.com/locate/withdrawalpolicy). The Publisher apologizes for any inconvenience this may cause.
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Affiliation(s)
- Joachim W Deitmer
- Abteilung für Allgemeine Zoologie, FB Biologie, TU Kaiserslautern, Postfach 3049, D-67653 Kaiserslautern, Germany
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Bröer S, Schneider HP, Bröer A, Deitmer JW. Mutation of asparagine 76 in the center of glutamine transporter SNAT3 modulates substrate-induced conductances and Na+ binding. J Biol Chem 2009; 284:25823-31. [PMID: 19596860 PMCID: PMC2757984 DOI: 10.1074/jbc.m109.031013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Revised: 07/08/2009] [Indexed: 11/06/2022] Open
Abstract
The glutamine transporter SLC38A3 (SNAT3) plays an important role in the release of glutamine from brain astrocytes and the uptake of glutamine into hepatocytes. It is related to the vesicular GABA (gamma-aminobutyric acid) transporter and the SLC36 family of proton-amino acid cotransporters. The transporter carries out electroneutral Na+-glutamine cotransport-H+ antiport. In addition, substrate-induced uncoupled cation currents are observed. Mutation of asparagine 76 to glutamine or histidine in predicted transmembrane helix 1 abolished all substrate-induced currents. Mutation of asparagine 76 to aspartate rendered the transporter Na+-independent and resulted in a gain of a large substrate-induced chloride conductance in the absence of Na+. Thus, a single residue is critical for coupled and uncoupled ion flows in the glutamine transporter SNAT3. Homology modeling of SNAT3 along the structure of the related benzyl-hydantoin permease from Microbacterium liquefaciens reveals that Asn-76 is likely to be located in the center of the membrane close to the translocation pore and forms part of the predicted Na+ -binding site.
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Affiliation(s)
- Stefan Bröer
- From the Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia and
| | - Hans-Peter Schneider
- the Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Technische Universität Kaiserslautern, Erwin-Schrödinger Strasse, D-67653 Kaiserslautern, Germany
| | - Angelika Bröer
- From the Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia and
| | - Joachim W. Deitmer
- the Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Technische Universität Kaiserslautern, Erwin-Schrödinger Strasse, D-67653 Kaiserslautern, Germany
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Courjaret R, Tröger M, Deitmer JW. Suppression of GABA input by A1 adenosine receptor activation in rat cerebellar granule cells. Neuroscience 2009; 162:946-58. [PMID: 19477241 DOI: 10.1016/j.neuroscience.2009.05.045] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 05/07/2009] [Accepted: 05/21/2009] [Indexed: 12/01/2022]
Abstract
Synaptic transmission has been shown to be modulated by purinergic receptors. In the cerebellum, spontaneous inhibitory input to Purkinje neurons is enhanced by ATP via P2 receptors, while evoked excitatory input via the granule cell parallel fibers is reduced by presynaptic P1 (A1) adenosine receptors. We have now studied the modulation of the complex GABAergic input to granule cells by the purinergic receptor agonists ATP and adenosine in acute rat cerebellar tissue slices using the whole-cell patch-clamp technique. Our experiments indicate that ATP and adenosine substantially reduce the bicuculline- and gabazine-sensitive GABAergic input to granule cells. Both phasic and tonic inhibitory components were reduced leading to an increased excitability of granule cells. The effect of ATP and adenosine could be blocked by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), but not by other P1 and P2 receptor antagonists, indicating that it was mediated by activation of A1 adenosine receptors. Our results suggest that, in the cerebellar network, A1 receptor activation, known to decrease the excitatory output of granule cells, also increases their excitability by reducing their complex GABAergic input. These findings extend our knowledge on purinergic receptors, mediating multiple modulations at both inhibitory and excitatory input and output sites in the cerebellar network.
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Affiliation(s)
- R Courjaret
- Abteilung für Allgemeine Zoologie, Fachbereich Biologie, Universität Kaiserslautern, Postfach 3049, Erwin-Schrödinger-strasse 13, D-67653, Kaiserslautern, Germany.
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46
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Singaravelu K, Lohr C, Deitmer JW. Calcium-independent phospholipase A2 mediates store-operated calcium entry in rat cerebellar granule cells. Cerebellum 2009; 7:467-81. [PMID: 18784973 DOI: 10.1007/s12311-008-0050-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) has been extensively studied in non-neuronal cells, such as glial cells and smooth muscle cells, in which Ca(2+)-independent phospholipase A(2) (iPLA(2)) has been shown to play a key role in the regulation of SOCE channels. In the present study, we have investigated the role of iPLA(2) for store-operated Ca(2+) entry in rat cerebellar granule neurons in acute brain slices using confocal Ca(2+) imaging. Depletion of Ca(2+) stores by cyclopiazonic acid (CPA) induced a Ca(2+) influx, which could be inhibited by SOCE channel blockers 2-aminoethoxy-diphenylborate (2-APB) and 3,5-bistrifluoromethyl pyrazole derivative (BTP2), but not by the voltage-operated Ca(2+) channel blocker diltiazem and by the Na+ channel blocker tetrodotoxin. The inhibitors of iPLA(2), bromoenol lactone (BEL) and 1,1,1-trifluoro-2-heptadecanone, and the selective suppression of iPLA(2) expression by antisense oligodeoxynucleotides, inhibited CPA-induced Ca(2+) influx. Calmidazolium, which relieves the block of inhibitory calmodulin from iPLA(2), elicited a Ca(2+) influx similar to CPA-induced Ca(2+) entry. The product of iPLA(2), lysophosphatidylinositol, elicited a 2-APB- and BTP2-sensitive, but BEL-insensitive, Ca(2+) influx. Spontaneous Ca(2+) oscillations in granule cells in acute brain slices were reduced after inhibiting iPLA(2) activity or by blocking SOCE channels. The results suggest that depletion of Ca(2+) stores activates iPLA(2) to trigger Ca(2+) influx by the formation of lysophospholipids in these neurons.
