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Romero-Moreno R, Czowski BJ, Harris L, Kuehn JF, White KA. Intracellular pH differentially regulates transcription of metabolic and signaling pathways in normal epithelial cells. J Biol Chem 2024:107658. [PMID: 39128712 DOI: 10.1016/j.jbc.2024.107658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2024] [Accepted: 07/31/2024] [Indexed: 08/13/2024] Open
Abstract
Intracellular pH (pHi) dynamics regulate normal cell function, and dysregulated pHi dynamics is an emerging hallmark of cancer (constitutively increased pHi) and neurodegeneration (constitutively decreased pHi). However, the molecular mechanisms by which pHi dynamics regulate cell biology are poorly understood. Here, we discovered that altering pHi in normal human breast epithelial cells triggers global transcriptional changes. We identified 176 genes differentially regulated by pHi, with pHi-dependent genes clustering in signaling and glycolytic pathways. Using various normal epithelial cell models, we showed pH-dependent Notch1 expression, with increased protein abundance at high pHi. This resulted in pH-dependent downstream signaling, with increased Notch1 signaling at high pHi. We also found that high pHi increased the expression of glycolytic enzymes and regulators of pyruvate fate, including lactate dehydrogenase and pyruvate dehydrogenase kinase. These transcriptional changes were sufficient to alter lactate production, with high pHi shifting these normal epithelial cells toward a glycolytic metabolism and increasing lactate production. Thus, pHi dynamics transcriptionally regulate signaling and metabolic pathways in normal epithelial cells. Our data reveal new molecular regulators of pHi-dependent biology and a role for increased pHi in driving the acquisition of cancer-associated signaling and metabolic changes in normal human epithelial cells.
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Affiliation(s)
- Ricardo Romero-Moreno
- Harper Cancer Research Institute, South Bend. IN, 46617, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Brandon J Czowski
- Harper Cancer Research Institute, South Bend. IN, 46617, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Lindsey Harris
- Harper Cancer Research Institute, South Bend. IN, 46617, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jessamine F Kuehn
- Harper Cancer Research Institute, South Bend. IN, 46617, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Katharine A White
- Harper Cancer Research Institute, South Bend. IN, 46617, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA.
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2
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Abstract
Cancers undergo sequential changes to proton (H+) concentration and sensing that are consequences of the disease and facilitate its further progression. The impact of protonation state on protein activity can arise from alterations to amino acids or their titration. Indeed, many cancer-initiating mutations influence pH balance, regulation or sensing in a manner that enables growth and invasion outside normal constraints as part of oncogenic transformation. These cancer-supporting effects become more prominent when tumours develop an acidic microenvironment owing to metabolic reprogramming and disordered perfusion. The ensuing intracellular and extracellular pH disturbances affect multiple aspects of tumour biology, ranging from proliferation to immune surveillance, and can even facilitate further mutagenesis. As a selection pressure, extracellular acidosis accelerates disease progression by favouring acid-resistant cancer cells, which are typically associated with aggressive phenotypes. Although acid-base disturbances in tumours often occur alongside hypoxia and lactate accumulation, there is now ample evidence for a distinct role of H+-operated responses in key events underpinning cancer. The breadth of these actions presents therapeutic opportunities to change the trajectory of disease.
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Affiliation(s)
- Pawel Swietach
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.
| | - Stine Falsig Pedersen
- Department of Biology, University of Copenhagen, University of Copenhagen, Faculty of Science, København, Denmark.
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3
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Toufiq M, Rinchai D, Bettacchioli E, Kabeer BSA, Khan T, Subba B, White O, Yurieva M, George J, Jourde-Chiche N, Chiche L, Palucka K, Chaussabel D. Harnessing large language models (LLMs) for candidate gene prioritization and selection. J Transl Med 2023; 21:728. [PMID: 37845713 PMCID: PMC10580627 DOI: 10.1186/s12967-023-04576-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 09/28/2023] [Indexed: 10/18/2023] Open
Abstract
BACKGROUND Feature selection is a critical step for translating advances afforded by systems-scale molecular profiling into actionable clinical insights. While data-driven methods are commonly utilized for selecting candidate genes, knowledge-driven methods must contend with the challenge of efficiently sifting through extensive volumes of biomedical information. This work aimed to assess the utility of large language models (LLMs) for knowledge-driven gene prioritization and selection. METHODS In this proof of concept, we focused on 11 blood transcriptional modules associated with an Erythroid cells signature. We evaluated four leading LLMs across multiple tasks. Next, we established a workflow leveraging LLMs. The steps consisted of: (1) Selecting one of the 11 modules; (2) Identifying functional convergences among constituent genes using the LLMs; (3) Scoring candidate genes across six criteria capturing the gene's biological and clinical relevance; (4) Prioritizing candidate genes and summarizing justifications; (5) Fact-checking justifications and identifying supporting references; (6) Selecting a top candidate gene based on validated scoring justifications; and (7) Factoring in transcriptome profiling data to finalize the selection of the top candidate gene. RESULTS Of the four LLMs evaluated, OpenAI's GPT-4 and Anthropic's Claude demonstrated the best performance and were chosen for the implementation of the candidate gene prioritization and selection workflow. This workflow was run in parallel for each of the 11 erythroid cell modules by participants in a data mining workshop. Module M9.2 served as an illustrative use case. The 30 candidate genes forming this module were assessed, and the top five scoring genes were identified as BCL2L1, ALAS2, SLC4A1, CA1, and FECH. Researchers carefully fact-checked the summarized scoring justifications, after which the LLMs were prompted to select a top candidate based on this information. GPT-4 initially chose BCL2L1, while Claude selected ALAS2. When transcriptional profiling data from three reference datasets were provided for additional context, GPT-4 revised its initial choice to ALAS2, whereas Claude reaffirmed its original selection for this module. CONCLUSIONS Taken together, our findings highlight the ability of LLMs to prioritize candidate genes with minimal human intervention. This suggests the potential of this technology to boost productivity, especially for tasks that require leveraging extensive biomedical knowledge.
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Affiliation(s)
- Mohammed Toufiq
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | | | - Eleonore Bettacchioli
- INSERM UMR1227, Lymphocytes B et Autoimmunité, Université de Bretagne Occidentale, Brest, France
- Service de Rhumatologie, CHU de Brest, Brest, France
| | | | - Taushif Khan
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Bishesh Subba
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Olivia White
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Marina Yurieva
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Joshy George
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | | | - Laurent Chiche
- Service de Médecine Interne, Hôpital Européen, Marseille, France
| | - Karolina Palucka
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
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Huang X, Winter D, Glover DJ, Supuran CT, Donald WA. Effects of Phosphorylation on the Activity, Inhibition and Stability of Carbonic Anhydrases. Int J Mol Sci 2023; 24:ijms24119275. [PMID: 37298228 DOI: 10.3390/ijms24119275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/23/2023] [Accepted: 05/24/2023] [Indexed: 06/12/2023] Open
Abstract
Carbonic anhydrases (CAs) are a metalloenzyme family that have important roles in cellular processes including pH homeostasis and have been implicated in multiple pathological conditions. Small molecule inhibitors have been developed to target carbonic anhydrases, but the effects of post-translational modifications (PTMs) on the activity and inhibition profiles of these enzymes remain unclear. Here, we investigate the effects of phosphorylation, the most prevalent carbonic anhydrase PTM, on the activities and drug-binding affinities of human CAI and CAII, two heavily modified active isozymes. Using serine to glutamic acid (S > E) mutations to mimic the effect of phosphorylation, we demonstrate that phosphomimics at a single site can significantly increase or decrease the catalytic efficiencies of CAs, depending on both the position of the modification and the CA isoform. We also show that the S > E mutation at Ser50 of hCAII decreases the binding affinities of hCAII with well-characterized sulphonamide inhibitors including by over 800-fold for acetazolamide. Our findings suggest that CA phosphorylation may serve as a regulatory mechanism for enzymatic activity, and affect the binding affinity and specificity of small, drug and drug-like molecules. This work should motivate future studies examining the PTM-modification forms of CAs and their distributions, which should provide insights into CA physiopathological functions and facilitate the development of 'modform-specific' carbonic anhydrase inhibitors.
