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Datta S, Antonio BM, Zahler NH, Theile JW, Krafte D, Zhang H, Rosenberg PB, Chaves AB, Muoio DM, Zhang G, Silas D, Li G, Soldano K, Nystrom S, Ferreira D, Miller SE, Bain JR, Muehlbauer MJ, Ilkayeva O, Becker TC, Hohmeier HE, Newgard CB, Olabisi OA. APOL1-mediated monovalent cation transport contributes to APOL1-mediated podocytopathy in kidney disease. J Clin Invest 2024; 134:e172262. [PMID: 38227370 PMCID: PMC10904047 DOI: 10.1172/jci172262] [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: 05/15/2023] [Accepted: 01/09/2024] [Indexed: 01/17/2024] Open
Abstract
Two coding variants of apolipoprotein L1 (APOL1), called G1 and G2, explain much of the excess risk of kidney disease in African Americans. While various cytotoxic phenotypes have been reported in experimental models, the proximal mechanism by which G1 and G2 cause kidney disease is poorly understood. Here, we leveraged 3 experimental models and a recently reported small molecule blocker of APOL1 protein, VX-147, to identify the upstream mechanism of G1-induced cytotoxicity. In HEK293 cells, we demonstrated that G1-mediated Na+ import/K+ efflux triggered activation of GPCR/IP3-mediated calcium release from the ER, impaired mitochondrial ATP production, and impaired translation, which were all reversed by VX-147. In human urine-derived podocyte-like epithelial cells (HUPECs), we demonstrated that G1 caused cytotoxicity that was again reversible by VX-147. Finally, in podocytes isolated from APOL1 G1 transgenic mice, we showed that IFN-γ-mediated induction of G1 caused K+ efflux, activation of GPCR/IP3 signaling, and inhibition of translation, podocyte injury, and proteinuria, all reversed by VX-147. Together, these results establish APOL1-mediated Na+/K+ transport as the proximal driver of APOL1-mediated kidney disease.
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Affiliation(s)
- Somenath Datta
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | | | | | | | | | - Hengtao Zhang
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Cardiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Paul B. Rosenberg
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Cardiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Alec B. Chaves
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
| | - Deborah M. Muoio
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Guofang Zhang
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Daniel Silas
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Guojie Li
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Karen Soldano
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Sarah Nystrom
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Davis Ferreira
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Sara E. Miller
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - James R. Bain
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Michael J. Muehlbauer
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
| | - Olga Ilkayeva
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Thomas C. Becker
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Hans-Ewald Hohmeier
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Christopher B. Newgard
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Opeyemi A. Olabisi
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
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Albuquerque ALB, Dos Santos Borges R, Conegundes AF, Dos Santos EE, Fu FMM, Araujo CT, Vaz de Castro PAS, Simões E Silva AC. Inherited Fanconi syndrome. World J Pediatr 2023; 19:619-634. [PMID: 36729281 DOI: 10.1007/s12519-023-00685-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 01/08/2023] [Indexed: 02/03/2023]
Abstract
BACKGROUND Fanconi-Debré-de Toni syndrome (also known as Fanconi renotubular syndrome, or FRST) profoundly increased the understanding of the functions of the proximal convoluted tubule (PCT) and provided important insights into the pathophysiology of several kidney diseases and drug toxicities. DATA SOURCES We searched Pubmed and Scopus databases to find relevant articles about FRST. This review article focuses on the physiology of the PCT, as well as on the physiopathology of FRST in children, its diagnosis, and treatment. RESULTS FRST encompasses a wide variety of inherited and acquired PCT alterations that lead to impairment of PCT reabsorption. In children, FRST often presents as a secondary feature of systemic disorders that impair energy supply, such as Lowe's syndrome, Dent's disease, cystinosis, hereditary fructose intolerance, galactosemia, tyrosinemia, Alport syndrome, and Wilson's disease. Although rare, congenital causes of FRST greatly impact the morbidity and mortality of patients and impose diagnostic challenges. Furthermore, its treatment is diverse and considers the ability of the clinician to identify the correct etiology of the disease. CONCLUSION The early diagnosis and treatment of pediatric patients with FRST improve the prognosis and the quality of life.
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Affiliation(s)
- Anna Luiza Braga Albuquerque
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Rafael Dos Santos Borges
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Ana Flávia Conegundes
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Erika Emmylaine Dos Santos
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Frederico Moreira Man Fu
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Clara Tavares Araujo
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Pedro Alves Soares Vaz de Castro
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
| | - Ana Cristina Simões E Silva
- Interdisciplinary Laboratory of Medical Investigation, Unit of Pediatric Nephrology, Faculty of Medicine, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil.
- Department of Pediatrics, Faculty of Medicine, UFMG, Alfredo Balena Avenue, 190, 2Nd Floor, Room # 281, Belo Horizonte, MG, 30130-100, Brazil.
