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Mishra S, Welch N, Singh SS, Singh KD, Bellar A, Kumar A, Deutz LN, Hanlon MD, Kant S, Dastidar S, Patel H, Agrawal V, Attaway AH, Musich R, Stark GR, Tedesco FS, Truskey GA, Weiner ID, Karnik SS, Dasarathy S. Ammonia transporter RhBG initiates downstream signaling and functional responses by activating NFκB. Proc Natl Acad Sci U S A 2024; 121:e2314760121. [PMID: 39052834 PMCID: PMC11294993 DOI: 10.1073/pnas.2314760121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 06/19/2024] [Indexed: 07/27/2024] Open
Abstract
Transceptors, solute transporters that facilitate intracellular entry of molecules and also initiate intracellular signaling events, have been primarily studied in lower-order species. Ammonia, a cytotoxic endogenous metabolite, is converted to urea in hepatocytes for urinary excretion in mammals. During hyperammonemia, when hepatic metabolism is impaired, nonureagenic ammonia disposal occurs primarily in skeletal muscle. Increased ammonia uptake in skeletal muscle is mediated by a membrane-bound, 12 transmembrane domain solute transporter, Rhesus blood group-associated B glycoprotein (RhBG). We show that in addition to its transport function, RhBG interacts with myeloid differentiation primary response-88 (MyD88) to initiate an intracellular signaling cascade that culminates in activation of NFκB. We also show that ammonia-induced MyD88 signaling is independent of the canonical toll-like receptor-initiated mechanism of MyD88-dependent NFκB activation. In silico, in vitro, and in situ experiments show that the conserved cytosolic J-domain of the RhBG protein interacts with the Toll-interleukin-1 receptor (TIR) domain of MyD88. In skeletal muscle from human patients, human-induced pluripotent stem cell-derived myotubes, and myobundles show an interaction of RhBG-MyD88 during hyperammonemia. Using complementary experimental and multiomics analyses in murine myotubes and mice with muscle-specific RhBG or MyD88 deletion, we show that the RhBG-MyD88 interaction is essential for the activation of NFkB but not ammonia transport. Our studies show a paradigm of substrate-dependent regulation of transceptor function with the potential for modulation of cellular responses in mammalian systems by decoupling transport and signaling functions of transceptors.
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Affiliation(s)
- Saurabh Mishra
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Nicole Welch
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Gastroenterology and Hepatology, Lerner Research Institute, Cleveland, OH44195
| | - Shashi Shekhar Singh
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | | | - Annette Bellar
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Avinash Kumar
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Lars N. Deutz
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Maxmillian D. Hanlon
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Sashi Kant
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Sumitava Dastidar
- Department of Cell and Developmental Biology, University College London & The Francis Crick Institute, LondonWC1E6DE, UK
| | - Hailee Patel
- Duke Biomedical Engineering, Duke University, Durham, NC27708
| | - Vandana Agrawal
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Amy H. Attaway
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Pulmonary Medicine, Lerner Research Institute, Cleveland, OH44195
| | - Ryan Musich
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - George R. Stark
- Cancer Biology, Lerner Research Institute, Cleveland, OH44195
| | - Francesco Saverio Tedesco
- Department of Cell and Developmental Biology, University College London & The Francis Crick Institute, LondonWC1E6DE, UK
| | | | - I. David Weiner
- Division of Nephrology Hypertension, and Renal Transplantation, University of Florida, Gainesville, FL32610
- Nephrology and Hypertension Section, Gainesville, FL32610
| | - Sadashiva S. Karnik
- Cardiovascular and Metabolic Diseases, Lerner Research Institute, Cleveland, OH44195
| | - Srinivasan Dasarathy
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Gastroenterology and Hepatology, Lerner Research Institute, Cleveland, OH44195
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2
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Sudnitsyna J, Ruzhnikova TO, Panteleev MA, Kharazova A, Gambaryan S, Mindukshev IV. Chloride Gradient Is Involved in Ammonium Influx in Human Erythrocytes. Int J Mol Sci 2024; 25:7390. [PMID: 39000500 PMCID: PMC11242273 DOI: 10.3390/ijms25137390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Revised: 06/20/2024] [Accepted: 06/29/2024] [Indexed: 07/16/2024] Open
Abstract
The ammonia/ammonium (NH3/NH4+, AM) concentration in human erythrocytes (RBCs) is significantly higher than in plasma. Two main possible mechanisms for AM transport, including simple and facilitated diffusion, are described; however, the driving force for AM transport is not yet fully characterized. Since the erythroid ammonium channel RhAG forms a structural unit with anion exchanger 1 (eAE1) within the ankyrin core complex, we hypothesized the involvement of eAE1 in AM transport. To evaluate the functional interaction between eAE1 and RhAG, we used a unique feature of RBCs to swell and lyse in isotonic NH4+ buffer. The kinetics of cell swelling and lysis were analyzed by flow cytometry and an original laser diffraction method, adapted for accurate volume sensing. The eAE1 role was revealed according to (i) the changes in cell swelling and lysis kinetics, and (ii) changes in intracellular pH, triggered by eAE1 inhibition or the modulation of eAE1 main ligand concentrations (Cl- and HCO3-). Additionally, the AM import kinetics was analyzed enzymatically and colorimetrically. In NH4+ buffer, RBCs concentration-dependently swelled and lysed when [NH4+] exceeded 100 mM. Cell swelling and hemolysis were tightly regulated by chloride concentration. The complete substitution of chloride with glutamate prevented NH4+-induced cell swelling and hemolysis, and the restoration of [Cl-] dose-dependently amplified the rates of RBC swelling and lysis and the percentage of hemolyzed cells. Similarly, eAE1 inhibition impeded cell swelling and completely prevented hemolysis. Accordingly, eAE1 inhibition, or a lack of chloride anions in the buffer, significantly decreased NH4+ import. Our data indicate that the eAE1-mediated chloride gradient is required for AM transport. Taken together, our data reveal a new player in AM transport in RBCs.
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Affiliation(s)
- Julia Sudnitsyna
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, 30 Srednyaya Kalitnikovskaya St., 109029 Moscow, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Ave., 194223 Saint Petersburg, Russia
| | - Tamara O Ruzhnikova
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Ave., 194223 Saint Petersburg, Russia
- Department of Cytology and Histology, Saint Petersburg State University, 7/9 Universitetskaya Emb., 199034 Saint Petersburg, Russia
| | - Mikhail A Panteleev
- Center for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences, 30 Srednyaya Kalitnikovskaya St., 109029 Moscow, Russia
| | - Alexandra Kharazova
- Department of Cytology and Histology, Saint Petersburg State University, 7/9 Universitetskaya Emb., 199034 Saint Petersburg, Russia
| | - Stepan Gambaryan
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Ave., 194223 Saint Petersburg, Russia
| | - Igor V Mindukshev
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Ave., 194223 Saint Petersburg, Russia
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3
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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.
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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.
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4
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Liu W, Wang Y, Zhang Y, Zhou M, Gu H, Lu M, Xia Y. Rh family C glycoprotein contributes to psoriatic inflammation through regulating the dysdifferentiation and cytokine secretion of keratinocytes. J Dermatol Sci 2024; 114:2-12. [PMID: 38514279 DOI: 10.1016/j.jdermsci.2024.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 02/16/2024] [Accepted: 02/27/2024] [Indexed: 03/23/2024]
Abstract
BACKGROUND Keratinocyte dysdifferentiation and proinflammatory cytokine production play a central role in psoriatic inflammation. According to recent studies, the Rh family C glycoprotein (RHCG) enhances cell proliferation and disrupts cell differentiation. However, the specific role of RHCG psoriasis development remains unclear. OBJECTIVE We here explored the effect of RHCG on keratinocytes under psoriatic inflammation. METHODS The cell counting kit‑8 assay was conducted to assess proliferation. RHCG protein expression was assessed through western blotting and enzyme-linked immunosorbent assays. The expression of proinflammatory cytokines and differentiation markers was analyzed through a quantitative reverse-transcription polymerase chain reaction. RESULTS Both RHCG mRNA and protein levels increased in psoriatic skin. Notably, cultured keratinocytes treated with an M5 cocktail, which mimics psoriatic inflammation, exhibited higher RHCG expression. Furthermore, RHCG overexpression promoted keratinocyte proliferation, accompanied by an increase in the production of interleukin (IL)-1β, IL-6, and IL-8, and tumor necrosis factor-α. RHCG overexpression also resulted in higher expression of keratin 17, a differentiation marker. Conversely, RHCG gene knockdown reduced keratinocyte proliferation and cytokine secretion. RHCG inhibition in cells recovered both keratin 1 and loricrin expression. Additionally, RHCG overexpression facilitated the phosphorylation of nuclear factor-kappa B and extracellular signal-regulated protein kinase signaling pathways. Importantly, when these signaling pathways were inhibited, the effect of RHCG on keratinocytes was attenuated. CONCLUSION These findings support the substantial role of RHCG in psoriatic inflammation development and suggest that RHCG serves as a potential target for psoriasis treatment.
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Affiliation(s)
- Wei Liu
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yaqi Wang
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yitian Zhang
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Mingzhu Zhou
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Hanjiang Gu
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Mei Lu
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yumin Xia
- Department of Dermatology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China.
