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Marcoux AA, Tremblay LE, Slimani S, Fiola MJ, Mac-Way F, Garneau AP, Isenring P. Molecular characteristics and physiological roles of Na + -K + -Cl - cotransporter 2. J Cell Physiol 2020; 236:1712-1729. [PMID: 32776569 PMCID: PMC7818487 DOI: 10.1002/jcp.29997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 06/28/2020] [Accepted: 07/24/2020] [Indexed: 12/23/2022]
Abstract
Na+–K+–Cl− cotransporter 2 (NKCC2; SLC12A1) is an integral membrane protein that comes as three splice variants and mediates the cotranslocation of Na+, K+, and Cl− ions through the apical membrane of the thick ascending loop of Henle (TALH). In doing so, and through the involvement of other ion transport systems, it allows this nephron segment to reclaim a large fraction of the ultrafiltered Na+, Cl−, Ca2+, Mg2+, and HCO3− loads. The functional relevance of NKCC2 in human is illustrated by the many abnormalities that result from the inactivation of this transport system through the use of loop diuretics or in the setting of inherited disorders. The following presentation aims at discussing the physiological roles and molecular characteristics of Na+–K+–Cl− cotransport in the TALH and those of the individual NKCC2 splice variants more specifically. Many of the historical and recent data that have emerged from the experiments conducted will be outlined and their larger meaning will also be placed into perspective with the aid of various hypotheses.
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Affiliation(s)
- Andree-Anne Marcoux
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
| | - Laurence E Tremblay
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
| | - Samira Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
| | - Marie-Jeanne Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
| | - Fabrice Mac-Way
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
| | - Alexandre P Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada.,Cardiometabolic Axis, School of Kinesiology and Physical Activity Sciences, University of Montréal, Montréal, Quebec, Canada
| | - Paul Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Québec, Canada
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Zicha J, Hojná S, Vaňourková Z, Kopkan L, Vaněčková I. Is renal ß-adrenergic-WNK4-NCC pathway important in salt hypertension of Dahl rats? Physiol Res 2019; 68:873-882. [PMID: 31647304 DOI: 10.33549/physiolres.934334] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In 2011 Fujita and coworkers proposed that ß-adrenergic stimulation causes decreased serine/threonine-protein kinase WNK4 transcription leading to the activation of Na-Cl cotransporter (NCC) which participates in salt sensitivity and salt hypertension development in rodents. The aim of our study was to investigate whether the above hypothesis is also valid for salt hypertension of Dahl rats, which are characterized by high sympathetic tone and abnormal renal sodium handling. Male 8-week-old salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) Dahl rats were fed either low-salt diet (LS, 0.4 % NaCl) or high-salt diet (HS, 4 % NaCl) for 6 weeks. Half of the animals on either diet were chronically treated with non-selective ß-blocker propranolol (100 mg/kg/day). At the end of the experiment diuresis and sodium excretion were measured prior and after hydrochlorothiazide injection (HCTZ, 10 mg/kg i.p.). Furthermore, blood pressure (BP), heart rate (HR), sympathetic (pentolinium 5 mg/kg i.v.) and NO-dependent (L-NAME 30 mg/kg i.v.) BP components were determined. Chronic HS diet feeding increased BP through sympathoexcitation in SS/Jr but not in SR/Jr rats. Concomitant propranolol treatment did not lower BP in either experimental group. Under the conditions of low salt intake HCTZ increased diuresis, natriuresis and fractional sodium excretion in SR/Jr but not in SS/Jr rats. HS diet feeding attenuated renal response to HCT in SR/Jr rats, whereas no HCTZ effect was observed in SS/Jr rats fed HS diet. Propranolol treatment did not modify diuresis or natriuresis in any experimental group. In conclusions, our present data do not support the idea on the essential importance of renal ß-adrenergic-WNK4-NCC pathway in pathogenesis and/or maintenance of salt hypertension in Dahl rats.
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Affiliation(s)
- J Zicha
- Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
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Gonzalez-Vicente A, Saez F, Monzon CM, Asirwatham J, Garvin JL. Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension. Physiol Rev 2019; 99:235-309. [PMID: 30354966 DOI: 10.1152/physrev.00055.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.
