1
|
Zimmer AM. Ammonia excretion by the fish gill: discoveries and ideas that shaped our current understanding. J Comp Physiol B 2024:10.1007/s00360-024-01561-5. [PMID: 38849577 DOI: 10.1007/s00360-024-01561-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 03/06/2024] [Accepted: 05/15/2024] [Indexed: 06/09/2024]
Abstract
The fish gill serves many physiological functions, among which is the excretion of ammonia, the primary nitrogenous waste in most fishes. Although it is the end-product of nitrogen metabolism, ammonia serves many physiological functions including acting as an acid equivalent and as a counter-ion in mechanisms of ion regulation. Our current understanding of the mechanisms of ammonia excretion have been influenced by classic experimental work, clever mechanistic approaches, and modern molecular and genetic techniques. In this review, I will overview the history of the study of ammonia excretion by the gills of fishes, highlighting the important advancements that have shaped this field with a nearly 100-year history. The developmental and evolutionary implications of an ammonia and gill-dominated nitrogen regulation strategy in most fishes will also be discussed. Throughout the review, I point to areas in which more work is needed to push forward this field of research that continues to produce novel insights and discoveries that will undoubtedly shape our overall understanding of fish physiology.
Collapse
Affiliation(s)
- Alex M Zimmer
- Department of Biological Sciences, University of New Brunswick, 100 Tucker Park Road, Saint John, Saint John, New Brunswick, E2L 4L5, Canada.
| |
Collapse
|
2
|
Quijada-Rodriguez AR, Fehsenfeld S, Marini AM, Wilson JM, Nash MT, Sachs M, Towle DW, Weihrauch D. Branchial CO 2 and ammonia excretion in crustaceans: Involvement of an apical Rhesus-like glycoprotein. Acta Physiol (Oxf) 2024; 240:e14078. [PMID: 38205922 DOI: 10.1111/apha.14078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 10/13/2023] [Accepted: 12/14/2023] [Indexed: 01/12/2024]
Abstract
AIM To determine whether the crustacean Rh1 protein functions as a dual CO2 /ammonia transporter and investigate its role in branchial ammonia excretion and acid-base regulation. METHODS Sequence analysis of decapod Rh1 proteins was used to determine the conservation of amino acid residues putatively involved in ammonia transport and CO2 binding in human and bacterial Rh proteins. Using the Carcinus maenas Rh1 protein (CmRh1) as a representative of decapod Rh1 proteins, we test the ammonia and CO2 transport capabilities of CmRh1 through heterologous expression in yeast and Xenopus oocytes coupled with site-directed mutagenesis. Quantitative PCR was used to assess the distribution of CmRh1 mRNA in various tissues. Western blotting was used to assess CmRh1 protein expression changes in response to high environmental ammonia and CO2 . Further, immunohistochemistry was used to assess sub-cellular localization of CmRh1 and a membrane-bound carbonic anhydrase (CmCAg). RESULTS Sequence analysis of decapod Rh proteins revealed high conservation of several amino acid residues putatively involved in conducting ammonia transport and CO2 binding. Expression of CmRh1 in Xenopus oocytes enhanced both ammonia and CO2 transport which was nullified in CmRh1 D180N mutant oocytes. Transport of the ammonia analog methylamine by CmRh1 is dependent on both ionized and un-ionized ammonia/methylamine species. CmRh1 was co-localized with CmCAg to the apical membrane of the crustacean gill and only experienced decreased protein expression in the anterior gills when exposed to high environmental ammonia. CONCLUSION CmRh1 is the first identified apical transporter-mediated route for ammonia and CO2 excretion in the crustacean gill. Our findings shed further light on the potential universality of dual ammonia and CO2 transport capacity of Rhesus glycoproteins in both vertebrates and invertebrates.
Collapse
Affiliation(s)
- Alex R Quijada-Rodriguez
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - Sandra Fehsenfeld
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
- Département de biologie, chimie et géographie, Université du Québec à Rimouski, Rimouski, Quebec, Canada
| | - Anna-Maria Marini
- Biology of Membrane Transport Laboratory, Molecular Biology Department, Université Libre de Bruxelles, Bruxelles, Belgium
- WELBIO, Wavre, Belgium
| | - Jonathan M Wilson
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - Mikyla T Nash
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Maria Sachs
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - David W Towle
- Mount Desert Island Biological Laboratory, Salisbury Cove, Maine, USA
| | - Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| |
Collapse
|
3
|
Williamson G, Bizior A, Harris T, Pritchard L, Hoskisson P, Javelle A. Biological ammonium transporters from the Amt/Mep/Rh superfamily: mechanism, energetics, and technical limitations. Biosci Rep 2024; 44:BSR20211209. [PMID: 38131184 PMCID: PMC10794816 DOI: 10.1042/bsr20211209] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/12/2023] [Accepted: 12/21/2023] [Indexed: 12/23/2023] Open
Abstract
The exchange of ammonium across cellular membranes is a fundamental process in all domains of life and is facilitated by the ubiquitous Amt/Mep/Rh transporter superfamily. Remarkably, despite a high structural conservation in all domains of life, these proteins have gained various biological functions during evolution. It is tempting to hypothesise that the physiological functions gained by these proteins may be explained at least in part by differences in the energetics of their translocation mechanisms. Therefore, in this review, we will explore our current knowledge of energetics of the Amt/Mep/Rh family, discuss variations in observations between different organisms, and highlight some technical drawbacks which have hampered effects at mechanistic characterisation. Through the review, we aim to provide a comprehensive overview of current understanding of the mechanism of transport of this unique and extraordinary Amt/Mep/Rh superfamily of ammonium transporters.
Collapse
Affiliation(s)
- Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Adriana Bizior
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Leighton Pritchard
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Paul A. Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, U.K
| |
Collapse
|
4
|
Williamson G, Harris T, Bizior A, Hoskisson PA, Pritchard L, Javelle A. Biological ammonium transporters: evolution and diversification. FEBS J 2024. [PMID: 38265636 DOI: 10.1111/febs.17059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/14/2023] [Accepted: 01/09/2024] [Indexed: 01/25/2024]
Abstract
Although ammonium is the preferred nitrogen source for microbes and plants, in animal cells it is a toxic product of nitrogen metabolism that needs to be excreted. Thus, ammonium movement across biological membranes, whether for uptake or excretion, is a fundamental and ubiquitous biological process catalysed by the superfamily of the Amt/Mep/Rh transporters. A remarkable feature of the Amt/Mep/Rh family is that they are ubiquitous and, despite sharing low amino acid sequence identity, are highly structurally conserved. Despite sharing a common structure, these proteins have become involved in a diverse range of physiological process spanning all domains of life, with reports describing their involvement in diverse biological processes being published regularly. In this context, we exhaustively present their range of biological roles across the domains of life and after explore current hypotheses concerning their evolution to help to understand how and why the conserved structure fulfils diverse physiological functions.
Collapse
Affiliation(s)
- Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Adriana Bizior
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Paul Alan Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Leighton Pritchard
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| |
Collapse
|
5
|
Habenicht T, Weidenbach K, Velazquez-Campoy A, Buey RM, Balsera M, Schmitz RA. Small protein mediates inhibition of ammonium transport in Methanosarcina mazei-an ancient mechanism? Microbiol Spectr 2023; 11:e0281123. [PMID: 37909787 PMCID: PMC10714827 DOI: 10.1128/spectrum.02811-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 09/29/2023] [Indexed: 11/03/2023] Open
Abstract
IMPORTANCE Small proteins containing fewer than 70 amino acids, which were previously disregarded due to computational prediction and biochemical detection challenges, have gained increased attention in the scientific community in recent years. However, the number of functionally characterized small proteins, especially in archaea, is still limited. Here, by using biochemical and genetic approaches, we demonstrate a crucial role of the small protein sP36 in the nitrogen metabolism of M. mazei, which modulates the ammonium transporter AmtB1 according to nitrogen availability. This modulation might represent an ancient archaeal mechanism of AmtB1 inhibition, in contrast to the well-studied uridylylation-dependent regulation in bacteria.
Collapse
Affiliation(s)
- Tim Habenicht
- Institut für allgemeine Mikrobiologie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Katrin Weidenbach
- Institut für allgemeine Mikrobiologie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Adrian Velazquez-Campoy
- Institute of Biocomputation and Physics of Complex Systems (BIFI), Universidad de Zaragoza, Zaragoza, Spain
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
- Instituto de Investigaciones Sanitarias de Aragón (IIS Aragón), Zaragoza, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Madrid, Spain
| | - Ruben M. Buey
- Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain
| | - Monica Balsera
- Instituto de Recursos Naturales y Agrobiología de Salamanca, Spanish National Research Council (IRNASA-CSIC), Salamanca, Spain
| | - Ruth A. Schmitz
- Institut für allgemeine Mikrobiologie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| |
Collapse
|
6
|
Bizior A, Williamson G, Harris T, Hoskisson PA, Javelle A. Prokaryotic ammonium transporters: what has three decades of research revealed? MICROBIOLOGY (READING, ENGLAND) 2023; 169:001360. [PMID: 37450375 PMCID: PMC10433425 DOI: 10.1099/mic.0.001360] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 06/24/2023] [Indexed: 07/18/2023]
Abstract
The exchange of ammonium across cellular membranes is a fundamental process in all domains of life. In plants, bacteria and fungi, ammonium represents a vital source of nitrogen, which is scavenged from the external environment. In contrast, in animal cells ammonium is a cytotoxic metabolic waste product and must be excreted to prevent cell death. Transport of ammonium is facilitated by the ubiquitous Amt/Mep/Rh transporter superfamily. In addition to their function as transporters, Amt/Mep/Rh proteins play roles in a diverse array of biological processes and human physiopathology. Despite this clear physiological importance and medical relevance, the molecular mechanism of Amt/Mep/Rh proteins has remained elusive. Crystal structures of bacterial Amt/Rh proteins suggest electroneutral transport, whilst functional evidence supports an electrogenic mechanism. Here, focusing on bacterial members of the family, we summarize the structure of Amt/Rh proteins and what three decades of research tells us concerning the general mechanisms of ammonium translocation, in particular the possibility that the transport mechanism might differ in various members of the Amt/Mep/Rh superfamily.
Collapse
Affiliation(s)
- Adriana Bizior
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK
| | - Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK
| | - Paul A. Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, G4 0RE, UK
| |
Collapse
|
7
|
Hoogenboom JL, Anderson WG. Investigating nitrogen movement in North Pacific spiny dogfish (Squalus acanthias suckleyi), with focus on UT, Rhp2, and Rhbg mRNA abundance. J Comp Physiol B 2023:10.1007/s00360-023-01487-4. [PMID: 37162540 DOI: 10.1007/s00360-023-01487-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 03/15/2023] [Accepted: 04/14/2023] [Indexed: 05/11/2023]
Abstract
For ureosmotic marine elasmobranchs, the acquisition and retention of nitrogen is critical for the synthesis of urea. To better understand whole-body nitrogen homeostasis, we investigated mechanisms of nitrogen trafficking in North Pacific spiny dogfish (Squalus acanthias suckleyi). We hypothesized that the presence of nitrogen within the spiral valve lumen would affect both the transport of nitrogen and the mRNA abundance of a urea transporter (UT) and two ammonia transport proteins (Rhp2, Rhbg) within the intestinal epithelium. The in vitro preincubation of intestinal tissues in NH4Cl, intended to simulate dietary nitrogen availability, showed that increased ammonia concentrations did not significantly stimulate the net uptake of total urea or total methylamine. We also examined the mRNA abundance of UT, Rhp2, and Rhbg in the gills, kidney, liver, and spiral valve of fasted, fed, excess urea fed, and antibiotic-treated dogfish. After fasting, hepatic UT mRNA abundance was significantly lower, and Rhp2 mRNA in the gills was significantly higher than the other treatments. Feeding significantly increased Rhp2 mRNA levels in the kidney and mid spiral valve region. Both excess urea and antibiotics significantly reduced Rhbg mRNA levels along all three spiral valve regions. The antibiotic treatment also significantly diminished UT mRNA abundance levels in the anterior and mid spiral valve, and Rhbg mRNA levels in the kidney. In our study, no single treatment had significantly greater influence on the overall transcript abundance of the three transport proteins compared to another treatment, demonstrating the dynamic nature of nitrogen balance in these ancient fish.
