101
|
Eladari D, Chambrey R, Picard N, Hadchouel J. Electroneutral absorption of NaCl by the aldosterone-sensitive distal nephron: implication for normal electrolytes homeostasis and blood pressure regulation. Cell Mol Life Sci 2014; 71:2879-95. [PMID: 24556999 PMCID: PMC11113337 DOI: 10.1007/s00018-014-1585-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 01/28/2014] [Accepted: 02/05/2014] [Indexed: 01/10/2023]
Abstract
Sodium absorption by the distal part of the nephron, i.e., the distal convoluted tubule, the connecting tubule, and the collecting duct, plays a major role in the control of homeostasis by the kidney. In this part of the nephron, sodium transport can either be electroneutral or electrogenic. The study of electrogenic Na(+) absorption, which is mediated by the epithelial sodium channel (ENaC), has been the focus of considerable interest because of its implication in sodium, potassium, and acid-base homeostasis. However, recent studies have highlighted the crucial role played by electroneutral NaCl absorption in the regulation of the body content of sodium chloride, which in turn controls extracellular fluid volume and blood pressure. Here, we review the identification and characterization of the NaCl cotransporter (NCC), the molecule accounting for the main part of electroneutral NaCl absorption in the distal nephron, and its regulators. We also discuss recent work describing the identification of a novel "NCC-like" transport system mediated by pendrin and the sodium-driven chloride/bicarbonate exchanger (NDCBE) in the β-intercalated cells of the collecting system.
Collapse
Affiliation(s)
- Dominique Eladari
- Department of Physiology, Hopital Européen Georges Pompidou, AP-HP, 56 rue Leblanc, 75015, Paris, France,
| | | | | | | |
Collapse
|
102
|
Davies M, Fraser SA, Galic S, Choy SW, Katerelos M, Gleich K, Kemp BE, Mount PF, Power DA. Novel mechanisms of Na+ retention in obesity: phosphorylation of NKCC2 and regulation of SPAK/OSR1 by AMPK. Am J Physiol Renal Physiol 2014; 307:F96-F106. [PMID: 24808538 DOI: 10.1152/ajprenal.00524.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Enhanced tubular reabsorption of salt is important in the pathogenesis of obesity-related hypertension, but the mechanisms remain poorly defined. To identify changes in the regulation of salt transporters in the kidney, C57BL/6 mice were fed a 40% fat diet [high-fat diet (HFD)] or a 12% fat diet (control diet) for 14 wk. Compared with control diet-fed mice, HFD-fed mice had significantly greater elevations in weight, blood pressure, and serum insulin and leptin levels. When we examined Na(+) transporter expression, Na(+)-K(+)-2Cl(-) cotransporter (NKCC2) was unchanged in whole kidney and reduced in the cortex, Na(+)-Cl(-) cotransporter (NCC) and α-epithelial Na(+) channel (ENaC) and γ-ENaC were unchanged, and β-ENaC was reduced. Phosphorylation of NCC was unaltered. Activating phosphorylation of NKCC2 at S126 was increased 2.5-fold. Activation of STE-20/SPS1-related proline-alanine-rich protein kinase (SPAK)/oxidative stress responsive 1 kinase (OSR1) was increased in kidneys from HFD-fed mice, and enhanced phosphorylation of NKCC2 at T96/T101 was evident in the cortex. Increased activity of NKCC2 in vivo was confirmed with diuretic experiments. HFD-fed mice had reduced activating phosphorylation of AMP-activated protein kinase (AMPK) in the renal cortex. In vitro, activation of AMPK led to a reduction in phospho-SPAK/phospho-OSR1 in AMPK(+/+) murine embryonic fibroblasts (MEFs), but no effect was seen in AMPK(-/-) MEFs, indicating an AMPK-mediated effect. Activation of the with no lysine kinase/SPAK/OSR1 pathway with low-NaCl solution invoked a greater elevation in phospho-SPAK/phospho-OSR1 in AMPK(-/-) MEFs than in AMPK(+/+) MEFs, consistent with a negative regulatory effect of AMPK on SPAK/OSR1 phosphorylation. In conclusion, this study identifies increased phosphorylation of NKCC2 on S126 as a hitherto-unrecognized mediator of enhanced Na(+) reabsorption in obesity and identifies a new role for AMPK in regulating the activity of SPAK/OSR1.
Collapse
Affiliation(s)
- Matthew Davies
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia; Department of Nephrology, University of Melbourne, Heidelberg, Victoria, Australia; Department of Medicine, University of Melbourne, Heidelberg, Victoria, Australia; and
| | - Scott A Fraser
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia
| | - Sandra Galic
- St. Vincent's Institute, Fitzroy, Victoria, Australia
| | - Suet-Wan Choy
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia; Department of Nephrology, University of Melbourne, Heidelberg, Victoria, Australia; Department of Medicine, University of Melbourne, Heidelberg, Victoria, Australia; and
| | - Marina Katerelos
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia
| | - Kurt Gleich
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia
| | - Bruce E Kemp
- St. Vincent's Institute, Fitzroy, Victoria, Australia
| | - Peter F Mount
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia; Department of Nephrology, University of Melbourne, Heidelberg, Victoria, Australia; Department of Medicine, University of Melbourne, Heidelberg, Victoria, Australia; and
| | - David A Power
- Kidney Laboratory, Institute for Breathing and Sleep, University of Melbourne, Heidelberg, Victoria, Australia; Department of Nephrology, University of Melbourne, Heidelberg, Victoria, Australia; Department of Medicine, University of Melbourne, Heidelberg, Victoria, Australia; and
| |
Collapse
|
103
|
Fraser SA, Davies M, Katerelos M, Gleich K, Choy SW, Steel R, Galic S, Mount PF, Kemp BE, Power DA. Activation of AMPK reduces the co-transporter activity of NKCC1. Mol Membr Biol 2014; 31:95-102. [PMID: 24702155 DOI: 10.3109/09687688.2014.902128] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The co-transporter activity of Na(+)-K(+)-2Cl(-) 1 (NKCC1) is dependent on phosphorylation. In this study we show the energy-sensing kinase AMPK inhibits NKCC1 activity. Three separate AMPK activators (AICAR, Phenformin and A-769662) inhibited NKCC1 flux in a variety of nucleated cells. Treatment with A-769662 resulted in a reduction of NKCC1(T212/T217) phosphorylation, and this was reversed by treatment with the non-selective AMPK inhibitor Compound C. AMPK dependence was confirmed by treatment of AMPK null mouse embryonic fibroblasts, where A-769662 had no effect on NKCC1 mediated transport. AMPK was found to directly phosphorylate a recombinant human-NKCC1 N-terminal fragment (1-293) with the phosphorylated site identified as S77. Mutation of Serine 77 to Alanine partially prevented the inhibitory effect of A-769662 on NKCC1 activity. In conclusion, AMPK can act to reduce NKCC1-mediated transport. While the exact mechanism is still unclear there is evidence for both a direct effect on phosphorylation of S77 and reduced phosphorylation of T212/217.
Collapse
Affiliation(s)
- Scott A Fraser
- Institute for Breathing and Sleep, Kidney Laboratory , Melbourne, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
104
|
delos Heros P, Alessi D, Gourlay R, Campbell D, Deak M, Macartney T, Kahle K, Zhang J. The WNK-regulated SPAK/OSR1 kinases directly phosphorylate and inhibit the K+-Cl- co-transporters. Biochem J 2014; 458:559-73. [PMID: 24393035 PMCID: PMC3940040 DOI: 10.1042/bj20131478] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Precise homoeostasis of the intracellular concentration of Cl- is achieved via the co-ordinated activities of the Cl- influx and efflux. We demonstrate that the WNK (WNK lysine-deficient protein kinase)-activated SPAK (SPS1-related proline/alanine-rich kinase)/OSR1 (oxidative stress-responsive kinase 1) known to directly phosphorylate and stimulate the N[K]CCs (Na+-K+ ion co-transporters), also promote inhibition of the KCCs (K+-Cl- co-transporters) by directly phosphorylating a recently described C-terminal threonine residue conserved in all KCC isoforms [Site-2 (Thr1048)]. First, we demonstrate that SPAK and OSR1, in the presence of the MO25 regulatory subunit, robustly phosphorylates all KCC isoforms at Site-2 in vitro. Secondly, STOCK1S-50699, a WNK pathway inhibitor, suppresses SPAK/OSR1 activation and KCC3A Site-2 phosphorylation with similar efficiency. Thirdly, in ES (embryonic stem) cells lacking SPAK/OSR1 activity, endogenous phosphorylation of KCC isoforms at Site-2 is abolished and these cells display elevated basal activity of 86Rb+ uptake that was not markedly stimulated further by hypotonic high K+ conditions, consistent with KCC3A activation. Fourthly, a tight correlation exists between SPAK/OSR1 activity and the magnitude of KCC3A Site-2 phosphorylation. Lastly, a Site-2 alanine KCC3A mutant preventing SPAK/OSR1 phosphorylation exhibits increased activity. We also observe that KCCs are directly phosphorylated by SPAK/OSR1, at a novel Site-3 (Thr5 in KCC1/KCC3 and Thr6 in KCC2/KCC4), and a previously recognized KCC3-specific residue, Site-4 (Ser96). These data demonstrate that the WNK-regulated SPAK/OSR1 kinases directly phosphorylate the N[K]CCs and KCCs, promoting their stimulation and inhibition respectively. Given these reciprocal actions with anticipated net effects of increasing Cl- influx, we propose that the targeting of WNK-SPAK/OSR1 with kinase inhibitors might be a novel potent strategy to enhance cellular Cl- extrusion, with potential implications for the therapeutic modulation of epithelial and neuronal ion transport in human disease states.
