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Guo J, Zhang C, Zhao H, Yan Y, Liu Z. The key mediator of diabetic kidney disease: Potassium channel dysfunction. Genes Dis 2024; 11:101119. [PMID: 38523672 PMCID: PMC10958065 DOI: 10.1016/j.gendis.2023.101119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 06/11/2022] [Accepted: 06/04/2023] [Indexed: 03/26/2024] Open
Abstract
Diabetic kidney disease is a leading cause of end-stage renal disease, making it a global public health concern. The molecular mechanisms underlying diabetic kidney disease have not been elucidated due to its complex pathogenesis. Thus, exploring these mechanisms from new perspectives is the current focus of research concerning diabetic kidney disease. Ion channels are important proteins that maintain the physiological functions of cells and organs. Among ion channels, potassium channels stand out, because they are the most common and important channels on eukaryotic cell surfaces and function as the basis for cell excitability. Certain potassium channel abnormalities have been found to be closely related to diabetic kidney disease progression and genetic susceptibility, such as KATP, KCa, Kir, and KV. In this review, we summarized the roles of different types of potassium channels in the occurrence and development of diabetic kidney disease to discuss whether the development of DKD is due to potassium channel dysfunction and present new ideas for the treatment of DKD.
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Affiliation(s)
- Jia Guo
- Nephrology Research Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
- Key Laboratory of Precision Diagnosis and Treatment for Chronic Kidney Disease in Henan Province, Zhengzhou, Henan 450052, China
- Research Center for Kidney Disease, Zhengzhou, Henan 450052, China
| | - Chaojie Zhang
- Nephrology Research Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
- Key Laboratory of Precision Diagnosis and Treatment for Chronic Kidney Disease in Henan Province, Zhengzhou, Henan 450052, China
- Research Center for Kidney Disease, Zhengzhou, Henan 450052, China
| | - Hui Zhao
- Nephrology Research Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
- Key Laboratory of Precision Diagnosis and Treatment for Chronic Kidney Disease in Henan Province, Zhengzhou, Henan 450052, China
- Research Center for Kidney Disease, Zhengzhou, Henan 450052, China
| | - Yufan Yan
- Nephrology Research Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
- Key Laboratory of Precision Diagnosis and Treatment for Chronic Kidney Disease in Henan Province, Zhengzhou, Henan 450052, China
- Research Center for Kidney Disease, Zhengzhou, Henan 450052, China
| | - Zhangsuo Liu
- Nephrology Research Center, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
- Key Laboratory of Precision Diagnosis and Treatment for Chronic Kidney Disease in Henan Province, Zhengzhou, Henan 450052, China
- Research Center for Kidney Disease, Zhengzhou, Henan 450052, China
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Burd SG, Lebedeva AV, Rubleva YV, Pantina NV, Yurchenko AV, Bogomazova MA, Kovaleva II, Karchevskaya AE. [Epilepsy syndromes associated with hearing loss]. Zh Nevrol Psikhiatr Im S S Korsakova 2023; 123:28-33. [PMID: 36719116 DOI: 10.17116/jnevro202312301128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Patients with epilepsy who have also hearing loss represent a distinct group of patients, often with aggravated medical history, comorbidities and high potential for disability. The etiopathogenetic factors of epilepsy and hearing loss may be common to these conditions (neuroinfections, craniocerebral injuries, cerebral circulatory disorders, perinatal pathology, etc.). In addition, these two syndromes may occur as part of hereditary diseases, so their timely recognition and genetic diagnosis are important for determining further medical and genetic prognosis. This article provides an overview of orphan genetic diseases associated with epilepsy and hearing loss - MERRF syndrome, MELAS syndrome, EAST syndrome, Ayme-Grippsyndrome, epilepsy, hearing loss and mental retardation syndromes, associated with mutations in SPATA5 gene, DOOR syndrome, Gustavson syndrome.
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Affiliation(s)
- S G Burd
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia.,Pirogov Russian National Research Medical University, Moscow, Russia
| | - A V Lebedeva
- Pirogov Russian National Research Medical University, Moscow, Russia
| | - Yu V Rubleva
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
| | - N V Pantina
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
| | - A V Yurchenko
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
| | - M A Bogomazova
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
| | - I I Kovaleva
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
| | - A E Karchevskaya
- Federal Center of Brain Research and Neurotechnologies, Moscow, Russia
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Role of inwardly rectifying K+ channel 5.1 (Kir5.1) in the regulation of renal membrane transport. Curr Opin Nephrol Hypertens 2022; 31:479-485. [PMID: 35894283 DOI: 10.1097/mnh.0000000000000817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW Kir5.1 interacts with Kir4.2 in proximal tubule and with Kir4.1 in distal convoluted tubule (DCT), connecting tubule (CNT) and cortical collecting duct (CCD) to form basolateral-K+-channels. Kir4.2/Kir5.1 and Kir4.1/Kir5.1 play an important role in regulating Na+/HCO3--transport of the proximal tubule and Na+/K+ -transport in the DCT/CNT/CCD. The main focus of this review is to provide an overview of the recent development in the field regarding the role of Kir5.1 regulating renal electrolyte transport in the proximal tubule and DCT. RECENT FINDINGS Loss-of-function-mutations of KCNJ16 cause a new form of tubulopathy, characterized by hypokalaemia, Na+-wasting, acid-base-imbalance and metabolic-acidosis. Abnormal bicarbonate transport induced by loss-of-function of KCNJ16-mutants is recapitulated in Kir4.2-knockout-(Kir4.2 KO) mice. Deletion of Kir5.1 also abolishes the effect of dietary Na+ and K+-intakes on the basolateral membrane voltage and NCC expression/activity. Long-term high-salt intake or high-K+-intake causes hyperkalaemic in Kir5.1-deficient mice. SUMMARY Kir4.2/Kir5.1 activity in the proximal tubule plays a key role in regulating Na+, K+ and bicarbonate-transport through regulating electrogenic-Na+-bicarbonate-cotransporter-(NBCe1) and type 3-Na+/H+-exchanger-(NHE3). Kir4.1/Kir5.1 activity of the DCT plays a critical role in mediating the effect of dietary-K+ and Na+-intakes on NCC activity/expression. As NCC determines the Na+ delivery rate to the aldosterone-sensitive distal nephron (ASDN), defective regulation of NCC during high-salt and high-K+ compromises renal K+ excretion and K+ homeostasis.
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Wang WH, Lin DH. Inwardly rectifying K + channels 4.1 and 5.1 (Kir4.1/Kir5.1) in the renal distal nephron. Am J Physiol Cell Physiol 2022; 323:C277-C288. [PMID: 35759440 PMCID: PMC9291425 DOI: 10.1152/ajpcell.00096.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The inwardly rectifying potassium channel (Kir) 4.1 (encoded by KCNJ10) interacts with Kir5.1 (encoded by KCNJ16) to form a major basolateral K+ channel in the renal distal convoluted tubule (DCT), connecting tubule (CNT), and the cortical collecting duct (CCD). Kir4.1/Kir5.1 heterotetramer plays an important role in regulating Na+ and K+ transport in the DCT, CNT, and CCD. A recent development in the field has firmly established the role of Kir4.1/Kir5.1 heterotetramer of the DCT in the regulation of thiazide-sensitive Na-Cl cotransporter (NCC). Changes in Kir4.1/Kir5.1 activity of the DCT are an essential step for the regulation of NCC expression/activity induced by dietary K+ and Na+ intakes and play a role in modulating NCC by type 2 angiotensin II receptor (AT2R), bradykinin type II receptor (BK2R), and β-adrenergic receptor. Since NCC activity determines the Na+ delivery rate to the aldosterone-sensitive distal nephron (ASDN), a distal nephron segment from late DCT to CCD, Kir4.1/Kir5.1 activity plays a critical role not only in the regulation of renal Na+ absorption but also in modulating renal K+ excretion and maintaining K+ homeostasis. Thus, Kir4.1/Kir5.1 activity serves as an important component of renal K+ sensing mechanism. The main focus of this review is to provide an overview regarding the role of Kir4.1 and Kir5.1 of the DCT and CCD in the regulation of renal K+ excretion and Na+ absorption.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
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Lo J, Forst AL, Warth R, Zdebik AA. EAST/SeSAME Syndrome and Beyond: The Spectrum of Kir4.1- and Kir5.1-Associated Channelopathies. Front Physiol 2022; 13:852674. [PMID: 35370765 PMCID: PMC8965613 DOI: 10.3389/fphys.2022.852674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/08/2022] [Indexed: 12/13/2022] Open
Abstract
In 2009, two groups independently linked human mutations in the inwardly rectifying K+ channel Kir4.1 (gene name KCNJ10) to a syndrome affecting the central nervous system (CNS), hearing, and renal tubular salt reabsorption. The autosomal recessive syndrome has been named EAST (epilepsy, ataxia, sensorineural deafness, and renal tubulopathy) or SeSAME syndrome (seizures, sensorineural deafness, ataxia, intellectual disability, and electrolyte imbalance), accordingly. Renal dysfunction in EAST/SeSAME patients results in loss of Na+, K+, and Mg2+ with urine, activation of the renin-angiotensin-aldosterone system, and hypokalemic metabolic alkalosis. Kir4.1 is highly expressed in affected organs: the CNS, inner ear, and kidney. In the kidney, it mostly forms heteromeric channels with Kir5.1 (KCNJ16). Biallelic loss-of-function mutations of Kir5.1 can also have disease significance, but the clinical symptoms differ substantially from those of EAST/SeSAME syndrome: although sensorineural hearing loss and hypokalemia are replicated, there is no alkalosis, but rather acidosis of variable severity; in contrast to EAST/SeSAME syndrome, the CNS is unaffected. This review provides a framework for understanding some of these differences and will guide the reader through the growing literature on Kir4.1 and Kir5.1, discussing the complex disease mechanisms and the variable expression of disease symptoms from a molecular and systems physiology perspective. Knowledge of the pathophysiology of these diseases and their multifaceted clinical spectrum is an important prerequisite for making the correct diagnosis and forms the basis for personalized therapies.
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Affiliation(s)
- Jacky Lo
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Anna-Lena Forst
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Richard Warth
- Medical Cell Biology, Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Anselm A. Zdebik
- Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
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Abstract
The kidney maintains electrolyte, water, and acid-base balance, eliminates foreign and waste compounds, regulates blood pressure, and secretes hormones. There are at least 16 different highly specialized epithelial cell types in the mammalian kidney. The number of specialized endothelial cells, immune cells, and interstitial cell types might even be larger. The concerted interplay between different cell types is critical for kidney function. Traditionally, cells were defined by their function or microscopical morphological appearance. With the advent of new single-cell modalities such as transcriptomics, epigenetics, metabolomics, and proteomics we are entering into a new era of cell type definition. This new technological revolution provides new opportunities to classify cells in the kidney and understand their functions.