Collapse
Affiliation(s)
- J Lisa Hoogenboom
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, V0R 1B0, Canada.
| | - W Gary Anderson
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, V0R 1B0, Canada
| |
Collapse
|
8
|
Chen H, Lv P, Liu Z, Chen W, Yao Y, Liu C, Cao Q, Zhou H. Preliminary study on the function of TMEM50A and its correlation with the RH genes. Transfus Med 2021; 31:277-285. [PMID: 33899290 DOI: 10.1111/tme.12778] [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: 06/04/2020] [Revised: 03/03/2021] [Accepted: 04/11/2021] [Indexed: 11/29/2022]
Abstract
OBJECTIVES The purpose of this study was to investigate the association and impact of TMEM50A on RH genes activity and function. BACKGROUND SMP1 is located on chromosome 1p36.11 in the RH gene locus, between the RHD and RHCE gene, where its position may be linked to RH haplotypes and contribute to selective pressures regarding certain RH haplotypes. TMEM50A is encoded by the SMP1 located in the intergenic region of RH, its influence on the function of the RH genes remains unclear. METHODS The expression of TMEM50A was regulated by transfection of plasmid and siRNA in K562 cell model. Western blot and real-time PCR were used to detect possible expression changes in the RH. The ammonium transport function of cells was monitored using pH-sensitive dye, while transcriptome sequencing was used to predict the potential function of TMEM50A. RESULTS The overexpression of TMEM50A significantly up-regulated RHCE gene activity (63.56%). The inhibition of TMEM50A resulted in significantly decreased RHCE (41.82%) and RHD expression (27.35%). Compared to control group, there was no significant change in the NH4 + transport function of cells in the overexpressed TMEM50A group. Transcriptome analysis showed that TMEM50A not only affected the transcription of target gene through splicing activities, but also played a role in the development of embryonic nervous system. CONCLUSIONS TMEM50A may regulate the expression of RH gene by affecting the stability of RH mRNA through splicing function. It speculates that TMEM50A may play an important role in the development of embryonic nervous system.
Collapse
Affiliation(s)
- Hongtian Chen
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Piao Lv
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Ziwei Liu
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Wanjun Chen
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Yuan Yao
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Chixiang Liu
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Qiong Cao
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Huayou Zhou
- Department of Blood Transfusion, Nanfang Hospital, Southern Medical University, Guangzhou, China
| |
Collapse
|
9
|
Michenkova M, Taki S, Blosser MC, Hwang HJ, Kowatz T, Moss FJ, Occhipinti R, Qin X, Sen S, Shinn E, Wang D, Zeise BS, Zhao P, Malmstadt N, Vahedi-Faridi A, Tajkhorshid E, Boron WF. Carbon dioxide transport across membranes. Interface Focus 2021; 11:20200090. [PMID: 33633837 PMCID: PMC7898146 DOI: 10.1098/rsfs.2020.0090] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2021] [Indexed: 12/30/2022] Open
Abstract
Carbon dioxide (CO2) movement across cellular membranes is passive and governed by Fick's law of diffusion. Until recently, we believed that gases cross biological membranes exclusively by dissolving in and then diffusing through membrane lipid. However, the observation that some membranes are CO2 impermeable led to the discovery of a gas molecule moving through a channel; namely, CO2 diffusion through aquaporin-1 (AQP1). Later work demonstrated CO2 diffusion through rhesus (Rh) proteins and NH3 diffusion through both AQPs and Rh proteins. The tetrameric AQPs exhibit differential selectivity for CO2 versus NH3 versus H2O, reflecting physico-chemical differences among the small molecules as well as among the hydrophilic monomeric pores and hydrophobic central pores of various AQPs. Preliminary work suggests that NH3 moves through the monomeric pores of AQP1, whereas CO2 moves through both monomeric and central pores. Initial work on AQP5 indicates that it is possible to create a metal-binding site on the central pore's extracellular face, thereby blocking CO2 movement. The trimeric Rh proteins have monomers with hydrophilic pores surrounding a hydrophobic central pore. Preliminary work on the bacterial Rh homologue AmtB suggests that gas can diffuse through the central pore and three sets of interfacial clefts between monomers. Finally, initial work indicates that CO2 diffuses through the electrogenic Na/HCO3 cotransporter NBCe1. At least in some cells, CO2-permeable proteins could provide important pathways for transmembrane CO2 movements. Such pathways could be amenable to cellular regulation and could become valuable drug targets.
Collapse
Affiliation(s)
- Marie Michenkova
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Sara Taki
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Matthew C. Blosser
- Mork Family Department of Chemical Engineering & Materials Science, University of Southern California, Los Angeles, CA, USA
| | - Hyea J. Hwang
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Thomas Kowatz
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Fraser. J. Moss
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Xue Qin
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Soumyo Sen
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Eric Shinn
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Dengke Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Brian S. Zeise
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Pan Zhao
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Noah Malmstadt
- Mork Family Department of Chemical Engineering & Materials Science, University of Southern California, Los Angeles, CA, USA
| | - Ardeschir Vahedi-Faridi
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Walter F. Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| |
Collapse
|
10
|
Ellingsen S, Narawane S, Fjose A, Verri T, Rønnestad I. Sequence analysis and spatiotemporal developmental distribution of the Cat-1-type transporter slc7a1a in zebrafish (Danio rerio). FISH PHYSIOLOGY AND BIOCHEMISTRY 2020; 46:2281-2298. [PMID: 32980952 PMCID: PMC7584565 DOI: 10.1007/s10695-020-00873-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 09/01/2020] [Indexed: 06/11/2023]
Abstract
Cationic amino acid transporter 1 (Cat-1 alias Slc7a1) is a Na+-independent carrier system involved in transport and absorption of the cationic amino acids lysine, arginine, histidine, and ornithine and has also been shown to be indispensable in a large variety of biological processes. Starting from isolated full-length zebrafish (Danio rerio) cDNA for slc7a1a, we performed comparative and phylogenetic sequence analysis, investigated the conservation of the gene during vertebrate evolution, and defined tissue expression during zebrafish development. Whole mount in situ hybridization first detected slc7a1a transcripts in somites, eyes, and brain at 14 h post-fertilization (hpf) with additional expression in the distal nephron at 24 hpf and in branchial arches at 3 days post-fertilization (dpf), with significant increase by 5 dpf. Taken together, the expression analysis of the zebrafish Cat-1 system gene slc7a1a suggests a functional role(s) during the early development of the central nervous system, muscle, gills, and kidney. Graphical abstract.
Collapse
Affiliation(s)
- Ståle Ellingsen
- Department of Molecular Biology, University of Bergen, Postbox 7803, NO-5020, Bergen, Norway
- Department of Biological Sciences, University of Bergen, Postbox 7803, NO-5020, Bergen, Norway
| | - Shailesh Narawane
- Department of Molecular Biology, University of Bergen, Postbox 7803, NO-5020, Bergen, Norway
| | - Anders Fjose
- Department of Molecular Biology, University of Bergen, Postbox 7803, NO-5020, Bergen, Norway
| | - Tiziano Verri
- Department of Biological and Environmental Sciences and Technologies, University of Salento, via Prov.le Lecce-Monteroni, I-73100, Lecce, Italy
| | - Ivar Rønnestad
- Department of Biological Sciences, University of Bergen, Postbox 7803, NO-5020, Bergen, Norway.
| |
Collapse
|
11
|
Ammonium transporter expression in sperm of the disease vector Aedes aegypti mosquito influences male fertility. Proc Natl Acad Sci U S A 2020; 117:29712-29719. [PMID: 33168715 PMCID: PMC7703593 DOI: 10.1073/pnas.2011648117] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Ammonium transporters (AMT) have been implicated in facilitating nitrogen assimilation in plants and bacteria and ammonia (NH3/NH4+) transport for nitrogen regulation and excretion in animals. However, the involvement of AMT proteins in mediating reproductive processes remains unexplored. We report that an insect AMT, AeAmt1, is expressed in the flagellum of spermatozoa from the dengue vector mosquito Aedes aegypti during sperm development through to egg fertilization. We provide evidence that AeAmt1 expression in spermatozoa is critical for sperm survival and overall male fertility. This description of ammonia transporter (AMT and Rh families) expression in the sperm of an animal provides a striking role for these evolutionarily conserved protein families and contributes to our understanding of mosquito reproductive biology. The ammonium transporter (AMT)/methylammonium permease (MEP)/Rhesus glycoprotein (Rh) family of ammonia (NH3/NH4+) transporters has been identified in organisms from all domains of life. In animals, fundamental roles for AMT and Rh proteins in the specific transport of ammonia across biological membranes to mitigate ammonia toxicity and aid in osmoregulation, acid–base balance, and excretion have been well documented. Here, we observed enriched Amt (AeAmt1) mRNA levels within reproductive organs of the arboviral vector mosquito, Aedes aegypti, prompting us to explore the role of AMTs in reproduction. We show that AeAmt1 is localized to sperm flagella during all stages of spermiogenesis and spermatogenesis in male testes. AeAmt1 expression in sperm flagella persists in spermatozoa that navigate the female reproductive tract following insemination and are stored within the spermathecae, as well as throughout sperm migration along the spermathecal ducts during ovulation to fertilize the descending egg. We demonstrate that RNA interference (RNAi)-mediated AeAmt1 protein knockdown leads to significant reductions (∼40%) of spermatozoa stored in seminal vesicles of males, resulting in decreased egg viability when these males inseminate nonmated females. We suggest that AeAmt1 function in spermatozoa is to protect against ammonia toxicity based on our observations of high NH4+ levels in the densely packed spermathecae of mated females. The presence of AMT proteins, in addition to Rh proteins, across insect taxa may indicate a conserved function for AMTs in sperm viability and reproduction in general.
Collapse
|
12
|
Zimmer AM, Perry SF. The Rhesus glycoprotein Rhcgb is expendable for ammonia excretion and Na + uptake in zebrafish (Danio rerio). Comp Biochem Physiol A Mol Integr Physiol 2020; 247:110722. [PMID: 32437959 DOI: 10.1016/j.cbpa.2020.110722] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/01/2020] [Accepted: 05/01/2020] [Indexed: 11/27/2022]
Abstract
In zebrafish (Danio rerio), the ammonia-transporting Rhesus glycoprotein Rhcgb is implicated in mechanisms of ammonia excretion and Na+ uptake. In particular, Rhcgb is thought to play an important role in maintaining ammonia excretion in response to alkaline conditions and high external ammonia (HEA) exposure, in addition to facilitating Na+ uptake via a functional metabolon with the Na+/H+-exchanger Nhe3b, specifically under low Na+ conditions. In the present study, we hypothesized that CRISPR/Cas9 knockout of rhcgb would reduce ammonia excretion and Na+ uptake capacity, particularly under the conditions listed above that have elicited increases in Rhcgb-mediated ammonia excretion and/or Na+ uptake. Contrary to this hypothesis, however, larval and juvenile rhcgb knockout (KO) mutants showed no reductions in ammonia excretion or Na+ uptake under any of the conditions tested in our study. In fact, under control conditions, rhcgb KO mutants generally displayed an increase in ammonia excretion, potentially due to increased transcript abundance of another rh gene, rhbg. Under alkaline conditions, rhcgb KO mutants were also able to maintain ammonia excretion, similar to wild-type fish, and stimulation of ammonia excretion after HEA exposure also was not affected by rhcgb KO. Surprisingly, ammonia excretion and Na+ uptake were unaffected by rhcgb or nhe3b KO in juvenile zebrafish acclimated to normal (800 μmol/L) or low (10 μmol/L) Na+ conditions. These results demonstrate that Rhcgb is expendable for ammonia excretion and Na+ uptake in zebrafish, highlighting the plasticity and flexibility of these physiological systems in this species.
