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Tholen LE, Hoenderop JGJ, de Baaij JHF. Mechanisms of ion transport regulation by HNF1β in the kidney: beyond transcriptional regulation of channels and transporters. Pflugers Arch 2022; 474:901-916. [PMID: 35554666 PMCID: PMC9338905 DOI: 10.1007/s00424-022-02697-5] [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: 02/25/2022] [Revised: 04/19/2022] [Accepted: 04/22/2022] [Indexed: 01/01/2023]
Abstract
Hepatocyte nuclear factor 1β (HNF1β) is a transcription factor essential for the development and function of the kidney. Mutations in and deletions of HNF1β cause autosomal dominant tubule interstitial kidney disease (ADTKD) subtype HNF1β, which is characterized by renal cysts, diabetes, genital tract malformations, and neurodevelopmental disorders. Electrolyte disturbances including hypomagnesemia, hyperuricemia, and hypocalciuria are common in patients with ADTKD-HNF1β. Traditionally, these electrolyte disturbances have been attributed to HNF1β-mediated transcriptional regulation of gene networks involved in ion transport in the distal part of the nephron including FXYD2, CASR, KCNJ16, and FXR. In this review, we propose additional mechanisms that may contribute to the electrolyte disturbances observed in ADTKD-HNF1β patients. Firstly, kidney development is severely affected in Hnf1b-deficient mice. HNF1β is required for nephron segmentation, and the absence of the transcription factor results in rudimentary nephrons lacking mature proximal tubule, loop of Henle, and distal convoluted tubule cluster. In addition, HNF1β is proposed to be important for apical-basolateral polarity and tight junction integrity in the kidney. Interestingly, cilia formation is unaffected by Hnf1b defects in several models, despite the HNF1β-mediated transcriptional regulation of many ciliary genes. To what extent impaired nephron segmentation, apical-basolateral polarity, and cilia function contribute to electrolyte disturbances in HNF1β patients remains elusive. Systematic phenotyping of Hnf1b mouse models and the development of patient-specific kidney organoid models will be essential to advance future HNF1β research.
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Affiliation(s)
- Lotte E Tholen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P. O. Box 9101, Nijmegen, 6500 HB, The Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P. O. Box 9101, Nijmegen, 6500 HB, The Netherlands
| | - Jeroen H F de Baaij
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P. O. Box 9101, Nijmegen, 6500 HB, The Netherlands.
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2
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Tseng MH, Yang SS, Sung CC, Ding JJ, Hsu YJ, Chu SM, Lin SH. Novel CNNM2 Mutation Responsible for Autosomal-Dominant Hypomagnesemia With Seizure. Front Genet 2022; 13:875013. [PMID: 35846113 PMCID: PMC9277586 DOI: 10.3389/fgene.2022.875013] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 04/27/2022] [Indexed: 12/04/2022] Open
Abstract
CNNM2 is primarily expressed in the brain and distal convoluted tubule (DCT) of the kidney. Mutations in CNNM2 have been reported to cause hypomagnesemia, seizure, and intellectual disability (HSMR) syndrome. However, the clinical and functional effect of CNNM2 mutations remains incompletely understood. We report our clinical encounter with a 1-year-old infant with HSMR features. Mutation screening for this trio family was performed using next-generation sequencing (NGS)-based whole exome sequencing (WES) with the identified mutation verified by Sanger sequencing. We identified a de novo heterozygous mutation c.G1439T (R480L) in the essential cystathionine β-synthase (CBS) domain of CNNM2 encoding CNNM2 (cyclin M2) without any other gene mutations related to hypomagnesemia. The amino acid involved in this missense mutation was conserved in different species. It was also found to be pathogenic based on the different software prediction models and ACGME criteria. In vitro studies revealed a higher expression of the CNNM2-R480L mutant protein compared to that of the wild-type CNNM2. Like the CNNM2-wild type, proper localization of CNNM2-R480L was shown on immunocytochemistry images. The Mg2+ efflux assay in murine DCT (mDCT) cells revealed a significant increase in intracellular Mg2+ green in CNNM2-R480L compared to that in CNNM2-WT. By using a simulation model, we illustrate that the R480L mutation impaired the interaction between CNNM2 and ATP-Mg2+. We propose that this novel R480L mutation in the CNNM2 gene led to impaired binding between Mg2+-ATP and CNNM2 and diminished Mg2+ efflux, manifesting clinically as refractory hypomagnesemia.
