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Abstract
QTL mapping in humans and rats has identified hundreds of blood-pressure-related phenotypes and genomic regions; the next daunting task is gene identification and validation. The development of novel rat model systems that mimic many elements of the human disease, coupled with advances in the genomic and informatic infrastructure for rats, promise to revolutionize the hunt for genes that determine susceptibility to hypertension. Furthermore, methods are evolving that should enable the identification of candidate genes in human populations. Together with the computational reconstruction of regulatory networks, these methods provide opportunities to significantly advance our understanding of the underlying aetiology of hypertension.
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Affiliation(s)
- Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, USA.
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202
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Jiang Y, Ferguson WB, Peng JB. WNK4 enhances TRPV5-mediated calcium transport: potential role in hypercalciuria of familial hyperkalemic hypertension caused by gene mutation of WNK4. Am J Physiol Renal Physiol 2006; 292:F545-54. [PMID: 17018846 DOI: 10.1152/ajprenal.00187.2006] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The epithelial Ca(2+) channel TRPV5 serves as a gatekeeper for active Ca(2+) reabsorption in the distal convoluted tubule and connecting tubule of the kidney. WNK4, a protein serine/threonine kinase with gene mutations that cause familial hyperkalemic hypertension (FHH), including a subtype with hypercalciuria, is also localized in the distal tubule of the nephron. To understand the role of WNK4 in modulation of Ca(2+) reabsorption, we evaluated the effect of WNK4 on TRPV5-mediated Ca(2+) transport in Xenopus laevis oocytes. Coexpression of TRPV5 with WNK4 resulted in a twofold increase in TRPV5-mediated Ca(2+) uptake. The increase in Ca(2+) uptake was due to the increase in surface expression of TRPV5. When the thiazide-sensitive Na(+)-Cl(-) cotransporter NCC was coexpressed, the effect of WNK4 on TRPV5 was weakened by NCC in a dose-dependent manner. Although the WNK4 disease-causing mutants E562K, D564A, Q565E, and R1185C retained their ability to upregulate TRPV5, the blocking effect of NCC was further strengthened when wild-type WNK4 was replaced by the Q565E mutant, which causes FHH with hypercalciuria. We conclude that WNK4 positively regulates TRPV5-mediated Ca(2+) transport and that the inhibitory effect of NCC on this process may be involved in the pathogenesis of hypercalciuria of FHH caused by gene mutation in WNK4.
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Affiliation(s)
- Yi Jiang
- Department of Medicine, Division of Nephrology, University of Alabama at Birmingham, AL 35294-0006, USA
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203
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Sun X, Gao L, Yu RK, Zeng G. Down-regulation of WNK1 protein kinase in neural progenitor cells suppresses cell proliferation and migration. J Neurochem 2006; 99:1114-21. [PMID: 17018027 DOI: 10.1111/j.1471-4159.2006.04159.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
WNK1, a Ser/Thr protein kinase, is widely expressed in many tissues. Its biological functions are largely unknown. Disruption of the WNK1 gene in mice leads to embryonic lethality at day 13, implicating a critical role of WNK1 in embryonic development. To investigate this potential function, we used antisense strategy to knock down the expression of WNK1 in a mouse neural progenitor cell line, C17.2. Down-regulation of WNK1 in C17.2 cells greatly reduced cell growth. Addition of epidermal growth factor (EGF), a mitogen for C17.2 cells, had no effect on growth. The WNK1-knockdown cells showed a flat and rounded morphology, characteristic of the immature and non-differentiated phenotype of the progenitor cells; this was further demonstrated by immunostaining for the progenitor and neuronal markers. Migration of the WNK1-knockdown C17.2 cells was reduced as tested in culture dishes or Matrigel-covered chambers. Moreover, activation of extracellular signal-regulated kinase (ERK1)/2 and ERK5 by EGF in the WNK1-knockdown cells was suppressed. These results demonstrate a novel function of WNK1 in proliferation, migration, and differentiation of neural progenitor cells, likely by mechanisms involving activation of the mitogen-activated protein (MAP) kinase ERK1/2 and/or ERK5 pathways.
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Affiliation(s)
- Xutong Sun
- Developmental Neurobiology Program, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA.
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204
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Kahle KT, Rinehart J, Ring A, Gimenez I, Gamba G, Hebert SC, Lifton RP. WNK protein kinases modulate cellular Cl- flux by altering the phosphorylation state of the Na-K-Cl and K-Cl cotransporters. Physiology (Bethesda) 2006; 21:326-35. [PMID: 16990453 DOI: 10.1152/physiol.00015.2006] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Precise control of cellular Cl(-) transport is necessary for many fundamental physiological processes. For example, the intracellular concentration of Cl(-), fine-tuned through the coordinated action of cellular Cl(-) influx and efflux mechanisms, determines whether a neuron's response to GABA is excitatory or inhibitory. In epithelia, synchrony between apical and basolateral Cl(-) flux, and transcellular and paracellular Cl(-) transport, is necessary for efficient transepithelial Cl(-) reabsorption or secretion. In cells throughout the body, coordination of Cl(-) entry and exit mechanisms help defend against changes in cell volume. The Na-K-Cl and K-Cl cotransporters of the SLC12 gene family are important molecular determinants of Cl(-) entry and exit, respectively, in these systems. The WNK serine-threonine kinase family, members of which are mutated in an inherited form of human hypertension, are components of a signaling pathway that coordinates Cl(-) influx and efflux through SLC12 cotransporters to dynamically regulate intracellular Cl(-) activity.
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Affiliation(s)
- Kristopher T Kahle
- Howard Hughes Medical Institute, Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA
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205
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Lalioti MD, Zhang J, Volkman HM, Kahle KT, Hoffmann KE, Toka HR, Nelson-Williams C, Ellison DH, Flavell R, Booth CJ, Lu Y, Geller DS, Lifton RP. Wnk4 controls blood pressure and potassium homeostasis via regulation of mass and activity of the distal convoluted tubule. Nat Genet 2006; 38:1124-32. [PMID: 16964266 DOI: 10.1038/ng1877] [Citation(s) in RCA: 302] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Accepted: 08/07/2006] [Indexed: 11/08/2022]
Abstract
The mechanisms that govern homeostasis of complex systems have been elusive but can be illuminated by mutations that disrupt system behavior. Mutations in the gene encoding the kinase WNK4 cause pseudohypoaldosteronism type II (PHAII), a syndrome featuring hypertension and hyperkalemia. We show that physiology in mice transgenic for genomic segments harboring wild-type (TgWnk4(WT)) or PHAII mutant (TgWnk4(PHAII)) Wnk4 is changed in opposite directions: TgWnk4(PHAII) mice have higher blood pressure, hyperkalemia, hypercalciuria and marked hyperplasia of the distal convoluted tubule (DCT), whereas the opposite is true in TgWnk4(WT) mice. Genetic deficiency for the Na-Cl cotransporter of the DCT (NCC) reverses phenotypes seen in TgWnk4(PHAII) mice, demonstrating that the effects of the PHAII mutation are due to altered NCC activity. These findings establish that Wnk4 is a molecular switch that regulates the balance between NaCl reabsorption and K+ secretion by altering the mass and function of the DCT through its effect on NCC.
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Affiliation(s)
- Maria D Lalioti
- Department of Genetics, Howard Hughes Medical, Institute, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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206
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Xie J, Craig L, Cobb MH, Huang CL. Role of with-no-lysine [K] kinases in the pathogenesis of Gordon's syndrome. Pediatr Nephrol 2006; 21:1231-6. [PMID: 16683163 DOI: 10.1007/s00467-006-0106-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Accepted: 01/23/2006] [Indexed: 11/28/2022]
Abstract
Gordon's syndrome, also known as pseudohypoaldosteronism type II (PHA II) or familial hypertension with hyperkalemia, is an autosomal-dominant disease characterized by hypertension, hyperkalemia, hyperchloremic metabolic acidosis, and normal glomerular filtration rate. Recent positional cloning has linked mutations of WNK1 and WNK4 to Gordon's syndrome. With-no-lysine [K] (WNK) kinases are a new family of large serine-threonine protein kinases with an atypical placement of the catalytic lysine. Here, we review the pathogenesis of PHA II based on current understanding of the actions of WNK1 and WNK4 on Na+ and K+ handling in the renal distal tubule.
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Affiliation(s)
- Jian Xie
- Department of Medicine, Room J5-104, MC-8856, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-8856, USA
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207
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Ohta A, Yang SS, Rai T, Chiga M, Sasaki S, Uchida S. Overexpression of human WNK1 increases paracellular chloride permeability and phosphorylation of claudin-4 in MDCKII cells. Biochem Biophys Res Commun 2006; 349:804-8. [PMID: 16949040 DOI: 10.1016/j.bbrc.2006.08.101] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Accepted: 08/18/2006] [Indexed: 11/22/2022]
Abstract
Pseudohypoaldosteronism type II (PHAII), an autosomal dominant disorder characterized by hypertension, hyperkalemia, and hyperchloremic acidosis, is reportedly due to mutations in WNK1 and WNK4 kinase genes. However, the pathogenesis of the disease remains unknown. Mutations in the WNK1 gene are the deletions in the first intron, which reportedly increases WNK1 mRNA expression. Thus, we generated WNK1 over-expressing stable cell lines using MDCKII cells to model the distal nephron of PHAII patients. Using these cell lines, we investigated whether increased WNK1 expression might affect paracellular chloride permeability and claudin phosphorylation, since we previously observed an increase in both with a disease-causing mutant WNK4. WNK1 expression in MDCKII cells increased chloride permeability two to threefold. Co-expression of wild-type WNK4 did not further increase WNK1-enhanced chloride permeability. WNK1 expression also induced phosphorylation of endogenous claudin-4 in MDCKII cells, as well as over-expressed claudin-4. Combined, these results suggest that increased WNK1 expression has the same effect on chloride permeability and claudin phosphorylation as the mutant WNK4. Thus, increased chloride shunt may be involved in the pathogenesis of PHAII caused by WNK1 mutations.
