1
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Yadav A, Kumar D, Dwivedi M. Site-directed mutagenesis at the Glu78 in Ec-NhaA transporter impacting ion exchange: a biophysical study. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2024; 53:193-203. [PMID: 38647543 DOI: 10.1007/s00249-024-01709-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 03/24/2024] [Accepted: 03/27/2024] [Indexed: 04/25/2024]
Abstract
Na+/H+ antiporters facilitate the exchange of Na+ for H+ across the cytoplasmic membrane in prokaryotic and eukaryotic cells. These transporters are crucial to maintain the homeostasis of sodium ions, consequently pH, and volume of the cells. Therefore, sodium/proton antiporters are considered promising therapeutic targets in humans. The Na+/H+ antiporter in Escherichia coli (Ec-NhaA), a prototype of cation-proton antiporter (CPA) family, transports two protons and one sodium (or Li+) in opposite direction. Previous mutagenesis experiments on Ec-NhaA have proposed Asp164, Asp163, and Asp133 amino acids with the significant implication in functional and structural integrity and create site for ion-binding. However, the mechanism and the sites for the binding of the two protons remain unknown and controversial which could be critical for pH regulation. In this study, we have explored the role of Glu78 in the regulation of pH by Ec-NhaA. Although we have created various mutants, E78C has shown a considerable effect on the stoichiometry of NhaA and presented comparable phenotypes. The ITC experiment has shown the binding of ~ 5 protons in response to the transport of one lithium ion. The phenotype analysis on selective medium showed a significant expression compared to WT Ec-NhaA. This represents the importance of Glu78 in transporting the H+ across the membrane where a single mutation with Cys amino acid alters the number of H+ significantly maintaining the activity of the protein.
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Affiliation(s)
- Anuradha Yadav
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow, 226028, India
| | - Dinesh Kumar
- Center of Biomedical Research, SGPGIMS Campus, Lucknow, 226014, India
| | - Manish Dwivedi
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow, 226028, India.
- Research Cell, Amity University Uttar Pradesh, Lucknow, 226028, India.
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2
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Rimon A, Amartely H, Padan E. The crossing of two unwound transmembrane regions that is the hallmark of the NhaA structural fold is critical for antiporter activity. Sci Rep 2024; 14:5915. [PMID: 38467695 PMCID: PMC10928194 DOI: 10.1038/s41598-024-56425-3] [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: 12/06/2023] [Accepted: 03/06/2024] [Indexed: 03/13/2024] Open
Abstract
Cell pH and Na+ homeostasis requires Na+/H+ antiporters. The crystal structure of NhaA, the main Escherichia coli Na+/H+ antiporter, revealed a unique NhaA structural fold shared by prokaryotic and eukaryotic membrane proteins. Out of the 12 NhaA transmembrane segments (TMs), TMs III-V and X-XII are topologically inverted repeats with unwound TMs IV and XI forming the X shape characterizing the NhaA fold. We show that intramolecular cross-linking under oxidizing conditions of a NhaA mutant with two Cys replacements across the crossing (D133C-T340C) inhibits antiporter activity and impairs NhaA-dependent cell growth in high-salts. The affinity purified D133C-T340C protein binds Li+ (the Na+ surrogate substrate of NhaA) under reducing conditions. The cross-linking traps the antiporter in an outward-facing conformation, blocking the antiport cycle. As many secondary transporters are found to share the NhaA fold, including some involved in human diseases, our data have importance for both basic and clinical research.
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Affiliation(s)
- Abraham Rimon
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Jerusalem, Israel
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel
| | - Hadar Amartely
- Wolfson Center for Applied Structural Biology, Jerusalem, Israel
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel
| | - Etana Padan
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Jerusalem, Israel.
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel.
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3
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Luo S, Wang D, Zhang Z. Post-translational modification and mitochondrial function in Parkinson's disease. Front Mol Neurosci 2024; 16:1329554. [PMID: 38273938 PMCID: PMC10808367 DOI: 10.3389/fnmol.2023.1329554] [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: 10/29/2023] [Accepted: 12/21/2023] [Indexed: 01/27/2024] Open
Abstract
Parkinson's disease (PD) is the second most common neurodegenerative disease with currently no cure. Most PD cases are sporadic, and about 5-10% of PD cases present a monogenic inheritance pattern. Mutations in more than 20 genes are associated with genetic forms of PD. Mitochondrial dysfunction is considered a prominent player in PD pathogenesis. Post-translational modifications (PTMs) allow rapid switching of protein functions and therefore impact various cellular functions including those related to mitochondria. Among the PD-associated genes, Parkin, PINK1, and LRRK2 encode enzymes that directly involved in catalyzing PTM modifications of target proteins, while others like α-synuclein, FBXO7, HTRA2, VPS35, CHCHD2, and DJ-1, undergo substantial PTM modification, subsequently altering mitochondrial functions. Here, we summarize recent findings on major PTMs associated with PD-related proteins, as enzymes or substrates, that are shown to regulate important mitochondrial functions and discuss their involvement in PD pathogenesis. We will further highlight the significance of PTM-regulated mitochondrial functions in understanding PD etiology. Furthermore, we emphasize the potential for developing important biomarkers for PD through extensive research into PTMs.
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Affiliation(s)
- Shishi Luo
- Institute for Future Sciences, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Key Laboratory of Rare Pediatric Diseases, Ministry of Education, Hengyang, Hunan, China
- The Affiliated Changsha Central Hospital, Hengyang Medical School, University of South China, Changsha, Hunan, China
| | - Danling Wang
- Institute for Future Sciences, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Key Laboratory of Rare Pediatric Diseases, Ministry of Education, Hengyang, Hunan, China
- The Affiliated Changsha Central Hospital, Hengyang Medical School, University of South China, Changsha, Hunan, China
| | - Zhuohua Zhang
- Institute for Future Sciences, Hengyang Medical School, University of South China, Hengyang, Hunan, China
- Key Laboratory of Rare Pediatric Diseases, Ministry of Education, Hengyang, Hunan, China
- Institute of Molecular Precision Medicine, Xiangya Hospital, Key Laboratory of Molecular Precision Medicine of Hunan Province and Center for Medical Genetics, Hunan Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan, China
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4
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Lee CE. Genome architecture underlying salinity adaptation in the invasive copepod Eurytemora affinis species complex: A review. iScience 2023; 26:107851. [PMID: 37752947 PMCID: PMC10518491 DOI: 10.1016/j.isci.2023.107851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2023] Open
Abstract
With climate change, habitat salinity is shifting rapidly throughout the globe. In addition, many destructive freshwater invaders are recent immigrants from saline habitats. Recently, populations of the copepod Eurytemora affinis species complex have invaded freshwater habitats multiple times independently from saline estuaries on three continents. This review discusses features of this species complex that could enhance their evolutionary potential during rapid environmental change. Remarkably, across independent freshwater invasions, natural selection has repeatedly favored the same alleles far more than expected. This high degree of parallelism is surprising, given the expectation of nonparallel evolution for polygenic adaptation. Factors such as population structure and the genome architecture underlying critical traits under selection might help drive rapid adaptation and parallel evolution. Given the preponderance of saline-to-freshwater invasions and climate-induced salinity change, the principles found here could provide invaluable insights into mechanisms operating in other systems and the potential for adaptation in a changing planet.