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Affiliation(s)
| | - Fara Saez
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Casandra M Monzon
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jessica Asirwatham
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
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Padmanabhan S, Joe B. Towards Precision Medicine for Hypertension: A Review of Genomic, Epigenomic, and Microbiomic Effects on Blood Pressure in Experimental Rat Models and Humans. Physiol Rev 2017; 97:1469-1528. [PMID: 28931564 PMCID: PMC6347103 DOI: 10.1152/physrev.00035.2016] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 04/28/2017] [Accepted: 04/29/2017] [Indexed: 12/11/2022] Open
Abstract
Compelling evidence for the inherited nature of essential hypertension has led to extensive research in rats and humans. Rats have served as the primary model for research on the genetics of hypertension resulting in identification of genomic regions that are causally associated with hypertension. In more recent times, genome-wide studies in humans have also begun to improve our understanding of the inheritance of polygenic forms of hypertension. Based on the chronological progression of research into the genetics of hypertension as the "structural backbone," this review catalogs and discusses the rat and human genetic elements mapped and implicated in blood pressure regulation. Furthermore, the knowledge gained from these genetic studies that provide evidence to suggest that much of the genetic influence on hypertension residing within noncoding elements of our DNA and operating through pervasive epistasis or gene-gene interactions is highlighted. Lastly, perspectives on current thinking that the more complex "triad" of the genome, epigenome, and the microbiome operating to influence the inheritance of hypertension, is documented. Overall, the collective knowledge gained from rats and humans is disappointing in the sense that major hypertension-causing genes as targets for clinical management of essential hypertension may not be a clinical reality. On the other hand, the realization that the polygenic nature of hypertension prevents any single locus from being a relevant clinical target for all humans directs future studies on the genetics of hypertension towards an individualized genomic approach.
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Affiliation(s)
- Sandosh Padmanabhan
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; and Center for Hypertension and Personalized Medicine; Department of Physiology and Pharmacology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio
| | - Bina Joe
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; and Center for Hypertension and Personalized Medicine; Department of Physiology and Pharmacology, University of Toledo College of Medicine and Life Sciences, Toledo, Ohio
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Elijovich F, Weinberger MH, Anderson CAM, Appel LJ, Bursztyn M, Cook NR, Dart RA, Newton-Cheh CH, Sacks FM, Laffer CL. Salt Sensitivity of Blood Pressure: A Scientific Statement From the American Heart Association. Hypertension 2016; 68:e7-e46. [PMID: 27443572 DOI: 10.1161/hyp.0000000000000047] [Citation(s) in RCA: 301] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Abstract
Chloride transport along the nephron is one of the key actions of the kidney that regulates extracellular volume and blood pressure. To maintain steady state, the kidney needs to reabsorb the vast majority of the filtered load of chloride. This is accomplished by the integrated function of sequential chloride transport activities along the nephron. The detailed mechanisms of transport in each segment generate unique patterns of interactions between chloride and numerous other individual components that are transported by the kidney. Consequently, chloride transport is inextricably intertwined with that of sodium, potassium, protons, calcium, and water. These interactions not only allow for exquisitely precise regulation but also determine the particular patterns in which the system can fail in disease states.
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Affiliation(s)
- John C Edwards
- UNC Kidney Center and the Departments of Medicine and Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
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Ares GR, Caceres PS, Ortiz PA. Molecular regulation of NKCC2 in the thick ascending limb. Am J Physiol Renal Physiol 2011; 301:F1143-59. [PMID: 21900458 DOI: 10.1152/ajprenal.00396.2011] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The kidney plays an essential role in blood pressure regulation by controlling short-term and long-term NaCl and water balance. The thick ascending limb of the loop of Henle (TAL) reabsorbs 25-30% of the NaCl filtered by the glomeruli in a process mediated by the apical Na(+)-K(+)-2Cl(-) cotransporter NKCC2, which allows Na(+) and Cl(-) entry from the tubule lumen into TAL cells. In humans, mutations in the gene coding for NKCC2 result in decreased or absent activity characterized by severe salt and volume loss and decreased blood pressure (Bartter syndrome type 1). Opposite to Bartter's syndrome, enhanced NaCl absorption by the TAL is associated with human hypertension and animal models of salt-sensitive hypertension. TAL NaCl reabsorption is subject to exquisite control by hormones like vasopressin, parathyroid, glucagon, and adrenergic agonists (epinephrine and norepinephrine) that stimulate NaCl reabsorption. Atrial natriuretic peptides or autacoids like nitric oxide and prostaglandins inhibit NaCl reabsorption, promoting salt excretion. In general, the mechanism by which hormones control NaCl reabsorption is mediated directly or indirectly by altering the activity of NKCC2 in the TAL. Despite the importance of NKCC2 in renal physiology, the molecular mechanisms by which hormones, autacoids, physical factors, and intracellular ions regulate NKCC2 activity are largely unknown. During the last 5 years, it has become apparent that at least three molecular mechanisms determine NKCC2 activity. As such, membrane trafficking, phosphorylation, and protein-protein interactions have recently been described in TALs and heterologous expression systems as mechanisms that modulate NKCC2 activity. The focus of this review is to summarize recent data regarding NKCC2 regulation and discuss their potential implications in physiological control of TAL function, renal physiology, and blood pressure regulation.
