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Huerta M, Franco-Serrano L, Amela I, Perez-Pons JA, Piñol J, Mozo-Villarías A, Querol E, Cedano J. Role of Moonlighting Proteins in Disease: Analyzing the Contribution of Canonical and Moonlighting Functions in Disease Progression. Cells 2023; 12:cells12020235. [PMID: 36672169 PMCID: PMC9857295 DOI: 10.3390/cells12020235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/27/2022] [Accepted: 12/29/2022] [Indexed: 01/09/2023] Open
Abstract
The term moonlighting proteins refers to those proteins that present alternative functions performed by a single polypeptide chain acquired throughout evolution (called canonical and moonlighting, respectively). Over 78% of moonlighting proteins are involved in human diseases, 48% are targeted by current drugs, and over 25% of them are involved in the virulence of pathogenic microorganisms. These facts encouraged us to study the link between the functions of moonlighting proteins and disease. We found a large number of moonlighting functions activated by pathological conditions that are highly involved in disease development and progression. The factors that activate some moonlighting functions take place only in pathological conditions, such as specific cellular translocations or changes in protein structure. Some moonlighting functions are involved in disease promotion while others are involved in curbing it. The disease-impairing moonlighting functions attempt to restore the homeostasis, or to reduce the damage linked to the imbalance caused by the disease. The disease-promoting moonlighting functions primarily involve the immune system, mesenchyme cross-talk, or excessive tissue proliferation. We often find moonlighting functions linked to the canonical function in a pathological context. Moonlighting functions are especially coordinated in inflammation and cancer. Wound healing and epithelial to mesenchymal transition are very representative. They involve multiple moonlighting proteins with a different role in each phase of the process, contributing to the current-phase phenotype or promoting a phase switch, mitigating the damage or intensifying the remodeling. All of this implies a new level of complexity in the study of pathology genesis, progression, and treatment. The specific protein function involved in a patient's progress or that is affected by a drug must be elucidated for the correct treatment of diseases.
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De Vecchis D, Reithmeier RAF, Kalli AC. Molecular Simulations of Intact Anion Exchanger 1 Reveal Specific Domain and Lipid Interactions. Biophys J 2019; 117:1364-1379. [PMID: 31540709 PMCID: PMC6818359 DOI: 10.1016/j.bpj.2019.08.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 07/30/2019] [Accepted: 08/22/2019] [Indexed: 12/23/2022] Open
Abstract
Anion exchanger 1 (AE1) is responsible for the exchange of bicarbonate and chloride across the erythrocyte plasma membrane. Human AE1 consists of a cytoplasmic and a membrane domain joined by a 33-residue flexible linker. Crystal structures of the individual domains have been determined, but the intact AE1 structure remains elusive. In this study, we use molecular dynamics simulations and modeling to build intact AE1 structures in a complex lipid bilayer that resembles the native erythrocyte plasma membrane. AE1 models were evaluated using available experimental data to provide an atomistic view of the interaction and dynamics of the cytoplasmic domain, the membrane domain, and the connecting linker in a complete model of AE1 in a lipid bilayer. Anionic lipids were found to interact strongly with AE1 at specific amino acid residues that are linked to diseases and blood group antigens. Cholesterol was found in the dimeric interface of AE1, suggesting that it may regulate subunit interactions and anion transport.
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Affiliation(s)
- Dario De Vecchis
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom
| | | | - Antreas C Kalli
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, United Kingdom; Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom.