Collapse
Key Words
- γ-aminobutyric acid (gaba)
- blood pressure/hypertension
- ion homoeostasis
- k+–cl− co-transporter 2 (kcc2)
- k+–cl− co-transporter 3 (kcc3)
- na+–cl− co-transporter (ncc)
- na+–k+–2cl− co-transporter 1 (nkcc1)
- protein kinase
- signal transduction
- ccc, cation–cl− co-transporter
- cct, conserved c-terminal
- ctd, c-terminal cytoplasmic domain
- erk1, extracellular-signal-regulated kinase 1
- es, embryonic stem
- hek, human embryonic kidney
- hrp, horseradish peroxidase
- kcc, k+–cl− co-transporter
- lds, lithium dodecyl sulfate
- ncc, na+–cl− co-transporter
- n[k]cc, na+–k+ ion co-transporter
- nkcc, na+–k+–2cl− co-transporter
- ntd, n-terminal cytoplasmic domain
- osr1, oxidative stress-responsive kinase 1
- slc12, solute carrier family 12
- spak, sps1-related proline/alanine-rich kinase
- ttbs, tris-buffered saline containing tween 20
- wnk, wnk lysine-deficient protein kinase
- xic, extracted ion chromatogram
Collapse
Affiliation(s)
- Paola delos Heros
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
| | - Dario R. Alessi
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
- 1Correspondence may be addressed to either of these authors (email or )
| | - Robert Gourlay
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
| | - David G. Campbell
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
| | - Maria Deak
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
| | - Thomas J. Macartney
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
| | - Kristopher T. Kahle
- †Department of Neurosurgery, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114, U.S.A
- ‡Manton Center for Orphan Disease Research, Children's Hospital Boston, Boston, MA 02115, U.S.A
| | - Jinwei Zhang
- *MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K
- 1Correspondence may be addressed to either of these authors (email or )
| |
Collapse
|
105
|
Rengarajan S, Lee DH, Oh YT, Delpire E, Youn JH, McDonough AA. Increasing plasma [K+] by intravenous potassium infusion reduces NCC phosphorylation and drives kaliuresis and natriuresis. Am J Physiol Renal Physiol 2014; 306:F1059-68. [PMID: 24598799 DOI: 10.1152/ajprenal.00015.2014] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Dietary potassium loading results in rapid kaliuresis, natriuresis, and diuresis associated with reduced phosphorylation (p) of the distal tubule Na(+)-Cl(-) cotransporter (NCC). Decreased NCC-p inhibits NCC-mediated Na(+) reabsorption and shifts Na(+) downstream for reabsorption by epithelial Na(+) channels (ENaC), which can drive K(+) secretion. Whether the signal is initiated by ingesting potassium or a rise in plasma K(+) concentration ([K(+)]) is not understood. We tested the hypothesis, in male rats, that an increase in plasma [K(+)] is sufficient to reduce NCC-p and drive kaliuresis. After an overnight fast, a single 3-h 2% potassium (2%K) containing meal increased plasma [K(+)] from 4.0 ± 0.1 to 5.2 ± 0.2 mM; increased urinary K(+), Na(+), and volume excretion; decreased NCC-p by 60%; and marginally reduced cortical Na(+)-K(+)-2Cl(-) cotransporter (NKCC) phosphorylation 25% (P = 0.055). When plasma [K(+)] was increased by tail vein infusion of KCl to 5.5 ± 0.1 mM over 3 h, significant kaliuresis and natriuresis ensued, NCC-p decreased by 60%, and STE20/SPS1-related proline alanine-rich kinase (SPAK) phosphorylation was marginally reduced 35% (P = 0.052). The following were unchanged at 3 h by either the potassium-rich meal or KCl infusion: Na(+)/H(+) exchanger 3 (NHE3), NHE3-p, NKCC, ENaC subunits, and renal outer medullary K(+) channel. In summary, raising plasma [K(+)] by intravenous infusion to a level equivalent to that observed after a single potassium-rich meal triggers renal kaliuretic and natriuretic responses, independent of K(+) ingestion, likely driven by decreased NCC-p and activity sufficient to shift sodium reabsorption downstream to where Na(+) reabsorption and flow drive K(+) secretion.
Collapse
Affiliation(s)
- Srinivas Rengarajan
- Cell and Neurobiology, Keck School of Medicine of USC, 1333 San Pablo St Los Angeles, CA 90033.
| | | | | | | | | | | |
Collapse
|
106
|
Dathe C, Daigeler AL, Seifert W, Jankowski V, Mrowka R, Kalis R, Wanker E, Mutig K, Bachmann S, Paliege A. Annexin A2 mediates apical trafficking of renal Na⁺-K⁺-2Cl⁻ cotransporter. J Biol Chem 2014; 289:9983-97. [PMID: 24526686 DOI: 10.1074/jbc.m113.540948] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The furosemide-sensitive Na(+)-K(+)-2Cl(-) cotransporter (NKCC2) is responsible for urine concentration and helps maintain systemic salt homeostasis. Its activity depends on trafficking to, and insertion into, the apical membrane, as well as on phosphorylation of conserved N-terminal serine and threonine residues. Vasopressin (AVP) signaling via PKA and other kinases activates NKCC2. Association of NKCC2 with lipid rafts facilitates its AVP-induced apical translocation and activation at the surface. Lipid raft microdomains typically serve as platforms for membrane proteins to facilitate their interactions with other proteins, but little is known about partners that interact with NKCC2. Yeast two-hybrid screening identified an interaction between NKCC2 and the cytosolic protein, annexin A2 (AnxA2). Annexins mediate lipid raft-dependent trafficking of transmembrane proteins, including the AVP-regulated water channel, aquaporin 2. Here, we demonstrate that AnxA2, which binds to phospholipids in a Ca(2+)-dependent manner and may organize microdomains, is codistributed with NKCC2 to promote its apical translocation in response to AVP stimulation and low chloride hypotonic stress. NKCC2 and AnxA2 interact in a phosphorylation-dependent manner. Phosphomimetic AnxA2 carrying a mutant phosphoacceptor (AnxA2-Y24D-GFP) enhanced surface expression and raft association of NKCC2 by 5-fold upon low chloride hypotonic stimulation, whereas AnxA2-Y24A-GFP and PKC-dependent AnxA2-S26D-GFP did not. As the AnxA2 effect involved only nonphosphorylated NKCC2, it appears to affect NKCC2 trafficking. Overexpression or knockdown experiments further supported the role of AnxA2 in the apical translocation and surface expression of NKCC2. In summary, this study identifies AnxA2 as a lipid raft-associated trafficking factor for NKCC2 and provides mechanistic insight into the regulation of this essential cotransporter.
Collapse
Affiliation(s)
- Christin Dathe
- From the Department of Anatomy, Charité-Universitätsmedizin Berlin, 10115 Berlin
| | | | | | | | | | | | | | | | | | | |
Collapse
|
107
|
Markadieu N, Delpire E. Physiology and pathophysiology of SLC12A1/2 transporters. Pflugers Arch 2014; 466:91-105. [PMID: 24097229 PMCID: PMC3877717 DOI: 10.1007/s00424-013-1370-5] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/21/2013] [Accepted: 09/23/2013] [Indexed: 01/14/2023]
Abstract
The electroneutral Na(+)-K(+)-Cl(-) cotransporters NKCC1 (encoded by the SLC12A2 gene) and NKCC2 (SLC12A1 gene) belong to the Na(+)-dependent subgroup of solute carrier 12 (SLC12) family of transporters. They mediate the electroneutral movement of Na(+) and K(+), tightly coupled to the movement of Cl(-) across cell membranes. As they use the energy of the ion gradients generated by the Na(+)/K(+)-ATPase to transport Na(+), K(+), and Cl(-) from the outside to the inside of a cell, they are considered secondary active transport mechanisms. NKCC-mediated transport occurs in a 1Na(+), 1K(+), and 2Cl(-) ratio, although NKCC1 has been shown to sometimes mediate partial reactions. Both transporters are blocked by bumetanide and furosemide, drugs which are commonly used in clinical medicine. NKCC2 is the molecular target of loop diuretics as it is expressed on the apical membrane of thick ascending limb of Henle epithelial cells, where it mediates NaCl reabsorption. NKCC1, in contrast, is found on the basolateral membrane of Cl(-) secretory epithelial cells, as well as in a variety of non-epithelial cells, where it mediates cell volume regulation and participates in Cl(-) homeostasis. Following their molecular identification two decades ago, much has been learned about their biophysical properties, their mode of operation, their regulation by kinases and phosphatases, and their physiological relevance. However, despite this tremendous amount of new information, there are still so many gaps in our knowledge. This review summarizes information that constitutes consensus in the field, but it also discusses current points of controversy and highlights many unanswered questions.