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Affiliation(s)
- Carol Eunmi Lee
- Department of Integrative Biology, University of Wisconsin, 430 Lincoln Drive, Birge Hall, Madison, WI 53706, USA
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5
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Gardner CC, James PF. Na +/H + Exchangers (NHEs) in Mammalian Sperm: Essential Contributors to Male Fertility. Int J Mol Sci 2023; 24:14981. [PMID: 37834431 PMCID: PMC10573352 DOI: 10.3390/ijms241914981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/03/2023] [Accepted: 10/04/2023] [Indexed: 10/15/2023] Open
Abstract
Na+/H+ exchangers (NHEs) are known to be important regulators of pH in multiple intracellular compartments of eukaryotic cells. Sperm function is especially dependent on changes in pH and thus it has been postulated that NHEs play important roles in regulating the intracellular pH of these cells. For example, in order to achieve fertilization, mature sperm must maintain a basal pH in the male reproductive tract and then alkalize in response to specific signals in the female reproductive tract during the capacitation process. Eight NHE isoforms are expressed in mammalian testis/sperm: NHE1, NHE3, NHE5, NHE8, NHA1, NHA2, NHE10, and NHE11. These NHE isoforms are expressed at varying times during spermatogenesis and localize to different subcellular structures in developing and mature sperm where they contribute to multiple aspects of sperm physiology and male fertility including proper sperm development/morphogenesis, motility, capacitation, and the acrosome reaction. Previous work has provided evidence for NHE3, NHE8, NHA1, NHA2, and NHE10 being critical for male fertility in mice and NHE10 has recently been shown to be essential for male fertility in humans. In this article we review what is known about each NHE isoform expressed in mammalian sperm and discuss the physiological significance of each NHE isoform with respect to male fertility.
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Affiliation(s)
| | - Paul F. James
- Department of Biology, Miami University, Oxford, OH 45056, USA;
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6
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Yadava A, Bhuyan MMR, Mukherjee D, Kumar D, Dwivedi M. Phytomolecules as potential candidates to intervene the function of E. coli sodium-proton antiporters; Ec-NhaA. J Biomol Struct Dyn 2023; 41:15598-15609. [PMID: 36935099 DOI: 10.1080/07391102.2023.2191130] [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: 10/27/2022] [Accepted: 03/06/2023] [Indexed: 03/20/2023]
Abstract
Sodium-Proton antiporter, NhaA is a ubiquitous protein found in cytoplasmic membranes of all the prokaryotic and eukaryotic systems. These antiporters have been widely studied in E. coli and their homologs, observed in humans, are found to be crucial for various pathophysiological conditions, such as hypertension, cardiac diseases, blood pressure fluctuation etc. NhaA is responsible for the virulent properties of many pathogens like Vibrio cholerae, Yersinia pestis etc. In the present work, we have exploited in silico approaches to find lead phytomolecules that have the efficacy to interfere with the activities of sodium-proton antiporters in E. coli. A database of the plant-based natural bioactive compounds was used to screen 350 phytochemicals from various plant sources as potential ligands for the Ec-NhaA protein (PDB ID: 4ATV). Further interactions between Ec-NhaA and ligands were analyzed by AutoDock Vina and proposed 46 ligands with a significant affinity for NhaA where the binding energy range from -7.5 to -9.3 kcal/mol. Physiochemical characterization suggested 26 ligands with non-BBB permeability, good GI absorption and solubility. As a final step, MD simulation for more than 100 ns duration suggested Luteolin, Apigenin and Rhamnocitrin with the best affinity and showing potential stable interaction with the target protein. This study proposed the potential compounds of natural origin as an interfering agent against sodium-proton transport activity that may lead to affect the survival of various pathogenic bacteria.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Anuradha Yadava
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow Campus, Lucknow, India
| | - Md Mahfuzur Rahman Bhuyan
- Department of Biochemistry and Molecular Biology, Noakhali Science and Technology University, Noakhali, Bangladesh
| | | | - Dinesh Kumar
- Centre of Biomedical Research (CBMR), Lucknow, Uttar Pradesh, India
| | - Manish Dwivedi
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow Campus, Lucknow, India
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7
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Velázquez D, Průša V, Masrati G, Yariv E, Sychrova H, Ben‐Tal N, Zimmermannova O. Allosteric links between the hydrophilic N-terminus and transmembrane core of human Na + /H + antiporter NHA2. Protein Sci 2022; 31:e4460. [PMID: 36177733 PMCID: PMC9667825 DOI: 10.1002/pro.4460] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 09/16/2022] [Accepted: 09/25/2022] [Indexed: 12/13/2022]
Abstract
The human Na+ /H+ antiporter NHA2 (SLC9B2) transports Na+ or Li+ across the plasma membrane in exchange for protons, and is implicated in various pathologies. It is a 537 amino acids protein with an 82 residues long hydrophilic cytoplasmic N-terminus followed by a transmembrane part comprising 14 transmembrane helices. We optimized the functional expression of HsNHA2 in the plasma membrane of a salt-sensitive Saccharomyces cerevisiae strain and characterized in vivo a set of mutated or truncated versions of HsNHA2 in terms of their substrate specificity, transport activity, localization, and protein stability. We identified a highly conserved proline 246, located in the core of the protein, as being crucial for ion selectivity. The replacement of P246 with serine or threonine resulted in antiporters with altered substrate specificity that were not only highly active at acidic pH 4.0 (like the native antiporter), but also at neutral pH. P246T/S versions also exhibited increased resistance to the HsNHA2-specific inhibitor phloretin. We experimentally proved that a putative salt bridge between E215 and R432 is important for antiporter function, but also structural integrity. Truncations of the first 50-70 residues of the N-terminus doubled the transport activity of HsNHA2, while changes in the charge at positions E47, E56, K57, or K58 decreased the antiporter's transport activity. Thus, the hydrophilic N-terminal part of the protein appears to allosterically auto-inhibit cation transport of HsNHA2. Our data also show this in vivo approach to be useful for a rapid screening of SNP's effect on HsNHA2 activity.
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Affiliation(s)
- Diego Velázquez
- Laboratory of Membrane TransportInstitute of Physiology of the Czech Academy of SciencesPragueCzech Republic
| | - Vojtěch Průša
- Laboratory of Membrane TransportInstitute of Physiology of the Czech Academy of SciencesPragueCzech Republic
| | - Gal Masrati
- Department of Biochemistry and Molecular BiologyGeorge S. Wise Faculty of Life Sciences, Tel‐Aviv UniversityTel‐AvivIsrael
| | - Elon Yariv
- Department of Biochemistry and Molecular BiologyGeorge S. Wise Faculty of Life Sciences, Tel‐Aviv UniversityTel‐AvivIsrael
| | - Hana Sychrova
- Laboratory of Membrane TransportInstitute of Physiology of the Czech Academy of SciencesPragueCzech Republic
| | - Nir Ben‐Tal
- Department of Biochemistry and Molecular BiologyGeorge S. Wise Faculty of Life Sciences, Tel‐Aviv UniversityTel‐AvivIsrael
| | - Olga Zimmermannova
- Laboratory of Membrane TransportInstitute of Physiology of the Czech Academy of SciencesPragueCzech Republic
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8
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Anderegg MA, Gyimesi G, Ho TM, Hediger MA, Fuster DG. The Less Well-Known Little Brothers: The SLC9B/NHA Sodium Proton Exchanger Subfamily—Structure, Function, Regulation and Potential Drug-Target Approaches. Front Physiol 2022; 13:898508. [PMID: 35694410 PMCID: PMC9174904 DOI: 10.3389/fphys.2022.898508] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 05/04/2022] [Indexed: 12/15/2022] Open
Abstract
The SLC9 gene family encodes Na+/H+ exchangers (NHEs), a group of membrane transport proteins critically involved in the regulation of cytoplasmic and organellar pH, cell volume, as well as systemic acid-base and volume homeostasis. NHEs of the SLC9A subfamily (NHE 1–9) are well-known for their roles in human physiology and disease. Much less is known about the two members of the SLC9B subfamily, NHA1 and NHA2, which share higher similarity to prokaryotic NHEs than the SLC9A paralogs. NHA2 (also known as SLC9B2) is ubiquitously expressed and has recently been shown to participate in renal blood pressure and electrolyte regulation, insulin secretion and systemic glucose homeostasis. In addition, NHA2 has been proposed to contribute to the pathogenesis of polycystic kidney disease, the most common inherited kidney disease in humans. NHA1 (also known as SLC9B1) is mainly expressed in testis and is important for sperm motility and thus male fertility, but has not been associated with human disease thus far. In this review, we present a summary of the structure, function and regulation of expression of the SLC9B subfamily members, focusing primarily on the better-studied SLC9B paralog, NHA2. Furthermore, we will review the potential of the SLC9B subfamily as drug targets.