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Affiliation(s)
- Min-Hua Tseng
- Division of Nephrology, Department of Pediatrics, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan.,Department of Pediatrics, Xiamen Chang Gung Hospital, Ximen, China
| | - Sung-Sen Yang
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Chih-Chien Sung
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Jhao-Jhuang Ding
- Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Yu-Juei Hsu
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Ming Chu
- Division of Neonatology, Department of Pediatrics, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan
| | - Shih-Hua Lin
- Division of Nephrology, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
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3
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Biondo ED, Spontarelli K, Ababioh G, Méndez L, Artigas P. Diseases caused by mutations in the Na +/K + pump α1 gene ATP1A1. Am J Physiol Cell Physiol 2021; 321:C394-C408. [PMID: 34232746 DOI: 10.1152/ajpcell.00059.2021] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Human cell survival requires function of the Na+/K+ pump; the heteromeric protein that hydrolyzes ATP to extrude Na+ and import K+ across the plasmalemma, thereby building and maintaining these ions' electrochemical gradients. Numerous dominant diseases caused by mutations in genes encoding for Na+/K+ pump catalytic (α) subunit isoforms highlight the importance of this protein. Here, we review literature describing disorders caused by missense mutations in ATP1A1, the gene encoding the ubiquitously expressed α1 isoform of the Na+/K+ pump. These various maladies include primary aldosteronism with secondary hypertension, an endocrine syndrome, Charcot-Marie-Tooth disease, a peripheral neuropathy, complex spastic paraplegia, another neuromuscular disorder, as well as hypomagnesemia accompanied by seizures and cognitive delay, a condition affecting the renal and central nervous systems. This article focuses on observed commonalities among these mutations' functional effects, as well as on the special characteristics that enable each particular mutation to exclusively affect a certain system, without affecting others. In this respect, it is clear how somatic mutations localized to adrenal adenomas increase aldosterone production without compromising other systems. However, it remains largely unknown how and why some but not all de novo germline or familial mutations (where the mutant must be expressed in numerous tissues) produce a specific disease and not the other diseases. We propose hypotheses to explain this observation and the approaches that we think will drive future research on these debilitating disorders to develop novel patient-specific treatments by combining the use of heterologous protein-expression systems, patient-derived pluripotent cells, and gene-edited cell and mouse models.
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Affiliation(s)
- Elisa D Biondo
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Kerri Spontarelli
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Giovanna Ababioh
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Lois Méndez
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
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Yap JQ, Seflova J, Sweazey R, Artigas P, Robia SL. FXYD proteins and sodium pump regulatory mechanisms. J Gen Physiol 2021; 153:211866. [PMID: 33688925 PMCID: PMC7953255 DOI: 10.1085/jgp.202012633] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 02/03/2021] [Indexed: 12/12/2022] Open
Abstract
The sodium/potassium-ATPase (NKA) is the enzyme that establishes gradients of sodium and potassium across the plasma membrane. NKA activity is tightly regulated for different physiological contexts through interactions with single-span transmembrane peptides, the FXYD proteins. This diverse family of regulators has in common a domain containing a Phe-X-Tyr-Asp (FXYD) motif, two conserved glycines, and one serine residue. In humans, there are seven tissue-specific FXYD proteins that differentially modulate NKA kinetics as appropriate for each system, providing dynamic responsiveness to changing physiological conditions. Our understanding of how FXYD proteins contribute to homeostasis has benefitted from recent advances described in this review: biochemical and biophysical studies have provided insight into regulatory mechanisms, genetic models have uncovered remarkable complexity of FXYD function in integrated physiological systems, new posttranslational modifications have been identified, high-resolution structural studies have revealed new details of the regulatory interaction with NKA, and new clinical correlations have been uncovered. In this review, we address the structural determinants of diverse FXYD functions and the special roles of FXYDs in various physiological systems. We also discuss the possible roles of FXYDs in protein trafficking and regulation of non-NKA targets.