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Affiliation(s)
- Akihito Ohta
- Department of Nephrology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
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208
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Delaloy C, Hadchouel J, Imbert-Teboul M, Clemessy M, Houot AM, Jeunemaitre X. Cardiovascular expression of the mouse WNK1 gene during development and adulthood revealed by a BAC reporter assay. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 169:105-18. [PMID: 16816365 PMCID: PMC1698764 DOI: 10.2353/ajpath.2006.051290] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Large deletions in WNK1 are associated with inherited arterial hypertension. WNK1 encodes two types of protein: a kidney-specific isoform (KS-WNK1) lacking kinase activity and a ubiquitously expressed full-length isoform (L-WNK1) with serine threonine kinase activity. Disease is thought to result from hypermorphic mutations increasing the production of one or both isoforms. However, the pattern of L-WNK1 expression remains poorly characterized. We generated transgenic mice bearing a murine WNK1 BAC containing the nlacZ reporter gene for monitoring L-WNK1 expression during development and adulthood. We observed previously unsuspected early expression in the vessels and primitive heart during embryogenesis, consistent with the early death of WNK1(-/-) mice. The generalized cardiovascular expression observed in adulthood may also suggest a possible kidney-independent role in blood pressure regulation. The second unsuspected site of L-WNK1 expression was the granular layer and Purkinje cells of the cerebellum, suggesting a role in local ion balance or cell trafficking. In the kidney, discordance between endogenous L-WNK1 and transgene expression suggests that either cis-regulatory elements important for physiological renal expression lie outside the BAC sequence or that illegitimate interactions occur between promoters. Despite this limitation, this transgenic model is a potentially valuable tool for the analysis of spatial and temporal aspects of WNK1 expression and regulation.
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209
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O'Reilly M, Marshall E, Macgillivray T, Mittal M, Xue W, Kenyon CJ, Brown RW. Dietary electrolyte-driven responses in the renal WNK kinase pathway in vivo. J Am Soc Nephrol 2006; 17:2402-13. [PMID: 16899520 DOI: 10.1681/asn.2005111197] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
WNK1 and WNK4 are unusual serine/threonine kinases with atypical positioning of the catalytic active-site lysine (WNK: With-No-K[lysine]). Mutations in these WNK kinase genes can cause familial hyperkalemic hypertension (FHHt), an autosomal dominant, hypertensive, hyperkalemic disorder, implicating this novel WNK pathway in normal regulation of BP and electrolyte balance. Full-length (WNK1-L) and short (WNK1-S) kinase-deficient WNK1 isoforms previously have been identified. Importantly, WNK1-S is overwhelmingly predominant in kidney. Recent Xenopus oocyte studies implicate WNK4 in inhibition of both thiazide-sensitive co-transporter-mediated Na+ reabsorption and K+ secretion via renal outer medullary K+ channel and now suggest that WNK4 is inhibited by WNK1-L, itself inhibited by WNK1-S. This study examined WNK pathway gene expression in mouse kidney and its regulation in vivo. Expression of WNK1-S and WNK4 is strongest in distal tubule, dropping sharply in collecting duct and with WNK4 also expressed in thick ascending limb and the macula densa. These nephron segments that express WNK1-S and WNK4 mRNA have major influence on long-term NaCl reabsorption, BP, K+, and acid-base balance, processes that all are disrupted in FHHt. In vivo, this novel WNK pathway responds with significant upregulation of WNK1-S and WNK4 with high K+ intake and reduction in WNK1-S on chronic lowering of K+ or Na+ intake. A two-compartment distal nephron model explains these in vivo findings and the pathophysiology of FHHt well, with WNK and classic aldosterone pathways responding to drivers from K+ balance, extracellular volume, and aldosterone and cross-talk through distal Na+ delivery regulating electrolyte balance and BP.
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Affiliation(s)
- Michelle O'Reilly
- Centre for Cardiovascular Science, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh, UK EH16 4TJ
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210
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Pacheco-Alvarez D, Cristóbal PS, Meade P, Moreno E, Vazquez N, Muñoz E, Díaz A, Juárez ME, Giménez I, Gamba G. The Na+:Cl- cotransporter is activated and phosphorylated at the amino-terminal domain upon intracellular chloride depletion. J Biol Chem 2006; 281:28755-63. [PMID: 16887815 DOI: 10.1074/jbc.m603773200] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The renal Na(+):Cl(-) cotransporter rNCC is mutated in human disease, is the therapeutic target of thiazide-type diuretics, and is clearly involved in arterial blood pressure regulation. rNCC belongs to an electroneutral cation-coupled chloride cotransporter family (SLC12A) that has two major branches with inverse physiological functions and regulation: sodium-driven cotransporters (NCC and NKCC1/2) that mediate cellular Cl(-) influx are activated by phosphorylation, whereas potassium-driven cotransporters (KCCs) that mediate cellular Cl(-) efflux are activated by dephosphorylation. A cluster of three threonine residues at the amino-terminal domain has been implicated in the regulation of NKCC1/2 by intracellular chloride, cell volume, vasopressin, and WNK/STE-20 kinases. Nothing is known, however, about rNCC regulatory mechanisms. By using rNCC heterologous expression in Xenopus laevis oocytes, here we show that two independent intracellular chloride-depleting strategies increased rNCC activity by 3-fold. The effect of both strategies was synergistic and dose-dependent. Confocal microscopy of enhanced green fluorescent protein-tagged rNCC showed no changes in rNCC cell surface expression, whereas immunoblot analysis, using the R5-anti-NKCC1-phosphoantibody, revealed increased phosphorylation of rNCC amino-terminal domain threonine residues Thr(53) and Thr(58). Elimination of these threonines together with serine residue Ser(71) completely prevented rNCC response to intracellular chloride depletion. We conclude that rNCC is activated by a mechanism that involves amino-terminal domain phosphorylation.
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Affiliation(s)
- Diana Pacheco-Alvarez
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónomade México, Tlalpan 14000, Mexico City, Mexico
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211
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Abstract
The kidney plays a central role in our ability to maintain an appropriate sodium balance, which is critical for the determination of blood pressure. The kidney's capacity for salt conservation may not be widely appreciated, and in general we consume vastly more salt than we need. Here we consider the socioeconomics of salt consumption, outline current knowledge of renal salt handling at the molecular level, describe some of the disease entities associated with abnormal sodium handling, give an overview of some of the animal models and their relevance to human disease, and examine the evidence that lowering our salt intake can help combat hypertension and cardiovascular disease.
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212
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Peng JB, Bell PD. Cellular mechanisms of WNK4-mediated regulation of ion transport proteins in the distal tubule. Kidney Int 2006; 69:2116-8. [PMID: 16761023 DOI: 10.1038/sj.ki.5000435] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Gene mutations in WNK4 kinase cause a genetic form of hypertension by affecting multiple ion transport pathways through different mechanisms. Cai et al. report that the inhibitory effect of WNK4 on the thiazide-sensitive sodium-chloride cotransporter occurs through the lysosomal degradation pathway in mammalian cells.
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Affiliation(s)
- J-B Peng
- Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0017, USA
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213
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214
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Subramanya AR, Yang CL, McCormick JA, Ellison DH. WNK kinases regulate sodium chloride and potassium transport by the aldosterone-sensitive distal nephron. Kidney Int 2006; 70:630-4. [PMID: 16820787 DOI: 10.1038/sj.ki.5001634] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
With-No-Lysine [K] (WNKs) are a recently discovered family of serine/threonine protein kinases that contain a uniquely structured catalytic domain. Mutations in the genes encoding two family members, WNK1 and WNK4, cause a chloride-dependent, thiazide-sensitive inherited syndrome of hypertension and hyperkalemia. Over the past 5 years, physiologic studies have demonstrated that these proteins regulate transcellular and paracellular epithelial ion flux. In this mini review, we discuss WNK1 and WNK4 gene products and their regulatory effects on sodium chloride and potassium handling in the aldosterone-sensitive distal nephron. Experimental observations regarding the effects of these proteins on transport processes mediated by the thiazide-sensitive Na-Cl co-transporter, the epithelial sodium channel, the renal outer medullary potassium channel, and the paracellular pathway integrate into a model that suggests an essential role for WNKs in coordinating renal Na-Cl reabsorption and K(+) secretion.
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Affiliation(s)
- A R Subramanya
- Department of Medicine, Division of Nephrology and Hypertension, Oregon Health and Science University, Portland, Oregon 97239, USA
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215
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Golbang AP, Cope G, Hamad A, Murthy M, Liu CH, Cuthbert AW, O'shaughnessy KM. Regulation of the expression of the Na/Cl cotransporter by WNK4 and WNK1: evidence that accelerated dynamin-dependent endocytosis is not involved. Am J Physiol Renal Physiol 2006; 291:F1369-76. [PMID: 16788137 DOI: 10.1152/ajprenal.00468.2005] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The novel serine/threonine kinases (with no lysine kinases or WNKs), WNK1 and WNK4, are encoded by the disease genes for Gordon syndrome (PRKWNK1 and PRKWNK4), a rare monogenic syndrome of hypertension and hyperkalemia. These proteins alter the expression of the thiazide-sensitive Na/Cl cotransporter (NCCT) in Xenopus laevis oocytes, although the details are controversial. We describe here our own experience and confirm that kinase-dead WNK4 (318D>A) is unable to affect Na+ fluxes through the thiazide-sensitive Na/Cl transporter (NCCT) or its membrane expression as an ECFP-NCCT fusion protein. However, the kinase domain is not sufficient for a functional WNK4 since deletion of the acidic motif (a motif unique to WNK family members) completely abolishes functional activity. Indeed, the NH2 terminal of WNK4 (1-620) containing the kinase domain and acidic motif retains full activity, but does not interact directly with NCCT in pull-down assays. Coexpression of WNK1 antagonizes the action of WNK4, and kinase-dead WNK1 (368D>A) or WNK1 carrying a WNK4 disease mutation (565Q>E) behaves in the same way as wild-type WNK1. This suggests kinase activity and charge conservation within the acidic motif are not essential for the WNK1-WNK4 interaction. We also report that WNK4 probably reduces surface expression largely through an effect on forward trafficking. Hence, the effect of WNK4 on NCCT expression is mimicked by dynamin, but the dominant-negative K44A dynamin mutant does not block the action of WNK4 itself. These results further highlight important differences in the mechanism by which WNK kinases affect expression of NCCT vs. other membrane proteins such as ROMK.