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Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Dept. of Internal Medicine, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA
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Barber Fox M, Barber Gutiérrez E, Fox Pascual M. Comportamiento del volumen sanguíneo corporal en ratas con hipertrofia tubular proximal. HIPERTENSION Y RIESGO VASCULAR 2009. [DOI: 10.1016/s1889-1837(09)71182-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Giménez I. Molecular mechanisms and regulation of furosemide-sensitive Na-K-Cl cotransporters. Curr Opin Nephrol Hypertens 2007; 15:517-23. [PMID: 16914965 DOI: 10.1097/01.mnh.0000242178.44576.b0] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Relevant advances towards understanding how furosemide-sensitive Na-K-Cl cotransporters (NKCC) are regulated by alternative splicing, phosphorylation and membrane expression have been made, which are critical to comprehending the role of NKCCs in blood pressure homeostasis. RECENT FINDINGS A major breakthrough has been the description of a macromolecular complex responsible for the regulatory phosphorylation of NKCCs, involving members of two families of novel serine-threonine kinases: WNK kinases and Ste-20-related kinases SPAK and OSR1. A new regulatory pathway has been defined, with WNK lying upstream of SPAK-OSR1 and the latter kinases directly phosphorylating NKCC. New evidence has arisen supporting regulation of NKCC membrane expression, possibly through the same mechanisms regulating phosphorylation. Alternative splicing of kidney-specific NKCC2 also appears to be a regulated process. Renal roles for NKCC1 have been described, including an unexpected role in controlling renin secretion. SUMMARY We now begin to understand the biochemical pathways mediating NKCC regulatory phosphorylation, which are governed by kinases that, like NKCCs, have been linked to the genesis of hypertension. Complementary long-term regulation of NKCC membrane expression, alternative splicing or gene transcription, however, should not be overlooked. Deciphering the relationships between these processes will enhance our understanding of the pathogenesis of hypertension.
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Affiliation(s)
- Ignacio Giménez
- Department of Pharmacology and Physiology, University of Zaragoza, Zaragoza, Spain.
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Matthews DB, Bhave SV, Belknap JK, Brittingham C, Chesler EJ, Hitzemann RJ, Hoffmann PL, Lu L, McWeeney S, Miles MF, Tabakoff B, Williams RW. Complex Genetics of Interactions of Alcohol and CNS Function and Behavior. Alcohol Clin Exp Res 2006; 29:1706-19. [PMID: 16205371 DOI: 10.1097/01.alc.0000179209.44407.df] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This work summarizes the proceedings of a symposium at the 2004 RSA Meeting in Vancouver, Canada. The organizers were R. W. Williams and D. B. Matthews; the Chair was M. F. Miles. The presentations were (1) WebQTL: A resource for analysis of gene expression variation and the genetic dissection of alcohol related phenotypes, by E. J. Chesler, (2) The marriage of microarray and qtl analyses: what's to gain, by J. K. Belknap, (3) Use of WebQTL to identify QTLs associated with footshock stress and ethanol related behaviors, by D. B. Matthews, (4) A high throughput strategy for the detection of quantitative trait genes, by R. J. Hitzemann, and (5) The use of gene arrays in conjunction with transgenic and selected animals to understand anxiety in alcoholism, by. B. Tabakoff.
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Affiliation(s)
- Douglas B Matthews
- Department of Psychology, University of Memphis, Memphis, Tennessee 38152, USA.