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5
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Bourgeois S, Houillier P. State of knowledge on ammonia handling by the kidney. Pflugers Arch 2024; 476:517-531. [PMID: 38448728 PMCID: PMC11006756 DOI: 10.1007/s00424-024-02940-1] [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: 12/21/2023] [Revised: 02/28/2024] [Accepted: 03/01/2024] [Indexed: 03/08/2024]
Abstract
The disposal of ammonia, the main proton buffer in the urine, is important for acid-base homeostasis. Renal ammonia excretion is the predominant contributor to renal net acid excretion, both under basal condition and in response to acidosis. New insights into the mechanisms of renal ammonia production and transport have been gained in the past decades. Ammonia is the only urinary solute known to be produced in the kidney and selectively transported through the different parts of the nephron. Both molecular forms of total ammonia, NH3 and NH4+, are transported by specific proteins. Proximal tubular ammoniagenesis and the activity of these transport processes determine the eventual fate of total ammonia produced and excreted by the kidney. In this review, we summarized the state of the art of ammonia handling by the kidney and highlighted the newest processes described in the last decade.
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Affiliation(s)
- Soline Bourgeois
- Institut of Physiology, University of Zurich, Zurich, Switzerland.
| | - Pascal Houillier
- Centre de Recherche Des Cordeliers, INSERM, Sorbonne Université, Université Paris Cité, Paris, France
- Centre National de La Recherche Scientifique (CNRS), EMR 8228, Paris, France
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6
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Kuhn C, Mohebbi N, Ritter A. Metabolic acidosis in chronic kidney disease: mere consequence or also culprit? Pflugers Arch 2024; 476:579-592. [PMID: 38279993 PMCID: PMC11006741 DOI: 10.1007/s00424-024-02912-5] [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: 11/15/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 01/29/2024]
Abstract
Metabolic acidosis is a frequent complication in non-transplant chronic kidney disease (CKD) and after kidney transplantation. It occurs when net endogenous acid production exceeds net acid excretion. While nephron loss with reduced ammoniagenesis is the main cause of acid retention in non-transplant CKD patients, additional pathophysiological mechanisms are likely inflicted in kidney transplant recipients. Functional tubular damage by calcineurin inhibitors seems to play a key role causing renal tubular acidosis. Notably, experimental and clinical studies over the past decades have provided evidence that metabolic acidosis may not only be a consequence of CKD but also a driver of disease. In metabolic acidosis, activation of hormonal systems and the complement system resulting in fibrosis have been described. Further studies of changes in renal metabolism will likely contribute to a deeper understanding of the pathophysiology of metabolic acidosis in CKD. While alkali supplementation in case of reduced serum bicarbonate < 22 mmol/l has been endorsed by CKD guidelines for many years to slow renal functional decline, among other considerations, beneficial effects and thresholds for treatment have lately been under intense debate. This review article discusses this topic in light of the most recent results of trials assessing the efficacy of dietary and pharmacological interventions in CKD and kidney transplant patients.
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Affiliation(s)
- Christian Kuhn
- Clinic for Nephrology and Transplantation Medicine, Cantonal Hospital St. Gallen, St. Gallen, Switzerland
| | | | - Alexander Ritter
- Clinic for Nephrology and Transplantation Medicine, Cantonal Hospital St. Gallen, St. Gallen, Switzerland.
- Clinic for Nephrology, University Hospital Zurich, Zurich, Switzerland.
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7
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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.
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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
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8
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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.
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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
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9
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Fehsenfeld S, Quijada-Rodriguez AR, Zhouyao H, Durant AC, Donini A, Sachs M, Eck P, Weihrauch D. Hiat1 as a new transporter involved in ammonia regulation. Sci Rep 2023; 13:4416. [PMID: 36932112 PMCID: PMC10023664 DOI: 10.1038/s41598-023-31503-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
The orphan transporter hippocampus-abundant transcript 1 (Hiat1) was first identified in the mammalian brain. Its specific substrate specificity, however, has not been investigated to date. Here, we identified and analyzed Hiat1 in a crustacean, the green crab Carcinus maenas. Our phylogenetic analysis showed that Hiat1 protein is conserved at a considerable level between mammals and this invertebrate (ca. 78% identical and conserved amino acids). Functional expression of Carcinus maenas Hiat1 in Xenopus laevis oocytes demonstrated the capability to transport ammonia (likely NH4+) in a sodium-dependent manner. Furthermore, applying quantitative polymerase chain reaction, our results indicated a physiological role for Carcinus maenas Hiat1 in ammonia homeostasis, as mRNA abundance increased in posterior gills in response to elevated circulating hemolymph ammonia upon exposure to high environmental ammonia. Its ubiquitous mRNA expression pattern also suggests an essential role in general cellular detoxification of ammonia. Overall, our results introduce a new ubiquitously expressed ammonia transporter, consequently demanding revision of our understanding of ammonia handling in key model systems from mammalian kidneys to crustacean and fish gills.
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Affiliation(s)
- Sandra Fehsenfeld
- Département de Biologie, Chimie et Géographie, Université du Quebec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada.
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada.
| | - Alex R Quijada-Rodriguez
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
| | - Haonan Zhouyao
- Department of Food and Human Nutritional Sciences, University of Manitoba, 35 Chancellor's Circle, Winnipeg, MB, R3T 2N2, Canada
| | - Andrea C Durant
- Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
| | - Andrew Donini
- Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
| | - Maria Sachs
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
| | - Peter Eck
- Department of Food and Human Nutritional Sciences, University of Manitoba, 35 Chancellor's Circle, Winnipeg, MB, R3T 2N2, Canada
| | - Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
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10
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Harris AN, Skankar M, Melanmed M, Batlle D. An Update on Kidney Ammonium Transport Along the Nephron. ADVANCES IN KIDNEY DISEASE AND HEALTH 2023; 30:189-196. [PMID: 36868733 DOI: 10.1053/j.akdh.2022.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 12/14/2022] [Indexed: 03/05/2023]
Abstract
Acid-base homeostasis is critical to the maintenance of normal health. The kidneys have a central role in bicarbonate generation, which occurs through the process of net acid excretion. Renal ammonia excretion is the predominant component of renal net acid excretion under basal conditions and in response to acid-base disturbances. Ammonia produced in the kidney is selectively transported into the urine or the renal vein. The amount of ammonia produced by the kidney that is excreted in the urine varies dramatically in response to physiological stimuli. Recent studies have advanced our understanding of ammonia metabolism's molecular mechanisms and regulation. Ammonia transport has been advanced by recognizing that the specific transport of NH3 and NH4+ by specific membrane proteins is critical to ammonia transport. Other studies show that proximal tubule protein, NBCe1, specifically the A variant, significantly regulates renal ammonia metabolism. This review discusses these critical aspects of the emerging features of ammonia metabolism and transport.
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Affiliation(s)
- Autumn N Harris
- Department of Small Animal Clinical Science, University of Florida College of Veterinary Medicine, Gainesville, FL; Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL.
| | - Mythri Skankar
- Department of Nephrology, Institute of Nephro-urology, Bengaluru, India
| | - Michal Melanmed
- Albert Einstein College of Medicine/ Montefiore Medical Center, Bronx, NY
| | - Daniel Batlle
- Northwestern University Feinberg School of Medicine, Chicago, IL
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11
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Imenez Silva PH, Mohebbi N. Kidney metabolism and acid-base control: back to the basics. Pflugers Arch 2022; 474:919-934. [PMID: 35513635 PMCID: PMC9338915 DOI: 10.1007/s00424-022-02696-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 01/18/2023]
Abstract
Kidneys are central in the regulation of multiple physiological functions, such as removal of metabolic wastes and toxins, maintenance of electrolyte and fluid balance, and control of pH homeostasis. In addition, kidneys participate in systemic gluconeogenesis and in the production or activation of hormones. Acid-base conditions influence all these functions concomitantly. Healthy kidneys properly coordinate a series of physiological responses in the face of acute and chronic acid-base disorders. However, injured kidneys have a reduced capacity to adapt to such challenges. Chronic kidney disease patients are an example of individuals typically exposed to chronic and progressive metabolic acidosis. Their organisms undergo a series of alterations that brake large detrimental changes in the homeostasis of several parameters, but these alterations may also operate as further drivers of kidney damage. Acid-base disorders lead not only to changes in mechanisms involved in acid-base balance maintenance, but they also affect multiple other mechanisms tightly wired to it. In this review article, we explore the basic renal activities involved in the maintenance of acid-base balance and show how they are interconnected to cell energy metabolism and other important intracellular activities. These intertwined relationships have been investigated for more than a century, but a modern conceptual organization of these events is lacking. We propose that pH homeostasis indissociably interacts with central pathways that drive progression of chronic kidney disease, such as inflammation and metabolism, independent of etiology.