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216
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Cope G, Murthy M, Golbang AP, Hamad A, Liu CH, Cuthbert AW, O'Shaughnessy KM. WNK1 Affects Surface Expression of the ROMK Potassium Channel Independent of WNK4. J Am Soc Nephrol 2006; 17:1867-74. [PMID: 16775035 DOI: 10.1681/asn.2005111224] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The WNK (with no lysine kinase) kinases are a novel class of serine/threonine kinases that lack a characteristic lysine residue for ATP docking. Both WNK1 and WNK4 are expressed in the mammalian kidney, and mutations in either can cause the rare familial syndrome of hypertension and hyperkalemia (Gordon syndrome, or pseudohypoaldosteronism type 2). The molecular basis for the action of WNK4 is through alteration in the membrane expression of the NaCl co-transporter (NCCT) and the renal outer-medullary K channel KCNJ1 (ROMK). The actions of WNK1 are less well defined, and evidence to date suggests that it can affect NCCT expression but only in the presence of WNK4. The results of co-expressing WNK1 with ROMK in Xenopus oocytes are reported for the first time. These studies show that WNK1 is able to suppress total current directly through ROMK by causing a marked reduction in its surface expression. The effect is mimicked by a kinase-dead mutant of WNK1 (368D > A), suggesting that it is not dependent on its catalytic activity. Study of the time course of ROMK expression further suggests that WNK1 accelerates trafficking of ROMK from the membrane, and this effect seems to be dynamin dependent. Using fragments of full-length WNK1, it also is shown that the effect depends on residues in the middle section of the protein (502 to 1100 WNK1) that contains the acidic motif. Together, these findings emphasize that the molecular mechanisms that underpin WNK1 regulation of ROMK expression are distinct from those that affect NCCT expression.
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Affiliation(s)
- Georgina Cope
- Department of Medicine, University of Cambridge, Cambridge, UK
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217
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Moreno E, Cristóbal PS, Rivera M, Vázquez N, Bobadilla NA, Gamba G. Affinity-defining Domains in the Na-Cl Cotransporter. J Biol Chem 2006; 281:17266-17275. [PMID: 16624820 DOI: 10.1074/jbc.m602614200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The thiazide-sensitive Na+-Cl- cotransporter (NCC) is the major pathway for salt reabsorption in the distal convoluted tubule, serves as a receptor for thiazide-type diuretics, and is involved in inherited diseases associated with abnormal blood pressure. Little is known regarding the structure-function relationship in this cotransporter. Previous studies from our group reveal that mammalian NCC exhibits higher affinity for ions and thiazides than teleost NCC and suggest a role for glycosylation upon thiazide affinity. Here we have constructed a series of chimeric and mutant cDNAs between rat and flounder NCC to define the role of glycosylation status, the amino-terminal domain, the carboxyl-terminal domain, the extracellular glycosylated loop, and the transmembrane segments upon affinity for Na+, Cl-, and metolazone. Xenopus laevis oocytes were used as the heterologous expression system. We observed that elimination of glycosylation sites in flounder NCC did not affect the affinity of the cotransporter for metolazone. Also, swapping the amino-terminal domain, the carboxyl-terminal domain, the glycosylation sites, or the entire extracellular glycosylation loop between rat and flounder NCC had no effect upon ions or metolazone affinity. In contrast, interchanging transmembrane regions between rat and flounder NCC revealed that affinity-modifying residues for chloride are located within the transmembrane 1-7 region and for thiazides are located within the transmembrane 8-12 region, whereas both segments seem to be implicated in defining sodium affinity. These observations strongly suggest that binding sites for chloride and thiazide in NCC are different.
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Affiliation(s)
- Erika Moreno
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico; Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo 42160, México
| | - Pedro San Cristóbal
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico
| | - Manuel Rivera
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico
| | - Norma Vázquez
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico
| | - Norma A Bobadilla
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico
| | - Gerardo Gamba
- Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México Tlalpan 14000, Mexico City, Mexico.
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218
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Wade JB, Fang L, Liu J, Li D, Yang CL, Subramanya AR, Maouyo D, Mason A, Ellison DH, Welling PA. WNK1 kinase isoform switch regulates renal potassium excretion. Proc Natl Acad Sci U S A 2006; 103:8558-63. [PMID: 16709664 PMCID: PMC1482529 DOI: 10.1073/pnas.0603109103] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Members of the WNK family of serine/threonine kinases have been implicated as important modulators of salt homeostasis, regulating the balance between renal sodium reabsorption and potassium excretion. Gain-of-expression mutations in the WNK1 gene uncouple Na(+) and K(+) balance and cause a familial disorder of diminished renal potassium excretion, excessive sodium retention, and hypertension (pseudohypoaldosteronism type II or Gordon's syndrome). Alternative splicing of the WNK1 gene produces a kidney-specific short form of WNK1 (KS-WNK1) and a more ubiquitous long form (L-WNK1), but it is not clear how either of these isoforms influence renal potassium excretion. Here we demonstrate that KS-WNK1 and L-WNK1 converge in a pathway to regulate the renal outer-medullary K(+) channel, Kir1.1. Reconstitution studies in Xenopus oocytes reveal that L-WNK1 significantly inhibits Kir1.1 by reducing cell surface localization of the channel. A catalytically inactive L-WNK1 mutant has no inhibitory effect on Kir1.1, indicating that channel inhibition depends on kinase activity. KS-WNK1, lacking an intact kinase domain, does not directly alter Kir1.1. Instead, KS-WNK1 negatively regulates L-WNK1 to release Kir1.1 from inhibition. Acute dietary potassium loading increases the relative abundance of KS-WNK1 to L-WNK1 transcript and protein in the kidney, indicating that physiologic up-regulation of Kir1.1 activity involves a WNK1 isoform switch and KS-WNK1-mediated release from L-WNK1 inhibition. Thus, these observations provide evidence for the physiological regulation of Na(+) and K(+) balance by a kinase isoform switch mechanism.
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Affiliation(s)
- James B. Wade
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
- To whom correspondence may be addressed at:
Department of Physiology, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201. E-mail:
or
| | - Liang Fang
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
| | - Jie Liu
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
| | - Dimin Li
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
| | - Chao-Ling Yang
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, OR 97239
| | - Arohan R. Subramanya
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, OR 97239
| | - Djikolngar Maouyo
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
| | - Amanda Mason
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
| | - David H. Ellison
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, OR 97239
| | - Paul A. Welling
- *Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201; and
- To whom correspondence may be addressed at:
Department of Physiology, University of Maryland School of Medicine, 655 West Baltimore Street, Baltimore, MD 21201. E-mail:
or
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219
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Cai H, Cebotaru V, Wang YH, Zhang XM, Cebotaru L, Guggino SE, Guggino WB. WNK4 kinase regulates surface expression of the human sodium chloride cotransporter in mammalian cells. Kidney Int 2006; 69:2162-70. [PMID: 16688122 DOI: 10.1038/sj.ki.5000333] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Pseudohypoaldosteronism type II (PHA II) is caused by mutations of two members of WNK ((with no lysine (k)) kinase family. WNK4 wild type (WT) has been shown to inhibit the activity and surface expression of sodium chloride cotransporter (NCC) when expressed in Xenopus oocytes. Here, we have studied NCC protein processing in mammalian cells in the presence or absence of WNK4 WT and its mutants, E562K and R1185C, by surface biotinylation, Western blot, co-immunoprecipitation (Co-IP) and immunostaining. WNK4 WT significantly reduced NCC surface expression in Cos-7 cells (58.9+/-6.8% vs 100% in control, P<0.001, n=6), whereas its mutant E562K has no significant effect on NCC surface expression (92.9+/-5.3% vs 100%, P=NS, n=6). Another mutant R1185C still partially reduces surface expression of NCC (76.2+/-11.8% vs 100%, P<0.05, n=6). The reduction of NCC surface expression by WNK4 WT (62.9+/-3.3% of control group) is not altered by WT dynamin ((61.8+/-3.7% (P=NS)) or its mutant K44A ((65.4+/-14.1% (P=NS)). A Co-IP study showed that both WNK4 WT and WNK4 E562K interact with NCC. Furthermore, a proton pump inhibitor, bafilomycin A1, partially reverses the inhibitory effect of WNK4 WT on NCC expression. Our data suggest that WNK4 WT significantly inhibits NCC surface expression, which is not owing to an increase in clathrin-mediated endocytosis of NCC, but likely results from enhanced degradation of NCC through a lysosomal pathway.
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Affiliation(s)
- H Cai
- Division of Nephrology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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220
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Abstract
In this review, we outline the application and contribution of transgenic technology to establishing the genetic basis of blood pressure regulation and its dysfunction. Apart from a small number of examples where high blood pressure is the result of single gene mutation, essential hypertension is the sum of interactions between multiple environmental and genetic factors. Candidate genes can be identified by a variety of means including linkage analysis, quantitative trait locus analysis, association studies, and genome-wide scans. To test the validity of candidate genes, it is valuable to model hypertension in laboratory animals. Animal models generated through selective breeding strategies are often complex, and the underlying mechanism of hypertension is not clear. A complementary strategy has been the use of transgenic technology. Here one gene can be selectively, tissue specifically, or developmentally overexpressed, knocked down, or knocked out. Although resulting phenotypes may still be complicated, the underlying genetic perturbation is a starting point for identifying interactions that lead to hypertension. We recognize that the development and maintenance of hypertension may involve many systems including the vascular, cardiac, and central nervous systems. However, given the central role of the kidney in normal and abnormal blood pressure regulation, we intend to limit our review to models with a broadly renal perspective.