Collapse
Affiliation(s)
- Nicolas Markadieu
- Department of Anesthesiology, Vanderbilt University School of Medicine, MCN T-4202, 1161 21st Avenue South, Nashville, TN, 37232, USA
| | | |
Collapse
|
108
|
Common noncoding UMOD gene variants induce salt-sensitive hypertension and kidney damage by increasing uromodulin expression. Nat Med 2013. [PMID: 24185693 DOI: 10.1038/nm.3384.] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Hypertension and chronic kidney disease (CKD) are complex traits representing major global health problems. Multiple genome-wide association studies have identified common variants in the promoter of the UMOD gene, which encodes uromodulin, the major protein secreted in normal urine, that cause independent susceptibility to CKD and hypertension. Despite compelling genetic evidence for the association between UMOD risk variants and disease susceptibility in the general population, the underlying biological mechanism is not understood. Here, we demonstrate that UMOD risk variants increased UMOD expression in vitro and in vivo. Uromodulin overexpression in transgenic mice led to salt-sensitive hypertension and to the presence of age-dependent renal lesions similar to those observed in elderly individuals homozygous for UMOD promoter risk variants. The link between uromodulin and hypertension is due to activation of the renal sodium cotransporter NKCC2. We demonstrated the relevance of this mechanism in humans by showing that pharmacological inhibition of NKCC2 was more effective in lowering blood pressure in hypertensive patients who are homozygous for UMOD promoter risk variants than in other hypertensive patients. Our findings link genetic susceptibility to hypertension and CKD to the level of uromodulin expression and uromodulin's effect on salt reabsorption in the kidney. These findings point to uromodulin as a therapeutic target for lowering blood pressure and preserving renal function.
Collapse
|
109
|
Common noncoding UMOD gene variants induce salt-sensitive hypertension and kidney damage by increasing uromodulin expression. Nat Med 2013; 19:1655-60. [PMID: 24185693 PMCID: PMC3856354 DOI: 10.1038/nm.3384] [Citation(s) in RCA: 265] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 09/19/2013] [Indexed: 12/21/2022]
Abstract
Elevated blood pressure (BP) and chronic kidney disease (CKD) are complex traits representing major global health problems1,2. Multiple genome-wide association studies (GWAS) identified common variants giving independent susceptibility for CKD and hypertension in the promoter of the UMOD gene3-9, encoding uromodulin, the major protein secreted in the normal urine. Despite compelling genetic evidence, the underlying biological mechanism is not understood. Here, we demonstrate that UMOD risk variants directly increase UMOD expression in vitro and in vivo. We modeled this effect in transgenic mice and showed that uromodulin overexpression leads to salt-sensitive hypertension and to age-dependent renal lesions that are similarly observed in elderly subjects homozygous for UMOD risk variants. We demonstrate that the link between uromodulin and hypertension is caused by activation of the renal sodium co-transporter NKCC2. This very mechanism is relevant in humans, as pharmacological inhibition of NKCC2 is more effective in lowering BP in hypertensive patients homozygous for UMOD risk variants. Our findings establish a link between the genetic susceptibility to hypertension and CKD, the control of uromodulin expression and its role in a salt-reabsorbing tubular segment of the kidney. These data point to uromodulin as a novel therapeutic target to lower BP and preserve renal function.
Collapse
|
110
|
Ding B, Frisina RD, Zhu X, Sakai Y, Sokolowski B, Walton JP. Direct control of Na(+)-K(+)-2Cl(-)-cotransport protein (NKCC1) expression with aldosterone. Am J Physiol Cell Physiol 2013; 306:C66-75. [PMID: 24173102 DOI: 10.1152/ajpcell.00096.2013] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Sodium/potassium/chloride cotransporter (NKCC1) proteins play important roles in Na(+) and K(+) concentrations in key physiological systems, including cardiac, vascular, renal, nervous, and sensory systems. NKCC1 levels and functionality are altered in certain disease states, and tend to decline with age. A sensitive, effective way of regulating NKCC1 protein expression has significant biotherapeutic possibilities. The purpose of the present investigation was to determine if the naturally occurring hormone aldosterone (ALD) could regulate NKCC1 protein expression. Application of ALD to a human cell line (HT-29) revealed that ALD can regulate NKCC1 protein expression, quite sensitively and rapidly, independent of mRNA expression changes. Utilization of a specific inhibitor of mineralocorticoid receptors, eplerenone, implicated these receptors as part of the ALD mechanism of action. Further experiments with cycloheximide (protein synthesis inhibitor) and MG132 (proteasome inhibitor) revealed that ALD can upregulate NKCC1 by increasing protein stability, i.e., reducing ubiquitination of NKCC1. Having a procedure for controlling NKCC1 protein expression opens the doors for therapeutic interventions for diseases involving the mis-regulation or depletion of NKCC1 proteins, for example during aging.
Collapse
Affiliation(s)
- Bo Ding
- Department of Communication Sciences and Disorders, Global Center for Hearing and Speech Research, University of South Florida, Tampa, Florida
| | | | | | | | | | | |
Collapse
|
111
|
Park HJ, Curry JN, McCormick JA. Regulation of NKCC2 activity by inhibitory SPAK isoforms: KS-SPAK is a more potent inhibitor than SPAK2. Am J Physiol Renal Physiol 2013; 305:F1687-96. [PMID: 24133122 DOI: 10.1152/ajprenal.00211.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The cation cotransporters Na(+)-K(+)-2Cl(-) cotransporter 1 and 2 (NKCC1 and NKCC2) and Na(+)-Cl cotransporter (NCC) are phosphorylated and activated by the kinases Ste20-related proline alanine-rich kinase (SPAK) and oxidative stress-responsive kinase (OSR1), and their targeted disruption in mice causes phenotypes resembling the human disorders Bartter syndrome and Gitelman syndrome, reflecting reduced NKCC2 and NCC activity, respectively. We previously cloned a kinase-inactive kidney-specific SPAK isoform, kidney-specific (KS)-SPAK, which lacks the majority of the kinase domain present in full-length SPAK. Another putative inactive SPAK isoform, SPAK2, which only lacks the initial portion of the kinase domain, is also highly expressed in kidney. The functional relevance of inactive SPAK isoforms is unclear. Here, we tested whether KS-SPAK and SPAK2 differentially affect cation cotransporter activity. While KS-SPAK and SPAK2 both strongly inhibited NKCC1 activity, SPAK2 was a much weaker inhibitor of NKCC2 activity. Removal of the catalytic loop from SPAK2 resulted in an inhibitory effect on NKCC2 similar to that of KS-SPAK. Full-length SPAK is phosphorylated and activated by members of the with-no-lysine[K] (WNK) kinase family. Mutation of a WNK phosphorylation in KS-SPAK did not alter its ability to inhibit NKCC2 activity. In contrast, we found that residues involved in KS-SPAK interactions with cation cotransporters are required for it to inhibit cotransporter activity. Finally, both KS-SPAK and SPAK2 associated with NKCC2, as demonstrated by coimmunoprecipitation. Together, these data identify the structural basis for the differential effects of KS-SPAK and SPAK2 on cation cotransporter activity that may be physiologically important.
Collapse
Affiliation(s)
- Hae J Park
- Division of Nephrology and Hypertension, Dept. of Medicine, Oregon Health and Science Univ., 3181 SW Sam Jackson Park Road, L463, Portland, Oregon 97239-2940.
| | | | | |
Collapse
|
112
|
Denton JS, Pao AC, Maduke M. Novel diuretic targets. Am J Physiol Renal Physiol 2013; 305:F931-42. [PMID: 23863472 PMCID: PMC3798746 DOI: 10.1152/ajprenal.00230.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 07/12/2013] [Indexed: 01/11/2023] Open
Abstract
As the molecular revolution continues to inform a deeper understanding of disease mechanisms and pathways, there exist unprecedented opportunities for translating discoveries at the bench into novel therapies for improving human health. Despite the availability of several different classes of antihypertensive medications, only about half of the 67 million Americans with hypertension manage their blood pressure appropriately. A broader selection of structurally diverse antihypertensive drugs acting through different mechanisms would provide clinicians with greater flexibility in developing effective treatment regimens for an increasingly diverse and aging patient population. An emerging body of physiological, genetic, and pharmacological evidence has implicated several renal ion-transport proteins, or regulators thereof, as novel, yet clinically unexploited, diuretic targets. These include the renal outer medullary potassium channel, ROMK (Kir1.1), Kir4.1/5.1 potassium channels, ClC-Ka/b chloride channels, UTA/B urea transporters, the chloride/bicarbonate exchanger pendrin, and the STE20/SPS1-related proline/alanine-rich kinase (SPAK). The molecular pharmacology of these putative targets is poorly developed or lacking altogether; however, recent efforts by a few academic and pharmaceutical laboratories have begun to lessen this critical barrier. Here, we review the evidence in support of the aforementioned proteins as novel diuretic targets and highlight examples where progress toward developing small-molecule pharmacology has been made.
