101
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Babich V, Vadnagara K, Di Sole F. Adenosine A 2A receptor blocks the A 1 receptor inhibition of renal Na + transport and oxygen consumption. J Cell Physiol 2019; 234:13917-13930. [PMID: 30633335 DOI: 10.1002/jcp.28074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Accepted: 12/18/2018] [Indexed: 11/11/2022]
Abstract
A high renal oxygen (O2 ) need is primarily associated with the renal tubular O2 consumption (VO2 ) necessary for a high rate of sodium (Na+ ) transport. Limited O2 availability leads to increased levels of adenosine, which regulates the kidney via activation of both A1 and A2A adenosine receptors (A1R and A2AR, respectively). The relative contributions of A1R and A2AR to the regulation of renal Na+ transport and VO2 have not been determined. We demonstrated that A1R activation has a dose-dependent biphasic effect on both renal Na+ /H+ exchanger-3 (NHE3), a major player in Na+ transport, and VO2 . Here, we report concentration-dependent effects of adenosine: less than 5 × 10-7 M adenosine-stimulated NHE3 activity; between 5 × 10-7 M and 10-5 M adenosine-inhibited NHE3 activity; and greater than 10-5 M adenosine reversed the change in NHE3 activity (returned to baseline). A1R activation mediated the activation and inhibition of NHE3 activity, whereas 10-4 M adenosine had no effect on the NHE3 activity due to A2AR activation. The following occurred when A1R and A2AR were activated: (a) Blockade of the A2AR receptor restored the NHE3 inhibition mediated by A1R activation, (b) the NHE-dependent effect on VO2 mediated by A1R activation became NHE independent, and (c) A2AR bound to A1R. In summary, A1R affects VO2 via NHE-dependent mechanisms, whereas A2AR acts via NHE-independent mechanisms. When both A1R and A2AR are activated, the A2AR effect on NHE3 and VO2 predominates, possibly via an A1R-A2AR protein interaction. A2AR-A1R heterodimerization is proposed as the molecular mechanism enabling the NHE-independent control of renal VO2 .
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Affiliation(s)
- Victor Babich
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, Iowa.,School of Liberal Arts and Sciences, Mercy College of Health Sciences, Des Moines, Iowa.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Komal Vadnagara
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Francesca Di Sole
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, Iowa.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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102
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Patiño-Ruiz M, Dwivedi M, Călinescu O, Karabel M, Padan E, Fendler K. Replacement of Lys-300 with a glutamine in the NhaA Na +/H + antiporter of Escherichia coli yields a functional electrogenic transporter. J Biol Chem 2019; 294:246-256. [PMID: 30409911 PMCID: PMC6322889 DOI: 10.1074/jbc.ra118.004903] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 11/06/2018] [Indexed: 01/28/2023] Open
Abstract
Much of the research on Na+/H+ exchange has been done in prokaryotic models, mainly on the NhaA Na+/H+-exchanger from Escherichia coli (EcNhaA). Two conserved aspartate residues, Asp-163 and Asp-164, are essential for transport and are candidates for possible binding sites for the two H+ that are exchanged for one Na+ to make the overall transport process electrogenic. More recently, a proposed mechanism of transport for EcNhaA has suggested direct binding of one of the transported H+ to the conserved Lys-300 residue, a salt bridge partner of Asp-163. This contention is supported by a study reporting that substitution of the equivalent residue, Lys-305, of a related Na+/H+ antiporter, NapA from Thermus thermophilus, renders the transporter electroneutral. In this work, we sought to establish whether the Lys-300 residue and its partner Asp-163 are essential for the electrogenicity of EcNhaA. To that end, we replaced Lys-300 with Gln, either alone or together with the simultaneous substitution of Asp-163 with Asn, and characterized these transporter variants in electrophysiological experiments combined with H+ transport measurements and stability analysis. We found that K300Q EcNhaA can still support electrogenic Na+/H+ antiport in EcNhaA, but has reduced thermal stability. A parallel electrophysiological investigation of the K305Q variant of TtNapA revealed that it is also electrogenic. Furthermore, replacement of both salt bridge partners in the ion-binding site of EcNhaA produced an electrogenic variant (D163N/K300Q). Our findings indicate that alternative mechanisms sustain EcNhaA activity in the absence of canonical ion-binding residues and that the conserved lysines confer structural stability.
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Affiliation(s)
- Miyer Patiño-Ruiz
- Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Manish Dwivedi
- Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Octavian Călinescu
- Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany; Department of Biophysics, "Carol Davila" University of Medicine and Pharmacy, 050474 Bucharest, Romania
| | - Mehmet Karabel
- Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - Etana Padan
- Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Klaus Fendler
- Max-Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
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103
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Challenges and Adaptations of Life in Alkaline Habitats. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2019; 172:85-133. [DOI: 10.1007/10_2019_97] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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104
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Dragwidge JM, Scholl S, Schumacher K, Gendall AR. NHX-type Na+(K+)/H+ antiporters are required for TGN/EE trafficking and endosomal ion homeostasis in Arabidopsis. J Cell Sci 2019; 132:jcs.226472. [DOI: 10.1242/jcs.226472] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Accepted: 02/21/2019] [Indexed: 12/17/2022] Open
Abstract
The regulation of ion and pH homeostasis of endomembrane organelles is critical for functional protein trafficking, sorting and modification in eukaryotic cells. pH homeostasis is maintained through the activity of vacuolar H+-ATPases (V-ATPases) pumping protons (H+) into the endomembrane lumen, and counter-action by cation/proton exchangers such as the NHX family of Na+(K+)/H+ exchangers. In plants, V-ATPase activity at the trans-Golgi network/early endosome (TGN/EE) is important for secretory and endocytic trafficking, however the role of the endosomal antiporters NHX5 and NHX6 in endomembrane trafficking is unclear. Here we show through genetic, pharmacological, and live-cell imaging approaches that double knockout of NHX5 and NHX6 results in the impairment of endosome motility, protein recycling at the TGN/EE, but not in the secretion of integral membrane proteins. Furthermore, we report that nhx5 nhx6 mutants are partially insensitive to osmotic swelling of TGN/EE induced by the monovalent cation ionophore monensin, and to late endosomal swelling by the phosphatidylinositol 3/4-kinase inhibitor wortmannin, demonstrating that NHX5 and NHX6 function to regulate the luminal cation composition of endosomes.
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Affiliation(s)
- Jonathan Michael Dragwidge
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, 5 Ring Road, La Trobe University, Bundoora, VIC 3086, Australia
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Stefan Scholl
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Karin Schumacher
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Anthony Richard Gendall
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, 5 Ring Road, La Trobe University, Bundoora, VIC 3086, Australia
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105
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Moshtaghi A, Rahi ML, Mather PB, Hurwood DA. An investigation of gene expression patterns that contribute to osmoregulation in Macrobrachium australiense: Assessment of adaptive responses to different osmotic niches. GENE REPORTS 2018. [DOI: 10.1016/j.genrep.2018.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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106
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Inhibition of Sodium-Hydrogen Antiport by Antibodies to NHA1 in Brush Border Membrane Vesicles from Whole Aedes aegypti Larvae. J Membr Biol 2018; 252:1-16. [PMID: 30392010 DOI: 10.1007/s00232-018-0053-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 10/31/2018] [Indexed: 10/27/2022]
Abstract
The present research report describes Na+/H+ antiport by brush border membrane vesicles isolated from whole larvae of Aedes aegypti (AeBBMVw). Our hypothesis is that acid quenching of acridine orange by AeBBMVw is predominantly mediated by Na+/H+ antiport via the NHA1 component of the AeBBMVw in the absence of amino acids and ATP. AeNHA1 is a Na+/H+ antiporter that has been postulated to exchange Na+ and H+ across the apical plasma membrane in posterior midgut of A. aegypti larvae. Its principal function is to recycle the H+ and Na+ that are transported during amino acid uptake, e.g., phenylalanine. This uptake is mediated, in part, by a voltage-driven, Na+-coupled, nutrient amino acid transporter (AeNAT8). The voltage is generated by an H+ V-ATPase. All three components, V-ATPase, antiporter, and nutrient amino acid transporter (VAN), are present in brush border membrane vesicles isolated from whole larvae of A. aegypti. By omitting ATP and amino acids, Na+/H+ antiport was measured by fluorescence quenching of acridine orange (AO) caused by acidification of either the internal vesicle medium (Na+in > Na+out) or the external fluid-membrane interface (Na+in < Na+out). Vesicles with 100 micromolar Na+ inside and 10 micromolar Na+ outside or with 0.01 micromolar Na+ inside and 100 micromolar Na+ outside quenched fluorescence of AO by as much as 30%. Acidification did not occur in the absence of AeBBMVw. Preincubation of AeBBMVw with antibodies to NHA1 inhibit Na+/H+ antiport dependent fluorescence quenching, indicating that AeNHA1 has a significant role in Na+/H+ exchange.
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107
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Masrati G, Dwivedi M, Rimon A, Gluck-Margolin Y, Kessel A, Ashkenazy H, Mayrose I, Padan E, Ben-Tal N. Broad phylogenetic analysis of cation/proton antiporters reveals transport determinants. Nat Commun 2018; 9:4205. [PMID: 30310075 PMCID: PMC6181914 DOI: 10.1038/s41467-018-06770-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 09/24/2018] [Indexed: 11/08/2022] Open
Abstract
Cation/proton antiporters (CPAs) play a major role in maintaining living cells' homeostasis. CPAs are commonly divided into two main groups, CPA1 and CPA2, and are further characterized by two main phenotypes: ion selectivity and electrogenicity. However, tracing the evolutionary relationships of these transporters is challenging because of the high diversity within CPAs. Here, we conduct comprehensive evolutionary analysis of 6537 representative CPAs, describing the full complexity of their phylogeny, and revealing a sequence motif that appears to determine central phenotypic characteristics. In contrast to previous suggestions, we show that the CPA1/CPA2 division only partially correlates with electrogenicity. Our analysis further indicates two acidic residues in the binding site that carry the protons in electrogenic CPAs, and a polar residue in the unwound transmembrane helix 4 that determines ion selectivity. A rationally designed triple mutant successfully converted the electrogenic CPA, EcNhaA, to be electroneutral.
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Affiliation(s)
- Gal Masrati
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
| | - Manish Dwivedi
- Department of Biological Chemistry, The Alexander Silberman Inst. of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Abraham Rimon
- Department of Biological Chemistry, The Alexander Silberman Inst. of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Yael Gluck-Margolin
- Department of Biological Chemistry, The Alexander Silberman Inst. of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Amit Kessel
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
| | - Haim Ashkenazy
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
| | - Itay Mayrose
- Department of Molecular Biology and Ecology of Plant, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel
| | - Etana Padan
- Department of Biological Chemistry, The Alexander Silberman Inst. of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978, Tel-Aviv, Israel.