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Clarkson YL, Weatherall E, Waterfall M, McLaughlin M, Lu H, Skehel PA, Anderson RA, Telfer EE. Extracellular Localisation of the C-Terminus of DDX4 Confirmed by Immunocytochemistry and Fluorescence-Activated Cell Sorting. Cells 2019; 8:cells8060578. [PMID: 31212843 PMCID: PMC6627596 DOI: 10.3390/cells8060578] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 06/06/2019] [Accepted: 06/09/2019] [Indexed: 02/03/2023] Open
Abstract
Putative oogonial stem cells (OSCs) have been isolated by fluorescence-activated cell sorting (FACS) from adult human ovarian tissue using an antibody against DEAD-box helicase 4 (DDX4). DDX4 has been reported to be germ cell specific within the gonads and localised intracellularly. White et al. (2012) hypothesised that the C-terminus of DDX4 is localised on the surface of putative OSCs but is internalised during the process of oogenesis. This hypothesis is controversial since it is assumed that RNA helicases function intracellularly with no extracellular expression. To determine whether the C-terminus of DDX4 could be expressed on the cell surface, we generated a novel expression construct to express full-length DDX4 as a DsRed2 fusion protein with unique C- and N-terminal epitope tags. DDX4 and the C-terminal myc tag were detected at the cell surface by immunocytochemistry and FACS of non-permeabilised human embryonic kidney HEK 293T cells transfected with the DDX4 construct. DDX4 mRNA expression was detected in the DDX4-positive sorted cells by RT-PCR. This study clearly demonstrates that the C-terminus of DDX4 can be expressed on the cell surface despite its lack of a conventional membrane-targeting or secretory sequence. These results validate the use of antibody-based FACS to isolate DDX4-positive putative OSCs.
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Affiliation(s)
- Yvonne L Clarkson
- Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3FF, UK.
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
| | - Emma Weatherall
- Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3FF, UK.
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
| | - Martin Waterfall
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
| | - Marie McLaughlin
- Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3FF, UK.
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
| | - Haojiang Lu
- Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3FF, UK.
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
| | - Paul A Skehel
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
| | - Richard A Anderson
- MRC Centre for Reproductive Health, Queens Medical Research Institute, University of Edinburgh, Edinburgh EH16 4TJ, UK.
| | - Evelyn E Telfer
- Institute of Cell Biology, University of Edinburgh, Edinburgh EH9 3FF, UK.
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh EH8 9XD, UK.
- Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
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Rivera-Santiago R, Harper SL, Sriswasdi S, Hembach P, Speicher DW. Full-Length Anion Exchanger 1 Structure and Interactions with Ankyrin-1 Determined by Zero Length Crosslinking of Erythrocyte Membranes. Structure 2016; 25:132-145. [PMID: 27989623 DOI: 10.1016/j.str.2016.11.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 11/02/2016] [Accepted: 11/18/2016] [Indexed: 11/26/2022]
Abstract
Anion exchanger 1 (AE1) is a critical transporter and the primary structural scaffold for large macromolecular complexes responsible for erythrocyte membrane flexibility and integrity. We used zero-length crosslinking and mass spectrometry to probe AE1 structures and interactions in intact erythrocyte membranes. An experimentally verified full-length model of AE1 dimers was developed by combining crosslink-defined distance constraints with homology modeling. Previously unresolved cytoplasmic loops in the AE1 C-terminal domain are packed at the domain-domain interface on the cytoplasmic face of the membrane where they anchor the N-terminal domain's location and prevent it from occluding the ion channel. Crosslinks between AE1 dimers and ankyrin-1 indicate the likely topology for AE1 tetramers and suggest that ankyrin-1 wraps around AE1 tetramers, which may stabilize this oligomer state. This interaction and interactions of AE1 with other major erythrocyte membrane proteins show that protein-protein contacts are often substantially more extensive than previously reported.
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Affiliation(s)
- Roland Rivera-Santiago
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Sandra L Harper
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Sira Sriswasdi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Peter Hembach
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - David W Speicher
- The Center for Systems and Computational Biology and Molecular and Cellular Oncogenesis Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.