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Affiliation(s)
- Pedro Henrique Imenez Silva
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.
| | - Nilufar Mohebbi
- National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
- Praxis Und Dialysezentrum Zurich, Zurich, Switzerland
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12
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Williamson G, Brito AS, Bizior A, Tamburrino G, Dias Mirandela G, Harris T, Hoskisson PA, Zachariae U, Marini AM, Boeckstaens M, Javelle A. Coexistence of Ammonium Transporter and Channel Mechanisms in Amt-Mep-Rh Twin-His Variants Impairs the Filamentation Signaling Capacity of Fungal Mep2 Transceptors. mBio 2022; 13:e0291321. [PMID: 35196127 PMCID: PMC9040831 DOI: 10.1128/mbio.02913-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 01/26/2022] [Indexed: 12/01/2022] Open
Abstract
Ammonium translocation through biological membranes, by the ubiquitous Amt-Mep-Rh family of transporters, plays a key role in all domains of life. Two highly conserved histidine residues protrude into the lumen of the pore of these transporters, forming the family's characteristic Twin-His motif. It has been hypothesized that the motif is essential to confer the selectivity of the transport mechanism. Here, using a combination of in vitro electrophysiology on Escherichia coli AmtB, in silico molecular dynamics simulations, and in vivo yeast functional complementation assays, we demonstrate that variations in the Twin-His motif trigger a mechanistic switch between a specific transporter, depending on ammonium deprotonation, to an unspecific ion channel activity. We therefore propose that there is no selective filter that governs specificity in Amt-Mep-Rh transporters, but the inherent mechanism of translocation, dependent on the fragmentation of the substrate, ensures the high specificity of the translocation. We show that coexistence of both mechanisms in single Twin-His variants of yeast Mep2 transceptors disrupts the signaling function and so impairs fungal filamentation. These data support a signaling process driven by the transport mechanism of the fungal Mep2 transceptors. IMPORTANCE Fungal infections represent a significant threat to human health and cause huge damage to crop yields worldwide. The dimorphic switch between yeast and filamentous growth is associated with the virulence of pathogenic fungi. Of note, fungal Mep2 proteins of the conserved Amt-Mep-Rh family play a transceptor role in the induction of filamentation; however, the signaling mechanism remains largely unknown. Amt-Mep-Rh proteins ensure the specific scavenging of NH4+ through a mechanism relying on substrate deprotonation, thereby preventing competition and translocation of similar-sized K+. Our multidisciplinary approaches using E. coli AmtB, Saccharomyces cerevisiae, and Candida albicans Mep2 show that double variation of the family-defining Twin-His motif triggers a mechanistic switch from a specific transporter to an unspecific ion channel with both mechanisms still coexisting in single variants. Moreover, we show that this mechanistic alteration is associated with loss of signaling ability of Mep2, supporting a transport mechanism-driven process in filamentation induction.
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Affiliation(s)
- Gordon Williamson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Ana Sofia Brito
- Biology of Membrane Transport Laboratory, Department of Molecular Biology, Université Libre de Bruxelles, Gosselies, Belgium
| | - Adriana Bizior
- 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
| | - Gaëtan Dias Mirandela
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
- Biology of Membrane Transport Laboratory, Department of Molecular Biology, Université Libre de Bruxelles, Gosselies, Belgium
| | - Thomas Harris
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, 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
| | - Anna Maria Marini
- Biology of Membrane Transport Laboratory, Department of Molecular Biology, Université Libre de Bruxelles, Gosselies, Belgium
| | - Mélanie Boeckstaens
- Biology of Membrane Transport Laboratory, Department of Molecular Biology, Université Libre de Bruxelles, Gosselies, Belgium
| | - Arnaud Javelle
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
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13
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Clifford AM, Tresguerres M, Goss GG, Wood CM. A novel K + -dependent Na + uptake mechanism during low pH exposure in adult zebrafish (Danio rerio): New tricks for old dogma. Acta Physiol (Oxf) 2022; 234:e13777. [PMID: 34985194 DOI: 10.1111/apha.13777] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 09/27/2021] [Accepted: 01/01/2022] [Indexed: 12/16/2022]
Abstract
AIM To determine whether Na+ uptake in adult zebrafish (Danio rerio) exposed to acidic water adheres to traditional models reliant on Na+ /H+ Exchangers (NHEs), Na+ channels and Na+ /Cl- Cotransporters (NCCs) or if it occurs through a novel mechanism. METHODS Zebrafish were exposed to control (pH 8.0) or acidic (pH 4.0) water for 0-12 hours during which 22 Na+ uptake ( J Na in ), ammonia excretion, net acidic equivalent flux and net K+ flux ( J H net ) were measured. The involvement of NHEs, Na+ channels, NCCs, K+ -channels and K+ -dependent Na+ /Ca2+ exchangers (NCKXs) was evaluated by exposure to Cl- -free or elevated [K+ ] water, or to pharmacological inhibitors. The presence of NCKXs in gill was examined using RT-PCR. RESULTS J Na in was strongly attenuated by acid exposure, but gradually recovered to control rates. The systematic elimination of each of the traditional models led us to consider K+ as a counter substrate for Na+ uptake during acid exposure. Indeed, elevated environmental [K+ ] inhibited J Na in during acid exposure in a concentration-dependent manner, with near-complete inhibition at 10 mM. Moreover, J H net loss increased approximately fourfold at 8-10 hours of acid exposure which correlated with recovered J Na in in 1:1 fashion, and both J Na in and J H net were sensitive to tetraethylammonium (TEA) during acid exposure. Zebrafish gills expressed mRNA coding for six NCKX isoforms. CONCLUSIONS During acid exposure, zebrafish engage a novel Na+ uptake mechanism that utilizes the outwardly directed K+ gradient as a counter-substrate for Na+ and is sensitive to TEA. NKCXs are promising candidates to mediate this K+ -dependent Na+ uptake, opening new research avenues about Na+ uptake in zebrafish and other acid-tolerant aquatic species.
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Affiliation(s)
- Alexander M. Clifford
- Department of Zoology University of British Columbia Vancouver British Columbia Canada
- Marine Biology Research Division Scripps Institution of Oceanography University of California San Diego La Jolla California USA
| | - Martin Tresguerres
- Marine Biology Research Division Scripps Institution of Oceanography University of California San Diego La Jolla California USA
| | - Greg G. Goss
- Department of Biological Sciences University of Alberta Edmonton Alberta Canada
| | - Chris M. Wood
- Department of Zoology University of British Columbia Vancouver British Columbia Canada
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14
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Liebe H, Liebe F, Sponder G, Hedtrich S, Stumpff F. Beyond Ca 2+ signalling: the role of TRPV3 in the transport of NH 4. Pflugers Arch 2021; 473:1859-1884. [PMID: 34664138 PMCID: PMC8599221 DOI: 10.1007/s00424-021-02616-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/17/2021] [Accepted: 08/18/2021] [Indexed: 12/11/2022]
Abstract
Mutations of TRPV3 lead to severe dermal hyperkeratosis in Olmsted syndrome, but whether the mutants are trafficked to the cell membrane or not is controversial. Even less is known about TRPV3 function in intestinal epithelia, although research on ruminants and pigs suggests an involvement in the uptake of NH4+. It was the purpose of this study to measure the permeability of the human homologue (hTRPV3) to NH4+, to localize hTRPV3 in human skin equivalents, and to investigate trafficking of the Olmsted mutant G573S. Immunoblotting and immunostaining verified the successful expression of hTRPV3 in HEK-293 cells and Xenopus oocytes with trafficking to the cell membrane. Human skin equivalents showed distinct staining of the apical membrane of the top layer of keratinocytes with cytosolic staining in the middle layers. Experiments with pH-sensitive microelectrodes on Xenopus oocytes demonstrated that acidification by NH4+ was significantly greater when hTRPV3 was expressed. Single-channel measurements showed larger conductances in overexpressing Xenopus oocytes than in controls. In whole-cell experiments on HEK-293 cells, both enantiomers of menthol stimulated influx of NH4+ in hTRPV3 expressing cells, but not in controls. Expression of the mutant G573S greatly reduced cell viability with partial rescue via ruthenium red. Immunofluorescence confirmed cytosolic expression, with membrane staining observed in a very small number of cells. We suggest that expression of TRPV3 by epithelia may have implications not just for Ca2+ signalling, but also for nitrogen metabolism. Models suggesting how influx of NH4+ via TRPV3 might stimulate skin cornification or intestinal NH4+ transport are discussed.
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Affiliation(s)
- Hendrik Liebe
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.,Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Franziska Liebe
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Gerhard Sponder
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Sarah Hedtrich
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | - Friederike Stumpff
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.
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15
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Diener M. How to manage N waste in the intestine? Acta Physiol (Oxf) 2021; 233:e13711. [PMID: 34214253 DOI: 10.1111/apha.13711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Martin Diener
- Institute for Veterinary Physiology and Biochemistry Justus Liebig University Giessen Germany
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16
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Zhang L, López-Picón FR, Jia Y, Chen Y, Li J, Han C, Zhuang X, Xia H. Longitudinal [ 18F]FDG and [ 13N]NH 3 PET/CT imaging of brain and spinal cord in a canine hemisection spinal cord injury model. Neuroimage Clin 2021; 31:102692. [PMID: 33992987 PMCID: PMC8134064 DOI: 10.1016/j.nicl.2021.102692] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 04/21/2021] [Accepted: 05/01/2021] [Indexed: 11/06/2022]
Abstract
To further understand the neurological changes induced by spinal cord injury (SCI) in its acute and subacute stages, we evaluated longitudinal changes in glucose and glutamate metabolism in the spinal cord and brain regions of a canine hemisection SCI model. [18F]FDG and [13N]NH3 positron-emission tomography (PET) with computed tomography (CT) was performed before SCI and at 1, 3, 7, 14, and 21 days after SCI. Spinal cord [18F]FDG uptake increased and peaked at 3 days post SCI. Similar changes were observed in the brain regions but were not statistically significant. Compared to the acute phase of SCI, [13N]NH3 uptake increased in the subacute stage and peaked at 7 days post SCI in all analyzed brain regions. But in spinal cord, no [13N]NH3 uptake was detected before SCI when the blood-spinal cord barrier (BSCB) was intact, then gradually increased when the BSCB was damaged after SCI. [13N]NH3 uptake was significantly correlated with plasma levels of the BSCB disruption marker, monocyte chemoattractant protein-1 (MCP-1). Overall, we showed that SCI induced in vivo changes in glucose uptake in both the spinal cord and the examined brain regions, and changes in glutamine synthetase activity in the latter. Moreover, our results suggest that [13N]NH3 PET may serve as a potential method for assessing BSCB permeability in vivo.