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108
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Soto E, Ortega-Ramírez A, Vega R. Protons as Messengers of Intercellular Communication in the Nervous System. Front Cell Neurosci 2018; 12:342. [PMID: 30364044 PMCID: PMC6191491 DOI: 10.3389/fncel.2018.00342] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/14/2018] [Indexed: 12/18/2022] Open
Abstract
In this review, evidence demonstrating that protons (H+) constitute a complex, regulated intercellular signaling mechanisms are presented. Given that pH is a strictly regulated variable in multicellular organisms, localized extracellular pH changes may constitute significant signals of cellular processes that occur in a cell or a group of cells. Several studies have demonstrated that the low pH of synaptic vesicles implies that neurotransmitter release is always accompanied by the co-release of H+ into the synaptic cleft, leading to transient extracellular pH shifts. Also, evidence has accumulated indicating that extracellular H+ concentration regulation is complex and implies a source of protons in a network of transporters, ion exchangers, and buffer capacity of the media that may finally establish the extracellular proton concentration. The activation of membrane transporters, increased production of CO2 and of metabolites, such as lactate, produce significant extracellular pH shifts in nano- and micro-domains in the central nervous system (CNS), constituting a reliable signal for intercellular communication. The acid sensing ion channels (ASIC) function as specific signal sensors of proton signaling mechanism, detecting subtle variations of extracellular H+ in a range varying from pH 5 to 8. The main question in relation to this signaling system is whether it is only synaptically restricted, or a volume modulator of neuron excitability. This signaling system may have evolved from a metabolic activity detection mechanism to a highly localized extracellular proton dependent communication mechanism. In this study, evidence showing the mechanisms of regulation of extracellular pH shifts and of the ASICs and its function in modulating the excitability in various systems is reviewed, including data and its role in synaptic neurotransmission, volume transmission and even segregated neurotransmission, leading to a reliable extracellular signaling mechanism.
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Affiliation(s)
- Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | | | - Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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109
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Royero P, García L, Rosales A, D'Suze G, Sevcik C, Castillo C. Bactridine 2 effect in DRG neurons. Identification of NHE as a second target. Toxicon 2018; 151:37-46. [PMID: 29959967 DOI: 10.1016/j.toxicon.2018.06.083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 06/02/2018] [Accepted: 06/24/2018] [Indexed: 11/26/2022]
Abstract
Bactridine 2 (Bact-2) is an antibacterial toxin from Tityus discrepans venom which modifies isoforms 1.2, 1.4 and 1.6 voltage-dependent sodium (Nav) channels. Bactridine-induced Na+ outflow in Yersinia enterocolitica was blocked by amiloride, suggesting that Bact-2 effect was mediated by an amiloride sensitive sodium channel. In this study we show that Bact-2 increases also an outward rectifying current in rat dorsal root ganglia (DRG) sensory neurons; therefore, the nature of the outward rectifying currents was characterized and then the effect of Bact-2 on these currents was studied. These currents are enhanced by amiloride, are decreased by Na+ when an outward pH gradient is present and its reversal potential coincides with that of a Cl-/H+ exchanger, suggesting that rectifying currents are produced by the electrogenic Cl-/H+ exchanger modulated by the Na+/H+ antiporter. Bact-2 also leads to an increase of the outward currents in a similar way to the produced by the inhibition of the Na+/H+ exchanger. Additionally, the subsequent application of Bact-2 after blocking the Na+/H+ exchanger does not produce any further effect, suggesting that Bact-2 modifies the outward current by modulating the activity of the Na+/H+ exchanger. The effect of Bact-2 on pHi regulation was determined using the pH indicator BCECF. The results show that the Na+/H+ exchanger is blocked by amiloride and Na+ free solutions and is modulated by Bact-2 in a similar way as cariporide. This study validates that besides Nav channels, Bact-2 modulates the activity of the Na+/H+ exchanger.
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Affiliation(s)
- Pedro Royero
- Unidad de Neurociencias, Instituto de Estudios Avanzados IDEA, Caracas, 1080, Venezuela; Depto. de Biología Celular, Universidad Simón Bolívar, Caracas, 1080, Venezuela
| | - Lisbeth García
- Unidad de Neurociencias, Instituto de Estudios Avanzados IDEA, Caracas, 1080, Venezuela
| | - Arnaldo Rosales
- Laboratory of Cellular Neuropharmacology, Biophysics and Biochemistry Center, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado, 20632, Caracas 1020-A, Venezuela
| | - Gina D'Suze
- Laboratory of Cellular Neuropharmacology, Biophysics and Biochemistry Center, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado, 20632, Caracas 1020-A, Venezuela.
| | - Carlos Sevcik
- Laboratory of Cellular Neuropharmacology, Biophysics and Biochemistry Center, Instituto Venezolano de Investigaciones Científicas (IVIC), Apartado, 20632, Caracas 1020-A, Venezuela
| | - Cecilia Castillo
- Unidad de Neurociencias, Instituto de Estudios Avanzados IDEA, Caracas, 1080, Venezuela.
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110
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Dragwidge JM, Ford BA, Ashnest JR, Das P, Gendall AR. Two Endosomal NHX-Type Na+/H+ Antiporters are Involved in Auxin-Mediated Development in Arabidopsis thaliana. PLANT & CELL PHYSIOLOGY 2018; 59:1660-1669. [PMID: 29788486 DOI: 10.1093/pcp/pcy090] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 04/29/2018] [Indexed: 05/16/2023]
Abstract
In Arabidopsis thaliana, the endosomal-localized Na+/H+ antiporters NHX5 and NHX6 regulate ion and pH homeostasis and are important for plant growth and development. However, the mechanism by which these endosomal NHXs function in plant development is not well understood. Auxin modulates plant growth and development through the formation of concentration gradients in plant tissue to control cell division and expansion. Here, we identified a role for NHX5 and NHX6 in the establishment and maintenance of auxin gradients in embryo and root tissues. We observed developmental impairment and abnormal cell division in embryo and root tissues in the double knockout nhx5 nhx6, consistent with these tissues showing high expression of NHX5 and NHX6. Through confocal microscopy imaging with the DR5::GFP auxin reporter, we identify defects in the perception, accumulation and redistribution of auxin in nhx5 nhx6 cells. Furthermore, we find that the steady-state levels of the PIN-FORMED (PIN) auxin efflux carriers PIN1 and PIN2 are reduced in nhx5 nhx6 root cells. Our results demonstrate that NHX5 and NHX6 function in auxin-mediated plant development by maintaining PIN abundance at the plasma membrane, and provide new insight into the regulation of plant development by endosomal NHX antiporters.
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Affiliation(s)
- Jonathan Michael Dragwidge
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, La Trobe University, 5 Ring Road, Bundoora, VIC, Australia
| | - Brett Andrew Ford
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, La Trobe University, 5 Ring Road, Bundoora, VIC, Australia
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Clunies Ross Street, Acton, ACT, Australia
| | - Joanne Rachel Ashnest
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, La Trobe University, 5 Ring Road, Bundoora, VIC, Australia
- Global Institute for Food Security, 110 Gymnasium Place, University of Saskatchewan, Saskatoon, Canada
| | - Partha Das
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, La Trobe University, 5 Ring Road, Bundoora, VIC, Australia
- College of Agriculture, Tripura, Lembucherra, India
| | - Anthony Richard Gendall
- Department of Animal, Plant and Soil Sciences, AgriBio, Centre for AgriBiosciences, La Trobe University, 5 Ring Road, Bundoora, VIC, Australia
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111
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Dutta D, Fliegel L. Molecular modeling and inhibitor docking analysis of the Na +/H + exchanger isoform one 1. Biochem Cell Biol 2018; 97:333-343. [PMID: 30058365 DOI: 10.1139/bcb-2018-0158] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Na+/H+ exchanger isoform one (NHE1) is a mammalian plasma membrane protein that removes intracellular protons, thereby elevating intracellular pH (pHi). NHE1 uses the energy of allowing an extracellular sodium down its gradient into cells to remove one intracellular proton. The ubiquitous protein has several important physiological and pathological influences on mammalian cells as a result of its activity. The three-dimensional structure of human NHE1 (hNHE1) is not known. Here, we modeled NHE1 based on the structure of MjNhaP1 of Methanocaldoccocus jannaschii in combination with biochemical surface accessibility data. hNHE1 contained 12 transmembrane segments including a characteristic Na+/H+ antiporter fold of two transmembrane segments with a helix - extended region - helix conformation crossing each other within the membrane. Amino acids 363-410 mapped principally to the extracellular surface as an extracellular loop (EL5). A large preponderance of amino acids shown to be surface accessible by biochemical experiments mapped near to, or on, the extracellular surface. Docking of Na+/H+ exchanger inhibitors to the extracellular surface suggested that inhibitor binding on an extracellular site is made up from several amino acids of different regions of the protein. The results present a novel testable, three-dimensional model illustrating NHE1 structure and accounting for experimental biochemical data.
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Affiliation(s)
- Debajyoti Dutta
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.,Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.,Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
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112
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Amyloid clearance defect in ApoE4 astrocytes is reversed by epigenetic correction of endosomal pH. Proc Natl Acad Sci U S A 2018; 115:E6640-E6649. [PMID: 29946028 DOI: 10.1073/pnas.1801612115] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Endosomes have emerged as a central hub and pathogenic driver of Alzheimer's disease (AD). The earliest brain cytopathology in neurodegeneration, occurring decades before amyloid plaques and cognitive decline, is an expansion in the size and number of endosomal compartments. The strongest genetic risk factor for sporadic AD is the ε4 allele of Apolipoprotein E (ApoE4). Previous studies have shown that ApoE4 potentiates presymptomatic endosomal dysfunction and defective endocytic clearance of amyloid beta (Aβ), although how these two pathways are linked at a cellular and mechanistic level has been unclear. Here, we show that aberrant endosomal acidification in ApoE4 astrocytes traps the low-density lipoprotein receptor-related protein (LRP1) within intracellular compartments, leading to loss of surface expression and Aβ clearance. Pathological endosome acidification is caused by ε4 risk allele-selective down-regulation of the Na+/H+ exchanger isoform NHE6, which functions as a critical leak pathway for endosomal protons. In vivo, the NHE6 knockout (NHE6KO) mouse model showed elevated Aβ in the brain, consistent with a causal effect. Increased nuclear translocation of histone deacetylase 4 (HDAC4) in ApoE4 astrocytes, compared with the nonpathogenic ApoE3 allele, suggested a mechanistic basis for transcriptional down-regulation of NHE6. HDAC inhibitors that restored NHE6 expression normalized ApoE4-specific defects in endosomal pH, LRP1 trafficking, and amyloid clearance. Thus, NHE6 is a downstream effector of ApoE4 and emerges as a promising therapeutic target in AD. These observations have prognostic implications for patients who have Christianson syndrome with loss of function mutations in NHE6 and exhibit prominent glial pathology and progressive hallmarks of neurodegeneration.