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3
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Jufar AH, Evans RG, May CN, Hood SG, Betrie AH, Trask‐Marino A, Bellomo R, Lankadeva YR. The effects of recruitment of renal functional reserve on renal cortical and medullary oxygenation in non-anesthetized sheep. Acta Physiol (Oxf) 2023; 237:e13919. [PMID: 36598336 PMCID: PMC10909474 DOI: 10.1111/apha.13919] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/18/2022] [Accepted: 01/02/2023] [Indexed: 01/05/2023]
Abstract
AIM Recruitment of renal functional reserve (RFR) with amino acid loading increases renal blood flow and glomerular filtration rate. However, its effects on renal cortical and medullary oxygenation have not been determined. Accordingly, we tested the effects of recruitment of RFR on renal cortical and medullary oxygenation in non-anesthetized sheep. METHODS Under general anesthesia, we instrumented 10 sheep to enable subsequent continuous measurements of systemic and renal hemodynamics, renal oxygen delivery and consumption, and cortical and medullary tissue oxygen tension (PO2 ). We then measured the effects of recruitment of RFR with an intravenous infusion of 500 ml of a clinically used amino acid solution (10% Synthamin® 17) in the non-anesthetized state. RESULTS Compared with baseline, Synthamin® 17 infusion significantly increased renal oxygen delivery mean ± SD maximum increase: (from 0.79 ± 0.17 to 1.06 ± 0.16 ml/kg/min, p < 0.001), renal oxygen consumption (from 0.08 ± 0.01 to 0.15 ± 0.02 ml/kg/min, p < 0.001), and glomerular filtration rate (+45.2 ± 2.7%, p < 0.001). Renal cortical tissue PO2 increased by a maximum of 26.4 ± 1.1% (p = 0.001) and medullary tissue PO2 increased by a maximum of 23.9 ± 2.8% (p = 0. 001). CONCLUSIONS In non-anesthetized healthy sheep, recruitment of RFR improved renal cortical and medullary oxygenation. These observations might have implications for the use of recruitment of RFR for diagnostic and therapeutic purposes.
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Affiliation(s)
- Alemayehu H. Jufar
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Cardiovascular Disease Program, Department of PhysiologyBiomedicine Discovery Institute, Monash UniversityMelbourneVictoriaAustralia
| | - Roger G. Evans
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Cardiovascular Disease Program, Department of PhysiologyBiomedicine Discovery Institute, Monash UniversityMelbourneVictoriaAustralia
| | - Clive N. May
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
| | - Sally G. Hood
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
| | - Ashenafi H. Betrie
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Melbourne Dementia Research CentreFlorey Institute of Neuroscience and Mental Health, The University of MelbourneMelbourneVictoriaAustralia
| | - Anton Trask‐Marino
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
| | - Rinaldo Bellomo
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
| | - Yugeesh R. Lankadeva
- Pre‐Clinical Critical Care UnitFlorey Institute of Neuroscience and Mental Health, University of MelbourneMelbourneVictoriaAustralia
- Department of Critical CareMelbourne Medical School, University of MelbourneMelbourneVictoriaAustralia
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Abstract
![]()
Metabolomics is becoming a mature
part of analytical chemistry
as evidenced by the growing number of publications and attendees of
international conferences dedicated to this topic. Yet, a systematic
treatment of the fundamental structure and properties of metabolomics
data is lagging behind. We want to fill this gap by introducing two
fundamental theories concerning metabolomics data: data theory and
measurement theory. Our approach is to ask simple questions, the answers
of which require applying these theories to metabolomics. We show
that we can distinguish at least four different levels of metabolomics
data with different properties and warn against confusing data with
numbers. This treatment provides a theoretical underpinning for preprocessing
and postprocessing methods in metabolomics and also argues for a proper
match between type of metabolomics data and the biological question
to be answered. The approach can be extended to other omics measurements
such as proteomics and is thus of relevance for a large analytical
chemistry community.
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Affiliation(s)
- Age K Smilde
- Biosystems Data Analysis, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Thomas Hankemeier
- Analytical Biosciences, LACDR, Leiden University, 2333 CC Leiden, The Netherlands
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5
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Baliou S, Kyriakopoulos AM, Goulielmaki M, Panayiotidis MI, Spandidos DA, Zoumpourlis V. Significance of taurine transporter (TauT) in homeostasis and its layers of regulation (Review). Mol Med Rep 2020; 22:2163-2173. [PMID: 32705197 PMCID: PMC7411481 DOI: 10.3892/mmr.2020.11321] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/09/2020] [Indexed: 11/05/2022] Open
Abstract
Taurine (2‑aminoethanesulfonic acid) contributes to homeostasis, mainly through its antioxidant and osmoregulatory properties. Taurine's influx and efflux are mainly mediated through the ubiquitous expression of the sodium/chloride‑dependent taurine transporter, located on the plasma membrane. The significance of the taurine transporter has been shown in various organ malfunctions in taurine‑transporter‑null mice. The taurine transporter differentially responds to various cellular stimuli including ionic environment, electrochemical charge, and pH changes. The renal system has been used as a model to evaluate the factors that significantly determine the regulation of taurine transporter regulation.