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Kaneko Y, Cloix JF, Herrera VL, Ruiz-Opazo N. Corroboration of Dahl S Q276L alpha1Na,K-ATPase protein sequence: impact on affinities for ligands and on E1 conformation. J Hypertens 2005; 23:745-52. [PMID: 15775778 DOI: 10.1097/01.hjh.0000163142.89835.c7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Multifactorial analyses support the hypothesis that alpha1Na,K-ATPase is a hypertension susceptibility gene in Dahl S rats. However, two studies report non-detection of the A1079T transversion underlying the Q276L substitution in Dahl S alpha1Na,K-ATPase questioning the validity of ATP1A1 as a hypertension susceptibility gene. To resolve this discordance, we investigated the issue at the protein level. DESIGN AND METHODS We employed protein blot analysis using Q276L- and Q276-specific; antipeptide-specific antibodies; tested differential chymotrypsin cleavage efficiency, measured differential Na and K affinities of alpha1Na,K-ATPases in Dahl S and Dahl R renal membranes and determined amino acid sequences of purified Dahl S alpha1Na,K-ATPase chymotryptic-digest peptides. RESULTS We detected Q276L variant protein in Dahl S rats; and Q276 wild-type variant in Dahl R, spontaneously hypertensive (SHR), Lewis and Wistar-Kyoto (WKY) rat kidney membranes. Q276L variant exhibits less chymotrypsin cleavage efficiency than the Q276 wild-type variant, consistent with the substitution of hydrophobic L for hydrophilic Q. Kinetic studies of kidney membranes detect increased Na affinity and decreased K affinity in renal Dahl S alpha1Na,K-ATPase compared with Dahl R. Protein sequencing of high pressure liquid chromatography (HPLC)-purified chymotrypsin digested 77 kDa peptide confirms Q276L substitution in the Dahl S alpha1Na,K-ATPase. CONCLUSIONS Data demonstrate the existence and functional significance of the Q276L variant in Dahl S rats.
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Affiliation(s)
- Yuji Kaneko
- Section of Molecular Medicine, Department of Medicine, Boston University School of Medicine, 700 Albany Street, W-609, Boston, Massachusetts 02118, USA
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Abstract
The renin-angiotensin system (RAS) is critically involved in cardiovascular and renal function and in disease conditions, and has been shown to be a far more complex system than initially thought. A recently discovered homologue of angiotensin-converting enzyme (ACE)--ACE2--appears to negatively regulate the RAS. ACE2 cleaves Ang I and Ang II into the inactive Ang 1-9 and Ang 1-7, respectively. ACE2 is highly expressed in kidney and heart and is especially confined to the endothelium. With quantitative trait locus (QTL) mapping, ACE2 was defined as a QTL on the X chromosome in rat models of hypertension. In these animal models, kidney ACE2 messenger RNA and protein expression were markedly reduced, making ACE2 a candidate gene for this QTL. Targeted disruption of ACE2 in mice failed to elicit hypertension, but resulted in severe impairment in myocardial contractility with increased angiotensin II levels. Genetic ablation of ACE in the ACE2 null mice rescued the cardiac phenotype. These genetic data show that ACE2 is an essential regulator of heart function in vivo. Basal renal morphology and function were not altered by the inactivation of ACE2. The novel role of ACE2 in hydrolyzing several other peptides-such as the apelin peptides, opioids, and kinin metabolites-raises the possibility that peptide systems other than angiotensin and its derivatives also may have an important role in regulating cardiovascular and renal function.
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Affiliation(s)
- Gavin Y Oudit
- Department of Medical Biophysics and Richard Lewar/Heart and Stroke Center of Excellence, University of Toronto, Toronto, Canada
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Gagnon E, Forbush B, Flemmer AW, Giménez I, Caron L, Isenring P. Functional and molecular characterization of the shark renal Na-K-Cl cotransporter: novel aspects. Am J Physiol Renal Physiol 2002; 283:F1046-55. [PMID: 12372780 DOI: 10.1152/ajprenal.00107.2002] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Na-K-Cl cotransporter isoform 1 (NKCC1) has been isolated from several species, including Squalus acanthias. A second kidney-specific isoform (NKCC2) has been cloned mainly from higher vertebrates. Here, we have isolated the S. acanthias NKCC2 and found that it is produced in at least four spliced variants (saNKCC2A, saNKCC2F, saNKCC2AF, and saNKCC2AFno8) of approximately 1,090 residues. Expression of these transcripts in Xenopus laevis oocytes revealed that only the A and F variants are functional and that they are more active after incubation in low-Cl or hyperosmolar media. Rates of activation after exposure to these media were exceptionally rapid, demonstrating for the first time that the NKCC2 itself represents an important site of regulation by Cl and that extracellular domains are involved. Another remarkable finding in this study was the failure to identify NKCC2B, a variant found in the kidney of higher vertebrates and expressed specifically in macula densa cells. This result, in conjunction with the fact that the shark kidney lacks a well-developed juxtaglomerular apparatus, suggests that the B exon evolved as a result of selective pressure (presumably by exon duplication) and that a restricted relationship exists between NKCC2B and macula densa.