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113
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Meng K, Wu Y. Footprints of divergent evolution in two Na+/H+ type antiporter gene families (NHX and SOS1) in the genus Populus. TREE PHYSIOLOGY 2018; 38:813-824. [PMID: 29394412 DOI: 10.1093/treephys/tpx173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 12/19/2017] [Indexed: 05/19/2023]
Abstract
Populus, a deciduous tree species of major economic and ecological value, grows across the range in which trees are distributed in the Northern Hemisphere. Patterns of DNA variation are often used to identify the evolutionary forces shaping the genotypes of distinctive species lineages. Sodium/hydrogen (Na+/H+) antiporter genes have been shown to play a central role in plant salt tolerance. Here, we analyzed DNA nucleotide polymorphisms in the Na+/H+ antiporter (NHX and SOS1) gene families across 30 different Populus species using several methods of phylogenetic analysis and functional verification. NHX and SOS1 gene families in the genus Populus have expanded from the state in their common ancestors by duplication events, and their distinct lineages have been retained. Signals of positive selection at certain amino acid sites in different members of the Na/H antiporter gene families show that the dynamics that drive the evolution of each gene vary. SOS1 has undergone duplication in Populus euphratica and been subjected to adaptive evolution in section Turanga; the paralog of PeSOS1 (PeSOS1.2) can complement the Escherichia coli mutant EP432; and the expression pattern of PeSOS1.2 is different from that of PeSOS1, a fact which may have been beneficial for P. euphratica, conferring a fitness advantage in saline habitats. The divergent evolution of the individual members of the NHX and SOS1 gene families is likely to have been influenced by the varied ecological and environmental niches occupied by the different poplar species, giving rise to evolutionary footprints that reflect the specific functions and subcellular localizations of the proteins encoded by these genes.
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Affiliation(s)
- Kuibin Meng
- State Key Laboratory of Grassland Agro-Ecosystem, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yuxia Wu
- State Key Laboratory of Grassland Agro-Ecosystem, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
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114
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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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115
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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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116
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Dawut K, Sirisattha S, Hibino T, Kageyama H, Waditee-Sirisattha R. Functional characterization of the NhaA Na +/H + antiporter from the green picoalga Ostreococcus tauri. Arch Biochem Biophys 2018; 649:37-46. [PMID: 29730321 DOI: 10.1016/j.abb.2018.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Revised: 05/01/2018] [Accepted: 05/02/2018] [Indexed: 12/13/2022]
Abstract
Transmembrane ion transport is a critical process in the cellular response to salt stress. Among the known functional membrane transporters that are involved in the salt stress response, Na+/H+ antiporters have been extensively studied. These ubiquitous membrane proteins are crucial for salt tolerance and are associated with the regulation of internal pH, cell volume, morphogenesis, and vesicular trafficking. Molecular and functional analyses of Na+/H+ antiporters have been characterized among taxa but little is known about algal Na+/H+ antiporters. Here, we analyzed putative Na+/H+ antiporters from the complete genome sequence of the marine picoalga Ostreococcus tauri. At least 10 putative Na+/H+ antiporters belonging to the SOS1, NHX, and KEA/Kef families were found. Surprisingly, a bacterial type NhaA sequence (OtNhaA) was also found. Topological modeling of OtNhaA predicted 12 possible transmembrane segments with a long N-terminus. The full-length (FL_OtNhaA) and N-terminal truncated (ΔN112_OtNhaA) versions of OtNhaA were constructed, expressed in the salt-sensitive mutant Escherichia coli TO114, and functionally characterized. Complementation analysis revealed that FL_OtNhaA- and ΔN112_OtNhaA-expressing cells exhibited increased tolerance to high NaCl concentrations up to 700 mM. Antiporter activity assays showed that both FL_OtNhaA and ΔN112_OtNhaA proteins predominantly exhibited Na+/H+ and Ca2+/H+ antiporter activities at alkaline pH conditions. Intriguingly, the ΔN112_OtNhaA exhibited higher Na+/H+ and Ca2+/H+ antiporter activities compared to FL_OtNhaA. Kinetic analysis revealed that FL_OtNhaA has a high affinity for Na+ and Ca2+ ions with a Km of 1.1 ± 0.23 mM for Na+ (at pH 8.5) and a Km of 0.3 ± 0.07 mM for Ca2+ (at pH 8.5). Since NhaA has shown striking diversity among taxa, our results provide insight into the functional properties of the algal NhaA Na+/H+ antiporter. These results will contribute to the understanding of Na+/H+ antiporters that have various implications in all kingdoms of life.
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Affiliation(s)
- Keatisuda Dawut
- Department of Microbiology, Faculty of Science, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand; Program in Biotechnology, Faculty of Science, Chulalongkorn University, Pathumwan, Bangkok 10330, Thailand
| | - Sophon Sirisattha
- Thailand Institute of Scientific and Technological Research (TISTR), Pathum Thani 12120, Thailand
| | - Takashi Hibino
- Department of Chemistry, Faculty of Science and Technology, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Hakuto Kageyama
- Department of Chemistry, Faculty of Science and Technology, Meijo University, Nagoya, Aichi 468-8502, Japan.
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117
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Hima Kumari P, Anil Kumar S, Ramesh K, Sudhakar Reddy P, Nagaraju M, Bhanu Prakash A, Shah T, Henderson A, Srivastava RK, Rajasheker G, Chitikineni A, Varshney RK, Rathnagiri P, Lakshmi Narasu M, Kavi Kishor PB. Genome-Wide Identification and Analysis of Arabidopsis Sodium Proton Antiporter (NHX) and Human Sodium Proton Exchanger (NHE) Homologs in Sorghum bicolor. Genes (Basel) 2018; 9:genes9050236. [PMID: 29751546 PMCID: PMC5977176 DOI: 10.3390/genes9050236] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/24/2018] [Accepted: 04/24/2018] [Indexed: 11/16/2022] Open
Abstract
Na⁺ transporters play an important role during salt stress and development. The present study is aimed at genome-wide identification, in silico analysis of sodium-proton antiporter (NHX) and sodium-proton exchanger (NHE)-type transporters in Sorghum bicolor and their expression patterns under varied abiotic stress conditions. In Sorghum, seven NHX and nine NHE homologs were identified. Amiloride (a known inhibitor of Na⁺/H⁺ exchanger activity) binding motif was noticed in both types of the transporters. Chromosome 2 was found to be a hotspot region with five sodium transporters. Phylogenetic analysis inferred six ortholog and three paralog groups. To gain an insight into functional divergence of SbNHX/NHE transporters, real-time gene expression was performed under salt, drought, heat, and cold stresses in embryo, root, stem, and leaf tissues. Expression patterns revealed that both SbNHXs and SbNHEs are responsive either to single or multiple abiotic stresses. The predicted protein⁻protein interaction networks revealed that only SbNHX7 is involved in the calcineurin B-like proteins (CBL)- CBL interacting protein kinases (CIPK) pathway. The study provides insights into the functional divergence of SbNHX/NHE transporter genes with tissue specific expressions in Sorghum under different abiotic stress conditions.
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Affiliation(s)
- P Hima Kumari
- Department of Genetics, Osmania University, Hyderabad 500 007, India.
- Centre for Biotechnology, Institute of Science & Technology, JNT University, Hyderabad 500 085, India.
| | - S Anil Kumar
- Department of Genetics, Osmania University, Hyderabad 500 007, India.
- Centre for Biotechnology, Institute of Science & Technology, JNT University, Hyderabad 500 085, India.
| | - Katam Ramesh
- Department of Biological Sciences, Florida A&M University, Tallahassee, FL 32307, USA.
| | - Palakolanu Sudhakar Reddy
- Center of Excellence in Genomics & Systems Biology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad 502 324, India.
| | - M Nagaraju
- Department of Genetics, Osmania University, Hyderabad 500 007, India.
| | - A Bhanu Prakash
- Center of Excellence in Genomics & Systems Biology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad 502 324, India.
| | - Trushar Shah
- IITA-Kenya c/o International Livestock Research Institute (ILRI), PO Box 30709, Nairobi 00100, Kenya.
| | - Ashley Henderson
- Department of Biological Sciences, Florida A&M University, Tallahassee, FL 32307, USA.
- Ottawa University, Ottawa, KS 66067, USA.
| | - Rakesh K Srivastava
- Center of Excellence in Genomics & Systems Biology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad 502 324, India.
| | - G Rajasheker
- Department of Genetics, Osmania University, Hyderabad 500 007, India.
| | - A Chitikineni
- Center of Excellence in Genomics & Systems Biology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad 502 324, India.
| | - Rajeev K Varshney
- Center of Excellence in Genomics & Systems Biology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Hyderabad 502 324, India.
| | - P Rathnagiri
- Genomix CARL Pvt. Ltd. Rayalapuram Road, Pulivendula, 516 390, Kadapa, Andhra Pradesh, India.
| | - M Lakshmi Narasu
- Centre for Biotechnology, Institute of Science & Technology, JNT University, Hyderabad 500 085, India.
| | - P B Kavi Kishor
- Department of Genetics, Osmania University, Hyderabad 500 007, India.
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118
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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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119
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Prasad H, Rao R. Histone deacetylase-mediated regulation of endolysosomal pH. J Biol Chem 2018; 293:6721-6735. [PMID: 29567836 DOI: 10.1074/jbc.ra118.002025] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 03/19/2018] [Indexed: 11/06/2022] Open
Abstract
The pH of the endolysosomal system is tightly regulated by a balance of proton pump and leak mechanisms that are critical for storage, recycling, turnover, and signaling functions in the cell. Dysregulation of endolysosomal pH has been linked to aging, amyloidogenesis, synaptic dysfunction, and various neurodegenerative disorders, including Alzheimer's disease. Therefore, understanding the mechanisms that regulate luminal pH may be key to identifying new targets for managing these disorders. Meta-analysis of yeast microarray databases revealed that nutrient-limiting conditions inhibited the histone deacetylase (HDAC) Rpd3 and thereby up-regulated transcription of the endosomal Na+/H+ exchanger Nhx1, resulting in vacuolar alkalinization. Consistent with these findings, Rpd3 inhibition by the HDAC inhibitor and antifungal drug trichostatin A induced Nhx1 expression and vacuolar alkalinization. Bioinformatics analysis of Drosophila and mouse databases revealed that caloric control of the Nhx1 orthologs DmNHE3 and NHE6, respectively, is also mediated by HDACs. We show that NHE6 is a target of the transcription factor cAMP-response element-binding protein (CREB), a known regulator of cellular responses to low-nutrient conditions, providing a molecular mechanism for nutrient- and HDAC-dependent regulation of endosomal pH. Of note, pharmacological targeting of the CREB pathway to increase NHE6 expression helped regulate endosomal pH and correct defective clearance of amyloid Aβ in an apoE4 astrocyte model of Alzheimer's disease. These observations from yeast, fly, mouse, and cell culture models point to an evolutionarily conserved mechanism for HDAC-mediated regulation of endosomal NHE expression. Our insights offer new therapeutic strategies for modulation of endolysosomal pH in fungal infection and human disease.