Collapse
Affiliation(s)
- Alex M Zimmer
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
| | - Steve F Perry
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| |
Collapse
|
13
|
Brito AS, Neuhäuser B, Wintjens R, Marini AM, Boeckstaens M. Yeast filamentation signaling is connected to a specific substrate translocation mechanism of the Mep2 transceptor. PLoS Genet 2020; 16:e1008634. [PMID: 32069286 PMCID: PMC7048316 DOI: 10.1371/journal.pgen.1008634] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 02/28/2020] [Accepted: 01/28/2020] [Indexed: 11/18/2022] Open
Abstract
The dimorphic transition from the yeast to the filamentous form of growth allows cells to explore their environment for more suitable niches and is often crucial for the virulence of pathogenic fungi. In contrast to their Mep1/3 paralogues, fungal Mep2-type ammonium transport proteins of the conserved Mep-Amt-Rh family have been assigned an additional receptor role required to trigger the filamentation signal in response to ammonium scarcity. Here, genetic, kinetic and structure-function analyses were used to shed light on the poorly characterized signaling role of Saccharomyces cerevisiae Mep2. We show that Mep2 variants lacking the C-terminal tail conserve the ability to induce filamentation, revealing that signaling can proceed in the absence of exclusive binding of a putative partner to the largest cytosolic domain of the protein. Our data support that filamentation signaling requires the conformational changes accompanying substrate translocation through the pore crossing the hydrophobic core of Mep2. pHluorin reporter assays show that the transport activity of Mep2 and of non-signaling Mep1 differently affect yeast cytosolic pH in vivo, and that the unique pore variant Mep2H194E, with apparent uncoupling of transport and signaling functions, acquires increased ability of acidification. Functional characterization in Xenopus oocytes reveals that Mep2 mediates electroneutral substrate translocation while Mep1 performs electrogenic transport. Our findings highlight that the Mep2-dependent filamentation induction is connected to its specific transport mechanism, suggesting a role of pH in signal mediation. Finally, we show that the signaling process is conserved for the Mep2 protein from the human pathogen Candida albicans. Fungal Mep2-type ammonium transport proteins of the conserved Mep-Amt-Rh family that includes human Rhesus factors are specifically required to allow filamentation in response to ammonium limitation. These proteins were therefore assigned a receptor role while the underlying mechanism of signal transduction remains poorly understood. The “transceptor” property has subsequently been proposed to concern transporters of all kind of micro- and macro- nutrients in eukaryotes, from fungi to human. However, bringing the firm demonstration of their existence remains challenging as variants with full uncoupling of transport and receptor functions are difficult to obtain. Our data question the involvement of the C-terminal extremity of Saccharomyces cerevisiae Mep2 in the signal mediation leading to filamentation. If signaling partners exist, they should also bind to cytosolic loops and/or membrane-embedded domains. The capacity of Mep2 to enable filamentation is closely intertwined to the mechanism of substrate translocation through the pore of the hydrophobic core of the protein. In Xenopus oocytes, the transport activity of non-signaling Mep1 is electrogenic while it is electroneutral for Mep2, the latter likely translocating the weak base NH3, but not the proton released after NH4+ recognition and depronotation. We propose that given consequences of a Mep2-specific transport process, such as an intracellular pH modification, could be the underlying cause of the filamentation signal ensured by Mep2-type proteins.
Collapse
Affiliation(s)
- Ana Sofia Brito
- Biology of Membrane Transport Laboratory, Molecular Biology Department, Université Libre de Bruxelles, Gosselies, Belgium
| | - Benjamin Neuhäuser
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Stuttgart, Germany
| | - René Wintjens
- Unité Microbiologie, Chimie Bioorganique et Macromoléculaire, Département RD3, Faculté de Pharmacie, Université Libre de Bruxelles, Brussels, Belgium
| | - Anna Maria Marini
- Biology of Membrane Transport Laboratory, Molecular Biology Department, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail: (AMM); (MB)
| | - Mélanie Boeckstaens
- Biology of Membrane Transport Laboratory, Molecular Biology Department, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail: (AMM); (MB)
| |
Collapse
|
14
|
Wang Y, Pasparakis C, Mager EM, Stieglitz JD, Benetti D, Grosell M. Ontogeny of urea and ammonia transporters in mahi-mahi (Coryphaena hippurus) early life stages. Comp Biochem Physiol A Mol Integr Physiol 2019; 229:18-24. [PMID: 30503629 DOI: 10.1016/j.cbpa.2018.11.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 11/25/2018] [Indexed: 01/17/2023]
Abstract
The mechanism(s) of ammonia and urea excretion in freshwater fish have received considerable attention; however, parallel investigations of seawater fish, specifically in the early life stages are scarce. The first objective of this study was to evaluate the patterns of ammonia and urea excretion in mahi-mahi (Coryphaena hippurus) up to 102 hours post fertilization (hpf). Similar to other teleosts, mahi embryos are ureotelic before hatch and gradually switch to being ammoniotelic around the time of hatch. The second objective was to characterize mRNA levels of ammonia transporters (Rhag, Rhbg, Rhcg1 and Rhcg2), as well as urea transporter (UT) and sodium hydrogen exchangers (NHE3 and NHE2) during mahi development. As predicted, the mRNA levels of the Rhesus glycoprotein (Rh) genes, especially Rhag, Rhbg and the UT gene were highly consistent with the ontogeny of ammonia and urea excretion rates. Further, the localization of each transporter was examined in larvae collected at 60 and 102 hpf using in situ hybridization. Rhag was expressed in the gills, yolk sac, and operculum. Rhbg was expressed in the gills and upper mouth. Rhcg1 and NHE3 were co-localized in the sub-operculum, and Rhcg2 was expressed in the skin. Together, these results indicate that urea excretion is critical for ammonia detoxification during embryonic development and that Rh proteins are involved in ammonia excretion via gills and yolk sac, possibly facilitated by NHE3.
Collapse
Affiliation(s)
- Y Wang
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States.
| | - C Pasparakis
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - E M Mager
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States; Department of Biological Sciences & Advanced Environmental Research Institute, University of North Texas, Denton, TX 76203, United States
| | - J D Stieglitz
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - D Benetti
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| | - M Grosell
- RSMAS, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
| |
Collapse
|
15
|
Mirandela GD, Tamburrino G, Hoskisson PA, Zachariae U, Javelle A. The lipid environment determines the activity of the Escherichia coli ammonium transporter AmtB. FASEB J 2018; 33:1989-1999. [PMID: 30211659 PMCID: PMC6338640 DOI: 10.1096/fj.201800782r] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The movement of ammonium across biologic membranes is a fundamental process in all living organisms and is mediated by the ubiquitous ammonium transporter/methylammonium permease/rhesus protein (Amt/Mep/Rh) family of transporters. Recent structural analysis and coupled mass spectrometry studies have shown that the Escherichia coli ammonium transporter AmtB specifically binds 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG). Upon POPG binding, several residues of AmtB undergo a small conformational change, which stabilizes the protein against unfolding. However, no studies have so far been conducted, to our knowledge, to explore whether POPG binding to AmtB has functional consequences. Here, we used an in vitro experimental assay with purified components, together with molecular dynamics simulations, to characterize the relation between POPG binding and AmtB activity. We show that the AmtB activity is electrogenic. Our results indicate that the activity, at the molecular level, of Amt in archaebacteria and eubacteria may differ. We also show that POPG is an important cofactor for AmtB activity and that, in the absence of POPG, AmtB cannot complete the full translocation cycle. Furthermore, our simulations reveal previously undiscovered POPG binding sites on the intracellular side of the lipid bilayer between the AmtB subunits. Possible molecular mechanisms explaining the functional role of POPG are discussed.-Mirandela, G. D., Tamburrino, G., Hoskisson, P. A., Zachariae, U., Javelle, A. The lipid environment determines the activity of the Escherichia coli ammonium transporter AmtB.
Collapse
Affiliation(s)
- Gaëtan Dias Mirandela
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Giulia Tamburrino
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, United Kingdom.,Physics, School of Science and Engineering, University of Dundee, Dundee, United Kingdom
| | - Paul A Hoskisson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Ulrich Zachariae
- Computational Biology, School of Life Sciences, University of Dundee, Dundee, United Kingdom.,Physics, School of Science and Engineering, University of Dundee, Dundee, United Kingdom
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| |
Collapse
|
16
|
Ariz I, Boeckstaens M, Gouveia C, Martins AP, Sanz-Luque E, Fernández E, Soveral G, von Wirén N, Marini AM, Aparicio-Tejo PM, Cruz C. Nitrogen isotope signature evidences ammonium deprotonation as a common transport mechanism for the AMT-Mep-Rh protein superfamily. SCIENCE ADVANCES 2018; 4:eaar3599. [PMID: 30214933 PMCID: PMC6135547 DOI: 10.1126/sciadv.aar3599] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 07/27/2018] [Indexed: 06/08/2023]
Abstract
Ammonium is an important nitrogen (N) source for living organisms, a key metabolite for pH control, and a potent cytotoxic compound. Ammonium is transported by the widespread AMT-Mep-Rh membrane proteins, and despite their significance in physiological processes, the nature of substrate translocation (NH3/NH4+) by the distinct members of this family is still a matter of controversy. Using Saccharomyces cerevisiae cells expressing representative AMT-Mep-Rh ammonium carriers and taking advantage of the natural chemical-physical property of the N isotopic signature linked to NH4+/NH3 conversion, this study shows that only cells expressing AMT-Mep-Rh proteins were depleted in 15N relative to 14N when compared to the external ammonium source. We observed 15N depletion over a wide range of external pH, indicating its independence of NH3 formation in solution. On the basis of inhibitor studies, ammonium transport by nonspecific cation channels did not show isotope fractionation but competition with K+. We propose that kinetic N isotope fractionation is a common feature of AMT-Mep-Rh-type proteins, which favor 14N over 15N, owing to the dissociation of NH4+ into NH3 + H+ in the protein, leading to 15N depletion in the cell and allowing NH3 passage or NH3/H+ cotransport. This deprotonation mechanism explains these proteins' essential functions in environments under a low NH4+/K+ ratio, allowing organisms to specifically scavenge NH4+. We show that 15N isotope fractionation may be used in vivo not only to determine the molecular species being transported by ammonium transport proteins, but also to track ammonium toxicity and associated amino acids excretion.
Collapse
Affiliation(s)
- Idoia Ariz
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Mélanie Boeckstaens
- Biology of Membrane Transport, Department of Molecular Biology, Université Libre de Bruxelles, 6041 Gosselies, Belgium
| | - Catarina Gouveia
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Ana Paula Martins
- iMed.ULisboa–Research Institute for Medicines, Faculdade de Farmácia da Universidade de Lisboa, 1649-003 Lisboa, Portugal
| | - Emanuel Sanz-Luque
- Department of Biochemistry and Molecular Biology, Univeristy of Córdoba, 14071 Cordoba, Spain
| | - Emilio Fernández
- Department of Biochemistry and Molecular Biology, Univeristy of Córdoba, 14071 Cordoba, Spain
| | - Graça Soveral
- iMed.ULisboa–Research Institute for Medicines, Faculdade de Farmácia da Universidade de Lisboa, 1649-003 Lisboa, Portugal
| | - Nicolaus von Wirén
- Department of Physiology and Cell Biology, Leibniz Institute for Plant Genetics and Crop Plant Research, Seeland, 06466 OT Gatersleben, Germany
| | - Anna M. Marini
- Biology of Membrane Transport, Department of Molecular Biology, Université Libre de Bruxelles, 6041 Gosselies, Belgium
| | | | - Cristina Cruz
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
| |
Collapse
|
17
|
Flatt JF, Bruce LJ. The Molecular Basis for Altered Cation Permeability in Hereditary Stomatocytic Human Red Blood Cells. Front Physiol 2018; 9:367. [PMID: 29713289 PMCID: PMC5911802 DOI: 10.3389/fphys.2018.00367] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 03/27/2018] [Indexed: 11/20/2022] Open
Abstract
Normal human RBCs have a very low basal permeability (leak) to cations, which is continuously corrected by the Na,K-ATPase. The leak is temperature-dependent, and this temperature dependence has been evaluated in the presence of inhibitors to exclude the activity of the Na,K-ATPase and NaK2Cl transporter. The severity of the RBC cation leak is altered in various conditions, most notably the hereditary stomatocytosis group of conditions. Pedigrees within this group have been classified into distinct phenotypes according to various factors, including the severity and temperature-dependence of the cation leak. As recent breakthroughs have provided more information regarding the molecular basis of hereditary stomatocytosis, it has become clear that these phenotypes elegantly segregate with distinct genetic backgrounds. The cryohydrocytosis phenotype, including South-east Asian Ovalocytosis, results from mutations in SLC4A1, and the very rare condition, stomatin-deficient cryohydrocytosis, is caused by mutations in SLC2A1. Mutations in RHAG cause the very leaky condition over-hydrated stomatocytosis, and mutations in ABCB6 result in familial pseudohyperkalemia. All of the above are large multi-spanning membrane proteins and the mutations may either modify the structure of these proteins, resulting in formation of a cation pore, or otherwise disrupt the membrane to allow unregulated cation movement across the membrane. More recently mutations have been found in two RBC cation channels, PIEZO1 and KCNN4, which result in dehydrated stomatocytosis. These mutations alter the activation and deactivation kinetics of these channels, leading to increased opening and allowing greater cation fluxes than in wild type.