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Affiliation(s)
- Linda J Mullins
- Molecular Physiology Laboratory, Centre for Cardiovascular Science, Queens Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
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221
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Abstract
Reversible phosphorylation by protein kinases is probably one of the most important examples of post-translational modification of ion transport proteins. Ste20-related proline alanine-rich kinase (SPAK) and oxidative stress response kinase (OSR1) are two serine/threonine kinases belonging to the germinal centre-like kinase subfamily VI. Genetic analysis suggests that OSR1 evolved first, with SPAK arising following a gene duplication in vertebrate evolution. SPAK and OSR1 are two recently discovered kinases which have been linked to several key cellular processes, including cell differentiation, cell transformation and proliferation, cytoskeleton rearrangement, and most recently, regulation of ion transporters. Na-K-2Cl cotransporter activity is regulated by phosphorylation. Pharmacological evidence has identified several kinases and phosphatases which alter cotransporter function, however, no direct linkage between these enzymes and the cotransporter has been demonstrated. This article will review some of the physical and physiological properties of SPAK and OSR1, and present new evidence of a direct interaction between the Na-K-Cl cotransporter and the stress kinases.
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Affiliation(s)
- E Delpire
- Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
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222
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Hu DC, Burtner C, Hong A, Lobo PI, Okusa MD. Correction of renal hypertension after kidney transplantation from a donor with Gitelman syndrome. Am J Med Sci 2006; 331:105-9. [PMID: 16479187 DOI: 10.1097/00000441-200602000-00021] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The relationship between the kidney and blood pressure control is complex. Monogenetic forms of hypertension have recently been identified that implicate specific mutations responsible for blood pressure control. The thiazide sensitive Na-Cl cotransporter (NCC) has been implicated in the control of blood pressure, however a direct link between the kidney NCC and blood pressure regulation is lacking. Here, we report a case of chimerism in which a kidney from a patient with Gitelman syndrome was transplanted into a non-Gitelman hypertensive recipient. After transplantation, postural hypotension resulted, necessitating discontinuation of all antihypertensive medications used for treatment of calcineurin-induced hypertension. This is the first reported case of acquired Gitelman syndrome after transplantation. Transplantation of a Gitelman "kidney" into a hypertensive recipient provides additional support for the role of the kidney NCC in blood pressure regulation. Furthermore, this case suggests the potential use of thiazide diuretics in the treatment of calcineurin-induced hypertension.
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Affiliation(s)
- Daniel C Hu
- Department of Medicine, University of Virginia, Charlottesville, Virginia, USA
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223
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Yu ASL. WNK signaling in the distal tubule: an inhibitory cascade regulating salt transport. Am J Physiol Renal Physiol 2006; 290:F617-8. [PMID: 16461759 DOI: 10.1152/ajprenal.00409.2005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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224
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Gagnon KBE, England R, Delpire E. Characterization of SPAK and OSR1, regulatory kinases of the Na-K-2Cl cotransporter. Mol Cell Biol 2006; 26:689-98. [PMID: 16382158 PMCID: PMC1346913 DOI: 10.1128/mcb.26.2.689-698.2006] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Our recent studies demonstrate that SPAK (Ste20p-related Proline Alanine-rich Kinase), in combination with WNK4 [With No lysine (K) kinase], phosphorylates and stimulates the Na-K-2Cl cotransporter (NKCC1), whereas catalytically inactive SPAK (K104R) fails to activate the cotransporter. The catalytic domain of SPAK contains an activation loop between the well-conserved DFG and APE motifs. We speculated that four threonine residues (T231, T236, T243, and T247) in the activation loop might be sites of phosphorylation and kinase activation; therefore, we mutated each residue into an alanine. In this report, we demonstrate that coexpression of SPAK (T243A) or SPAK (T247A) with WNK4 not only prevented, but robustly inhibited, cotransporter activity in NKCC1-injected Xenopus laevis oocytes. These activation loop mutations produced an effect similar to that of the SPAK (K104R) mutant. In vitro phosphorylation experiments demonstrate that both intramolecular autophosphorylation of SPAK and phosphorylation of NKCC1 are significantly stronger in the presence of Mn2+ rather than Mg2+. We also show that SPAK activity is markedly inhibited by staurosporine and K252a, partially inhibited by N-ethylmaleimide and diamide, and unaffected by arsenite. OSR1, a kinase closely related to SPAK, exhibited similar kinase properties and similar functional activation of NKCC1 when coexpressed with WNK4.
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Affiliation(s)
- Kenneth B E Gagnon
- Department of Anesthesiology, Vanderbilt University Medical Center, T-4202 Medical Center North, 1161 21st Avenue South, Nashville, Tennessee 37232, USA
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225
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de los Heros P, Kahle KT, Rinehart J, Bobadilla NA, Vázquez N, San Cristobal P, Mount DB, Lifton RP, Hebert SC, Gamba G. WNK3 bypasses the tonicity requirement for K-Cl cotransporter activation via a phosphatase-dependent pathway. Proc Natl Acad Sci U S A 2006; 103:1976-81. [PMID: 16446421 PMCID: PMC1413675 DOI: 10.1073/pnas.0510947103] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
SLC12A cation/Cl- cotransporters are mutated in human disease, are targets of diuretics, and are collectively involved in the regulation of cell volume, neuronal excitability, and blood pressure. This gene family has two major branches with different physiological functions and inverse regulation: K-Cl cotransporters (KCC1-KCC4) mediate cellular Cl- efflux, are inhibited by phosphorylation, and are activated by dephosphorylation; Na-(K)-Cl cotransporters (NCC and NKCC1/2) mediate cellular Cl- influx and are activated by phosphorylation. A single kinase/phosphatase pathway is thought to coordinate the activities of these cotransporters in a given cell; however, the mechanisms involved are as yet unknown. We previously demonstrated that WNK3, a paralog of serine-threonine kinases mutated in hereditary hypertension, is coexpressed with several cation/Cl- cotransporters and regulates their activity. Here, we show that WNK3 completely prevents the cell swelling-induced activation of KCC1-KCC4 in Xenopus oocytes. In contrast, catalytically inactive WNK3 abolishes the cell shrinkage-induced inhibition of KCC1-KCC4, resulting in a >100-fold stimulation of K-Cl cotransport during conditions in which transport is normally inactive. This activation is completely abolished by calyculin A and cyclosporine A, inhibitors of protein phosphatase 1 and 2B, respectively. Wild-type WNK3 activates Na-(K)-Cl cotransporters by increasing their phosphorylation, and catalytically inactive kinase inhibits Na-(K)-Cl cotransporters by decreasing their phosphorylation, such that our data suggest that WNK3 is a crucial component of the kinase/phosphatase signaling pathway that coordinately regulates the Cl- influx and efflux branches of the SLC12A cotransporter family.
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Affiliation(s)
- Paola de los Heros
- *Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14000, Mexico
| | - Kristopher T. Kahle
- Department of Genetics and
- Molecular and Cellular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510; and
| | | | - Norma A. Bobadilla
- *Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14000, Mexico
| | - Norma Vázquez
- *Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14000, Mexico
| | - Pedro San Cristobal
- *Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14000, Mexico
| | - David B. Mount
- Renal Division, Brigham and Women’s Hospital and Division of General Internal Medicine, Veterans Affairs Boston Healthcare System, Harvard Medical School, Boston, MA 02115
| | | | - Steven C. Hebert
- Molecular and Cellular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510; and
| | - Gerardo Gamba
- *Molecular Physiology Unit, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán and Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Tlalpan, Mexico City, 14000, Mexico
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226
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Gamba G. TRPV4: a new target for the hypertension-related kinases WNK1 and WNK4. Am J Physiol Renal Physiol 2006; 290:F1303-4. [PMID: 16467131 DOI: 10.1152/ajprenal.00030.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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227
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Abstract
The epithelial tight junction (TJ) has three major functions. As a "gate," it serves as a regulatory barrier separating and maintaining biological fluid compartments of different composition. As a "fence," it generates and maintains the apicobasal polarity of cells that form the confluent epithelium. Finally, the TJ proteins form a trafficking and signaling platform that regulates cell growth, proliferation, differentiation, and dedifferentiation. Six examples are selected that illustrate the emerging link between TJ dysfunction and kidney disease. First, the glomerular slit diaphragm (GSD) is evolved, in part, from the TJ and, on maturation, exhibits all three functions of the TJ. GSD dysfunction leads to proteinuria and, in some instances, podocyte dedifferentiation and proliferation. Second, accumulating evidence supports epithelial-mesenchymal transformation (EMT) as a major player in renal fibrosis, the final common pathway that leads to end-stage renal failure. EMT is characterized by a loss of cell-cell contact and apicobasal polarity, which are hallmarks of TJ dysfunction. Third, in autosomal dominant polycystic kidney disease, mutations of the polycystins may disrupt their known interactions with the apical junction complex, of which the TJ is a major component. This can lead to disturbances in epithelial polarity regulation with consequent abnormal tubulogenesis and cyst formation. Fourth, evidence for epithelial barrier and polarity dysregulation in the pathogenesis of ischemic acute renal failure will be summarized. Fifth, the association between mutations of paracellin-1, the first TJ channel identified, and clinical disorders of magnesium and calcium wasting and bovine renal fibrosis will be used to highlight an integral TJ protein that can serve multiple TJ functions. Finally, the role of WNK4 protein kinase in shunting chloride across the TJ of the distal nephron will be addressed.
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Affiliation(s)
- David B N Lee
- Division of Nephrology, Veterans Affairs Greater Los Angeles Healthcare System, California, USA.
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228
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Capasso G, Cantone A, Evangelista C, Zacchia M, Trepiccione F, Acone D, Rizzo M. Channels, carriers, and pumps in the pathogenesis of sodium-sensitive hypertension. Semin Nephrol 2006; 25:419-24. [PMID: 16298266 DOI: 10.1016/j.semnephrol.2005.05.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sodium-sensitive hypertension is thought to be dependent on primary alterations in renal tubular sodium reabsorption. The major apical plasma membrane Na(+) transporters include the proximal tubular Na(+)-H(+) exchanger, the thick ascending limb Na(+)-K(+)-2Cl(-) cotransport system, the distal tubular Na(+)-Cl(-) cotransporter, and the collecting duct epithelial sodium channel (ENaC). This article explores the role of each transporter in the pathogenesis of hypertension. Although the contribution of the proximal tubule Na(+)-H(+) exchanger is not yet defined completely, more convincing data have been generated about the importance of the Na(+)-K(+)-2Cl(-). Indeed at least 2 forms of hypertension appear to be related to the up-regulation of the transporter: the so-called programmed hypertension induced by low-protein diet during pregnancy and the early phase of hypertension in the Milan strain of rats. With respect to the Na(+)-Cl(-) cotransporter this may be overactive caused by inactivating mutation of WNK4 as in the Gordon syndrome, although it is the main actor for the maintenance phase of the hypertension found in the Milan strain of rats. Finally, the contribution of the ENaC has been established clearly; indeed, in the Liddle syndrome the mutation of the ENaC gene leads to a longer retention of the channel on the cell surface of collecting duct principal cells, thus inducing stronger sodium reabsorption along this segment. All these examples clearly indicate that renal sodium transporters may be responsible for various types of sodium-sensitive hypertension.