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Affiliation(s)
- John Q Yap
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Jaroslava Seflova
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Ryan Sweazey
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
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van der Wijst J, Belge H, Bindels RJM, Devuyst O. Learning Physiology From Inherited Kidney Disorders. Physiol Rev 2019; 99:1575-1653. [PMID: 31215303 DOI: 10.1152/physrev.00008.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.
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Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Hendrica Belge
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Olivier Devuyst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
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6
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Abstract
PURPOSE OF REVIEW Identification of the mechanisms of magnesium absorption and reabsorption has markedly enhanced our understanding of the causes of hypomagnesemia. RECENT FINDINGS New gastrointestinal and renal causes of hypomagnesemia have been recently documented. SUMMARY The recognition of new mechanisms and causes of magnesium absorption and reabsorption should enhance the ability to monitor patients at risk for hypomagnesemia and improve our ability to mitigate the serious symptoms associated with this disorder.
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7
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Li H, Sun S, Chen J, Xu G, Wang H, Qian Q. Genetics of Magnesium Disorders. KIDNEY DISEASES 2017; 3:85-97. [PMID: 29344503 DOI: 10.1159/000477730] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 05/23/2017] [Indexed: 12/30/2022]
Abstract
Background Magnesium (Mg2+), the second most abundant cation in the cell, is woven into a multitude of cellular functions. Dysmagnesemia is associated with multiple diseases and, when severe, can be life-threatening. Summary This review discusses Mg2+ homeostasis and function with specific focus on renal Mg2+ handling. Intrarenal channels and transporters related to Mg2+ absorption are discussed. Unraveling the rare genetic diseases with manifestations of dysmagnesemia has greatly increased our understanding of the complex and intricate regulatory network in the kidney, specifically, functions of tight junction proteins including claudin-14, -16, -19, and -10; apical ion channels including: TRPM6, Kv1.1, and ROMK; small regulatory proteins including AC3 and ANK3; and basolateral proteins including EGF receptor, γ-subunit (FXYD2) of Na-K-ATPase, Kir4.1, CaSR, CNNM2, and SLC41A. Although our understanding of Mg2+ handling of the kidney has expanded considerably in the last two decades, many questions remain. Future studies are needed to elucidate a multitude of unknown aspects of Mg2+ handling in the kidney. Key Message Understanding rare and genetic diseases of Mg2+ dysregulation has expanded our knowledge and furthers the development of strategies for preventing and managing dysmagnesemia.
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Affiliation(s)
- Heng Li
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
| | - Shiren Sun
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Jianghua Chen
- Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Goushuang Xu
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Hanmin Wang
- Department of Nephrology, Xijing Hospital, The Fourth Military Medical University, Xian, China
| | - Qi Qian
- Division of Nephrology and Hypertension, Department of Medicine, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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8
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Abstract
PURPOSE OF REVIEW The tight control of blood magnesium (Mg) levels is of central importance for numerous physiological processes. A persistent low Mg status (hypomagnesemia) is associated with severe health risks and is involved in the pathogenesis of type 2 diabetes mellitus, osteoporosis, asthma, and heart and vascular diseases. The current view has expanded significantly as a result of the identification of novel genes and regulatory pathways involved in hypomagnesemic disorders. This review aims to give an up-to-date overview of transient receptor potential melastatin 6 (TRPM6) regulation and its role in the maintenance of Mg homeostasis. RECENT FINDINGS The epithelial Mg channel TRPM6 is considered to be the Mg entry pathway in the distal convoluted tubule of the kidney, where it functions as gatekeeper for controlling the body's Mg balance. Various factors and hormones contribute not only to the function, but also to the dysregulation of TRPM6, which has a substantial impact on renal Mg handling. Recent genetic and molecular studies have further elucidated the signaling processes of epithelial Mg transport, including their effect on the expression and function of TRPM6. SUMMARY Knowledge of TRPM6 functioning is of vital importance to decipher its role in Mg handling and will, in particular, provide a molecular basis for achieving a better understanding of Mg mal(re)absorption and hence systemic Mg balance.