Collapse
Affiliation(s)
- Joanna F Flatt
- Bristol Institute for Transfusion Sciences, NHS Blood and Transplant, Bristol, United Kingdom
| | - Lesley J Bruce
- Bristol Institute for Transfusion Sciences, NHS Blood and Transplant, Bristol, United Kingdom
| |
Collapse
|
18
|
André B. Tribute to Marcelle Grenson (1925-1996), A Pioneer in the Study of Amino Acid Transport in Yeast. Int J Mol Sci 2018; 19:E1207. [PMID: 29659503 PMCID: PMC5979419 DOI: 10.3390/ijms19041207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 04/07/2018] [Accepted: 04/10/2018] [Indexed: 02/05/2023] Open
Abstract
The year 2016 marked the 20th anniversary of the death of Marcelle Grenson and the 50th anniversary of her first publication on yeast amino acid transport, the topic to which, as Professor at the Free University of Brussels (ULB), she devoted the major part of her scientific career. M. Grenson was the first scientist in Belgium to introduce and apply genetic analysis in yeast to dissect the molecular mechanisms that were underlying complex problems in biology. Today, M. Grenson is recognized for the pioneering character of her work on the diversity and regulation of amino acid transporters in yeast. The aim of this tribute is to review the major milestones of her forty years of scientific research that were conducted between 1950 and 1990.
Collapse
Affiliation(s)
- Bruno André
- Molecular Physiology of the Cell, Université Libre de Bruxelles (ULB), Biopark, 6041 Gosselies, Belgium.
| |
Collapse
|
19
|
Stumpff F. A look at the smelly side of physiology: transport of short chain fatty acids. Pflugers Arch 2018; 470:571-598. [PMID: 29305650 DOI: 10.1007/s00424-017-2105-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 12/19/2017] [Accepted: 12/20/2017] [Indexed: 12/14/2022]
Abstract
Fermentative organs such as the caecum, the colon, and the rumen have evolved to produce and absorb energy rich short chain fatty acids (SCFA) from otherwise indigestible substrates. Classical models postulate diffusional uptake of the undissociated acid (HSCFA). However, in net terms, a major part of SCFA absorption occurs with uptake of Na+ and resembles classical, coupled electroneutral NaCl transport. Considerable evidence suggests that the anion transporting proteins expressed by epithelia of fermentative organs are poorly selective and that their main function may be to transport acetate-, propionate-, butyrate- and HCO3- as the physiologically relevant anions. Apical uptake of SCFA thus involves non-saturable diffusion of the undissociated acid (HSCFA), SCFA-/HCO3- exchange via DRA (SLC26A3) and/or SCFA--H+ symport (MCT1, SLC16A1). All mechanisms lead to cytosolic acidification with stimulation of Na+/H+ exchange via NHE (SLC9A2/3). Basolaterally, Na+ leaves via the Na+/K+-ATPase with recirculation of K+. Na+ efflux drives the transport of SCFA- anions through volume-regulated anion channels, such as maxi-anion channels (possibly SLCO2A1), LRRC8, anoctamins, or uncoupled exchangers. When luminal buffering is inadequate, basolateral efflux will increasingly involve SCFA-/ HCO3- exchange (AE1/2, SCL4A1/2), or efflux of SCFA- with H+ (MCT1/4, SLC16A1/3). Furthermore, protons can be basolaterally removed by NHE1 (SCL9A1) or NBCe1 (SLC4A4). The purpose of these transport proteins is to maximize the amount of SCFA transported from the tightly buffered ingesta while minimizing acid transport through the epithelium. As known from the rumen for many decades, a disturbance of these processes is likely to cause severe colonic disease.
Collapse
Affiliation(s)
- Friederike Stumpff
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.
| |
Collapse
|
20
|
Si L, Pan L, Wang H, Zhang X. Identification of the role of Rh protein in ammonia excretion of swimming crab Portunus trituberculatus. J Exp Biol 2018; 221:jeb.184655. [DOI: 10.1242/jeb.184655] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 08/24/2018] [Indexed: 12/14/2022]
Abstract
In Portunus trituberculatus, a full-length cDNA of Rhesus-like glycoprotein (Rh protein), the whole 478 amino acids, has been identified in gills, which plays an essential role in ammonia (NH3 /NH4+) excretion. Phylogenetic analysis of the Rh-like proteins from crabs was clustered, showing high conservation of the ammonium transporter domain and transmembrane segments essential to the function of Rh protein. Rh protein of P. trituberculatus (PtRh) was detected in all tested tissues, and showed the highest expression in gills. To further characterize the role of PtRh in ammonia metabolism and excretion, a double-stranded RNA-mediated RNA interference of PtRh was employed. The knockdown of PtRh up-regulated mRNA expression of ammonia excretion related genes aquaporin (AQP), K+-channel, vesicle associated membrane protein (VAMP), increased activities of Na+ /K+ -ATPase (NKA) and V-type H+-ATPase (V-ATPase), whereas the Na+/H+-exchanger (NHE) expression reduced firstly and then elevated. dsRNA-mediated reductions in PtRh significantly reduced ammonia excretion rate and increased ammonia and glutamine (Gln) levels in hemolymph, together with increase of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) activites, indicating a central role for PtRh in ammonia excretion and detoxification mechanisms. Taken together, we conclude that the Rh protein is a primary contributor to ammonia excretion of P. trituberculatus, which may be the basis of their ability to inhabit benthic water with high ammonia levels.
Collapse
Affiliation(s)
- Lingjun Si
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Luqing Pan
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Hongdan Wang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Xin Zhang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| |
Collapse
|
21
|
Merhi A, Delrée P, Marini AM. The metabolic waste ammonium regulates mTORC2 and mTORC1 signaling. Sci Rep 2017; 7:44602. [PMID: 28303961 PMCID: PMC5355986 DOI: 10.1038/srep44602] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/09/2017] [Indexed: 12/21/2022] Open
Abstract
Two structurally and functionally distinct mammalian TOR complexes control cell growth and metabolism in physiological and pathological contexts including cancer. Upregulated glutaminolysis is part of the metabolic reprogramming occurring in cancer, providing fuels for growth but also liberating ammonium, a potent neurotoxic waste product. Here, we identify ammonium as a novel dose-dependent signal mediating rapid mTORC2 activation and further regulating mTORC1. We show that ammonium induces rapid RICTOR-dependent phosphorylation of AKT-S473, a process requiring the PI3K pathway and further involving the Src-family kinase YES1, the FAK kinase and the ITGβ1 integrin. Release of calcium from the endoplasmic reticulum store triggers rapid mTORC2 activation, similar to ammonium-induced activation, the latter being conversely prevented by calcium chelation.Moreover, in analogy to growth factors, ammonium triggers the AKT-dependent phosphoinhibition of the TSC complex and of PRAS40, two negative regulators of mTORC1. Consistent with mTORC1 stimulation, ammonium induces the inhibitory phosphorylation of 4EBP1, a negative regulator of protein biogenesis. Ammonium however dually impacts on the phosphorylation of p70S6K1 triggering a transient AKT-independent decrease in the phosphorylation of this second mTORC1 readout. Finally, we reveal ammonium as a dose-dependent stimulator of proliferation. This study underscores an mTORC2 and mTORC1 response to the so-called ammonium waste.
Collapse
Affiliation(s)
- Ahmad Merhi
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium.,Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium.,Tumour Bank, Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium
| | - Paul Delrée
- Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium.,Tumour Bank, Institute of Pathology and Genetics, Avenue Georges Lemaître 25, 6041 Gosselies, Belgium
| | - Anna Maria Marini
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Rue des Professeurs Jeener et Brachet 12, 6041 Gosselies, Belgium
| |
Collapse
|
22
|
Abdulnour-Nakhoul S, Le T, Rabon E, Hamm LL, Nakhoul NL. Structural determinants of NH3 and NH4+ transport by mouse Rhbg, a renal Rh glycoprotein. Am J Physiol Renal Physiol 2016; 311:F1280-F1293. [PMID: 27681563 PMCID: PMC5210199 DOI: 10.1152/ajprenal.00556.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 09/21/2016] [Indexed: 11/22/2022] Open
Abstract
Renal Rhbg is localized to the basolateral membrane of intercalated cells and is involved in NH3/NH4+ transport. The structure of Rhbg is not yet resolved; however, a high-resolution crystal structure of AmtB, a bacterial homolog of Rh, has been determined. We aligned the sequence of Rhbg to that of AmtB and identified important sites of Rhbg that may affect transport. Our analysis positioned three conserved amino acids, histidine 183 (H183), histidine 342 (H342), and tryptophan 230 (W230), within the hydrophobic pore where they presumably serve to control NH3 transport. A fourth residue, phenylalanine 128 (F128) was positioned at the upper vestibule, presumably contributing to recruitment of NH4+ We generated three mutations each of H183, H342, W230, and F128 and expressed them in frog oocytes. Immunolabeling showed that W230 and F128 mutants were localized to the cell membrane, whereas H183 and H342 staining was diffuse and mostly intracellular. To determine function, we compared measurements of NH3/NH4+ and methyl amine (MA)/methyl ammonium (MA+)-induced currents, intracellular pH, and surface pH (pHs) among oocytes expressing the mutants, Rhbg, or injected with H2O. In H183 and W230 mutants, NH4+-induced current and intracellular acidification were inhibited compared with that of Rhbg, and MA-induced intracellular alkalinization was completely absent. Expression of H183A or W230A mutants inhibited NH3/NH4+- and MA/MA+-induced decrease in pHs to the level observed in H2O-injected oocytes. Mutations of F128 did not significantly affect transport of NH3 or NH4+ These data demonstrated that mutating H183 or W230 caused loss of function but not F128. H183 and H342 may affect membrane expression of the transporter.
Collapse
Affiliation(s)
- Solange Abdulnour-Nakhoul
- Southeast Louisiana Veterans Health Care Network and Department of Medicine, Section of Nephrology, Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Trang Le
- Southeast Louisiana Veterans Health Care Network and Department of Medicine, Section of Nephrology, Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Edd Rabon
- Southeast Louisiana Veterans Health Care Network and Department of Medicine, Section of Nephrology, Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - L Lee Hamm
- Southeast Louisiana Veterans Health Care Network and Department of Medicine, Section of Nephrology, Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Nazih L Nakhoul
- Southeast Louisiana Veterans Health Care Network and Department of Medicine, Section of Nephrology, Department of Physiology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| |
Collapse
|
23
|
Suzuki A, Komata H, Iwashita S, Seto S, Ikeya H, Tabata M, Kitano T. Evolution of the RH gene family in vertebrates revealed by brown hagfish (Eptatretus atami) genome sequences. Mol Phylogenet Evol 2016; 107:1-9. [PMID: 27746317 DOI: 10.1016/j.ympev.2016.10.004] [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: 06/13/2016] [Revised: 10/04/2016] [Accepted: 10/08/2016] [Indexed: 01/02/2023]
Abstract
In vertebrates, there are four major genes in the RH (Rhesus) gene family, RH, RHAG, RHBG, and RHCG. These genes are thought to have been formed by the two rounds of whole-genome duplication (2R-WGD) in the common ancestor of all vertebrates. In our previous work, where we analyzed details of the gene duplications process of this gene family, three nucleotide sequences belonging to this family were identified in Far Eastern brook lamprey (Lethenteron reissneri), and the phylogenetic positions of the genes were determined. Lampreys, along with hagfishes, are cyclostomata (jawless fishes), which is a sister group of gnathostomata (jawed vertebrates). Although those results suggested that one gene was orthologous to the gnathostome RHCG genes, we did not identify clear orthologues for other genes. In this study, therefore, we identified three novel cDNA sequences that belong to the RH gene family using de novo transcriptome analysis of another cyclostome: the brown hagfish (Eptatretus atami). We also determined the nucleotide sequences for the RHBG and RHCG genes in a red stingray (Dasyatis akajei), which belongs to the cartilaginous fishes. The phylogenetic tree showed that two brown hagfish genes, which were probably duplicated in the cyclostome lineage, formed a cluster with the gnathostome RHAG genes, whereas another brown hagfish gene formed a cluster with the gnathostome RHCG genes. We estimated that the RH genes had a higher evolutionary rate than the RHAG, RHBG, and RHCG genes. Interestingly, in the RHBG genes, only the bird lineage showed a higher rate of nonsynonymous substitutions. It is likely that this higher rate was caused by a state of relaxed functional constraints rather than positive selection nor by pseudogenization.