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Affiliation(s)
- Stella Baliou
- National Hellenic Research Foundation, 11635 Athens, Greece
| | | | | | - Michalis I Panayiotidis
- Department of Electron Microscopy and Molecular Pathology, The Cyprus Institute of Neurology and Genetics, 2371 Nicosia, Cyprus
| | - Demetrios A Spandidos
- Laboratory of Clinical Virology, Medical School, University of Crete, 71003 Heraklion, Greece
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6
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Nesovic-Ostojic J, Kovacevic S, Spasic S, Lopicic S, Todorovic J, Dincic M, Stanojevic M, Savin M, Milovanovic A, Cemerikic D. Modulation of luminal L-alanine transport in proximal tubular cells of frog kidney induced by low micromolar Cd 2+ concentration. Comp Biochem Physiol C Toxicol Pharmacol 2019; 216:38-42. [PMID: 30414954 DOI: 10.1016/j.cbpc.2018.11.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 11/07/2018] [Accepted: 11/08/2018] [Indexed: 12/25/2022]
Abstract
The kidneys are recognized as a major target of cadmium-induced toxicity. However, all mechanisms that are involved in the early stages of cadmium nephrotoxicity, particularly considering low micromolar concentrations of cadmium ions (Cd2+) are still unknown. Therefore, the aim of this study was to investigate the effects of peritubular acute exposure to micromolar Cd2+ concentration (2.3 μmol/L) on the rapid depolarization and the rate of slow repolarization of peritubular membrane potential difference (PD), induced by luminal application of L-alanine in proximal tubular cells of frog kidney. The results showed that the luminal application of L-alanine rapidly depolarized the peritubular membrane PD of -42.00 ± 11.68 mV by 23.89 ± 4.15 mV with an average rate of slow repolarization of 5.64 ± 0.81 mV/min. Additionally, peritubular acute exposure to Cd2+ induced change in rapid depolarization of peritubular membrane PD of -53.33 ± 13.01 mV by 18.78 ± 3.31 mV (P < 0.01) after luminal application of L-alanine. Also, peritubular acute exposure to Cd2+ led to statistically significant decrease in the rate of slow repolarization of peritubular membrane PD (3.53 ± 0.35 mV/min; P < 0.05). In conclusion, these results suggest that peritubular acute exposure to low micromolar Cd2+ concentration decreased the rapid depolarization and the rate of slow repolarization of peritubular membrane PD induced by luminal application of L-alanine. This is followed by reduced luminal sodium-coupled transport of L-alanine and this change may be one of the possible mechanisms involved in the early stages of Cd2+-induced nephrotoxicity.
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Affiliation(s)
| | - Sanjin Kovacevic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Svetolik Spasic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Srdjan Lopicic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Jasna Todorovic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Marko Dincic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Marija Stanojevic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
| | - Marina Savin
- Clinic of Nephrology, Clinical Center of Serbia, Medical Faculty, University of Belgrade, Serbia
| | - Aleksandar Milovanovic
- Insitute of Occupational Health, Clinical Center of Serbia, Medical Faculty, University of Belgrade, Serbia
| | - Dusan Cemerikic
- Institute of Pathophysiology, Medical Faculty, University of Belgrade, Serbia
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7
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8
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Chloroquine, a novel inhibitor of amino acid transport by rat renal brush border membrane vesicles. Amino Acids 2013; 8:141-58. [PMID: 24186324 DOI: 10.1007/bf00806488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/1994] [Accepted: 07/19/1994] [Indexed: 10/26/2022]
Abstract
Chloroquine is an antimalarial and antirheumatic lysosomotropic drug which inhibits taurine uptake into and increases efflux from cultured human lymphoblastoid cells. It inhibits taurine uptake by rat lung slices and affects the uptake and release of cystine from cystinotic fibroblasts. Speculations on its mode of action include a proton gradient effect, a non-specific alteration in membrane integrity, and membrane stabilization. In this study, the effect of chloroquine on the uptake of several amino acids by rat renal brush border membrane vesicles (BBMV) was examined. Chloroquine significantly inhibited the secondary active, NaCl-dependent component of 10µM taurine uptake at all concentrations tested, but did not change equilibrium values. Analysis of these data indicated that the inhibition was non-competitive. Taurine uptake was reduced at all osmolarities tested, but inhibition was greatest at the lowest osmolarity. Taurine efflux was not affected by chloroquine, nor was the NaCl-independent diffusional component of taurine transport. Chloroquine (1 mM) inhibited uptake of the imino acids L-proline and glycine, and the dibasic amino acid L-lysine. It inhibited the uptake of D-glucose, but not the neutralα-amino acids L-alanine or L-methionine. Uptake of the dicarboxylic amino acids, L-glutamic acid and L-aspartic acid, was slightly enhanced. With regard to amino acid uptake by BBMV, these findings may support some of the currently proposed mechanisms of the action of chloroquine but further studies are indicated to determine why it affects the initial rate of active amino acid transport.
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9
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Yang Y, Zhang Y, Liu X, Zuo J, Wang K, Liu W, Ge J. Exogenous taurine attenuates mitochondrial oxidative stress and endoplasmic reticulum stress in rat cardiomyocytes. Acta Biochim Biophys Sin (Shanghai) 2013; 45:359-67. [PMID: 23619568 DOI: 10.1093/abbs/gmt034] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Taurine, a conditionally essential amino acid, plays a critical role in cardiovascular function. Here we examined the effect of taurine on mitochondria and endoplasmic reticulum in rat cardiomyocytes during glucose deprivation (GD). Data showed that cell viability, intracellular taurine contents, and taurine transporter expression were decreased during GD. In contrast, an increase in reactive oxygen species and intracellular Ca(2+) contents was observed. GD also caused disrupted mitochondrial membrane potential, apoptotic cell death, and dissociation of unfolded protein response (UPR)-relative proteins in cardiomyocytes. Signal transduction analysis showed that Bcl-2 family protein balance was disturbed, caspase-12 was activated and UPR-relative protein levels were up-regulated. Moreover, pre-treatment with 80 mM exogenous taurine attenuated GD effect in cardiomyocytes. Our results suggest that taurine have beneficial effects on inhibiting mitochondria-dependent cell apoptosis and UPR-associated cell apoptosis and might have clinical implications on acute myocardial infarction in future.