Collapse
Affiliation(s)
- Jerod S Denton
- T4208 Medical Center North, 1161 21st Ave. South, Nashville, TN 37232.
| | | | | |
Collapse
|
113
|
Melo Z, de los Heros P, Cruz-Rangel S, Vázquez N, Bobadilla NA, Pasantes-Morales H, Alessi DR, Mercado A, Gamba G. N-terminal serine dephosphorylation is required for KCC3 cotransporter full activation by cell swelling. J Biol Chem 2013; 288:31468-76. [PMID: 24043619 PMCID: PMC3814743 DOI: 10.1074/jbc.m113.475574] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The K+:Cl− cotransporter (KCC) activity is modulated by phosphorylation/dephosphorylation processes. In isotonic conditions, KCCs are inactive and phosphorylated, whereas hypotonicity promotes their dephosphorylation and activation. Two phosphorylation sites (Thr-991 and Thr-1048) in KCC3 have been found to be critical for its regulation. However, here we show that the double mutant KCC3-T991A/T1048A could be further activated by hypotonicity, suggesting that additional phosphorylation site(s) are involved. We observed that in vitro activated STE20/SPS1-related proline/alanine-rich kinase (SPAK) complexed to its regulatory MO25 subunit phosphorylated KCC3 at Ser-96 and that in Xenopus laevis oocytes Ser-96 of human KCC3 is phosphorylated in isotonic conditions and becomes dephosphorylated during incubation in hypotonicity, leading to a dramatic increase in KCC3 function. Additionally, WNK3, which inhibits the activity of KCC3, promoted phosphorylation of Ser-96 as well as Thr-991 and Thr-1048. These observations were corroborated in HEK293 cells stably transfected with WNK3. Mutation of Ser-96 alone (KCC3-S96A) had no effect on the activity of the cotransporter when compared with wild type KCC3. However, when compared with the double mutant KCC3-T991A/T1048A, the triple mutant KCC3-S96A/T991A/T1048A activity in isotonic conditions was significantly higher, and it was not further increased by hypotonicity or inhibited by WNK3. We conclude that serine residue 96 of human KCC3 is a third site that has to be dephosphorylated for full activation of the cotransporter during hypotonicity.
Collapse
Affiliation(s)
- Zesergio Melo
- From the Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Tlalpan, 14000 Mexico City, Mexico
| | | | | | | | | | | | | | | | | |
Collapse
|
114
|
Yang SS, Fang YW, Tseng MH, Chu PY, Yu IS, Wu HC, Lin SW, Chau T, Uchida S, Sasaki S, Lin YF, Sytwu HK, Lin SH. Phosphorylation regulates NCC stability and transporter activity in vivo. J Am Soc Nephrol 2013; 24:1587-97. [PMID: 23833262 DOI: 10.1681/asn.2012070742] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A T60M mutation in the thiazide-sensitive sodium chloride cotransporter (NCC) is common in patients with Gitelman's syndrome (GS). This mutation prevents Ste20-related proline and alanine-rich kinase (SPAK)/oxidative stress responsive kinase-1 (OSR1)-mediated phosphorylation of NCC and alters NCC transporter activity in vitro. Here, we examined the physiologic effects of NCC phosphorylation in vivo using a novel Ncc T58M (human T60M) knock-in mouse model. Ncc(T58M/T58M) mice exhibited typical features of GS with a blunted response to thiazide diuretics. Despite expressing normal levels of Ncc mRNA, these mice had lower levels of total Ncc and p-Ncc protein that did not change with a low-salt diet that increased p-Spak. In contrast to wild-type Ncc, which localized to the apical membrane of distal convoluted tubule cells, T58M Ncc localized primarily to the cytosolic region and caused an increase in late distal convoluted tubule volume. In MDCK cells, exogenous expression of phosphorylation-defective NCC mutants reduced total protein expression levels and membrane stability. Furthermore, our analysis found diminished total urine NCC excretion in a cohort of GS patients with homozygous NCC T60M mutations. When Wnk4(D561A/+) mice, a model of pseudohypoaldosteronism type II expressing an activated Spak/Osr1-Ncc, were crossed with Ncc(T58M/T58M) mice, total Ncc and p-Ncc protein levels decreased and the GS phenotype persisted over the hypertensive phenotype. Overall, these data suggest that SPAK-mediated phosphorylation of NCC at T60 regulates NCC stability and function, and defective phosphorylation at this residue corrects the phenotype of pseudohypoaldosteronism type II.
Collapse
Affiliation(s)
- Sung-Sen Yang
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, Taipei, Taiwan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
115
|
IRBIT plays an important role in NHE3-mediated pHi regulation in HSG cells. Biochem Biophys Res Commun 2013; 437:18-22. [DOI: 10.1016/j.bbrc.2013.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 06/04/2013] [Indexed: 11/20/2022]
|
116
|
Nguyen MTX, Lee DH, Delpire E, McDonough AA. Differential regulation of Na+ transporters along nephron during ANG II-dependent hypertension: distal stimulation counteracted by proximal inhibition. Am J Physiol Renal Physiol 2013; 305:F510-9. [PMID: 23720346 DOI: 10.1152/ajprenal.00183.2013] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
During angiotensin II (ANG II)-dependent hypertension, ANG II stimulates, while hypertension inhibits, Na(+) transporter activity to balance Na(+) output to input. This study tests the hypothesis that ANG II infusion activates Na(+) transporters in the distal nephron while inhibiting transporters along the proximal nephron. Male Sprague-Dawley rats were infused with ANG II (400 ng·kg(-1)·min(-1)) or vehicle for 2 wk. Kidneys were dissected (cortex vs. medulla) or fixed for immunohistochemistry (IHC). ANG II increased mean arterial pressure by 40 mmHg, urine Na(+) by 1.67-fold, and urine volume by 3-fold, evidence for hypertension and pressure natriuresis. Na(+) transporters' abundance and activation [assessed by phosphorylation (-P) or proteolytic cleavage] were measured by immunoblot. During ANG II infusion Na(+)/H(+) exchanger 3 (NHE3) abundance decreased in both cortex and medulla; Na-K-2Cl cotransporter 2 (NKCC2) decreased in medullary thick ascending loop of Henle (TALH) and increased, along with NKCC2-P, in cortical TALH; Na-Cl cotransporter (NCC) and NCC-P increased in the distal convoluted tubule; and epithelial Na(+) channel subunits and their cleaved forms were increased in both cortex and medulla. Like NKCC2, STE20/SPS1-related proline alanine-rich kinase (SPAK) and SPAK-P were decreased in medulla and increased in cortex. By IHC, during ANG II NHE3 remained localized to proximal tubule microvilli at lower abundance, and the differential regulation of NKCC2 and NKCC2-P in cortex versus medulla was evident. In summary, ANG II infusion increases Na(+) transporter abundance and activation from cortical TALH to medullary collecting duct while the hypertension drives a natriuresis response evident as decreased Na(+) transporter abundance and activation from proximal tubule through medullary TALH.
Collapse
Affiliation(s)
- Mien T X Nguyen
- Cell and Neurobiology, Keck School of Medicine of USC, 1333 San Pablo St., Los Angeles, CA 90033.
| | | | | | | |
Collapse
|
117
|
The CUL3-KLHL3 E3 ligase complex mutated in Gordon's hypertension syndrome interacts with and ubiquitylates WNK isoforms: disease-causing mutations in KLHL3 and WNK4 disrupt interaction. Biochem J 2013; 451:111-22. [PMID: 23387299 PMCID: PMC3632089 DOI: 10.1042/bj20121903] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The WNK (with no lysine kinase)–SPAK (SPS1-related proline/alanine-rich kinase)/OSR1
(oxidative stress-responsive kinase 1) signalling pathway plays an important role in controlling
mammalian blood pressure by modulating the activity of ion co-transporters in the kidney. Recent
studies have identified Gordon's hypertension syndrome patients with mutations in either CUL3
(Cullin-3) or the BTB protein KLHL3 (Kelch-like 3). CUL3 assembles with BTB proteins to form
Cullin–RING E3 ubiquitin ligase complexes. To explore how a CUL3–KLHL3 complex might
operate, we immunoprecipitated KLHL3 and found that it associated strongly with WNK isoforms and
CUL3, but not with other components of the pathway [SPAK/OSR1 or NCC
(Na+/Cl− co-transporter)/NKCC1
(Na+/K+/2Cl− co-transporter 1)]. Strikingly, 13 out of the
15 dominant KLHL3 disease mutations analysed inhibited binding to WNK1 or CUL3. The recombinant
wild-type CUL3–KLHL3 E3 ligase complex, but not a disease-causing CUL3–KLHL3[R528H]
mutant complex, ubiquitylated WNK1 in vitro. Moreover, siRNA (small
interfering RNA)-mediated knockdown of CUL3 increased WNK1 protein levels and kinase activity in
HeLa cells. We mapped the KLHL3 interaction site in WNK1 to a non-catalytic region (residues
479–667). Interestingly, the equivalent region in WNK4 encompasses residues that are mutated
in Gordon's syndrome patients. Strikingly, we found that the Gordon's disease-causing WNK4[E562K]
and WNK4[Q565E] mutations, as well as the equivalent mutation in the WNK1[479–667] fragment,
abolished the ability to interact with KLHL3. These results suggest that the CUL3–KLHL3 E3
ligase complex regulates blood pressure via its ability to interact with and ubiquitylate WNK
isoforms. The findings of the present study also emphasize that the missense mutations in WNK4 that
cause Gordon's syndrome strongly inhibit interaction with KLHL3. This could elevate blood pressure
by increasing the expression of WNK4 thereby stimulating inappropriate salt retention in the kidney
by promoting activation of the NCC/NKCC2 ion co-transporters. The present study reveals how
mutations that disrupt the ability of an E3 ligase to interact with and ubiquitylate a critical
cellular substrate such as WNK isoforms can trigger a chronic disease such as hypertension.