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Affiliation(s)
- Michael S Balzer
- Department of Medicine, Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
- Institute of Diabetes Obesity and Metabolism, University of Pennsylvania, Philadelphia, Philadelphia, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Katalin Susztak
- Department of Medicine, Renal Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
- Institute of Diabetes Obesity and Metabolism, University of Pennsylvania, Philadelphia, Philadelphia, USA
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Wieërs MLAJ, Mulder J, Rotmans JI, Hoorn EJ. Potassium and the kidney: a reciprocal relationship with clinical relevance. Pediatr Nephrol 2022; 37:2245-2254. [PMID: 35195759 PMCID: PMC9395506 DOI: 10.1007/s00467-022-05494-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/02/2022] [Accepted: 02/02/2022] [Indexed: 10/26/2022]
Abstract
By controlling urinary potassium excretion, the kidneys play a key role in maintaining whole-body potassium homeostasis. Conversely, low urinary potassium excretion (as a proxy for insufficient dietary intake) is increasingly recognized as a risk factor for the progression of kidney disease. Thus, there is a reciprocal relationship between potassium and the kidney: the kidney regulates potassium balance but potassium also affects kidney function. This review explores this relationship by discussing new insights into kidney potassium handling derived from recently characterized tubulopathies and studies on sexual dimorphism. These insights reveal a central but non-exclusive role for the distal convoluted tubule in sensing potassium and subsequently modifying the activity of the sodium-chloride cotransporter. This is another example of reciprocity: activation of the sodium-chloride cotransporter not only reduces distal sodium delivery and therefore potassium secretion but also increases salt sensitivity. This mechanism helps explain the well-known relationship between dietary potassium and blood pressure. Remarkably, in children, blood pressure is related to dietary potassium but not sodium intake. To explore how potassium deficiency can cause kidney injury, we review the mechanisms of hypokalemic nephropathy and discuss if these mechanisms may explain the association between low dietary potassium intake and adverse kidney outcomes. We discuss if potassium should be repleted in patients with kidney disease and what role dietary potassium plays in the risk of hyperkalemia. Supported by data and physiology, we reach the conclusion that we should view potassium not only as a potentially dangerous cation but also as a companion in the battle against kidney disease.
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Affiliation(s)
- Michiel L. A. J. Wieërs
- grid.5645.2000000040459992XDepartment of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Room Ns403, PO Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Jaap Mulder
- grid.5645.2000000040459992XDepartment of Pediatrics, Division of Pediatric Nephrology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands ,grid.10419.3d0000000089452978Department of Pediatrics, Division of Pediatric Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Joris I. Rotmans
- grid.10419.3d0000000089452978Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ewout J. Hoorn
- grid.5645.2000000040459992XDepartment of Internal Medicine, Division of Nephrology and Transplantation, Erasmus Medical Center, University Medical Center Rotterdam, Room Ns403, PO Box 2040, 3000 CA Rotterdam, The Netherlands
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Claverie-Martin F, Perdomo-Ramirez A, Garcia-Nieto V. Hereditary kidney diseases associated with hypomagnesemia. Kidney Res Clin Pract 2021; 40:512-526. [PMID: 34784661 PMCID: PMC8685365 DOI: 10.23876/j.krcp.21.112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 06/20/2021] [Indexed: 11/04/2022] Open
Abstract
In the kidney, a set of proteins expressed in the epithelial cells of the thick ascending loop of Henle and the distal convoluted tubule directly or indirectly play important roles in the regulation of serum magnesium levels. Magnesium reabsorption in the thick ascending loop of Henle occurs through a passive paracellular pathway, while in the distal convoluted tubule, the final magnesium concentration is established through an active transcellular pathway. The players involved in magnesium reabsorption include proteins with diverse functions including tight junction proteins, cation and anion channels, sodium chloride cotransporter, calcium-sensing receptor, epidermal growth factor, cyclin M2, sodium potassium adenosine triphosphatase subunits, transcription factors, a serine protease, and proteins involved in mitochondrial function. Mutations in the genes that encode these proteins impair their function and cause different rare diseases associated with hypomagnesemia, which may lead to muscle cramps, fatigue, epileptic seizures, intellectual disability, cardiac arrhythmias, and chronic kidney disease. The purpose of this review is to describe the clinical and genetic characteristics of these hereditary kidney diseases and the current research findings on the pathophysiological basis of these diseases.
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Affiliation(s)
- Felix Claverie-Martin
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Ana Perdomo-Ramirez
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Victor Garcia-Nieto
- Unidad de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
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Abstract
Magnesium (Mg2+) plays an essential role in many biological processes. Mg2+ deficiency is therefore associated with a wide range of clinical effects including muscle cramps, fatigue, seizures and arrhythmias. To maintain sufficient Mg2+ levels, (re)absorption of Mg2+ in the intestine and kidney is tightly regulated. Genetic defects that disturb Mg2+ uptake pathways, as well as drugs interfering with Mg2+ (re)absorption cause hypomagnesemia. The aim of this review is to provide an overview of the molecular mechanisms underlying genetic and drug-induced Mg2+ deficiencies. This leads to the identification of four main mechanisms that are affected by hypomagnesemia-causing mutations or drugs: luminal transient receptor potential melastatin type 6/7-mediated Mg2+ uptake, paracellular Mg2+ reabsorption in the thick ascending limb of Henle's loop, structural integrity of the distal convoluted tubule and Na+-dependent Mg2+ extrusion driven by the Na+/K+-ATPase. Our analysis demonstrates that genetic and drug-induced causes of hypomagnesemia share common molecular mechanisms. Targeting these shared pathways can lead to novel treatment options for patients with hypomagnesemia.
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Wang J, Wang C, Xu N, Liu ZF, Pang DW, Zhang ZL. A virus-induced kidney disease model based on organ-on-a-chip: Pathogenesis exploration of virus-related renal dysfunctions. Biomaterials 2019; 219:119367. [PMID: 31344514 DOI: 10.1016/j.biomaterials.2019.119367] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 07/13/2019] [Accepted: 07/14/2019] [Indexed: 02/03/2023]
Abstract
Renal dysfunctions usually happen in viral infections and many viruses specially infect distal renal tubules, however the pathogenesis remains unknown. Here, in order to explore the pathogenesis of virus-related renal dysfunctions, a Pseudorabies Virus (PrV) induced kidney disease model was built on a distal tubule-on-a-chip (DTC), for the first time. The barrier structure and Na reabsorption of distal renal tubules were successfully reconstituted in DTCs. After PrV infection, results showed electrolyte regulation dysfunction in Na reabsorption for the disordered Na transporters, the broken reabsorption barrier, and the transformed microvilli. And it would lead to virus induced serum electrolyte abnormalities. This work brought us a new cognition about the advantages of organ-on-a-chip (OOC) in virus research, for it had given us a better insight into the pathogenesis of virus induced dysfunctions, based on its unique ability in function reproduction.
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Affiliation(s)
- Ji Wang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China
| | - Cheng Wang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China
| | - Na Xu
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China
| | - Zheng-Fei Liu
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Dai-Wen Pang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China
| | - Zhi-Ling Zhang
- Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, and State Key Laboratory of Virology, Wuhan University, Wuhan 430072, PR China.
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11
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The interplay of renal potassium and sodium handling in blood pressure regulation: critical role of the WNK-SPAK-NCC pathway. J Hum Hypertens 2019; 33:508-523. [DOI: 10.1038/s41371-019-0170-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 12/18/2018] [Accepted: 01/03/2019] [Indexed: 12/19/2022]
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12
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Teulon J, Planelles G, Sepúlveda FV, Andrini O, Lourdel S, Paulais M. Renal Chloride Channels in Relation to Sodium Chloride Transport. Compr Physiol 2018; 9:301-342. [DOI: 10.1002/cphy.c180024] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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13
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Celmina M, Micule I, Inashkina I, Audere M, Kuske S, Pereca J, Stavusis J, Pelnena D, Strautmanis J. EAST/SeSAME syndrome: Review of the literature and introduction of four new Latvian patients. Clin Genet 2018; 95:63-78. [PMID: 29722015 DOI: 10.1111/cge.13374] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 04/12/2018] [Accepted: 04/23/2018] [Indexed: 11/28/2022]
Abstract
EAST (Epilepsy, Ataxia, Sensorineural deafness, Tubulopathy) or SeSAME (Seizures, Sensorineural deafness, Ataxia, Mental retardation, and Electrolyte imbalance) syndrome is a rare autosomal recessive syndrome first described in 2009 independently by Bockenhauer and Scholl. It is caused by mutations in KCNJ10, which encodes Kir4.1, an inwardly rectifying K+ channel found in the brain, inner ear, kidney and eye. To date, 16 mutations and at least 28 patients have been reported. In this paper, we review mutations causing EAST/SeSAME syndrome, clinical manifestations in detail, and efficacy of treatment in previously reported patients. We also report a new Latvian kindred with 4 patients. In contrast to the majority of previous reports, we found a progressive course of the disorder in terms of hearing impairment and neurologic deficit. The treatment is based on antiepileptic drugs, electrolyte replacement, hearing aids and mobility devices. Future research should concentrate on recognizing the lesions in the central nervous system to evaluate new potential diagnostic criteria and on formally evaluating intellectual disability.
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Affiliation(s)
- M Celmina
- Clinic for Pediatrics, Children's Clinical University Hospital, Riga, Latvia.,Faculty of Continuing Education, University of Latvia, Riga, Latvia
| | - I Micule
- Clinic for Medical Genetics and Prenatal Diagnostics, Children's Clinical University Hospital, Riga, Latvia
| | - I Inashkina
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - M Audere
- ENT Department, Children's Clinical University Hospital, Riga, Latvia
| | - S Kuske
- Latvian Children's Hearing Center, Riga, Latvia
| | - J Pereca
- Emergency Department, Royal Infirmary of Edinburg, Edinburgh, United Kingdom
| | - J Stavusis
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - D Pelnena
- Latvian Biomedical Research and Study Center, Riga, Latvia
| | - J Strautmanis
- Clinic for Pediatric Neurology and Neurosurgery, Children's Clinical University Hospital, Riga, Latvia
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15
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Viering DHHM, de Baaij JHF, Walsh SB, Kleta R, Bockenhauer D. Genetic causes of hypomagnesemia, a clinical overview. Pediatr Nephrol 2017; 32:1123-1135. [PMID: 27234911 PMCID: PMC5440500 DOI: 10.1007/s00467-016-3416-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/02/2016] [Accepted: 05/04/2016] [Indexed: 12/16/2022]
Abstract
Magnesium is essential to the proper functioning of numerous cellular processes. Magnesium ion (Mg2+) deficits, as reflected in hypomagnesemia, can cause neuromuscular irritability, seizures and cardiac arrhythmias. With normal Mg2+ intake, homeostasis is maintained primarily through the regulated reabsorption of Mg2+ by the thick ascending limb of Henle's loop and distal convoluted tubule of the kidney. Inadequate reabsorption results in renal Mg2+ wasting, as evidenced by an inappropriately high fractional Mg2+ excretion. Familial renal Mg2+ wasting is suggestive of a genetic cause, and subsequent studies in these hypomagnesemic families have revealed over a dozen genes directly or indirectly involved in Mg2+ transport. Those can be classified into four groups: hypercalciuric hypomagnesemias (encompassing mutations in CLDN16, CLDN19, CASR, CLCNKB), Gitelman-like hypomagnesemias (CLCNKB, SLC12A3, BSND, KCNJ10, FYXD2, HNF1B, PCBD1), mitochondrial hypomagnesemias (SARS2, MT-TI, Kearns-Sayre syndrome) and other hypomagnesemias (TRPM6, CNMM2, EGF, EGFR, KCNA1, FAM111A). Although identification of these genes has not yet changed treatment, which remains Mg2+ supplementation, it has contributed enormously to our understanding of Mg2+ transport and renal function. In this review, we discuss general mechanisms and symptoms of genetic causes of hypomagnesemia as well as the specific molecular mechanisms and clinical phenotypes associated with each syndrome.