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Affiliation(s)
- Lijian Zhang
- Department of Neurosurgery, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China; Department of Neurosurgery, Affiliated Hospital of Hebei University, Baoding, Hebei, China
| | - Francisco R López-Picón
- Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland; MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Yingqin Jia
- Department of Nuclear Medicine, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China
| | - Yao Chen
- Department of Neurosurgery, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China
| | - Juan Li
- Department of Nuclear Medicine, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China
| | - Chunlei Han
- Clinical Imaging Laboratory, Turku PET Centre, University of Turku and Turku University Hospital, Turku, Finland
| | - Xiaoqing Zhuang
- Department of Nuclear Medicine, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China.
| | - Hechun Xia
- Department of Neurosurgery, General Hospital of Ningxia Medical University, Yinchuan, Ningxia, China.
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17
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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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18
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Sørhus E, Donald CE, da Silva D, Thorsen A, Karlsen Ø, Meier S. Untangling mechanisms of crude oil toxicity: Linking gene expression, morphology and PAHs at two developmental stages in a cold-water fish. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 757:143896. [PMID: 33316527 DOI: 10.1016/j.scitotenv.2020.143896] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/17/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
Early life stages of fish are highly sensitive to crude oil exposure and thus, short term exposures during critical developmental periods could have detrimental consequences for juvenile survival. Here we administered crude oil to Atlantic haddock (Melanogrammus aeglefinus) in short term (3-day) exposures at two developmental time periods: before first heartbeat, from gastrulation to cardiac cone stage (early), and from first heartbeat to one day before hatching (late). A frequent sampling regime enabled us to determine immediate PAH uptake, metabolite formation and gene expression changes. In general, the embryotoxic consequences of an oil exposure were more severe in the early exposure animals. Oil droplets on the eggshell resulted in severe cardiac and craniofacial abnormalities in the highest treatments. Gene expression changes of Cytochrome 1 a, b, c and d (cyp1a, b, c, d), Bone morphogenetic protein 10 (bmp10), ABC transporter b1 (abcb1) and Rh-associated G-protein (rhag) were linked to PAH uptake, occurrence of metabolites of phenanthrene and developmental and functional abnormalities. We detected circulation-independent, oil-induced gene expression changes and separated phenotypes linked to proliferation, growth and disruption of formation events at early and late developmental stages. Changes in bmp10 expression suggest a direct oil-induced effect on calcium homeostasis. Localized expression of rhag propose an impact on osmoregulation. Severe eye abnormalities were linked to possible inappropriate overexpression of cyp1b in the eyes. This study gives an increased knowledge about developmentally dependent effects of crude oil toxicity. Thus, our findings provide more knowledge and detail to new and several existing adverse outcome pathways of crude oil toxicity.
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Affiliation(s)
- Elin Sørhus
- Institute of Marine Research, Bergen, Norway.
| | | | - Denis da Silva
- Northwest Fisheries Science Center (NOAA), 2725 Montlake Blvd. East, Seattle, WA 98112-2097, USA
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19
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Liebe F, Liebe H, Kaessmeyer S, Sponder G, Stumpff F. The TRPV3 channel of the bovine rumen: localization and functional characterization of a protein relevant for ruminal ammonia transport. Pflugers Arch 2020; 472:693-710. [PMID: 32458085 PMCID: PMC7293678 DOI: 10.1007/s00424-020-02393-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/31/2020] [Accepted: 05/06/2020] [Indexed: 12/28/2022]
Abstract
Large quantities of ammonia (NH3 or NH4+) are absorbed from the gut, associated with encephalitis in hepatic disease, poor protein efficiency in livestock, and emissions of nitrogenous climate gasses. Identifying the transport mechanisms appears urgent. Recent functional and mRNA data suggest that absorption of ammonia from the forestomach of cattle may involve TRPV3 channels. The purpose of the present study was to sequence the bovine homologue of TRPV3 (bTRPV3), localize the protein in ruminal tissue, and confirm transport of NH4+. After sequencing, bTRPV3 was overexpressed in HEK-293 cells and Xenopus oocytes. An antibody was selected via epitope screening and used to detect the protein in immunoblots of overexpressing cells and bovine rumen, revealing a signal of the predicted ~ 90 kDa. In rumen only, an additional ~ 60 kDa band appeared, which may represent a previously described bTRPV3 splice variant of equal length. Immunohistochemistry revealed staining from the ruminal stratum basale to stratum granulosum. Measurements with pH-sensitive microelectrodes showed that NH4+ acidifies Xenopus oocytes, with overexpression of bTRPV3 enhancing permeability to NH4+. Single-channel measurements revealed that Xenopus oocytes endogenously expressed small cation channels in addition to fourfold-larger channels only observed after expression of bTRPV3. Both endogenous and bTRPV3 channels conducted NH4+, Na+, and K+. We conclude that bTRPV3 is expressed by the ruminal epithelium on the protein level. In conjunction with data from previous studies, a role in the transport of Na+, Ca2+, and NH4+ emerges. Consequences for calcium homeostasis, ruminal pH, and nitrogen efficiency in cattle are discussed.
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Affiliation(s)
- Franziska Liebe
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Hendrik Liebe
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany
| | - Sabine Kaessmeyer
- Institute of Veterinary Anatomy, Freie Universität Berlin, Koserstraße 20, 14195, Berlin, Germany
| | - Gerhard Sponder
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Friederike Stumpff
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.
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20
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Diener M. New ways for an old cation. Pflugers Arch 2020; 472:669-670. [PMID: 32448954 PMCID: PMC8213586 DOI: 10.1007/s00424-020-02394-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 04/28/2020] [Accepted: 05/06/2020] [Indexed: 11/28/2022]
Affiliation(s)
- Martin Diener
- Institute for Veterinary Physiology and Biochemistry, Justus Liebig University Giessen, Frankfurter Str. 100, 35392, Giessen, Germany.
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21
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Tresguerres M, Clifford AM, Harter TS, Roa JN, Thies AB, Yee DP, Brauner CJ. Evolutionary links between intra- and extracellular acid-base regulation in fish and other aquatic animals. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:449-465. [PMID: 32458594 DOI: 10.1002/jez.2367] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 03/10/2020] [Accepted: 05/06/2020] [Indexed: 12/17/2022]
Abstract
The acid-base relevant molecules carbon dioxide (CO2 ), protons (H+ ), and bicarbonate (HCO3 - ) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid-base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO2 , H+ , and HCO3 - have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways. Life in aquatic environments presents organisms with distinct acid-base challenges that are not found in terrestrial environments. These include a relatively high CO2 relative to O2 solubility that prevents internal CO2 /HCO3 - accumulation to buffer pH, a lower O2 content that may favor anaerobic metabolism, and variable environmental CO2 , pH and O2 levels that require dynamic adjustments in acid-base homeostatic mechanisms. Additionally, some aquatic animals purposely create acidic or alkaline microenvironments that drive specialized physiological functions. For example, acidifying mechanisms can enhance O2 delivery by red blood cells, lead to ammonia trapping for excretion or buoyancy purposes, or lead to CO2 accumulation to promote photosynthesis by endosymbiotic algae. On the other hand, alkalinizing mechanisms can serve to promote calcium carbonate skeletal formation. This nonexhaustive review summarizes some of the distinct acid-base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.
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Affiliation(s)
- Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Alexander M Clifford
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Jinae N Roa
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Angus B Thies
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Daniel P Yee
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, California
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, Canada
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22
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Weiner ID, Verlander JW. Emerging Features of Ammonia Metabolism and Transport in Acid-Base Balance. Semin Nephrol 2020; 39:394-405. [PMID: 31300094 DOI: 10.1016/j.semnephrol.2019.04.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ammonia metabolism has a critical role in acid-base homeostasis and in other cellular functions. Kidneys have a central role in bicarbonate generation, which occurs through the process of net acid excretion; ammonia metabolism is the quantitatively greatest component of net acid excretion, both under basal conditions and in response to acid-base disturbances. Several recent studies have advanced our understanding substantially of the molecular mechanisms and regulation of ammonia metabolism. First, the previous paradigm that ammonia transport could be explained by passive NH3 diffusion and NH4+ trapping has been advanced by the recognition that specific transport of NH3 and of NH4+ by specific membrane proteins is critical to ammonia transport. Second, significant advances have been made in the understanding of the regulation of ammonia metabolism. Novel studies have shown that hyperkalemia directly inhibits ammonia metabolism, thereby leading to the metabolic acidosis present in type IV renal tubular acidosis. Other studies have shown that the proximal tubule protein NBCe1, specifically the A variant NBCe1-A, has a major role in regulating renal ammonia metabolism. Third, there are important sex differences in ammonia metabolism that involve structural and functional differences in the kidney. This review addresses these important aspects of ammonia metabolism and transport.