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Deeb A, Abood SA, Simon J, Dastoor H, Pearce SH, Sayer JA. A novel CLDN16 mutation in a large family with familial hypomagnesaemia with hypercalciuria and nephrocalcinosis. BMC Res Notes 2013; 6:527. [PMID: 24321194 PMCID: PMC3867415 DOI: 10.1186/1756-0500-6-527] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 12/05/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis is a rare tubulopathy leading to renal calcification and progressive renal failure. CASE PRESENTATION We report a consanguineous Arab family (of Qatari origin) with 7 affected siblings with variable phenotypes including hypomagnesaemia, hypercalciuria, nephrocalcinosis and renal stones. Presenting features included haematuria and recurrent urinary tract infections. As the biochemical and clinical phenotypes of this family resembled familial hypomagnesaemia with hypercalciuria and nephrocalcinosis, we performed genetic investigation in order to provide a precise molecular diagnosis. We screened all coding regions of the CLDN16 gene and identified a novel mutation (c.G647A, p.R216H) which was found homozygously in the six severely affected cases, who manifested significant nephrocalcinosis, often nephrolithiasis and sometimes reduced GFR. Parents were both heterozygous for the mutation and, together with children carrying the mutation in its heterozygous state, exhibited mild or no biochemical phenotypes. CONCLUSION Mutations in CLDN16 underlie familial hypomagnesaemia with hypercalciuria and nephrocalcinosis but remain a rare cause of nephrocalcinosis and nephrolithiasis. Management includes reduction of hypercalciuria with thiazide diuretics, correction of serum magnesium and close monitoring of renal function given the significant risk of end stage renal failure with this inherited form of nephrocalcinosis.
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Affiliation(s)
| | | | | | | | | | - John A Sayer
- Institute of Genetic Medicine, Newcastle University, International Centre for Life, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK.
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10
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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Abstract
Hypocalcemia is common in the critically ill patient. In this population, however, the diagnosis of hypocalcemia is complicated by limitations in the interpretation of the total plasma calcium concentration. These limitations are principally the result of the effects of hypoalbuminemia and disorders of acid-base balance on the total calcium concentration. Thus, measurement of ionized calcium can be critical in determining an individual's true serum calcium status. In this review, we first describe the regulation of normal calcium metabolism and then focus on the various etiologies of hypocalcemia, including congenital and acquired disorders of parathyroid hormone and vitamin D, which are encountered in the neonatal, pediatric, and adult critical care settings. The approach to the treatment of hypocalcemia and the current consensus on treatment of hypocalcemia in the critically ill patient is also presented.
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Affiliation(s)
- Andrea Kelly
- Division of Endocrinology and Diabetes, Department of Pediatrics, The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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12
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The salt-wasting phenotype of EAST syndrome, a disease with multifaceted symptoms linked to the KCNJ10 K+ channel. Pflugers Arch 2011; 461:423-35. [DOI: 10.1007/s00424-010-0915-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 12/10/2010] [Accepted: 12/17/2010] [Indexed: 11/25/2022]
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Harrington MG, Fonteh AN, Arakaki X, Cowan RP, Ecke LE, Foster H, Hühmer AF, Biringer RG. Capillary endothelial Na(+), K(+), ATPase transporter homeostasis and a new theory for migraine pathophysiology. Headache 2010; 50:459-78. [PMID: 19845787 PMCID: PMC8020446 DOI: 10.1111/j.1526-4610.2009.01551.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Cerebrospinal fluid sodium concentration ([Na(+)](csf)) increases during migraine, but the cause of the increase is not known. OBJECTIVE Analyze biochemical pathways that influence [Na(+)](csf) to identify mechanisms that are consistent with migraine. METHOD We reviewed sodium physiology and biochemistry publications for links to migraine and pain. RESULTS Increased capillary endothelial cell (CEC) Na(+), K(+), -ATPase transporter (NKAT) activity is probably the primary cause of increased [Na(+)](csf). Physiological fluctuations of all NKAT regulators in blood, many known to be involved in migraine, are monitored by receptors on the luminal wall of brain CECs; signals are then transduced to their abluminal NKATs that alter brain extracellular sodium ([Na(+)](e)) and potassium ([K(+)](e)). CONCLUSIONS We propose a theoretical mechanism for aura and migraine when NKAT activity shifts outside normal limits: (1) CEC NKAT activity below a lower limit increases [K(+)](e), facilitates cortical spreading depression, and causes aura; (2) CEC NKAT activity above an upper limit elevates [Na(+)](e), increases neuronal excitability, and causes migraine; (3) migraine-without-aura may arise from CEC NKAT over-activity without requiring a prior decrease in activity and its consequent spreading depression; (4) migraine triggers disturb, and treatments improve, CEC NKAT homeostasis; (5) CEC NKAT-induced regulation of neural and vasomotor excitability coordinates vascular and neuronal activities, and includes occasional pathology from CEC NKAT-induced apoptosis or cerebral infarction.