Collapse
Affiliation(s)
- Akinori Suzuki
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Hidero Komata
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Shogo Iwashita
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Shotaro Seto
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Hironobu Ikeya
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Mitsutoshi Tabata
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan
| | - Takashi Kitano
- Department of Biomolecular Functional Engineering, College of Engineering, Ibaraki University, 4-12-1 Nakanarusawa-cho, Hitachi 316-8511, Japan.
| |
Collapse
|
24
|
Boeckstaens M. [From the discovery of microbial Mep-Amt ammonium transporters to human Rhesus factors]. Med Sci (Paris) 2016; 32:394-400. [PMID: 27137697 DOI: 10.1051/medsci/20163204018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Ammonium, ubiquitous on Earth, plays major and distinct roles in most organisms. While it can be a nitrogen source for many microorganisms and plants, it is a cytotoxic metabolic product actively detoxified by the liver in animals. Furthermore, in the latter, ammonium synthesis in the kidney is involved in acid/base homeostasis. Ammonium transport is ensured by a family of proteins, called Mep-Amt-Rh. This family is conserved in all domains of life and comprises the human Rh factors, notably known in transfusional medicine. While the study of bacterial, fungal and vegetal Mep-Amt transporters reveals a fine-tuned and rapid regulation of these proteins in function of environmental changes, the regulation of animal Rh proteins has been poorly addressed. This review notably highlights the importance of the yeast model in the study of the regulation of these proteins as well as in the functional characterization of Mep-Amt-Rh members of diverse origins.
Collapse
Affiliation(s)
- Mélanie Boeckstaens
- Laboratoire de biologie du transport membranaire, IBMM, université Libre de Bruxelles, 12, rue des Professeurs Jeener et Brachet, 6041 Gosselies, Belgique
| |
Collapse
|
25
|
McDonald TR, Ward JM. Evolution of Electrogenic Ammonium Transporters (AMTs). FRONTIERS IN PLANT SCIENCE 2016; 7:352. [PMID: 27066024 PMCID: PMC4814505 DOI: 10.3389/fpls.2016.00352] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 03/07/2016] [Indexed: 05/05/2023]
Abstract
The ammonium transporter gene family consists of three main clades, AMT, MEP, and Rh. The evolutionary history of the AMT/MEP/Rh gene family is characterized by multiple horizontal gene transfer events, gene family expansion and contraction, and gene loss; thus the gene tree for this family of transporters is unlike the organismal tree. The genomes of angiosperms contain genes for both electrogenic and electroneutral ammonium transporters, but it is not clear how far back in the land plant lineage electrogenic ammonium transporters occur. Here, we place Marchantia polymorpha ammonium transporters in the AMT/MEP/Rh phylogeny and we show that AMTs from the liverwort M. polymorpha are electrogenic. This information suggests that electrogenic ammonium transport evolved at least as early as the divergence of bryophytes in the land plant lineage.
Collapse
Affiliation(s)
| | - John M. Ward
- Department of Plant Biology, University of MinnesotaSt. Paul, MN, USA
| |
Collapse
|
26
|
The TORC1 effector kinase Npr1 fine tunes the inherent activity of the Mep2 ammonium transport protein. Nat Commun 2015; 5:3101. [PMID: 24476960 DOI: 10.1038/ncomms4101] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 12/13/2013] [Indexed: 12/30/2022] Open
Abstract
The TORC1 complex controls cell growth upon integrating nutritional signals including amino-acid availability. TORC1 notably adapts the plasma membrane protein content by regulating arrestin-mediated endocytosis of amino-acid transporters. Here we demonstrate that TORC1 further fine tunes the inherent activity of the ammonium transport protein, Mep2, a yeast homologue of mammalian Rhesus factors, independently of arrestin-mediated endocytosis. The TORC1 effector kinase Npr1 and the upstream TORC1 regulator Npr2 control Mep2 transport activity by phospho-silencing a carboxy-terminal autoinhibitory domain. Under poor nitrogen supply, Npr1 enables Mep2 S457 phosphorylation and thus ammonium transport activity. Supplementation of the preferred nitrogen source glutamine leads to Mep2 inactivation and instant S457 dephosphorylation via plasma membrane Psr1 and Psr2 redundant phosphatases. This study underscores that TORC1 also adjusts nutrient permeability to regulate cell growth in a fast and flexible response to environmental perturbation, establishing a hierarchy in the transporters to be degraded, inactivated or maintained active at the plasma membrane.
Collapse
|
27
|
Caner T, Abdulnour-Nakhoul S, Brown K, Islam MT, Hamm LL, Nakhoul NL. Mechanisms of ammonia and ammonium transport by rhesus-associated glycoproteins. Am J Physiol Cell Physiol 2015; 309:C747-58. [PMID: 26354748 DOI: 10.1152/ajpcell.00085.2015] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 09/02/2015] [Indexed: 01/24/2023]
Abstract
In this study we characterized ammonia and ammonium (NH3/NH4(+)) transport by the rhesus-associated (Rh) glycoproteins RhAG, Rhbg, and Rhcg expressed in Xenopus oocytes. We used ion-selective microelectrodes and two-electrode voltage clamp to measure changes in intracellular pH, surface pH, and whole cell currents induced by NH3/NH4(+) and methyl amine/ammonium (MA/MA(+)). These measurements allowed us to define signal-specific signatures to distinguish NH3 from NH4(+) transport and to determine how transport of NH3 and NH4(+) differs among RhAG, Rhbg, and Rhcg. Our data indicate that expression of Rh glycoproteins in oocytes generally enhanced NH3/NH4(+) transport and that cellular changes induced by transport of MA/MA(+) by Rh proteins were different from those induced by transport of NH3/NH4(+). Our results support the following conclusions: 1) RhAG and Rhbg transport both the ionic NH4(+) and neutral NH3 species; 2) transport of NH4(+) is electrogenic; 3) like Rhbg, RhAG transport of NH4(+) masks NH3 transport; and 4) Rhcg is likely to be a predominantly NH3 transporter, with no evidence of enhanced NH4(+) transport by this transporter. The dual role of Rh proteins as NH3 and NH4(+) transporters is a unique property and may be critical in understanding how transepithelial secretion of NH3/NH4(+) occurs in the renal collecting duct.
Collapse
Affiliation(s)
- Tolga Caner
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Solange Abdulnour-Nakhoul
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Karen Brown
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - M Toriqul Islam
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - L Lee Hamm
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| | - Nazih L Nakhoul
- Section of Nephrology, Department of Medicine, and Department of Physiology, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana; and Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana
| |
Collapse
|
28
|
Boeckstaens M, Merhi A, Llinares E, Van Vooren P, Springael JY, Wintjens R, Marini AM. Identification of a Novel Regulatory Mechanism of Nutrient Transport Controlled by TORC1-Npr1-Amu1/Par32. PLoS Genet 2015; 11:e1005382. [PMID: 26172854 PMCID: PMC4501750 DOI: 10.1371/journal.pgen.1005382] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 06/22/2015] [Indexed: 01/12/2023] Open
Abstract
Fine-tuning the plasma-membrane permeability to essential nutrients is fundamental to cell growth optimization. Nutritional signals including nitrogen availability are integrated by the TORC1 complex which notably regulates arrestin-mediated endocytosis of amino-acid transporters. Ammonium is a ubiquitous compound playing key physiological roles in many, if not all, organisms. In yeast, it is a preferred nitrogen source transported by three Mep proteins which are orthologues of the mammalian Rhesus factors. By combining genetic, kinetic, biochemical and cell microscopy analyses, the current study reveals a novel mechanism enabling TORC1 to regulate the inherent activity of ammonium transport proteins, independently of arrestin-mediated endocytosis, identifying the still functional orphan Amu1/Par32 as a selective regulator intermediate. We show that, under poor nitrogen supply, the TORC1 effector kinase' Npr1' promotes phosphorylation of Amu1/Par32 which appears mainly cytosolic while ammonium transport proteins are active. Upon preferred nitrogen supplementation, like glutamine or ammonium addition, TORC1 upregulation enables Npr1 inhibition and Amu1/Par32 dephosphorylation. In these conditions, as in Npr1-lacking cells, hypophosphorylated Amu1/Par32 accumulates at the cell surface and mediates the inhibition of specific ammonium transport proteins. We show that the integrity of a conserved repeated motif of Amu1/Par32 is required for the interaction with these transport proteins. This study underscores the diversity of strategies enabling TORC1-Npr1 to selectively monitor cell permeability to nutrients by discriminating between transporters to be degraded or transiently inactivated and kept stable at the plasma membrane. This study further identifies the function of Amu1/Par32 in acute control of ammonium transport in response to variations in nitrogen availability. Cells have evolved a variety of mechanisms to control the permeability of the plasma membrane to face environmental perturbations. Transcriptional regulation, endocytosis, gating and activity control of channels and transporters enable global or specific responses to stressful conditions and focused variations in nutrient availability. Emerging data from the yeast model reveal that the conserved TORC1 pathway regulates arrestin-mediated endocytosis of amino-acid transporters. We provide genetic and biochemical evidence for a novel mechanism enabling TORC1 to regulate the inherent activity of transport proteins via the Amu1/Par32 regulator intermediate. This low complexity protein mediates inhibition of specific proteins dedicated to the transport of ammonium, a favored nitrogen source, underscoring that TORC1 selects transporters to be degraded or transiently inactivated and preserved at the cell surface according to the environmental situation. The here-revealed mechanism of transport inhibition by Amu/Par32 is reminiscent to the inhibition of prokaryotic ammonium transport proteins mediated by PII-type proteins, key nitrogen signal transducers widespread in bacteria and Archaea.
Collapse
Affiliation(s)
- Mélanie Boeckstaens
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | - Ahmad Merhi
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | - Elisa Llinares
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | - Pascale Van Vooren
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | | | - René Wintjens
- Laboratoire des Biopolymères et des nanomatériaux supramoléculaires, Université Libre de Bruxelles, Brussels, Belgium
| | - Anna Maria Marini
- Biology of Membrane Transport, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail:
| |
Collapse
|
29
|
Merhi A, De Mees C, Abdo R, Victoria Alberola J, Marini AM. Wnt/β-Catenin Signaling Regulates the Expression of the Ammonium Permease Gene RHBG in Human Cancer Cells. PLoS One 2015; 10:e0128683. [PMID: 26029888 PMCID: PMC4452261 DOI: 10.1371/journal.pone.0128683] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 04/29/2015] [Indexed: 11/18/2022] Open
Abstract
Ammonium is a metabolic waste product mainly detoxified by the liver. Hepatic dysfunction can lead to cytotoxic accumulation of circulating ammonium and to subsequent encephalopathy. Transmembrane ammonium transport is a widely spread process ensured by the highly conserved proteins of the Mep-Amt-Rh superfamily, including the mammalian Rhesus (Rh) factors. The regulatory mechanisms involved in the control of RH genes expression remain poorly studied. Here we addressed the expression regulation of one of these factors, RHBG. We identify HepG2 hepatocellular carcinoma cells and SW480 colon adenocarcinoma cells as expressing RHBG and show that its expression relies on β-catenin signaling. siRNA-mediated β-catenin knockdown resulted in significant reduction of RHBG mRNA in both cell lines. Pharmaceutical inhibition of the TCF4/β-catenin interaction or knockdown of the transcription factor TCF4 also downregulated RHBG expression. We identify a minimal RHBG regulatory sequence displaying a promoter activity and show that β-catenin and TCF4 bind to this fragment in vivo. We finally characterize the role of potential TCF4 binding sites in RHBG regulation. Taken together, our results indicate RHBG expression as a direct target of β-catenin regulation, a pathway frequently deregulated in many cancers and associated with tumorigenesis.