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Affiliation(s)
- I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL; Nephrology and Hypertension Section, Gainesville Veterans Affairs Medical Center, Gainesville, FL.
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL
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23
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Benitez-Martin C, Guadix JA, Pearson JR, Najera F, Perez-Pomares JM, Perez-Inestrosa E. Indolenine-Based Derivatives as Customizable Two-Photon Fluorescent Probes for pH Bioimaging in Living Cells. ACS Sens 2020; 5:1068-1074. [PMID: 32227860 DOI: 10.1021/acssensors.9b02590] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Novel pH probes based on 2-(6-methoxynaphthalen-2-yl)-3,3-dimethyl-3H-indole have been synthesized and characterized. These compounds display excellent "off-on" fluorescence responses to acidic pH especially under two-photon (TP) excitation conditions as well as strong selectivity and sensitivity toward H+. These features are supported by fluorescence quantum yields over 35%, TP cross sections ∼60 GM, and good resistance to photodegradation under acidic conditions. The synthetic versatility of this model allows subcellular targets to be tuned through minor scaffold modifications without affecting its optical characteristics. The effectiveness of the probes' innate photophysical properties and the structural modifications for different pH-related applications are demonstrated in mouse embryonic fibroblast cells.
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Affiliation(s)
- Carlos Benitez-Martin
- Departamento de Quı́mica Orgánica, Universidad de Málaga-IBIMA, Campus de Teatinos s/n, Málaga 29071, Spain
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
| | - Juan A. Guadix
- Departamento de Biologı́a Animal, Facultad de Ciencias, Universidad de Málaga-IBIMA, Campus de Teatinos s/n, Málaga 29071, Spain
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
| | - John R. Pearson
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
| | - Francisco Najera
- Departamento de Quı́mica Orgánica, Universidad de Málaga-IBIMA, Campus de Teatinos s/n, Málaga 29071, Spain
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
| | - Jose M. Perez-Pomares
- Departamento de Biologı́a Animal, Facultad de Ciencias, Universidad de Málaga-IBIMA, Campus de Teatinos s/n, Málaga 29071, Spain
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
| | - Ezequiel Perez-Inestrosa
- Departamento de Quı́mica Orgánica, Universidad de Málaga-IBIMA, Campus de Teatinos s/n, Málaga 29071, Spain
- Centro Andaluz de Nanomedicina y Biotecnologı́a-BIONAND, Parque Tecnológico de Andalucía, c/Severo Ochoa, 35, 29590 Campanillas, Málaga 29071, Spain
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Abdulnour‐Nakhoul S, Hering‐Smith K, Hamm LL, Nakhoul NL. Effects of chronic hypercapnia on ammonium transport in the mouse kidney. Physiol Rep 2019; 7:e14221. [PMID: 31456326 PMCID: PMC6712239 DOI: 10.14814/phy2.14221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 11/24/2022] Open
Abstract
Hypercapnia and subsequent respiratory acidosis are serious complications in many patients with respiratory disorders. The acute response to hypercapnia is buffering of H+ by hemoglobin and cellular proteins but this effect is limited. The chronic response is renal compensation that increases HCO3- reabsorption, and stimulates urinary excretion of titratable acids (TA) and NH4+ . However, the main effective pathway is the excretion of NH4+ in the collecting duct. Our hypothesis is that, the renal NH3 /NH4+ transporters, Rhbg and Rhcg, in the collecting duct mediate this response. The effect of hypercapnia on these transporters is unknown. We conducted in vivo experiments on mice subjected to chronic hypercapnia. One group breathed 8% CO2 and the other breathed normal air as control (0.04% CO2 ). After 3 days, the mice were euthanized and kidneys, blood, and urine samples were collected. We used immunohistochemistry and Western blot analysis to determine the effects of high CO2 on localization and expression of the Rh proteins, carbonic anhydrase IV, and pendrin. In hypercapnic animals, there was a significant increase in urinary NH4+ excretion but no change in TA. Western blot analysis showed a significant increase in cortical expression of Rhbg (43%) but not of Rhcg. Expression of CA-IV was increased but pendrin was reduced. These data suggest that hypercapnia leads to compensatory upregulation of Rhbg that contributes to excretion of NH3 /NH4+ in the kidney. These studies are the first to show a link among hypercapnia, NH4+ excretion, and Rh expression.
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Affiliation(s)
- Solange Abdulnour‐Nakhoul
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - Kathleen Hering‐Smith
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - L. Lee Hamm
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
| | - Nazih L. Nakhoul
- Section of Nephrology, Departments of Medicine and PhysiologyTulane University School of MedicineNew OrleansLouisiana
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25
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Risinger M, Emberesh M, Kalfa TA. Rare Hereditary Hemolytic Anemias: Diagnostic Approach and Considerations in Management. Hematol Oncol Clin North Am 2019; 33:373-392. [PMID: 31030808 DOI: 10.1016/j.hoc.2019.01.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hereditary hemolytic anemias (HHAs) comprise a heterogeneous group of anemias caused by mutations in genes coding the globins, red blood cell (RBC) membrane proteins, and RBC enzymes. Congenital dyserythropoietic anemias (CDAs) are rare disorders of erythropoiesis characterized by binucleated and multinucleated erythroblasts in bone marrow. CDAs typically present with a hemolytic phenotype, as the produced RBCs have structural defects and decreased survival and should be considered in the differential of HHAs. This article discusses the clinical presentation, laboratory findings, and management considerations for rare HHAs arising from unstable hemoglobins, RBC hydration defects, the less common RBC enzymopathies, and CDAs.
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Affiliation(s)
- Mary Risinger
- College of Nursing, University of Cincinnati, 3110 Vine Street, Cincinnati, OH 45221-0038, USA
| | - Myesa Emberesh
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, MLC 7018, Cincinnati, OH 45229-3039, USA
| | - Theodosia A Kalfa
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, MLC 7015, Cincinnati, OH 45229-3039, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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26
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Wang W, Lu H, Lu X, Wang D, Wang Z, Dai W, Wang J, Liu P. Effect of tumor necrosis factor-α on the expression of the ammonia transporter Rhcg in the brain in mice with acute liver failure. J Neuroinflammation 2018; 15:234. [PMID: 30134917 PMCID: PMC6106833 DOI: 10.1186/s12974-018-1264-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 07/31/2018] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Ammonia and tumor necrosis factor-alpha (TNF-α) play important roles in the mechanisms of hepatic encephalopathy (HE). Rhesus glycoprotein C (Rhcg) is important for ammonia transport especially in the kidney. The aim of the present study was to investigate the role of Rhcg in the brain in acute liver failure (ALF) and the effect of TNF-α on Rhcg expression. METHODS ALF mouse models were generated by treatment with D-galactosamine (D-GalN) and lipopolysaccharide (LPS), or D-GalN and TNF-α. ALF induction was blocked by pretreatment with anti-TNF-α IgG. The levels of serum TNF-α were determined by ELISA. Blood ammonia and brain ammonia concentrations were detected using an ammonia assay kit. The expression and distribution of Rhcg in the brain tissues of ALF mice were examined by western blotting, real-time PCR, immunohistochemical, and immunofluorescence analyses. RESULTS Serum TNF-α levels were increased in the LPS/D-GalN group. Blood and brain ammonia were increased in the LPS/D-GalN- and TNF-α/D-GalN-induced ALF groups. Rhcg mRNA and protein levels were elevated in both ALF groups, consistent with the increase in blood and brain ammonia. Rhcg was mainly expressed in vascular endothelial cells and astrocytes. Pretreatment with anti-TNF-α IgG antibody downregulated Rhcg in brain tissues in the LPS/D-GalN group, prevented the occurrence of ALF, and reduced blood and brain ammonia levels in the LPS/D-GalN group. CONCLUSION TNF-α promoted the transport of ammonia from the blood to brain tissues and exacerbated the toxic effects of ammonia by upregulating Rhcg.
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Affiliation(s)
- Wen Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Hui Lu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Xu Lu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Donglei Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Zhaohan Wang
- Gastroenterology and Hepatology Department, Jiangxi Provincial People's Hospital, Nanchang City, Jiangxi Province, People's Republic of China
| | - Wenying Dai
- Department of Intervention, the Sixth People's Hospital of Shenyang, Shenyang City, Liaoning Province, People's Republic of China
| | - Jinyong Wang
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Pei Liu
- Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, 155 Nanjing North Street, Shenyang, 110001, Liaoning Province, People's Republic of China. .,The Institute of Liver Diseases of China Medical University, Shenyang, Liaoning Province, China.