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Affiliation(s)
- Daan H H M Viering
- Centre for Nephrology, University College London, London, UK
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Jeroen H F de Baaij
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Stephen B Walsh
- Centre for Nephrology, University College London, London, UK
| | - Robert Kleta
- Centre for Nephrology, University College London, London, UK.
- Paediatric Nephrology, Great Ormond Street Hospital, London, UK.
| | - Detlef Bockenhauer
- Centre for Nephrology, University College London, London, UK
- Paediatric Nephrology, Great Ormond Street Hospital, London, UK
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16
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Kompatscher A, de Baaij JHF, Aboudehen K, Hoefnagels APWM, Igarashi P, Bindels RJM, Veenstra GJC, Hoenderop JGJ. Loss of transcriptional activation of the potassium channel Kir5.1 by HNF1β drives autosomal dominant tubulointerstitial kidney disease. Kidney Int 2017; 92:1145-1156. [PMID: 28577853 DOI: 10.1016/j.kint.2017.03.034] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 03/08/2017] [Accepted: 03/23/2017] [Indexed: 12/20/2022]
Abstract
Hepatocyte nuclear factor 1 homeobox B (HNF1β) is an essential transcription factor for the development and functioning of the kidney. Mutations in HNF1β cause autosomal dominant tubulointerstitial kidney disease characterized by renal cysts and maturity-onset diabetes of the young (MODY). Moreover, these patients suffer from a severe electrolyte phenotype consisting of hypomagnesemia and hypokalemia. Until now, genes that are regulated by HNF1β are only partially known and do not fully explain the phenotype of the patients. Therefore, we performed chIP-seq in the immortalized mouse kidney cell line mpkDCT to identify HNF1β binding sites on a genome-wide scale. In total 7,421 HNF1β-binding sites were identified, including several genes involved in electrolyte transport and diabetes. A highly specific and conserved HNF1β site was identified in the promoter of Kcnj16 that encodes the potassium channel Kir5.1. Luciferase-promoter assays showed a 2.2-fold increase in Kcnj16 expression when HNF1β was present. Expression of the Hnf1β p.Lys156Glu mutant, previously identified in a patient with autosomal dominant tubulointerstitial kidney disease, did not activate Kcnj16 expression. Knockdown of Hnf1β in mpkDCT cells significantly reduced the appearance of Kcnj16 (Kir5.1) and Kcnj10 (Kir4.1) by 38% and 37%, respectively. These results were confirmed in a HNF1β renal knockout mouse which exhibited downregulation of Kcnj16, Kcnj10 and Slc12a3 transcripts in the kidney by 78%, 83% and 76%, respectively, compared to HNF1β wild-type mice. Thus, HNF1β is a transcriptional activator of Kcnj16. Hence, patients with HNF1β mutations may have reduced Kir5.1 activity in the kidney, resulting in hypokalemia and hypomagnesemia.
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Affiliation(s)
- Andreas Kompatscher
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Jeroen H F de Baaij
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Karam Aboudehen
- Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Anke P W M Hoefnagels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Peter Igarashi
- Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, Netherlands
| | - Gertjan J C Veenstra
- Department of Molecular Developmental Biology, Radboud Institute for Molecular Life Sciences, Radboud University, Nijmegen, Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, Netherlands.
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17
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Abstract
PURPOSE OF REVIEW Magnesium (Mg) imbalances are frequently overlooked. Hypermagnesemia usually occurs in preeclamptic women after Mg therapy or in end-stage renal disease patients, whereas hypomagnesemia is more common with a prevalence of up to 15% in the general population. Increasing evidence points toward a role for mild-to-moderate chronic hypomagnesemia in the pathogenesis of hypertension, type 2 diabetes mellitus, and metabolic syndrome. RECENT FINDINGS The kidneys are the major regulator of total body Mg homeostasis. Over the last decade, the identification of the responsible genes in rare genetic disorders has enhanced our understanding of how the kidney handles Mg. The different genetic disorders and medications contributing to abnormal Mg homeostasis are reviewed. SUMMARY As dysfunctional Mg homeostasis contributes to the development of many common human disorders, serum Mg deserves closer monitoring. Hypomagnesemic patients may be asymptomatic or may have mild symptoms. In severe hypomagnesemia, patients may present with neurological symptoms such as seizures, spasms, or cramps. Renal symptoms include nephrocalcinosis and impaired renal function. Most conditions affect tubular Mg reabsorption by disturbing the lumen-positive potential in the thick ascending limb or the negative membrane potential in the distal convoluted tubule.
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Cuevas CA, Su XT, Wang MX, Terker AS, Lin DH, McCormick JA, Yang CL, Ellison DH, Wang WH. Potassium Sensing by Renal Distal Tubules Requires Kir4.1. J Am Soc Nephrol 2017; 28:1814-1825. [PMID: 28052988 DOI: 10.1681/asn.2016090935] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 11/23/2016] [Indexed: 11/03/2022] Open
Abstract
The mammalian distal convoluted tubule (DCT) makes an important contribution to potassium homeostasis by modulating NaCl transport. The thiazide-sensitive Na+/Cl- cotransporter (NCC) is activated by low potassium intake and by hypokalemia. Coupled with suppression of aldosterone secretion, activation of NCC helps to retain potassium by increasing electroneutral NaCl reabsorption, therefore reducing Na+/K+ exchange. Yet the mechanisms by which DCT cells sense plasma potassium concentration and transmit the information to the apical membrane are not clear. Here, we tested the hypothesis that the potassium channel Kir4.1 is the potassium sensor of DCT cells. We generated mice in which Kir4.1 could be deleted in the kidney after the mice are fully developed. Deletion of Kir4.1 in these mice led to moderate salt wasting, low BP, and profound potassium wasting. Basolateral membranes of DCT cells were depolarized, nearly devoid of conductive potassium transport, and unresponsive to plasma potassium concentration. Although renal WNK4 abundance increased after Kir4.1 deletion, NCC abundance and function decreased, suggesting that membrane depolarization uncouples WNK kinases from NCC. Together, these results indicate that Kir4.1 mediates potassium sensing by DCT cells and couples this signal to apical transport processes.
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Affiliation(s)
- Catherina A Cuevas
- Division of Nephrology and Hypertension, Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Ming-Xiao Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - Andrew S Terker
- Division of Nephrology and Hypertension, Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
| | - James A McCormick
- Division of Nephrology and Hypertension, Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon
| | - Chao-Ling Yang
- Division of Nephrology and Hypertension, Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon.,Renal Section, Veterans Administration Portland Health Care System, Portland, Oregon
| | - David H Ellison
- Division of Nephrology and Hypertension, Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon; .,Renal Section, Veterans Administration Portland Health Care System, Portland, Oregon
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York; and
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Penton D, Czogalla J, Wengi A, Himmerkus N, Loffing-Cueni D, Carrel M, Rajaram RD, Staub O, Bleich M, Schweda F, Loffing J. Extracellular K + rapidly controls NaCl cotransporter phosphorylation in the native distal convoluted tubule by Cl - -dependent and independent mechanisms. J Physiol 2016; 594:6319-6331. [PMID: 27457700 DOI: 10.1113/jp272504] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/14/2016] [Indexed: 12/12/2022] Open
Abstract
KEY POINTS High dietary potassium (K+ ) intake dephosphorylates and inactivates the NaCl cotransporter (NCC) in the renal distal convoluted tubule (DCT). Using several ex vivo models, we show that physiological changes in extracellular K+ , similar to those occurring after a K+ rich diet, are sufficient to promote a very rapid dephosphorylation of NCC in native DCT cells. Although the increase of NCC phosphorylation upon decreased extracellular K+ appears to depend on cellular Cl- fluxes, the rapid NCC dephosphorylation in response to increased extracellular K+ is not Cl- -dependent. The Cl- -dependent pathway involves the SPAK/OSR1 kinases, whereas the Cl- independent pathway may include additional signalling cascades. ABSTRACT A high dietary potassium (K+ ) intake causes a rapid dephosphorylation, and hence inactivation, of the thiazide-sensitive NaCl cotransporter (NCC) in the renal distal convoluted tubule (DCT). Based on experiments in heterologous expression systems, it was proposed that changes in extracellular K+ concentration ([K+ ]ex ) modulate NCC phosphorylation via a Cl- -dependent modulation of the with no lysine (K) kinases (WNK)-STE20/SPS-1-44 related proline-alanine-rich protein kinase (SPAK)/oxidative stress-related kinase (OSR1) kinase pathway. We used the isolated perfused mouse kidney technique and ex vivo preparations of mouse kidney slices to test the physiological relevance of this model on native DCT. We demonstrate that NCC phosphorylation inversely correlates with [K+ ]ex , with the most prominent effects occurring around physiological plasma [K+ ]. Cellular Cl- conductances and the kinases SPAK/OSR1 are involved in the phosphorylation of NCC under low [K+ ]ex . However, NCC dephosphorylation triggered by high [K+ ]ex is neither blocked by removing extracellular Cl- , nor by the Cl- channel blocker 4,4'-diisothiocyano-2,2'-stilbenedisulphonic acid. The response to [K+ ]ex on a low extracellular chloride concentration is also independent of significant changes in SPAK/OSR1 phosphorylation. Thus, in the native DCT, [K+ ]ex directly and rapidly controls NCC phosphorylation by Cl- -dependent and independent pathways that involve the kinases SPAK/OSR1 and a yet unidentified additional signalling mechanism.