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Affiliation(s)
- Michael G Harrington
- Huntington Medical Research Institutes - Molecular Neurology, Pasadena, CA 91101, USA
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14
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New molecular players facilitating Mg2+ reabsorption in the distal convoluted tubule. Kidney Int 2010; 77:17-22. [DOI: 10.1038/ki.2009.358] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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15
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Cairo ER, Swarts HGP, Wilmer MJG, Willems PHGM, Levtchenko EN, De Pont JJHHM, Koenderink JB. FXYD2 and Na,K-ATPase expression in isolated human proximal tubular cells: disturbed upregulation on renal hypomagnesemia? J Membr Biol 2009; 231:117-24. [PMID: 19865785 PMCID: PMC2776943 DOI: 10.1007/s00232-009-9210-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 10/08/2009] [Indexed: 11/05/2022]
Abstract
Autosomal dominant renal hypomagnesemia (OMIM 154020), associated with hypocalciuria, has been linked to a 121G to A mutation in the FXYD2 gene. To gain insight into the molecular mechanisms linking this mutation to the clinical phenotype, we studied isolated proximal tubular cells from urine of a patient and a healthy subject. Cells were immortalized and used to assess the effects of hypertonicity-induced overexpression of FXYD2 on amount, activity and apparent affinities for Na+, K+ and ATP of Na,K-ATPase. Both cell lines expressed mRNA for FXYD2a and FXYD2b, and patient cells contained both the wild-type and mutated codons. FXYD2 protein expression was lower in patient cells and could be increased in both cell lines upon culturing in hyperosmotic medium but to a lesser extent in patient cells. Similarly, hyperosmotic culturing increased Na,K-ATPase protein expression and ATP hydrolyzing activity but, again, to a lesser extent in patient cells. Apparent affinities of Na,K-ATPase for Na+, K+ and ATP did not differ between patient and control cells or after hyperosmotic induction. We conclude that human proximal tubular cells respond to a hyperosmotic challenge with an increase in FXYD2 and Na,K-ATPase protein expression, though to a smaller absolute extent in patient cells.
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Affiliation(s)
- Edinio R Cairo
- Department of Biochemistry, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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16
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Laurila K, Vihinen M. Prediction of disease-related mutations affecting protein localization. BMC Genomics 2009; 10:122. [PMID: 19309509 PMCID: PMC2680896 DOI: 10.1186/1471-2164-10-122] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 03/23/2009] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Eukaryotic cells contain numerous compartments, which have different protein constituents. Proteins are typically directed to compartments by short peptide sequences that act as targeting signals. Translocation to the proper compartment allows a protein to form the necessary interactions with its partners and take part in biological networks such as signalling and metabolic pathways. If a protein is not transported to the correct intracellular compartment either the reaction performed or information carried by the protein does not reach the proper site, causing either inactivation of central reactions or misregulation of signalling cascades, or the mislocalized active protein has harmful effects by acting in the wrong place. RESULTS Numerous methods have been developed to predict protein subcellular localization with quite high accuracy. We applied bioinformatics methods to investigate the effects of known disease-related mutations on protein targeting and localization by analyzing over 22,000 missense mutations in more than 1,500 proteins with two complementary prediction approaches. Several hundred putative localization affecting mutations were identified and investigated statistically. CONCLUSION Although alterations to localization signals are rare, these effects should be taken into account when analyzing the consequences of disease-related mutations.