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Affiliation(s)
- Giovambattista Capasso
- Department of Nephrology and Research Center for Cardiovascular Diseases, Faculty of Medicine, Second University of Napoli, Napoli, Italy.
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229
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Lazrak A, Liu Z, Huang CL. Antagonistic regulation of ROMK by long and kidney-specific WNK1 isoforms. Proc Natl Acad Sci U S A 2006; 103:1615-20. [PMID: 16428287 PMCID: PMC1360592 DOI: 10.1073/pnas.0510609103] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
WNK kinases are serine-threonine kinases with an atypical placement of the catalytic lysine. Intronic deletions with increased expression of a ubiquitous long WNK1 transcript cause pseudohypoaldosteronism type 2 (PHA II), characterized by hypertension and hyperkalemia. Here, we report that long WNK1 inhibited ROMK1 by stimulating its endocytosis. Inhibition of ROMK by long WNK1 was synergistic with, but not dependent on, WNK4. A smaller transcript of WNK1 lacking the N-terminal 1-437 amino acids is expressed highly in the kidney. Whether expression of the KS-WNK1 (kidney-specific, KS) is altered in PHA II is not known. We found that KS-WNK1 did not inhibit ROMK1 but reversed the inhibition of ROMK1 caused by long WNK1. Consistent with the lack of inhibition by KS-WNK1, we found that amino acids 1-491 of the long WNK1 were sufficient for inhibiting ROMK. Dietary K(+) restriction decreases ROMK abundance in the renal cortical-collecting ducts by stimulating endocytosis, an adaptative response important for conservation of K(+) during K(+) deficiency. We found that K(+) restriction in rats increased whole-kidney transcript of long WNK1 while decreasing that of KS-WNK1. Thus, KS-WNK1 is a physiological antagonist of long WNK1. Hyperkalemia in PHA II patients with PHA II mutations may be caused, at least partially, by increased expression of long WNK1 with or without decreased expression of KS-WNK1.
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Affiliation(s)
- Ahmed Lazrak
- Department of Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8856, USA
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230
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Hong-Hermesdorf A, Brüx A, Grüber A, Grüber G, Schumacher K. A WNK kinase binds and phosphorylates V-ATPase subunit C. FEBS Lett 2006; 580:932-9. [PMID: 16427632 DOI: 10.1016/j.febslet.2006.01.018] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Revised: 12/14/2005] [Accepted: 01/04/2006] [Indexed: 10/25/2022]
Abstract
WNK (with no lysine (K)) protein kinases are found in many eukaryotes and share a unique active site. Here, we report that a member of the Arabidopsis WNK family (AtWNK8) interacts with subunit C of the vacuolar H+-ATPase (V-ATPase) via a short C-terminal domain. AtWNK8 is shown to autophosphorylate intermolecularly and to phosphorylate Arabidopsis subunit C (AtVHA-C) at multiple sites as determined by MALDI-TOF MS analysis. Furthermore, we show that AtVHA-C and other V-ATPase subunits are phosphorylated when V1-complexes are used as substrates for AtWNK8. Taken together, our results provide evidence that V-ATPases are potential targets of WNK kinases and their associated signaling pathways.
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Affiliation(s)
- Anne Hong-Hermesdorf
- Universität Tübingen, ZMBP-Plant Physiology, Auf der Morgenstelle 1, 72076 Tübingen, Germany
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231
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Fu Y, Subramanya A, Rozansky D, Cohen DM. WNK kinases influence TRPV4 channel function and localization. Am J Physiol Renal Physiol 2006; 290:F1305-14. [PMID: 16403833 DOI: 10.1152/ajprenal.00391.2005] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
TRPV4, a renally expressed nonselective cation channel of the transient receptor potential (TRP) family, is gated by hypotonicity. Kinases of the WNK family influence expression and function of the thiazide-sensitive Na+-Cl- cotransporter, and monogenic human hypertension has been linked to mutations in the gene coding for WNK4. Along with TRPV4, WNK isoforms are highly expressed in the distal nephron. We show here that coexpression of WNK4 downregulates TRPV4 function in human embryonic kidney (HEK-293) cells and that this effect is mediated via decreased cell surface expression of TRPV4; total abundance of TRPV4 in whole cell lysates is unaffected. The effect of the related kinase WNK1 on TRPV4 function and surface expression was similar to that of WNK4. Disease-causing point mutations in WNK4 abrogate, but do not eliminate, the inhibitory effect on TRPV4 function. In contrast to wild-type WNK4, a kinase-dead WNK4 point mutant failed to influence TRPV4 trafficking; however, deletion of the entire WNK4 kinase domain did not blunt the effect of WNK4 on localization of TRPV4. Deletion of the extreme COOH-terminal putative coiled-coil domain of WNK4 abolished its effect. In immunoprecipitation experiments, we were unable to detect direct interaction between TRPV4 and either WNK kinase. In aggregate, these data indicate that TRPV4 is functionally regulated by WNK family kinases at the level of cell surface expression. Because TRPV4 and WNK kinases are coexpressed in the distal nephron in vivo and because there is a tendency toward hypercalcemia in TRPV4-/- mice, we speculate that this pathway may impact systemic Ca2+ balance. In addition, because WNK kinases and TRPV4 are activated by anisotonicity, they may comprise elements of an osmosensing or osmotically responsive signal transduction cascade in the distal nephron.
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Affiliation(s)
- Yi Fu
- Department of Medicine, Oregon Health & Science Univ., Portland, USA
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232
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Gagnon KBE, England R, Delpire E. Volume sensitivity of cation-Cl- cotransporters is modulated by the interaction of two kinases: Ste20-related proline-alanine-rich kinase and WNK4. Am J Physiol Cell Physiol 2006; 290:C134-42. [PMID: 15930150 DOI: 10.1152/ajpcell.00037.2005] [Citation(s) in RCA: 227] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present study, we have demonstrated functional interaction between Ste20-related proline-alanine-rich kinase (SPAK), WNK4 [with no lysine (K)], and the widely expressed Na+-K+-2Cl- cotransporter type 1 (NKCC1). NKCC1 function, which we measured in Xenopus laevis oocytes under both isosmotic (basal) and hyperosmotic (stimulated) conditions, was unaffected when SPAK and WNK4 were expressed alone. In contrast, expression of both kinases with NKCC1 resulted in a significant increase in cotransporter activity and an insensitivity to external osmolarity or cell volume. NKCC1 activation is dependent on the catalytic activity of SPAK and likely also of WNK4, because mutations in their catalytic domains result in an absence of cotransporter stimulation. The results of our yeast two-hybrid experiments suggest that WNK4 does not interact directly with NKCC1 but does interact with SPAK. Functional experiments demonstrated that the binding of SPAK to WNK4 was also required because a SPAK-interaction-deficient WNK4 mutant (Phe997Ala) did not increase NKCC1 activity. We also have shown that the transport function of K+-Cl- cotransporter type 2 (KCC2), a neuron-specific KCl cotransporter, was diminished by the expression of both kinases under both isosmotic and hyposmotic conditions. Our data are consistent with WNK4 interacting with SPAK, which in turn phosphorylates and activates NKCC1 and phosphorylates and deactivates KCC2.
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Affiliation(s)
- Kenneth B E Gagnon
- Dept. of Anesthesiology, Vanderbilt Univ. Medical Center, T-4202 Medical Center North, 1161 21st Ave. South, Nashville, TN 37232, USA
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233
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Abstract
This brief review attempts to provide an overview regarding recent developments in the regulation of ROMK channels. Studies performed in ROMK null mice suggest that ROMK cannot only form hometetramers such as the small-conductance (30-pS) K channels but also construct heterotetramers such as the 70-pS K channel in the thick ascending limb (TAL). The expression of ROMK channels in the plasma membrane is regulated by protein tyrosine kinase (PTK), serum and glucorticoid-induced kinase (SGK), and with-no-lysine-kinase 4. PTK is involved in mediating the effect of low K intake on ROMK channel activity. Increases in superoxide anions induced by low dietary K intake are responsible for the stimulation of PTK expression and tyrosine phosphorylation of ROMK channels. Finally, a recent study indicated that ROMK channels can be monoubiquitinated and monoubiquitination regulates the surface expression of ROMK channels.
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Affiliation(s)
- Wen-Hui Wang
- Dept. of Pharmacology, New York Medical College, Valhalla, NY 10595, USA.
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Maitland-van der Zee AH, Turner ST, Schwartz GL, Chapman AB, Klungel OH, Boerwinkle E. A multilocus approach to the antihypertensive pharmacogenetics of hydrochlorothiazide. Pharmacogenet Genomics 2005; 15:287-93. [PMID: 15864129 DOI: 10.1097/01213011-200505000-00003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To assess the influence of variations in multiple candidate genes on inter-individual variation in diastolic blood pressure (DBP) response to hydrochlorothiazide. METHODS A community-based sample of 585 adults with essential hypertension underwent monotherapy with hydrochlorothiazide for 4 weeks. In a nested case-control design, 195 individuals in the highest tertile of DBP response (responders) and 195 individuals in the lowest tertile of DBP response (non-responders) were genotyped for 45 polymorphisms in 19 candidate genes. For those polymorphisms where the set association approach found to be significantly associated with DBP response, logistic regression was performed to estimate the odds ratio (OR) for response associated variation in the identified genotype/haplotype. RESULTS Two polymorphisms in the sodium channel gamma-subunit promotor gene, and a polymorphism in the endothelial nitric oxide synthase gene, were significantly associated with blood pressure response to hydrochlorothiazide. In the final experiment for the set association model P=0.038. In the logistic regression analyses, compared to subjects with the CT/CT haplotype of the SCNN1G gene, those with the GA/GA haplotype had OR 5.21 of being a DBP responder [95% CI 1.65-16.47]. Compared to subjects with the GT genotype of the ENOSA_rs1799983 polymorphism, those with the GG genotype had an OR 2.19 of being a DBP responder [95% CI 1.27-3.77]. CONCLUSIONS Two polymorphisms in the sodium channel gamma-subunit promotor gene, and a polymorphism in the endothelial nitric oxide synthase gene, were associated with significant differences in odds of DBP response to hydrochlorothiazide. Follow-up studies are needed to define the functional genetic variations and their mechanisms of pharmacogenetic effects.