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Chen J, Zhou Y, Gao Y, Cao W, Sun H, Liu Y, Wang C. A genetic features and gene interaction study for identifying the genes that cause hereditary spherocytosis. ACTA ACUST UNITED AC 2016; 22:240-247. [PMID: 27696975 DOI: 10.1080/10245332.2016.1235673] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
OBJECTIVE Hereditary spherocytosis (HS) is a hemolytic disorder characterized by the presence of spherical-shaped red blood cells on the peripheral blood smear. Non-dominant HS cases are due to de novo mutations of the type associated with dominant inheritance or recessive genes. This study is aimed to identify HS-related biological mechanisms and predicting HS candidate genes. METHODS We searched the known HS-related genes from the public databases. By analyzing the gene ontology (GO) and biological pathway of these genes, we extracted the optimal features to encode HS genes. Based on them, we predicted the HS-related genes from genes of whole genomes using the Random Forest classification. We used the gene interaction networks analysis to further identify the core regulatory genes that were related to HS. RESULTS Forty-one known HS-related genes were found out and encoded. Three hundred and sixty-seven GO terms and ten biological pathway terms were identified as the optimal features for prediction. We subsequently predicted 150 novel HS-related genes and identified the core regulatory genes in the interaction network of predicted and known genes. These features and genes that we identified could complement the genetic features of HS.
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Affiliation(s)
- Jing Chen
- a Nursing College of Zhengzhou University , Zhengzhou , China
| | - Yang Zhou
- b Department of Hematology , The First Affiliated Hospital of Zhengzhou University , Zhengzhou , China
| | - Yaqi Gao
- c Nursing College of Hebi Polytechnic , Hebi , China
| | - Weijie Cao
- b Department of Hematology , The First Affiliated Hospital of Zhengzhou University , Zhengzhou , China
| | - Hui Sun
- b Department of Hematology , The First Affiliated Hospital of Zhengzhou University , Zhengzhou , China
| | - Yanfang Liu
- b Department of Hematology , The First Affiliated Hospital of Zhengzhou University , Zhengzhou , China
| | - Chong Wang
- b Department of Hematology , The First Affiliated Hospital of Zhengzhou University , Zhengzhou , China
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Reithmeier RAF, Casey JR, Kalli AC, Sansom MSP, Alguel Y, Iwata S. Band 3, the human red cell chloride/bicarbonate anion exchanger (AE1, SLC4A1), in a structural context. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1507-32. [PMID: 27058983 DOI: 10.1016/j.bbamem.2016.03.030] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/21/2016] [Accepted: 03/29/2016] [Indexed: 02/03/2023]
Abstract
The crystal structure of the dimeric membrane domain of human Band 3(1), the red cell chloride/bicarbonate anion exchanger 1 (AE1, SLC4A1), provides a structural context for over four decades of studies into this historic and important membrane glycoprotein. In this review, we highlight the key structural features responsible for anion binding and translocation and have integrated the following topological markers within the Band 3 structure: blood group antigens, N-glycosylation site, protease cleavage sites, inhibitor and chemical labeling sites, and the results of scanning cysteine and N-glycosylation mutagenesis. Locations of mutations linked to human disease, including those responsible for Southeast Asian ovalocytosis, hereditary stomatocytosis, hereditary spherocytosis, and distal renal tubular acidosis, provide molecular insights into their effect on Band 3 folding. Finally, molecular dynamics simulations of phosphatidylcholine self-assembled around Band 3 provide a view of this membrane protein within a lipid bilayer.
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Affiliation(s)
- Reinhart A F Reithmeier
- Department of Biochemistry, 1 King's College Circle, University of Toronto, Toronto M5S 1A8, Canada.