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Affiliation(s)
- Edith Gagnon
- Groupe de Recherche en Néphrologie, Department of Medicine, Faculty of Medicine, Laval University, Laval, Quebec, Canada G1R 2J6
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Suketa Y. [Fundamental and applied studies on transport and metabolism of electrolytes and glucose--aim to contact with molecular biology]. YAKUGAKU ZASSHI 2002; 122:507-25. [PMID: 12187767 DOI: 10.1248/yakushi.122.507] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The authors' research focuses on polyuria, natriuresis, glucosuria, glycemia, and renal calcification in occupational lead poisoning and endemic fluorosis. Changes in electrolyte mobilization and in glucose metabolism and transport following the administration of lead compounds or fluoride were examined to elucidate these mechanisms. The results suggest fundamental approaches to the mechanism of aging and life style diseases. Our results show that: 1) Natriuresis and polyuria in lead poisoning and fluorosis are due to a decrease in renal Na/K-ATPase activity; 2) Renal calcification in fluorosis is due to stimulation of parathyroid function and activation of the renal phosphatidylinositol cascade; 3) Glycemia in fluorosis is due to elevation of renal and hepatic glucose-6-phosphatase activities; 4) Glusosuria in fluorosis is due to decreased renal Na/K-ATPase activity (but fluoride administered directly did not damage the renal Na/glucose cotransporter (SGLT); 5) Renal calcification in fluorosis is due to stimulation of parathyroid function; and 6) The decrease in renal Na/K-ATPase and SGLT activities with aging and hypertension is due to a decrease in phosphorylation activity by protein kinase C (PKC) etc. (decrease in PKC productivity with aging and hypertension).
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Affiliation(s)
- Yasunobu Suketa
- University of Shizuoka School of Pharmaceutical Sciences, 52-1 Yada, Shizuoka 422-8526, Japan.
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Affiliation(s)
- Ron Korstanje
- The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA
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Giménez I, Isenring P, Forbush B. Spatially distributed alternative splice variants of the renal Na-K-Cl cotransporter exhibit dramatically different affinities for the transported ions. J Biol Chem 2002; 277:8767-70. [PMID: 11815599 DOI: 10.1074/jbc.c200021200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Three splice variants of the renal Na-K-Cl cotransporter (NKCC2 F, A, and B) are spatially distributed along the thick ascending limb of the mammalian kidney. To test whether NKCC2 splice variants differ in ion transport characteristics we expressed cDNAs encoding rabbit NKCC2 F, A, and B in Xenopus oocytes and determined the ion dependence of bumetanide-sensitive (86)Rb influx. The three splice variants of NKCC2 showed dramatic differences in their kinetic behavior. The medullary variant F exhibited 3-4-fold lower affinity than variants A and B for Na(+) and K(+). Chloride affinities also markedly distinguish the three variants (K(m)F = 111.3, K(m)A = 44.7, and K(m)B = 8.9 mm Cl(-)). Thus, the kinetic properties of the NKCC2 splice variants are consistent with the spatial distribution of the variants along the thick ascending limb as they are involved in reabsorbing Na(+), K(+), and Cl(-) from a progressively diluted fluid in the tubule lumen. Variant B also showed an anomalous inhibition of rubidium influx at high extracellular Na(+) concentrations, possibly important in its highly specialized role in the macula densa. The adaptation of the kinetic characteristics of the NKCC2 variants to the luminal concentrations of substrate represents an excellent example of functional specialization and diversity that can be achieved through alternative mRNA splicing.
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Affiliation(s)
- Ignacio Giménez
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06511, USA.
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