Collapse
|
118
|
Arroyo JP, Kahle KT, Gamba G. The SLC12 family of electroneutral cation-coupled chloride cotransporters. Mol Aspects Med 2013; 34:288-98. [PMID: 23506871 DOI: 10.1016/j.mam.2012.05.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 04/09/2012] [Indexed: 11/21/2022]
Abstract
The SLC12 family encodes electroneutral cation-coupled chloride cotransporters that are critical for several physiological processes including cell volume regulation, modulation of intraneuronal chloride concentration, transepithelial ion movement, and blood pressure regulation. Members of this family are the targets of the most commonly used diuretic drugs, have been shown to be the causative genes for inherited disease such as Gitelman, Bartter and Andermann syndromes, and potentially play a role in polygenic complex diseases like arterial hypertension, epilepsy, osteoporosis, and cancer.
Collapse
Affiliation(s)
- Juan Pablo Arroyo
- Molecular Physiology Unit, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico
| | | | | |
Collapse
|
119
|
Saritas T, Borschewski A, McCormick JA, Paliege A, Dathe C, Uchida S, Terker A, Himmerkus N, Bleich M, Demaretz S, Laghmani K, Delpire E, Ellison DH, Bachmann S, Mutig K. SPAK differentially mediates vasopressin effects on sodium cotransporters. J Am Soc Nephrol 2013; 24:407-18. [PMID: 23393317 DOI: 10.1681/asn.2012040404] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Activation of the Na(+)-K(+)-2Cl(-)-cotransporter (NKCC2) and the Na(+)-Cl(-)-cotransporter (NCC) by vasopressin includes their phosphorylation at defined, conserved N-terminal threonine and serine residues, but the kinase pathways that mediate this action of vasopressin are not well understood. Two homologous Ste20-like kinases, SPS-related proline/alanine-rich kinase (SPAK) and oxidative stress responsive kinase (OSR1), can phosphorylate the cotransporters directly. In this process, a full-length SPAK variant and OSR1 interact with a truncated SPAK variant, which has inhibitory effects. Here, we tested whether SPAK is an essential component of the vasopressin stimulatory pathway. We administered desmopressin, a V2 receptor-specific agonist, to wild-type mice, SPAK-deficient mice, and vasopressin-deficient rats. Desmopressin induced regulatory changes in SPAK variants, but not in OSR1 to the same degree, and activated NKCC2 and NCC. Furthermore, desmopressin modulated both the full-length and truncated SPAK variants to interact with and phosphorylate NKCC2, whereas only full-length SPAK promoted the activation of NCC. In summary, these results suggest that SPAK mediates the effect of vasopressin on sodium reabsorption along the distal nephron.
Collapse
Affiliation(s)
- Turgay Saritas
- Department of Anatomy, Charité Universitätsmedizin, Berlin, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
120
|
Ares GR, Haque MZ, Delpire E, Ortiz PA. Hyperphosphorylation of Na-K-2Cl Cotransporter in Thick Ascending Limbs of Dahl Salt-Sensitive Rats. Hypertension 2012; 60:1464-70. [DOI: 10.1161/hypertensionaha.112.202101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Salt-sensitive hypertension involves a renal defect preventing the kidney from eliminating excess NaCl. The thick ascending limb of Henle loop reabsorbs ≈30% of filtered NaCl via the apical Na-K-2Cl cotransporter (NKCC2). Higher NKCC2 activity and Cl reabsorption have been reported in the thick ascending limbs from Dahl salt-sensitive rats (DSS) fed normal salt. NKCC2 activity is primarily regulated by protein trafficking and phosphorylation at Thr
96
/Thr
101
via STE20- and SPS1-related proline and alanine-rich kinases and oxidative stress-responsive kinase 1. However, the mechanism for enhanced NKCC2 activity in DSS is unclear. We hypothesized that DSS exhibit enhanced NKCC2 trafficking and higher NKCC2 phosphorylation compared with Dahl salt-resistant rats on normal salt diet. We measured steady state surface NKCC2 expression and phosphorylation at Thr
96
and Thr
101
by surface biotinylation and Western blot. In DSS, the surface:total NKCC2 ratio was enhanced by 25% compared with Dahl salt-resistant rats (
P
<0.05) despite lower NKCC2 expression. Total NKCC2 phosphorylation at Thr
96
and Thr
101
was enhanced ≈5-fold in DSS thick ascending limbs. Moreover, total STE20- and SPS1-related proline and alanine-rich kinases expression, kidney-specific STE20- and SPS1-related proline and alanine-rich kinases, and oxidative stress-responsive kinase 1 were not different between strains, although STE20- and SPS1-related proline and alanine-rich kinases/oxidative stress-responsive kinase 1 phosphorylation was enhanced by 60% (
P
<0.05) in DSS rats, suggesting increased activity. We concluded that phosphorylation of NKCC2 Thr
96
and Thr
101
and surface:total NKCC2 ratio are enhanced in DSS rats. These differences in NKCC2 may be, in part, responsible for higher NKCC2 activity and abnormally enhanced thick ascending limb NaCl reabsorption in DSS rats.
Collapse
Affiliation(s)
- Gustavo R. Ares
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, MI (G.R.A., M.Z.H., P.A.O.); Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN (E.D.); Department of Physiology, Wayne State University, Detroit, MI (P.A.O.)
| | - Mohammed Z. Haque
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, MI (G.R.A., M.Z.H., P.A.O.); Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN (E.D.); Department of Physiology, Wayne State University, Detroit, MI (P.A.O.)
| | - Eric Delpire
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, MI (G.R.A., M.Z.H., P.A.O.); Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN (E.D.); Department of Physiology, Wayne State University, Detroit, MI (P.A.O.)
| | - Pablo A. Ortiz
- From the Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, MI (G.R.A., M.Z.H., P.A.O.); Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN (E.D.); Department of Physiology, Wayne State University, Detroit, MI (P.A.O.)
| |
Collapse
|
121
|
Lee DH, Maunsbach AB, Riquier-Brison AD, Nguyen MTX, Fenton RA, Bachmann S, Yu AS, McDonough AA. Effects of ACE inhibition and ANG II stimulation on renal Na-Cl cotransporter distribution, phosphorylation, and membrane complex properties. Am J Physiol Cell Physiol 2012; 304:C147-63. [PMID: 23114965 DOI: 10.1152/ajpcell.00287.2012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The renal distal tubule Na-Cl cotransporter (NCC) reabsorbs <10% of the filtered Na(+) but is a key control point for blood pressure regulation by angiotensin II (ANG II), angiotensin-converting enzyme inhibitors (ACEI), and thiazide diuretics. This study aimed to determine whether NCC phosphorylation (NCCp) was regulated by acute (20-30 min) treatment with the ACEI captopril (12 μg/min × 20 min) or by a sub-pressor dose of ANG II (20 ng·kg(-1)·min(-1)) in Inactin-anesthetized rats. By immuno-EM, NCCp was detected exclusively in or adjacent to apical plama membranes (APM) in controls and after ACEI or ANG II treatment, while NCC total was detected in both APM and subapical cytoplasmic vesicles (SCV) in all conditions. In renal homogenates, neither ACEI nor ANG II treatment altered NCCp abundance, assayed by immunoblot. However, by density gradient fractionation we identified a pool of low-density APM in which NCCp decreased 50% in response to captopril and was restored during ANG II infusion, and another pool of higher-density APM that responded reciprocally, indicative of regulated redistribution between two APM pools. In both pools, NCCp was preferentially localized to Triton-soluble membranes. Blue Native gel electrophoresis established that APM NCCp localized to ~700 kDa complexes (containing γ-adducin) while unphosphorylated NCC in intracellular membranes primarily localized to ~400 kDa complexes: there was no evidence for native monomeric or dimeric NCC or NCCp. In summary, this study demonstrates that phosphorylated NCC, localized to multimeric complexes in the APM, redistributes in a regulated manner within the APM in response to ACEI and ANG II.