Collapse
Affiliation(s)
- Ahmad Merhi
- Biology of Membrane Transport Laboratory, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | - Christelle De Mees
- Biology of Membrane Transport Laboratory, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | - Rami Abdo
- Biology of Membrane Transport Laboratory, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
| | | | - Anna Maria Marini
- Biology of Membrane Transport Laboratory, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail:
| |
Collapse
|
30
|
Chantranupong L, Wolfson RL, Sabatini DM. Nutrient-sensing mechanisms across evolution. Cell 2015; 161:67-83. [PMID: 25815986 DOI: 10.1016/j.cell.2015.02.041] [Citation(s) in RCA: 229] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Indexed: 12/11/2022]
Abstract
For organisms to coordinate their growth and development with nutrient availability, they must be able to sense nutrient levels in their environment. Here, we review select nutrient-sensing mechanisms in a few diverse organisms. We discuss how these mechanisms reflect the nutrient requirements of specific species and how they have adapted to the emergence of multicellularity in eukaryotes.
Collapse
Affiliation(s)
- Lynne Chantranupong
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Rachel L Wolfson
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - David M Sabatini
- Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology, Department of Biology, 9 Cambridge Center, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
| |
Collapse
|
31
|
Weiner ID, Verlander JW. Ammonia transport in the kidney by Rhesus glycoproteins. Am J Physiol Renal Physiol 2014; 306:F1107-20. [PMID: 24647713 PMCID: PMC4024734 DOI: 10.1152/ajprenal.00013.2014] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 03/14/2014] [Indexed: 12/26/2022] Open
Abstract
Renal ammonia metabolism is a fundamental element of acid-base homeostasis, comprising a major component of both basal and physiologically altered renal net acid excretion. Over the past several years, a fundamental change in our understanding of the mechanisms of renal epithelial cell ammonia transport has occurred, replacing the previous model which was based upon diffusion equilibrium for NH3 and trapping of NH4(+) with a new model in which specific and regulated transport of both NH3 and NH4(+) across renal epithelial cell membranes via specific membrane proteins is required for normal ammonia metabolism. A major advance has been the recognition that members of a recently recognized transporter family, the Rhesus glycoprotein family, mediate critical roles in renal and extrarenal ammonia transport. The erythroid-specific Rhesus glycoprotein, Rh A Glycoprotein (Rhag), was the first Rhesus glycoprotein recognized as an ammonia-specific transporter. Subsequently, the nonerythroid Rh glycoproteins, Rh B Glycoprotein (Rhbg) and Rh C Glycoprotein (Rhcg), were cloned and identified as ammonia transporters. They are expressed in specific cell populations and membrane domains in distal renal epithelial cells, where they facilitate ammonia secretion. In this review, we discuss the distribution of Rhbg and Rhcg in the kidney, the regulation of their expression and activity in physiological disturbances, the effects of genetic deletion on renal ammonia metabolism, and the molecular mechanisms of Rh glycoprotein-mediated ammonia transport.
Collapse
Affiliation(s)
- I David Weiner
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and Division of Nephrology, Hypertension, and Transplantation, University of Florida College of Medicine, Gainesville, Florida
| | - Jill W Verlander
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville Florida; and
| |
Collapse
|
32
|
Nakhoul NL, Lee Hamm L. The challenge of determining the role of Rh glycoproteins in transport of NH3and NH4+. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/wmts.105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nazih L. Nakhoul
- Department of Physiology; Tulane University Medical School; New Orleans LA USA
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
| | - L. Lee Hamm
- Department of Medicine, Section of Nephrology; Tulane University Medical School; New Orleans LA USA
| |
Collapse
|
33
|
Dance I. A molecular pathway for the egress of ammonia produced by nitrogenase. Sci Rep 2013; 3:3237. [PMID: 24241241 PMCID: PMC3831235 DOI: 10.1038/srep03237] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 11/01/2013] [Indexed: 01/19/2023] Open
Abstract
Nitrogenase converts N2 to NH3, at one face of an Fe-Mo-S cluster (FeMo-co) buried in the protein. Through exploration of cavities in the structures of nitrogenase proteins, a pathway for the egress of ammonia from its generation site to the external medium is proposed. This pathway is conserved in the three species Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum. A molecular mechanism for the translocation of NH3 by skipping through a sequence of hydrogen bonds involving eleven water molecules and surrounding aminoacids has been developed. The putative mechanism requires movement aside of some water molecules by up to ~ 1Å. Consistent with this, the surrounding protein is comprised of different chains and has little secondary structure: protein fluctuations are part of the mechanism. This NH3 pathway is well separated from the water chain and embedded proton wire that have been proposed for serial supply of protons to FeMo-co. Verification procedures are suggested.
Collapse
Affiliation(s)
- Ian Dance
- School of Chemistry, University of New South Wales, Sydney 2052, Australia
| |
Collapse
|
34
|
Characteristics of mammalian Rh glycoproteins (SLC42 transporters) and their role in acid-base transport. Mol Aspects Med 2013; 34:629-37. [PMID: 23506896 DOI: 10.1016/j.mam.2012.05.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 04/16/2012] [Indexed: 01/06/2023]
Abstract
The mammalian Rh glycoproteins belong to the solute transporter family SLC42 and include RhAG, present in red blood cells, and two non-erythroid members RhBG and RhCG that are expressed in various tissues, including kidney, liver, skin and the GI tract. The Rh proteins in the red blood cell form an "Rh complex" made up of one D-subunit, one CE-subunit and two RhAG subunits. The Rh complex has a well-known antigenic effect but also contributes to the stability of the red cell membrane. RhBG and RhCG are related to the NH4(+) transporters of the yeast and bacteria but their exact function is yet to be determined. This review describes the expression and molecular properties of these membrane proteins and their potential role as NH3/NH4(+) and CO2 transporters. The likelihood that these proteins transport gases such as CO2 or NH3 is novel and significant. The review also describes the physiological importance of these proteins and their relevance to human disease.
Collapse
|
35
|
Deschuyteneer A, Boeckstaens M, De Mees C, Van Vooren P, Wintjens R, Marini AM. SNPs altering ammonium transport activity of human Rhesus factors characterized by a yeast-based functional assay. PLoS One 2013; 8:e71092. [PMID: 23967154 PMCID: PMC3742762 DOI: 10.1371/journal.pone.0071092] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 06/24/2013] [Indexed: 01/23/2023] Open
Abstract
Proteins of the conserved Mep-Amt-Rh family, including mammalian Rhesus factors, mediate transmembrane ammonium transport. Ammonium is an important nitrogen source for the biosynthesis of amino acids but is also a metabolic waste product. Its disposal in urine plays a critical role in the regulation of the acid/base homeostasis, especially with an acid diet, a trait of Western countries. Ammonium accumulation above a certain concentration is however pathologic, the cytotoxicity causing fatal cerebral paralysis in acute cases. Alteration in ammonium transport via human Rh proteins could have clinical outcomes. We used a yeast-based expression assay to characterize human Rh variants resulting from non synonymous single nucleotide polymorphisms (nsSNPs) with known or unknown clinical phenotypes and assessed their ammonium transport efficiency, protein level, localization and potential trans-dominant impact. The HsRhAG variants (I61R, F65S) associated to overhydrated hereditary stomatocytosis (OHSt), a disease affecting erythrocytes, proved affected in intrinsic bidirectional ammonium transport. Moreover, this study reveals that the R202C variant of HsRhCG, the orthologue of mouse MmRhcg required for optimal urinary ammonium excretion and blood pH control, shows an impaired inherent ammonium transport activity. Urinary ammonium excretion was RHcg gene-dose dependent in mouse, highlighting MmRhcg as a limiting factor. HsRhCG(R202C) may confer susceptibility to disorders leading to metabolic acidosis for instance. Finally, the analogous R211C mutation in the yeast ScMep2 homologue also impaired intrinsic activity consistent with a conserved functional role of the preserved arginine residue. The yeast expression assay used here constitutes an inexpensive, fast and easy tool to screen nsSNPs reported by high throughput sequencing or individual cases for functional alterations in Rh factors revealing potential causal variants.
Collapse
Affiliation(s)
- Aude Deschuyteneer
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Mélanie Boeckstaens
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Christelle De Mees
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - Pascale Van Vooren
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
| | - René Wintjens
- Laboratoire des Biopolymères et des nanomatériaux supramoléculaires, Université Libre de Bruxelles, Brussels, Belgium
| | - Anna Maria Marini
- Biologie du Transport Membranaire, Université Libre de Bruxelles, Gosselies, Belgium
- * E-mail:
| |
Collapse
|
36
|
De Michele R, Ast C, Loqué D, Ho CH, Andrade SLA, Lanquar V, Grossmann G, Gehne S, Kumke MU, Frommer WB. Fluorescent sensors reporting the activity of ammonium transceptors in live cells. eLife 2013; 2:e00800. [PMID: 23840931 PMCID: PMC3699834 DOI: 10.7554/elife.00800] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 05/18/2013] [Indexed: 01/14/2023] Open
Abstract
Ammonium serves as key nitrogen source and metabolic intermediate, yet excess causes toxicity. Ammonium uptake is mediated by ammonium transporters, whose regulation is poorly understood. While transport can easily be characterized in heterologous systems, measuring transporter activity in vivo remains challenging. Here we developed a simple assay for monitoring activity in vivo by inserting circularly-permutated GFP into conformation-sensitive positions of two plant and one yeast ammonium transceptors (‘AmTrac’ and ‘MepTrac’). Addition of ammonium to yeast cells expressing the sensors triggered concentration-dependent fluorescence intensity (FI) changes that strictly correlated with the activity of the transporter. Fluorescence-based activity sensors present a novel technology for monitoring the interaction of the transporters with their substrates, the activity of transporters and their regulation in vivo, which is particularly valuable in the context of analytes for which no radiotracers exist, as well as for cell-specific and subcellular transport processes that are otherwise difficult to track. DOI:http://dx.doi.org/10.7554/eLife.00800.001 Ammonium provides a vital source of nitrogen for bacteria, fungi and plants, and is produced by animals as a waste product of metabolism. High levels of ammonium can be toxic, so all organisms need to control their uptake or excretion of this substance. Ammonium transporters, which are highly conserved from bacteria to plants to humans, are essential for this process but, along with transporters in general, they are hard to study. Their activity can be examined in vitro by expressing them in heterologous systems—that is, in cells other than those in which they are naturally found. But in vivo studies must rely on indirect techniques such as monitoring radioactive isotopes or membrane potentials, and these cannot distinguish between the activity of ammonium transporters and uptake of ammonium through other routes. One approach that has been successful in other fields is the use of fluorescent proteins that can signal conformational changes—such as those that occur when a transporter is activated—by a shift in fluorescence. Green fluorescent protein (GFP) is a commonly used fluorescent indicator, and a particularly useful variant is ‘circularly permutated GFP’. This is GFP in which parts of the amino acid sequence have been rearranged without fundamentally changing the overall structure or function of the protein. Circularly permutated GFP can be fused to another protein in such a way that a conformational change in the second protein triggers a change in fluorescence that can be detected by fluorescence spectroscopy or microscopy. Now, De Michele et al. have applied this approach to the study of both plant and yeast ammonium transporters. They constructed a library of fusion proteins made up of circularly permutated GFP and an ammonium transporter from the plant Arabidopsis thaliana—and found one version that functioned normally as a transporter but also produced a detectable change in fluorescence that correlated precisely with transporter activity. De Michele et al. then used the same method to produce fluorescent indicator fusion proteins of two more ammonium transporters—a second isoform from Arabidopsis and one from yeast. These fluorescent sensors should be a great boon to researchers studying the ammonium transport system. Moreover, this approach could in theory be applied to other transporter proteins that are currently difficult to study, and so could help to open up research into a variety of transport processes. DOI:http://dx.doi.org/10.7554/eLife.00800.002
Collapse
Affiliation(s)
- Roberto De Michele
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States.,Institute of Plant Genetics, Italian National Research Council (CNR-IGV), Palermo, Italy
| | - Cindy Ast
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States.,NanoPolyPhotonik, Fraunhofer Institute for Applied Polymer Research, Potsdam-Golm, Germany
| | - Dominique Loqué
- Feedstocks Division, Joint BioEnergy Institute, Emeryville, United States
| | - Cheng-Hsun Ho
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Susana LA Andrade
- Department of Biochemistry, Institute for Organic Chemistry and Biochemistry, and BIOSS Center for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Viviane Lanquar
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Guido Grossmann
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Sören Gehne
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Michael U Kumke
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Wolf B Frommer
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| |
Collapse
|
37
|
De Michele R, Ast C, Loqué D, Ho CH, Andrade SLA, Lanquar V, Grossmann G, Gehne S, Kumke MU, Frommer WB. Fluorescent sensors reporting the activity of ammonium transceptors in live cells. eLife 2013; 2:e00800. [PMID: 23840931 DOI: 10.7554/elife.00800.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 05/18/2013] [Indexed: 05/26/2023] Open
Abstract
Ammonium serves as key nitrogen source and metabolic intermediate, yet excess causes toxicity. Ammonium uptake is mediated by ammonium transporters, whose regulation is poorly understood. While transport can easily be characterized in heterologous systems, measuring transporter activity in vivo remains challenging. Here we developed a simple assay for monitoring activity in vivo by inserting circularly-permutated GFP into conformation-sensitive positions of two plant and one yeast ammonium transceptors ('AmTrac' and 'MepTrac'). Addition of ammonium to yeast cells expressing the sensors triggered concentration-dependent fluorescence intensity (FI) changes that strictly correlated with the activity of the transporter. Fluorescence-based activity sensors present a novel technology for monitoring the interaction of the transporters with their substrates, the activity of transporters and their regulation in vivo, which is particularly valuable in the context of analytes for which no radiotracers exist, as well as for cell-specific and subcellular transport processes that are otherwise difficult to track. DOI:http://dx.doi.org/10.7554/eLife.00800.001.