| | - Joseph R Casey
- Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Antreas C Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Yilmaz Alguel
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
| | - So Iwata
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
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Genetet S, Ripoche P, Le Van Kim C, Colin Y, Lopez C. Evidence of a structural and functional ammonium transporter RhBG·anion exchanger 1·ankyrin-G complex in kidney epithelial cells. J Biol Chem 2015; 290:6925-36. [PMID: 25616663 DOI: 10.1074/jbc.m114.610048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The renal ammonium transporter RhBG and anion exchanger 1 kAE1 colocalize in the basolateral domain of α-intercalated cells in the distal nephron. Although we have previously shown that RhBG is linked to the spectrin-based skeleton through ankyrin-G and that its NH3 transport activity is dependent on this association, there is no evidence for an interaction of kAE1 with this adaptor protein. We report here that the kAE1 cytoplasmic N terminus actually binds to ankyrin-G, both in yeast two-hybrid analysis and by coimmunoprecipitation in situ in HEK293 cells expressing recombinant kAE1. A site-directed mutagenesis study allowed the identification of three dispersed regions on kAE1 molecule linking the third and fourth repeat domains of ankyrin-G. One secondary docking site corresponds to a major interacting loop of the erythroid anion exchanger 1 (eAE1) with ankyrin-R, whereas the main binding region of kAE1 does not encompass any eAE1 determinant. Stopped flow spectrofluorometry analysis of recombinant HEK293 cells revealed that the Cl(-)/HCO3 (-) exchange activity of a kAE1 protein mutated on the ankyrin-G binding site was abolished. This disruption impaired plasma membrane expression of kAE1 leading to total retention on cytoplasmic structures in polarized epithelial Madin-Darby canine kidney cell transfectants. kAE1 also directly interacts with RhBG without affecting its surface expression and NH3 transport function. This is the first description of a structural and functional RhBG·kAE1·ankyrin-G complex at the plasma membrane of kidney epithelial cells, comparable with the well known Rh·eAE1·ankyrin-R complex in the red blood cell membrane. This renal complex could participate in the regulation of acid-base homeostasis.
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Affiliation(s)
- Sandrine Genetet
- From INSERM U1134, 75739 Paris, France, the Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, 75739 Paris, France, the Institut National de la Transfusion Sanguine, 75739 Paris, France, and the Laboratoire d'Excellence GR-Ex, 75238 Paris, France
| | - Pierre Ripoche
- From INSERM U1134, 75739 Paris, France, the Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, 75739 Paris, France, the Institut National de la Transfusion Sanguine, 75739 Paris, France, and the Laboratoire d'Excellence GR-Ex, 75238 Paris, France
| | - Caroline Le Van Kim
- From INSERM U1134, 75739 Paris, France, the Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, 75739 Paris, France, the Institut National de la Transfusion Sanguine, 75739 Paris, France, and the Laboratoire d'Excellence GR-Ex, 75238 Paris, France
| | - Yves Colin
- From INSERM U1134, 75739 Paris, France, the Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, 75739 Paris, France, the Institut National de la Transfusion Sanguine, 75739 Paris, France, and the Laboratoire d'Excellence GR-Ex, 75238 Paris, France
| | - Claude Lopez
- From INSERM U1134, 75739 Paris, France, the Université Paris Diderot, Sorbonne Paris Cité, UMR_S1134, 75739 Paris, France, the Institut National de la Transfusion Sanguine, 75739 Paris, France, and the Laboratoire d'Excellence GR-Ex, 75238 Paris, France
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8
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Satchwell TJ, Hawley BR, Bell AJ, Ribeiro ML, Toye AM. The cytoskeletal binding domain of band 3 is required for multiprotein complex formation and retention during erythropoiesis. Haematologica 2014; 100:133-42. [PMID: 25344524 DOI: 10.3324/haematol.2014.114538] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Band 3 is the most abundant protein in the erythrocyte membrane and forms the core of a major multiprotein complex. The absence of band 3 in human erythrocytes has only been reported once, in the homozygous band 3 Coimbra patient. We used in vitro culture of erythroblasts derived from this patient, and separately short hairpin RNA-mediated depletion of band 3, to investigate the development of a band 3-deficient erythrocyte membrane and to specifically assess the stability and retention of band 3 dependent proteins in the absence of this core protein during terminal erythroid differentiation. Further, using lentiviral transduction of N-terminally green fluorescent protein-tagged band 3, we demonstrated the ability to restore expression of band 3 to normal levels and to rescue secondary deficiencies of key proteins including glycophorin A, protein 4.2, CD47 and Rh proteins arising from the absence of band 3 in this patient. By transducing band 3-deficient erythroblasts from this patient with band 3 mutants with absent or impaired ability to associate with the cytoskeleton we also demonstrated the importance of cytoskeletal connectivity for retention both of band 3 and of its associated dependent proteins within the reticulocyte membrane during the process of erythroblast enucleation.