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Affiliation(s)
- David Penton
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Swiss National Centre of Competence in Research 'Kidney Control of Homeostasis', University of Zurich, Zurich, Switzerland
| | - Jan Czogalla
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Swiss National Centre of Competence in Research 'Kidney Control of Homeostasis', University of Zurich, Zurich, Switzerland
| | - Agnieszka Wengi
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Nina Himmerkus
- Institute of Physiology, Christian-Albrecht University, Kiel, Germany
| | | | - Monique Carrel
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Renuga Devi Rajaram
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Swiss National Centre of Competence in Research 'Kidney Control of Homeostasis', University of Zurich, Zurich, Switzerland
| | - Olivier Staub
- Department of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.,Swiss National Centre of Competence in Research 'Kidney Control of Homeostasis', University of Zurich, Zurich, Switzerland
| | - Markus Bleich
- Institute of Physiology, Christian-Albrecht University, Kiel, Germany
| | - Frank Schweda
- Institute of Physiology, University of Regensburg, Regensburg, Germany
| | - Johannes Loffing
- Institute of Anatomy, University of Zurich, Zurich, Switzerland. .,Swiss National Centre of Competence in Research 'Kidney Control of Homeostasis', University of Zurich, Zurich, Switzerland.
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20
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Wang WH. Basolateral Kir4.1 activity in the distal convoluted tubule regulates K secretion by determining NaCl cotransporter activity. Curr Opin Nephrol Hypertens 2016; 25:429-35. [PMID: 27306796 PMCID: PMC4974141 DOI: 10.1097/mnh.0000000000000248] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE OF REVIEW Renal potassium (K) secretion plays a key role in maintaining K homeostasis. The classic mechanism of renal K secretion is focused on the connecting tubule and cortical collecting duct, in which K is uptaken by basolateral Na-K-ATPase and is secreted into the lumen by apical ROMK (Kir1.1) and Ca-activated big conductance K channel. Recently, genetic studies and animal models have indicated that inwardly rectifying K channel 4.1 (Kir4.1 or Kcnj10) in the distal convoluted tubule (DCT) may play a role in the regulation of K secretion in the aldosterone-sensitive distal nephron by targeting the NaCl cotransporter (NCC). This review summarizes recent progresses regarding the role of Kir4.1 in the regulation of NCC and K secretion. RECENT FINDINGS Kir4.1 is expressed in the basolateral membrane of the DCT, and plays a predominant role in contributing to the basolateral K conductance and in participating in the generation of negative membrane potential. Kir4.1 is also the substrate of src-family tyrosine kinase and the stimulation of src-family tyrosine kinase activates Kir4.1 activity in the DCT. The genetic deletion or functional inhibition of Kir4.1 depolarizes the membrane of the DCT, inhibits ste20-proline-alanine rich kinase, and suppresses NCC activity. Moreover, the downregulation of Kir4.1 increases epithelial Na channel expression in the collecting duct and urinary K excretion. Finally, mice with low Kir4.1 activity in the DCT are hypomagnesemia and hypokalemia. SUMMARY Recent progress in exploring the regulation and the function of Kir4.1 in the DCT strongly indicates that Kir4.1plays an important role in initiating the regulation of renal K secretion by targeting NCC and it may serves as a K sensor in the kidney.
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Affiliation(s)
- Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York, USA
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21
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Abdelhadi O, Iancu D, Tekman M, Stanescu H, Bockenhauer D, Kleta R. Founder mutation in KCNJ10 in Pakistani patients with EAST syndrome. Mol Genet Genomic Med 2016; 4:521-6. [PMID: 27652280 PMCID: PMC5023937 DOI: 10.1002/mgg3.227] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/11/2022] Open
Abstract
Background EAST syndrome is an autosomal recessive disorder caused by loss‐of‐function mutations in the gene KCNJ10. Among the 14 pathogenic mutations described so far, the p.R65P mutation stands out as the most frequent one and is particularly associated with patients of Pakistani origin. As a result we aimed to establish the existence of a potential founder effect in the Pakistani population. Methods To this end, we genotyped 12 patients from seven families and we compared disease haplotypes with ethnically matched control chromosomes. This haplotype was used together with demographic data for Pakistan to estimate the age of this founder mutation. Results We identified a small homozygous 0.694 Mb region around the KCNJ10 p.R65P mutation that had identical haplotypes in all of the patients which were completely absent in the control sample. Based on current demographic data and knowledge about disease frequency, we estimate that this particular p.R65P mutation arose 20 generations (about 500 years) ago. Conclusion By knowing the prevalent mutation in a given population more efficient diagnostics can be performed and the families can benefit from specific counseling.
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Affiliation(s)
- Ola Abdelhadi
- Centre for Nephrology University College London London UK
| | - Daniela Iancu
- Centre for Nephrology University College London London UK
| | - Mehmet Tekman
- Centre for Nephrology University College London London UK
| | - Horia Stanescu
- Centre for Nephrology University College London London UK
| | | | - Robert Kleta
- Centre for Nephrology University College London London UK
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22
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Abdelhadi O, Iancu D, Stanescu H, Kleta R, Bockenhauer D. EAST syndrome: Clinical, pathophysiological, and genetic aspects of mutations in KCNJ10. Rare Dis 2016; 4:e1195043. [PMID: 27500072 PMCID: PMC4961265 DOI: 10.1080/21675511.2016.1195043] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 11/04/2022] Open
Abstract
EAST syndrome is a recently described autosomal recessive disorder secondary to mutations in KCNJ10 (Kir4.1), a gene encoding a potassium channel expressed in the brain, eye, ear and kidney. This condition is characterized by 4 cardinal features; Epilepsy, Ataxia, Sensorineural deafness, and (a renal salt-wasting) Tubulopathy, hence the acronym EAST syndrome. Here we review reported clinical manifestations, in particular the neurological signs and symptoms which typically have the most impact on the quality of life of patients. In addition we review the pathophysiology and genetic aspects of the disease. So far 14 different KCNJ10 mutations have been published which either directly affect channel function or may lead to mislocalisation. Investigations of the pathophysiology may provide clues to potential treatments.
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Affiliation(s)
- Ola Abdelhadi
- Center for Nephrology, University College London, London, UK
| | - Daniela Iancu
- Center for Nephrology, University College London, London, UK
| | - Horia Stanescu
- Center for Nephrology, University College London, London, UK
| | - Robert Kleta
- Center for Nephrology, University College London, London, UK
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23
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Fan L, Wang X, Zhang D, Duan X, Zhao C, Zu M, Meng X, Zhang C, Su XT, Wang MX, Wang WH, Gu R. Vasopressin-induced stimulation of the Na(+)-activated K(+) channels is responsible for maintaining the basolateral K(+) conductance of the thick ascending limb (TAL) in EAST/SeSAME syndrome. Biochim Biophys Acta Mol Basis Dis 2015; 1852:2554-62. [PMID: 26319417 DOI: 10.1016/j.bbadis.2015.08.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 08/07/2015] [Accepted: 08/25/2015] [Indexed: 11/29/2022]
Abstract
The renal phenotype of EAST syndrome, a disease caused by the loss-of-function-mutations of Kcnj10 (Kir4.1), is a reminiscence of Gitelman's syndrome characterized by the defective function in the distal convoluted tubule (DCT). The aim of the present study is to test whether antidiuretic hormone (vasopressin)-induced stimulation of the Na(+)-activated 80-150pS K(+) channel is responsible for compensating the lost function of Kcnj10 in the thick ascending limb (TAL) of subjects with EAST syndrome. Immunostaining and western blot showed that the expression of aquaporin 2 (AQP2) was significantly higher in Kcnj10(-/-) mice than those of WT littermates, suggesting that the disruption of Kcnj10 stimulates vasopressin response in the kidney. The role of vasopressin in stimulating the basolateral K(+) conductance of the TAL was strongly indicated by the finding that the application of arginine-vasopressin (AVP) hyperpolarized the membrane in the TAL of Kcnj10(-/-) mice. Application of AVP significantly stimulated the 80-150pS K(+) channel in the TAL and this effect was blocked by tolvaptan (V2 receptor antagonist) or by inhibiting PKA. Moreover, the water restriction for 24h significantly increased the probability of finding the 80-150pS K(+) channel and the K(+) channel open probability in the TAL. The application of a membrane permeable cAMP analog also mimicked the effect of AVP and activated this K(+) channel, suggesting that cAMP-PKA pathway stimulates the 80-150pS K(+) channels. The role of the basolateral K(+) conductance in maintaining transcellular Cl(-) transport is further suggested by the finding that the inhibition of basolateral K(+) channels significantly diminished the AVP-induced stimulation of the basolateral 10pS Cl(-) channels. We conclude that vasopressin stimulates the 80-150pS K(+) channel in the TAL via a cAMP-dependent mechanism. The vasopressin-induced stimulation of K(+) channels is responsible for compensating lost function of Kcnj10 thereby rescuing the basolateral K(+) conductance which is essential for the transport function in the TAL.
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Affiliation(s)
- Lili Fan
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Xiaoyan Wang
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Dandan Zhang
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Xinpeng Duan
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Chunlei Zhao
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Mingxue Zu
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Xinxin Meng
- Department of Physiology, Harbin Medical University, Harbin, China
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, United States
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, United States
| | - Ming-Xiao Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, United States
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, United States.
| | - Ruimin Gu
- Department of Physiology, Harbin Medical University, Harbin, China.
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24
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Zhang C, Wang L, Su XT, Lin DH, Wang WH. KCNJ10 (Kir4.1) is expressed in the basolateral membrane of the cortical thick ascending limb. Am J Physiol Renal Physiol 2015; 308:F1288-96. [PMID: 25834074 DOI: 10.1152/ajprenal.00687.2014] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 03/29/2015] [Indexed: 11/22/2022] Open
Abstract
The aim of the present study is to examine the role of Kcnj10 (Kir.4.1) in contributing to the basolateral K conductance in the cortical thick ascending limb (cTAL) using Kcnj10(+/+) wild-type (WT) and Kcnj10(-/-) knockout (KO) mice. The patch-clamp experiments detected a 40- and an 80-pS K channel in the basolateral membrane of the cTAL. Moreover, the probability of finding the 40-pS K was significantly higher in the late part of the cTAL close to the distal convoluted tubule than those in the initial part. Immunostaining showed that Kcnj10 staining was detected in the basolateral membrane of the cTAL but the expression was not uniformly distributed. The disruption of Kcnj10 completely eliminated the 40-pS K channel but not the 80-pS K channel, suggesting the role of Kcnj10 in forming the 40-pS K channel of the cTAL. Also, the disruption of Kcnj10 increased the probability of finding the 80-pS K channel in the cTAL, especially in the late part of the cTAL. Because the channel open probability of the 80-pS K channel in KO was similar to those of WT mice, the increase in the 80-pS K channel may be achieved by increasing K channel number. The whole cell recording further showed that K reversal potential measured with 5 mM K in the bath and 140 mM K in the pipette was the same in the WT and KO mice. Moreover, Western blot and immunostaining showed that the disruption of Kcnj10 did not affect the expression of Na-K-Cl cotransporter 2 (NKCC2). We conclude that Kir.4.1 is expressed in the basolateral membrane of cTAL and that the disruption of Kir.4.1 has no significant effect on the membrane potential of the cTAL and NKCC2 expression.