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Affiliation(s)
- Yujie Yang
- Department of Cellular and Genetic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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10
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Han X, Chesney RW. The role of taurine in renal disorders. Amino Acids 2012; 43:2249-63. [DOI: 10.1007/s00726-012-1314-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 04/24/2012] [Indexed: 01/10/2023]
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11
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Bröer S. Amino acid transport across mammalian intestinal and renal epithelia. Physiol Rev 2008; 88:249-86. [PMID: 18195088 DOI: 10.1152/physrev.00018.2006] [Citation(s) in RCA: 614] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The transport of amino acids in kidney and intestine is critical for the supply of amino acids to all tissues and the homeostasis of plasma amino acid levels. This is illustrated by a number of inherited disorders affecting amino acid transport in epithelial cells, such as cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, dicarboxylic aminoaciduria, and some other less well-described disturbances of amino acid transport. The identification of most epithelial amino acid transporters over the past 15 years allows the definition of these disorders at the molecular level and provides a clear picture of the functional cooperation between transporters in the apical and basolateral membranes of mammalian epithelial cells. Transport of amino acids across the apical membrane not only makes use of sodium-dependent symporters, but also uses the proton-motive force and the gradient of other amino acids to efficiently absorb amino acids from the lumen. In the basolateral membrane, antiporters cooperate with facilitators to release amino acids without depleting cells of valuable nutrients. With very few exceptions, individual amino acids are transported by more than one transporter, providing backup capacity for absorption in the case of mutational inactivation of a transport system.
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Affiliation(s)
- Stefan Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
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12
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Sved DW, Godsey JL, Ledyard SL, Mahoney AP, Stetson PL, Ho S, Myers NR, Resnis P, Renwick AG. Absorption, tissue distribution, metabolism and elimination of taurine given orally to rats. Amino Acids 2007; 32:459-66. [PMID: 17514497 DOI: 10.1007/s00726-007-0494-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Accepted: 01/11/2007] [Indexed: 10/23/2022]
Abstract
Three biodisposition studies with taurine were performed in male and female adult rats at dosages of 30 and 300 mg/kg. A single oral dose of (14)C-taurine was rapidly absorbed, distributed to tissues and excreted unchanged in urine. Elimination of radioactivity from intracellular pools was slow. Pre-treatment of animals for 14 days with unlabelled taurine did not significantly affect the fate of (14)C-taurine. At the higher dose there was more extensive excretion combined with a lower percentage of the dose in the carcass, indicating the possibility of saturation of the tubular reabsorption mechanism for taurine. Daily administration of unlabelled taurine for 14 days did not result in an increase in total taurine in the brain. The data indicate that exogenous taurine rapidly equilibrates with endogenous body pools and that any excess is rapidly eliminated by the kidneys.
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Affiliation(s)
- D W Sved
- WIL Research Laboratories, LLC, Ashland, OH 44805, U.S.A.
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13
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Han X, Patters AB, Jones DP, Zelikovic I, Chesney RW. The taurine transporter: mechanisms of regulation. Acta Physiol (Oxf) 2006; 187:61-73. [PMID: 16734743 DOI: 10.1111/j.1748-1716.2006.01573.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Taurine transport undergoes an adaptive response to changes in taurine availability. Unlike most amino acids, taurine is not metabolized or incorporated into protein but remains free in the intracellular water. Most amino acids are reabsorbed at rates of 98-99%, but reabsorption of taurine may range from 40% to 99.5%. Factors that influence taurine accumulation include ionic environment, electrochemical charge, and post-translational and transcriptional factors. Among these are protein kinase C (PKC) activation and transactivation or repression by proto-oncogenes such as WT1, c-Jun, c-Myb and p53. Renal adaptive regulation of the taurine transporter (TauT) was studied in vivo and in vitro. Site-directed mutagenesis and the oocyte expression system were used to study post-translational regulation of the TauT by PKC. Reporter genes and Northern and Western blots were used to study transcriptional regulation of the taurine transporter gene (TauT). We demonstrated that (i) the body pool of taurine is controlled through renal adaptive regulation of TauT in response to taurine availability; (ii) ionic environment, electrochemical charge, pH, and developmental ontogeny influence renal taurine accumulation; (iii) the fourth segment of TauT is involved in the gating of taurine across the cell membrane, which is controlled by PKC phosphorylation of serine 322 at the post-translational level; (iv) expression of TauT is repressed by the p53 tumour suppressor gene and is transactivated by proto-oncogenes such as WT1, c-Jun, and c-Myb; and (v) over-expression of TauT protects renal cells from cisplatin-induced nephrotoxicity.
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Affiliation(s)
- X Han
- Department of Pediatrics, The University of Tennessee Health Science Center, Memphis, TN 38103, USA
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14
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Bröer S, Cavanaugh JA, Rasko JEJ. Neutral amino acid transport in epithelial cells and its malfunction in Hartnup disorder. Biochem Soc Trans 2005; 33:233-6. [PMID: 15667315 DOI: 10.1042/bst0330233] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hartnup disorder is an autosomal recessive abnormality of renal and gastrointestinal neutral amino acid transport. A corresponding transport activity has been characterized in kidney and intestinal cells and named system B(0). The failure to resorb amino acids in this disorder is thought to be compensated by a protein-rich diet. However, in combination with a poor diet and other factors, more severe symptoms can develop in Hartnup patients, including a photosensitive pellagra-like skin rash, cerebellar ataxia and other neurological symptoms. Homozygosity mapping in a Japanese family and linkage analysis on six Australian pedigrees placed the Hartnup disorder gene at a locus on chromosome 5p15. This fine mapping facilitated a candidate gene approach within the interval, which resulted in the cloning and characterization of a novel member of the sodium-dependent neurotransmitter transporter family (B(0)AT1, SLC6A19) from mouse and human kidney, which shows all properties of system B(0). Flux experiments and electrophysiological recording showed that the transporter is Na(+) dependent and Cl(-) independent, electrogenic and actively transports most neutral amino acids. In situ hybridization showed strong expression in intestinal villi and in the proximal tubule of the kidney. Expression of B(0)AT1 was restricted to kidney, intestine and skin. A total of ten mutations have been identified in SLC6A19 that co-segregate with disease in the predicted recessive manner, with the majority of affected individuals being compound heterozygotes. These mutations lead to altered neutral amino acid transport function compared to the wild-type allele in vitro. One of the mutations occurs in members of the original Hartnup family described in 1956, thereby defining SLC6A19 as the 'Hartnup'-gene.