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Affiliation(s)
- Manuel A. Anderegg
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- *Correspondence: Manuel A. Anderegg,
| | - Gergely Gyimesi
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Membrane Transport Discovery Lab, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Tin Manh Ho
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Matthias A. Hediger
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Membrane Transport Discovery Lab, Department for BioMedical Research, University of Bern, Bern, Switzerland
| | - Daniel G. Fuster
- Department of Nephrology and Hypertension, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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9
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Matsuoka R, Fudim R, Jung S, Zhang C, Bazzone A, Chatzikyriakidou Y, Robinson CV, Nomura N, Iwata S, Landreh M, Orellana L, Beckstein O, Drew D. Structure, mechanism and lipid-mediated remodeling of the mammalian Na +/H + exchanger NHA2. Nat Struct Mol Biol 2022; 29:108-120. [PMID: 35173351 PMCID: PMC8850199 DOI: 10.1038/s41594-022-00738-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 12/14/2021] [Indexed: 11/09/2022]
Abstract
The Na+/H+ exchanger SLC9B2, also known as NHA2, correlates with the long-sought-after Na+/Li+ exchanger linked to the pathogenesis of diabetes mellitus and essential hypertension in humans. Despite the functional importance of NHA2, structural information and the molecular basis for its ion-exchange mechanism have been lacking. Here we report the cryo-EM structures of bison NHA2 in detergent and in nanodiscs, at 3.0 and 3.5 Å resolution, respectively. The bison NHA2 structure, together with solid-state membrane-based electrophysiology, establishes the molecular basis for electroneutral ion exchange. NHA2 consists of 14 transmembrane (TM) segments, rather than the 13 TMs previously observed in mammalian Na+/H+ exchangers (NHEs) and related bacterial antiporters. The additional N-terminal helix in NHA2 forms a unique homodimer interface with a large intracellular gap between the protomers, which closes in the presence of phosphoinositol lipids. We propose that the additional N-terminal helix has evolved as a lipid-mediated remodeling switch for the regulation of NHA2 activity.
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Affiliation(s)
- Rei Matsuoka
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Roman Fudim
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
| | - Sukkyeong Jung
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Chenou Zhang
- Center for Biological Physics, Department of Physics, Arizona State University, Tempe, AZ, USA
| | | | | | | | - Norimichi Nomura
- Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, Japan
| | - So Iwata
- Graduate School of Medicine, Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, Japan
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Laura Orellana
- Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Oliver Beckstein
- Center for Biological Physics, Department of Physics, Arizona State University, Tempe, AZ, USA.
| | - David Drew
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
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10
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Pizzagalli MD, Bensimon A, Superti‐Furga G. A guide to plasma membrane solute carrier proteins. FEBS J 2021; 288:2784-2835. [PMID: 32810346 PMCID: PMC8246967 DOI: 10.1111/febs.15531] [Citation(s) in RCA: 181] [Impact Index Per Article: 60.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 08/07/2020] [Accepted: 08/17/2020] [Indexed: 12/13/2022]
Abstract
This review aims to serve as an introduction to the solute carrier proteins (SLC) superfamily of transporter proteins and their roles in human cells. The SLC superfamily currently includes 458 transport proteins in 65 families that carry a wide variety of substances across cellular membranes. While members of this superfamily are found throughout cellular organelles, this review focuses on transporters expressed at the plasma membrane. At the cell surface, SLC proteins may be viewed as gatekeepers of the cellular milieu, dynamically responding to different metabolic states. With altered metabolism being one of the hallmarks of cancer, we also briefly review the roles that surface SLC proteins play in the development and progression of cancer through their influence on regulating metabolism and environmental conditions.
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Affiliation(s)
- Mattia D. Pizzagalli
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Ariel Bensimon
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
| | - Giulio Superti‐Furga
- CeMM, Research Center for Molecular Medicine of the Austrian Academy of SciencesViennaAustria
- Center for Physiology and PharmacologyMedical University of ViennaAustria
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11
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Quick M, Dwivedi M, Padan E. Insight into the direct interaction of Na + with NhaA and mechanistic implications. Sci Rep 2021; 11:7045. [PMID: 33782459 PMCID: PMC8007835 DOI: 10.1038/s41598-021-86318-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 03/05/2021] [Indexed: 11/21/2022] Open
Abstract
Na+/H+ antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life that are essential in cellular ion homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystals provided insight in the structure of this molecular machine. However, structural data revealing the composition of the binding site for Na+ (or its surrogate Li+) is missing, representing a bottleneck in our understanding of the correlation between the structure and function of NhaA. Here, by adapting the scintillation proximity assay (SPA) for direct determination of Na+ binding to NhaA, we revealed that (i) NhaA is well adapted as the main antiporter for Na+ homeostasis in Escherichia coli and possibly in other bacteria as the cytoplasmic Na+ concentration is similar to the Na+ binding affinity of NhaA, (ii) experimental conditions affect NhaA-mediated cation binding, (iii) in addition to Na+ and Li+, the halide Tl+ interacts with NhaA, (iv) whereas acidic pH inhibits maximum binding of Na+ to NhaA, partial Na+ binding by NhaA is independent of the pH, an important novel insight into the effect of pH on NhaA cation binding.
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Affiliation(s)
- Matthias Quick
- Department of Psychiatry and Center for Molecular Recognition, Columbia University Vagelos College of Physicians and Surgeons, and New York State Psychiatric Institute, New York, NY, 10032, USA.
| | - Manish Dwivedi
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel.,Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow, 226028, India
| | - Etana Padan
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel.
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12
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Posavi M, Gulisija D, Munro JB, Silva JC, Lee CE. Rapid evolution of genome-wide gene expression and plasticity during saline to freshwater invasions by the copepod Eurytemora affinis species complex. Mol Ecol 2020; 29:4835-4856. [PMID: 33047351 DOI: 10.1111/mec.15681] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 09/18/2020] [Accepted: 10/01/2020] [Indexed: 01/01/2023]
Abstract
Saline migrants into freshwater habitats constitute among the most destructive invaders in aquatic ecosystems throughout the globe. However, the evolutionary and physiological mechanisms underlying such habitat transitions remain poorly understood. To explore the mechanisms of freshwater adaptation and distinguish between adaptive (evolutionary) and acclimatory (plastic) responses to salinity change, we examined genome-wide patterns of gene expression between ancestral saline and derived freshwater populations of the Eurytemora affinis species complex, reared under two different common-garden conditions (0 versus 15 PSU). We found that evolutionary shifts in gene expression (between saline and freshwater inbred lines) showed far greater changes and were more widespread than acclimatory responses to salinity (0 versus 15 PSU). Most notably, 30-40 genes showing evolutionary shifts in gene expression across the salinity boundary were associated with ion transport function, with inorganic cation transmembrane transport forming the largest Gene Ontology category. Of particular interest was the sodium transporter, the Na+ /H+ antiporter (NHA) gene family, which was discovered in animals relatively recently. Thirty key ion regulatory genes, such as NHA paralogue #7, demonstrated concordant evolutionary and plastic shifts in gene expression, suggesting the evolution of ion transporter function and plasticity during rapid invasions into novel salinities. Moreover, freshwater invasions were associated with the evolution of reduced plasticity in the freshwater population, again for the same key ion transporters, consistent with the predicted evolution of canalization following adaptation to stressful conditions. Our results have important implications for understanding evolutionary and physiological mechanisms of range expansions by some of the most widespread invaders in aquatic habitats.