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Affiliation(s)
- Chengbiao Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou, Jiangsu, China; and Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Lijun Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, New York
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York
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25
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Cheng CJ, Sung CC, Huang CL, Lin SH. Inward-rectifying potassium channelopathies: new insights into disorders of sodium and potassium homeostasis. Pediatr Nephrol 2015; 30:373-83. [PMID: 24899236 DOI: 10.1007/s00467-014-2764-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/11/2013] [Accepted: 01/10/2014] [Indexed: 11/30/2022]
Abstract
Inward-rectifying potassium (Kir) channels allow more inward than outward potassium flux when channels are open in mammalian cells. At physiological resting membrane potentials, however, they predominantly mediate outward potassium flux and play important roles in regulating the resting membrane potential in diverse cell types and potassium secretion in the kidneys. Mutations of Kir channels cause human hereditary diseases collectively called Kir channelopathies, many of which are characterized by disorders of sodium and potassium homeostasis. Studies on these genetic Kir channelopathies have shed light on novel pathophysiological mechanisms, including renal sodium and potassium handling, potassium shifting in skeletal muscles, and aldosterone production in the adrenal glands. Here, we review several recent advances in Kir channels and their clinical implications in sodium and potassium homeostasis.
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Affiliation(s)
- Chih-Jen Cheng
- Department of Medicine, Division of Nephrology, Tri-Service General Hospital, National Defense Medical Center, No. 325, Section 2, Cheng-Kung Road, Neihu 114, Taipei, Taiwan
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de Baaij JHF, Hoenderop JGJ, Bindels RJM. Magnesium in man: implications for health and disease. Physiol Rev 2015; 95:1-46. [PMID: 25540137 DOI: 10.1152/physrev.00012.2014] [Citation(s) in RCA: 870] [Impact Index Per Article: 96.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Magnesium (Mg(2+)) is an essential ion to the human body, playing an instrumental role in supporting and sustaining health and life. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Although Mg(2+) availability has been proven to be disturbed during several clinical situations, serum Mg(2+) values are not generally determined in patients. This review aims to provide an overview of the function of Mg(2+) in human health and disease. In short, Mg(2+) plays an important physiological role particularly in the brain, heart, and skeletal muscles. Moreover, Mg(2+) supplementation has been shown to be beneficial in treatment of, among others, preeclampsia, migraine, depression, coronary artery disease, and asthma. Over the last decade, several hereditary forms of hypomagnesemia have been deciphered, including mutations in transient receptor potential melastatin type 6 (TRPM6), claudin 16, and cyclin M2 (CNNM2). Recently, mutations in Mg(2+) transporter 1 (MagT1) were linked to T-cell deficiency underlining the important role of Mg(2+) in cell viability. Moreover, hypomagnesemia can be the consequence of the use of certain types of drugs, such as diuretics, epidermal growth factor receptor inhibitors, calcineurin inhibitors, and proton pump inhibitors. This review provides an extensive and comprehensive overview of Mg(2+) research over the last few decades, focusing on the regulation of Mg(2+) homeostasis in the intestine, kidney, and bone and disturbances which may result in hypomagnesemia.
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Affiliation(s)
- Jeroen H F de Baaij
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
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27
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Sepúlveda FV, Pablo Cid L, Teulon J, Niemeyer MI. Molecular aspects of structure, gating, and physiology of pH-sensitive background K2P and Kir K+-transport channels. Physiol Rev 2015; 95:179-217. [PMID: 25540142 DOI: 10.1152/physrev.00016.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
K(+) channels fulfill roles spanning from the control of excitability to the regulation of transepithelial transport. Here we review two groups of K(+) channels, pH-regulated K2P channels and the transport group of Kir channels. After considering advances in the molecular aspects of their gating based on structural and functional studies, we examine their participation in certain chosen physiological and pathophysiological scenarios. Crystal structures of K2P and Kir channels reveal rather unique features with important consequences for the gating mechanisms. Important tasks of these channels are discussed in kidney physiology and disease, K(+) homeostasis in the brain by Kir channel-equipped glia, and central functions in the hearing mechanism in the inner ear and in acid secretion by parietal cells in the stomach. K2P channels fulfill a crucial part in central chemoreception probably by virtue of their pH sensitivity and are central to adrenal secretion of aldosterone. Finally, some unorthodox behaviors of the selectivity filters of K2P channels might explain their normal and pathological functions. Although a great deal has been learned about structure, molecular details of gating, and physiological functions of K2P and Kir K(+)-transport channels, this has been only scratching at the surface. More molecular and animal studies are clearly needed to deepen our knowledge.
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Affiliation(s)
- Francisco V Sepúlveda
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - L Pablo Cid
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - Jacques Teulon
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - María Isabel Niemeyer
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
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28
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Penton D, Czogalla J, Loffing J. Dietary potassium and the renal control of salt balance and blood pressure. Pflugers Arch 2015; 467:513-30. [PMID: 25559844 DOI: 10.1007/s00424-014-1673-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 01/09/2023]
Abstract
Dietary potassium (K(+)) intake has antihypertensive effects, prevents strokes, and improves cardiovascular outcomes. The underlying mechanism for these beneficial effects of high K(+) diets may include vasodilation, enhanced urine flow, reduced renal renin release, and negative sodium (Na(+)) balance. Indeed, several studies demonstrate that dietary K(+) intake induces renal Na(+) loss despite elevated plasma aldosterone. This review briefly highlights the epidemiological and experimental evidences for the effects of dietary K(+) on arterial blood pressure. It discusses the pivotal role of the renal distal tubule for the regulation of urinary K(+) and Na(+) excretion and blood pressure and highlights that it depends on the coordinated interaction of different nephron portions, epithelial cell types, and various ion channels, transporters, and ATPases. Moreover, we discuss the relevance of aldosterone and aldosterone-independent factors in mediating the effects of an altered K(+) intake on renal K(+) and Na(+) handling. Particular focus is given to findings suggesting that an aldosterone-independent downregulation of the thiazide-sensitive NaCl cotransporter significantly contributes to the natriuretic and antihypertensive effect of a K(+)-rich diet. Last but not least, we refer to the complex signaling pathways enabling the kidney to adapt its function to the homeostatic needs in response to an altered K(+) intake. Future work will have to further address the underlying cellular and molecular mechanism and to elucidate, among others, how an altered dietary K(+) intake is sensed and how this signal is transmitted to the different epithelial cells lining the distal tubule.
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Affiliation(s)
- David Penton
- Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
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29
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Terker AS, Zhang C, McCormick JA, Lazelle RA, Zhang C, Meermeier NP, Siler DA, Park HJ, Fu Y, Cohen DM, Weinstein AM, Wang WH, Yang CL, Ellison DH. Potassium modulates electrolyte balance and blood pressure through effects on distal cell voltage and chloride. Cell Metab 2015; 21:39-50. [PMID: 25565204 PMCID: PMC4332769 DOI: 10.1016/j.cmet.2014.12.006] [Citation(s) in RCA: 325] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 10/13/2014] [Accepted: 12/13/2014] [Indexed: 10/24/2022]
Abstract
Dietary potassium deficiency, common in modern diets, raises blood pressure and enhances salt sensitivity. Potassium homeostasis requires a molecular switch in the distal convoluted tubule (DCT), which fails in familial hyperkalemic hypertension (pseudohypoaldosteronism type 2), activating the thiazide-sensitive NaCl cotransporter, NCC. Here, we show that dietary potassium deficiency activates NCC, even in the setting of high salt intake, thereby causing sodium retention and a rise in blood pressure. The effect is dependent on plasma potassium, which modulates DCT cell membrane voltage and, in turn, intracellular chloride. Low intracellular chloride stimulates WNK kinases to activate NCC, limiting potassium losses, even at the expense of increased blood pressure. These data show that DCT cells, like adrenal cells, sense potassium via membrane voltage. In the DCT, hyperpolarization activates NCC via WNK kinases, whereas in the adrenal gland, it inhibits aldosterone secretion. These effects work in concert to maintain potassium homeostasis.
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MESH Headings
- Animals
- Blood Pressure/drug effects
- Cell Line
- Chlorides/metabolism
- Electrolytes/urine
- Humans
- Kidney Tubules, Distal/metabolism
- Membrane Potentials/drug effects
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Minor Histocompatibility Antigens
- Potassium/blood
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium, Dietary/pharmacology
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Pseudohypoaldosteronism/metabolism
- Pseudohypoaldosteronism/pathology
- Sodium Chloride, Dietary/pharmacology
- Solute Carrier Family 12, Member 3/deficiency
- Solute Carrier Family 12, Member 3/genetics
- Solute Carrier Family 12, Member 3/metabolism
- WNK Lysine-Deficient Protein Kinase 1
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Affiliation(s)
- Andrew S Terker
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Chong Zhang
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA; Department of Nephrology, Xinhua Hostpital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092, China
| | - James A McCormick
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Rebecca A Lazelle
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Chengbiao Zhang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA
| | - Nicholas P Meermeier
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Dominic A Siler
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Hae J Park
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Yi Fu
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - David M Cohen
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA; VA Portland Health Care System, Portland, OR 97239, USA
| | - Alan M Weinstein
- Department of Physiology and Biophysics, Weil Medical College, New York, NY 10065, USA
| | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA
| | - Chao-Ling Yang
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA; VA Portland Health Care System, Portland, OR 97239, USA
| | - David H Ellison
- Division of Nephrology & Hypertension, Department of Medicine, Oregon Health & Science University, Portland, OR 97239, USA; VA Portland Health Care System, Portland, OR 97239, USA.
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30
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Abstract
The distal convoluted tubule (DCT) is a short nephron segment, interposed between the macula densa and collecting duct. Even though it is short, it plays a key role in regulating extracellular fluid volume and electrolyte homeostasis. DCT cells are rich in mitochondria, and possess the highest density of Na+/K+-ATPase along the nephron, where it is expressed on the highly amplified basolateral membranes. DCT cells are largely water impermeable, and reabsorb sodium and chloride across the apical membrane via electroneurtral pathways. Prominent among this is the thiazide-sensitive sodium chloride cotransporter, target of widely used diuretic drugs. These cells also play a key role in magnesium reabsorption, which occurs predominantly, via a transient receptor potential channel (TRPM6). Human genetic diseases in which DCT function is perturbed have provided critical insights into the physiological role of the DCT, and how transport is regulated. These include Familial Hyperkalemic Hypertension, the salt-wasting diseases Gitelman syndrome and EAST syndrome, and hereditary hypomagnesemias. The DCT is also established as an important target for the hormones angiotensin II and aldosterone; it also appears to respond to sympathetic-nerve stimulation and changes in plasma potassium. Here, we discuss what is currently known about DCT physiology. Early studies that determined transport rates of ions by the DCT are described, as are the channels and transporters expressed along the DCT with the advent of molecular cloning. Regulation of expression and activity of these channels and transporters is also described; particular emphasis is placed on the contribution of genetic forms of DCT dysregulation to our understanding.