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Affiliation(s)
- Hari Prasad
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Rajini Rao
- From the Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Asp133 Residue in NhaA Na+/H+ Antiporter Is Required for Stability Cation Binding and Transport. J Mol Biol 2018; 430:867-880. [DOI: 10.1016/j.jmb.2018.01.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 01/23/2018] [Accepted: 01/23/2018] [Indexed: 11/18/2022]
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121
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Babich V, Henry MK, Di Sole F. Application of Electrophysiology Measurement to Study the Activity of Electro-Neutral Transporters. J Vis Exp 2018. [PMID: 29443070 DOI: 10.3791/56630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The transport of ions through cell membranes ensures the fine control of ion content within and outside the cell that is indispensable for cell survival. These transport mechanisms are mediated by the activities of specialized transporter proteins. Specifically,pH dynamics are finely controlled by plasma membrane proton (H+) extrusion systems, such as the Na+/H+ exchanger (NHE) protein family. Despite extensive efforts to study the mechanisms underlying NHE regulation, our current understanding of the biophysical and molecular properties of the NHE family is inadequate because of the limited availability of methods to effectively measure NHE activity. In this manuscript, we used H+-selective electrodes during whole-cell patch clamping recording to measure NHE-induced H+ flux. We proposed this approach to overcome some limitations of typically used methods to measure NHE activity, such as radioactive uptake and fluorescent membrane permeants. Measurement of NHE activity using the described method enables high sensitivity and time resolution and more efficient control of intracellular H+ concentrations. H+-selective electrodes are based on the fact that transporter activity creates an ion gradient in close proximity to the cell membrane. An H+-selective electrode moving up to and away from the cell membrane in a repetitive, oscillatory fashion records a voltage difference that is dependent on H+ flux. While H+-selective electrodes are used to detect H+ flux moving out of the cell, the patch clamp method in the whole-cell configuration is used to control the intracellular ion composition. Moreover, application of the giant patch clamp technique allows modification of the intracellular composition of not only ions but also lipids. The transporter activity of NHE isoform 3 (NHE3) was measured using this technical approach to study the molecular basis of NHE3 regulation by phosphoinositides.
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Affiliation(s)
- Victor Babich
- Physiology and Pharmacology Department, Des Moines University; School of Liberal Arts and Sciences, Mercy College of Health Sciences
| | - Matthew K Henry
- Physiology and Pharmacology Department, Des Moines University
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122
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Karim MA, Brett CL. The Na +(K +)/H + exchanger Nhx1 controls multivesicular body-vacuolar lysosome fusion. Mol Biol Cell 2018; 29:317-325. [PMID: 29212874 PMCID: PMC5996954 DOI: 10.1091/mbc.e17-08-0496] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 11/07/2017] [Accepted: 11/28/2017] [Indexed: 01/12/2023] Open
Abstract
Loss-of-function mutations in human endosomal Na+(K+)/H+ exchangers (NHEs) NHE6 and NHE9 are implicated in neurological disorders including Christianson syndrome, autism, and attention deficit and hyperactivity disorder. These mutations disrupt retention of surface receptors within neurons and glial cells by affecting their delivery to lysosomes for degradation. However, the molecular basis of how these endosomal NHEs control endocytic trafficking is unclear. Using Saccharomyces cerevisiae as a model, we conducted cell-free organelle fusion assays to show that transport activity of the orthologous endosomal NHE Nhx1 is important for multivesicular body (MVB)-vacuolar lysosome fusion, the last step of endocytosis required for surface protein degradation. We find that deleting Nhx1 disrupts the fusogenicity of the MVB, not the vacuole, by targeting pH-sensitive machinery downstream of the Rab-GTPase Ypt7 needed for SNARE-mediated lipid bilayer merger. All contributing mechanisms are evolutionarily conserved offering new insight into the etiology of human disorders linked to loss of endosomal NHE function.
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Mixed Neurodevelopmental and Neurodegenerative Pathology in Nhe6-Null Mouse Model of Christianson Syndrome. eNeuro 2018; 4:eN-NWR-0388-17. [PMID: 29349289 PMCID: PMC5771691 DOI: 10.1523/eneuro.0388-17.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 12/12/2017] [Accepted: 12/17/2017] [Indexed: 12/20/2022] Open
Abstract
Christianson syndrome (CS) is an X-linked disorder resulting from loss-of-function mutations in SLC9A6, which encodes the endosomal Na+/H+ exchanger 6 (NHE6). Symptoms include early developmental delay, seizures, intellectual disability, nonverbal status, autistic features, postnatal microcephaly, and progressive ataxia. Neuronal development is impaired in CS, involving defects in neuronal arborization and synaptogenesis, likely underlying diminished brain growth postnatally. In addition to neurodevelopmental defects, some reports have supported neurodegenerative pathology in CS with age. The objective of this study was to determine the nature of progressive changes in the postnatal brain in Nhe6-null mice. We examined the trajectories of brain growth and atrophy in mutant mice from birth until very old age (2 yr). We report trajectories of volume changes in the mutant that likely reflect both brain undergrowth as well as tissue loss. Reductions in volume are first apparent at 2 mo, particularly in the cerebellum, which demonstrates progressive loss of Purkinje cells (PCs). We report PC loss in two distinct Nhe6-null mouse models. More widespread reductions in tissue volumes, namely, in the hippocampus, striatum, and cortex, become apparent after 2 mo, largely reflecting delays in growth with more limited tissue losses with aging. Also, we identify pronounced glial responses, particularly in major fiber tracts such as the corpus callosum, where the density of activated astrocytes and microglia are substantially increased. The prominence of the glial response in axonal tracts suggests a primary axonopathy. Importantly, therefore, our data support both neurodevelopmental and degenerative mechanisms in the pathobiology of CS.
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Gomez Zubieta DM, Hamood MA, Beydoun R, Pall AE, Kondapalli KC. MicroRNA-135a regulates NHE9 to inhibit proliferation and migration of glioblastoma cells. Cell Commun Signal 2017; 15:55. [PMID: 29268774 PMCID: PMC5740897 DOI: 10.1186/s12964-017-0209-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 12/08/2017] [Indexed: 12/13/2022] Open
Abstract
Background Glioblastoma multiformae (GBM) is the most aggressive type of malignant brain tumor with complex molecular profile. Overexpression of Na+/H+ Exchanger isoform 9 (NHE9) promotes tumor progression and correlates positively with insensitivity to radiochemotherapy and poor prognosis. However, molecular mechanisms responsible for increase in NHE9 levels beyond a critical threshold have not been identified. Methods Bioinformatics analysis, luciferase reporter assays, real-time PCR and western blotting were conducted to examine the expression profiles and identify microRNAs (miRNA) that target NHE9. Cell proliferation and migration assays were conducted in U87 glioblastoma cells to determine the consequence of miRNA mediated targeting of NHE9. Endosomal pH measurements, immunofluorescence microscopy and surface biotinylation experiments were conducted to characterize the mechanistic basis of regulation. Results We show that microRNA 135a (miR-135a) targets NHE9 to downregulate its expression in U87 cells. MiR-135a levels are significantly lower in glioblastoma cells compared to normal brain tissue. Downregulation of NHE9 expression by miR-135a affects proliferative and migratory capacity of U87 cells. Selectively increasing NHE9 expression in these cells restored their ability to proliferate and migrate. We demonstrate that miR-135a takes a two-pronged approach affecting epidermal growth factor receptors (EGFRs) to suppress tumor cell growth and migration. EGFR activity is a potent stimulator of oncogenic signaling. While miR-135a targets EGFR transcripts to decrease the total number of receptors made, by targeting NHE9 it routes the few EGFRs made away from the plasma membrane to dampen oncogenic signaling. NHE9 is localized to sorting endosomes in glioblastoma cells where it alkalinizes the endosome lumen by leaking protons. Downregulation of NHE9 expression by miR-135a acidifies sorting endosomes limiting EGFR trafficking to the glioblastoma cell membrane. Conclusions We propose downregulation of miR-135a as a potential mechanism underlying the high NHE9 expression observed in subset of glioblastomas. Future studies should explore miR-135a as a potential therapeutic for glioblastomas with NHE9 overexpression. Electronic supplementary material The online version of this article (10.1186/s12964-017-0209-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Daniela M Gomez Zubieta
- Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Road, SFC # 207, Dearborn, MI, 48128, USA
| | - Mohamed A Hamood
- Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Road, SFC # 207, Dearborn, MI, 48128, USA
| | - Rami Beydoun
- Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Road, SFC # 207, Dearborn, MI, 48128, USA
| | - Ashley E Pall
- Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Road, SFC # 207, Dearborn, MI, 48128, USA
| | - Kalyan C Kondapalli
- Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Road, SFC # 207, Dearborn, MI, 48128, USA.
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125
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Dutta D, Fliegel L. Structure and function of yeast and fungal Na + /H + antiporters. IUBMB Life 2017; 70:23-31. [PMID: 29219228 DOI: 10.1002/iub.1701] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 11/21/2017] [Indexed: 12/22/2022]
Abstract
Sodium proton antiporters (or sodium proton exchangers [NHEs]) are a critical family of membrane proteins that exchange sodium for protons across cell membranes. In yeast and plants, their primary function is to keep the sodium concentration low inside the cytoplasm. One class of NHE constitutively expressed in yeast is the plasma membrane Na+ /H+ antiporter, and another class is expressed on the endosomal/vacuolar membrane. At present, four bacterial plasma membrane antiporter structures are known and nuclear magnetic resonance structures are available for the membrane spanning transmembrane helices of mammalian and yeast NHEs. Additionally, a vast amount of mutational data are available on the role of individual amino acids and critical motifs involved in transport. We combine this information to obtain a more detailed picture of the yeast NHE plasma membrane protein and review mechanisms of transport, conserved motifs, unique residues important in function, and regulation of these proteins. The Na+ /H+ antiporter of Schizosaccharomyces pombe, SpNHE1, is an interesting model protein in an easy to study system and is representative of fungal Na+ /H+ antiporters. © IUBMB Life, 70(1):23-31, 2018.
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Affiliation(s)
- Debajyoti Dutta
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
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126
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Pan T, Liu Y, Su X, An L, Qiu QS. Domain-switch analysis of PeNHX3 from Populus euphratica reveals the critical role of the transmembrane domain 11 in Na + and Li + transport. JOURNAL OF PLANT PHYSIOLOGY 2017; 219:1-11. [PMID: 28946051 DOI: 10.1016/j.jplph.2017.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 09/12/2017] [Accepted: 09/13/2017] [Indexed: 06/07/2023]
Abstract
Populus euphratica, the well-known tree halophyte, tolerates the stress of high levels of salt. We previously showed that the transmembrane domain 11 (TM11) of PeNHX3, a Na+,K+/H+ antiporter from P. euphratica, was crucial for Na+ and Li+ transport in a yeast growth assay. Here, we examined the role of TM11 in catalyzing Na+ and Li+ transport in transgenic Arabidopsis. We found that PeNHX3 localized to the tonoplasts in Arabidopsis. Overexpression of PeNHX3 in Arabidopsis improved seedling growth and enhanced salt tolerance and Li+ detoxification. However, overexpression of PeNHX3 did not improve Arabidopsis growth at KCl concentrations higher than 0.1mM, suggesting a low K+ transport activity for PeNHX3 in plants. We performed in planta domain-switch analysis by replacing the C-terminal domain of AtNHX1 with a C-terminal segment of PeNHX3 containing the TM11 domain. We demonstrated that TM11 was critical for the Na+ and Li+ transport activities by PeNHX3. Taken together, PeNHX3 plays an important role in salt tolerance and Li+ detoxification in plants. TM11 controls the Na+ and Li+ transport activities of PeNHX3 in Arabidopsis.
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Affiliation(s)
- Ting Pan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Yafen Liu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Xiaomeng Su
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Lizhe An
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China
| | - Quan-Sheng Qiu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 73000, China.