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27
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Calender A, Rollat Farnier PA, Buisson A, Pinson S, Bentaher A, Lebecque S, Corvol H, Abou Taam R, Houdouin V, Bardel C, Roy P, Devouassoux G, Cottin V, Seve P, Bernaudin JF, Lim CX, Weichhart T, Valeyre D, Pacheco Y, Clement A, Nathan N. Whole exome sequencing in three families segregating a pediatric case of sarcoidosis. BMC Med Genomics 2018; 11:23. [PMID: 29510755 PMCID: PMC5839022 DOI: 10.1186/s12920-018-0338-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Accepted: 02/19/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Sarcoidosis (OMIM 181000) is a multi-systemic granulomatous disorder of unknown origin. Despite multiple genome-wide association (GWAS) studies, no major pathogenic pathways have been identified to date. To find out relevant sarcoidosis predisposing genes, we searched for de novo and recessive mutations in 3 young probands with sarcoidosis and their healthy parents using a whole-exome sequencing (WES) methodology. METHODS From the SARCFAM project based on a national network collecting familial cases of sarcoidosis, we selected three families (trios) in which a child, despite healthy parents, develop the disease before age 15 yr. Each trio was genotyped by WES (Illumina HiSEQ 2500) and we selected the gene variants segregating as 1) new mutations only occurring in affected children and 2) as recessive traits transmitted from each parents. The identified coding variants were compared between the three families. Allelic frequencies and in silico functional results were analyzed using ExAC, SIFT and Polyphenv2 databases. The clinical and genetic studies were registered by the ClinicalTrials.gov - Protocol Registration and Results System (PRS) ( https://clinicaltrials.gov ) receipt under the reference NCT02829853 and has been approved by the ethical committee (CPP LYON SUD EST - 2 - REF IRB 00009118 - September 21, 2016). RESULTS We identified 37 genes sharing coding variants occurring either as recessive mutations in at least 2 trios or de novo mutations in one of the three affected children. The genes were classified according to their potential roles in immunity related pathways: 9 to autophagy and intracellular trafficking, 6 to G-proteins regulation, 4 to T-cell activation, 4 to cell cycle and immune synapse, 2 to innate immunity. Ten of the 37 genes were studied in a bibliographic way to evaluate the functional link with sarcoidosis. CONCLUSIONS Whole exome analysis of case-parent trios is useful for the identification of genes predisposing to complex genetic diseases as sarcoidosis. Our data identified 37 genes that could be putatively linked to a pediatric form of sarcoidosis in three trios. Our in-depth focus on 10 of these 37 genes may suggest that the formation of the characteristic lesion in sarcoidosis, granuloma, results from combined deficits in autophagy and intracellular trafficking (ex: Sec16A, AP5B1 and RREB1), G-proteins regulation (ex: OBSCN, CTTND2 and DNAH11), T-cell activation (ex: IDO2, IGSF3), mitosis and/or immune synapse (ex: SPICE1 and KNL1). The significance of these findings needs to be confirmed by functional tests on selected gene variants.
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Affiliation(s)
- Alain Calender
- Genetics Department, Hospices Civils de LYON (HCL), University Hospital, East Pathology Center, LYON, B-A3, 59 Bld Pinel, 69677 BRON Cedex, France
- Inflammation & Immunity of the Respiratory Epithelium - EA7426 (PI3) – South Medical University Hospital – Lyon 1 Claude Bernard University, 165 Chemin du Grand Revoyet, 69310 Pierre-Bénite, France
| | | | - Adrien Buisson
- Genetics Department, Hospices Civils de LYON (HCL), University Hospital, East Pathology Center, LYON, B-A3, 59 Bld Pinel, 69677 BRON Cedex, France
| | - Stéphane Pinson
- Genetics Department, Hospices Civils de LYON (HCL), University Hospital, East Pathology Center, LYON, B-A3, 59 Bld Pinel, 69677 BRON Cedex, France
| | - Abderrazzaq Bentaher
- Inflammation & Immunity of the Respiratory Epithelium - EA7426 (PI3) – South Medical University Hospital – Lyon 1 Claude Bernard University, 165 Chemin du Grand Revoyet, 69310 Pierre-Bénite, France
| | - Serge Lebecque
- Cancer Research Center, INSERM U-1052, CNRS 5286, 69008 Lyon, France
| | - Harriet Corvol
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Trousseau, AP-HP, INSERM UMR-S938, Sorbonne University, Paris, France
| | - Rola Abou Taam
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Necker, Paris, France
| | - Véronique Houdouin
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Robert Debré, INSERM U-1142, University Paris Diderot VII, Paris, France
| | - Claire Bardel
- Department of biostatistics, University Hospital, Hospices Civils de LYON (HCL), Lyon, France
| | - Pascal Roy
- Department of biostatistics, University Hospital, Hospices Civils de LYON (HCL), Lyon, France
| | - Gilles Devouassoux
- Department of Pulmonology, University Hospital, Hôpital Croix Rousse, Lyon, France
| | - Vincent Cottin
- Department of Pulmonology, University Hospital, Hôpital Louis Pradel, Lyon, France
| | - Pascal Seve
- Department of Internal medicine, University Hospital, Hôpital Croix Rousse, Lyon, France
| | | | - Clarice X. Lim
- Medical University of Vienna, Center for Pathobiochemistry and Genetics, Institute of Medical Genetics, Währinger Straße 10, 1090 Vienna, Austria
| | - Thomas Weichhart
- Medical University of Vienna, Center for Pathobiochemistry and Genetics, Institute of Medical Genetics, Währinger Straße 10, 1090 Vienna, Austria
| | - Dominique Valeyre
- EA2363, University Paris 13, COMUE Sorbonne-Paris-Cité, 74 rue Marcel Cachin, 93009 Bobigny, France
- Assistance Publique Hôpitaux de Paris, Department of Pulmonology, Avicenne University Hospital, 93009 Bobigny, France
| | - Yves Pacheco
- Inflammation & Immunity of the Respiratory Epithelium - EA7426 (PI3) – South Medical University Hospital – Lyon 1 Claude Bernard University, 165 Chemin du Grand Revoyet, 69310 Pierre-Bénite, France
| | - Annick Clement
- AP-HP Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Trousseau, INSERM UMR-S933, Sorbonne University, Paris, France
| | - Nadia Nathan
- AP-HP Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Trousseau, INSERM UMR-S933, Sorbonne University, Paris, France
| | - in the frame of GSF (Groupe Sarcoïdose France)
- Genetics Department, Hospices Civils de LYON (HCL), University Hospital, East Pathology Center, LYON, B-A3, 59 Bld Pinel, 69677 BRON Cedex, France
- Department of biostatistics, University Hospital, Hospices Civils de LYON (HCL), Lyon, France
- Inflammation & Immunity of the Respiratory Epithelium - EA7426 (PI3) – South Medical University Hospital – Lyon 1 Claude Bernard University, 165 Chemin du Grand Revoyet, 69310 Pierre-Bénite, France
- Cancer Research Center, INSERM U-1052, CNRS 5286, 69008 Lyon, France
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Trousseau, AP-HP, INSERM UMR-S938, Sorbonne University, Paris, France
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Necker, Paris, France
- Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Robert Debré, INSERM U-1142, University Paris Diderot VII, Paris, France
- Department of Pulmonology, University Hospital, Hôpital Croix Rousse, Lyon, France
- Department of Pulmonology, University Hospital, Hôpital Louis Pradel, Lyon, France
- Department of Internal medicine, University Hospital, Hôpital Croix Rousse, Lyon, France
- Histology and Tumor Biology, ER2 UPMC, Hôpital Tenon, Paris, France
- Medical University of Vienna, Center for Pathobiochemistry and Genetics, Institute of Medical Genetics, Währinger Straße 10, 1090 Vienna, Austria
- EA2363, University Paris 13, COMUE Sorbonne-Paris-Cité, 74 rue Marcel Cachin, 93009 Bobigny, France
- Assistance Publique Hôpitaux de Paris, Department of Pulmonology, Avicenne University Hospital, 93009 Bobigny, France
- AP-HP Pediatric pulmonology and Reference Center for rare lung diseases RespiRare, Hôpital Trousseau, INSERM UMR-S933, Sorbonne University, Paris, France
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28
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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.
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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
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29
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Abstract
The erythrocyte contains a network of pathways that regulate salt and water content in the face of extracellular and intracellular osmotic perturbations. This allows the erythrocyte to maintain a narrow range of cell hemoglobin concentration, a process critical for normal red blood cell function and survival. Primary disorders that perturb volume homeostasis jeopardize the erythrocyte and may lead to its premature destruction. These disorders are marked by clinical, laboratory, and physiologic heterogeneity. Recent studies have revealed that these disorders are also marked by genetic heterogeneity. They have implicated roles for several proteins, PIEZO1, a mammalian mechanosensory protein; GLUT1, the glucose transporter; SLC4A1, the anion transporter; RhAG, the Rh-associated glycoprotein; KCNN4, the Gardos channel; and ABCB6, an adenosine triphosphate-binding cassette family member, in the maintenance of erythrocyte volume homeostasis. Secondary disorders of erythrocyte hydration include sickle cell disease, thalassemia, hemoglobin CC, and hereditary spherocytosis, where cellular dehydration may be a significant contributor to disease pathology and clinical complications. Understanding the pathways regulating erythrocyte water and solute content may reveal innovative strategies to maintain normal volume in disorders associated with primary or secondary cellular dehydration. These mechanisms will serve as a paradigm for other cells and may reveal new therapeutic targets for disease prevention and treatment beyond the erythrocyte.