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Affiliation(s)
- James A McCormick
- Division of Nephrology & Hypertension, Oregon Health & Science University, & VA Medical Center, Portland, Oregon, United States
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31
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Luft FC. Clinical salt deficits. Pflugers Arch 2014; 467:559-63. [PMID: 25471347 DOI: 10.1007/s00424-014-1643-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 10/30/2014] [Indexed: 11/25/2022]
Abstract
Salt retention or salt deficit has a bearing on the body fluid volume. Both states are clinically difficult to recognize and quantitate. Salt deficit is particularly cumbersome in that regard since orthostatic blood pressure, heart rate changes, and simple physical inspection are inaccurate and unreliable. Salt deficit can be acute such as after hemorrhage or massive diarrhea, or more chronic as observed in Addison's disease, failure of renal sodium chloride transporters, drug-related effects, or distal nephron disease. Molecular genetics has given us important new insights into salt deficit syndromes. Recent recognition of a novel sodium storage compartment involving sodium binding to proteoglycans adds to the overall complexity of these syndromes.
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Affiliation(s)
- Friedrich C Luft
- Experimental and Clinical Research Center, a joint cooperation between the Max-Delbrück Center for Molecular Medicine and the Charité Medical Faculty, Lindenbergerweg 80, 13125, Berlin, Germany,
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32
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Konrad M, Schlingmann KP. Inherited disorders of renal hypomagnesaemia. Nephrol Dial Transplant 2014; 29 Suppl 4:iv63-71. [PMID: 25165187 DOI: 10.1093/ndt/gfu198] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The kidney plays a key role in the maintenance of normal magnesium balance. The distal tubule of the kidney, namely the thick ascending limb of the loop of Henle and the distal convoluted tubule, is crucial for the regulation of serum magnesium levels and body magnesium content. The identification of molecular defects related to rare inherited magnesium losing disorders has contributed greatly to a better understanding of the process of renal magnesium handling. Since the number of genetic defects related to magnesium metabolism is still increasing, it might be expected that our knowledge on magnesium physiology will further improve. This knowledge will hopefully lead to therapeutic strategies that enable specific therapies for patients suffering from the symptoms and possible sequelae of chronic magnesium depletion.
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Affiliation(s)
- Martin Konrad
- Department of General Pediatrics, University Children's Hospital, Münster, Germany
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33
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Zhang C, Wang L, Zhang J, Su XT, Lin DH, Scholl UI, Giebisch G, Lifton RP, Wang WH. KCNJ10 determines the expression of the apical Na-Cl cotransporter (NCC) in the early distal convoluted tubule (DCT1). Proc Natl Acad Sci U S A 2014; 111:11864-9. [PMID: 25071208 PMCID: PMC4136599 DOI: 10.1073/pnas.1411705111] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The renal phenotype induced by loss-of-function mutations of inwardly rectifying potassium channel (Kir), Kcnj10 (Kir4.1), includes salt wasting, hypomagnesemia, metabolic alkalosis and hypokalemia. However, the mechanism by which Kir.4.1 mutations cause the tubulopathy is not completely understood. Here we demonstrate that Kcnj10 is a main contributor to the basolateral K conductance in the early distal convoluted tubule (DCT1) and determines the expression of the apical Na-Cl cotransporter (NCC) in the DCT. Immunostaining demonstrated Kcnj10 and Kcnj16 were expressed in the basolateral membrane of DCT, and patch-clamp studies detected a 40-pS K channel in the basolateral membrane of the DCT1 of p8/p10 wild-type Kcnj10(+/+) mice (WT). This 40-pS K channel is absent in homozygous Kcnj10(-/-) (knockout) mice. The disruption of Kcnj10 almost completely eliminated the basolateral K conductance and decreased the negativity of the cell membrane potential in DCT1. Moreover, the lack of Kcnj10 decreased the basolateral Cl conductance, inhibited the expression of Ste20-related proline-alanine-rich kinase and diminished the apical NCC expression in DCT. We conclude that Kcnj10 plays a dominant role in determining the basolateral K conductance and membrane potential of DCT1 and that the basolateral K channel activity in the DCT determines the apical NCC expression possibly through a Ste20-related proline-alanine-rich kinase-dependent mechanism.
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Affiliation(s)
- Chengbiao Zhang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical College, Xuzhou 221002, China;Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Lijun Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Junhui Zhang
- Department of Genetics, Howard Hughes Medical Institute, and
| | - Xiao-Tong Su
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Dao-Hong Lin
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
| | - Ute I Scholl
- Department of Genetics, Howard Hughes Medical Institute, and
| | - Gerhard Giebisch
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510
| | | | - Wen-Hui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595; and
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34
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Bollepalli MK, Fowler PW, Rapedius M, Shang L, Sansom MSP, Tucker SJ, Baukrowitz T. State-dependent network connectivity determines gating in a K+ channel. Structure 2014; 22:1037-46. [PMID: 24980796 PMCID: PMC4087272 DOI: 10.1016/j.str.2014.04.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/05/2014] [Accepted: 04/07/2014] [Indexed: 12/31/2022]
Abstract
X-ray crystallography has provided tremendous insight into the different structural states of membrane proteins and, in particular, of ion channels. However, the molecular forces that determine the thermodynamic stability of a particular state are poorly understood. Here we analyze the different X-ray structures of an inwardly rectifying potassium channel (Kir1.1) in relation to functional data we obtained for over 190 mutants in Kir1.1. This mutagenic perturbation analysis uncovered an extensive, state-dependent network of physically interacting residues that stabilizes the pre-open and open states of the channel, but fragments upon channel closure. We demonstrate that this gating network is an important structural determinant of the thermodynamic stability of these different gating states and determines the impact of individual mutations on channel function. These results have important implications for our understanding of not only K+ channel gating but also the more general nature of conformational transitions that occur in other allosteric proteins. Functional validation of different crystallographic states of Kir channels Presence of a state-dependent gating network revealed by large-scale mutagenesis Biased effect of mutations on Kir channel gating due to open-state destabilization Long-range allosteric coupling mediated by a physically connected residue network
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Affiliation(s)
- Murali K Bollepalli
- Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany
| | - Philip W Fowler
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Markus Rapedius
- Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany
| | - Lijun Shang
- Clarendon Laboratory, Department of Physics, University of Oxford Oxford, OX1 3PU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Ion Channel Initiative, University of Oxford, Oxford OX1 3PT, UK
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford Oxford, OX1 3PU, UK; OXION Ion Channel Initiative, University of Oxford, Oxford OX1 3PT, UK.
| | - Thomas Baukrowitz
- Physiological Institute, Christian-Albrechts University, 24118 Kiel, Germany.
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35
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Abstract
The distal convoluted tubule is the nephron segment that lies immediately downstream of the macula densa. Although short in length, the distal convoluted tubule plays a critical role in sodium, potassium, and divalent cation homeostasis. Recent genetic and physiologic studies have greatly expanded our understanding of how the distal convoluted tubule regulates these processes at the molecular level. This article provides an update on the distal convoluted tubule, highlighting concepts and pathophysiology relevant to clinical practice.
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Affiliation(s)
- Arohan R Subramanya
- Departments of Medicine and Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, Pennsylvania;
| | - David H Ellison
- Departments of Medicine and Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon; and Portland Veterans Affairs Medical Center, Portland, Oregon
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36
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Gilliam D, O'Brien DP, Coates JR, Johnson GS, Johnson GC, Mhlanga-Mutangadura T, Hansen L, Taylor JF, Schnabel RD. A homozygous KCNJ10 mutation in Jack Russell Terriers and related breeds with spinocerebellar ataxia with myokymia, seizures, or both. J Vet Intern Med 2014; 28:871-7. [PMID: 24708069 PMCID: PMC4238845 DOI: 10.1111/jvim.12355] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 02/14/2014] [Accepted: 03/03/2014] [Indexed: 12/21/2022] Open
Abstract
Background Juvenile‐onset spinocerebellar ataxia has been recognized in Jack Russell Terriers and related Russell group terriers (RGTs) for over 40 years. Ataxia occurs with varying combinations of myokymia, seizures, and other signs of neurologic disease. More than 1 form of the disease has been suspected. Hypothesis/Objectives The objective was to identify the mutation causing the spinocerebellar ataxia associated with myokymia, seizures, or both and distinguish the phenotype from other ataxias in the RGTs. Animals DNA samples from 16 RGTs with spinocerebellar ataxia beginning from 2 to 12 months of age, 640 control RGTs, and 383 dogs from 144 other breeds along with the medical records of affected dogs were studied. Methods This case‐control study compared the frequencies of a KCNJ10 allele in RGTs with spinocerebellar ataxia versus control RGTs. This allele was identified in a whole‐genome sequence of a single RGT with spinocerebellar ataxia and myokymia by comparison to whole‐genome sequences from 81 other canids that were normal or had other diseases. Results A missense mutation in the gene coding for the inwardly rectifying potassium channel Kir4.1 (KCNJ10:c.627C>G) was significantly (P < .001) associated with the disease. Dogs homozygous for the mutant allele all had spinocerebellar ataxia with varying combinations of myokymia and seizures. Conclusions and Clinical Importance Identification of the KCNJ10 mutation in dogs with spinocerebellar ataxia with myokymia, seizures, or both clarifies the multiple forms of ataxia seen in these breeds and provides a DNA test to identify carriers.
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Affiliation(s)
- D Gilliam
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO
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37
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Abstract
Specific channels permit movement of selected ions through cellular membranes, and are of vital importance in a number of physiological processes, particularly in excitable tissues such as nerve and muscle, but also in endocrine organs and in epithelial biology. Disorders of channel proteins are termed channelopathies, and their importance is increasingly recognised within medicine. In the kidney, ion channels have critical roles enabling sodium and potassium reuptake or excretion along the nephron, in magnesium homeostasis, in the control of water reabsorption in the collecting duct, and in determining glomerular permeability. In this review, we assess the channelopathies encountered in each nephron segment, and see how their molecular and genetic characterisation in the past 20–30 years has furthered our understanding of normal kidney physiology and disease processes, aids correct diagnosis and promises future therapeutic opportunities.