Collapse
Affiliation(s)
- Donna H Lee
- Department of Cell and Neurobiology, Keck School of Medicine of University of Southern California, Los Angeles, CA 90033, USA
| | | | | | | | | | | | | | | |
Collapse
|
122
|
Hoorn EJ, Meima ME. Predicting kinase-substrate interactions in the era of proteomics: focus on "Identifying protein kinase target preferences using mass spectrometry". Am J Physiol Cell Physiol 2012; 303:C711-2. [PMID: 22814397 DOI: 10.1152/ajpcell.00232.2012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
123
|
Sengupta S, Tu SW, Wedin K, Earnest S, Stippec S, Luby-Phelps K, Cobb MH. Interactions with WNK (with no lysine) family members regulate oxidative stress response 1 and ion co-transporter activity. J Biol Chem 2012; 287:37868-79. [PMID: 22989884 DOI: 10.1074/jbc.m112.398750] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two of the four WNK (with no lysine (K)) protein kinases are associated with a heritable form of ion imbalance culminating in hypertension. WNK1 affects ion transport in part through activation of the closely related Ste20 family protein kinases oxidative stress-responsive 1 (OSR1) and STE20/SPS1-related proline-, alanine-rich kinase (SPAK). Once activated by WNK1, OSR1 and SPAK phosphorylate and stimulate the sodium, potassium, two chloride co-transporters, NKCC1 and NKCC2, and also affect other related ion co-transporters. We find that WNK1 and OSR1 co-localize on cytoplasmic puncta in HeLa and other cell types. We show that the C-terminal region of WNK1 including a coiled coil is sufficient to localize the fragment in a manner similar to the full-length protein, but some other fragments lacking this region are mislocalized. Photobleaching experiments indicate that both hypertonic and hypotonic conditions reduce the mobility of GFP-WNK1 in cells. The four WNK family members can phosphorylate the activation loop of OSR1 to increase its activity with similar kinetic constants. C-terminal fragments of WNK1 that contain three RFXV interaction motifs can bind OSR1, block activation of OSR1 by sorbitol, and prevent the OSR1-induced enhancement of ion co-transporter activity in cells, further supporting the conclusion that association with WNK1 is required for OSR1 activation and function at least in some contexts. C-terminal WNK1 fragments can be phosphorylated by OSR1, suggesting that OSR1 catalyzes feedback phosphorylation of WNK1.
Collapse
Affiliation(s)
- Samarpita Sengupta
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9041, USA
| | | | | | | | | | | | | |
Collapse
|
124
|
Grimm PR, Taneja TK, Liu J, Coleman R, Chen YY, Delpire E, Wade JB, Welling PA. SPAK isoforms and OSR1 regulate sodium-chloride co-transporters in a nephron-specific manner. J Biol Chem 2012; 287:37673-90. [PMID: 22977235 DOI: 10.1074/jbc.m112.402800] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
STE20/SPS-1-related proline-alanine-rich protein kinase (SPAK) and oxidative stress-related kinase (OSR1) activate the potassium-dependent sodium-chloride co-transporter, NKCC2, and thiazide-sensitive sodium-chloride cotransporter, NCC, in vitro, and both co-localize with a kinase regulatory molecule, Cab39/MO25α, at the apical membrane of the thick ascending limb (TAL) and distal convoluted tubule (DCT). Yet genetic ablation of SPAK in mice causes a selective loss of NCC function, whereas NKCC2 becomes hyperphosphorylated. Here, we explore the underlying mechanisms in wild-type and SPAK-null mice. Unlike in the DCT, OSR1 remains at the TAL apical membrane of KO mice where it is accompanied by an increase in the active, phosphorylated form of AMP-activated kinase. We found an alterative SPAK isoform (putative SPAK2 form), which modestly inhibits co-transporter activity in vitro, is more abundant in the medulla than the cortex. Thus, enhanced NKCC2 phosphorylation in the SPAK knock-out may be explained by removal of inhibitory SPAK2, sustained activity of OSR1, and activation of other kinases. By contrast, the OSR1/SPAK/M025α signaling apparatus is disrupted in the DCT. OSR1 becomes largely inactive and displaced from M025α and NCC at the apical membrane, and redistributes to dense punctate structures, containing WNK1, within the cytoplasm. These changes are paralleled by a decrease in NCC phosphorylation and a decrease in the mass of the distal convoluted tubule, exclusive to DCT1. As a result of the dependent nature of OSR1 on SPAK in the DCT, NCC is unable to be activated. Consequently, SPAK(-/-) mice are highly sensitive to dietary salt restriction, displaying prolonged negative sodium balance and hypotension.
Collapse
Affiliation(s)
- P Richard Grimm
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
| | | | | | | | | | | | | | | |
Collapse
|
125
|
Mechanisms of sodium–chloride cotransporter modulation by angiotensin II. Curr Opin Nephrol Hypertens 2012; 21:516-22. [DOI: 10.1097/mnh.0b013e32835571a4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
126
|
Rodan AR, Baum M, Huang CL. The Drosophila NKCC Ncc69 is required for normal renal tubule function. Am J Physiol Cell Physiol 2012; 303:C883-94. [PMID: 22914641 DOI: 10.1152/ajpcell.00201.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epithelial ion transport is essential to renal homeostatic function, and it is dysregulated in several diseases, such as hypertension. An understanding of the insect renal (Malpighian) tubule yields insights into conserved epithelial ion transport processes in higher organisms and also has implications for the control of insect infectious disease vectors. Here, we examine the role of the Na(+)-K(+)-2Cl(-) (NKCC) cotransporter Ncc69 in Drosophila tubule function. Ncc69 mutant tubules have decreased rates of fluid secretion and K(+) flux, and these phenotypes were rescued by expression of wild-type Ncc69 in the principal cells of the tubule. Na(+) flux was unaltered in Ncc69 mutants, suggesting Na(+) recycling across the basolateral membrane. In unstimulated tubules, the principal role of the Na(+)-K(+)-ATPase is to generate a favorable electrochemical gradient for Ncc69 activity: while the Na(+)-K(+)-ATPase inhibitor ouabain decreased K(+) flux in wild-type tubules, it had no effect in Ncc69 mutant tubules. However, in the presence of cAMP, which stimulates diuresis, additional Na(+)-K(+)-ATPase-dependent K(+) transport pathways are recruited. In studying the effects of capa-1 on wild-type and Ncc69 mutant tubules, we found a novel antidiuretic role for this hormone that is dependent on intact Ncc69, as it was abolished in Ncc69 mutant tubules. Thus, Ncc69 plays an important role in transepithelial ion and fluid transport in the fly renal tubule and is a target for regulation in antidiuretic states.
Collapse
Affiliation(s)
- Aylin R Rodan
- Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, Dallas, USA.
| | | | | |
Collapse
|
127
|
Current world literature. Curr Opin Nephrol Hypertens 2012; 21:557-66. [PMID: 22874470 DOI: 10.1097/mnh.0b013e3283574c3b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
128
|
Nguyen MTX, Yang LE, Fletcher NK, Lee DH, Kocinsky H, Bachmann S, Delpire E, McDonough AA. Effects of K+-deficient diets with and without NaCl supplementation on Na+, K+, and H2O transporters' abundance along the nephron. Am J Physiol Renal Physiol 2012; 303:F92-104. [PMID: 22496411 DOI: 10.1152/ajprenal.00032.2012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Dietary potassium (K(+)) restriction and hypokalemia have been reported to change the abundance of most renal Na(+) and K(+) transporters and aquaporin-2 isoform, but results have not been consistent. The aim of this study was to reexamine Na(+), K(+) and H(2)O transporters' pool size regulation in response to removing K(+) from a diet containing 0.74% NaCl, as well as from a diet containing 2% NaCl (as found in American diets) to blunt reducing total diet electrolytes. Sprague-Dawley rats (n = 5-6) were fed for 6 days with one of these diets: 2% KCl, 0.74% NaCl (2K1Na, control chow) compared with 0.03% KCl, 0.74% NaCl (0K1Na); or 2% KCl, 2%NaCl (2K2Na) compared with 0.03% KCl, 2% NaCl (0K2Na, Na(+) replete). In both 0K1Na and 0K2Na there were significant decreases in: 1) plasma [K(+)] (<2.5 mM); 2) urinary K(+) excretion (<5% of control); 3) urine osmolality and plasma [aldosterone], as well as 4) an increase in urine volume and medullary hypertrophy. The 0K2Na group had the lowest [aldosterone] (172.0 ± 17.4 pg/ml) and lower blood pressure (93.2 ± 4.9 vs. 112.0 ± 3.1 mmHg in 2K2Na). Transporter pool size regulation was determined by quantitative immunoblotting of renal cortex and medulla homogenates. The only differences measured in both 0K1Na and 0K2Na groups were a 20-30% decrease in cortical β-ENaC, 30-40% increases in kidney-specific Ste20/SPS1-related proline/alanine-rich kinase, and a 40% increase in medullary sodium pump abundance. The following proteins were not significantly changed in both the 0 K groups: Na(+)/H(+) exchanger isoform 3; Na(+)-K(+)-Cl(-) cotransporter; Na(+)-Cl(-) cotransporter, oxidative stress response kinase-1; renal outer medullary K(+) channel; autosomal recessive hypercholesterolemia; c-Src, aquaporin 2 isoform; or renin. Thus, despite profound hypokalemia and renal K(+) conservation, we did not confirm many of the changes that were previously reported. We predict that changes in transporter distribution and activity are likely more important for conserving K(+) than changes in total abundance.