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Chen X, Wang X, Tang L, Wang J, Shen C, Liu J, Lu S, Zhang H, Kuang Y, Fei J, Wang Z. Nhe5 deficiency enhances learning and memory via upregulating Bdnf/TrkB signaling in mice. Am J Med Genet B Neuropsychiatr Genet 2017; 174:828-838. [PMID: 28981195 DOI: 10.1002/ajmg.b.32600] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 07/10/2017] [Accepted: 09/05/2017] [Indexed: 11/11/2022]
Abstract
Nhe5, a Na+ /H+ exchanger, is predominantly expressed in brain tissue and is proposed to act as a negative regulator of dendritic spine growth. Up to now, its physiological function in vivo remains unclear. Here we show that Nhe5-deficient mice exhibit markedly enhanced learning and memory in Morris water maze, novel object recognition, and passive avoidance task. Meanwhile, the pre- and post-synaptic components, synaptophysin (Syn) and post-synaptic density 95 (PSD95) expression levels were found increased in hippocampal regions lacking of Nhe5, suggesting a possible alterations in neuronal synaptic structure and function in Nhe5-/- mice. Further study reveals that Nhe5 deficiency leads to higher Bdnf expression levels, followed by increased phosphorylated TrkB and PLCγ levels, indicating that Bdnf/TrkB signaling is activated due to Nhe5 deficiency. Moreover, the corresponding brain regions of Nhe5-/- mice display elevated ERK/CaMKII/CREB phosphorylation levels. Taken together, these findings uncover a novel physiological function of Nhe5 in regulating learning and memory, further implying Nhe5 as a potential therapeutic target for improving cognition.
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Affiliation(s)
- Xuejiao Chen
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.,Shanghai Research Center for Model Organisms, Shanghai, China
| | - Xiyi Wang
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.,Shanghai Research Center for Model Organisms, Shanghai, China
| | - Lingyun Tang
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Jinjin Wang
- Shanghai Research Center for Model Organisms, Shanghai, China
| | - Chunling Shen
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.,Shanghai Research Center for Model Organisms, Shanghai, China
| | - Jianbing Liu
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.,Shanghai Research Center for Model Organisms, Shanghai, China
| | - Shunyuan Lu
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Hongxin Zhang
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China
| | - Ying Kuang
- Shanghai Research Center for Model Organisms, Shanghai, China
| | - Jian Fei
- Shanghai Research Center for Model Organisms, Shanghai, China
| | - Zhugang Wang
- State Key Laboratory of Medical Genomics, Research Center for Experimental Medicine of Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine (SJTUSM), Shanghai, China.,Shanghai Research Center for Model Organisms, Shanghai, China.,Department of Medical Genetics, E-Institutes of Shanghai Universities, SJTUSM, Shanghai, China
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128
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Dibrov P, Dibrov E, Pierce GN. Na+-NQR (Na+-translocating NADH:ubiquinone oxidoreductase) as a novel target for antibiotics. FEMS Microbiol Rev 2017; 41:653-671. [PMID: 28961953 DOI: 10.1093/femsre/fux032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 05/17/2017] [Indexed: 01/08/2023] Open
Abstract
The recent breakthrough in structural studies on Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) from the human pathogen Vibrio cholerae creates a perspective for the systematic design of inhibitors for this unique enzyme, which is the major Na+ pump in aerobic pathogens. Widespread distribution of Na+-NQR among pathogenic species, its key role in energy metabolism, its relation to virulence in different species as well as its absence in eukaryotic cells makes this enzyme especially attractive as a target for prospective antibiotics. In this review, the major biochemical, physiological and, especially, the pharmacological aspects of Na+-NQR are discussed to assess its 'target potential' for drug development. A comparison to other primary bacterial Na+ pumps supports the contention that NQR is a first rate prospective target for a new generation of antimicrobials. A new, narrowly targeted furanone inhibitor of NQR designed in our group is presented as a molecular platform for the development of anti-NQR remedies.
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Affiliation(s)
- Pavel Dibrov
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | - Elena Dibrov
- Institute of Cardiovascular Sciences, Albrechtsen Research Centre, St. Boniface Hospital, Winnipeg, Canada.,Department of Physiology and Pathophysiology, Colleges of Medicine and Pharmacy, Faculty of Health Sciences, Winnipeg, Canada
| | - Grant N Pierce
- Institute of Cardiovascular Sciences, Albrechtsen Research Centre, St. Boniface Hospital, Winnipeg, Canada.,Department of Physiology and Pathophysiology, Colleges of Medicine and Pharmacy, Faculty of Health Sciences, Winnipeg, Canada
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129
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Dutta D, Shin K, Rainey JK, Fliegel L. Transmembrane Segment XI of the Na +/H + Antiporter of S. pombe is a Critical Part of the Ion Translocation Pore. Sci Rep 2017; 7:12793. [PMID: 29038548 PMCID: PMC5643542 DOI: 10.1038/s41598-017-12701-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 09/18/2017] [Indexed: 01/01/2023] Open
Abstract
The Na+/H+ exchanger of the plasma membrane of S. pombe (SpNHE1) removes intracellular sodium in exchange for an extracellular proton. We examined the structure and functional role of amino acids 360–393 of putative transmembrane (TM) segment XI of SpNHE1. Structural analysis suggested that it had a helical propensity over amino acids 360–368, an extended region from 369–378 and was helical over amino acids 379–386. TM XI was sensitive to side chain alterations. Mutation of eight amino acids to alanine resulted in loss of one or both of LiCl or NaCl tolerance when re-introduced into SpNHE1 deficient S. pombe. Mutation of seven other amino acids had minor effects. Analysis of structure and functional mutations suggested that Glu361 may be involved in cation coordination on the cytoplasmic face of the protein with a negative charge in this position being important. His367, Ile371 and Gly372 were important in function. Ile371 may have important hydrophobic interactions with other residues and Gly372 may be important in maintaining an extended conformation. Several residues from Val377 to Leu384 are important in function possibly involved in hydrophobic interactions with other amino acids. We suggest that TM XI forms part of the ion translocation core of this Na+/H+ exchanger.
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Affiliation(s)
- Debajyoti Dutta
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Kyungsoo Shin
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Jan K Rainey
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.,Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada.
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130
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Adlimoghaddam A, O’Donnell MJ, Quijada-Rodriguez A, Weihrauch D. Sodium–hydrogen exchangers in the nematode Caenorhabditis elegans: investigations towards their potential role in hypodermal H+ excretion, Na+ uptake, and ammonia excretion, as well as acid–base balance. CAN J ZOOL 2017. [DOI: 10.1139/cjz-2016-0243] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cation/proton exchangers of the cation proton antiporter 1 (CPA1) subfamily (NHEs, SLC 9) play an important role in many physiological processes, including cell volume regulation, acid–base homeostasis, and ammonia excretion. The soil nematode Caenorhabditis elegans (Maupas, 1900) (N2, 1968) expresses nine paralogues (NHX-1 to NHX-9). The current study was undertaken to investigate the role of the cation/proton exchanger in hypodermal Na+ and H+ fluxes, as well in ammonia excretion processes. Measurements using SIET (scanning ion-selective electrode technique) showed that the hypodermis promotes H+ secretion and Na+ uptake. Inhibitory effects on fluxes were observed upon application of amiloride but not EIPA, suggesting that NHXs are not involved in the transport processes. In response to stress induced by starvation or exposure to 1 mmol·L−1 NH4Cl, pH 5.5, or pH 8.0, body pH stayed fairly constant, with changes in mRNA expression levels detected in intestinal NHX-2 and hypodermal NHX-3. In conclusion, the study suggest that hypodermal apically localized EIPA-sensitive Na+/H+ exchangers do not likely play a role in ammonia excretion and Na+ uptake in the hypodermis of C. elegans, whereas apical amiloride-sensitive Na+ channels seem to be involved not just in hypodermal Na+ uptake but indirectly also in NH4+ and H+ excretion.
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Affiliation(s)
- Aida Adlimoghaddam
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | | | | | - Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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131
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Hu MC, Bobulescu IA, Quiñones H, Gisler SM, Moe OW. Dopamine reduces cell surface Na +/H + exchanger-3 protein by decreasing NHE3 exocytosis and cell membrane recycling. Am J Physiol Renal Physiol 2017; 313:F1018-F1025. [PMID: 28768665 DOI: 10.1152/ajprenal.00251.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/14/2017] [Accepted: 07/24/2017] [Indexed: 01/06/2023] Open
Abstract
The intrarenal autocrine-paracrine dopamine (DA) system mediates a significant fraction of the natriuresis in response to a salt load. DA inhibits a number of Na+ transporters to effect sodium excretion, including the proximal tubule Na+/H+ exchanger-3 (NHE3). DA represent a single hormone that regulates NHE3 at multiple levels, including translation, degradation, endocytosis, and protein phosphorylation. Because cell surface NHE3 protein is determined by the balance between exocytotic insertion and endocytotic retrieval, we examined whether DA acutely affects the rate of NHE3 exocytosis in a cell culture model. DA inhibited NHE3 exocytosis at a dose-dependent manner with a half maximal around 10-6 M. The DA effect on NHE3 exocytosis was blocked by inhibition of protein kinase A and by brefeldin A, which inhibits endoplasmic reticulum-to-Golgi transport. NHE3 directly interacts with the ε-subunit of coatomer protein based on yeast-two-hybrid and coimmunoprecipitation. Because NHE3 has been shown to be recycled back to the cell membrane after endocytosis, we measured NHE3 recycling using a biochemical reinsertion assay and showed that reinsertion of NHE3 back to the membrane is also inhibited by DA. In conclusion, among the many mechanisms by which DA reduces apical membrane NHE3 and induces proximal tubule natriuresis, one additional mechanism is inhibition of exocytotic insertion and reinsertion of NHE3 in the apical cell surface.
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Affiliation(s)
- Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas; .,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - I Alexandru Bobulescu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Henry Quiñones
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Serge M Gisler
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Orson W Moe
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas; and.,Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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132
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Patiño-Ruiz M, Ganea C, Fendler K, Călinescu O. Competition is the basis of the transport mechanism of the NhaB Na+/H+ exchanger from Klebsiella pneumoniae. PLoS One 2017; 12:e0182293. [PMID: 28750048 PMCID: PMC5531510 DOI: 10.1371/journal.pone.0182293] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 07/14/2017] [Indexed: 11/18/2022] Open
Abstract
Na+/H+ exchange is essential for survival of all organisms, having a role in the regulation of the intracellular Na+ concentration, pH and cell volume. Furthermore, Na+/H+ exchangers were shown to be involved in the virulence of the bacterium Yersinia pestis, indicating they might be potential targets for novel antibiotic treatments. The model system for Na+/H+ exchangers is the NhaA transporter from Escherichia coli, EcNhaA. Therefore, the general transport mechanism of NhaA exchangers is currently well characterized. However, much less is known about NhaB exchangers, with only a limited number of studies available. The pathogen Klebsiella pneumoniae, which is a major source of nosocomial infection, possesses three electrogenic Na+/H+ exchangers, KpNhaA1, KpNhaA2 and KpNhaB, none of which have been previously investigated. Our aim in this study was to functionally characterize KpNhaB using solid supported membrane-based electrophysiology as the main investigation technique, and thus provide the first electrophysiological investigation of an NhaB Na+/H+ exchanger. We found that NhaB can be described by the same competition-based mechanism that was shown to be valid for electrogenic NhaA and NapA, and for electroneutral NhaP Na+/H+ exchangers. For comparison we also characterized the activity of KpNhaA1 and KpNhaA2 and found that the three exchangers have complementary activity profiles, which is likely a survival advantage for K. pneumoniae when faced with environments of different salinity and pH. This underlines their importance as potential antibiotic drug targets.