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Affiliation(s)
- S Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia.
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15
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Zelikovic I, Wager-Miller J. Proline transport in MDCK cells expressing a mutant regulatory subunit of cAMP-dependent protein kinase. Mol Genet Metab 2001; 72:45-53. [PMID: 11161828 DOI: 10.1006/mgme.2000.3110] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
cAMP-dependent protein kinase (cAK) regulates the activity of several membrane-bound ion channels and carriers. The role of cAK in regulating the transport of osmoprotective amino acids in the distal tubule is unknown. We examined the regulation of Na(+)- and Cl(-)-dependent proline transport in MDCK cells expressing a mutant murine regulatory subunit (RIalpha(AB)) of cAK. For this purpose, MDCK cells were transfected with an expression vector encoding RIalpha(AB) driven by the metallothionein 1 promoter together with neomycin-resistance (NEO) gene. Stable G418-resistant colonies were isolated that expressed RIalpha(AB) as demonstrated by Northern hybridization analysis using a cDNA probe for RIalpha and cAK assay that showed decreased enzyme activity. A clone constitutively expressing high levels of RIalpha(AB) (M(AB)) in a Zn-independent manner and a control clone transfected with the NEO gene alone (M(neo)) were selected for transport studies. We examined the effect of the cAMP-stimulating agents forskolin (F) and IBMX on NaCl-dependent uptake of [(3)H]proline by confluent monolayers of transfected MDCK cells. While F/IBMX-induced mean inhibition of proline transport in M(neo) cells was 48 and 45% at 5 and 15 min, respectively, inhibition of proline uptake in M(AB) cells was 9% (5 min) and 0% (15 min). These data demonstrate that the inhibition of NaCl-linked proline transport in response to elevated cAMP is reversed in MDCK clones that express mutant cAK and provide evidence that cAK mediates the modulatory action of cAMP on proline transport. cAK may play an important role in controlling transport of proline and other osmoprotective amino acids in the renal tubule.
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Affiliation(s)
- I Zelikovic
- Department of Pediatrics, Division of Nephrology, University of Washington School of Medicine, 4800 Sand Point Way NW, Seattle, Washington 98105, USA.
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16
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Zelikovic I, Budreau-Patters A. Cl- and membrane potential dependence of amino acid transport across the rat renal brush border membrane. Mol Genet Metab 1999; 67:236-47. [PMID: 10381331 DOI: 10.1006/mgme.1999.2866] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The relative roles of the anion present and the membrane potential in the operation of each of the seven amino acid transport systems in the renal tubular brush border membrane were explored by manipulating transmembrane potential and chemical gradients across the membrane. The effect of various external anions with different permeabilities of the membrane and of valinomycin-generated K+ diffusion potential on Na+-coupled amino acid accumulation by rat renal brush border membrane vesicles was examined. Accumulation of all amino acids examined, except for cystine, was membrane potential dependent. The highest voltage dependence was observed for taurine (equivalent to glucose) and l-methionine. Addition of taurine uptake values obtained under each electrical gradient (inside negative) and a chemical gradient (100 mM NaCl out) condition yielded markedly lower values than under conditions where there was a combined electrochemical gradient. Cl- gradient rather than merely imposing a voltage gradient was a specific mediator of Na+-coupled transport of l-proline, taurine, l-glutamic acid, and glycine across the brush border membrane. Cl- gradient alone under Na+-equilibrated conditions could energize an overshoot of taurine accumulation by vesicles providing evidence that taurine is energetically activated by and coupled to Cl- transport. These data suggest that Na+-linked transport of most amino acids across the tubular luminal membrane is an electrogenic positive process and for proline, taurine, glutamic acid, and glycine, a Cl--requiring process. A negative intracellular potential combined with luminal chloride is required for optimal Na+-coupled transport of these amino acids across the luminal membrane of the proximal tubule. The coupling of Cl- to the transport of these osmoprotective amino acids may enhance their volume regulatory effect in kidney cells and other mammalian cells.
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Affiliation(s)
- I Zelikovic
- Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, USA.
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17
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Hilgers KF, Nagaraj SK, Karginova EA, Kazakova IG, Chevalier RL, Carey RM, Pentz ES, Gomez RA. Molecular cloning of KS, a novel rat gene expressed exclusively in the kidney. Kidney Int 1998; 54:1444-54. [PMID: 9844120 DOI: 10.1046/j.1523-1755.1998.00143.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND We aimed to identify genes with kidney specific, developmentally regulated expression. Here we report the cDNA sequence and expression pattern of KS, a novel kidney-specific rat gene. METHODS A partial cDNA was identified by differential display polymerase chain reaction (PCR) of a renal cell fraction enriched for proximal tubular and renin-expressing cells. Using the partial cDNA as a probe, a rat kidney cDNA library was screened. The full-length KS sequence was obtained by PCR amplification of cDNA ends. The expression pattern of KS was investigated by Northern blot. RNA was extracted from several organs of newborn and adult rats, as well as from the kidneys of rats with altered tubular function, that is, rats that had undergone unilateral nephrectomy, unilateral ureteral obstruction, neonatal losartan treatment, and the appropriate control animals. The expression of KS was also investigated in the kidneys of rats with spontaneous or renovascular hypertension. RESULTS The KS cDNA (2426 bp) contained one open reading frame encoding a predicted 572 amino acid protein. The derived peptide sequence displayed approximately 70% similarity to the hypertension-related SA gene product and approximately 50% similarity to prokaryotic and eukaryotic acetyl-CoA synthases (EC 6. 2.1.1). KS was expressed in the kidney and not in any other organ assayed. KS RNA was not detected in fetal and newborn rat kidney but became apparent after one week of postnatal life. Gene expression was downregulated in rat models of altered tubular function. KS expression was decreased in spontaneously hypertensive rats but not in renovascular hypertension. CONCLUSION KS, a novel rat gene, exhibits a unique tissue-specific expression exclusively in mature kidneys. The data suggest KS may encode an adenosine monophosphate binding enzyme.