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30
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Gilmour KM. Heads you gain, tails you lose. Am J Physiol Regul Integr Comp Physiol 2017; 313:R65-R66. [DOI: 10.1152/ajpregu.00208.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 06/03/2017] [Indexed: 11/22/2022]
Affiliation(s)
- K. M. Gilmour
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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31
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Chen XL, Zhang B, Chng YR, Ong JLY, Chew SF, Wong WP, Lam SH, Nakada T, Ip YK. Ammonia exposure affects the mRNA and protein expression levels of certain Rhesus glycoproteins in the gills of climbing perch. ACTA ACUST UNITED AC 2017; 220:2916-2931. [PMID: 28576822 DOI: 10.1242/jeb.157123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/30/2017] [Indexed: 01/08/2023]
Abstract
The freshwater climbing perch, Anabas testudineus, is an obligate air-breathing and euryhaline teleost capable of active ammonia excretion and tolerant of high concentrations of environmental ammonia. As Rhesus glycoproteins (RhGP/Rhgp) are known to transport ammonia, this study aimed to obtain the complete cDNA coding sequences of various rhgp isoforms from the gills of A. testudineus, and to determine their mRNA and protein expression levels during 6 days of exposure to 100 mmol l-1 NH4Cl. The subcellular localization of Rhgp isoforms in the branchial epithelium was also examined in order to elucidate the type of ionocyte involved in active ammonia excretion. Four rhgp (rhag, rhbg, rhcg1 and rhcg2) had been identified from the gills of A. testudineus They had conserved amino acid residues for NH4+ binding, NH4+ deprotonation, channel gating and lining of the vestibules. Despite inwardly directed NH3 and NH4+ gradients, there were significant increases in the mRNA expression levels of the four branchial rhgp in A. testudineus at certain time points during 6 days of ammonia exposure, with significant increases in the protein abundances of Rhag and Rhcg2 on day 6. Immunofluorescence microscopy revealed a type of ammonia-inducible Na+/K+-ATPase α1c-immunoreactive ionocyte with apical Rhag and basolateral Rhcg2 in the gills of fish exposed to ammonia for 6 days. Hence, active ammonia excretion may involve NH4+ entering the ionocyte through the basolateral Rhcg2 and being excreted through the apical Rhag, driven by a transapical membrane electrical potential generated by the apical cystic fibrosis transmembrane conductance regulator Cl- channel, as suggested previously.
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Affiliation(s)
- Xiu L Chen
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Biyan Zhang
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - You R Chng
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Jasmine L Y Ong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Republic of Singapore
| | - Wai P Wong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Siew H Lam
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore.,NUS Environmental Research Institute, National University of Singapore, Kent Ridge, Singapore 117411, Republic of Singapore
| | - Tsutomu Nakada
- Department of Molecular Pharmacology, Shinshu University School of Medicine, Matsumoto, Nagano 390-8621, Japan
| | - Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
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32
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Clifford AM, Weinrauch AM, Edwards SL, Wilkie MP, Goss GG. Flexible ammonia handling strategies using both cutaneous and branchial epithelia in the highly ammonia-tolerant Pacific hagfish. Am J Physiol Regul Integr Comp Physiol 2017; 313:R78-R90. [PMID: 28515081 DOI: 10.1152/ajpregu.00351.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 12/20/2022]
Abstract
Hagfish consume carrion, potentially exposing them to hypoxia, hypercapnia, and high environmental ammonia (HEA). We investigated branchial and cutaneous ammonia handling strategies by which Pacific hagfish (Eptatretus stoutii) tolerate and recover from high ammonia loading. Hagfish were exposed to HEA (20 mmol/l) for 48 h to elevate plasma total ammonia (TAmm) levels before placement into divided chambers for a 4-h recovery period in ammonia-free seawater where ammonia excretion (JAmm) was measured independently in the anterior and posterior compartments. Localized HEA exposures were also conducted by subjecting hagfish to HEA in either the anterior or posterior compartments. During recovery, HEA-exposed animals increased JAmm in both compartments, with the posterior compartment comprising ~20% of the total JAmm compared with ~11% in non-HEA-exposed fish. Plasma TAmm increased substantially when whole hagfish and the posterior regions were exposed to HEA. Alternatively, plasma TAmm did not elevate after anterior localized HEA exposure. JAmm was concentration dependent (0.05-5 mmol/l) across excised skin patches at up to eightfold greater rates than in skin sections that were excised from HEA-exposed hagfish. Skin excised from more posterior regions displayed greater JAmm than those from more anterior regions. Immunohistochemistry with hagfish-specific anti-rhesus glycoprotein type c (α-hRhcg; ammonia transporter) antibody was characterized by staining on the basal aspect of hagfish epidermis while Western blotting demonstrated greater expression of Rhcg in more posterior skin sections. We conclude that cutaneous Rhcg proteins are involved in cutaneous ammonia excretion by Pacific hagfish and that this mechanism could be particularly important during feeding.
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Affiliation(s)
- Alexander M Clifford
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; .,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
| | - Alyssa M Weinrauch
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
| | - Susan L Edwards
- Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada.,Department of Biology, Appalachian State University, Boone, North Carolina; and
| | - Michael P Wilkie
- Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada.,Department of Biology and Laurier Institute for Water Science, Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
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33
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Moreira NR, Cardoso C, Dias RO, Ferreira C, Terra WR. A physiologically-oriented transcriptomic analysis of the midgut of Tenebrio molitor. JOURNAL OF INSECT PHYSIOLOGY 2017; 99:58-66. [PMID: 28341416 DOI: 10.1016/j.jinsphys.2017.03.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 03/13/2017] [Accepted: 03/20/2017] [Indexed: 06/06/2023]
Abstract
Physiological data showed that T. molitor midgut is buffered at pH 5.6 at the two anterior thirds and at 7.9 at the posterior third. Furthermore, water is absorbed and secreted at the anterior and posterior midgut, respectively, driving a midgut counter flux of fluid. To look for the molecular mechanisms underlying these phenomena and nutrient absorption as well, a transcriptomic approach was used. For this, 11 types of transporters were chosen from the midgut transcriptome obtained by pyrosequencing (Roche 454). After annotation with the aid of databanks and manual curation, the sequences were validated by RT-PCR. The expression level of each gene at anterior, middle and posterior midgut and carcass (larva less midgut) was evaluated by RNA-seq taking into account reference sequences based on 454 contigs and reads obtained by Illumina sequencing. The data showed that sugar and amino acid uniporters and symporters are expressed along the whole midgut. In the anterior midgut are found transporters for NH3 and NH4+ that with a chloride channel may be responsible for acidifying the lumen. At the posterior midgut, bicarbonate-Cl- antiporter with bicarbonate supplied by carbonic anhydrase may alkalinize the lumen. Water absorption caused mainly by an anterior Na+-K+-2Cl- symporter and water secretion caused by a posterior K+-Cl- may drive the midgut counter flux. Transporters that complement the action of those described were also found.
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Affiliation(s)
- Nathalia R Moreira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Christiane Cardoso
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Renata O Dias
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Clelia Ferreira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil
| | - Walter R Terra
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000 São Paulo, Brazil.
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Abstract
Acid-base homeostasis is critical to maintenance of normal health. Renal ammonia excretion is the quantitatively predominant component of renal net acid excretion, both under basal conditions and in response to acid-base disturbances. Although titratable acid excretion also contributes to renal net acid excretion, the quantitative contribution of titratable acid excretion is less than that of ammonia under basal conditions and is only a minor component of the adaptive response to acid-base disturbances. In contrast to other urinary solutes, ammonia is produced in the kidney and then is selectively transported either into the urine or the renal vein. The proportion of ammonia that the kidney produces that is excreted in the urine varies dramatically in response to physiological stimuli, and only urinary ammonia excretion contributes to acid-base homeostasis. As a result, selective and regulated renal ammonia transport by renal epithelial cells is central to acid-base homeostasis. Both molecular forms of ammonia, NH3 and NH4+, are transported by specific proteins, and regulation of these transport processes determines the eventual fate of the ammonia produced. In this review, we discuss these issues, and then discuss in detail the specific proteins involved in renal epithelial cell ammonia transport.
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Affiliation(s)
- I David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
| | - Jill W Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, Florida; and Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, Florida
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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.
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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
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Thiel D, Hugenschütt M, Meyer H, Paululat A, Quijada-Rodriguez AR, Purschke G, Weihrauch D. Ammonia excretion in the marine polychaete Eurythoe complanata (Annelida). ACTA ACUST UNITED AC 2016; 220:425-436. [PMID: 27852754 DOI: 10.1242/jeb.145615] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 11/11/2016] [Indexed: 12/31/2022]
Abstract
Ammonia is a toxic waste product from protein metabolism and needs to be either converted into less toxic molecules or, in the case of fish and aquatic invertebrates, excreted directly as is. In contrast to fish, very little is known regarding the ammonia excretion mechanism and the participating excretory organs in marine invertebrates. In the current study, ammonia excretion in the marine burrowing polychaete Eurythoe complanata was investigated. As a potential site for excretion, the 100-200 µm long, 30-50 µm wide and up to 25 µm thick dentrically branched, well ventilated and vascularized branchiae (gills) were identified. In comparison to the main body, the branchiae showed considerably higher mRNA expression levels of Na+/K+-ATPase, V-type H+-ATPase, cytoplasmic carbonic anhydrase (CA-2), a Rhesus-like protein, and three different ammonia transporters (AMTs). Experiments on the intact organism revealed that ammonia excretion did not occur via apical ammonia trapping, but was regulated by a basolateral localized V-type H+-ATPase, carbonic anhydrase and intracellular cAMP levels. Interestingly, the V-type H+-ATPase seems to play a role in ammonia retention. A 1 week exposure to 1 mmol l-1 NH4Cl (HEA) did not cause a change in ammonia excretion rates, while the three branchial expressed AMTs showed a tendency to be down-regulated. This indicates a shift of function in the branchial ammonia excretion processes under these conditions.