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Affiliation(s)
- Timothy J Satchwell
- School of Biochemistry, Medical Sciences Building, University Walk, Bristol, UK Bristol Institute of Transfusion Sciences, NHSBT Filton, Bristol, UK
| | - Bethan R Hawley
- School of Biochemistry, Medical Sciences Building, University Walk, Bristol, UK Bristol Institute of Transfusion Sciences, NHSBT Filton, Bristol, UK
| | - Amanda J Bell
- School of Biochemistry, Medical Sciences Building, University Walk, Bristol, UK
| | - M Leticia Ribeiro
- Servico de Hematologia Clinica, Centro Hospitalar e Universitario de Coimbra, Portugal
| | - Ashley M Toye
- School of Biochemistry, Medical Sciences Building, University Walk, Bristol, UK Bristol Institute of Transfusion Sciences, NHSBT Filton, Bristol, UK
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Okawa Y, Li J, Basu A, Casey JR, Reithmeier RAF. Differential roles of tryptophan residues in the functional expression of human anion exchanger 1 (AE1, Band 3, SLC4A1). Mol Membr Biol 2014; 31:211-27. [PMID: 25257781 DOI: 10.3109/09687688.2014.955829] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Anion exchanger 1 (AE1) is a 95 kDa glycoprotein that facilitates Cl(-)=HCO(-)(3) exchange across the erythrocyte plasma membrane. This transport activity resides in the 52 kDa C-terminal membrane domain (Gly(361)-Val(911)) predicted to span the membrane 14 times. To explore the role of tryptophan (Trp) residues in AE1 function, the seven endogenous Trp residues in the membrane domain were mutated individually to alanine (Ala) and phenylalanine (Phe). Expression levels, cell surface abundance, inhibitor binding and transport activities of the mutants were measured upon expression in HEK-293 cells. The seven Trp residues divided into three classes according the impact of mutations on the functional expression of AE1: Class 1, dramatically decreased expression (Trp(492) and Trp(496)); Class 2, decreased expression by Ala substitution but not Phe (Trp(648), Trp(662) and Trp(723)); and Class 3, normal expression (Trp(831) and Trp(848)). The results indicate that Trp residues play differential roles in AE1 expression and function depending on their location in the protein and that Trp mutants with low expression are misfolded and retained in the endoplasmic reticulum.
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Affiliation(s)
- Yuka Okawa
- Department of Biochemistry, University of Toronto , Toronto, Canada and
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10
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Cordat E, Reithmeier RA. Structure, Function, and Trafficking of SLC4 and SLC26 Anion Transporters. CURRENT TOPICS IN MEMBRANES 2014; 73:1-67. [DOI: 10.1016/b978-0-12-800223-0.00001-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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11
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Shnitsar V, Li J, Li X, Calmettes C, Basu A, Casey JR, Moraes TF, Reithmeier RAF. A substrate access tunnel in the cytosolic domain is not an essential feature of the solute carrier 4 (SLC4) family of bicarbonate transporters. J Biol Chem 2013; 288:33848-33860. [PMID: 24121512 DOI: 10.1074/jbc.m113.511865] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Anion exchanger 1 (AE1; Band 3; SLC4A1) is the founding member of the solute carrier 4 (SLC4) family of bicarbonate transporters that includes chloride/bicarbonate AEs and Na(+)-bicarbonate co-transporters (NBCs). These membrane proteins consist of an amino-terminal cytosolic domain involved in protein interactions and a carboxyl-terminal membrane domain that carries out the transport function. Mutation of a conserved arginine residue (R298S) in the cytosolic domain of NBCe1 (SLC4A4) is linked to proximal renal tubular acidosis and results in impaired transport function, suggesting that the cytosolic domain plays a role in substrate permeation. Introduction of single and double mutations at the equivalent arginine (Arg(283)) and at an interacting glutamate (Glu(85)) in the cytosolic domain of human AE1 (cdAE1) had no effect on the cell surface expression or the transport activity of AE1 expressed in HEK-293 cells. In addition, the membrane domain of AE1 (mdAE1) efficiently mediated anion transport. A 2.1-Å resolution crystal structure of cdΔ54AE1 (residues 55-356 of cdAE1) lacking the amino-terminal and carboxyl-terminal disordered regions, produced at physiological pH, revealed an extensive hydrogen-bonded network involving Arg(283) and Glu(85). Mutations at these residues affected the pH-dependent conformational changes and stability of cdΔ54AE1. As these structural alterations did not impair functional expression of AE1, the cytosolic and membrane domains operate independently. A substrate access tunnel within the cytosolic domain is not present in AE1 and therefore is not an essential feature of the SLC4 family of bicarbonate transporters.