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Affiliation(s)
- K F Hilgers
- Departments of Pediatrics and Internal Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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18
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Nissim I, States B, Nissim I, Lin ZP, Yudkoff M. Hormonal regulation of glutamine metabolism by OK cells. Kidney Int 1995; 47:96-105. [PMID: 7731175 DOI: 10.1038/ki.1995.11] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The precise mechanism(s) of action of PTH, insulin or glucagon in the regulation of renal glutamine and ammonia metabolism is unknown. Our aim was to delineate the effects and the site(s) of action of these hormones on renal glutamine metabolism. Experiments were carried out using OK cells as a model system. Cell cultures were incubated for three hours in a bicarbonate buffer of pH 7.4 supplemented with either 1 mM [2-15N] or [5-15N] glutamine and 10(-7) M PTH, insulin or glucagon. Comparative studies were performed at pH 6.8, 7.4 or 7.6 without hormone. PTH and acute acidosis significantly stimulated glutamine metabolism via both the phosphate-dependent glutaminase (PDG) and glutamate dehydrogenase (GLDH) pathways. The opposite was observed at pH 7.6. Insulin augmented flux via PDG with little effect on the GLDH pathway. Glucagon had insignificant effects on either PDG or GLDH pathways. Intracellular [15N] glutamate formed from [2-15N] glutamine was removed partially by transamination to alanine, aspartate and serine and partially by translocation to an extracellular compartment. Acidosis, PTH and insulin enhanced the formation of [15N] alanine with little effect on [15N] aspartate. PTH, insulin and glucagon significantly stimulated the production of [15N]serine, whereas acidosis had little effect. The translocation of intracellular glutamate was significantly increased by acidosis, PTH and insulin and decreased by acute alkalosis. The data indicate that: (a) PTH mimicks the effect of acute acidosis on renal glutamine metabolism, that is, augmented glutamine metabolism through both PDG and GLDH pathways and stimulated the output of intracellular glutamate. This effect might be mediated via decreased activity of the Na(+)-H+ exchanger associated with cellular acidification and/or through a second messenger; (b) insulin, but not glucagon, increased glutamine uptake and metabolism, and simultaneously enhanced output of intracellular glutamate sufficiently to stimulate the PDG pathway; and (c) overall, glucagon had little effect on glutamine metabolism by OK cells compared with either PTH or insulin.
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Affiliation(s)
- I Nissim
- Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Department of Pediatrics, USA
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19
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Fleck C, Bräunlich H. Renal handling of drugs and amino acids after impairment of kidney or liver function--influences of maturity and protective treatment. Pharmacol Ther 1995; 67:53-77. [PMID: 7494861 DOI: 10.1016/0163-7258(95)00010-e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Renal tubular cells are involved both in secretion and in reabsorption processes within the kidney. Normally, most xenobiotics are secreted into the urine at the basolateral membrane of the tubular cell, whereas amino acids are reabsorbed quantitatively at the luminal side. Under different pathological or experimental circumstances, these transport steps may be changed, e.g., they may be reduced by renal impairment (reduction of kidney mass, renal ischemia, administration of nephrotoxins) or they may be enhanced after stimulation of transport carriers. Furthermore, a distinct interrelationship exists between excretory functions of the kidney and the liver. That means liver injury can influence renal transport systems also (hepato-renal syndrome). In this review, the following aspects were included: based upon general information concerning different transport pathways for xenobiotics and amino acids within kidney cells and upon a brief characterization of methods for testing impairment of kidney function, the maturation of renal transport and its stimulation are described. Similarities and differences between the postnatal development of kidney function and the increase of renal transport capacity after suitable stimulatory treatment by, for example, various hormones or xenobiotics are reviewed. Especially, renal transport in acute renal failure is described for individuals of different ages. Depending upon the maturity of kidney function, age differences in susceptibility to kidney injury occur: if energy-requiring processes are involved in the transport of the respective substance, then adults, in general, are more susceptible to renal failure than young individuals, because in immature organisms, anaerobic energy production predominates within the kidney. On the other hand, adult animals can better compensate for the loss of renal tissue (partial nephrectomy). With respect to stimulation of renal transport capacity after repeated pretreatment with suitable substances, age differences also exist: most stimulatory schedules are more effective in young, developing individuals than in mature animals. Therefore, the consequences of the stimulation of renal transport can be different in animals of different ages and are discussed in detail. Furthermore, the extent of stimulation is different for the transporters located at the basolateral and at the luminal membranes: obviously the tubular secretion at the contraluminal membrane can be stimulated more effectively than reabsorption processes at the luminal side.