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Affiliation(s)
- KW Loudon
- Department of Renal Medicine, Addenbrooke’s Hospital, Cambridge, UK
| | - AC Fry
- Department of Renal Medicine, Addenbrooke’s Hospital, Cambridge, UK
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38
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Tian C, Zhu R, Zhu L, Qiu T, Cao Z, Kang T. Potassium Channels: Structures, Diseases, and Modulators. Chem Biol Drug Des 2013; 83:1-26. [DOI: 10.1111/cbdd.12237] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Chuan Tian
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
| | - Ruixin Zhu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Lixin Zhu
- Department of Pediatrics; Digestive Diseases and Nutrition Center; The State University of New York at Buffalo; Buffalo NY 14226 USA
| | - Tianyi Qiu
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Zhiwei Cao
- School of Life Sciences and Technology; Tongji University; Shanghai 200092 China
| | - Tingguo Kang
- School of Pharmacy; Liaoning University of Traditional Chinese Medicine; Dalian Liaoning 116600 China
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39
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Schmidt K, Ripper M, Tegtmeier I, Humberg E, Sterner C, Reichold M, Warth R, Bandulik S. Dynamics of Renal Electrolyte Excretion in Growing Mice. ACTA ACUST UNITED AC 2013; 124:7-13. [DOI: 10.1159/000356816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 10/25/2013] [Indexed: 11/19/2022]
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40
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Zdebik AA, Mahmood F, Stanescu HC, Kleta R, Bockenhauer D, Russell C. Epilepsy in kcnj10 morphant zebrafish assessed with a novel method for long-term EEG recordings. PLoS One 2013; 8:e79765. [PMID: 24244558 PMCID: PMC3828195 DOI: 10.1371/journal.pone.0079765] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 09/30/2013] [Indexed: 11/18/2022] Open
Abstract
We aimed to develop and validate a reliable method for stable long-term recordings of EEG activity in zebrafish, which is less prone to artifacts than current invasive techniques. EEG activity was recorded with a blunt electrolyte-filled glass pipette placed on the zebrafish head mimicking surface EEG technology in man. In addition, paralysis of agarose-embedded fish using D-tubocurarine excluded movement artifacts associated with epileptic activity. This non-invasive recording technique allowed recordings for up to one hour and produced less artifacts than impaling the zebrafish optic tectum with a patch pipette. Paralyzed fish survived, and normal heartbeat could be monitored for over 1h. Our technique allowed the demonstration of specific epileptic activity in kcnj10a morphant fish (a model for EAST syndrome) closely resembling epileptic activity induced by pentylenetetrazol. This new method documented that seizures in the zebrafish EAST model were ameliorated by pentobarbitone, but not diazepam, validating its usefulness. In conclusion, non-invasive recordings in paralyzed EAST syndrome zebrafish proved stable, reliable and robust, showing qualitatively similar frequency spectra to those obtained from pentylenetetrazol-treated fish. This technique may prove particularly useful in zebrafish epilepsy models that show infrequent or conditional seizure activity.
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Affiliation(s)
- Anselm A. Zdebik
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
- * E-mail:
| | - Fahad Mahmood
- Department of Comparative Biological Sciences, Royal Veterinary College, London, United Kingdom
| | - Horia C. Stanescu
- Centre for Nephrology, University College London, London, United Kingdom
| | - Robert Kleta
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Centre for Nephrology, University College London, London, United Kingdom
- Institute of Child Health, University College London, London, United Kingdom
| | - Detlef Bockenhauer
- Centre for Nephrology, University College London, London, United Kingdom
- Institute of Child Health, University College London, London, United Kingdom
| | - Claire Russell
- Department of Comparative Biological Sciences, Royal Veterinary College, London, United Kingdom
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41
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Stivaros S. How the imaging investigation of EAST syndrome points towards the future of radiological multi-parametric phenotyping of a genetic disease. Dev Med Child Neurol 2013; 55:783-4. [PMID: 23924081 DOI: 10.1111/dmcn.12189] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stavros Stivaros
- Royal Manchester Children's Hospital, Academic Department of Paediatric Neuroradiology & The University of Manchester, UK
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42
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Cross JH, Arora R, Heckemann RA, Gunny R, Chong K, Carr L, Baldeweg T, Differ AM, Lench N, Varadkar S, Sirimanna T, Wassmer E, Hulton SA, Ognjanovic M, Ramesh V, Feather S, Kleta R, Hammers A, Bockenhauer D. Neurological features of epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome. Dev Med Child Neurol 2013; 55:846-56. [PMID: 23924083 PMCID: PMC4298033 DOI: 10.1111/dmcn.12171] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/14/2013] [Indexed: 01/30/2023]
Abstract
AIM Recently, we reported a previously unrecognized symptom constellation comprising epilepsy, ataxia, sensorineural deafness, and tubulopathy (EAST syndrome) associated with recessive mutations in the KCNJ10 gene. Here, we provide a detailed characterization of the clinical features of the syndrome to aid patient management with respect to diagnosis, prognostic counselling, and identification of best treatment modalities. METHOD We conducted a retrospective review of the detailed neurological and neuroradiological features of nine children (four females, five males; age range at last examination 6-20y) with genetically proven EAST syndrome. RESULTS All children presented with tonic-clonic seizures in infancy. Later, non-progressive, cerebellar ataxia and hearing loss were noted. Whilst seizures mostly responded well to treatment, ataxia proved to be the most debilitating feature, with three patients non-ambulant. All available magnetic resonance imaging (MRI) revealed subtle symmetrical signal changes in the cerebellar dentate nuclei. Moreover, four patients had a small corpus callosum and brainstem hypoplasia, and three had a small spinal cord. Regional quantitative volumetric analysis of the images confirmed the corpus callosum and brainstem hypoplasia and showed further patterns of variation from the norm. INTERPRETATION The neurological features of EAST syndrome appear to be non-progressive, which is important for prognostic counselling. The spectrum of EAST syndrome includes consistent abnormalities on brain MRI, which may aid diagnosis. Further longitudinal documentation is required to determine the true natural history of the disorder.
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Affiliation(s)
- J Helen Cross
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child Health, London, UK.
| | - Ruchi Arora
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | | | - Roxana Gunny
- Department of Radiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Kling Chong
- Department of Radiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Lucinda Carr
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Torsten Baldeweg
- Developmental Cognitive Neuroscience Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Ann-Marie Differ
- Department of Molecular Genetics, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Nicholas Lench
- Department of Molecular Genetics, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Sophie Varadkar
- Neurosciences Unit, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Tony Sirimanna
- Department of Audiology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | | | | | | | | | - Sally Feather
- Leeds Teaching Hospitals/University of LeedsLeeds, UK
| | - Robert Kleta
- Department of Nephrology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
| | - Alexander Hammers
- The Neurodis FoundationLyon, France,Division of Experimental Medicine, Imperial College LondonLondon, UK
| | - Detlef Bockenhauer
- Department of Nephrology, Great Ormond Street Hospital for Children NHS Trust and UCL-Institute of Child HealthLondon, UK
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43
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Disorders of calcium and magnesium balance: a physiology-based approach. Pediatr Nephrol 2013; 28:1195-206. [PMID: 23142866 DOI: 10.1007/s00467-012-2350-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/02/2012] [Accepted: 10/08/2012] [Indexed: 01/20/2023]
Abstract
Disorders of calcium and magnesium balance are physiologically interesting and clinically challenging. In this review, we attempt to bridge the gap between physiology and practice by providing a physiology-based approach to understanding hypocalcemia, hypercalcemia and hypomagnesemia. Calcium and, to a lesser extent, magnesium balance is achieved through a complex interplay between the parathyroid gland, bone, the intestine and the kidney. Our understanding of the molecular physiology of calcium and magnesium balance has grown considerably following the discovery of the calcium-sensing receptor (CaSR) and the main intestinal and renal transporters for calcium and magnesium, namely, the transient receptor potential channels TRPV5, TRPV6 and TRPM6. The regulation of parathyroid hormone (PTH) secretion by CaSR and the subsequent effects of PTH and vitamin D on TRPV5 constitute an increasingly characterized regulatory loop. In contrast, no truly magnesiotropic hormones have been identified, although the recently established interactions between the epidermal growth factor and TRPM6 suggest a possible candidate. Overall, the aim of this review is to illustrate the clinical disorders of calcium and magnesium balance from the perspective of their integrated physiology.
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44
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Tyler Miller R. Control of renal calcium, phosphate, electrolyte, and water excretion by the calcium-sensing receptor. Best Pract Res Clin Endocrinol Metab 2013; 27:345-58. [PMID: 23856264 DOI: 10.1016/j.beem.2013.04.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Through regulation of excretion, the kidney shares responsibility for the metabolic balance of calcium (Ca(2+)) with several other tissues including the GI tract and bone. The balances of Ca(2+) and phosphate (PO4), magnesium (Mg(2+)), sodium (Na(+)), potassium (K(+)), chloride (Cl(-)), and water (H2O) are linked via regulatory systems with overlapping effects and are also controlled by systems specific to each of them. Cloning of the calcium-sensing receptor (CaSR) along with the recognition that mutations in the CaSR gene are responsible for two familial syndromes characterized by abnormalities in the regulation of PTH secretion and Ca(2+) metabolism (Familial Hypocalciuric Hypercalcemia, FHH, and Autosomal Dominant Hypocalcemia, ADH) made it clear that extracellular Ca(2+) (Ca(2+)o) participates in its own regulation via a specific, receptor-mediated mechanism. Demonstration that the CaSR is expressed in the kidney as well as the parathyroid glands combined with more complete characterizations of FHH and ADH established that the effects of elevated Ca(2+) on the kidney (wasting of Na(+), K(+), Cl(-), Ca(2+), Mg(2+) and H2O) are attributable to activation of the CaSR. The advent of positive and negative allosteric modulators of the CaSR along with mouse models with global or tissue-selective deletion of the CaSR in the kidney have allowed a better understanding of the functions of the CaSR in various nephron segments. The biology of the CaSR is more complicated than originally thought and difficult to define precisely owing to the limitations of reagents such as anti-CaSR antibodies and the difficulties inherent in separating direct effects of Ca(2+) on the kidney mediated by the CaSR from associated CaSR-induced changes in PTH. Nevertheless, renal CaSRs have nephron-specific effects that contribute to regulating Ca(2+) in the circulation and urine in a manner that assures a narrow range of Ca(2+)o in the blood and avoids excessively high concentrations of Ca(2+) in the urine.
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Affiliation(s)
- R Tyler Miller
- Department of Medicine and Nephrology, University of Texas Southwestern Medical Center and Chief of Medicine Service, VA North Texas Health System, 5323 Harry Hines Blvd, Dallas, TX 75390, USA.