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235
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Leng Q, Kahle KT, Rinehart J, MacGregor GG, Wilson FH, Canessa CM, Lifton RP, Hebert SC. WNK3, a kinase related to genes mutated in hereditary hypertension with hyperkalaemia, regulates the K+ channel ROMK1 (Kir1.1). J Physiol 2005; 571:275-86. [PMID: 16357011 PMCID: PMC1796803 DOI: 10.1113/jphysiol.2005.102202] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The serine-threonine kinase WNK3 modulates Cl- transport into and out of cells through its regulation of SLC12A cation/Cl- cotransporters, implicating it as (one of) the long-sought Cl-/volume-sensitive kinase(s). Integrators in homeostatic systems regulate structurally diverse but functionally coupled elements. For example, the related kinase WNK4 regulates the Na-Cl co-transporter (NCC), paracellular Cl- flux, and the K+ channel ROMK1 (Kir1.1) to maintain renal NaCl and K+ homeostasis; mutations in PRKWNK4, encoding WNK4, cause a Mendelian disease featuring hypertension and hyperkalemia. It is known that WNK3 is expressed in the nephron's distal convoluted tubule (DCT) and stimulates NCC activity. Here, we show that WNK3 is also expressed in cortical and outer medullary collecting duct principal cells. Accordingly, we tested WNK3's effect on the mediators of NaCl and K+ handling in these nephron segments--the epithelial sodium channel (ENaC), paracellular Cl- flux, and ROMK1--using established model systems. WNK3 did not alter paracellular Cl- flux in tetracycline-responsive MDCK II cells, nor affect amiloride-sensitive currents when co-expressed with ENaC in Xenopus laevis oocytes. However, additional co-expression studies in oocytes revealed WNK3 inhibited the renal-specific K+ channel ROMK1 activity greater than 5.5-fold (p < .0001) by altering its plasmalemmal surface expression; WNK3 did not affect ROMK1's conductance or open/closed probability. In contrast, WNK3 had no effect on the activity of the cardiac long-QT syndrome K+ channel KCNQ1/KCNE1 when co-expressed in oocytes. Inhibition of ROMK1 is independent of WNK3's catalytic activity and is mediated by WNK3's carboxyl terminus--a mechanism distinct from its known kinase-dependent activation of NCC. A kinase-inactivating point mutation, or a missense mutation homologous to one in WNK4 that causes disease produced a gain-of-function effect, enhancing WNK3's inhibition of ROMK1 greater than 2.5-fold relative to wild type kinase (p < .0001). The magnitude and specificity of WNK3's effects at both NCC and ROMK1, its co-expression with its targets in the distal nephron, and the established in vivo effect of WNK4 at these same targets provide evidence that WNK3's action is physiologically relevant. WNK3 is likely a component of one of the mechanisms that determines the balance between renal NaCl reabsorption and K+ secretion.
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Affiliation(s)
- Qiang Leng
- Department of Molecular and Cellular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
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Moriguchi T, Urushiyama S, Hisamoto N, Iemura SI, Uchida S, Natsume T, Matsumoto K, Shibuya H. WNK1 Regulates Phosphorylation of Cation-Chloride-coupled Cotransporters via the STE20-related Kinases, SPAK and OSR1. J Biol Chem 2005; 280:42685-93. [PMID: 16263722 DOI: 10.1074/jbc.m510042200] [Citation(s) in RCA: 375] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The WNK1 and WNK4 genes have been found to be mutated in some patients with hyperkalemia and hypertension caused by pseudohypoaldosteronism type II. The clue to the pathophysiology of pseudohypoaldosteronism type II was its striking therapeutic response to thiazide diuretics, which are known to block the sodium chloride cotransporter (NCC). Although this suggests a role for WNK1 in hypertension, the precise molecular mechanisms are largely unknown. Here we have shown that WNK1 phosphorylates and regulates the STE20-related kinases, Ste20-related proline-alanine-rich kinase (SPAK) and oxidative stress response 1 (OSR1). WNK1 was observed to phosphorylate the evolutionary conserved serine residue located outside the kinase domains of SPAK and OSR1, and mutation of the OSR1 serine residue caused enhanced OSR1 kinase activity. In addition, hypotonic stress was shown to activate SPAK and OSR1 and induce phosphorylation of the conserved OSR1 serine residue, suggesting that WNK1 may be an activator of the SPAK and OSR1 kinases. Moreover, SPAK and OSR1 were found to directly phosphorylate the N-terminal regulatory regions of cation-chloride-coupled cotransporters including NKCC1, NKCC2, and NCC. Phosphorylation of NCC was induced by hypotonic stress in cells. These results suggested that WNK1 and SPAK/OSR1 mediate the hypotonic stress signaling pathway to the transporters and may provide insights into the mechanisms by which WNK1 regulates ion balance.
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Affiliation(s)
- Tetsuo Moriguchi
- Department of Molecular Cell Biology, Medical Research Institute and School of Biomedical Science, Tokyo Medical and Dental University, and CREST, JST, Chiyoda, Tokyo 101-0062
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237
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Zhang H, Staessen JA. Association of Blood Pressure With Genetic Variation inWNKKinases in a White European Population. Circulation 2005; 112:3371-2. [PMID: 16316962 DOI: 10.1161/circulationaha.105.585737] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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238
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Tobin MD, Raleigh SM, Newhouse S, Braund P, Bodycote C, Ogleby J, Cross D, Gracey J, Hayes S, Smith T, Ridge C, Caulfield M, Sheehan NA, Munroe PB, Burton PR, Samani NJ. Association of WNK1 gene polymorphisms and haplotypes with ambulatory blood pressure in the general population. Circulation 2005; 112:3423-9. [PMID: 16301342 DOI: 10.1161/circulationaha.105.555474] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Blood pressure (BP) is a heritable trait of major public health concern. The WNK1 and WNK4 genes, which encode proteins in the WNK family of serine-threonine kinases, are involved in renal electrolyte homeostasis. Mutations in the WNK1 and WNK4 genes cause a rare monogenic hypertensive syndrome, pseudohypoaldosteronism type II. We investigated whether polymorphisms in these WNK genes influence BP in the general population. METHODS AND RESULTS Associations between 9 single-nucleotide polymorphisms (SNPs) in WNK1 and 1 in WNK4 with ambulatory BP were studied in a population-based sample of 996 subjects from 250 white European families. The heritability estimates of mean 24-hour systolic BP (SBP) and diastolic BP (DBP) were 63.4% and 67.9%, respectively. We found statistically significant (P<0.05) associations of several common SNPs and haplotypes in WNK1 with mean 24-hour SBP and/or DBP. The minor allele (C) of rs880054, with a frequency of 44%, reduced mean 24-hour SBP and DBP by 1.37 (95% confidence interval, -2.45 to -0.23) and 1.14 (95% confidence interval, -1.93 to -0.38) mm Hg, respectively, per copy of the allele. CONCLUSIONS Common variants in WNK1 contribute to BP variation in the general population. This study shows that a gene causing a rare monogenic form of hypertension also plays a significant role in BP regulation in the general population. The findings provide a basis to identify functional variants of WNK1, elucidate any interactions of these variants with dietary intake or with response to antihypertensive drugs, and determine their impact on cardiovascular morbidity and mortality.
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Affiliation(s)
- Martin D Tobin
- Department of Health Sciences, University of Leicester, Leicester, England
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Rinehart J, Kahle KT, de Los Heros P, Vazquez N, Meade P, Wilson FH, Hebert SC, Gimenez I, Gamba G, Lifton RP. WNK3 kinase is a positive regulator of NKCC2 and NCC, renal cation-Cl- cotransporters required for normal blood pressure homeostasis. Proc Natl Acad Sci U S A 2005; 102:16777-82. [PMID: 16275913 PMCID: PMC1283841 DOI: 10.1073/pnas.0508303102] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
WNK1 and WNK4 [WNK, with no lysine (K)] are serine-threonine kinases that function as molecular switches, eliciting coordinated effects on diverse ion transport pathways to maintain homeostasis during physiological perturbation. Gain-of-function mutations in either of these genes cause an inherited syndrome featuring hypertension and hyperkalemia due to increased renal NaCl reabsorption and decreased K(+) secretion. Here, we reveal unique biochemical and functional properties of WNK3, a related member of the WNK kinase family. Unlike WNK1 and WNK4, WNK3 is expressed throughout the nephron, predominantly at intercellular junctions. Because WNK4 is a potent inhibitor of members of the cation-cotransporter SLC12A family, we used coexpression studies in Xenopus oocytes to investigate the effect of WNK3 on NCC and NKCC2, related kidney-specific transporters that mediate apical NaCl reabsorption in the thick ascending limb and distal convoluted tubule, respectively. In contrast to WNK4's inhibitory activity, kinase-active WNK3 is a potent activator of both NKCC2 and NCC-mediated transport. Conversely, in its kinase-inactive state, WNK3 is a potent inhibitor of NKCC2 and NCC activity. WNK3 regulates the activity of these transporters by altering their expression at the plasma membrane. Wild-type WNK3 increases and kinase-inactive WNK3 decreases NKCC2 phosphorylation at Thr-184 and Thr-189, sites required for the vasopressin-mediated plasmalemmal translocation and activation of NKCC2 in vivo. The effects of WNK3 on these transporters and their coexpression in renal epithelia implicate WNK3 in NaCl, water, and blood pressure homeostasis, perhaps via signaling downstream of vasopressin.