Collapse
Affiliation(s)
- Mien T X Nguyen
- Department of Cell and Neurobiology, Keck School of Medicine of University of Southern California, Los Angeles, California, USA
| | | | | | | | | | | | | | | |
Collapse
|
129
|
Pacheco-Alvarez D, Vázquez N, Castañeda-Bueno M, de-Los-Heros P, Cortes-González C, Moreno E, Meade P, Bobadilla NA, Gamba G. WNK3-SPAK interaction is required for the modulation of NCC and other members of the SLC12 family. Cell Physiol Biochem 2012; 29:291-302. [PMID: 22415098 DOI: 10.1159/000337610] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2011] [Indexed: 11/19/2022] Open
Abstract
The serine/threonine with no lysine kinase 3 (WNK3) modulates the activity of the electroneutral cation-coupled chloride cotransporters (CCC) to promote Cl(-) influx and prevent Cl(-) efflux, thus fitting the profile for a putative "Cl(-)-sensing kinase". The Ste20-type kinases, SPAK/OSR1, become phosphorylated in response to reduction in intracellular chloride concentration and regulate the activity of NKCC1. Several studies have now shown that WNKs function upstream of SPAK/OSR1. This study was designed to analyze the role of WNK3-SPAK interaction in the regulation of CCCs with particular emphasis on NCC. In this study we used the functional expression system of Xenopus laevis oocytes to show that different SPAK binding sites in WNK3 ((241, 872, 1336)RFxV) are required for the kinase to have effects on CCCs. WNK3-F1337A no longer activated NKCC2, but the effects on NCC, NKCC1, and KCC4 were preserved. In contrast, the effects of WNK3 on these cotransporters were prevented in WNK3-F242A. The elimination of F873 had no consequence on WNK3 effects. WNK3 promoted NCC phosphorylation at threonine 58, even in the absence of the unique SPAK binding site of NCC, but this effect was abolished in the mutant WNK3-F242A. Thus, our data support the hypothesis that the effects of WNK3 upon NCC and other CCCs require the interaction and activation of the SPAK kinase. The effect is dependent on one of the three binding sites for SPAK that are present in WNK3, but not on the SPAK binding sites on the CCCs, which suggests that WNK3 is capable of binding both SPAK and CCCs to promote their phosphorylation.
Collapse
|
130
|
SPAK/OSR1 regulate NKCC1 and WNK activity: analysis of WNK isoform interactions and activation by T-loop trans-autophosphorylation. Biochem J 2012; 441:325-37. [PMID: 22032326 PMCID: PMC3242505 DOI: 10.1042/bj20111879] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Mutations in the WNK [with no lysine (K) kinase] family instigate hypertension and pain perception disorders. Of the four WNK isoforms, much of the focus has been on WNK1, which is activated in response to osmotic stress by phosphorylation of its T-loop residue (Ser382). WNK isoforms phosphorylate and activate the related SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1) protein kinases. In the present study, we first describe the generation of double-knockin ES (embryonic stem) cells, where SPAK and OSR1 cannot be activated by WNK1. We establish that NKCC1 (Na+/K+/2Cl- co-transporter 1), a proposed target of the WNK pathway, is not phosphorylated or activated in a knockin that is deficient in SPAK/OSR1 activity. We also observe that activity of WNK1 and WNK3 are markedly elevated in the knockin cells, demonstrating that SPAK/OSR1 significantly influences WNK activity. Phosphorylation of another regulatory serine residue, Ser1261, in WNK1 is unaffected in knockin cells, indicating that this is not phosphorylated by SPAK/OSR1. We show that WNK isoforms interact via a C-terminal CCD (coiled-coil domain) and identify point mutations of conserved residues within this domain that ablate the ability of WNK isoforms to interact. Employing these mutants, we demonstrate that interaction of WNK isoforms is not essential for their T-loop phosphorylation and activation, at least for overexpressed WNK isoforms. Moreover, we finally establish that full-length WNK1, WNK2 and WNK3, but not WNK4, are capable of directly phosphorylating Ser382 of WNK1 in vitro. This supports the notion that T-loop phosphorylation of WNK isoforms is controlled by trans-autophosphorylation. These results provide novel insights into the WNK signal transduction pathway and provide genetic evidence confirming the essential role that SPAK/OSR1 play in controlling NKCC1 function. They also reveal a role in which the downstream SPAK/OSR1 enzymes markedly influence the activity of the upstream WNK activators. The knockin ES cells lacking SPAK/OSR1 activity will be useful in validating new targets of the WNK signalling pathway.
Collapse
|
131
|
Carmosino M, Procino G, Svelto M. Na+-K+-2Cl- cotransporter type 2 trafficking and activity: the role of interacting proteins. Biol Cell 2012; 104:201-12. [PMID: 22211456 DOI: 10.1111/boc.201100049] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 12/28/2011] [Indexed: 11/30/2022]
Abstract
The central role of Na+-K+-2Cl- cotransporter type 2 (NKCC2) in vectorial transepithelial salt reabsorption in thick ascending limb cells from Henle's loop in the kidney is evidenced by the effects of loop diuretics, the pharmacological inhibitors of NKCC2, that are amongst the most powerful antihypertensive drugs available to date. Moreover, genetic mutations of the NKCC2 encoding gene resulting in impaired apical targeting and function of NKCC2 transporter give rise to a pathological phenotype known as type I Bartter syndrome, characterised by a severe volume depletion, hypokalaemia and metabolic alkalosis with high prenatal mortality. On the contrary, excessive NKCC2 activity has been linked with inherited hypertension in humans and in rodent models. Interestingly, in animal models of hypertension, NKCC2 upregulation is achieved by post-translational mechanisms underlining the need to analyse the molecular mechanisms involved in the regulation of NKCC2 trafficking and activity to gain insights in the pathogenesis of hypertension.
Collapse
Affiliation(s)
- Monica Carmosino
- Department of Biosciences, Biotechnologies and Pharmacological Sciences, University of Bari, Bari, Italy.
| | | | | |
Collapse
|
132
|
Pathar G, Föller M, Daryadel A, Mutig K, Bogatikov E, Fajol A, Almilaji A, Michael D, Stange G, Voelkl J, Wagner CA, Bachmann S, Lang F. OSR1-Sensitive Renal Tubular Phosphate Reabsorption. ACTA ACUST UNITED AC 2012; 36:149-61. [DOI: 10.1159/000343405] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2012] [Indexed: 02/06/2023]
|
133
|
Pathare G, Föller M, Michael D, Walker B, Hierlmeier M, Mannheim JG, Pichler BJ, Lang F. Enhanced FGF23 Serum Concentrations and Phosphaturia in Gene Targeted Mice Expressing WNK-Resistant Spak. ACTA ACUST UNITED AC 2012; 36:355-64. [DOI: 10.1159/000343393] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2012] [Indexed: 12/20/2022]
|
134
|
Abstract
PURPOSE OF REVIEW Sodium and chloride transport play a fundamental role in many physiological processes. In the kidney, sodium secretion and reabsorption are essential to maintain the extracellular volume and, thus, blood pressure (BP). In vascular smooth muscle, it is important for contractility and in the nervous system for the functioning of GABAergic neurons. Hence, the emergence of a WNK/SPAK/OSR1 kinase cascade that activates NaCl cotransporters has widespread physiological implications. This review gives an overview of the actions of SPAK and OSR1 kinases on NaCl cotransporters and highlights their possible therapeutic potential. RECENT FINDINGS Evidence has emerged from in-vitro phosphorylation assays that WNK kinases can activate SPAK and OSR1 kinases by phosphorylation of a key Thr residue in their catalytic domains. Once activated, SPAK and OSR1 in turn activate members of the SCL12A family of solute carriers by phosphorylation of conserved Ser/Thr residues in the N-terminal domain of these carrier proteins. The importance of this pathway has recently emerged from studies on mice that lack a catalytically active SPAK enzyme. These models are strikingly hypotensive with marked reduction in the phosphorylation of Na⁺/Cl⁻ cotransporter (NCC) in the kidney, and reduced Na⁺/K⁺/2Cl⁻ cotransporter (NKCC1) phosphorylation in the vessel wall. SUMMARY SPAK and OSR1 kinases regulate SCL12A transporters with important physiological effects for sodium homeostasis by the kidney, aortic contractility and neuronal excitability. In vivo, SPAK plays a major role in the regulation of blood pressure and represents a potential target for the development of novel diuretics.