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Affiliation(s)
- Marijan Posavi
- Department of Integrative Biology, University of Wisconsin, Madison, WI, USA
| | - Davorka Gulisija
- Department of Biology, University of New Mexico, Albuquerque, NM, USA
| | - James B Munro
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Joana C Silva
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Carol Eunmi Lee
- Department of Integrative Biology, University of Wisconsin, Madison, WI, USA
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13
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Dwivedi M. Site-directed mutations reflecting functional and structural properties of Ec-NhaA. Biochimie 2020; 180:79-89. [PMID: 33129932 DOI: 10.1016/j.biochi.2020.10.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/21/2020] [Accepted: 10/27/2020] [Indexed: 11/20/2022]
Abstract
NhaA antiporters are secondary integral membrane protein critical for maintaining the Na+/H+ cell homeostasis, as a result, they regulate fundamental processes like cell volume and intracellular pH. Exploration of the structural and functional properties can assist to make them effective human drug targets and mechanisms of salt-resistance in plants. NhaA proteins are integrated into cytoplasmic and intracellular membranes, transport 2H+/Na + across the membrane by the canonical alternating access mechanism. There are mutagenesis studies have done on Ec-NhaA predicting residues crucial for function and structure. The unique NhaA structural fold is formed in the middle of the membrane by two transmembrane segments (TMs), TM IV and XI which cross each other creating a delicate electrostatically balanced environment for the binding of Na+/H+. Previously, Asp164, Asp163 and Asp133 residues have been proposed as crucial for Na+/Li + binding on the based on crystal structure and mutation-based studies. However, the pathway and the binding sites for the two protons are still elusive and debatable. This review will provide comprehensive details on various mutations constructed in Ec-NhaA by different research groups using site-directed or random mutagenesis techniques. The selected residues for mutations are located on the sites which are more suspected to have a crucial role in function and structure on NhaA. This information on the single platform would accelerate further studies on the structure-function relationship on NhaA as well as will facilitate to predict the role of Na+/H+ antiporters in human diseases.
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Affiliation(s)
- Manish Dwivedi
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Gomtinagar Ext., Lucknow, 226028, India.
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14
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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15
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Prasad H, Dang DK, Kondapalli KC, Natarajan N, Cebotaru V, Rao R. NHA2 promotes cyst development in an in vitro model of polycystic kidney disease. J Physiol 2019; 597:499-519. [PMID: 30242840 PMCID: PMC6332743 DOI: 10.1113/jp276796] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Accepted: 08/31/2018] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Significant and selective up-regulation of the Na+ /H+ exchanger NHA2 (SLC9B2) was observed in cysts of patients with autosomal dominant polycystic kidney disease. Using the MDCK cell model of cystogenesis, it was found that NHA2 increases cyst size. Silencing or pharmacological inhibition of NHA2 inhibits cyst formation in vitro. Polycystin-1 represses NHA2 expression via Ca2+ /NFAT signalling whereas the dominant negative membrane-anchored C-terminal fragment (PC1-MAT) increased NHA2 levels. Drugs (caffeine, theophylline) and hormones (vasopressin, aldosterone) known to exacerbate cysts elicit NHA2 expression. Taken together, the findings reveal NHA2 as a potential new player in salt and water homeostasis in the kidney and in the pathogenesis of polycystic kidney disease. ABSTRACT Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 and PKD2 encoding polycystin-1 (PC1) and polycystin-2 (PC2), respectively. The molecular pathways linking polycystins to cyst development in ADPKD are still unclear. Intracystic fluid secretion via ion transporters and channels plays a crucial role in cyst expansion in ADPKD. Unexpectedly, we observed significant and selective up-regulation of NHA2, a member of the SLC9B family of Na+ /H+ exchangers, that correlated with cyst size and disease severity in ADPKD patients. Using three-dimensional cultures of MDCK cells to model cystogenesis in vitro, we showed that ectopic expression of NHA2 is causal to increased cyst size. Induction of PC1 in MDCK cells inhibited NHA2 expression with concordant inhibition of Ca2+ influx through store-dependent and -independent pathways, whereas reciprocal activation of Ca2+ influx by the dominant negative membrane-anchored C-terminal tail fragment of PC1 elevated NHA2. We showed that NHA2 is a target of Ca2+ /NFAT signalling and is transcriptionally induced by methylxanthine drugs such as caffeine and theophylline, which are contraindicated in ADPKD patients. Finally, we observed robust induction of NHA2 by vasopressin, which is physiologically consistent with increased levels of circulating vasopressin and up-regulation of vasopressin V2 receptors in ADPKD. Our findings have mechanistic implications on the emerging use of vasopressin V2 receptor antagonists such as tolvaptan as safe and effective therapy for polycystic kidney disease and reveal a potential new regulator of transepithelial salt and water transport in the kidney.
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Affiliation(s)
- Hari Prasad
- Department of PhysiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
| | - Donna K. Dang
- Department of PhysiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
| | - Kalyan C. Kondapalli
- Department of PhysiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
| | - Niranjana Natarajan
- Department of PhysiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
| | - Valeriu Cebotaru
- Department of MedicineUniversity of Maryland School of MedicineBaltimoreMDUSA
| | - Rajini Rao
- Department of PhysiologyJohns Hopkins University School of MedicineBaltimoreMDUSA
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16
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Poynton HC, Hasenbein S, Benoit JB, Sepulveda MS, Poelchau MF, Hughes DST, Murali SC, Chen S, Glastad KM, Goodisman MAD, Werren JH, Vineis JH, Bowen JL, Friedrich M, Jones J, Robertson HM, Feyereisen R, Mechler-Hickson A, Mathers N, Lee CE, Colbourne JK, Biales A, Johnston JS, Wellborn GA, Rosendale AJ, Cridge AG, Munoz-Torres MC, Bain PA, Manny AR, Major KM, Lambert FN, Vulpe CD, Tuck P, Blalock BJ, Lin YY, Smith ME, Ochoa-Acuña H, Chen MJM, Childers CP, Qu J, Dugan S, Lee SL, Chao H, Dinh H, Han Y, Doddapaneni H, Worley KC, Muzny DM, Gibbs RA, Richards S. The Toxicogenome of Hyalella azteca: A Model for Sediment Ecotoxicology and Evolutionary Toxicology. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:6009-6022. [PMID: 29634279 DOI: 10.15482/usda.adc/1415994] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Hyalella azteca is a cryptic species complex of epibenthic amphipods of interest to ecotoxicology and evolutionary biology. It is the primary crustacean used in North America for sediment toxicity testing and an emerging model for molecular ecotoxicology. To provide molecular resources for sediment quality assessments and evolutionary studies, we sequenced, assembled, and annotated the genome of the H. azteca U.S. Lab Strain. The genome quality and completeness is comparable with other ecotoxicological model species. Through targeted investigation and use of gene expression data sets of H. azteca exposed to pesticides, metals, and other emerging contaminants, we annotated and characterized the major gene families involved in sequestration, detoxification, oxidative stress, and toxicant response. Our results revealed gene loss related to light sensing, but a large expansion in chemoreceptors, likely underlying sensory shifts necessary in their low light habitats. Gene family expansions were also noted for cytochrome P450 genes, cuticle proteins, ion transporters, and include recent gene duplications in the metal sequestration protein, metallothionein. Mapping of differentially expressed transcripts to the genome significantly increased the ability to functionally annotate toxicant responsive genes. The H. azteca genome will greatly facilitate development of genomic tools for environmental assessments and promote an understanding of how evolution shapes toxicological pathways with implications for environmental and human health.