Collapse
Affiliation(s)
- Roberto De Michele
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
- Institute of Plant Genetics, Italian National Research Council (CNR-IGV), Palermo, Italy
| | - Cindy Ast
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
- NanoPolyPhotonik, Fraunhofer Institute for Applied Polymer Research, Potsdam-Golm, Germany
| | - Dominique Loqué
- Feedstocks Division, Joint BioEnergy Institute, Emeryville, United States
| | - Cheng-Hsun Ho
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Susana LA Andrade
- Department of Biochemistry, Institute for Organic Chemistry and Biochemistry, and BIOSS Center for Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Viviane Lanquar
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Guido Grossmann
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| | - Sören Gehne
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Michael U Kumke
- Department of Physical Chemistry, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Wolf B Frommer
- Department of Plant Biology, Carnegie Institution for Science, Stanford, United States
| |
Collapse
|
38
|
High-throughput genome sequencing of lichenizing fungi to assess gene loss in the ammonium transporter/ammonia permease gene family. BMC Genomics 2013; 14:225. [PMID: 23557360 PMCID: PMC3663718 DOI: 10.1186/1471-2164-14-225] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 02/13/2013] [Indexed: 11/20/2022] Open
Abstract
Background Horizontal gene transfer has shaped the evolution of the ammonium transporter/ammonia permease gene family. Horizontal transfers of ammonium transporter/ammonia permease genes into the fungi include one transfer from archaea to the filamentous ascomycetes associated with the adaptive radiation of the leotiomyceta. The horizontally transferred gene has subsequently been lost in most of the group but has been selectively retained in lichenizing fungi. However, some groups of lichens appear to have secondarily lost the archaeal ammonium transporter. Definitive assessment of gene loss can only be made via whole genome sequencing. Results Ammonium transporter/ammonia permease gene sequences were recovered from the assembled genomes of eight lichenizing fungi in key clades including the Caliciales, the Peltigerales, the Ostropomycetidae, the Acarosporomycetidae, the Verrucariales, the Arthoniomycetidae and the Lichinales. The genes recovered were included in a refined phylogenetic analysis. The hypothesis that lichens symbiotic with a nitrogen-fixing cyanobacterium as a primary photobiont or lichens living in high nitrogen environments lose the plant-like ammonium transporters was upheld, but did not account for additional losses of ammonium transporters/ammonia permeases in the lichens from the Acarosporomycetidae, Chaetotheriomycetes and Arthoniomycetes. In addition, the four ammonium transporter/ammonia permease genes from Cladonia grayi were shown to be functional by expressing the lichen genes in a strain of Saccharomyces cerevisiae in which all three native ammonium transporters were deleted, and assaying for growth on limiting ammonia as a sole nitrogen source. Conclusions Given sufficient coverage, next-generation sequencing technology can definitively address the loss of a gene in a genome when using environmental DNA isolated from lichen thalli collected from their natural habitats. Lichen-forming fungi have been losing ammonium transporters/ammonia permease genes at a slower rate than the most closely related non-lichenized lineages. These horizontally transferred genes in the Cladonia grayi genome encode functional ammonium transporters/ammonia permeases.
Collapse
|
39
|
Orabi EA, Lamoureux G. Polarizable Interaction Model for Liquid, Supercritical, and Aqueous Ammonia. J Chem Theory Comput 2013; 9:2035-51. [DOI: 10.1021/ct301123j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Esam A. Orabi
- Department of Chemistry
and Biochemistry and Centre
for Research in Molecular Modeling (CERMM), Concordia University,
7141 Sherbrooke Street West, Montréal, Québec H4B 1R6,
Canada
| | - Guillaume Lamoureux
- Department of Chemistry
and Biochemistry and Centre
for Research in Molecular Modeling (CERMM), Concordia University,
7141 Sherbrooke Street West, Montréal, Québec H4B 1R6,
Canada
| |
Collapse
|
40
|
Retracted article: ammonium transport proteins from Archaeoglobus fulgidus. J Physiol Biochem 2013; 69:963. [PMID: 23385667 DOI: 10.1007/s13105-012-0205-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 07/26/2012] [Indexed: 10/28/2022]
|
41
|
Cooper CA, Wilson JM, Wright PA. Marine, freshwater and aerially acclimated mangrove rivulus (Kryptolebias marmoratus) use different strategies for cutaneous ammonia excretion. Am J Physiol Regul Integr Comp Physiol 2013; 304:R599-612. [PMID: 23389109 DOI: 10.1152/ajpregu.00228.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Rhesus (Rh) glycoproteins are ammonia gas (NH(3)) channels known to be involved in ammonia transport in animals. Because of the different osmoregulatory and ionoregulatory challenges faced by teleost fishes in marine and freshwater (FW) environments, we hypothesized that ammonia excretion strategies would differ between environments. Also, we hypothesized that cutaneous NH(3) volatilization in air-acclimated fish is facilitated by base secretion. To test these hypotheses, we used the skin of the euryhaline amphibious mangrove rivulus (Kryptolebias marmoratus). The skin excretes ammonia and expresses Rh glycoproteins. Serosal-to-mucosal cutaneous ammonia flux was saturable (0-16 mmol/l ammonia, K(m) of 6.42 mmol/l). In FW, ammonia excretion increased in response to low mucosal pH but decreased with pharmacological inhibition of Na(+)/H(+) exchangers (NHE) and H(+) ATPase. Conversely, in brackish water (BW), lowering the mucosal pH significantly decreased ammonia excretion. Inhibitors of NHE also decreased ammonia excretion in BW fish. Immunofluorescence microscopy demonstrated that both the Rh isoform, Rhcg1, and NHE3 proteins colocalized in Na(+)/K(+) ATPase expressing mitochondrion-rich cells in the gills, kidney, and skin. We propose that the mechanisms of cutaneous ammonia excretion in FW K. marmoratus are consistent with the model for branchial ammonia excretion in FW teleost fish. NH(4)(+) excretion appeared to play a stronger role in BW. NH(4)(+) excretion in BW may be facilitated by apical NHE and/or diffuse through paracellular pathways. In aerially acclimated fish, inhibition of NHE and H(+) ATPase, but not the Cl(-)/HCO(3)(-) exchanger, significantly affected cutaneous surface pH, suggesting that direct base excretion is not critical for NH(3) volatilization. Overall, K. marmoratus use different strategies for excreting ammonia in three different environments, FW, BW, and air, and Rh glycoproteins and NHE are integral to all.
Collapse
|
42
|
Wang S, Orabi EA, Baday S, Bernèche S, Lamoureux G. Ammonium Transporters Achieve Charge Transfer by Fragmenting Their Substrate. J Am Chem Soc 2012; 134:10419-27. [DOI: 10.1021/ja300129x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shihao Wang
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
| | - Esam A. Orabi
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
| | - Sefer Baday
- Swiss Institute of Bioinformatics
and Biozentrum, University of Basel, Klingelbergstrasse
50/70, CH-4056 Basel, Switzerland
| | - Simon Bernèche
- Swiss Institute of Bioinformatics
and Biozentrum, University of Basel, Klingelbergstrasse
50/70, CH-4056 Basel, Switzerland
| | - Guillaume Lamoureux
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
| |
Collapse
|
43
|
Flatt JF, Musa RH, Ayob Y, Hassan A, Asidin N, Yahya NM, Mathlouthi R, Thornton N, Anstee DJ, Bruce LJ. Study of the D-- phenotype reveals erythrocyte membrane alterations in the absence of RHCE. Br J Haematol 2012; 158:262-273. [PMID: 22571328 DOI: 10.1111/j.1365-2141.2012.09149.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/27/2012] [Indexed: 02/04/2023]
Abstract
Red cells with the D-- phenotype do not express the RHCE protein because of mutations in both alleles of the RHCE gene. At present, little is known of the effect this has on the normal function of erythrocytes. In this study a group of five families belonging to a nomadic tribe in Malaysia were identified as carriers of the D-- haplotype. Analysis of homozygous individuals' genomic DNA showed two separate novel mutations. In four of the families, RHCE exons 1, 9 and 10 were present, while the 5th family possessed RHCE exons 1-3 and 10. Analysis of cDNA revealed hybrid transcripts, suggesting a gene conversion event with RHD, consistent with previously reported D-- mutations. Immunoblotting analysis of D-- erythrocyte membrane proteins found that Rh-associated glycoprotein (RHAG) migrates with altered electrophoretic mobility on sodium dodecyl sulphate polyacrylamide gel electrophoresis, consistent with increased glycosylation. Total amounts of Rh polypeptide in D-- membranes were comparable with controls, indicating that the exalted D antigen displayed by D-- red cells may be associated with altered surface epitope presentation. The adhesion molecules CD44 and CD47 are significantly reduced in D--. Together these results suggest that absence of RHCE polypeptide alters the structure and packing of the band 3/Rh macrocomplex.
Collapse
Affiliation(s)
- Joanna F Flatt
- Bristol Institute for Transfusion Sciences, N.H.S. Blood and Transplant, Filton, Bristol, UK
| | - Rozi H Musa
- Immunohaematology Division, National Blood Centre, Kuala Lumpur, Malaysia
| | - Yasmin Ayob
- Immunohaematology Division, National Blood Centre, Kuala Lumpur, Malaysia
| | - Afifah Hassan
- Immunohaematology Division, National Blood Centre, Kuala Lumpur, Malaysia
| | - Norhanim Asidin
- Immunohaematology Division, National Blood Centre, Kuala Lumpur, Malaysia
| | - Nurul M Yahya
- Immunohaematology Division, National Blood Centre, Kuala Lumpur, Malaysia
| | - Rosalind Mathlouthi
- International Blood Group Reference Laboratory, N.H.S. Blood and Transplant, Filton, Bristol, UK
| | - Nicole Thornton
- International Blood Group Reference Laboratory, N.H.S. Blood and Transplant, Filton, Bristol, UK
| | - David J Anstee
- Bristol Institute for Transfusion Sciences, N.H.S. Blood and Transplant, Filton, Bristol, UK
| | - Lesley J Bruce
- Bristol Institute for Transfusion Sciences, N.H.S. Blood and Transplant, Filton, Bristol, UK
| |
Collapse
|
44
|
Weihrauch D, Donini A, O'Donnell MJ. Ammonia transport by terrestrial and aquatic insects. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:473-87. [PMID: 22100291 DOI: 10.1016/j.jinsphys.2011.11.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/03/2011] [Accepted: 11/04/2011] [Indexed: 05/13/2023]
Abstract
Ammonia, an end product from amino acid and nucleic acid metabolism, is highly toxic for most animals. This review will provide an update on nitrogen metabolism in terrestrial and aquatic insects with emphasis on ammonia generation and transport. Aspects that will be discussed include metabolic pathways of nitrogenous compounds, the origin of ammonia and other nitrogenous waste products, ammonia toxicity, putative ammonia transporters as well as ammonia transport processes known in insects. Ammonia transport mechanisms in the mosquito Aedes aegypti, the tobacco hornworm Manduca sexta and the locust Schistocerca gregaria will be discussed in detail while providing additional, novel data.