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Affiliation(s)
- Xiaojing Huang
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Daniel Winter
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Dominic J Glover
- School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Claudiu T Supuran
- Neurofarba Department, Sezione di Scienze Farmaceutiche, Universita degli Studi di Firenze, Via Ugo Schiff 6, Sesto Fiorentino, 50019 Florence, Italy
| | - William A Donald
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
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5
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Lee S, Toft NJ, Axelsen TV, Espejo MS, Pedersen TM, Mele M, Pedersen HL, Balling E, Johansen T, Burton M, Thomassen M, Vahl P, Christiansen P, Boedtkjer E. Carbonic anhydrases reduce the acidity of the tumor microenvironment, promote immune infiltration, decelerate tumor growth, and improve survival in ErbB2/HER2-enriched breast cancer. Breast Cancer Res 2023; 25:46. [PMID: 37098526 PMCID: PMC10127511 DOI: 10.1186/s13058-023-01644-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/30/2023] [Indexed: 04/27/2023] Open
Abstract
BACKGROUND Carbonic anhydrases catalyze CO2/HCO3- buffer reactions with implications for effective H+ mobility, pH dynamics, and cellular acid-base sensing. Yet, the integrated consequences of carbonic anhydrases for cancer and stromal cell functions, their interactions, and patient prognosis are not yet clear. METHODS We combine (a) bioinformatic analyses of human proteomic data and bulk and single-cell transcriptomic data coupled to clinicopathologic and prognostic information; (b) ex vivo experimental studies of gene expression in breast tissue based on quantitative reverse transcription and polymerase chain reactions, intracellular and extracellular pH recordings based on fluorescence confocal microscopy, and immunohistochemical protein identification in human and murine breast cancer biopsies; and (c) in vivo tumor size measurements, pH-sensitive microelectrode recordings, and microdialysis-based metabolite analyses in mice with experimentally induced breast carcinomas. RESULTS Carbonic anhydrases-particularly the extracellular isoforms CA4, CA6, CA9, CA12, and CA14-undergo potent expression changes during human and murine breast carcinogenesis. In patients with basal-like/triple-negative breast cancer, elevated expression of the extracellular carbonic anhydrases negatively predicts survival, whereas, surprisingly, the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer. Carbonic anhydrase inhibition attenuates cellular net acid extrusion and extracellular H+ elimination from diffusion-restricted to peripheral and well-perfused regions of human and murine breast cancer tissue. Supplied in vivo, the carbonic anhydrase inhibitor acetazolamide acidifies the microenvironment of ErbB2-induced murine breast carcinomas, limits tumor immune infiltration (CD3+ T cells, CD19+ B cells, F4/80+ macrophages), lowers inflammatory cytokine (Il1a, Il1b, Il6) and transcription factor (Nfkb1) expression, and accelerates tumor growth. Supporting the immunomodulatory influences of carbonic anhydrases, patient survival benefits associated with high extracellular carbonic anhydrase expression in HER2-enriched breast carcinomas depend on the tumor inflammatory profile. Acetazolamide lowers lactate levels in breast tissue and blood without influencing breast tumor perfusion, suggesting that carbonic anhydrase inhibition lowers fermentative glycolysis. CONCLUSIONS We conclude that carbonic anhydrases (a) elevate pH in breast carcinomas by accelerating net H+ elimination from cancer cells and across the interstitial space and (b) raise immune infiltration and inflammation in ErbB2/HER2-driven breast carcinomas, restricting tumor growth and improving patient survival.
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Affiliation(s)
- Soojung Lee
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Nicolai J Toft
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Trine V Axelsen
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Maria Sofia Espejo
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Tina M Pedersen
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Marco Mele
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
| | - Helene L Pedersen
- Department of Pathology, Randers Regional Hospital, Randers, Denmark
| | - Eva Balling
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
| | - Tonje Johansen
- Department of Pathology, Randers Regional Hospital, Randers, Denmark
| | - Mark Burton
- Department of Clinical Genetics, University of Southern Denmark, Odense, Denmark
- Clinical Genome Center, University and Region of Southern Denmark, Odense, Denmark
- Department of Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Mads Thomassen
- Department of Clinical Genetics, University of Southern Denmark, Odense, Denmark
- Clinical Genome Center, University and Region of Southern Denmark, Odense, Denmark
| | - Pernille Vahl
- Department of Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - Peer Christiansen
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
- Department of Plastic and Breast Surgery, Aarhus University Hospital, Aarhus, Denmark
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark.
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6
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Potential Novel Role of Membrane-Associated Carbonic Anhydrases in the Kidney. Int J Mol Sci 2023; 24:ijms24044251. [PMID: 36835660 PMCID: PMC9961601 DOI: 10.3390/ijms24044251] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 02/06/2023] [Accepted: 02/06/2023] [Indexed: 02/23/2023] Open
Abstract
Carbonic anhydrases (CAs), because they catalyze the interconversion of carbon dioxide (CO2) and water into bicarbonate (HCO3-) and protons (H+), thereby influencing pH, are near the core of virtually all physiological processes in the body. In the kidneys, soluble and membrane-associated CAs and their synergy with acid-base transporters play important roles in urinary acid secretion, the largest component of which is the reabsorption of HCO3- in specific nephron segments. Among these transporters are the Na+-coupled HCO3- transporters (NCBTs) and the Cl--HCO3- exchangers (AEs)-members of the "solute-linked carrier" 4 (SLC4) family. All of these transporters have traditionally been regarded as "HCO3-" transporters. However, recently our group has demonstrated that two of the NCBTs carry CO32- rather than HCO3- and has hypothesized that all NCBTs follow suit. In this review, we examine current knowledge on the role of CAs and "HCO3-" transporters of the SLC4 family in renal acid-base physiology and discuss how our recent findings impact renal acid secretion, including HCO3- reabsorption. Traditionally, investigators have associated CAs with producing or consuming solutes (CO2, HCO3-, and H+) and thus ensuring their efficient transport across cell membranes. In the case of CO32- transport by NCBTs, however, we hypothesize that the role of membrane-associated CAs is not the appreciable production or consumption of substrates but the minimization of pH changes in nanodomains near the membrane.
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7
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O’Herin C, Moriuchi YW, Bemis TA, Kohlbrand AJ, Burkart MD, Cohen SM. Development of Human Carbonic Anhydrase II Heterobifunctional Degraders. J Med Chem 2023; 66:2789-2803. [PMID: 36735827 PMCID: PMC9969396 DOI: 10.1021/acs.jmedchem.2c01843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Human carbonic anhydrase II (hCAII) is a metalloenzyme essential to critical physiological processes in the body. hCA inhibitors are used clinically for the treatment of indications ranging from glaucoma to epilepsy. Targeted protein degraders have emerged as a promising means of inducing the degradation of disease-implicated proteins by using the endogenous quality control mechanisms of a cell. Here, a series of heterobifunctional degrader candidates targeting hCAII were developed from a simple aryl sulfonamide fragment. Degrader candidates were functionalized to produce either cereblon E3 ubiquitin ligase (CRBN) recruiting proteolysis targeting chimeras (PROTACs) or adamantyl-based hydrophobic tags (HyTs). Screens in HEK293 cells identified two PROTAC small-molecule degraders of hCA. Optimization of linker length and composition yielded a degrader with sub-nanomolar potency and sustained depletion of hCAII over prolonged treatments. Mechanistic studies suggest that this optimized degrader depletes hCAII through the same mechanism as previously reported CRBN-recruiting heterobifunctional degraders.
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8
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Zito F, Bonaventura R, Costa C, Russo R. Carbonic anhydrases in development: morphological observations and gene expression profiling in sea urchin embryos exposed to acetazolamide. Open Biol 2023; 13:220254. [PMID: 36597694 PMCID: PMC9811153 DOI: 10.1098/rsob.220254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Carbonic anhydrases (CANs) are conserved metalloenzymes catalysing the reversible hydration of carbon dioxide into protons and bicarbonate, with important roles in cells physiology. Some CAN-coding genes were found in sea urchin genome, although only one involved in embryonic skeletogenesis was described in Paracentrotus lividus. Here, we investigated gene expression patterns of P. lividus embryos cultured in the presence of acetazolamide (AZ), a CAN inhibitor, to combine morphological defects with their molecular underpinning. CAN inhibition blocked skeletogenesis, affected the spatial/temporal expression of some biomineralization-related genes, inhibited embryos swimming. A comparative analysis on the expression of 127 genes in control and 3 h/24 h AZ-treated embryos, using NanoString technology, showed the differential expression of genes encoding for structural/regulatory proteins, with different embryonic roles: biomineralization, transcriptional regulation, signalling, development and defence response. The study of the differentially expressed genes and the signalling pathways affected, besides in silico analyses and a speculative 'interactomic model', leads to predicting the presence of various CAN isoforms, possibly involved in different physiological processes/activities in sea urchin embryo, and their potential target genes/proteins. Our findings provide new valuable molecular data for further studies in several biological fields: developmental biology (biomineralization, axes patterning), cell differentiation (neural development) and drug toxicology (AZ effects on embryos/tissues).