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Affiliation(s)
- Helen C Poynton
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Simone Hasenbein
- Aquatic Systems Biology Unit , Technical University of Munich , D-85354 Freising , Germany
| | - Joshua B Benoit
- Department of Biological Sciences , University of Cincinnati , Cincinnati , Ohio 45221 United States
| | - Maria S Sepulveda
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
| | - Monica F Poelchau
- Agricultural Research Service, National Agricultural Library , U.S. Department of Agriculture , Beltsville , Maryland 20705 United States
| | - Daniel S T Hughes
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shwetha C Murali
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shuai Chen
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
- OmicSoft Corporation, Cary , North Carolina 27513 United States
| | - Karl M Glastad
- Perelman School of Medicine , University of Pennsylvania , Philadelphia , Pennsylvania 19104 United States
| | - Michael A D Goodisman
- School of Biological Sciences , Georgia Institute of Technology , Atlanta , Georgia 30332 United States
| | - John H Werren
- Biology Department , University of Rochester , Rochester , New York 14627 United States
| | - Joseph H Vineis
- Department of Marine and Environmental Sciences, Marine Science Center , Northeastern University , Nahant , Massachusetts 01908 United States
| | - Jennifer L Bowen
- Department of Marine and Environmental Sciences, Marine Science Center , Northeastern University , Nahant , Massachusetts 01908 United States
| | - Markus Friedrich
- Department of Biological Sciences , Wayne State University , Detroit Michigan 48202 United States
| | - Jeffery Jones
- Department of Biological Sciences , Wayne State University , Detroit Michigan 48202 United States
| | - Hugh M Robertson
- Department of Entomology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 United States
| | - René Feyereisen
- Department of Plant and Environmental Sciences , University of Copenhagen , DK-1871 Frederiksberg , Denmark
| | - Alexandra Mechler-Hickson
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - Nicholas Mathers
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - Carol Eunmi Lee
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - John K Colbourne
- School of Biosciences , University of Birmingham , Birmingham B15 2TT U.K
| | - Adam Biales
- National Exposure Research Laboratory , United States Environmental Protection Agency , Cincinnati , Ohio 45268 United States
| | - J Spencer Johnston
- Department of Entomology , Texas A&M University , College Station , Texas 77843 United States
| | - Gary A Wellborn
- Department of Biology , University of Oklahoma , Norman , Oklahoma 73019 United States
| | - Andrew J Rosendale
- Department of Biological Sciences , University of Cincinnati , Cincinnati , Ohio 45221 United States
| | - Andrew G Cridge
- Laboratory for Evolution and Development, Department of Biochemistry , University of Otago , Dunedin , 9054 New Zealand
| | - Monica C Munoz-Torres
- Environmental Genomics and Systems Biology Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 United States
| | - Peter A Bain
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Urrbrae SA 5064 Australia
| | - Austin R Manny
- Department of Microbiology & Cell Science , University of Florida , Gainesville , Florida 32611 United States
| | - Kaley M Major
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Faith N Lambert
- Center for Environmental and Human Toxicology, Department of Physiological Sciences , University of Florida , Gainesville , Florida 32611 United States
| | - Chris D Vulpe
- Center for Environmental and Human Toxicology, Department of Physiological Sciences , University of Florida , Gainesville , Florida 32611 United States
| | - Padrig Tuck
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Bonnie J Blalock
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Yu-Yu Lin
- Graduate Institute of Biomedical Electronics and Bioinformatics , National Taiwan University , Taipei , 10617 Taiwan
| | - Mark E Smith
- McConnell Group, Cincinnati , Ohio 45268 , United States
| | - Hugo Ochoa-Acuña
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
| | - Mei-Ju May Chen
- Graduate Institute of Biomedical Electronics and Bioinformatics , National Taiwan University , Taipei , 10617 Taiwan
| | - Christopher P Childers
- Agricultural Research Service, National Agricultural Library , U.S. Department of Agriculture , Beltsville , Maryland 20705 United States
| | - Jiaxin Qu
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shannon Dugan
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Sandra L Lee
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Hsu Chao
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Huyen Dinh
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Yi Han
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | | | - Kim C Worley
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
- Department of Molecular and Human Genetics , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Donna M Muzny
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Richard A Gibbs
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Stephen Richards
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
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17
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Poynton HC, Hasenbein S, Benoit JB, Sepulveda MS, Poelchau MF, Hughes DST, Murali SC, Chen S, Glastad KM, Goodisman MAD, Werren JH, Vineis JH, Bowen JL, Friedrich M, Jones J, Robertson HM, Feyereisen R, Mechler-Hickson A, Mathers N, Lee CE, Colbourne JK, Biales A, Johnston JS, Wellborn GA, Rosendale AJ, Cridge AG, Munoz-Torres MC, Bain PA, Manny AR, Major KM, Lambert FN, Vulpe CD, Tuck P, Blalock BJ, Lin YY, Smith ME, Ochoa-Acuña H, Chen MJM, Childers CP, Qu J, Dugan S, Lee SL, Chao H, Dinh H, Han Y, Doddapaneni H, Worley KC, Muzny DM, Gibbs RA, Richards S. The Toxicogenome of Hyalella azteca: A Model for Sediment Ecotoxicology and Evolutionary Toxicology. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:6009-6022. [PMID: 29634279 PMCID: PMC6091588 DOI: 10.1021/acs.est.8b00837] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Hyalella azteca is a cryptic species complex of epibenthic amphipods of interest to ecotoxicology and evolutionary biology. It is the primary crustacean used in North America for sediment toxicity testing and an emerging model for molecular ecotoxicology. To provide molecular resources for sediment quality assessments and evolutionary studies, we sequenced, assembled, and annotated the genome of the H. azteca U.S. Lab Strain. The genome quality and completeness is comparable with other ecotoxicological model species. Through targeted investigation and use of gene expression data sets of H. azteca exposed to pesticides, metals, and other emerging contaminants, we annotated and characterized the major gene families involved in sequestration, detoxification, oxidative stress, and toxicant response. Our results revealed gene loss related to light sensing, but a large expansion in chemoreceptors, likely underlying sensory shifts necessary in their low light habitats. Gene family expansions were also noted for cytochrome P450 genes, cuticle proteins, ion transporters, and include recent gene duplications in the metal sequestration protein, metallothionein. Mapping of differentially expressed transcripts to the genome significantly increased the ability to functionally annotate toxicant responsive genes. The H. azteca genome will greatly facilitate development of genomic tools for environmental assessments and promote an understanding of how evolution shapes toxicological pathways with implications for environmental and human health.