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Affiliation(s)
- Kirsti Laurila
- Institute of Medical Technology, FI-33014 University of Tampere, Finland
- Department of Signal Processing, Tampere University of Technology, P.O. Box 527, FI-33101 Tampere, Finland
| | - Mauno Vihinen
- Institute of Medical Technology, FI-33014 University of Tampere, Finland
- Tampere University Hospital, FI-33520 Tampere, Finland
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Knoers NVAM. Inherited forms of renal hypomagnesemia: an update. Pediatr Nephrol 2009; 24:697-705. [PMID: 18818955 PMCID: PMC7811505 DOI: 10.1007/s00467-008-0968-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 07/22/2008] [Accepted: 07/23/2008] [Indexed: 12/19/2022]
Abstract
The kidney plays an important role in ion homeostasis in the human body. Several hereditary disorders characterized by perturbations in renal magnesium reabsorption leading to hypomagnesemia have been described over the past 50 years, with the most important of these being Gitelman syndrome, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, familial hypomagnesemia with secondary hypocalcemia, autosomal dominant hypomagnesemia with hypocalciuria, and autosomal recessive hypomagnesemia. Only recently, following positional cloning strategies in affected families, have mutations in renal ion channels and transporters been identified in these diseases. In this short review, I give an update on these hypomagnesemic disorders. Elucidation of the genetic etiology and, for most of these disorders, also the underlying pathophysiology of the disease, has greatly increased our understanding of the normal physiology of renal magnesium handling. This is yet another example of the importance of studying rare disorders in order to unravel physiological and pathophysiological processes in the human body.
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Affiliation(s)
- Nine V. A. M. Knoers
- grid.10417.330000000404449382Department of Human Genetics 849, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
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18
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Regulation of magnesium reabsorption in DCT. Pflugers Arch 2008; 458:89-98. [DOI: 10.1007/s00424-008-0601-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 10/08/2008] [Indexed: 12/31/2022]
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19
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Vincenzi B, Santini D, Tonini G. Biological interaction between anti-epidermal growth factor receptor agent cetuximab and magnesium. Expert Opin Pharmacother 2008; 9:1267-9. [DOI: 10.1517/14656566.9.8.1267] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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20
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Naderi ASA, Reilly RF. Hereditary etiologies of hypomagnesemia. ACTA ACUST UNITED AC 2008; 4:80-9. [PMID: 18227801 DOI: 10.1038/ncpneph0680] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2007] [Accepted: 09/20/2007] [Indexed: 12/15/2022]
Abstract
Magnesium ions are essential to all living cells. As the second most abundant intracellular cation, magnesium has a crucial role in fundamental metabolic processes such as DNA and protein synthesis, oxidative phosphorylation, enzyme function, ion channel regulation, and neuromuscular excitability. After presenting an overview of magnesium homeostasis, we review the etiologies of hypomagnesemia, with an emphasis on hereditary causes.
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Affiliation(s)
- Amir Said Alizadeh Naderi
- Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-8837, USA.
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21
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Impaired routing of wild type FXYD2 after oligomerisation with FXYD2-G41R might explain the dominant nature of renal hypomagnesemia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:398-404. [DOI: 10.1016/j.bbamem.2007.10.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 10/09/2007] [Accepted: 10/10/2007] [Indexed: 11/21/2022]
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22
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Groenestege WMT, Thébault S, van der Wijst J, van den Berg D, Janssen R, Tejpar S, van den Heuvel LP, van Cutsem E, Hoenderop JG, Knoers NV, Bindels RJ. Impaired basolateral sorting of pro-EGF causes isolated recessive renal hypomagnesemia. J Clin Invest 2007; 117:2260-7. [PMID: 17671655 PMCID: PMC1934557 DOI: 10.1172/jci31680] [Citation(s) in RCA: 234] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 05/08/2007] [Indexed: 12/11/2022] Open
Abstract
Primary hypomagnesemia constitutes a rare heterogeneous group of disorders characterized by renal or intestinal magnesium (Mg(2+)) wasting resulting in generally shared symptoms of Mg(2+) depletion, such as tetany and generalized convulsions, and often including associated disturbances in calcium excretion. However, most of the genes involved in the physiology of Mg(2+) handling are unknown. Through the discovery of a mutation in the EGF gene in isolated autosomal recessive renal hypomagnesemia, we have, for what we believe is the first time, identified a magnesiotropic hormone crucial for total body Mg(2+) balance. The mutation leads to impaired basolateral sorting of pro-EGF. As a consequence, the renal EGFR is inadequately stimulated, resulting in insufficient activation of the epithelial Mg(2+) channel TRPM6 (transient receptor potential cation channel, subfamily M, member 6) and thereby Mg(2+) loss. Furthermore, we show that colorectal cancer patients treated with cetuximab, an antagonist of the EGFR, develop hypomagnesemia, emphasizing the significance of EGF in maintaining Mg(2+) balance.