Collapse
Affiliation(s)
- Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada R3T2N2.
| | | | | |
Collapse
|
45
|
Rodela TM, Esbaugh AJ, Weihrauch D, Veauvy CM, McDonald MD, Gilmour KM, Walsh PJ. Revisiting the effects of crowding and feeding in the gulf toadfish, Opsanus beta: the role of Rhesus glycoproteins in nitrogen metabolism and excretion. J Exp Biol 2012; 215:301-13. [DOI: 10.1242/jeb.061879] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
SUMMARY
Models of branchial transport in teleosts have been reshaped by the recent discovery of Rhesus (Rh) glycoproteins, a family of proteins that facilitate the movement of NH3 across cell membranes. This study examines the effects of crowding and feeding on ammonia excretion in gulf toadfish (Opsanus beta) within the context of Rh glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). Four Rh isoforms (Rhag, Rhbg, Rhcg1 and Rhcg2) were isolated from toadfish. Tissue distributions showed higher levels of mRNA expression in the gills and liver, moderate levels in the intestine and lower levels in the stomach. Crowding significantly lowered branchial Rh expression and ammonia excretion rates in fasted toadfish. A comparison of Rh expression in the digestive tract revealed relatively low levels of Rhcg1 and Rhcg2 in the stomach and high mRNA abundance of Rhbg, Rhcg1 and Rhcg2 in the intestine of fasted, crowded toadfish. We speculate that these trends may reduce secretion and enhance absorption, respectively, to minimize the amount of ammonia that is lost through gastrointestinal routes. By contrast, these patterns of expression were modified in response to an exogenous ammonia load via feeding. Post-prandial ammonia excretion rates were elevated twofold, paralleled by similar increases in branchial Rhcg1 mRNA, gastric Rhcg1 mRNA and mRNA of all intestinal Rh isoforms. These changes were interpreted as an attempt to increase post-prandial ammonia excretion rates into the environment owing to a gradient created by elevated circulating ammonia concentrations and acidification of the digestive tract. Overall, we provide evidence that toadfish modulate both the expression of Rh isoforms and urea synthesis pathways to tightly control and regulate nitrogen excretion.
Collapse
Affiliation(s)
- Tamara M. Rodela
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Andrew J. Esbaugh
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
| | - Clémence M. Veauvy
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA
| | - M. Danielle McDonald
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA
| | - Kathleen M. Gilmour
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Patrick J. Walsh
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| |
Collapse
|
46
|
Rodela TM, McDonald MD, Walsh PJ, Gilmour KM. Interactions between cortisol and Rhesus glycoprotein expression in ureogenic toadfish, Opsanus beta. J Exp Biol 2012; 215:314-23. [DOI: 10.1242/jeb.061895] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
SUMMARY
In their native environment, gulf toadfish excrete equal quantities of ammonia and urea. However, upon exposure to stressful conditions in the laboratory (i.e. crowding, confinement or air exposure), toadfish decrease branchial ammonia excretion and become ureotelic. The objective of this study was to determine the influences of cortisol and ammonia on ammonia excretion relative to expression of Rhesus (Rh) glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). In vivo infusions and/or injections were used to manipulate corticosteroid activity and plasma ammonia concentrations in ureotelic toadfish. Metyrapone treatment to lower circulating cortisol levels resulted in a 3.5-fold elevation of ammonia excretion rates, enhanced mRNA expression of two of the toadfish Rh isoforms (Rhcg1 and Rhcg2), and decreased branchial and hepatic GS activity. Correspondingly, cortisol infusion decreased ammonia excretion 2.5-fold, a change that was accompanied by reduced branchial expression of all toadfish Rh isoforms (Rhag, Rhbg, Rhcg1 and Rhcg2) and a twofold increase in hepatic GS activity. In contrast, maintenance of high circulating ammonia levels by ammonia infusion enhanced ammonia excretion and Rh expression (Rhag, Rhbg and Rhcg2). Toadfish treated with cortisol showed an attenuated response to ammonia infusion with no change in Rh mRNA expression or GS activity. In summary, the evidence suggests that ammonia excretion in toadfish is modulated by cortisol-induced changes in both Rh glycoprotein expression and GS activity.
Collapse
Affiliation(s)
- Tamara M. Rodela
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - M. Danielle McDonald
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149-1098, USA
| | - Patrick J. Walsh
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| | - Kathleen M. Gilmour
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
| |
Collapse
|
47
|
Anderson WG, Nawata CM, Wood CM, Piercey-Normore MD, Weihrauch D. Body fluid osmolytes and urea and ammonia flux in the colon of two chondrichthyan fishes, the ratfish, Hydrolagus colliei, and spiny dogfish, Squalus acanthias. Comp Biochem Physiol A Mol Integr Physiol 2012; 161:27-35. [PMID: 21911071 DOI: 10.1016/j.cbpa.2011.08.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 08/29/2011] [Accepted: 08/29/2011] [Indexed: 12/29/2022]
Abstract
The present study has examined the role of the colon in regulating ammonia and urea nitrogen balance in two species of chondrichthyans, the ratfish, Hydrolagus colliei (a holocephalan) and the spiny dogfish, Squalus acanthias (an elasmobranch). Stripped colonic tissue from both the dogfish and ratfish was mounted in an Ussing chamber and in both species bi-directional urea flux was found to be negligible. Urea uptake by the mucosa and serosa of the isolated colonic epithelium through accumulation of (14)C-urea was determined to be 2.8 and 6.2 fold greater in the mucosa of the dogfish compared to the serosa of the dogfish and the mucosa of the ratfish respectively. Furthermore, there was no difference between serosal and mucosal accumulation of (14)C-urea in the ratfish. Through the addition of 2mM NH(4)Cl to the mucosal side of each preparation the potential for ammonia flux was also examined. This was again found to be negligible in both species suggesting that the colon is an extremely tight epithelium to the movement of both urea and ammonia. Plasma, chyme and bile fluid samples were also taken from the agastric ratfish and were compared with solute concentrations of equivalent body fluids in the dogfish. Finally molecular analysis revealed expression of 3 isoforms of the urea transport protein (UT) and an ammonia transport protein (Rhbg) in the gill, intestine, kidney and colon of the ratfish. Partial nucleotide sequences of the UT-1, 2 and 3 isoforms in the ratfish had 95, 95 and 92% identity to the equivalent UT isoforms recently identified in another holocephalan, the elephantfish, Callorhinchus milii. Finally, the nucleotide sequence of the Rhbg identified in the ratfish had 73% identity to the Rhbg protein recently identified in the little skate, Leucoraja erinacea.
Collapse
Affiliation(s)
- W Gary Anderson
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada.
| | | | | | | | | |
Collapse
|
48
|
McDonald TR, Dietrich FS, Lutzoni F. Multiple horizontal gene transfers of ammonium transporters/ammonia permeases from prokaryotes to eukaryotes: toward a new functional and evolutionary classification. Mol Biol Evol 2012; 29:51-60. [PMID: 21680869 PMCID: PMC3383101 DOI: 10.1093/molbev/msr123] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The proteins of the ammonium transporter/methylammonium permease/Rhesus factor family (AMT/MEP/Rh family) are responsible for the movement of ammonia or ammonium ions across the cell membrane. Although it has been established that the Rh proteins are distantly related to the other members of the family, the evolutionary history of the AMT/MEP/Rh family remains unclear. Here, we use phylogenetic analysis to infer the evolutionary history of this family of proteins across 191 genomes representing all main lineages of life and to provide a new classification of the proteins in this family. Our phylogenetic analysis suggests that what has heretofore been conceived of as a protein family with two clades (AMT/MEP and Rh) is instead a protein family with three clades (AMT, MEP, and Rh). We show that the AMT/MEP/Rh family illustrates two contrasting modes of gene transmission: The AMT family as defined here exhibits vertical gene transfer (i.e., standard parent-to-offspring inheritance), whereas the MEP family as defined here is characterized by several ancient independent horizontal gene transfers (HGTs). These ancient HGT events include a gene replacement during the early evolution of the fungi, which could be a defining trait for the kingdom Fungi, a gene gain from hyperthermophilic chemoautolithotrophic prokaryotes during the early evolution of land plants (Embryophyta), and an independent gain of this same gene in the filamentous ascomycetes (Pezizomycotina) that was subsequently lost in most lineages but retained in even distantly related lichenized fungi. This recircumscription of the ammonium transporters/ammonia permeases family into MEP and AMT families informs the debate on the mechanism of transport in these proteins and on the nature of the transported molecule because published crystal structures of proteins from the MEP and Rh clades may not be representative of the AMT clade. The clades as depicted in this phylogenetic study appear to correspond to functionally different groups, with AMTs and ammonia permeases forming two distinct and possibly monophyletic groups.
Collapse
|
49
|
Rodrigues TE, Souza VEP, Monteiro RA, Gerhardt ECM, Araújo LM, Chubatsu LS, Souza EM, Pedrosa FO, Huergo LF. In vitro interaction between the ammonium transport protein AmtB and partially uridylylated forms of the P(II) protein GlnZ. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1203-9. [PMID: 21645649 DOI: 10.1016/j.bbapap.2011.05.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 04/28/2011] [Accepted: 05/13/2011] [Indexed: 12/18/2022]
Abstract
The ammonium transport family Amt/Rh comprises ubiquitous integral membrane proteins that facilitate ammonium movement across biological membranes. Besides their role in transport, Amt proteins also play a role in sensing the levels of ammonium in the environment, a process that depends on complex formation with cytosolic proteins of the P(II) family. Trimeric P(II) proteins from a variety of organisms undergo a cycle of reversible posttranslational modification according to the prevailing nitrogen supply. In proteobacteria, P(II) proteins are subjected to reversible uridylylation of each monomer. In this study we used the purified proteins from Azospirillum brasilense to analyze the effect of P(II) uridylylation on the protein's ability to engage complex formation with AmtB in vitro. Our results show that partially uridylylated P(II) trimers can interact with AmtB in vitro, the implication of this finding in the regulation of nitrogen metabolism is discussed. We also report an improved expression and purification protocol for the A. brasilense AmtB protein that might be applicable to AmtB proteins from other organisms.
Collapse
Affiliation(s)
- Thiago E Rodrigues
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Hwang PP, Lee TH, Lin LY. Ion regulation in fish gills: recent progress in the cellular and molecular mechanisms. Am J Physiol Regul Integr Comp Physiol 2011; 301:R28-47. [PMID: 21451143 DOI: 10.1152/ajpregu.00047.2011] [Citation(s) in RCA: 299] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Fish encounter harsh ionic/osmotic gradients on their aquatic environments, and the mechanisms through which they maintain internal homeostasis are more challenging compared with those of terrestrial vertebrates. Gills are one of the major organs conducting the internal ionic and acid-base regulation, with specialized ionocytes as the major cells carrying out active transport of ions. Exploring the iono/osmoregulatory mechanisms in fish gills, extensive literature proposed several models, with many conflicting or unsolved issues. Recent studies emerged, shedding light on these issues with new opened windows on other aspects, on account of available advanced molecular/cellular physiological approaches and animal models. Respective types of ionocytes and ion transporters, and the relevant regulators for the mechanisms of NaCl secretion, Na(+) uptake/acid secretion/NH(4)(+) excretion, Ca(2+) uptake, and Cl(-) uptake/base secretion, were identified and functionally characterized. These new ideas broadened our understanding of the molecular/cellular mechanisms behind the functional modification/regulation of fish gill ion transport during acute and long-term acclimation to environmental challenges. Moreover, a model for the systematic and local carbohydrate energy supply to gill ionocytes during these acclimation processes was also proposed. These provide powerful platforms to precisely study transport pathways and functional regulation of specific ions, transporters, and ionocytes; however, very few model species were established so far, whereas more efforts are needed in other species.
Collapse
Affiliation(s)
- Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei 115, Taiwan.
| | | | | |
Collapse
|