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Affiliation(s)
- Helen C Poynton
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Simone Hasenbein
- Aquatic Systems Biology Unit , Technical University of Munich , D-85354 Freising , Germany
| | - Joshua B Benoit
- Department of Biological Sciences , University of Cincinnati , Cincinnati , Ohio 45221 United States
| | - Maria S Sepulveda
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
| | - Monica F Poelchau
- Agricultural Research Service, National Agricultural Library , U.S. Department of Agriculture , Beltsville , Maryland 20705 United States
| | - Daniel S T Hughes
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shwetha C Murali
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shuai Chen
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
- OmicSoft Corporation, Cary , North Carolina 27513 United States
| | - Karl M Glastad
- Perelman School of Medicine , University of Pennsylvania , Philadelphia , Pennsylvania 19104 United States
| | - Michael A D Goodisman
- School of Biological Sciences , Georgia Institute of Technology , Atlanta , Georgia 30332 United States
| | - John H Werren
- Biology Department , University of Rochester , Rochester , New York 14627 United States
| | - Joseph H Vineis
- Department of Marine and Environmental Sciences, Marine Science Center , Northeastern University , Nahant , Massachusetts 01908 United States
| | - Jennifer L Bowen
- Department of Marine and Environmental Sciences, Marine Science Center , Northeastern University , Nahant , Massachusetts 01908 United States
| | - Markus Friedrich
- Department of Biological Sciences , Wayne State University , Detroit Michigan 48202 United States
| | - Jeffery Jones
- Department of Biological Sciences , Wayne State University , Detroit Michigan 48202 United States
| | - Hugh M Robertson
- Department of Entomology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 United States
| | - René Feyereisen
- Department of Plant and Environmental Sciences , University of Copenhagen , DK-1871 Frederiksberg , Denmark
| | - Alexandra Mechler-Hickson
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - Nicholas Mathers
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - Carol Eunmi Lee
- Center of Rapid Evolution (CORE) and Department of Integrative Biology , University of Wisconsin , Madison , Wisconsin 53706 United States
| | - John K Colbourne
- School of Biosciences , University of Birmingham , Birmingham B15 2TT U.K
| | - Adam Biales
- National Exposure Research Laboratory , United States Environmental Protection Agency , Cincinnati , Ohio 45268 United States
| | - J Spencer Johnston
- Department of Entomology , Texas A&M University , College Station , Texas 77843 United States
| | - Gary A Wellborn
- Department of Biology , University of Oklahoma , Norman , Oklahoma 73019 United States
| | - Andrew J Rosendale
- Department of Biological Sciences , University of Cincinnati , Cincinnati , Ohio 45221 United States
| | - Andrew G Cridge
- Laboratory for Evolution and Development, Department of Biochemistry , University of Otago , Dunedin , 9054 New Zealand
| | - Monica C Munoz-Torres
- Environmental Genomics and Systems Biology Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 United States
| | - Peter A Bain
- Commonwealth Scientific and Industrial Research Organisation (CSIRO), Urrbrae SA 5064 Australia
| | - Austin R Manny
- Department of Microbiology & Cell Science , University of Florida , Gainesville , Florida 32611 United States
| | - Kaley M Major
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Faith N Lambert
- Center for Environmental and Human Toxicology, Department of Physiological Sciences , University of Florida , Gainesville , Florida 32611 United States
| | - Chris D Vulpe
- Center for Environmental and Human Toxicology, Department of Physiological Sciences , University of Florida , Gainesville , Florida 32611 United States
| | - Padrig Tuck
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Bonnie J Blalock
- School for the Environment , University of Massachusetts Boston , Boston , Massachusetts 02125 United States
| | - Yu-Yu Lin
- Graduate Institute of Biomedical Electronics and Bioinformatics , National Taiwan University , Taipei , 10617 Taiwan
| | - Mark E Smith
- McConnell Group, Cincinnati , Ohio 45268 , United States
| | - Hugo Ochoa-Acuña
- Forestry and Natural Resources , Purdue University , West Lafayette , Indiana 47907 United States
| | - Mei-Ju May Chen
- Graduate Institute of Biomedical Electronics and Bioinformatics , National Taiwan University , Taipei , 10617 Taiwan
| | - Christopher P Childers
- Agricultural Research Service, National Agricultural Library , U.S. Department of Agriculture , Beltsville , Maryland 20705 United States
| | - Jiaxin Qu
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Shannon Dugan
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Sandra L Lee
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Hsu Chao
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Huyen Dinh
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Yi Han
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | | | - Kim C Worley
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
- Department of Molecular and Human Genetics , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Donna M Muzny
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Richard A Gibbs
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
| | - Stephen Richards
- Human Genome Sequencing Center , Baylor College of Medicine , Houston , Texas 77030 United States
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18
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Xu H, Ghishan FK, Kiela PR. SLC9 Gene Family: Function, Expression, and Regulation. Compr Physiol 2018; 8:555-583. [PMID: 29687889 DOI: 10.1002/cphy.c170027] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Slc9 family of Na+ /H+ exchangers (NHEs) plays a critical role in electroneutral exchange of Na+ and H+ in the mammalian intestine as well as other absorptive and secretory epithelia of digestive organs. These transport proteins contribute to the transepithelial Na+ and water absorption, intracellular pH and cellular volume regulation as well as the electrolyte, acid-base, and fluid volume homeostasis at the systemic level. They also influence the function of other membrane transport mechanisms, affect cellular proliferation and apoptosis as well as cell migration, adherence to the extracellular matrix, and tissue repair. Additionally, they modulate the extracellular milieu to facilitate other nutrient absorption and to regulate the intestinal microbial microenvironment. Na+ /H+ exchange is inhibited in selected gastrointestinal diseases, either by intrinsic factors (e.g., bile acids, inflammatory mediators) or infectious agents and associated bacterial toxins. Disrupted NHE activity may contribute not only to local and systemic electrolyte imbalance but also to the disease severity via multiple mechanisms. In this review, we describe the cation proton antiporter superfamily of Na+ /H+ exchangers with a particular emphasis on the eight SLC9A isoforms found in the digestive tract, followed by a more integrative description in their roles in each of the digestive organs. We discuss regulatory mechanisms that determine the function of Na+ /H+ exchangers as pertinent to the digestive tract, their regulation in pathological states of the digestive organs, and reciprocally, the contribution of dysregulated Na+ /H+ exchange to the disease pathogenesis and progression. © 2018 American Physiological Society. Compr Physiol 8:555-583, 2018.
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Affiliation(s)
- Hua Xu
- Department of Pediatrics, Steele Children's Research Center, University of Arizona, Tucson, Arizona, USA
| | - Fayez K Ghishan
- Department of Pediatrics, Steele Children's Research Center, University of Arizona, Tucson, Arizona, USA
| | - Pawel R Kiela
- Department of Pediatrics, Steele Children's Research Center, University of Arizona, Tucson, Arizona, USA.,Department of Immunobiology, University of Arizona, Tucson, Arizona, USA
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19
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Huang X, Anderle P, Hostettler L, Baumann MU, Surbek DV, Ontsouka EC, Albrecht C. Identification of placental nutrient transporters associated with intrauterine growth restriction and pre-eclampsia. BMC Genomics 2018; 19:173. [PMID: 29499643 PMCID: PMC5833046 DOI: 10.1186/s12864-018-4518-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 01/31/2018] [Indexed: 12/17/2022] Open
Abstract
Background Gestational disorders such as intrauterine growth restriction (IUGR) and pre-eclampsia (PE) are main causes of poor perinatal outcomes worldwide. Both diseases are related with impaired materno-fetal nutrient transfer, but the crucial transport mechanisms underlying IUGR and PE are not fully elucidated. In this study, we aimed to identify membrane transporters highly associated with transplacental nutrient deficiencies in IUGR/PE. Results In silico analyses on the identification of differentially expressed nutrient transporters were conducted using seven eligible microarray datasets (from Gene Expression Omnibus), encompassing control and IUGR/PE placental samples. Thereby 46 out of 434 genes were identified as potentially interesting targets. They are involved in the fetal provision with amino acids, carbohydrates, lipids, vitamins and microelements. Targets of interest were clustered into a substrate-specific interaction network by using Search Tool for the Retrieval of Interacting Genes. The subsequent wet-lab validation was performed using quantitative RT-PCR on placentas from clinically well-characterized IUGR/PE patients (IUGR, n = 8; PE, n = 5; PE+IUGR, n = 10) and controls (term, n = 13; preterm, n = 7), followed by 2D-hierarchical heatmap generation. Statistical evaluation using Kruskal-Wallis tests was then applied to detect significantly different expression patterns, while scatter plot analysis indicated which transporters were predominantly influenced by IUGR or PE, or equally affected by both diseases. Identified by both methods, three overlapping targets, SLC7A7, SLC38A5 (amino acid transporters), and ABCA1 (cholesterol transporter), were further investigated at the protein level by western blotting. Protein analyses in total placental tissue lysates and membrane fractions isolated from disease and control placentas indicated an altered functional activity of those three nutrient transporters in IUGR/PE. Conclusions Combining bioinformatic analysis, molecular biological experiments and mathematical diagramming, this study has demonstrated systematic alterations of nutrient transporter expressions in IUGR/PE. Among 46 initially targeted transporters, three significantly regulated genes were further investigated based on the severity and the disease specificity for IUGR and PE. Confirmed by mRNA and protein expression, the amino acid transporters SLC7A7 and SLC38A5 showed marked differences between controls and IUGR/PE and were regulated by both diseases. In contrast, ABCA1 may play an exclusive role in the development of PE. Electronic supplementary material The online version of this article (10.1186/s12864-018-4518-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Xiao Huang
- Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland.,Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Pascale Anderle
- Swiss Institute of Bioinformatics and HSeT Foundation, Lausanne, Switzerland.,Sitem-insel AG, Bern, Switzerland
| | - Lu Hostettler
- Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Marc U Baumann
- Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland.,Department of Obstetrics and Gynaecology, University Hospital, University of Bern, Bern, Switzerland
| | - Daniel V Surbek
- Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland.,Department of Obstetrics and Gynaecology, University Hospital, University of Bern, Bern, Switzerland
| | - Edgar C Ontsouka
- Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland.,Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Christiane Albrecht
- Swiss National Centre of Competence in Research, NCCR TransCure, University of Bern, Bern, Switzerland. .,Institute of Biochemistry and Molecular Medicine, Faculty of Medicine, University of Bern, Bern, Switzerland.