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Affiliation(s)
- Miyer Patiño-Ruiz
- Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Constanța Ganea
- Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- Department of Biophysics, “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania
| | - Klaus Fendler
- Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Octavian Călinescu
- Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- Department of Biophysics, “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania
- * E-mail:
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Expression and integrated network analyses revealed functional divergence of NHX-type Na +/H + exchanger genes in poplar. Sci Rep 2017; 7:2607. [PMID: 28572621 PMCID: PMC5453932 DOI: 10.1038/s41598-017-02894-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 04/19/2017] [Indexed: 12/21/2022] Open
Abstract
The Na+/H+ antiporters (NHXs) are secondary ion transporters to exchange H+ and transfer the Na+ or K+ across membrane, they play crucial roles during plant development and stress responses. To gain insight into the functional divergence of NHX genes in poplar, eight PtNHX were identified from Populus trichocarpa genome. PtNHXs containing 10 transmembrane helices (TMH) and a hydrophilic C-terminal domain, the TMH compose a hollow cylinder to provide the channel for Na+ and H+ transport. The expression patterns and cis-acting elements showed that all the PtNHXs were response to single or multiple stresses including drought, heat, cold, salinity, MV, and ABA. Both the co-expression network and protein-protein interaction network of PtNHXs implying their functional divergence. Interestingly, although PtNHX7 and PtNHX8 were generated by whole genome duplication event, they showed significant differences in expression pattern, protein structure, co-expressed genes, and interacted proteins. Only PtNHX7 interact with CBL and CIPK, indicating PtNHX7 is the primary NHX involved in CBL-CIPK pathway during salt stress responses. Natural variation analysis based on 549 P. trichocarpa individuals indicated the frequency of SNPs in PtNHX7 was significantly higher than other PtNHXs. Our findings provide new insights into the functional divergence of NHX genes in poplar.
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Padmanaban S, Czerny DD, Levin KA, Leydon AR, Su RT, Maugel TK, Zou Y, Chanroj S, Cheung AY, Johnson MA, Sze H. Transporters involved in pH and K+ homeostasis affect pollen wall formation, male fertility, and embryo development. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:3165-3178. [PMID: 28338823 PMCID: PMC5853877 DOI: 10.1093/jxb/erw483] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/01/2016] [Indexed: 05/20/2023]
Abstract
Flowering plant genomes encode multiple cation/H+ exchangers (CHXs) whose functions are largely unknown. AtCHX17, AtCHX18, and AtCHX19 are membrane transporters that modulate K+ and pH homeostasis and are localized in the dynamic endomembrane system. Loss of function reduced seed set, but the particular phase(s) of reproduction affected was not determined. Pollen tube growth and ovule targeting of chx17chx18chx19 mutant pollen appeared normal, but reciprocal cross experiments indicate a largely male defect. Although triple mutant pollen tubes reach ovules of a wild-type pistil and a synergid cell degenerated, half of those ovules were unfertilized or showed fertilization of the egg or central cell, but not both female gametes. Fertility could be partially compromised by impaired pollen tube and/or sperm function as CHX19 and CHX18 are expressed in the pollen tube and sperm cell, respectively. When fertilization was successful in self-pollinated mutants, early embryo formation was retarded compared with embryos from wild-type ovules receiving mutant pollen. Thus CHX17 and CHX18 proteins may promote embryo development possibly through the endosperm where these genes are expressed. The reticulate pattern of the pollen wall was disorganized in triple mutants, indicating perturbation of wall formation during male gametophyte development. As pH and cation homeostasis mediated by AtCHX17 affect membrane trafficking and cargo delivery, these results suggest that male fertility, sperm function, and embryo development are dependent on proper cargo sorting and secretion that remodel cell walls, plasma membranes, and extracellular factors.
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Affiliation(s)
- Senthilkumar Padmanaban
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Daniel D Czerny
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Kara A Levin
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Alexander R Leydon
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Robert T Su
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
| | - Timothy K Maugel
- Laboratory for Biological Ultrastructure, University of Maryland, College Park, MD, USA
| | - Yanjiao Zou
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
| | - Salil Chanroj
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
- Department of Biotechnology, Burapha University, Chon-Buri, Thailand
| | - Alice Y Cheung
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
| | - Mark A Johnson
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
| | - Heven Sze
- Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD, USA
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
- Maryland Agricultural Experiment Station, University of Maryland, College Park, MD, USA
- Correspondence:
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135
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Larkum AWD, Davey PA, Kuo J, Ralph PJ, Raven JA. Carbon-concentrating mechanisms in seagrasses. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:3773-3784. [PMID: 28911056 DOI: 10.1093/jxb/erx206] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Seagrasses are unique angiosperms that carry out growth and reproduction submerged in seawater. They occur in at least three families of the Alismatales. All have chloroplasts mainly in the cells of the epidermis. Living in seawater, the supply of inorganic carbon (Ci) to the chloroplasts is diffusion limited, especially under unstirred conditions. Therefore, the supply of CO2 and bicarbonate across the diffusive boundary layer on the outer side of the epidermis is often a limiting factor. Here we discuss the evidence for mechanisms that enhance the uptake of Ci into the epidermal cells. Since bicarbonate is plentiful in seawater, a bicarbonate pump might be expected; however, the evidence for such a pump is not strongly supported. There is evidence for a carbonic anhydrase outside the outer plasmalemma. This, together with evidence for an outward proton pump, suggests the possibility that local acidification leads to enhanced concentrations of CO2 adjacent to the outer tangential epidermal walls, which enhances the uptake of CO2, and this could be followed by a carbon-concentrating mechanism (CCM) in the cytoplasm and/or chloroplasts. The lines of evidence for such an epidermal CCM are discussed, including evidence for special 'transfer cells' in some but not all seagrass leaves in the tangential inner walls of the epidermal cells. It is concluded that seagrasses have a CCM but that the case for concentration of CO2 at the site of Rubisco carboxylation is not proven.
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Affiliation(s)
- Anthony William D Larkum
- Plant Functional Biology and Global Climate Change Cluster, University of Technology Sydney, NSW 2009, Australia
| | - Peter A Davey
- Plant Functional Biology and Global Climate Change Cluster, University of Technology Sydney, NSW 2009, Australia
| | - John Kuo
- Electron Microscope Centre, University of Western Australia, WA 6900, Australia
| | - Peter J Ralph
- Plant Functional Biology and Global Climate Change Cluster, University of Technology Sydney, NSW 2009, Australia
| | - John A Raven
- Plant Functional Biology and Global Climate Change Cluster, University of Technology Sydney, NSW 2009, Australia
- University of Dundee at JHI, Invergowrie, Dundee, UK
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136
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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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137
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Ma Y, Augé RM, Dong C, Cheng Z(M. Increased salt tolerance with overexpression of cation/proton antiporter 1 genes: a meta-analysis. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:162-173. [PMID: 27383431 PMCID: PMC5258863 DOI: 10.1111/pbi.12599] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 06/21/2016] [Accepted: 06/23/2016] [Indexed: 05/05/2023]
Abstract
Cation/proton antiporter 1 (CPA1) genes encode cellular Na+ /H+ exchanger proteins, which act to adjust ionic balance. Overexpression of CPA1s can improve plant performance under salt stress. However, the diversified roles of the CPA1 family and the various parameters used in evaluating transgenic plants over-expressing CPA1s make it challenging to assess the complex functions of CPA1s and their physiological mechanisms in salt tolerance. Using meta-analysis, we determined how overexpression of CPA1s has influenced several plant characteristics involved in response and resilience to NaCl stress. We also evaluated experimental variables that favour or reduce CPA1 effects in transgenic plants. Viewed across studies, overexpression of CPA1s has increased the magnitude of 10 of the 19 plant characteristics examined, by 25% or more. Among the ten moderating variables, several had substantial impacts on the extent of CPA1 influence: type of culture media, donor and recipient type and genus, and gene family. Genes from monocotyledonous plants stimulated root K+ , root K+ /Na+ , total chlorophyll, total dry weight and root length much more than genes from dicotyledonous species. Genes transformed to or from Arabidopsis have led to smaller CPA1-induced increases in plant characteristics than genes transferred to or from other genera. Heterogeneous expression of CPA1s led to greater increases in leaf chlorophyll and root length than homologous expression. These findings should help guide future investigations into the function of CPA1s in plant salt tolerance and the use of genetic engineering for breeding of resistance.
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Affiliation(s)
- Yuan‐Chun Ma
- Institute of HorticultureJiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic ImprovementNanjingJiangsuChina
- College of HorticultureNanjing Agricultural UniversityNanjingJiangsuChina
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - Robert M. Augé
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
| | - Chao Dong
- College of HorticultureNanjing Agricultural UniversityNanjingJiangsuChina
| | - Zong‐Ming (Max) Cheng
- College of HorticultureNanjing Agricultural UniversityNanjingJiangsuChina
- Department of Plant SciencesUniversity of TennesseeKnoxvilleTNUSA
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138
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Beydoun R, Hamood MA, Gomez Zubieta DM, Kondapalli KC. Na +/H + Exchanger 9 Regulates Iron Mobilization at the Blood-Brain Barrier in Response to Iron Starvation. J Biol Chem 2017; 292:4293-4301. [PMID: 28130443 DOI: 10.1074/jbc.m116.769240] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/24/2017] [Indexed: 12/21/2022] Open
Abstract
Iron is essential for brain function, with loss of iron homeostasis in the brain linked to neurological diseases ranging from rare syndromes to more common disorders, such as Parkinson's and Alzheimer's diseases. Iron entry into the brain is regulated by the blood-brain barrier (BBB). Molecular mechanisms regulating this transport are poorly understood. Using an in vitro model of the BBB, we identify NHE9, an endosomal cation/proton exchanger, as a novel regulator of this system. Human brain microvascular endothelial cells (hBMVECs) that constitute the BBB receive brain iron status information via paracrine signals from ensheathing astrocytes. In hBMVECs, we show that NHE9 expression is up-regulated very early in a physiological response invoked by paracrine signals from iron-starved astrocytes. Ectopic expression of NHE9 in hBMVECs without external cues induced up-regulation of the transferrin receptor (TfR) and down-regulation of ferritin, leading to an increase in iron uptake. Mechanistically, we demonstrate that NHE9 localizes to recycling endosomes in hBMVECs where it raises the endosomal pH. The ensuing alkalization of the endosomal lumen increased translocation of TfRs to the hBMVEC membrane. TfRs on the membrane were previously shown to facilitate both recycling-dependent and -independent iron uptake. We propose that NHE9 regulates TfR-dependent, recycling-independent iron uptake in hBMVECs by fine-tuning the endosomal pH in response to paracrine signals and is therefore an important regulator in iron mobilization pathway at the BBB.