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Affiliation(s)
- C Fleck
- Institute of Pharmacology and Toxicology, Freidrich Schiller University of Jena, Germany
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20
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Chesney RW, Jones D, Zelikovic I. Renal amino acid transport: cellular and molecular events from clearance studies to frog eggs. Pediatr Nephrol 1993; 7:574-84. [PMID: 8251325 DOI: 10.1007/bf00852553] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
This article reviews recent advances in the mechanisms of renal amino acid transport. Renal amino acid transport is necessary to efficiently reclaim approximately 450 mmol amino acids from the glomerular ultrafiltrate each day in man. In general, individual amino acids are transported across the epithelial membrane of the proximal tubule by a sodium (Na+) dependent mechanism. This cotransport process utilizes the energy of the Na+ gradient to enter the cell. The amino acid then exits the basolateral surface and Na+ is pumped out by the Na(+)-K(+)-ATPase located in the basolateral membrane. In addition to the cellular accumulation of amino acids across the luminal membrane, these compounds may be taken up by the cell from the basolateral surface. Most amino acids are transported both individually and in a series of seven group specific processes. Human disorders of amino acid transport have been described for six of the seven transport systems. The process of ontogeny of amino acid accumulation by the proximal tubule is a complex one and will be further discussed in this review. A number of factors including pH, ion dependency, electrogenicity of transport process, as well as a variety of hormonal factors, may contribute to the regulation of amino acid transport. Gene expression of several amino acid transporters has been successfully performed using the oocyte of the frog Xenopus laevis. Using this system, a number of transporters have been cloned. Such a strategy will permit the cloning of virtually all transporter molecules, and thus we can anticipate the elucidation of the structure of the transporters. However, for a comprehensive understanding of cytoskeletal interactions protein phosphorylation and phospholipid domains and their linkage to the primary structure of the transporter need to be studied. The future for research in this area is indeed a bright one.
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Affiliation(s)
- R W Chesney
- Department of Pediatrics, University of Tennessee, Memphis College of Medicine
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21
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Abstract
Changes in tubular reabsorption of amino acids and other solutes are characteristic of the immature renal tubule and of various hereditary nephropathies. The cellular mechanisms governing these aberrations in renal amino acid transport have not been established. Calcium (Ca2+)-dependent protein kinases are known to phosphorylate membrane-bound carrier proteins, thereby modulating transport of various solutes by the proximal tubule. The role of these enzymes in regulating renal tubular amino acid transport, particularly during kidney development, is unknown. We investigated: (1) the effect of Ca(2+)- and phospholipid-dependent protein kinase [protein kinase C (PKC)] and Ca2+/calmodulin-dependent protein kinase II (CaMKII) on sodium chloride (NaCl)-linked proline transport by renal brush border membrane vesicles (BBMV) from adult rats using the "hypoosmotic shock" technique (lysis of vesicles); (2) the activity, expression and subcellular distribution (cytosol, particulate, BBM) of Ca(2+)-dependent protein kinases in kidneys from 7-day-old and adult rats using MBP 4-14 and autocamtide II phosphorylation assays for PKC and CaMKII, respectively, endogenous protein phosphorylation (using gel electrophoresis and autoradiography) and Western immunoblot analysis to detect PKC and CaMKII. The studies showed: (1) endogenous (membrane-bound) CaMKII and PKC as well as exogenous, highly purified PKC inhibit proline uptake by phosphorylated, lyzed/resealed BBMV when compared with control vesicles; the voltage-clamped, nonelectrogenic component of proline transport was inhibited by PKC- but not CaMKII-mediated phosphorylation; (2) a Ca(2+)-dependent activity of both kinases was evident in all subcellular fractions tested in immature and adult kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- I Zelikovic
- Department of Pediatrics, University of Washington, Seattle
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22
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Chesney RW, Budreau AM. Efflux of taurine from renal brush border membrane vesicles: is it adaptively regulated? Pediatr Nephrol 1993; 7:35-40. [PMID: 8382504 DOI: 10.1007/bf00861561] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The uptake of the beta-amino acid taurine by rat renal brush border membrane vesicles (BBMV) adapts to changes in dietary sulfur amino acid intake. Initial rate Vmax "upregulates" after ingestion of a low methionine and taurine diet (LTD) and "downregulates" after a high taurine diet (HTD). This is reflected in vivo by hypotaurinuria after a LTD (90% reduction in excretion) and an 18-fold increase in urine taurine after a HTD. This study was performed to determine whether taurine efflux from BBMV is adaptively regulated by external taurine concentration or by diet. Vesicles were preloaded with varying concentrations of radiolabelled and unlabelled taurine and a 150 mM concentration of various salts. Efflux conditions were: taurine and 150 mM salt inside and 150 mM salt outside. The efflux of five concentrations of taurine (10-500 microM) was linear over 6 min, reached equilibrium by 21 min, and was dependent upon intravesicular taurine content. The kinetic characteristics of efflux (E) were significantly different from influx (I): Km = 109.8 +/- 5.8 (E) versus 23.6 +/- 4.2 (I), P < 0.001 [time of linearity = 360 s (E) vs. 20 s (I)]. Efflux of taurine was dependent on the presence of both sodium and chloride in the system, but neither external taurine content (0.100 microM, 1,000 microM) nor external beta-alanine altered initial efflux. Feeding rats a normal diet, LTD, or fasting altered taurine uptake but not efflux. Efflux does not appear to play a role in the adaptive regulation of taurine transport found in all mammalian species.