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20
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Călinescu O, Dwivedi M, Patiño-Ruiz M, Padan E, Fendler K. Lysine 300 is essential for stability but not for electrogenic transport of the Escherichia coli NhaA Na +/H + antiporter. J Biol Chem 2017; 292:7932-7941. [PMID: 28330875 PMCID: PMC5427271 DOI: 10.1074/jbc.m117.778175] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/09/2017] [Indexed: 11/06/2022] Open
Abstract
Na+/H+ antiporters are located in the cytoplasmic and intracellular membranes and play crucial roles in regulating intracellular pH, Na+, and volume. The NhaA antiporter of Escherichia coli is the best studied member of the Na+/H+ exchanger family and a model system for all related Na+/H+ exchangers, including eukaryotic representatives. Several amino acid residues are important for the transport activity of NhaA, including Lys-300, a residue that has recently been proposed to carry one of the two H+ ions that NhaA exchanges for one Na+ ion during one transport cycle. Here, we sought to characterize the effects of mutating Lys-300 of NhaA to amino acid residues containing side chains of different polarity and length (i.e. Ala, Arg, Cys, His, Glu, and Leu) on transporter stability and function. Salt resistance assays, acridine-orange fluorescence dequenching, solid supported membrane-based electrophysiology, and differential scanning fluorometry were used to characterize Na+ and H+ transport, charge translocation, and thermal stability of the different variants. These studies revealed that NhaA could still perform electrogenic Na+/H+ exchange even in the absence of a protonatable residue at the Lys-300 position. However, all mutants displayed lower thermal stability and reduced ion transport activity compared with the wild-type enzyme, indicating the critical importance of Lys-300 for optimal NhaA structural stability and function. On the basis of these experimental data, we propose a tentative mechanism integrating the functional and structural role of Lys-300.
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Affiliation(s)
- Octavian Călinescu
- From the Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
- the "Carol Davila" University of Medicine and Pharmacy, 050474 Bucharest, Romania, and
| | - Manish Dwivedi
- the Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Miyer Patiño-Ruiz
- From the Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Etana Padan
- the Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Klaus Fendler
- From the Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany,
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21
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Dissecting the proton transport pathway in electrogenic Na +/H + antiporters. Proc Natl Acad Sci U S A 2017; 114:E1101-E1110. [PMID: 28154142 DOI: 10.1073/pnas.1614521114] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sodium/proton exchangers of the SLC9 family mediate the transport of protons in exchange for sodium to help regulate intracellular pH, sodium levels, and cell volume. In electrogenic Na+/H+ antiporters, it has been assumed that two ion-binding aspartate residues transport the two protons that are later exchanged for one sodium ion. However, here we show that we can switch the antiport activity of the bacterial Na+/H+ antiporter NapA from being electrogenic to electroneutral by the mutation of a single lysine residue (K305). Electroneutral lysine mutants show similar ion affinities when driven by [Formula: see text]pH, but no longer respond to either an electrochemical potential ([Formula: see text]) or could generate one when driven by ion gradients. We further show that the exchange activity of the human Na+/H+ exchanger NHA2 (SLC9B2) is electroneutral, despite harboring the two conserved aspartic acid residues found in NapA and other bacterial homologues. Consistently, the equivalent residue to K305 in human NHA2 has been replaced with arginine, which is a mutation that makes NapA electroneutral. We conclude that a transmembrane embedded lysine residue is essential for electrogenic transport in Na+/H+ antiporters.
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22
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NHA2 is expressed in distal nephron and regulated by dietary sodium. J Physiol Biochem 2016; 73:199-205. [PMID: 27909897 DOI: 10.1007/s13105-016-0539-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 11/22/2016] [Indexed: 01/02/2023]
Abstract
Increased renal reabsorption of sodium is a significant risk factor in hypertension. An established clinical marker for essential hypertension is elevated sodium lithium countertransport (SLC) activity. NHA2 is a newly identified Na+(Li+)/H+ antiporter with potential genetic links to hypertension, which has been shown to mediate SLC activity and H+-coupled Na+(Li+) efflux in kidney-derived MDCK cells. To evaluate a putative role in sodium homeostasis, we determined the effect of dietary salt on NHA2. In murine kidney sections, NHA2 localized apically to distal convoluted (both DCT1 and 2) and connecting tubules, partially overlapping in distribution with V-ATPase, AQP2, and NCC1 transporters. Mice fed a diet high in sodium chloride showed elevated transcripts and expression of NHA2 protein. We propose a model in which NHA2 plays a dual role in salt reabsorption or secretion, depending on the coupling ion (sodium or protons). The identified novel regulation of Na+/H+ antiporter in the kidney suggests new roles in salt homeostasis and disease.
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23
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The Ec-NhaA antiporter switches from antagonistic to synergistic antiport upon a single point mutation. Sci Rep 2016; 6:23339. [PMID: 27021484 PMCID: PMC4810432 DOI: 10.1038/srep23339] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 03/04/2016] [Indexed: 12/14/2022] Open
Abstract
The Na+, Li+/H+ antiporter of Escherichia coli (Ec-NhaA) maintains pH, Na+ homeostasis in enterobacteria. We used isothermal titration calorimetry to perform a detailed thermodynamic analysis of Li+ binding to Ec-NhaA and several of its mutants. We found that, in line with the canonical alternative access mechanistic model of secondary transporters, Li+/H+ binding to the antiporter is antagonistically coupled. Binding of Li+ displaces 2 H+ from the binding site. The process is enthalpically driven, the enthalpic gain just compensating for an entropic loss and the buffer-associated enthalpic changes dominate the overall free-energy change. Li+ binding, H+ release and antiporter activity were all affected to the same extent by mutations in the Li+ binding site (D163E, D163N, D164N, D164E), while D133C changed the H+/Li+ stoichiometry to 4. Most striking, however, was the mutation, A167P, which converted the Ec-NhaA antagonistic binding into synergistic binding which is only known to occur in Cl−/H+ antiporter.
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24
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Sodium-Proton (Na+/H+) Antiporters: Properties and Roles in Health and Disease. Met Ions Life Sci 2016; 16:391-458. [DOI: 10.1007/978-3-319-21756-7_12] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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25
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26
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NhaA antiporter functions using 10 helices, and an additional 2 contribute to assembly/stability. Proc Natl Acad Sci U S A 2015; 112:E5575-82. [PMID: 26417087 DOI: 10.1073/pnas.1510964112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The Escherichia coli Na(+)/H(+) antiporter (Ec-NhaA) is the best-characterized of all pH-regulated Na(+)/H(+) exchangers that control cellular Na(+) and H(+) homeostasis. Ec-NhaA has 12 helices, 2 of which (VI and VII) are absent from other antiporters that share the Ec-NhaA structural fold. This α-hairpin is located in the dimer interface of the Ec-NhaA homodimer together with a β-sheet. Here we examine computationally and experimentally the role of the α-hairpin in the stability, dimerization, transport, and pH regulation of Ec-NhaA. Evolutionary analysis (ConSurf) indicates that the VI-VII helical hairpin is much less conserved than the remaining transmembrane region. Moreover, normal mode analysis also shows that intact NhaA and a variant, deleted of the α-hairpin, share similar dynamics, suggesting that the structure may be dispensable. Thus, two truncated Ec-NhaA mutants were constructed, one deleted of the α-hairpin and another also lacking the β-sheet. The mutants were studied at physiological pH in the membrane and in detergent micelles. The findings demonstrate that the truncated mutants retain significant activity and regulatory properties but are defective in the assembly/stability of the Ec-NhaA dimer.