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Affiliation(s)
- Francesca Zito
- Istituto per la Ricerca e l'Innovazione Biomedica, Consiglio Nazionale delle Ricerche, via Ugo La Malfa 153, Palermo 90146, Italy
| | - Rosa Bonaventura
- Istituto per la Ricerca e l'Innovazione Biomedica, Consiglio Nazionale delle Ricerche, via Ugo La Malfa 153, Palermo 90146, Italy
| | - Caterina Costa
- Istituto per la Ricerca e l'Innovazione Biomedica, Consiglio Nazionale delle Ricerche, via Ugo La Malfa 153, Palermo 90146, Italy
| | - Roberta Russo
- Istituto per la Ricerca e l'Innovazione Biomedica, Consiglio Nazionale delle Ricerche, via Ugo La Malfa 153, Palermo 90146, Italy
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Local Attraction of Substrates and Co-Substrates Enhances Weak Acid and Base Transmembrane Transport. Biomolecules 2022; 12:biom12121794. [PMID: 36551222 PMCID: PMC9775063 DOI: 10.3390/biom12121794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 11/25/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022] Open
Abstract
The transmembrane transport of weak acid and base metabolites depends on the local pH conditions that affect the protonation status of the substrates and the availability of co-substrates, typically protons. Different protein designs ensure the attraction of substrates and co-substrates to the transporter entry sites. These include electrostatic surface charges on the transport proteins and complexation with seemingly transport-unrelated proteins that provide substrate and/or proton antenna, or enzymatically generate substrates in place. Such protein assemblies affect transport rates and directionality. The lipid membrane surface also collects and transfers protons. The complexity in the various systems enables adjustability and regulation in a given physiological or pathophysiological situation. This review describes experimentally shown principles in the attraction and facilitation of weak acid and base transport substrates, including monocarboxylates, ammonium, bicarbonate, and arsenite, plus protons as a co-substrate.
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Dotsenko OI. The whole-cell kinetic metabolic model of the pH regulation mechanisms in human erythrocytes. REGULATORY MECHANISMS IN BIOSYSTEMS 2022. [DOI: 10.15421/022235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mathematical modeling in recent years helped to obtain answers to questions that were difficult or even impossible to answer experimentally, to predict several unexpected connections in cell metabolism and to understand and importance of certain biochemical reactions. Due to the complexity and variety of processes underlying the mechanisms of intracellular pH (pHi) regulation, mathematical modeling and metabolome analysis are powerful tools for their analysis. In this regard, a mathematical metabolic model for human erythrocytes was created, which combines cellular metabolism with acid-base processes and gas exchange. The model consists of the main metabolic pathways, such as glycolysis, the pentose phosphate pathway, some membrane transport systems, and interactions between hemoglobin and metabolites. The Jacobs-Stewart cycle, which is fundamental in gas exchange and pH regulation, was included to these pathways. The model was created in the COPASI environment, consisted of 85 reactions, the rate of which is based on accurate kinetic equations. The time dependences of reaction flows and metabolite concentrations, as an outcome of calculations, allowed us to reproduce the behaviour of the metabolic system after its disturbance in vitro and to establish the recovery mechanisms or approximation to stationary states. The COPASI simulation environment provides model flexibility by reproducing any experimental design by optimizing direct quantitative comparisons between measured and predicted results. Thus, the procedure of parameters optimization (Parameter Estimation) followed by the solution of the model’s differential equations (Time Course procedure) was used to predict the behaviour of all measured and unmeasured variables over time. The initial intracellular concentrations of CO2, HCO3– in human erythrocytes used for incubation in a phosphate buffer medium were calculated. Changes in CO2, HCO3– content over time were shown. It was established that the regulation of pH in erythrocytes placed in a buffer medium takes place with the participation of two types of processes – fast (takes place in 1.3 s) and slow. It is shown that fast processes are aimed at restoring the intracellular balance between CO2 and HCO3–, slow processes are aimed at establishing the balance of H+ between the cell and the extracellular environment. The role of carbonic anhydrase (CA) and hemoglobin in the processes of pH stabilization is shown and analyzed. The physiological role of the metabolon between band 3 protein (AE1), CA, aquaporin and hemoglobin in maintaining pH homeostasis in the conditions of in vitro experiments are discussed.
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11
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Jennings ML. Cell Physiology and Molecular Mechanism of Anion Transport by Erythrocyte Band 3/AE1. Am J Physiol Cell Physiol 2021; 321:C1028-C1059. [PMID: 34669510 PMCID: PMC8714990 DOI: 10.1152/ajpcell.00275.2021] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The major transmembrane protein of the red blood cell, known as band 3, AE1, and SLC4A1, has two main functions: 1) catalysis of Cl-/HCO3- exchange, one of the steps in CO2 excretion; 2) anchoring the membrane skeleton. This review summarizes the 150 year history of research on red cell anion transport and band 3 as an experimental system for studying membrane protein structure and ion transport mechanisms. Important early findings were that red cell Cl- transport is a tightly coupled 1:1 exchange and band 3 is labeled by stilbenesulfonate derivatives that inhibit anion transport. Biochemical studies showed that the protein is dimeric or tetrameric (paired dimers) and that there is one stilbenedisulfonate binding site per subunit of the dimer. Transport kinetics and inhibitor characteristics supported the idea that the transporter acts by an alternating access mechanism with intrinsic asymmetry. The sequence of band 3 cDNA provided a framework for detailed study of protein topology and amino acid residues important for transport. The identification of genetic variants produced insights into the roles of band 3 in red cell abnormalities and distal renal tubular acidosis. The publication of the membrane domain crystal structure made it possible to propose concrete molecular models of transport. Future research directions include improving our understanding of the transport mechanism at the molecular level and of the integrative relationships among band 3, hemoglobin, carbonic anhydrase, and gradients (both transmembrane and subcellular) of HCO3-, Cl-, O2, CO2, pH, and NO metabolites during pulmonary and systemic capillary gas exchange.
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Affiliation(s)
- Michael L Jennings
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
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12
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Bertling E, Blaesse P, Seja P, Kremneva E, Gateva G, Virtanen MA, Summanen M, Spoljaric I, Uvarov P, Blaesse M, Paavilainen VO, Vutskits L, Kaila K, Hotulainen P, Ruusuvuori E. Carbonic anhydrase seven bundles filamentous actin and regulates dendritic spine morphology and density. EMBO Rep 2021; 22:e50145. [PMID: 33719157 PMCID: PMC8025036 DOI: 10.15252/embr.202050145] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 01/14/2021] [Accepted: 01/28/2021] [Indexed: 01/02/2023] Open
Abstract
Intracellular pH is a potent modulator of neuronal functions. By catalyzing (de)hydration of CO2 , intracellular carbonic anhydrase (CAi ) isoforms CA2 and CA7 contribute to neuronal pH buffering and dynamics. The presence of two highly active isoforms in neurons suggests that they may serve isozyme-specific functions unrelated to CO2 -(de)hydration. Here, we show that CA7, unlike CA2, binds to filamentous actin, and its overexpression induces formation of thick actin bundles and membrane protrusions in fibroblasts. In CA7-overexpressing neurons, CA7 is enriched in dendritic spines, which leads to aberrant spine morphology. We identified amino acids unique to CA7 that are required for direct actin interactions, promoting actin filament bundling and spine targeting. Disruption of CA7 expression in neocortical neurons leads to higher spine density due to increased proportion of small spines. Thus, our work demonstrates highly distinct subcellular expression patterns of CA7 and CA2, and a novel, structural role of CA7.
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Affiliation(s)
- Enni Bertling
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Minerva Institute for Medical ResearchBiomedicum Helsinki 2UHelsinkiFinland
| | - Peter Blaesse
- Institute of Physiology IWestfälische Wilhelms‐Universität MünsterMünsterGermany
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | - Patricia Seja
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | | | | | - Mari A Virtanen
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
- Department of Anesthesiology, PharmacologyIntensive Care and Emergency MedicineUniversity Hospitals of GenevaGenevaSwitzerland
| | - Milla Summanen
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | - Inkeri Spoljaric
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | - Pavel Uvarov
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | | | | | - Laszlo Vutskits
- Department of Anesthesiology, PharmacologyIntensive Care and Emergency MedicineUniversity Hospitals of GenevaGenevaSwitzerland
| | - Kai Kaila
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
| | - Pirta Hotulainen
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Minerva Institute for Medical ResearchBiomedicum Helsinki 2UHelsinkiFinland
| | - Eva Ruusuvuori
- Neuroscience CenterHiLIFEUniversity of HelsinkiHelsinkiFinland
- Faculty of Biological and Environmental SciencesMolecular and Integrative Biosciences, and HiLIFEUniversity of HelsinkiHelsinkiFinland
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13
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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] [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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14
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Trampert DC, van de Graaf SFJ, Jongejan A, Oude Elferink RPJ, Beuers U. Hepatobiliary acid-base homeostasis: Insights from analogous secretory epithelia. J Hepatol 2021; 74:428-441. [PMID: 33342564 DOI: 10.1016/j.jhep.2020.10.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 10/03/2020] [Accepted: 10/19/2020] [Indexed: 12/14/2022]
Abstract
Many epithelia secrete bicarbonate-rich fluid to generate flow, alter viscosity, control pH and potentially protect luminal and intracellular structures from chemical stress. Bicarbonate is a key component of human bile and impaired biliary bicarbonate secretion is associated with liver damage. Major efforts have been undertaken to gain insight into acid-base homeostasis in cholangiocytes and more can be learned from analogous secretory epithelia. Extrahepatic examples include salivary and pancreatic duct cells, duodenocytes, airway and renal epithelial cells. The cellular machinery involved in acid-base homeostasis includes carbonic anhydrase enzymes, transporters of the solute carrier family, and intra- and extracellular pH sensors. This pH-regulatory system is orchestrated by protein-protein interactions, the establishment of an electrochemical gradient across the plasma membrane and bicarbonate sensing of the intra- and extracellular compartment. In this review, we discuss conserved principles identified in analogous secretory epithelia in the light of current knowledge on cholangiocyte physiology. We present a framework for cholangiocellular acid-base homeostasis supported by expression analysis of publicly available single-cell RNA sequencing datasets from human cholangiocytes, which provide insights into the molecular basis of pH homeostasis and dysregulation in the biliary system.