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Affiliation(s)
- R W Chesney
- Department of Pediatrics, University of Tennessee, Memphis
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23
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Lao L, Franklin RB, Costello LC. High-affinity L-aspartate transporter in prostate epithelial cells that is regulated by testosterone. Prostate 1993; 22:53-63. [PMID: 8426838 DOI: 10.1002/pros.2990220108] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The prostate gland produces and secretes extraordinarily high levels of citrate. Studies with rat ventral prostate (VP) have demonstrated that aspartate can serve as a four-carbon source of oxalacetate in the synthesis of citrate. To achieve this, prostate secretory epithelial cells must contain a transport system for the active uptake of aspartate from circulation. The present studies with VP epithelial cells confirm the existence of a Na(+)-dependent high-affinity L-aspartate transporter. The transporter has an optimal pH approximately 7.5 and is temperature dependent. It appears to be an anionic amino acid transporter capable of transporting L-glutamate but not basic or neutral amino acids. The transporter is inhibited by ATPase inhibitors, thereby indicating its dependency on a Na+ gradient. The characteristics of the high-affinity L-aspartate transporter are consistent with its operation at the basilar membrane for the transport of circulating aspartate into the cell. Castration (24 hr) resulted in a significant decrease in the ability of VP epithelial cells to transport L-aspartate. The administration of testosterone to castrated rats completely restored L-aspartate transport. In addition, in vitro testosterone addition (10(-8) M for 30 min) to isolated prostate epithelial cells markedly increased L-aspartate transport. Both cycloheximide and actinomycin inhibited the testosterone effect. The studies reveal that testosterone is a regulator of this Na(+)-dependent high-affinity L-aspartate transporter. The mechanism of this testosterone effect appears to involve both RNA and protein synthesis. We now have a model system to elucidate this novel effect of testosterone.
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Affiliation(s)
- L Lao
- Department of Physiology, Dental School, University of Maryland, Baltimore 21201
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25
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Kinne R, Kinne‐Saffran E. Renal Plasma Membranes: Isolation, General Properties, and Biochemical Components. Compr Physiol 1992. [DOI: 10.1002/cphy.cp080245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Law RO. Amino acids as volume-regulatory osmolytes in mammalian cells. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1991; 99:263-77. [PMID: 1678326 DOI: 10.1016/0300-9629(91)90001-s] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. This review summarizes current knowledge relating to the volume-regulatory and osmoprotective functions of amino acids in mammalian cells exposed to anisosmotic fluids. 2. Experiments in vivo and in vitro have established that they play a significant role in regulating brain cell volume under these conditions, and that taurine may be of particular importance in this respect. 3. Their possible role in renal medulla is discussed, and it is suggested that they may protect cells against acute (but not long-term) osmotic variation. 4. Evidence is briefly presented regarding adaptive changes in amino acid content of other cell types.
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Affiliation(s)
- R O Law
- Department of Physiology, University of Leicester, U.K
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27
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Chesney RW, Zelikovic I, Jones DP, Budreau A, Jolly K. The renal transport of taurine and the regulation of renal sodium-chloride-dependent transporter activity. Pediatr Nephrol 1990; 4:399-407. [PMID: 2206910 DOI: 10.1007/bf00862526] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A model for the beta-amino acid taurine transport is presented to help define the ionic, pH, and voltage requirements for the movement of taurine into the rat proximal tubule brush border membrane vesicle (BBMV). Sodium-(Na+)-taurine symport across the apical surface of the proximal tubule has a highly specific requirement for Cl- and Br-. Active taurine transport operates with a 2 Na+:1 Cl-:1 taurine-carrier complex. Complexes like the one required for maximal taurine transport may be pertinent for many other amino acids whose uptake is Na(+)-dependent. Renal epithelial cell lines LLC-PK and MDCK were used to define the nature of taurine uptake; they express Na(+)-Cl(-)-taurine cotransport that is inhibited by beta-alanine. The cell lines up- or down-regulate taurine transport in response to changes in the taurine concentration of the medium in a manner similar to that seen in BBMV. The adaptation is present by 12 h and depends on new protein synthesis and protein import to the cell membrane. The role of trafficking in the adaptive response was also explored in brush border vesicles. During dietary surfeit, transporter could be down-regulated and transporters could be shifted back into the microtubule system, resulting in taurinuria. Use of continuous renal cell lines allowed a more mechanistic exploration of intracellular trafficking in the up- and down-expression of the Na(+)-Cl(-)-taurine cotransporter. Colchicine appeared to be a more potent inhibitor of the rapid (over hours) adaptive response to a reduction in media and, therefore, intracellular taurine content.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R W Chesney
- Department of Pediatrics, University of Tennessee, Memphis, 38103
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28
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Abstract
The reabsorption of amino acids by the proximal tubule is remarkably efficient. Current evidence indicates that this process occurs by Na+-amino acid cotransport or symport. The energy for amino acid entry is derived from the chemical and voltage gradient for Na+ entry across the apical surface of the renal cell maintained by pumping Na+ out of the cell by Na+-K+-adenosine triphosphatase (ATPase) activity at the basolateral membrane. We chose the beta-amino acid taurine to study the anionic requirements as well as voltage- and pH-dependence of Na+-taurine symport into rat proximal tubule brush border membrane vesicles. Maximal uptake was found when Cl- or Br- were the anions. The addition of various ionophores (amiloride, carbonyl cyanide-n chlorophenyl-hydrazone, and valinomycin) under pH-equilibrated conditions did not change taurine entry into the vesicle. Hill equation analysis of the initial rate of taurine uptake into vesicles indicates that transport operates by means of a 2 Na+:1 Cl-:1 taurine-carrier complex. Because taurine is a zwitterion, this complex has a net positive charge. Its entry into the vesicle is favored by the imposition of an outwardly directed K+ gradient in the presence of valinomycin. The movement of a quaternary complex of this type across the apical surface of the proximal tubular cell would assure that the movement of both Cl- and the amino acid is energized by the Na+ gradient. Because most amino acids are zwitterions at physiologic pH this complex would be positively charged, favoring entry into the voltage negative renal cell interior.
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Affiliation(s)
- I Zelikovic
- Department of Pediatrics, University of Tennessee, College of Medicine, Memphis
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