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Affiliation(s)
- Rami Beydoun
- From the Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
| | - Mohamed A Hamood
- From the Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
| | - Daniela M Gomez Zubieta
- From the Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
| | - Kalyan C Kondapalli
- From the Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, Michigan 48128
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139
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Wu Y, Meng K, Liang X. Distinct patterns of natural selection in Na +/H + antiporter genes in Populus euphratica and Populus pruinosa. Ecol Evol 2016; 7:82-91. [PMID: 28070277 PMCID: PMC5214168 DOI: 10.1002/ece3.2639] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/17/2016] [Accepted: 10/19/2016] [Indexed: 01/28/2023] Open
Abstract
Salt tolerance genes constitute an important class of loci in plant genomes. Little is known about the extent to which natural selection in saline environments has acted upon these loci, and what types of nucleotide diversity such selection has given rise to. Here, we surveyed genetic diversity in three types of Na+/H+ antiporter gene (SOS, NhaD, and NHX, belonging to the cation/proton antiporter 1 family), which have well‐characterized essential roles in plant salt tolerance. Ten Na+/H+ antiporter genes and 16 neutral loci randomly selected as controls were sequenced from 17 accessions of two closely related members of the genus Populus, Populus euphratica and Populus pruinosa, section Turanga, which are native to northwest China. The results show that salt tolerance genes are common targets of natural selection in P. euphratica and P. pruinosa. Moreover, the patterns of nucleotide variation across the three types of Na+/H+ antiporter gene are distinctly different in these two closely related Populus species, and gene flow from P. pruinosa to P. euphratica is highly restricted. Our results suggest that natural selection played an important role in shaping the current distinct patterns of Na+/H+ antiporter genes, resulting in adaptive evolution in P. euphratica and P. pruinosa.
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Affiliation(s)
- Yuxia Wu
- State Key Laboratory of Grassland Agro-Ecosystem School of Life Sciences Lanzhou University Lanzhou Gansu China
| | - Kuibin Meng
- State Key Laboratory of Grassland Agro-Ecosystem School of Life Sciences Lanzhou University Lanzhou Gansu China
| | - Xiaohui Liang
- State Key Laboratory of Grassland Agro-Ecosystem School of Life Sciences Lanzhou University Lanzhou Gansu China
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140
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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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141
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Călinescu O, Linder M, Wöhlert D, Yildiz Ö, Kühlbrandt W, Fendler K. Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi. J Biol Chem 2016; 291:26786-26793. [PMID: 27821589 PMCID: PMC5207186 DOI: 10.1074/jbc.m116.761080] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/02/2016] [Indexed: 01/04/2023] Open
Abstract
Na+/H+ antiporters in the CPA1 branch of the cation proton antiporter family drive the electroneutral exchange of H+ against Na+ ions and ensure pH homeostasis in eukaryotic and prokaryotic organisms. Although their transport cycle is overall electroneutral, specific partial reactions are electrogenic. Here, we present an electrophysiological study of the PaNhaP Na+/H+ antiporter from Pyrococcus abyssi reconstituted into liposomes. Positive transient currents were recorded upon addition of Na+ to PaNhaP proteoliposomes, indicating a reaction where positive charge is rapidly displaced into the proteoliposomes with a rate constant of k >200 s-1 We attribute the recorded currents to an electrogenic reaction that includes Na+ binding and possibly occlusion. Subsequently, positive charge is transported out of the cell associated with H+ binding, so that the overall reaction is electroneutral. We show that the differences in pH profile and Na+ affinity of PaNhaP and the related MjNhaP1 from Methanocaldococcus jannaschii can be attributed to an additional negatively charged glutamate residue in PaNhaP. The results are discussed in the context of the physiological function of PaNhaP and other microbial Na+/H+ exchangers. We propose that both, electroneutral and electrogenic Na+/H+ antiporters, represent a carefully tuned self-regulatory system, which drives the cytoplasmic pH back to neutral after any deviation.
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Affiliation(s)
- Octavian Călinescu
- From the Departments of Biological Chemistry and.,the Department of Biophysics, "Carol Davila" University of Medicine and Pharmacy, 050474 Bucharest, Romania
| | - Mark Linder
- From the Departments of Biological Chemistry and.,Structural Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany and
| | - David Wöhlert
- Structural Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany and
| | - Özkan Yildiz
- Structural Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany and
| | - Werner Kühlbrandt
- Structural Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany and
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142
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Abstract
Several members of the SLC9A family of Na+/H+ exchangers are expressed in the gut, with varying expression patterns and cellular localization. Not only do they participate in the regulation of basic epithelial cell functions, including control of transepithelial Na+ absorption, intracellular pH (pH i ), cell volume, and nutrient absorption, but also in cellular proliferation, migration, and apoptosis. Additionally, they modulate the extracellular milieu in order to facilitate other nutrient absorption and to regulate the intestinal microbial microenvironment. Na+/H+ exchangers are frequent targets of inhibition in gastrointestinal pathologies, either by intrinsic factors (e.g. bile acids, inflammatory mediators) or infectious agents and associated microbial toxins. Based on emerging evidence, disruption of NHE activity via impaired expression or function of respective isoforms may contribute not only to local and systemic electrolyte imbalance, but also to the disease severity via multiple mechanisms. Here, we review the current state of knowledge about the roles Na+/H+ exchangers play in the pathogenesis of disorders of diverse origin and affecting a range of GI tissues.
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Affiliation(s)
- Michael A. Gurney
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona, Tucson, Arizona
| | - Daniel Laubitz
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona, Tucson, Arizona
| | - Fayez K. Ghishan
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona, Tucson, Arizona
| | - Pawel R. Kiela
- Department of Pediatrics, Steele Children’s Research Center, University of Arizona, Tucson, Arizona,Department of Immunobiology, University of Arizona, Tucson, Arizona,Correspondence Address correspondence to: Pawel R. Kiela, DVM, PhD, Department of Pediatrics, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724. fax: (520) 626-4141.Department of Pediatrics, University of Arizona1501 North Campbell AvenueTucsonArizona 85724
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143
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Abstract
The structures of transport proteins have been steadily revealed in the last few decades, and yet the conversion of this information into molecular-level understanding of their function is still lagging behind. In this study, we try to elucidate how the action of the archaeal sodium/proton antiporter MjNhaP1 depends on its structure-energy relationship. To this end, we calculate the binding energies of its substrates and evaluate the conformational change barrier, focusing on the rotation of the catalytic residue D161. We find that sodium ions and protons compete against a common binding site and that the accessibility of this binding site is restricted to either the inside or outside of the cell. We suggest that the rotation of D161 χ1 angle correlates with the conformational change and is energetically unfavorable when D161 does not bind any substrate. This restriction ensures coupling between the sodium ions and the protons, allowing MjNhaP1 and probably other similar transporters to exchange substrates with minimal leak. Using Monte Carlo simulations we demonstrate the feasibility of our model. Overall we present a complete picture that reproduces the electroneutral (at 1:1 substrate ratio) and coupled transport activity of MjNhaP1 including the energetic basis for the criteria provided by Jardetzky half a century ago.
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Affiliation(s)
- Raphael Alhadeff
- Department of Chemistry, University of Southern California , SGM 418, 3620 McClintock Avenue, Los Angeles, California 90089, United States
| | - Arieh Warshel
- Department of Chemistry, University of Southern California , SGM 418, 3620 McClintock Avenue, Los Angeles, California 90089, United States
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144
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Morino M, Ogoda S, Krulwich TA, Ito M. Differences in the phenotypic effects of mutations in homologous MrpA and MrpD subunits of the multi-subunit Mrp-type Na +/H + antiporter. Extremophiles 2016; 21:51-64. [PMID: 27709304 DOI: 10.1007/s00792-016-0877-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 09/24/2016] [Indexed: 10/20/2022]
Abstract
Mrp antiporters are the sole antiporters in the Cation/Proton Antiporter 3 family of transporter databases because of their unusual structural complexity, 6-7 hydrophobic proteins that function as a hetero-oligomeric complex. The two largest and homologous subunits, MrpA and MrpD, are essential for antiport activity and have direct roles in ion transport. They also show striking homology with proton-conducting, membrane-embedded Nuo subunits of respiratory chain complex I of bacteria, e.g., Escherichia coli. MrpA has the closest homology to the complex I NuoL subunit and MrpD has the closest homology to the complex I NuoM and N subunits. Here, introduction of mutations in MrpD, in residues that are also present in MrpA, led to defects in antiport function and/or complex formation. No significant phenotypes were detected in strains with mutations in corresponding residues of MrpA, but site-directed changes in the C-terminal region of MrpA had profound effects, showing that the MrpA C-terminal region has indispensable roles in antiport function. The results are consistent with a divergence in adaptations that support the roles of MrpA and MrpD in secondary antiport, as compared to later adaptations supporting homologs in primary proton pumping by the respiratory chain complex I.
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Affiliation(s)
- Masato Morino
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.,, 573-13 Kamitanui, Tarnaki-cho, Watarai-gun, Mie, 519-0417, Japan
| | - Shinichiro Ogoda
- Faculty of Life Sciences, Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma, 374-0193, Japan
| | - Terry Ann Krulwich
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Masahiro Ito
- Faculty of Life Sciences, Graduate School of Life Sciences, Toyo University, Oura-gun, Gunma, 374-0193, Japan. .,Bio-Nano Electronics Research Center, Toyo University, Kawagoe, Saitama, 350-0815, Japan.
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145
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Rackelmann N, Matter H, Englert H, Follmann M, Maier T, Weston J, Arndt P, Heyse W, Mertsch K, Wirth K, Bialy L. Discovery and Optimization of 1-Phenoxy-2-aminoindanes as Potent, Selective, and Orally Bioavailable Inhibitors of the Na +/H + Exchanger Type 3 (NHE3). J Med Chem 2016; 59:8812-8829. [PMID: 27606885 DOI: 10.1021/acs.jmedchem.6b00624] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The design, synthesis, and structure-activity relationship of 1-phenoxy-2-aminoindanes as inhibitors of the Na+/H+ exchanger type 3 (NHE3) are described based on a hit from high-throughput screening (HTS). The chemical optimization resulted in the discovery of potent, selective, and orally bioavailable NHE3 inhibitors with 13d as best compound, showing high in vitro permeability and lacking CYP2D6 inhibition as main optimization parameters. Aligning 1-phenoxy-2-aminoindanes onto the X-ray structure of 13d then provided 3D-QSAR models for NHE3 inhibition capturing guidelines for optimization. These models showed good correlation coefficients and allowed for activity estimation. In silico ADMET models for Caco-2 permeability and CYP2D6 inhibition were also successfully applied for this series. Moreover, docking into the CYP2D6 X-ray structure provided a reliable alignment for 3D-QSAR models. Finally 13d, renamed as SAR197, was characterized in vitro and by in vivo pharmacokinetic (PK) and pharmacological studies to unveil its potential for reduction of obstructive sleep apneas.