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Affiliation(s)
- David C Trampert
- Amsterdam UMC, University of Amsterdam, Department of Gastroenterology and Hepatology, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology Endocrinology Metabolism (AGEM), Meibergdreef 9, Amsterdam, the Netherlands
| | - Stan F J van de Graaf
- Amsterdam UMC, University of Amsterdam, Department of Gastroenterology and Hepatology, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology Endocrinology Metabolism (AGEM), Meibergdreef 9, Amsterdam, the Netherlands
| | - Aldo Jongejan
- Amsterdam UMC, University of Amsterdam, Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Meibergdreef 9, Amsterdam, the Netherlands
| | - Ronald P J Oude Elferink
- Amsterdam UMC, University of Amsterdam, Department of Gastroenterology and Hepatology, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology Endocrinology Metabolism (AGEM), Meibergdreef 9, Amsterdam, the Netherlands
| | - Ulrich Beuers
- Amsterdam UMC, University of Amsterdam, Department of Gastroenterology and Hepatology, Tytgat Institute for Liver and Intestinal Research, Amsterdam Gastroenterology Endocrinology Metabolism (AGEM), Meibergdreef 9, Amsterdam, the Netherlands.
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15
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Moss FJ, Boron WF. Carbonic anhydrases enhance activity of endogenous Na-H exchangers and not the electrogenic Na/HCO 3 cotransporter NBCe1-A, expressed in Xenopus oocytes. J Physiol 2020; 598:5821-5856. [PMID: 32969493 PMCID: PMC7747792 DOI: 10.1113/jp280143] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/07/2020] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS According to the HCO 3 - metabolon hypothesis, direct association of cytosolic carbonic anhydrases (CAs) with the electrogenic Na/HCO3 cotransporter NBCe1-A speeds transport by regenerating/consuming HCO 3 - . The present work addresses published discrepancies as to whether cytosolic CAs stimulate NBCe1-A, heterologously expressed in Xenopus oocytes. We confirm the essential elements of the previous experimental observations, taken as support for the HCO 3 - metabolon hypothesis. However, using our own experimental protocols or those of others, we find that NBCe1-A function is unaffected by cytosolic CAs. Previous conclusions that cytosolic CAs do stimulate NBCe1-A can be explained by an unanticipated stimulatory effect of the CAs on an endogenous Na-H exchanger. Theoretical analyses show that, although CAs could stimulate non- HCO 3 - transporters (e.g. Na-H exchangers) by accelerating CO2 / HCO 3 - -mediated buffering of acid-base equivalents, they could not appreciably affect transport rates of NBCe1 or other transporters carrying HCO 3 - , CO 3 = , or NaCO 3 - ion pairs. ABSTRACT The HCO 3 - metabolon hypothesis predicts that cytosolic carbonic anhydrase (CA) binds to NBCe1-A, promotes HCO 3 - replenishment/consumption, and enhances transport. Using a short step-duration current-voltage (I-V) protocol with Xenopus oocytes expressing eGFP-tagged NBCe1-A, our group reported that neither injecting human CA II (hCA II) nor fusing hCA II to the NBCe1-A carboxy terminus affects background-subtracted NBCe1 slope conductance (GNBC ), which is a direct measure of NBCe1-A activity. Others - using bovine CA (bCA), untagged NBCe1-A, and protocols keeping holding potential (Vh ) far from NBCe1-A's reversal potential (Erev ) for prolonged periods - found that bCA increases total membrane current (ΔIm ), which apparently supports the metabolon hypothesis. We systematically investigated differences in the two protocols. In oocytes expressing untagged NBCe1-A, injected with bCA and clamped to -40 mV, CO2 / HCO 3 - exposures markedly decrease Erev , producing large transient outward currents persisting for >10 min and rapid increases in [Na+ ]i . Although the CA inhibitor ethoxzolamide (EZA) reduces both ΔIm and d[Na+ ]i /dt, it does not reduce GNBC . In oocytes not expressing NBCe1-A, CO2 / HCO 3 - triggers rapid increases in [Na+ ]i that both hCA II and bCA enhance in concentration-dependent manners. These d[Na+ ]i /dt increases are inhibited by EZA and blocked by EIPA, a Na-H exchanger (NHE) inhibitor. In oocytes expressing untagged NBCe1-A and injected with bCA, EIPA abolishes the EZA-dependent decreases in ΔIm and d[Na+ ]i /dt. Thus, CAs/EZA produce their ΔIm and d[Na+ ]i /dt effects not through NBCe1-A, but endogenous NHEs. Theoretical considerations argue against a CA stimulation of HCO 3 - transport, supporting the conclusion that an NBCe1-A- HCO 3 - metabolon does not exist in oocytes.
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Affiliation(s)
- Fraser J. Moss
- Department of Physiology and Biophysics, Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Walter F. Boron
- Department of Physiology and Biophysics, Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Department of Medicine and Department of Biochemistry Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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16
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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] [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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17
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Becker HM. Carbonic anhydrase IX and acid transport in cancer. Br J Cancer 2020; 122:157-167. [PMID: 31819195 PMCID: PMC7051959 DOI: 10.1038/s41416-019-0642-z] [Citation(s) in RCA: 99] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/29/2019] [Accepted: 10/22/2019] [Indexed: 02/07/2023] Open
Abstract
Alterations in tumour metabolism and acid/base regulation result in the formation of a hostile environment, which fosters tumour growth and metastasis. Acid/base homoeostasis in cancer cells is governed by the concerted interplay between carbonic anhydrases (CAs) and various transport proteins, which either mediate proton extrusion or the shuttling of acid/base equivalents, such as bicarbonate and lactate, across the cell membrane. Accumulating evidence suggests that some of these transporters interact both directly and functionally with CAIX to form a protein complex coined the 'transport metabolon'. Transport metabolons formed between bicarbonate transporters and CAIX require CA catalytic activity and have a function in cancer cell migration and invasion. Another type of transport metabolon is formed by CAIX and monocarboxylate transporters. In this complex, CAIX functions as a proton antenna for the transporter, which drives the export of lactate and protons from the cell. Since CAIX is almost exclusively expressed in cancer cells, these transport metabolons might serve as promising targets to interfere with tumour pH regulation and energy metabolism. This review provides an overview of the current state of research on the function of CAIX in tumour acid/base transport and discusses how CAIX transport metabolons could be exploited in modern cancer therapy.
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Affiliation(s)
- Holger M Becker
- Institute of Physiological Chemistry, University of Veterinary Medicine Hannover, D-30559, Hannover, Germany.
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18
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Feng HZ, Jin JP. Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis. Am J Physiol Cell Physiol 2019; 317:C922-C931. [PMID: 31390226 DOI: 10.1152/ajpcell.00130.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO2 and HCO3- in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.
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Affiliation(s)
- Han-Zhong Feng
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - J-P Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
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19
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Occhipinti R, Boron WF. Role of Carbonic Anhydrases and Inhibitors in Acid-Base Physiology: Insights from Mathematical Modeling. Int J Mol Sci 2019; 20:E3841. [PMID: 31390837 PMCID: PMC6695913 DOI: 10.3390/ijms20153841] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 01/25/2023] Open
Abstract
Carbonic anhydrases (CAs) catalyze a reaction fundamental for life: the bidirectional conversion of carbon dioxide (CO2) and water (H2O) into bicarbonate (HCO3-) and protons (H+). These enzymes impact numerous physiological processes that occur within and across the many compartments in the body. Within compartments, CAs promote rapid H+ buffering and thus the stability of pH-sensitive processes. Between compartments, CAs promote movements of H+, CO2, HCO3-, and related species. This traffic is central to respiration, digestion, and whole-body/cellular pH regulation. Here, we focus on the role of mathematical modeling in understanding how CA enhances buffering as well as gradients that drive fluxes of CO2 and other solutes (facilitated diffusion). We also examine urinary acid secretion and the carriage of CO2 by the respiratory system. We propose that the broad physiological impact of CAs stem from three fundamental actions: promoting H+ buffering, enhancing H+ exchange between buffer systems, and facilitating diffusion. Mathematical modeling can be a powerful tool for: (1) clarifying the complex interdependencies among reaction, diffusion, and protein-mediated components of physiological processes; (2) formulating hypotheses and making predictions to be tested in wet-lab experiments; and (3) inferring data that are impossible to measure.