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Becker HM, Deitmer JW. Nonenzymatic Proton Handling by Carbonic Anhydrase II during H+-Lactate Cotransport via Monocarboxylate Transporter 1. J Biol Chem 2008; 283:21655-67. [DOI: 10.1074/jbc.m802134200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Stumpf T, Zhang Q, Hirnet D, Lewandrowski U, Sickmann A, Wissenbach U, Dörr J, Lohr C, Deitmer JW, Fecher-Trost C. The Human TRPV6 Channel Protein Is Associated with Cyclophilin B in Human Placenta. J Biol Chem 2008; 283:18086-98. [DOI: 10.1074/jbc.m801821200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Doengi M, Deitmer JW, Lohr C. New evidence for purinergic signaling in the olfactory bulb: A2A and P2Y1 receptors mediate intracellular calcium release in astrocytes. FASEB J 2008; 22:2368-78. [PMID: 18310463 DOI: 10.1096/fj.07-101782] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Purinergic receptors play a key role in neuron-glia and glia-neuron interactions. In the present study, we have recorded cytosolic Ca(2+) responses using confocal imaging in astrocytes of acute olfactory bulb slices from mice (postnatal days 3-8). By application of agonists and antagonists, we identified two types of receptors, P2Y(1) and A(2A), that mediated Ca(2+) responses attributable to Ca(2+) release from intracellular stores in the astrocytes. Both receptor types were activated by application of ATP and ADP; however, when enzymatic ATP degradation was suppressed by the alkaline phosphatase inhibitor levamisole, ATP only activated MRS2179-sensitive P2Y(1) but not ZM241385-sensitive A(2A) receptors. The dose-response curve for A(2A) receptors activated by adenosine revealed an EC(50) of 0.3 microM, one order of magnitude smaller than the EC(50) of 5 microM determined for P2Y(1) receptors activated by ADP. Electrical stimulation of the olfactory nerve in the presence of glutamate receptor blockers to suppress excitation of postsynaptic neurons evoked Ca(2+) responses in most of the astrocytes, which were inhibited by blocking both P2Y(1) and A(2A) receptors. Our results indicate that olfactory nerve terminals release not only glutamate, but also ATP, which activates P2Y(1) receptors and, after degradation of ATP to adenosine, A(2A) receptors in astrocytes.
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Affiliation(s)
- Michael Doengi
- Abteilung für Allgemeine Zoologie, University of Kaiserslautern, POB 3049, D-67653 Kaiserslautern, Germany
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Hirth IC, Britz FC, Deitmer JW. G protein activation by uncaging of GTP-gamma-S in the leech giant glial cell. ACTA ACUST UNITED AC 2008; 210:3771-9. [PMID: 17951418 DOI: 10.1242/jeb.008037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Glial cells can be activated by neurotransmitters via metabotropic, G protein-coupled receptors. We have studied the effects of 'global' G protein activation by GTP-gamma-S on the membrane potential, membrane conductance, intracellular Ca(2+) and Na(+) of the giant glial cell in isolated ganglia of the leech Hirudo medicinalis. Uncaging GTP-gamma-S (injected into a giant glial cell as caged compound) by moderate UV illumination hyperpolarized the membrane due to an increase in K+ conductance. Uncaging GTP-gamma-S also evoked rises in cytosolic Ca(2+) and Na+, both of which were suppressed after depleting the intracellular Ca(2+) stores with cyclopiazonic acid (20 micromol l(-1)). Uncaging inositol-trisphosphate evoked a transient rise in cytosolic Ca(2+) and Na+ but no change in membrane potential. Injection of the fast Ca(2+) chelator BAPTA or depletion of intracellular Ca(2+) stores did not suppress the membrane hyperpolarization induced by uncaging GTP-gamma-S. Our results suggest that global activation of G proteins in the leech giant glial cell results in a rise of Ca(2+)-independent membrane K+ conductance, a rise of cytosolic Ca(2+), due to release from intracellular stores, and a rise of cytosolic Na+, presumably due to increased Na+/Ca(2+) exchange.
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Affiliation(s)
- Ingo C Hirth
- Abteilung für Allgemeine Zoologie, FB Biologie, TU Kaiserslautern, Kaiserslautern, Germany
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