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Affiliation(s)
- Nils Rackelmann
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Hans Matter
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Heinrich Englert
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Markus Follmann
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Thomas Maier
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - John Weston
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Petra Arndt
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Winfried Heyse
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Katharina Mertsch
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Klaus Wirth
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
| | - Laurent Bialy
- Sanofi-Aventis Deutschland GmbH, R&D , D-65926, Frankfurt am Main, Germany
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Ilie A, Gao AYL, Reid J, Boucher A, McEwan C, Barrière H, Lukacs GL, McKinney RA, Orlowski J. A Christianson syndrome-linked deletion mutation (∆(287)ES(288)) in SLC9A6 disrupts recycling endosomal function and elicits neurodegeneration and cell death. Mol Neurodegener 2016; 11:63. [PMID: 27590723 PMCID: PMC5010692 DOI: 10.1186/s13024-016-0129-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 08/27/2016] [Indexed: 01/19/2023] Open
Abstract
Background Christianson Syndrome, a recently identified X-linked neurodevelopmental disorder, is caused by mutations in the human gene SLC9A6 encoding the recycling endosomal alkali cation/proton exchanger NHE6. The patients have pronounced limitations in cognitive ability, motor skills and adaptive behaviour. However, the mechanistic basis for this disorder is poorly understood as few of the more than 20 mutations identified thus far have been studied in detail. Methods Here, we examined the molecular and cellular consequences of a 6 base-pair deletion of amino acids Glu287 and Ser288 (∆ES) in the predicted seventh transmembrane helix of human NHE6 expressed in established cell lines (CHO/AP-1, HeLa and neuroblastoma SH-SY5Y) and primary cultures of mouse hippocampal neurons by measuring levels of protein expression, stability, membrane trafficking, endosomal function and cell viability. Results In the cell lines, immunoblot analyses showed that the nascent mutant protein was properly synthesized and assembled as a homodimer, but its oligosaccharide maturation and half-life were markedly reduced compared to wild-type (WT) and correlated with enhanced ubiquitination leading to both proteasomal and lysosomal degradation. Despite this instability, a measurable fraction of the transporter was correctly sorted to the plasma membrane. However, the rates of clathrin-mediated endocytosis of the ∆ES mutant as well as uptake of companion vesicular cargo, such as the ligand-bound transferrin receptor, were significantly reduced and correlated with excessive endosomal acidification. Notably, ectopic expression of ∆ES but not WT induced apoptosis when examined in AP-1 cells. Similarly, in transfected primary cultures of mouse hippocampal neurons, membrane trafficking of the ∆ES mutant was impaired and elicited marked reductions in total dendritic length, area and arborization, and triggered apoptotic cell death. Conclusions These results suggest that loss-of-function mutations in NHE6 disrupt recycling endosomal function and trafficking of cargo which ultimately leads to neuronal degeneration and cell death in Christianson Syndrome. Electronic supplementary material The online version of this article (doi:10.1186/s13024-016-0129-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alina Ilie
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Andy Y L Gao
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Jonathan Reid
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Annie Boucher
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Cassandra McEwan
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Hervé Barrière
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada
| | - R Anne McKinney
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - John Orlowski
- Department of Physiology, McGill University, Bellini Life Sciences Bldg., Rm, 166, 3649 Promenade Sir-William-Osler, Montreal, QC, H3G 0B1, Canada.
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147
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Holmes RS, Spradling-Reeves KD, Cox LA. Evolution of Vertebrate Solute Carrier Family 9B Genes and Proteins ( SLC9B): Evidence for a Marsupial Origin for Testis Specific SLC9B1 from an Ancestral Vertebrate SLC9B2 Gene. ACTA ACUST UNITED AC 2016; 4. [PMID: 28868326 DOI: 10.4172/2329-9002.1000167] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
SLC9B genes and proteins are members of the sodium/lithium hydrogen antiporter family which function as solute exchangers within cellular membranes of mammalian tissues. SLC9B2 and SLC9B1 amino acid sequences and structures and SLC9B-like gene locations were examined using bioinformatic data from several vertebrate genome projects. Vertebrate SLC9B2 sequences shared 56-98% identity as compared with ∼50% identities with mammalian SLC9B1 sequences. Sequence alignments, key amino acid residues and conserved predicted transmembrane structures were also studied. Mammalian SLC9B2 and SLC9B1 genes usually contained 11 or 12 coding exons with differential tissue expression patterns: SLC9B2, broad tissue distribution; and SLC9B1, being testis specific. Transcription factor binding sites and CpG islands within the human SLC9B2 and SLC9B1 gene promoters were identified. Phylogenetic analyses suggested that SLC9B1 originated in an ancestral marsupial genome from a SLC9B2 gene duplication event.
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Affiliation(s)
- Roger S Holmes
- Eskitis Institute for Drug Discovery and School of Natural Sciences, Griffith University, Nathan, QLD, Australia.,Department of Genetics and Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Kimberly D Spradling-Reeves
- Department of Genetics and Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, Texas, USA
| | - Laura A Cox
- Department of Genetics and Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, Texas, USA
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148
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Nieves-Cordones M, Al Shiblawi FR, Sentenac H. Roles and Transport of Sodium and Potassium in Plants. Met Ions Life Sci 2016; 16:291-324. [PMID: 26860305 DOI: 10.1007/978-3-319-21756-7_9] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The two alkali cations Na(+) and K(+) have similar relative abundances in the earth crust but display very different distributions in the biosphere. In all living organisms, K(+) is the major inorganic cation in the cytoplasm, where its concentration (ca. 0.1 M) is usually several times higher than that of Na(+). Accumulation of Na(+) at high concentrations in the cytoplasm results in deleterious effects on cell metabolism, e.g., on photosynthetic activity in plants. Thus, Na(+) is compartmentalized outside the cytoplasm. In plants, it can be accumulated at high concentrations in vacuoles, where it is used as osmoticum. Na(+) is not an essential element in most plants, except in some halophytes. On the other hand, it can be a beneficial element, by replacing K(+) as vacuolar osmoticum for instance. In contrast, K(+) is an essential element. It is involved in electrical neutralization of inorganic and organic anions and macromolecules, pH homeostasis, control of membrane electrical potential, and the regulation of cell osmotic pressure. Through the latter function in plants, it plays a role in turgor-driven cell and organ movements. It is also involved in the activation of enzymes, protein synthesis, cell metabolism, and photosynthesis. Thus, plant growth requires large quantities of K(+) ions that are taken up by roots from the soil solution, and then distributed throughout the plant. The availability of K(+) ions in the soil solution, slowly released by soil particles and clays, is often limiting for optimal growth in most natural ecosystems. In contrast, due to natural salinity or irrigation with poor quality water, detrimental Na(+) concentrations, toxic for all crop species, are present in many soils, representing 6 % to 10 % of the earth's land area. Three families of ion channels (Shaker, TPK/KCO, and TPC) and 3 families of transporters (HAK, HKT, and CPA) have been identified so far as contributing to K(+) and Na(+) transport across the plasmalemma and internal membranes, with high or low ionic selectivity. In the model plant Arabidopsis thaliana, these families gather at least 70 members. Coordination of the activities of these systems, at the cell and whole plant levels, ensures plant K(+) nutrition, use of Na(+) as a beneficial element, and adaptation to saline conditions.
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Affiliation(s)
- Manuel Nieves-Cordones
- Laboratory of Plant Biochemistry and Molecular Physiology, UMR BPMP CNRS/INRA/MontpellierSupAgro, University of Montpellier, INRA, Place Viala, F-34060, Montpellier cedex 1, France
| | - Fouad Razzaq Al Shiblawi
- Laboratory of Plant Biochemistry and Molecular Physiology, UMR BPMP CNRS/INRA/MontpellierSupAgro, University of Montpellier, INRA, Place Viala, F-34060, Montpellier cedex 1, France
| | - Hervé Sentenac
- Laboratory of Plant Biochemistry and Molecular Physiology, UMR BPMP CNRS/INRA/MontpellierSupAgro, University of Montpellier, INRA, Place Viala, F-34060, Montpellier cedex 1, France.
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149
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Zhu J, Ying SH, Feng MG. The Na + /H + antiporter Nhx1 controls vacuolar fusion indispensible for life cycles in vitro and in vivo in a fungal insect pathogen. Environ Microbiol 2016; 18:3884-3895. [PMID: 27112237 DOI: 10.1111/1462-2920.13359] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 04/21/2016] [Indexed: 01/10/2023]
Abstract
The sole Na+ /H+ antiporter Nhx1 has been generally unexplored in filamentous fungi. We characterized Nhx1 in the entomopathogenic fungus Beauveria bassiana. An eGFP-tagged Nhx1 fusion accumulated in small punctuate structures, presumably endosomal and trans-Golgi network compartments, between septum and tubular vacuole of each wild-type cell stained with a vacuole-specific dye. Deletion of nhx1 resulted in significant acidification and severe fusion defect in vacuoles, which were fragmented and distinct from large or tubular wild-type vacuoles. The deletion also caused a drastic reduction in aerial conidiation or submerged blastospore production and more severe defect in vegetative growth than in conidial germination. The Δnhx1 mutant became more sensitive to high osmolarity, heat shock and several metal ions during growth but its conidia showed increased UV-B tolerance. Intriguingly, Δnhx1 was unable to infect a model insect through cuticle penetration or intrahaemocoel injection because it produced much less biomass and cuticle-degrading enzymes in a minimal broth and failed to form blastospores in the insect haemolymph. All changes were completely or largely restored by targeted nhx1 complementation. Our results provide novel insight into an indispensability of Nhx1 for not only vacuolar fusion but also life cycles in vitro and in vivo in B. bassiana.
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Affiliation(s)
- Jing Zhu
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
| | - Sheng-Hua Ying
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
| | - Ming-Guang Feng
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China
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150
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Czerny DD, Padmanaban S, Anishkin A, Venema K, Riaz Z, Sze H. Protein architecture and core residues in unwound α-helices provide insights to the transport function of plant AtCHX17. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1983-1998. [PMID: 27179641 DOI: 10.1016/j.bbamem.2016.05.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/13/2016] [Accepted: 05/08/2016] [Indexed: 01/27/2023]
Abstract
Using Arabidopsis thaliana AtCHX17 as an example, we combine structural modeling and mutagenesis to provide insights on its protein architecture and transport function which is poorly characterized. This approach is based on the observation that protein structures are significantly more conserved in evolution than linear sequences, and mechanistic similarities among diverse transporters are emerging. Two homology models of AtCHX17 were obtained that show a protein fold similar to known structures of bacterial Na(+)/H(+) antiporters, EcNhaA and TtNapA. The distinct secondary and tertiary structure models highlighted residues at positions potentially important for CHX17 activity. Mutagenesis showed that asparagine-N200 and aspartate-D201 inside transmembrane5 (TM5), and lysine-K355 inside TM10 are critical for AtCHX17 activity. We reveal previously unrecognized threonine-T170 and lysine-K383 as key residues at unwound regions in the middle of TM4 and TM11 α-helices, respectively. Mutation of glutamate-E111 located near the membrane surface inhibited AtCHX17 activity, suggesting a role in pH sensing. The long carboxylic tail of unknown purpose has an alternating β-sheet and α-helix secondary structure that is conserved in prokaryote universal stress proteins. These results support the overall architecture of AtCHX17 and identify D201, N200 and novel residues T170 and K383 at the functional core which likely participates in ion recognition, coordination and/or translocation, similar to characterized cation/H(+) exchangers. The core of AtCHX17 models according to EcNhaA and TtNapA templates faces inward and outward, respectively, which may reflect two conformational states of the alternating access transport mode for proteins belonging to the plant CHX family.
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Affiliation(s)
- Daniel D Czerny
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Senthilkumar Padmanaban
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Kees Venema
- Dpto de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, c/. Profesor Albareda 1, 18008Granada, Spain
| | - Zoya Riaz
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Heven Sze
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA; Maryland Agricultural Experiment Station, Department of Plant Science and Landscape Architecture (HS), University of Maryland, College Park, MD 20742, USA.
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