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Affiliation(s)
- Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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20
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21
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Hsu K. Exploring the Potential Roles of Band 3 and Aquaporin-1 in Blood CO 2 Transport-Inspired by Comparative Studies of Glycophorin B-A-B Hybrid Protein GP.Mur. Front Physiol 2018; 9:733. [PMID: 29971013 PMCID: PMC6018491 DOI: 10.3389/fphys.2018.00733] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 05/25/2018] [Indexed: 12/15/2022] Open
Abstract
The Cl—/HCO3— exchanger band 3 is functionally relevant to blood CO2 transport. Band 3 is the most abundant membrane protein in human red blood cells (RBCs). Our understanding of its physiological functions mainly came from clinical cases associated with band 3 mutations. Severe reduction in band 3 expression affects blood HCO3—/CO2 metabolism. What could happen physiologically if band 3 expression is elevated instead? In some areas of Southeast Asia, about 1–10% of the populations express GP.Mur, a glycophorin B-A-B hybrid membrane protein important in the field of transfusion medicine. GP.Mur functions to promote band 3 expression, and GP.Mur red cells can be deemed as a naturally occurred model for higher band 3 expression. This review first compares the functional consequences of band 3 at different levels, and suggests a critical role of band 3 in postnatal CO2 respiration. The second part of the review explores the transport of water, which is the other substrate for intra-erythrocytic CO2/HCO3— conversion (an essential step in blood CO2 transport). Despite that water is considered unlimited physiologically, it is unclear whether water channel aquaporin-1 (AQP1) abundantly expressed in RBCs is functionally involved in CO2 transport. Research in this area is complicated by the fact that the H2O/CO2-transporting function of AQP1 is replaceable by other erythrocyte channels/transporters (e.g., UT-B/GLUT1 for H2O; RhAG for CO2). Recently, using carbonic anhydrase II (CAII)-filled erythrocyte vesicles, AQP1 has been demonstrated to transport water for the CAII-mediated reaction, CO2(g) + H2O ⇌ HCO3—(aq) + H+(aq). AQP1 is structurally associated with some population of band 3 complexes on the erythrocyte membrane in an osmotically responsive fashion. The current findings reveal transient interaction among components within the band 3-central, CO2-transport metabolon (AQP1, band 3, CAII and deoxygenated hemoglobin). Their dynamic interaction is envisioned to facilitate blood CO2 respiration, in the presence of constantly changing osmotic and hemodynamic stresses during circulation.
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Affiliation(s)
- Kate Hsu
- Transfusion Medicine and Immunogenetics Laboratories, MacKay Memorial Hospital, Tamsui, Taiwan
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22
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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: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [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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23
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Rasmussen JK, Boedtkjer E. Carbonic anhydrase inhibitors modify intracellular pH transients and contractions of rat middle cerebral arteries during CO 2/HCO 3- fluctuations. J Cereb Blood Flow Metab 2018; 38:492-505. [PMID: 28318362 PMCID: PMC5851140 DOI: 10.1177/0271678x17699224] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The CO2/HCO3- buffer minimizes pH changes in response to acid-base loads, HCO3- provides substrate for Na+,HCO3--cotransporters and Cl-/HCO3--exchangers, and H+ and HCO3- modify vasomotor responses during acid-base disturbances. We show here that rat middle cerebral arteries express cytosolic, mitochondrial, extracellular, and secreted carbonic anhydrase isoforms that catalyze equilibration of the CO2/HCO3- buffer. Switching from CO2/HCO3--free to CO2/HCO3--containing extracellular solution results in initial intracellular acidification due to hydration of CO2 followed by gradual alkalinization due to cellular HCO3- uptake. Carbonic anhydrase inhibition decelerates the initial acidification and attenuates the associated transient vasoconstriction without affecting intracellular pH or artery tone at steady-state. Na+,HCO3--cotransport and Na+/H+-exchange activity after NH4+-prepulse-induced intracellular acidification are unaffected by carbonic anhydrase inhibition. Extracellular surface pH transients induced by transmembrane NH3 flux are evident under CO2/HCO3--free conditions but absent when the buffer capacity and apparent H+ mobility increase in the presence of CO2/HCO3- even after the inhibition of carbonic anhydrases. We conclude that (a) intracellular carbonic anhydrase activity accentuates pH transients and vasoconstriction in response to acute elevations of pCO2, (b) CO2/HCO3- minimizes extracellular surface pH transients without requiring carbonic anhydrase activity, and (c) carbonic anhydrases are not rate limiting for acid–base transport across cell membranes during recovery from intracellular acidification.
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Affiliation(s)
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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24
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Mboge MY, Mahon BP, McKenna R, Frost SC. Carbonic Anhydrases: Role in pH Control and Cancer. Metabolites 2018; 8:E19. [PMID: 29495652 PMCID: PMC5876008 DOI: 10.3390/metabo8010019] [Citation(s) in RCA: 157] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/08/2018] [Accepted: 02/22/2018] [Indexed: 02/07/2023] Open
Abstract
The pH of the tumor microenvironment drives the metastatic phenotype and chemotherapeutic resistance of tumors. Understanding the mechanisms underlying this pH-dependent phenomenon will lead to improved drug delivery and allow the identification of new therapeutic targets. This includes an understanding of the role pH plays in primary tumor cells, and the regulatory factors that permit cancer cells to thrive. Over the last decade, carbonic anhydrases (CAs) have been shown to be important mediators of tumor cell pH by modulating the bicarbonate and proton concentrations for cell survival and proliferation. This has prompted an effort to inhibit specific CA isoforms, as an anti-cancer therapeutic strategy. Of the 12 active CA isoforms, two, CA IX and XII, have been considered anti-cancer targets. However, other CA isoforms also show similar activity and tissue distribution in cancers and have not been considered as therapeutic targets for cancer treatment. In this review, we consider all the CA isoforms and their possible role in tumors and their potential as targets for cancer therapy.
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Affiliation(s)
- Mam Y Mboge
- University of Florida, College of Medicine, Department of Biochemistry and Molecular Biology, P.O. Box 100245, Gainesville, FL 32610, USA.
| | - Brian P Mahon
- University of Florida, College of Medicine, Department of Biochemistry and Molecular Biology, P.O. Box 100245, Gainesville, FL 32610, USA.
| | - Robert McKenna
- University of Florida, College of Medicine, Department of Biochemistry and Molecular Biology, P.O. Box 100245, Gainesville, FL 32610, USA.
| | - Susan C Frost
- University of Florida, College of Medicine, Department of Biochemistry and Molecular Biology, P.O. Box 100245, Gainesville, FL 32610, USA.
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25
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Abstract
The high metabolic demand of cancer cells leads to an accumulation of H+ ions in the tumour microenvironment. The disorganized tumour vasculature prevents an efficient wash-out of H+ ions released into the extracellular medium but also favours the development of tumour hypoxic regions associated with a shift towards glycolytic metabolism. Under hypoxia, the final balance of glycolysis, including breakdown of generated ATP, is the production of lactate and a stoichiometric amount of H+ ions. Another major source of H+ ions results from hydration of CO2 produced in the more oxidative tumour areas. All of these events occur at high rates in tumours to fulfil bioenergetic and biosynthetic needs. This Review summarizes the current understanding of how H+-generating metabolic processes segregate within tumours according to the distance from blood vessels and inversely how ambient acidosis influences tumour metabolism, reducing glycolysis while promoting mitochondrial activity. The Review also presents novel insights supporting the participation of acidosis in cancer progression via stimulation of autophagy and immunosuppression. Finally, recent advances in the different therapeutic modalities aiming to either block pH-regulatory systems or exploit acidosis will be discussed.