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Affiliation(s)
- Wouter M. Tiel Groenestege
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Stéphanie Thébault
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Jenny van der Wijst
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Dennis van den Berg
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Rob Janssen
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Sabine Tejpar
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Lambertus P. van den Heuvel
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Eric van Cutsem
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Joost G. Hoenderop
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Nine V. Knoers
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - René J. Bindels
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Digestive Oncology Unit, Department of Internal Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium.
Department of Pediatrics and
Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Thébault S, Hoenderop JGJ, Bindels RJM. Epithelial Ca2+ and Mg2+ channels in kidney disease. Adv Chronic Kidney Dis 2006; 13:110-7. [PMID: 16580611 DOI: 10.1053/j.ackd.2006.01.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Many physiological functions rely on the precise maintenance of body calcium (Ca2+) and magnesium (Mg2+) balance, which is tightly regulated by the concerted actions of intestinal absorption, renal reabsorption, and exchange with bone. The kidney plays an important role in the homeostasis of divalent ions. Most Ca2+ and Mg2+ reabsorption occurs in the proximal tubules and the thick ascending limb of Henle's loop via a passive paracellular pathway. At the level of the distal convoluted tubule (DCT) and the connecting tubule (CNT), Ca2+ and Mg2+ are reabsorbed via an active transcellular route. Reabsorption of divalents in these latter segments is regulated in a Ca2+ and Mg2+-specific manner and determines the final excretion in the urine. Importantly, genetic studies, as well as molecular cloning strategies, recently identified epithelial ion channels as the gatekeepers of active Ca2+ and Mg2+ reabsorption. These channels are members of the transient receptor potential (TRP) superfamily. TRP vanilloid 5 (TRPV5) is responsible for the rate-limiting Ca2+ entry, and TRP melastatin 6 (TRPM6) constitutes the apical entry step in Mg2+ reabsorption. Dysregulation or malfunction of these influx pathways has been associated with renal Ca2+ and Mg2+ wasting. This review updates the current knowledge and the recent advances of Ca2+ and Mg2+ reabsorption and related disorders.
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Affiliation(s)
- Stéphanie Thébault
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Jones DH, Li TY, Arystarkhova E, Barr KJ, Wetzel RK, Peng J, Markham K, Sweadner KJ, Fong GH, Kidder GM. Na,K-ATPase from mice lacking the gamma subunit (FXYD2) exhibits altered Na+ affinity and decreased thermal stability. J Biol Chem 2005; 280:19003-11. [PMID: 15755730 DOI: 10.1074/jbc.m500697200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma subunit of the Na,K-ATPase, a 7-kDa single-span membrane protein, is a member of the FXYD gene family. Several FXYD proteins have been shown to bind to Na,K-ATPase and modulate its properties, and each FXYD protein appears to alter enzyme kinetics differently. Different results have sometimes been obtained with different experimental systems, however. To test for effects of gamma in a native tissue environment, mice lacking a functional gamma subunit gene (Fxyd2) were generated. These mice were viable and without observable pathology. Prior work in the mouse embryo showed that gamma is expressed at the blastocyst stage. However, there was no delay in blastocele formation, and the expected Mendelian ratios of offspring were obtained even with Fxyd2-/- dams. In adult Fxyd2-/- mouse kidney, splice variants of gamma that have different nephron segment-specific expression patterns were absent. Purified gamma-deficient renal Na,K-ATPase displayed higher apparent affinity for Na+ without significant change in apparent affinity for K+. Affinity for ATP, which was expected to be decreased, was instead slightly increased. The results suggest that regulation of Na+ sensitivity is a major functional role for this protein, whereas regulation of ATP affinity may be context-specific. Most importantly, this implies that gamma and other FXYD proteins have their effects by local and not global conformation change. Na,K-ATPase lacking the gamma subunit had increased thermal lability. Combined with other evidence that gamma participates in an early step of thermal denaturation, this indicates that FXYD proteins may play an important structural role in the enzyme complex.
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Affiliation(s)
- D Holstead Jones
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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