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27
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Transport proteins NHA1 and NHA2 are essential for survival, but have distinct transport modalities. Proc Natl Acad Sci U S A 2015; 112:11720-5. [PMID: 26324901 DOI: 10.1073/pnas.1508031112] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The cation/proton antiporter (CPA) family includes the well-known sodium/proton exchanger (NHE; SLC9A) family of Na(+)/H(+) exchangers, and the more recently discovered and less well understood CPA2s (SLC9B), found widely in living organisms. In Drosophila, as in humans, they are represented by two genes, Nha1 (Slc9b1) and Nha2 (Slc9b2), which are enriched and functionally significant in renal tubules. The importance of their role in organismal survival has not been investigated in animals, however. Here we show that single RNAi knockdowns of either Nha1 or Nha2 reduce survival and in combination are lethal. Knockdown of either gene alone results in up-regulation of the other, suggesting functional complementation of the two genes. Under salt stress, knockdown of either gene decreases survival, demonstrating a key role for the CPA2 family in ion homeostasis. This is specific to Na(+) stress; survival on K(+) intoxication is not affected by sodium/hydrogen antiporter (NHA) knockdown. A direct functional assay in Xenopus oocytes shows that Nha2 acts as a Na(+)/H(+) exchanger. In contrast, Nha1 expressed in Xenopus oocytes shows strong Cl(-) conductance and acts as a H(+)-Cl(-) cotransporter. The activity of Nha1 is inhibited by chloride-binding competitors 4,4'-diiso-thiocyano-2,2'-disulfonic acid stilbene and 4,4'-dibenzamido-2,2'-stilbenedisulphonate. Salt stress induces a massive up-regulation of NHA gene expression not in the major osmoregulatory tissues of the alimentary canal, but in the crop, cuticle, and associated tissues. Thus, it is necessary to revise the classical view of the coordination of different tissues in the coordination of the response to osmoregulatory stress.
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Functional and structural dynamics of NhaA, a prototype for Na(+) and H(+) antiporters, which are responsible for Na(+) and H(+) homeostasis in cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:1047-62. [PMID: 24361841 DOI: 10.1016/j.bbabio.2013.12.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 12/09/2013] [Accepted: 12/13/2013] [Indexed: 01/14/2023]
Abstract
The crystal structure of down-regulated NhaA crystallized at acidic pH4 [21] has provided the first structural insights into the antiport mechanism and pH regulation of a Na(+)/H(+) antiporter [22]. On the basis of the NhaA crystal structure [21] and experimental data (reviewed in [2,22,38] we have suggested that NhaA is organized into two functional regions: (i) a cluster of amino acids responsible for pH regulation (ii) a catalytic region at the middle of the TM IV/XI assembly, with its unique antiparallel unfolded regions that cross each other forming a delicate electrostatic balance in the middle of the membrane. This unique structure contributes to the cation binding site and allows the rapid conformational changes expected for NhaA. Extended chains interrupting helices appear now a common feature for ion binding in transporters. However the NhaA fold is unique and shared by ASBTNM [30] and NapA [29]. Computation [13], electrophysiology [69] combined with biochemistry [33,47] have provided intriguing models for the mechanism of NhaA. However, the conformational changes and the residues involved have not yet been fully identified. Another issue which is still enigma is how energy is transduced "in this 'nano-machine.'" We expect that an integrative approach will reveal the residues that are crucial for NhaA activity and regulation, as well as elucidate the pHand ligand-induced conformational changes and their dynamics. Ultimately, integrative results will shed light on the mechanism of activity and pH regulation of NhaA, a prototype of the CPA2 family of transporters. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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29
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Shmukler BE, Hsu A, Alves J, Trudel M, Rust MB, Hubner CA, Rivera A, Alper SL. N-ethylmaleimide activates a Cl(-)-independent component of K(+) flux in mouse erythrocytes. Blood Cells Mol Dis 2013; 51:9-16. [PMID: 23481459 PMCID: PMC3646938 DOI: 10.1016/j.bcmd.2013.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 02/04/2013] [Indexed: 11/17/2022]
Abstract
The K-Cl cotransporters (KCCs) of mouse erythrocytes exhibit higher basal activity than those of human erythrocytes, but are similarly activated by cell swelling, by hypertonic urea, and by staurosporine. However, the dramatic stimulation of human erythroid KCCs by N-ethylmaleimide (NEM) is obscured in mouse erythrocytes by a prominent NEM-stimulated K(+) efflux that lacks Cl(-)-dependence. The NEM-sensitivity of Cl(-)-independent K(+) efflux of mouse erythrocytes is lower than that of KCC. The genetically engineered absence of the K-Cl cotransporters KCC3 and KCC1 from mouse erythrocytes does not modify Cl(-)-independent K(+) efflux. Mouse erythrocytes genetically devoid of the Gardos channel KCNN4 show increased NEM-sensitivity of both Cl(-)-independent K(+) efflux and K-Cl cotransport. The increased NEM-sensitivity and stimulation magnitude of Cl(-)-independent K(+) efflux in mouse erythrocytes expressing transgenic hypersickling human hemoglobin SAD (HbSAD) are independent of the presence of KCC3 and KCC1, but absence of KCNN4 reduces the stimulatory effect of HbSAD. NEM-stimulated Cl(-)-independent K(+) efflux of mouse red cells is insensitive to ouabain and bumetanide, but partially inhibited by chloroquine, barium, and amiloride. The NEM-stimulated activity is modestly reduced at pH6.0 but not significantly altered at pH8.0, and is abolished at 0°C. Although the molecular identity of this little-studied K(+) efflux pathway of mouse erythrocytes remains unknown, its potential role in the pathophysiology of sickle red cell dehydration will be important for the extrapolation of studies in mouse models of sickle cell disease to our understanding of humans with sickle cell anemia.
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Affiliation(s)
- Boris E. Shmukler
- Divisions of Nephrology and Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | - Ann Hsu
- Divisions of Nephrology and Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | - Jessica Alves
- Department of Laboratory Medicine, Children’s Hospital, Boston, MA
| | - Marie Trudel
- Institut de Recherches Cliniques de Montréal, Molecular Genetics and Development, Faculte de Medecine, University of Montreal, Montreal
| | - Marco B. Rust
- Neurobiology/Neurophysiology Group, University of Kaiserslautern, Kaiserslautern, Germany
| | | | - Alicia Rivera
- Department of Laboratory Medicine, Children’s Hospital, Boston, MA
- Department of Pathology, Harvard Medical School, Boston, MA
| | - Seth L. Alper
- Divisions of Nephrology and Molecular and Vascular Medicine, Beth Israel Deaconess Medical Center, Boston, MA
- Department of Medicine, Harvard Medical School, Boston, MA
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30
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Regulation of the cardiac Na⁺/H⁺ exchanger in health and disease. J Mol Cell Cardiol 2013; 61:68-76. [PMID: 23429007 DOI: 10.1016/j.yjmcc.2013.02.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/07/2013] [Accepted: 02/11/2013] [Indexed: 11/21/2022]
Abstract
The Na(+) gradient produced across the cardiac sarcolemma by the ATP-dependent Na(+)-pump is a constant source of energy for Na(+)-dependent transporters. The plasma membrane Na(+)/H(+) exchanger (NHE) is one such secondary active transporter, regulating intracellular pH, Na(+) concentration, and cell volume. NHE1, the major isoform found in the heart, is activated in response to a variety of stimuli such as hormones and mechanical stress. This important characteristic of NHE1 is intimately linked to heart diseases, including maladaptive cardiac hypertrophy and subsequent heart failure, as well as acute ischemic-reperfusion injury. NHE1 activation results in elevation of pH and intracellular Na(+) concentration, which potentially enhance downstream signaling cascades in the myocardium. Therefore, in addition to determining the mechanism underlying regulation of NHE1 activity, it is important to understand how the ionic signal produced by NHE1 is transmitted to the downstream targets. Extensive studies have identified many accessory factors that interact with NHE1. Here, we have summarized the recent progress on understanding the molecular mechanism underlying NHE1 regulation and have shown a possible signaling pathway leading to cardiac remodeling, which is initiated from NHE1. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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