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Affiliation(s)
- Jesse Rinehart
- Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
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240
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Kahle KT, Rinehart J, de Los Heros P, Louvi A, Meade P, Vazquez N, Hebert SC, Gamba G, Gimenez I, Lifton RP. WNK3 modulates transport of Cl- in and out of cells: implications for control of cell volume and neuronal excitability. Proc Natl Acad Sci U S A 2005; 102:16783-8. [PMID: 16275911 PMCID: PMC1283843 DOI: 10.1073/pnas.0508307102] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The regulation of Cl(-) transport into and out of cells plays a critical role in the maintenance of intracellular volume and the excitability of GABA responsive neurons. The molecular determinants of these seemingly diverse processes are related ion cotransporters: Cl(-) influx is mediated by the Na-K-2Cl cotransporter NKCC1 and Cl(-) efflux via K-Cl cotransporters, KCC1 or KCC2. A Cl(-)/volume-sensitive kinase has been proposed to coordinately regulate these activities via altered phosphorylation of the transporters; phosphorylation activates NKCC1 while inhibiting KCCs, and dephosphorylation has the opposite effects. We show that WNK3, a member of the WNK family of serine-threonine kinases, colocalizes with NKCC1 and KCC1/2 in diverse Cl(-)-transporting epithelia and in neurons expressing ionotropic GABA(A) receptors in the hippocampus, cerebellum, cerebral cortex, and reticular activating system. By expression studies in Xenopus oocytes, we show that kinase-active WNK3 increases Cl(-) influx via NKCC1, and that it inhibits Cl(-) exit through KCC1 and KCC2; kinase-inactive WNK3 has the opposite effects. WNK3's effects are imparted via altered phosphorylation and surface expression of its downstream targets and bypass the normal requirement of altered tonicity for activation of these transporters. Together, these data indicate that WNK3 can modulate the level of intracellular Cl(-) via opposing actions on entry and exit pathways. They suggest that WNK3 is part of the Cl(-)/volume-sensing mechanism necessary for the maintenance of cell volume during osmotic stress and the dynamic modulation of GABA neurotransmission.
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Affiliation(s)
- Kristopher T Kahle
- Department of Genetics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
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241
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Hadchouel J, Delaloy C, Fauré S, Achard JM, Jeunemaitre X. Familial Hyperkalemic Hypertension. J Am Soc Nephrol 2005; 17:208-17. [PMID: 16221868 DOI: 10.1681/asn.2005030314] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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242
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Subramanya AR, Yang CL, Zhu X, Ellison DH. Dominant-negative regulation of WNK1 by its kidney-specific kinase-defective isoform. Am J Physiol Renal Physiol 2005; 290:F619-24. [PMID: 16204408 DOI: 10.1152/ajprenal.00280.2005] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
With-no-lysine kinase-1 (WNK1) gene mutations cause familial hyperkalemic hypertension (FHHt), a Mendelian disorder of excessive renal Na+ and K+ retention. Through its catalytic activity, full-length kinase-sufficient WNK1 (L-WNK1) suppresses its paralog, WNK4, thereby upregulating thiazide-sensitive Na-Cl cotransporter (NCC) activity. The predominant renal WNK1 isoform, KS-WNK1, expressed exclusively and at high levels in distal nephron, is a shorter kinase-defective product; the function of KS-WNK1 must therefore be kinase independent. Here, we report a novel role for KS-WNK1 as a dominant-negative regulator of L-WNK1. Na+ transport studies in Xenopus laevis oocytes demonstrate that KS-WNK1 downregulates NCC activity indirectly, by inhibiting L-WNK1. KS-WNK1 also associates with L-WNK1 in protein complexes in oocytes and attenuates L-WNK1 kinase activity in vitro. These observations suggest that KS-WNK1 plays an essential role in the renal molecular switch regulating Na+ and K+ balance; they provide insight into the kidney-specific phenotype of FHHt.
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Affiliation(s)
- Arohan R Subramanya
- Division of Nephrology and Hypertension, Oregon Health and Science University, PP262, 3314 SW US Veterans Hospital Road, Portland, OR 97239, USA
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243
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Abstract
PURPOSE OF REVIEW A variety of K+ channels have been identified with the patch-clamp technique and molecular cloning in the kidney. However, it is still a challenging task to determine the location and function of the cloned K+ channels in the corresponding nephron segment. The aim of the present review is to update the recent developments regarding the location and function of the cloned K+ channels in the native tubule. Also, the review describes the new regulatory mechanism of renal outer-medullary K (ROMK) channels and the role of Ca(2+)-activated maxi K+ channels in flow-dependent K+ secretion. RECENT FINDINGS Several types of voltage-gated K+ (Kv) channel, such as KCNQ1, KCNA10 and Kv1.3, are highly expressed at the apical membrane of proximal tubules and distal tubules. They may participate in stabilizing the cell membrane potential. Moreover, studies performed in ROMK-knockout mice have shown that the apical 70 pS K+ channel is absent in the thick ascending limb in these mice, suggesting that the ROMK channel is also involved in forming the apical 70 pS K+ channel in the thick ascending limb. Three important kinases, protein tyrosine kinase, serum- and glucocorticoid-inducible kinase and with-no-lysine kinase, have been suggested to regulate the ROMK channel density in the cortical collecting duct. Low K+ intake increases protein tyrosine kinase expression and tyrosine phosphorylation of ROMK channels. Coexpression of with-no-lysine kinase with the ROMK channel decreases K+ current whereas serum- and glucocorticoid-inducible kinase 1 stimulates the ROMK current in oocytes in the presence of Na/H exchanger regulatory factor 2. The Ca-activated maxi K+ channel has been shown to be activated by an increase in flow rate in the rabbit cortical collecting duct. SUMMARY The voltage-gated K+ channels are expressed in a variety of nephron segments and play a role in stabilization of cell membrane potential. With-no-lysine kinase and serum- and glucocorticoid-inducible kinase 1 have been shown to regulate ROMK1 channels. Protein tyrosine kinase mediates the effect of K+ intake on K+ secretion by stimulation of tyrosine phosphorylation of ROMK1 channels. The Ca-activated maxi K+ channel plays a role in flow-dependent K+ secretion in the distal nephron.
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Affiliation(s)
- WenHui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA.
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Le Moellic C, Boulkroun S, González-Nunez D, Dublineau I, Cluzeaud F, Fay M, Blot-Chabaud M, Farman N. Aldosterone and tight junctions: modulation of claudin-4 phosphorylation in renal collecting duct cells. Am J Physiol Cell Physiol 2005; 289:C1513-21. [PMID: 16107502 DOI: 10.1152/ajpcell.00314.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aldosterone classically modulates Na transport in tight epithelia such as the renal collecting duct (CD) through the transcellular route, but it is not known whether the hormone could also affect paracellular permeability. Such permeability is controlled by tight junctions (TJ) that form a size- and charge-selective barrier. Among TJ proteins, claudin-4 has been highlighted as a key element to control paracellular charge selectivity. In RCCD2 CD cells grown on filters, we have identified novel early aldosterone effects on TJ. Endogenous claudin-4 abundance and cellular localization were unaltered by aldosterone. However, the hormone promoted rapid (within 15-20 min) and transient phosphorylation of endogenous claudin-4 on threonine residues, without affecting tyrosine or serine; this event was fully developed at 10 nM aldosterone and appeared specific for aldosterone (because it is not observed after dexamethasone treatment and it depends on mineralocorticoid receptor occupancy). Within the same delay, aldosterone also promoted an increased apical-to-basal passage of 125I (a substitute for 36Cl), whereas 22Na passage was unaffected; paracellular permeability to [3H]mannitol was also reduced. Later on (45 min), a fall in transepithelial resistance was observed. These data indicate that aldosterone modulates TJ properties in renal epithelial cells.
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Affiliation(s)
- Cathy Le Moellic
- INSERM U478, Faculté de Médecine Xavier Bichat, BP 416, 75870 Paris Cedex 18, France
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245
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Matayoshi T, Kamide K, Takiuchi S, Yoshii M, Miwa Y, Takami Y, Tanaka C, Banno M, Horio T, Nakamura S, Nakahama H, Yoshihara F, Inenaga T, Miyata T, Kawano Y. The thiazide-sensitive Na(+)-Cl(-) cotransporter gene, C1784T, and adrenergic receptor-beta3 gene, T727C, may be gene polymorphisms susceptible to the antihypertensive effect of thiazide diuretics. Hypertens Res 2005; 27:821-33. [PMID: 15824464 DOI: 10.1291/hypres.27.821] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The response of blood pressure to thiazide diuretics (TZDs) differs among individuals. The prediction of the antihypertensive effect of TZDs is important for realizing individualized therapy in the management of hypertension. The aim of this study was to identify the single nucleotide polymorphisms (SNPs) susceptible to the antihypertensive effect of TZDs, particularly focusing on genes related to water-electrolyte absorption in the kidney. Seventy-six outpatients (mean age, 65.4+/-9.0 years) with essential hypertension (EHT) taking TZDs were retrospectively assessed. We defined as responders (R) those whose mean blood pressure was lowered by more than 5 mmHg after the use of TZDs. Forty-eight SNPs in 17 genes (ADD1, GNB3, TSC [SLC12A3], MLR [NR3C2], NCX1 [SLC8A1], WNK1, WNK4, AGT, ACE, AT1 [AGTR1], CYP11B2, ADRB1, ADRB2, ADRB3, ADRA1A, ADRA1B, ADRA2A) were genotyped in the 76 patients. The SNPs in TSC, MLR, NCX1, WNK1, and WNK4 were identified by direct sequencing and those with minor frequencies of greater than 5% were genotyped in this study. The comparison of polymorphism prevalence between R and non-responders (NR) showed significant differences in TSC C1784T (C allele vs. T allele, odds ratio (OR)=3.81, p =0.016, confidence interval (CI): 1.25-11.63) and ADRB3 T727C (Trp64Arg) (T allele vs. C allele, OR=4.59, p =0.005, CI: 1.54-13.68). The blood pressure (BP) in patients homozygous for the major alleles of both TSC C1784T and ADRB3 T727C were significantly reduced by TZD treatment; however, the BP in those homozygous for the minor allele and heterozygous (TSC C1784T: TT+CT; ADRB3 T727C: CC+CT) for both SNPs were not significantly changed after TZD treatment. Both newly detected TSC C1784T and ADRB3 T727C are gene polymorphisms susceptible to the antihypertensive effect of TZDs in patients with EHT. Thus, the prediction of BP reduction by TZDs may be possible by evaluating these two SNPs.