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Affiliation(s)
- Cyril Corbet
- Pole of Pharmacology and Therapeutics (FATH), Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 53 Avenue Mounier B1.53.09, B-1200 Brussels, Belgium
| | - Olivier Feron
- Pole of Pharmacology and Therapeutics (FATH), Institut de Recherche Expérimentale et Clinique (IREC), Université Catholique de Louvain, 53 Avenue Mounier B1.53.09, B-1200 Brussels, Belgium
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26
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Teplyakov E, Wu Q, Liu J, Pugacheva EM, Loukinov D, Boukaba A, Lobanenkov V, Strunnikov A. The downregulation of putative anticancer target BORIS/CTCFL in an addicted myeloid cancer cell line modulates the expression of multiple protein coding and ncRNA genes. Oncotarget 2017; 8:73448-73468. [PMID: 29088719 PMCID: PMC5650274 DOI: 10.18632/oncotarget.20627] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 08/23/2017] [Indexed: 12/27/2022] Open
Abstract
The BORIS/CTCFL gene, is a testis-specific CTCF paralog frequently erroneously activated in cancer, although its exact role in cancer remains unclear. BORIS is both a transcription factor and an architectural chromatin protein. BORIS' normal role is to establish a germline-like gene expression and remodel the epigenetic landscape in testis; it similarly remodels chromatin when activated in human cancer. Critically, at least one cancer cell line, K562, is dependent on BORIS for its self-renewal and survival. Here, we downregulate BORIS expression in the K562 cancer cell line to investigate downstream pathways regulated by BORIS. RNA-seq analyses of both mRNA and small ncRNAs, including miRNA and piRNA, in the knock-down cells revealed a set of differentially expressed genes and pathways, including both testis-specific and general proliferation factors, as well as proteins involved in transcription regulation and cell physiology. The differentially expressed genes included important transcriptional regulators such as SOX6 and LIN28A. Data indicate that both direct binding of BORIS to promoter regions and locus-control activity via long-distance chromatin domain regulation are involved. The sum of findings suggests that BORIS activation in leukemia does not just recapitulate the germline, but creates a unique regulatory network.
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Affiliation(s)
- Evgeny Teplyakov
- Molecular Epigenetics Laboratory, Guangzhou Institutes of Biomedicine and Health, Guangzhou, China.,The University of the Chinese Academy of Sciences, Beijing, China
| | - Qiongfang Wu
- Molecular Epigenetics Laboratory, Guangzhou Institutes of Biomedicine and Health, Guangzhou, China
| | - Jian Liu
- Molecular Epigenetics Laboratory, Guangzhou Institutes of Biomedicine and Health, Guangzhou, China
| | | | - Dmitry Loukinov
- NIH, NIAID, Laboratory of Immunogenetics, Rockville, MD, USA
| | - Abdelhalim Boukaba
- Molecular Epigenetics Laboratory, Guangzhou Institutes of Biomedicine and Health, Guangzhou, China
| | | | - Alexander Strunnikov
- Molecular Epigenetics Laboratory, Guangzhou Institutes of Biomedicine and Health, Guangzhou, China.,The University of the Chinese Academy of Sciences, Beijing, China
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Carre G, Ouedraogo M, Magaud C, Carreyre H, Becq F, Bois P, Supuran CT, Thibaudeau S, Vandebrouck C, Bescond J. Vasorelaxation induced by dodoneine is mediated by calcium channels blockade and carbonic anhydrase inhibition on vascular smooth muscle cells. JOURNAL OF ETHNOPHARMACOLOGY 2015; 169:8-17. [PMID: 25847623 DOI: 10.1016/j.jep.2015.03.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 03/05/2015] [Accepted: 03/12/2015] [Indexed: 06/04/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Dodoneine (Ddn) is one of the active compounds identified from Agelanthus dodoneifolius (DC.) Polhill and Wiens, a medicinal plant used in traditional medicine for the treatment of hypertension. This dihydropyranone exerts hypotensive and vasorelaxant effects on rats, and two molecular targets have been characterized: the carbonic anhydrase and the L-type calcium channel in cardiomyocytes with biochemical and electrophysiological techniques, respectively. To further evaluate the involvement of these two molecular targets in vasorelaxation, the effect of Ddn on rat vascular smooth muscle was investigated. MATERIAL AND METHODS The effects of Ddn on L-type calcium current and on resting membrane potential were characterized in A7r5 cell line using the whole-cell patch-clamp configuration. The molecular identities of carbonic anhydrase isozymes in smooth muscle cells were examined with RT-PCR. Vascular response was measured on rat aortic rings in an organ bath apparatus and the effect of Ddn on intracellular pH was determined by flow cytometry using the pH-sensitive fluorescent probe BCECF-AM [2,7-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein, Acetoxymethyl Ester]. RESULTS 100µM Ddn reduced calcium current density of about 30%. In addition, carbonic anhydrase II, III, XIII and XIV were shown to be expressed in rat aorta and inhibited in smooth muscle cells by Ddn. This inhibition resulted in a rise in pHi of about 0.31, leading to KCa channel activation, thereby inducing membrane hyperpolarization and vasorelaxation. The results of vascular reactivity experiments obtained with pharmacological tools acting on the L-type calcium current and carbonic anhydrase suggest that Ddn produces its vasorelaxant effect via the inhibition of these two molecular targets. CONCLUSION This study demonstrates that Ddn induced vasorelaxation by targeting two proteins involved in the modulation of excitation-contraction coupling: L-type calcium channels and carbonic anhydrase.
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Affiliation(s)
- Grégoire Carre
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Maurice Ouedraogo
- Laboratoire de Physiologie Animale, Université de Ouagadougou, 03 BP 7021, Ouagadougou 01, Burkina Faso
| | - Christophe Magaud
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Hélène Carreyre
- Superacid group in "Organic Synthesis" team, Université de Poitiers, CNRS UMR 7285 IC2MP, 4 avenue Michel Brunet, Poitiers 86022 Cedex, France
| | - Frédéric Becq
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Patrick Bois
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Claudiu T Supuran
- Università degli Studi di Firenze, Laboratorio di Chimica Bioinorganica, Rm 188, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Firenze), Italy
| | - Sébastien Thibaudeau
- Superacid group in "Organic Synthesis" team, Université de Poitiers, CNRS UMR 7285 IC2MP, 4 avenue Michel Brunet, Poitiers 86022 Cedex, France
| | - Clarisse Vandebrouck
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Jocelyn Bescond
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France.
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Thornell IM, Bevensee MO. Regulators of Slc4 bicarbonate transporter activity. Front Physiol 2015; 6:166. [PMID: 26124722 PMCID: PMC4464172 DOI: 10.3389/fphys.2015.00166] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/15/2015] [Indexed: 12/11/2022] Open
Abstract
The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na+-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO−3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO−3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na+ or Cl−). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family.
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Affiliation(s)
- Ian M Thornell
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Mark O Bevensee
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA ; Nephrology Research and Training Center, University of Alabama at Birmingham Birmingham, AL, USA ; Center of Glial Biology in Medicine, University of Alabama at Birmingham Birmingham, AL, USA ; Civitan International Research Center, University of Alabama at Birmingham Birmingham, AL, USA
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Krishnan D, Liu L, Wiebe SA, Casey JR, Cordat E, Alexander RT. Carbonic anhydrase II binds to and increases the activity of the epithelial sodium-proton exchanger, NHE3. Am J Physiol Renal Physiol 2015; 309:F383-92. [PMID: 26041446 DOI: 10.1152/ajprenal.00464.2014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 05/20/2015] [Indexed: 02/08/2023] Open
Abstract
Two-thirds of sodium filtered by the renal glomerulus is reabsorbed from the proximal tubule via a sodium/proton exchanger isoform 3 (NHE3)-dependent mechanism. Since sodium and bicarbonate reabsorption are coupled, we postulated that the molecules involved in their reabsorption [NHE3 and carbonic anhydrase II (CAII)] might physically and functionally interact. Consistent with this, CAII and NHE3 were closely associated in a renal proximal tubular cell culture model as revealed by a proximity ligation assay. Direct physical interaction was confirmed in solid-phase binding assays with immobilized CAII and C-terminal NHE3 glutathione-S-transferase fusion constructs. To assess the effect of CAII on NHE3 function, we expressed NHE3 in a proximal tubule cell line and measured NHE3 activity as the rate of intracellular pH recovery, following an acid load. NHE3-expressing cells had a significantly greater rate of intracellular pH recovery than controls. Inhibition of endogenous CAII activity with acetazolamide significantly decreased NHE3 activity, indicating that CAII activates NHE3. To ascertain whether CAII binding per se activates NHE3, we expressed NHE3 with wild-type CAII, a catalytically inactive CAII mutant (CAII-V143Y), or a mutant unable to bind other transporters (CAII-HEX). NHE3 activity increased upon wild-type CAII coexpression, but not in the presence of the CAII V143Y or HEX mutant. Together these studies support an association between CAII and NHE3 that alters the transporter's activity.
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Affiliation(s)
- Devishree Krishnan
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; and
| | - Lei Liu
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
| | - Shane A Wiebe
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; and
| | - Joseph R Casey
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; and
| | - Emmanuelle Cordat
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; and
| | - R Todd Alexander
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada; and Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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30
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Alka K, Casey JR. Bicarbonate transport in health and disease. IUBMB Life 2014; 66:596-615. [PMID: 25270914 DOI: 10.1002/iub.1315] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/10/2014] [Indexed: 12/28/2022]
Abstract
Bicarbonate (HCO3(-)) has a central place in human physiology as the waste product of mitochondrial energy production and for its role in pH buffering throughout the body. Because bicarbonate is impermeable to membranes, bicarbonate transport proteins are necessary to enable control of bicarbonate levels across membranes. In humans, 14 bicarbonate transport proteins, members of the SLC4 and SLC26 families, function by differing transport mechanisms. In addition, some anion channels and ZIP metal transporters contribute to bicarbonate movement across membranes. Defective bicarbonate transport leads to diseases, including systemic acidosis, brain dysfunction, kidney stones, and hypertension. Altered expression levels of bicarbonate transporters in patients with breast, colon, and lung cancer suggest an important role of these transporters in cancer.