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Affiliation(s)
- Daniel Thiel
- University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany
| | - Maja Hugenschütt
- University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany
| | - Heiko Meyer
- University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany
| | - Achim Paululat
- University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany
| | | | - Günter Purschke
- University of Osnabrück, Fachbereich Biologie, Department of Zoology, Osnabrück 49069, Germany
| | - Dirk Weihrauch
- University of Manitoba, Department of Biological Sciences, Winnipeg, Manitoba, Canada
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Wood CM, Giacomin M. Feeding through your gills and turning a toxicant into a resource: how the dogfish shark scavenges ammonia from its environment. J Exp Biol 2016; 219:3218-3226. [DOI: 10.1242/jeb.145268] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 08/02/2016] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Nitrogen (N) appears to be a limiting dietary resource for elasmobranchs, required not only for protein growth but also for urea-based osmoregulation. Building on recent evidence that the toxicant ammonia can be taken up actively at the gills of the shark and made into the valuable osmolyte urea, we demonstrate that the uptake exhibits classic Michaelis–Menten saturation kinetics with an affinity constant (Km) of 379 µmol l−1, resulting in net N retention at environmentally realistic ammonia concentrations (100–400 µmol l−1) and net N loss through stimulated urea-N excretion at higher levels. Ammonia-N uptake rate increased or decreased with alterations in seawater pH, but the changes were much less than predicted by the associated changes in seawater PNH3, and more closely paralleled changes in seawater NH4+ concentration. Ammonia-N uptake rate was insensitive to amiloride (0.1 mmol l−1) or to a 10-fold elevation in seawater K+ concentration (to 100 mmol l−1), suggesting that the mechanism does not directly involve Na+ or K+ transporters, but was inhibited by blockade of glutamine synthetase, the enzyme that traps ammonia-N to fuel the ornithine–urea cycle. High seawater ammonia inhibited uptake of the ammonia analogue [14C]methylamine. The results suggest that branchial ammonia-N uptake may significantly supplement dietary N intake, amounting to about 31% of the nitrogen acquired from the diet. They further indicate the involvement of Rh glycoproteins (ammonia channels), which are expressed in dogfish gills, in normal ammonia-N uptake and retention.
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Affiliation(s)
- Chris M. Wood
- Bamfield Marine Sciences Centre, Bamfield, BC, Canada V0R 1B0
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
- Department of Biology, McMaster University, Hamilton, ON, Canada L8S 4K1
| | - Marina Giacomin
- Bamfield Marine Sciences Centre, Bamfield, BC, Canada V0R 1B0
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Weiner ID, Verlander JW. Recent advances in understanding renal ammonia metabolism and transport. Curr Opin Nephrol Hypertens 2016; 25:436-43. [PMID: 27367914 PMCID: PMC4974126 DOI: 10.1097/mnh.0000000000000255] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
PURPOSE OF REVIEW The purpose of this review is to provide a succinct description of the recent findings that advance our understanding of the fundamental renal process of ammonia metabolism and transport in conditions relevant to the clinician. RECENT FINDINGS Recent studies advance our understanding of renal ammonia metabolism. Mechanisms through which chronic kidney disease and altered dietary protein intake alter ammonia excretion have been identified. Lithium, although it can acutely cause distal renal tubular acidosis, was shown with long-term use to increase urinary ammonia excretion, and this appeared to be mediated, at least in part, by increased Rhcg expression. Gene deletion studies showed that the ammonia recycling enzyme, glutamine synthetase, has a critical role in normal-stimulated and acidosis-stimulated ammonia metabolism and that the proximal tubule basolateral bicarbonate transporter, NBCe1, is necessary for normal ammonia metabolism. Finally, our understanding of the molecular ammonia species, NH3 versus NH4, transported by Rh glycoproteins continues to be advanced. SUMMARY Fundamental studies have been recently published that advance our understanding of the regulation of ammonia metabolism in clinically important circumstances, and our understanding of the mechanisms and regulation of proximal tubule ammonia generation, and the mechanisms through which Rh glycoproteins contribute to ammonia secretion.
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Affiliation(s)
- I. David Weiner
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL 32610
- Nephrology and Hypertension Section, North Florida/South Georgia Veterans Health System, Gainesville, FL 32611
| | - Jill W. Verlander
- Division of Nephrology, Hypertension and Renal Transplantation, University of Florida College of Medicine, Gainesville, FL 32610
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Assentoft M, Kaptan S, Schneider HP, Deitmer JW, de Groot BL, MacAulay N. Aquaporin 4 as a NH3 Channel. J Biol Chem 2016; 291:19184-95. [PMID: 27435677 DOI: 10.1074/jbc.m116.740217] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Indexed: 12/21/2022] Open
Abstract
Ammonia is a biologically potent molecule, and the regulation of ammonia levels in the mammalian body is, therefore, strictly controlled. The molecular paths of ammonia permeation across plasma membranes remain ill-defined, but the structural similarity of water and NH3 has pointed to the aquaporins as putative NH3-permeable pores. Accordingly, a range of aquaporins from mammals, plants, fungi, and protozoans demonstrates ammonia permeability. Aquaporin 4 (AQP4) is highly expressed at perivascular glia end-feet in the mammalian brain and may, with this prominent localization at the blood-brain-interface, participate in the exchange of ammonia, which is required to sustain the glutamate-glutamine cycle. Here we observe that AQP4-expressing Xenopus oocytes display a reflection coefficient <1 for NH4Cl at pH 8.0, at which pH an increased amount of the ammonia occurs in the form of NH3 Taken together with an NH4Cl-mediated intracellular alkalization (or lesser acidification) of AQP4-expressing oocytes, these data suggest that NH3 is able to permeate the pore of AQP4. Exposure to NH4Cl increased the membrane currents to a similar extent in uninjected oocytes and in oocytes expressing AQP4, indicating that the ionic NH4 (+) did not permeate AQP4. Molecular dynamics simulations revealed partial pore permeation events of NH3 but not of NH4 (+) and a reduced energy barrier for NH3 permeation through AQP4 compared with that of a cholesterol-containing lipid bilayer, suggesting AQP4 as a favored transmembrane route for NH3 Our data propose that AQP4 belongs to the growing list of NH3-permeable water channels.
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Affiliation(s)
- Mette Assentoft
- From the Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Shreyas Kaptan
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Gottingen, Germany, and
| | - Hans-Peter Schneider
- Division of General Zoology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Joachim W Deitmer
- Division of General Zoology, Department of Biology, University of Kaiserslautern, 67653 Kaiserslautern, Germany
| | - Bert L de Groot
- Computational Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Gottingen, Germany, and
| | - Nanna MacAulay
- From the Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark,
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Zimmer AM, Wilson JM, Wright PA, Hiroi J, Wood CM. Different mechanisms of Na+ uptake and ammonia excretion by the gill and yolk sac epithelium of early life stage rainbow trout. J Exp Biol 2016; 220:775-786. [DOI: 10.1242/jeb.148429] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 12/07/2016] [Indexed: 12/30/2022]
Abstract
In rainbow trout, the dominant site of Na+ uptake (JNain) and ammonia excretion (Jamm) shifts from the skin to the gills over development. Post-hatch (PH; 7 days post-hatch) larvae utilize the yolk sac skin for physiological exchange, whereas by complete yolk sac absorption (CYA; 30 days post-hatch), the gill is the dominant site. At the gills, JNain and Jamm occur via loose Na+/NH4+ exchange, but this exchange has not been examined in the skin of larval trout. Based on previous work, we hypothesized that, contrary to the gill model, JNain by the yolk sac skin of PH trout occurs independently of Jamm. Following a 12-h exposure to high environmental ammonia (HEA; 0.5 mmol l−1 NH4HCO3; [Na+]=600 µmol l−1; pH=8), Jamm by the gills of CYA trout and the yolk sac skin of PH larvae, which were isolated using divided chambers, increased significantly. However, this was coupled to an increase in JNain across the gills only, supporting our hypothesis. Moreover, gene expression of proteins involved in JNain (Na+/H+-exchanger-2 (NHE2) and H+-ATPase) increased in response to HEA only in the CYA gills. We further identified expression of the apical Rhesus (Rh) proteins Rhcg2 in putative pavement cells and Rhcg1 (co-localized with apical NHE2 and NHE3b and Na+/K+-ATPase) in putative peanut lectin agglutinin-positive (PNA+) ionocytes in gill sections. Similar Na+/K+-ATPase-positive cells expressing Rhcg1 and NHE3b, but not NHE2, were identified in the yolk sac epithelium. Overall, our findings suggest that the mechanisms of JNain and Jamm by the dominant exchange epithelium at two distinct stages of early development are fundamentally different.
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Affiliation(s)
- Alex M. Zimmer
- Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N57
- Department of Biology, Wilfrid Laurier University, ON, Canada N2L 3C5
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | | | - Patricia A. Wright
- Department of Anatomy, St Marianna University School of Medicine, Miyamae, Kawasaki 216-8511, Japan
| | - Junya Hiroi
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Chris M. Wood
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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