Collapse
|
135
|
Oi K, Sohara E, Rai T, Misawa M, Chiga M, Alessi DR, Sasaki S, Uchida S. A minor role of WNK3 in regulating phosphorylation of renal NKCC2 and NCC co-transporters in vivo. Biol Open 2011; 1:120-7. [PMID: 23213404 PMCID: PMC3507202 DOI: 10.1242/bio.2011048] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mutations in WNK1 and WNK4 kinase genes have been shown to cause a human hereditary hypertensive disease, pseudohypoaldosteronism type II (PHAII). We previously discovered that WNK kinases phosphorylate and activate OSR1/SPAK kinases that regulate renal SLC12A family transporters such as NKCC2 and NCC, and clarified that the constitutive activation of this cascade causes PHAII. WNK3, another member of the WNK kinase family, was reported to be a strong activator of NCC/NKCC2 when assayed in Xenopus oocytes, suggesting that WNK3 also plays a major role in regulating blood pressure and sodium reabsorption in the kidney. However, it remains to be determined whether WNK3 is in fact involved in the regulation of these transporters in vivo. To clarify this issue, we generated and analyzed WNK3 knockout mice. Surprisingly, phosphorylation and expression of OSR1, SPAK, NKCC2 and NCC did not decrease in knockout mouse kidney under normal and low-salt diets. Similarly, expression of epithelial Na channel and Na/H exchanger 3 were not affected in knockout mice. Na+ and K+ excretion in urine in WNK3 knockout mice was not affected under different salt diets. Blood pressure in WNK3 knockout mice was not lower under normal diet. However, lower blood pressure was observed in WNK3 knockout mice fed low-salt diet. WNK4 and WNK1 expression was slightly elevated in the knockout mice under low-salt diet, suggesting compensation for WNK3 knockout by these WNKs. Thus, WNK3 may have some role in the WNK-OSR1/SPAK-NCC/NKCC2 signal cascade in the kidney, but its contribution to total WNK kinase activity may be minimal.
Collapse
Affiliation(s)
- Katsuyuki Oi
- Department of Nephrology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University , 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519 , Japan
| | | | | | | | | | | | | | | |
Collapse
|
136
|
Impaired phosphorylation of Na(+)-K(+)-2Cl(-) cotransporter by oxidative stress-responsive kinase-1 deficiency manifests hypotension and Bartter-like syndrome. Proc Natl Acad Sci U S A 2011; 108:17538-43. [PMID: 21972418 DOI: 10.1073/pnas.1107452108] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Na(+)-K(+)-2Cl(-) cotransporters (NKCCs), including NKCC1 and renal-specific NKCC2, and the Na(+)-Cl(-) cotransporter (NCC) play pivotal roles in the regulation of blood pressure (BP) and renal NaCl reabsorption. Oxidative stress-responsive kinase-1 (OSR1) is a known upstream regulator of N(K)CCs. We generated and analyzed global and kidney tubule-specific (KSP) OSR1 KO mice to elucidate the physiological role of OSR1 in vivo, particularly on BP and kidney function. Although global OSR1(-/-) mice were embryonically lethal, OSR1(+/-) mice had low BP associated with reduced phosphorylated (p) STE20 (sterile 20)/SPS1-related proline/alanine-rich kinase (SPAK) and p-NKCC1 abundance in aortic tissue and attenuated p-NKCC2 abundance with increased total and p-NCC expression in the kidney. KSP-OSR1(-/-) mice had normal BP and hypercalciuria and maintained significant hypokalemia on a low-K(+) diet. KSP-OSR1(-/-) mice exhibited impaired Na(+) reabsorption in the thick ascending loop on a low-Na(+) diet accompanied by remarkably decreased expression of p-NKCC2 and a blunted response to furosemide, an NKCC2 inhibitor. The expression of total SPAK and p-SPAK was significantly increased in parallel to that of total NCC and p-NCC despite unchanged total NKCC2 expression. These results suggest that, globally, OSR1 is involved in the regulation of BP and renal tubular Na(+) reabsorption mainly via the activation of NKCC1 and NKCC2. In the kidneys, NKCC2 but not NCC is the main target of OSR1 and the reduced p-NKCC2 in KSP-OSR1(-/-) mice may lead to a Bartter-like syndrome.
Collapse
|
137
|
Ares GR, Caceres PS, Ortiz PA. Molecular regulation of NKCC2 in the thick ascending limb. Am J Physiol Renal Physiol 2011; 301:F1143-59. [PMID: 21900458 DOI: 10.1152/ajprenal.00396.2011] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The kidney plays an essential role in blood pressure regulation by controlling short-term and long-term NaCl and water balance. The thick ascending limb of the loop of Henle (TAL) reabsorbs 25-30% of the NaCl filtered by the glomeruli in a process mediated by the apical Na(+)-K(+)-2Cl(-) cotransporter NKCC2, which allows Na(+) and Cl(-) entry from the tubule lumen into TAL cells. In humans, mutations in the gene coding for NKCC2 result in decreased or absent activity characterized by severe salt and volume loss and decreased blood pressure (Bartter syndrome type 1). Opposite to Bartter's syndrome, enhanced NaCl absorption by the TAL is associated with human hypertension and animal models of salt-sensitive hypertension. TAL NaCl reabsorption is subject to exquisite control by hormones like vasopressin, parathyroid, glucagon, and adrenergic agonists (epinephrine and norepinephrine) that stimulate NaCl reabsorption. Atrial natriuretic peptides or autacoids like nitric oxide and prostaglandins inhibit NaCl reabsorption, promoting salt excretion. In general, the mechanism by which hormones control NaCl reabsorption is mediated directly or indirectly by altering the activity of NKCC2 in the TAL. Despite the importance of NKCC2 in renal physiology, the molecular mechanisms by which hormones, autacoids, physical factors, and intracellular ions regulate NKCC2 activity are largely unknown. During the last 5 years, it has become apparent that at least three molecular mechanisms determine NKCC2 activity. As such, membrane trafficking, phosphorylation, and protein-protein interactions have recently been described in TALs and heterologous expression systems as mechanisms that modulate NKCC2 activity. The focus of this review is to summarize recent data regarding NKCC2 regulation and discuss their potential implications in physiological control of TAL function, renal physiology, and blood pressure regulation.
Collapse
Affiliation(s)
- Gustavo R Ares
- Hypertension and Vascular Research Division, Dept. of Internal Medicine, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA
| | | | | |
Collapse
|
138
|
A SPAK isoform switch modulates renal salt transport and blood pressure. Cell Metab 2011; 14:352-64. [PMID: 21907141 PMCID: PMC3172576 DOI: 10.1016/j.cmet.2011.07.009] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 06/09/2011] [Accepted: 07/29/2011] [Indexed: 11/21/2022]
Abstract
The renal thick ascending limb (TAL) and distal convoluted tubule (DCT) play central roles in salt homeostasis and blood pressure regulation. An emerging model suggests that bumetanide- and thiazide-sensitive NaCl transporters (NKCC2 and NCC) along these segments are phosphorylated and activated by WNK kinases, via SPAK and OSR1. Here, we show that a kidney-specific SPAK isoform, which lacks the kinase domain, inhibits phosphorylation of NCC and NKCC2 by full-length SPAK in vitro. Kidney-specific SPAK is highly expressed along the TAL, whereas full-length SPAK is more highly expressed along the DCT. As predicted from the differential expression, SPAK knockout in animals has divergent effects along TAL and DCT, with increased phosphorylated NKCC2 along TAL and decreased phosphorylated NCC along DCT. In mice, extracellular fluid volume depletion shifts SPAK isoform abundance to favor NaCl retention along both segments, indicating that a SPAK isoform switch modulates sodium avidity along the distal nephron.
Collapse
|
139
|
MO25 is a master regulator of SPAK/OSR1 and MST3/MST4/YSK1 protein kinases. EMBO J 2011; 30:1730-41. [PMID: 21423148 DOI: 10.1038/emboj.2011.78] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 02/23/2011] [Indexed: 11/08/2022] Open
Abstract
Mouse protein-25 (MO25) isoforms bind to the STRAD pseudokinase and stabilise it in a conformation that can activate the LKB1 tumour suppressor kinase. We demonstrate that by binding to several STE20 family kinases, MO25 has roles beyond controlling LKB1. These new MO25 targets are SPAK/OSR1 kinases, regulators of ion homeostasis and blood pressure, and MST3/MST4/YSK1, involved in controlling development and morphogenesis. Our analyses suggest that MO25α and MO25β associate with these STE20 kinases in a similar manner to STRAD. MO25 isoforms induce approximately 100-fold activation of SPAK/OSR1 dramatically enhancing their ability to phosphorylate the ion cotransporters NKCC1, NKCC2 and NCC, leading to the identification of several new phosphorylation sites. siRNA-mediated reduction of expression of MO25 isoforms in mammalian cells inhibited phosphorylation of endogenous NKCC1 at residues phosphorylated by SPAK/OSR1, which is rescued by re-expression of MO25α. MO25α/β binding to MST3/MST4/YSK1 also stimulated kinase activity three- to four-fold. MO25 has evolved as a key regulator of a group of STE20 kinases and may represent an ancestral mechanism of regulating conformation of pseudokinases and activating catalytically competent protein kinases.
Collapse
|
140
|
Pacheco-Alvarez D, Gamba G. WNK3 is a Putative Chloride-sensing Kinase. Cell Physiol Biochem 2011; 28:1123-34. [DOI: 10.1159/000335848] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2011] [Indexed: 11/19/2022] Open
|