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Affiliation(s)
- Kumari Alka
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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31
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Cure E, Cure MC, Tumkaya L, Kalkan Y, Aydin I, Kirbas A, Yilmaz A, Yuce S, Gokce MF. Topiramate ameliorates abdominal aorta cross-clamping induced liver injury in rats. SAUDI JOURNAL OF GASTROENTEROLOGY : OFFICIAL JOURNAL OF THE SAUDI GASTROENTEROLOGY ASSOCIATION 2014. [PMID: 25253365 DOI: 10.4103/1319-3767.141690.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND AND AIM Ischemia/reperfusion (I/R) injury in the liver occurs after a prolonged period of ischemia followed by restoration of hepatic blood perfusion. During the surgery of abdominal aorta, I/R injury causes damage to lower extremities and many organs, especially liver. The antioxidant and tumor necrosis factor-alpha (TNF-α) suppression effects of topiramate (TPM) have been reported in several studies. We evaluated the potential protective effect of TPM on cellular damage in liver tissue during I/R injury. MATERIALS AND METHODS Thirty male Wistar albino rats were divided into three groups: Control, I/R, and I/R plus TPM (I/R + TPM) groups. Laparotomy without I/R injury was performed in the control group. After laparotomy, cross-ligation of infrarenal abdominal aorta was applied for 2 h in I/R groups that was followed by 2 h of reperfusion. TPM (100 mg/kg/day) was orally administrated to the animals in the I/R + TPM group for seven consecutive days before I/R procedure. RESULTS The I/R group's TNF-α and interleukin-6 (IL-6) levels were significantly higher than those of the control (P = 0.010; P = 0.002) and I/R + TPM groups (P = 0.010; P = 0.002, respectively). Asymmetric dimethyl arginine (ADMA) levels of I/R group were higher than the control (P = 0.015) and I/R + TPM groups. I/R caused serious histopathological damage to liver tissue; however, TPM led to very low histopathological changes. CONCLUSION Our data demonstrated that TPM treatment prominently decreases the severity of liver I/R injury. TPM pretreatment may have preventive effects on liver injury via I/R during intra-abdominal surgery.
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Affiliation(s)
- Erkan Cure
- Department of Internal Medicine, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
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32
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Cure E, Cure MC, Tumkaya L, Kalkan Y, Aydin I, Kirbas A, Yilmaz A, Yuce S, Gokce MF. Topiramate ameliorates abdominal aorta cross-clamping induced liver injury in rats. Saudi J Gastroenterol 2014; 20:297-303. [PMID: 25253365 PMCID: PMC4196345 DOI: 10.4103/1319-3767.141690] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND AND AIM Ischemia/reperfusion (I/R) injury in the liver occurs after a prolonged period of ischemia followed by restoration of hepatic blood perfusion. During the surgery of abdominal aorta, I/R injury causes damage to lower extremities and many organs, especially liver. The antioxidant and tumor necrosis factor-alpha (TNF-α) suppression effects of topiramate (TPM) have been reported in several studies. We evaluated the potential protective effect of TPM on cellular damage in liver tissue during I/R injury. MATERIALS AND METHODS Thirty male Wistar albino rats were divided into three groups: Control, I/R, and I/R plus TPM (I/R + TPM) groups. Laparotomy without I/R injury was performed in the control group. After laparotomy, cross-ligation of infrarenal abdominal aorta was applied for 2 h in I/R groups that was followed by 2 h of reperfusion. TPM (100 mg/kg/day) was orally administrated to the animals in the I/R + TPM group for seven consecutive days before I/R procedure. RESULTS The I/R group's TNF-α and interleukin-6 (IL-6) levels were significantly higher than those of the control (P = 0.010; P = 0.002) and I/R + TPM groups (P = 0.010; P = 0.002, respectively). Asymmetric dimethyl arginine (ADMA) levels of I/R group were higher than the control (P = 0.015) and I/R + TPM groups. I/R caused serious histopathological damage to liver tissue; however, TPM led to very low histopathological changes. CONCLUSION Our data demonstrated that TPM treatment prominently decreases the severity of liver I/R injury. TPM pretreatment may have preventive effects on liver injury via I/R during intra-abdominal surgery.
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Affiliation(s)
- Erkan Cure
- Department of Internal Medicine, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
- Address for correspondence: Dr. Erkan Cure, Department of Internal Medicine, University of Recep Tayyip Erdogan, School of Medicine, Rize - 53100, Turkey. E-mail:
| | - Medine C. Cure
- Department of Biochemistry, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Levent Tumkaya
- Department of Histology and Embryology, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Yildiray Kalkan
- Department of Histology and Embryology, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Ibrahim Aydin
- Department of Surgery, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Aynur Kirbas
- Department of Biochemistry, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Arif Yilmaz
- Department of Gastroenterology, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Suleyman Yuce
- Department of Internal Medicine, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
| | - Mehmet F. Gokce
- Department of Physiology, Recep Tayyip Erdogan University, School of Medicine, Rize, Turkey
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Sowah D, Brown BF, Quon A, Alvarez BV, Casey JR. Resistance to cardiomyocyte hypertrophy in ae3-/- mice, deficient in the AE3 Cl-/HCO3- exchanger. BMC Cardiovasc Disord 2014; 14:89. [PMID: 25047106 PMCID: PMC4120010 DOI: 10.1186/1471-2261-14-89] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 07/16/2014] [Indexed: 12/21/2022] Open
Abstract
Background Cardiac hypertrophy is central to the etiology of heart failure. Understanding the molecular pathways promoting cardiac hypertrophy may identify new targets for therapeutic intervention. Sodium-proton exchanger (NHE1) activity and expression levels in the heart are elevated in many models of hypertrophy through protein kinase C (PKC)/MAPK/ERK/p90RSK pathway stimulation. Sustained NHE1 activity, however, requires an acid-loading pathway. Evidence suggests that the Cl−/HCO3− exchanger, AE3, provides this acid load. Here we explored the role of AE3 in the hypertrophic growth cascade of cardiomyocytes. Methods AE3-deficient (ae3−/−) mice were compared to wildtype (WT) littermates to examine the role of AE3 protein in the development of cardiomyocyte hypertrophy. Mouse hearts were assessed by echocardiography. As well, responses of cultured cardiomyocytes to hypertrophic stimuli were measured. pH regulation capacity of ae3−/− and WT cardiomyocytes was assessed in cultured cells loaded with the pH-sensitive dye, BCECF-AM. Results ae3−/− mice were indistinguishable from wild type (WT) mice in terms of cardiovascular performance. Stimulation of ae3−/− cardiomyocytes with hypertrophic agonists did not increase cardiac growth or reactivate the fetal gene program. ae3−/− mice are thus protected from pro-hypertrophic stimulation. Steady state intracellular pH (pHi) in ae3−/− cardiomyocytes was not significantly different from WT, but the rate of recovery of pHi from imposed alkalosis was significantly slower in ae3−/− cardiomyocytes. Conclusions These data reveal the importance of AE3-mediated Cl−/HCO3− exchange in cardiovascular pH regulation and the development of cardiomyocyte hypertrophy. Pharmacological antagonism of AE3 is an attractive approach in the treatment of cardiac hypertrophy.
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Affiliation(s)
| | | | | | | | - Joseph R Casey
- Department of Biochemistry and Membrane Protein Disease Research Group, University of Alberta, Edmonton T6G 2H7, Canada.
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34
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Yan Q, Sharma-Kuinkel BK, Deshmukh H, Tsalik EL, Cyr DD, Lucas J, Woods CW, Scott WK, Sempowski GD, Thaden J, Rude TH, Ahn SH, Fowler VG. Dusp3 and Psme3 are associated with murine susceptibility to Staphylococcus aureus infection and human sepsis. PLoS Pathog 2014; 10:e1004149. [PMID: 24901344 PMCID: PMC4047107 DOI: 10.1371/journal.ppat.1004149] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 04/12/2014] [Indexed: 01/21/2023] Open
Abstract
Using A/J mice, which are susceptible to Staphylococcus aureus, we sought to identify genetic determinants of susceptibility to S. aureus, and evaluate their function with regard to S. aureus infection. One QTL region on chromosome 11 containing 422 genes was found to be significantly associated with susceptibility to S. aureus infection. Of these 422 genes, whole genome transcription profiling identified five genes (Dcaf7, Dusp3, Fam134c, Psme3, and Slc4a1) that were significantly differentially expressed in a) S. aureus -infected susceptible (A/J) vs. resistant (C57BL/6J) mice and b) humans with S. aureus blood stream infection vs. healthy subjects. Three of these genes (Dcaf7, Dusp3, and Psme3) were down-regulated in susceptible vs. resistant mice at both pre- and post-infection time points by qPCR. siRNA-mediated knockdown of Dusp3 and Psme3 induced significant increases of cytokine production in S. aureus-challenged RAW264.7 macrophages and bone marrow derived macrophages (BMDMs) through enhancing NF-κB signaling activity. Similar increases in cytokine production and NF-κB activity were also seen in BMDMs from CSS11 (C57BL/6J background with chromosome 11 from A/J), but not C57BL/6J. These findings suggest that Dusp3 and Psme3 contribute to S. aureus infection susceptibility in A/J mice and play a role in human S. aureus infection.