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Affiliation(s)
- Tetsutaro Matayoshi
- Division of Hypertension and Nephrology, National Cardiovascular Center, Suita, Japan
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246
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Xu BE, Stippec S, Chu PY, Lazrak A, Li XJ, Lee BH, English JM, Ortega B, Huang CL, Cobb MH. WNK1 activates SGK1 to regulate the epithelial sodium channel. Proc Natl Acad Sci U S A 2005; 102:10315-20. [PMID: 16006511 PMCID: PMC1177404 DOI: 10.1073/pnas.0504422102] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
WNK (with no lysine [K]) kinases are serine-threonine protein kinases with an atypical placement of the catalytic lysine. Intronic deletions increase the expression of WNK1 in humans and cause pseudohypoaldosteronism type II, a form of hypertension. WNKs have been linked to ion carriers, but the underlying regulatory mechanisms are unknown. Here, we report a mechanism for the control of ion permeability by WNK1. We show that WNK1 activates the serum- and glucocorticoid-inducible protein kinase SGK1, leading to activation of the epithelial sodium channel. Increased channel activity induced by WNK1 depends on SGK1 and the E3 ubiquitin ligase Nedd4-2. This finding provides compelling evidence that this molecular mechanism contributes to the pathogenesis of hypertension in pseudohypoaldosteronism type II caused by WNK1 and, possibly, in other forms of hypertension.
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Affiliation(s)
- Bing-e Xu
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, USA
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247
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Golbang AP, Murthy M, Hamad A, Liu CH, Cope G, Van't Hoff W, Cuthbert A, O'Shaughnessy KM. A new kindred with pseudohypoaldosteronism type II and a novel mutation (564D>H) in the acidic motif of the WNK4 gene. Hypertension 2005; 46:295-300. [PMID: 15998707 DOI: 10.1161/01.hyp.0000174326.96918.d6] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We identified a new kindred with the familial syndrome of hypertension and hyperkalemia (pseudohypoaldosteronism type II or Gordon's syndrome) containing an affected father and son. Mutation analysis confirmed a single heterozygous G to C substitution within exon 7 (1690G>C) that causes a missense mutation within the acidic motif of WNK4 (564D>H). We confirmed the function of this novel mutation by coexpressing it in Xenopus oocytes with either the NaCl cotransporter (NCCT) or the inwardly rectifying K-channel (ROMK). Wild-type WNK4 inhibits 22Na+ flux in Xenopus oocytes expressing NCCT by approximately 90% (P<0.001), whereas the 564D>H mutant had no significantly inhibitory effect on flux through NCCT. In oocytes expressing ROMK, wild-type WNK4 produced >50% inhibition of steady-state current through ROMK at a +20-mV holding potential (P<0.001). The 564D>H mutant produced further inhibition with steady-state currents to some 60% to 70% of those seen with the wild-type WNK4. Using fluorescent-tagged NCCT (enhanced cyan fluorescent protein-NCCT) and ROMK (enhanced green fluorescent protein-ROMK) to quantify the expression of the proteins in the oocyte membrane, it appears that the functional effects of the 564D>H mutation can be explained by alteration in the surface expression of NCCT and ROMK. Compared with wild-type WNK4, WNK4 564D>H causes increased cell surface expression of NCCT but reduced expression of ROMK. This work confirms that the novel missense mutation in WNK4, 564D>H, is functionally active and highlights further how switching charge on a single residue in the acid motif of WNK4 affects its interaction with the thiazide-sensitive target NCCT and the potassium channel ROMK.
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Affiliation(s)
- Amir P Golbang
- Clinical Pharmacology Unit, University of Cambridge, United Kingdom
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Yamauchi K, Yang SS, Ohta A, Sohara E, Rai T, Sasaki S, Uchida S. Apical localization of renal K channel was not altered in mutant WNK4 transgenic mice. Biochem Biophys Res Commun 2005; 332:750-5. [PMID: 15907795 DOI: 10.1016/j.bbrc.2005.04.169] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Accepted: 04/30/2005] [Indexed: 11/17/2022]
Abstract
Missense mutations in the WNK4 gene have been postulated to cause pseudohypoaldosteronism type II, an autosomal-dominant disorder characterized by hyperkalemia and hypertension. A previous study using Xenopus oocytes showed that wild-type WNK4 expression inhibited surface expression of renal K channel (ROMK) and that a disease-causing mutant further decreased the surface expression. The decreased surface expression of ROMK caused by mutant WNK4 was postulated to be a mechanism for decreased potassium secretion in distal nephrons that would presumably lead to hyperkalemia. To determine if the mutant WNK4 had such an inhibitory effect on the apical localization of ROMK in vivo, we generated transgenic mice using the CLCNKB gene promoter that expressed a mutant WNK4 (D564A) in distal nephrons. In contrast to the tight junction localization of wild-type WNK4 described previously, the mutant WNK4 was present in the cytoplasm in the distal tubules and in the apical membranes in the thick ascending limb of Henle's loop. In both cell types, the apical localization of endogenous ROMK was not influenced by the co-expression of mutant WNK4. This result indicates that the mutant WNK4 does not have a dominant effect on the cellular localization of ROMK in vivo.
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Affiliation(s)
- Kozue Yamauchi
- Department of Nephrology, Graduate School of Medicine, Tokyo Medical and Dental University, Japan
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Jiang ZY, Zhou QL, Holik J, Patel S, Leszyk J, Coleman K, Chouinard M, Czech MP. Identification of WNK1 as a Substrate of Akt/Protein Kinase B and a Negative Regulator of Insulin-stimulated Mitogenesis in 3T3-L1 Cells. J Biol Chem 2005; 280:21622-8. [PMID: 15799971 DOI: 10.1074/jbc.m414464200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin signaling through protein kinase Akt/protein kinase B (PKB), a downstream element of the phosphatidylinositol 3-kinase (PI3K) pathway, regulates diverse cellular functions including metabolic pathways, apoptosis, mitogenesis, and membrane trafficking. To identify Akt/PKB substrates that mediate these effects, we used antibodies that recognize phosphopeptide sites containing the Akt/PKB substrate motif (RXRXX(p)S/T) to immunoprecipitate proteins from insulin-stimulated adipocytes. Tryptic peptides from a 250-kDa immunoprecipitated protein were identified as the protein kinase WNK1 (with no lysine) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry, consistent with a recent report that WNK1 is phosphorylated on Thr60 in response to insulin-like growth factor I. Insulin treatment of 3T3-L1 adipocytes stimulated WNK1 phosphorylation, as detected by immunoprecipitation with antibody against WNK1 followed by immunoblotting with the anti-phosphoAkt substrate antibody. WNK1 phosphorylation induced by insulin was unaffected by rapamycin, an inhibitor of p70 S6 kinase pathway but abolished by the PI3K inhibitor wortmannin. RNA interference-directed depletion of Akt1/PKB alpha and Akt2/PKB beta attenuated insulin-stimulated WNK1 phosphorylation, but depletion of protein kinase C lambda did not. Whereas small interfering RNA-induced loss of WNK1 protein did not significantly affect insulin-stimulated glucose transport in 3T3-L1 adipocytes, it significantly enhanced insulin-stimulated thymidine incorporation by about 2-fold. Furthermore, depletion of WNK1 promoted serum-stimulated cell proliferation of 3T3-L1 preadipocytes, as evidenced by a 36% increase in cell number after 48 h in culture. These data suggest that WNK1 is a physiologically relevant target of insulin signaling through PI3K and Akt/PKB and functions as a negative regulator of insulin-stimulated mitogenesis.
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Affiliation(s)
- Zhen Y Jiang
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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Farfel Z, Mayan H, Yaacov Y, Mouallem M, Shaharabany M, Pauzner R, Kerem E, Wilschanski M. WNK4 regulates airway Na+ transport: study of familial hyperkalaemia and hypertension. Eur J Clin Invest 2005; 35:410-5. [PMID: 15948903 DOI: 10.1111/j.1365-2362.2005.01504.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND WNK [With No K (lysine)] kinases are essential for regulation of blood pressure and potassium homeostasis. WNK4 expression was recently found not only in the distal nephron but also in chloride-transporting epithelia. To establish a physiological role for this distribution we studied patients with familial hyperkalaemia and hypertension (FHH), [pseudohypoaldosteronism type II (PHAII)], which is caused by mutations in WNK4. DESIGN Measurement of nasal potential difference (NPD) and sweat electrolytes were performed in controls, in six subjects with FHH and ten subjects with cystic fibrosis (CF). RESULTS Basal NPD was higher in FHH compared with controls (n = 20): 22.8 +/- 5.7 vs. 16.2 +/- 5.3 mV, respectively (P = 0.014). Maximal response to amiloride was also higher in FHH compared with controls: 14.8 +/- 3.5 vs. 10.0 +/- 4.8 mV, respectively (P = 0.03). In CF these values were 42.9 +/- 9.3 and 29.9 +/- 7.4 mV, respectively. The kinetics of the amiloride effect were faster in FHH, and as first reported here also in CF, compared with controls. At 30 s, amiloride-inhibitable residual PD in FHH was 50 +/- 30 vs. 81 +/- 9% in controls (P = 0.0003) and 56 +/- 7% in CF. The response to chloride-free and isoproterenol solutions, which determines chloride transport activity, was similar in FHH compared with controls [16.0 +/- 8.6 vs. 10.4 +/- 5.9 mV (P = 0.08)]. Sweat conductivity in FHH was 49.7 +/- 7.3 vs. 38.2 +/- 8.1 mmol (NaCl eq) L-1 in 16 controls (P = 0.007) and 94.0 +/- 19.3 in CF. CONCLUSIONS Mutant WNK4 increases Na+ transport in airways, and therefore it is regulated by wild-type WNK4. This may be caused by a regulation of ENaC or a K+ channel.
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Affiliation(s)
- Z Farfel
- Department of Medicine, Tel Aviv University, Tel Aviv, Israel.
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