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45
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Mahmood F, Mozere M, Zdebik AA, Stanescu HC, Tobin J, Beales PL, Kleta R, Bockenhauer D, Russell C. Generation and validation of a zebrafish model of EAST (epilepsy, ataxia, sensorineural deafness and tubulopathy) syndrome. Dis Model Mech 2013; 6:652-60. [PMID: 23471908 PMCID: PMC3634649 DOI: 10.1242/dmm.009480] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recessive mutations in KCNJ10, which encodes an inwardly rectifying potassium channel, were recently identified as the cause of EAST syndrome, a severe and disabling multi-organ disorder consisting of epilepsy, ataxia, sensorineural deafness and tubulopathy that becomes clinically apparent with seizures in infancy. A Kcnj10 knockout mouse shows postnatal mortality and is therefore not suitable for drug discovery. Because zebrafish are ideal for in vivo screening for potential therapeutics, we tested whether kcnj10 knockdown in zebrafish would fill this need. We cloned zebrafish kcnj10 and demonstrated that its function is equivalent to that of human KCNJ10. We next injected splice- and translation-blocking kcnj10 antisense morpholino oligonucleotides and reproduced the cardinal symptoms of EAST syndrome – ataxia, epilepsy and renal tubular defects. Several of these phenotypes could be assayed in an automated manner. We could rescue the morphant phenotype with complementary RNA (cRNA) encoding human wild-type KCNJ10, but not with cRNA encoding a KCNJ10 mutation identified in individuals with EAST syndrome. Our results suggest that zebrafish will be a valuable tool to screen for compounds that are potentially therapeutic for EAST syndrome or its individual symptoms. Knockdown of kcnj10 represents the first zebrafish model of a salt-losing tubulopathy, which has relevance for blood pressure control.
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Affiliation(s)
- Fahad Mahmood
- Department of Comparative Biomedical Sciences, Royal Veterinary College, London, UK
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46
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Scholl UI, Dave HB, Lu M, Farhi A, Nelson-Williams C, Listman JA, Lifton RP. SeSAME/EAST syndrome--phenotypic variability and delayed activity of the distal convoluted tubule. Pediatr Nephrol 2012; 27:2081-2090. [PMID: 22907601 DOI: 10.1007/s00467-012-2219-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 05/09/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND Mutations in the K(+) channel KCNJ10 (Kir4.1) cause an autosomal recessive syndrome featuring seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME). Kir4.1 localizes to the basolateral membrane of the renal distal convoluted tubule, and its loss of function mimics renal features of Gitelman syndrome, with hypokalemic alkalosis, hypomagnesemia, and hypocalciuria. Presentation early in life due to seizures provides an opportunity to investigate the development of the electrolyte defect with age. METHODS We used DNA sequencing, electrophysiology, confocal imaging, and biochemistry to identify a new KCNJ10 mutation in a previously unreported family and determine its impact on channel function. We examined medical records to follow the development of electrolyte disorders with age. RESULTS The four affected members were all homozygous for a novel T57I mutation that confers biochemical loss-of-function. Electrolytes in affected children were normal in the first years of life but showed significant worsening with age, resulting in clinically significant defects at age 5-8 years. Similar findings were seen in other SeSAME patients. CONCLUSIONS These findings provide evidence for a delayed activity of salt reabsorption by the distal convoluted tubule and suggest an explanation for the delayed clinical presentation of subjects with Gitelman syndrome.
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Affiliation(s)
- Ute I Scholl
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Haatal B Dave
- Department of Pediatrics, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Ming Lu
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Anita Farhi
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - Carol Nelson-Williams
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA
| | - James A Listman
- Department of Pediatrics, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY, 13210, USA
| | - Richard P Lifton
- Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06510, USA. .,Departments of Genetics and Internal Medicine, Howard Hughes Medical Institute, Yale University School of Medicine, 333 Cedar St., SHM I308, New Haven, CT, 06510, USA.
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47
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Hamilton KL, Devor DC. Basolateral membrane K+ channels in renal epithelial cells. Am J Physiol Renal Physiol 2012; 302:F1069-81. [PMID: 22338089 DOI: 10.1152/ajprenal.00646.2011] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The major function of epithelial tissues is to maintain proper ion, solute, and water homeostasis. The tubule of the renal nephron has an amazingly simple structure, lined by epithelial cells, yet the segments (i.e., proximal tubule vs. collecting duct) of the nephron have unique transport functions. The functional differences are because epithelial cells are polarized and thus possess different patterns (distributions) of membrane transport proteins in the apical and basolateral membranes of the cell. K(+) channels play critical roles in normal physiology. Over 90 different genes for K(+) channels have been identified in the human genome. Epithelial K(+) channels can be located within either or both the apical and basolateral membranes of the cell. One of the primary functions of basolateral K(+) channels is to recycle K(+) across the basolateral membrane for proper function of the Na(+)-K(+)-ATPase, among other functions. Mutations of these channels can cause significant disease. The focus of this review is to provide an overview of the basolateral K(+) channels of the nephron, providing potential physiological functions and pathophysiology of these channels, where appropriate. We have taken a "K(+) channel gene family" approach in presenting the representative basolateral K(+) channels of the nephron. The basolateral K(+) channels of the renal epithelia are represented by members of the KCNK, KCNJ, KCNQ, KCNE, and SLO gene families.
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Affiliation(s)
- Kirk L Hamilton
- Department of Physiology, Otago School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
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48
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Freudenthal B, Kulaveerasingam D, Lingappa L, Shah MA, Brueton L, Wassmer E, Ognjanovic M, Dorison N, Reichold M, Bockenhauer D, Kleta R, Zdebik AA. KCNJ10 mutations disrupt function in patients with EAST syndrome. Nephron Clin Pract 2011; 119:p40-8. [PMID: 21849804 DOI: 10.1159/000330250] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Accepted: 06/17/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS Mutations in the inwardly-rectifying K+ channel KCNJ10/Kir4.1 cause an autosomal recessive disorder characterized by epilepsy, ataxia, sensorineural deafness and tubulopathy (EAST syndrome). KCNJ10 is expressed in the kidney distal convoluted tubule, cochlear stria vascularis and brain glial cells. Patients clinically diagnosed with EAST syndrome were genotyped to identify and study mutations in KCNJ10. METHODS Patient DNA was sequenced and new mutations identified. Mutant and wild-type KCNJ10 constructs were cloned and heterologously expressed in Xenopus oocytes. Whole-cell K+ currents were measured by two-electrode voltage clamping. RESULTS Three new mutations in KCNJ10 (p.R65C, p.F75L and p.V259fs259X) were identified, and mutation p.R297C, previously only seen in a compound heterozygous patient, was found in a homozygous state. Wild-type human KCNJ10-expressing oocytes showed strongly inwardly-rectified currents, which by comparison were significantly reduced in all the mutants (p < 0.001). Specific inhibition of KCNJ10 currents by Ba2+ demonstrated residual function in all mutant channels (p < 0.05) but V259X. CONCLUSION This study confirms that EAST syndrome can be caused by many different mutations in KCNJ10 that significantly reduce K+ conductance. EAST syndrome should be considered in any patient with a renal Gitelman-like phenotype with additional neurological signs and symptoms like ataxia, epilepsy or sensorineural deafness.
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Affiliation(s)
- Bernard Freudenthal
- Centre for Nephrology, University College London, Royal Free Hospital, London, UK
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49
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Paulais M, Bloch-Faure M, Picard N, Jacques T, Ramakrishnan SK, Keck M, Sohet F, Eladari D, Houillier P, Lourdel S, Teulon J, Tucker SJ. Renal phenotype in mice lacking the Kir5.1 (Kcnj16) K+ channel subunit contrasts with that observed in SeSAME/EAST syndrome. Proc Natl Acad Sci U S A 2011; 108:10361-6. [PMID: 21633011 PMCID: PMC3121827 DOI: 10.1073/pnas.1101400108] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The heteromeric inwardly rectifying Kir4.1/Kir5.1 K(+) channel underlies the basolateral K(+) conductance in the distal nephron and is extremely sensitive to inhibition by intracellular pH. The functional importance of Kir4.1/Kir5.1 in renal ion transport has recently been highlighted by mutations in the human Kir4.1 gene (KCNJ10) that result in seizures, sensorineural deafness, ataxia, mental retardation, and electrolyte imbalance (SeSAME)/epilepsy, ataxia, sensorineural deafness, and renal tubulopathy (EAST) syndrome, a complex disorder that includes salt wasting and hypokalemic alkalosis. Here, we investigated the role of the Kir5.1 subunit in mice with a targeted disruption of the Kir5.1 gene (Kcnj16). The Kir5.1(-/-) mice displayed hypokalemic, hyperchloremic metabolic acidosis with hypercalciuria. The short-term responses to hydrochlorothiazide, an inhibitor of ion transport in the distal convoluted tubule (DCT), were also exaggerated, indicating excessive renal Na(+) absorption in this segment. Furthermore, chronic treatment with hydrochlorothiazide normalized urinary excretion of Na(+) and Ca(2+), and abolished acidosis in Kir5.1(-/-) mice. Finally, in contrast to WT mice, electrophysiological recording of K(+) channels in the DCT basolateral membrane of Kir5.1(-/-) mice revealed that, even though Kir5.1 is absent, there is an increased K(+) conductance caused by the decreased pH sensitivity of the remaining homomeric Kir4.1 channels. In conclusion, disruption of Kcnj16 induces a severe renal phenotype that, apart from hypokalemia, is the opposite of the phenotype seen in SeSAME/EAST syndrome. These results highlight the important role that Kir5.1 plays as a pH-sensitive regulator of salt transport in the DCT, and the implication of these results for the correct genetic diagnosis of renal tubulopathies is discussed.
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Affiliation(s)
- Marc Paulais
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - May Bloch-Faure
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Nicolas Picard
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Thibaut Jacques
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
- Faculty of Medicine, Université Paris–Descartes, 75006 Paris, France
| | - Suresh Krishna Ramakrishnan
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Mathilde Keck
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Fabien Sohet
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Dominique Eladari
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
- Faculty of Medicine, Université Paris–Descartes, 75006 Paris, France
- Assistance Publique–Hôpitaux de Paris, Hôpital Européen Georges Pompidou, 75015 Paris, France; and
| | - Pascal Houillier
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
- Faculty of Medicine, Université Paris–Descartes, 75006 Paris, France
- Assistance Publique–Hôpitaux de Paris, Hôpital Européen Georges Pompidou, 75015 Paris, France; and
| | - Stéphane Lourdel
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Jacques Teulon
- Université Pierre et Marie Curie Paris 6, Université Paris 5, and Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche en Santé 872, 75006 Paris, France
- Centre National de la Recherche Scientifique, Équipes de Recherche Labellisées 7226, Genomics Physiology, and Renal Physiopathology Laboratory, Centre de Recherche des Cordeliers, 75270 Paris 6, France
| | - Stephen J. Tucker
- Clarendon Laboratory and Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
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