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Affiliation(s)
- Volodymyr Shnitsar
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jing Li
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Xuyao Li
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Charles Calmettes
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Arghya Basu
- Department of Biochemistry and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Joseph R Casey
- Department of Biochemistry and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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12
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Frumence E, Genetet S, Ripoche P, Iolascon A, Andolfo I, Le Van Kim C, Colin Y, Mouro-Chanteloup I, Lopez C. Rapid Cl−/HCO3−exchange kinetics of AE1 in HEK293 cells and hereditary stomatocytosis red blood cells. Am J Physiol Cell Physiol 2013; 305:C654-62. [DOI: 10.1152/ajpcell.00142.2013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anion exchanger 1 (AE1) or band 3 is a membrane protein responsible for the rapid exchange of chloride for bicarbonate across the red blood cell membrane. Nine mutations leading to single amino-acid substitutions in the transmembrane domain of AE1 are associated with dominant hereditary stomatocytosis, monovalent cation leaks, and reduced anion exchange activity. We set up a stopped-flow spectrofluorometry assay coupled with flow cytometry to investigate the anion transport and membrane expression characteristics of wild-type recombinant AE1 in HEK293 cells, using an inducible expression system. Likewise, study of three stomatocytosis-associated mutations (R730C, E758K, and G796R), allowed the validation of our method. Measurement of the rapid and specific chloride/bicarbonate exchange by surface expressed AE1 showed that E758K mutant was fully active compared with wild-type (WT) AE1, whereas R730C and G796R mutants were inactive, reinforcing previously reported data on other experimental models. Stopped-flow analysis of AE1 transport activity in red blood cell ghost preparations revealed a 50% reduction of G796R compared with WT AE1 corresponding to a loss of function of the G796R mutated protein, in accordance with the heterozygous status of the AE1 variant patients. In conclusion, stopped-flow led to measurement of rapid transport kinetics using the natural substrate for AE1 and, conjugated with flow cytometry, allowed a reliable correlation of chloride/bicarbonate exchange to surface expression of AE1, both in recombinant cells and ghosts and therefore a fine comparison of function between different stomatocytosis samples. This technical approach thus provides significant improvements in anion exchange analysis in red blood cells.
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Affiliation(s)
- Etienne Frumence
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
- Université de la Réunion, Saint-Denis, France; and
| | - Sandrine Genetet
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
| | - Pierre Ripoche
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
| | - Achille Iolascon
- Chair of Medical Genetics, Department of Molecular Medicine and Medical Biotechnologies, University Federico II, Naples, and CEINGE-Advanced Biotechnologies, Naples, Italy
| | - Immacolata Andolfo
- Chair of Medical Genetics, Department of Molecular Medicine and Medical Biotechnologies, University Federico II, Naples, and CEINGE-Advanced Biotechnologies, Naples, Italy
| | - Caroline Le Van Kim
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
| | - Yves Colin
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
| | - Isabelle Mouro-Chanteloup
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
| | - Claude Lopez
- Inserm U665, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, UMR-S665, Paris, France
- Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire d'Excellence GR-Ex., Paris, France
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