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Affiliation(s)
- Qin Yan
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Batu K. Sharma-Kuinkel
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Hitesh Deshmukh
- Division of Neonatology, Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Ephraim L. Tsalik
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
- Emergency Medicine Service, Durham Veteran's Affairs Medical Center, Durham, North Carolina, United States of America
- Duke Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
| | - Derek D. Cyr
- Duke Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
| | - Joseph Lucas
- Quintiles Innovations, Morrisville, North Carolina, United States of America
| | - Christopher W. Woods
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
- Duke Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
- Section on Infectious Diseases, Durham Veteran's Affairs Medical Center, Durham, North Carolina, United States of America
| | - William K. Scott
- Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | | | - Joshua Thaden
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
- Duke Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
- Duke Clinical Research Institute, Durham, North Carolina, United States of America
| | - Thomas H. Rude
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Sun Hee Ahn
- Department of Biochemistry School of Dentistry, Chonnam National University, Bukgu, Gwangju, Korea
| | - Vance G. Fowler
- Division of Infectious Diseases & International Health, Department of Medicine, Duke University School of Medicine, Durham, North Carolina, United States of America
- Duke Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
- Duke Clinical Research Institute, Durham, North Carolina, United States of America
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Endeward V, Al-Samir S, Itel F, Gros G. How does carbon dioxide permeate cell membranes? A discussion of concepts, results and methods. Front Physiol 2014; 4:382. [PMID: 24409149 PMCID: PMC3884148 DOI: 10.3389/fphys.2013.00382] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/05/2013] [Indexed: 12/13/2022] Open
Abstract
We review briefly how the thinking about the permeation of gases, especially CO2, across cell and artificial lipid membranes has evolved during the last 100 years. We then describe how the recent finding of a drastic effect of cholesterol on CO2 permeability of both biological and artificial membranes fundamentally alters the long-standing idea that CO2—as well as other gases—permeates all membranes with great ease. This requires revision of the widely accepted paradigm that membranes never offer a serious diffusion resistance to CO2 or other gases. Earlier observations of “CO2-impermeable membranes” can now be explained by the high cholesterol content of some membranes. Thus, cholesterol is a membrane component that nature can use to adapt membrane CO2 permeability to the functional needs of the cell. Since cholesterol serves many other cellular functions, it cannot be reduced indefinitely. We show, however, that cells that possess a high metabolic rate and/or a high rate of O2 and CO2 exchange, do require very high CO2 permeabilities that may not be achievable merely by reduction of membrane cholesterol. The article then discusses the alternative possibility of raising the CO2 permeability of a membrane by incorporating protein CO2 channels. The highly controversial issue of gas and CO2 channels is systematically and critically reviewed. It is concluded that a majority of the results considered to be reliable, is in favor of the concept of existence and functional relevance of protein gas channels. The effect of intracellular carbonic anhydrase, which has recently been proposed as an alternative mechanism to a membrane CO2 channel, is analysed quantitatively and the idea considered untenable. After a brief review of the knowledge on permeation of O2 and NO through membranes, we present a summary of the 18O method used to measure the CO2 permeability of membranes and discuss quantitatively critical questions that may be addressed to this method.
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Affiliation(s)
- Volker Endeward
- Zentrum Physiologie, Vegetative Physiologie 4220, Medizinische Hochschule Hannover Hannover, Germany
| | - Samer Al-Samir
- Zentrum Physiologie, Vegetative Physiologie 4220, Medizinische Hochschule Hannover Hannover, Germany
| | - Fabian Itel
- Departement Chemie, Universität Basel Basel, Switzerland
| | - Gerolf Gros
- Zentrum Physiologie, Vegetative Physiologie 4220, Medizinische Hochschule Hannover Hannover, Germany
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Villafuerte FC, Swietach P, Youm JB, Ford K, Cardenas R, Supuran CT, Cobden PM, Rohling M, Vaughan-Jones RD. Facilitation by intracellular carbonic anhydrase of Na+ -HCO3- co-transport but not Na+ / H+ exchange activity in the mammalian ventricular myocyte. J Physiol 2013; 592:991-1007. [PMID: 24297849 PMCID: PMC3948559 DOI: 10.1113/jphysiol.2013.265439] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Carbonic anhydrase enzymes (CAs) catalyse the reversible hydration of CO2 to H+ and HCO3- ions. This catalysis is proposed to be harnessed by acid/base transporters, to facilitate their transmembrane flux activity, either through direct protein-protein binding (a 'transport metabolon') or local functional interaction. Flux facilitation has previously been investigated by heterologous co-expression of relevant proteins in host cell lines/oocytes. Here, we examine the influence of intrinsic CA activity on membrane HCO3- or H+ transport via the native acid-extruding proteins, Na+ -HCO3- cotransport (NBC) and Na+ / H+ exchange (NHE), expressed in enzymically isolated mammalian ventricular myocytes. Effects of intracellular and extracellular (exofacial) CA (CAi and CAe) are distinguished using membrane-permeant and -impermeant pharmacological CA inhibitors, while measuring transporter activity in the intact cell using pH and Na+ fluorophores. We find that NBC, but not NHE flux is enhanced by catalytic CA activity, with facilitation being confined to CAi activity alone. Results are quantitatively consistent with a model where CAi catalyses local H+ ion delivery to the NBC protein, assisting the subsequent (uncatalysed) protonation and removal of imported HCO3- ions. In well-superfused myocytes, exofacial CA activity is superfluous, most likely because extracellular CO2/HCO3- buffer is clamped at equilibrium. The CAi insensitivity of NHE flux suggests that, in the native cell, intrinsic mobile buffer-shuttles supply sufficient intracellular H+ ions to this transporter, while intrinsic buffer access to NBC proteins is restricted. Our results demonstrate a selective CA facilitation of acid/base transporters in the ventricular myocyte, implying a specific role for the intracellular enzyme in HCO3- transport, and hence pHi regulation in the heart.
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Affiliation(s)
- Francisco C Villafuerte
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK.
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Deitmer JW, Becker HM. Transport metabolons with carbonic anhydrases. Front Physiol 2013; 4:291. [PMID: 24133456 PMCID: PMC3794380 DOI: 10.3389/fphys.2013.00291] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 09/24/2013] [Indexed: 01/02/2023] Open
Affiliation(s)
- Joachim W Deitmer
- General Zoology, University of Kaiserslautern Kaiserslautern, Germany
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Peña-Münzenmayer G, Niemeyer MI, Sepúlveda FV, Cid LP. Zebrafish and mouse TASK-2 K(+) channels are inhibited by increased CO2 and intracellular acidification. Pflugers Arch 2013; 466:1317-27. [PMID: 24081451 DOI: 10.1007/s00424-013-1365-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 11/28/2022]
Abstract
TASK-2 is a K2P K(+) channel considered as a candidate to mediate CO2 sensing in central chemosensory neurons in mouse. Neuroepithelial cells in zebrafish gills sense CO2 levels through an unidentified K2P K(+) channel. We have now obtained zfTASK-2 from zebrafish gill tissue that is 49 % identical to mTASK-2. Like its mouse equivalent, it is gated both by extra- and intracellular pH being activated by alkalinization and inhibited by acidification. The pHi dependence of zfTASK-2 is similar to that of mTASK-2, with pK 1/2 values of 7.9 and 8.0, respectively, but pHo dependence occurs with a pK 1/2 of 8.8 (8.0 for mTASK-2) in line with the relatively alkaline plasma pH found in fish. Increasing CO2 led to a rapid, concentration-dependent (IC50 ~1.5 % CO2) inhibition of mouse and zfTASK-2 that could be resolved into an inhibition by intracellular acidification and a CO2 effect independent of pHi change. Indeed a CO2 effect persisted despite using strongly buffered intracellular solutions abolishing any change in pHi, was present in TASK-2-K245A mutant insensitive to pHi, and also under carbonic anhydrase inhibition. The mechanism by which TASK-2 senses CO2 is unknown but requires the presence of the 245-273 stretch of amino acids in the C terminus that comprises numerous basic amino acids and is important in TASK-2 G protein subunit binding and regulation of the channel. The described CO2 effect might be of importance in the eventual roles played by TASK-2 in chemoreception in mouse and zebrafish.
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