Control of sodium and potassium homeostasis by renal distal convoluted tubules

Distal convoluted tubules (DCT), which contain the Na-Cl cotransporter (NCC) inhibited by thiazide diuretics, undergo complex modulation to preserve Na+ and K+ homeostasis. The lysine kinases 1 and 4 (WNK1 and WNK4), identified as hyperactive in the hereditary disease pseudohypoaldosteronism type 2, are responsible for activation of NCC and consequent hypokalemia and hypertension. WNK4, highly expressed in DCT, activates the SPAK/OSR1 kinases, which phosphorylate NCC and other regulatory proteins and transporters in the distal nephron. WNK4 works as a chloride sensor through a Cl- binding site, which acts as an on/off switch at this kinase in response to changes of basolateral membrane electrical potential, the driving force of cellular Cl- efflux. High intracellular Cl- in hyperkalemia decreases NCC phosphorylation and low intracellular Cl- in hypokalemia increases NCC phosphorylation and activity, which makes plasma K+ concentration a central modulator of NCC and of K+ secretion. The WNK4 phosphorylation by cSrc or SGK1, activated by angiotensin II or aldosterone, respectively, is another relevant mechanism of NCC, ENaC, and ROMK modulation in states such as volume reduction, hyperkalemia, and hypokalemia. Loss of NCC function induces upregulation of electroneutral NaCl reabsorption by type B intercalated cells through the combined activity of pendrin and NDCBE, as demonstrated in double knockout mice (KO) animal models, Ncc/pendrin or Ncc/NDCBE. The analysis of ks-Nedd-4-2 KO animal models introduced the modulation of NEDD4-2 by intracellular Mg2+ activity as an important regulator of NCC, explaining the thiazide-induced persistent hypokalemia.

Clinical efficacy of controlled-release morphine tablets combined with celecoxib in pain management and the effects on WNK1 expression

OBJECTIVES: This study was designed to evaluate the clinical efficacy of controlled-release morphine tablets combined with celecoxib in relieving osteocarcinoma-related pain and the effects of the combination on WNK1 expression. METHODS: A total of 110 patients with osteocarcinoma-related pain were selected and divided into two groups based on the treatment administered, including the control group (treated with controlled-release morphine tablets alone) and the study group (treated with a combination of controlled-release morphine tablets and celecoxib). We compared the treatment efficacy, pain level (visual analog scale (VAS)), time of onset of breakthrough pain (BTP), dose of morphine, incidence of adverse events, quality of life (QOL) score, and With-no-lysine 1 (WNK1) expression in the peripheral blood (PB) as determined with qRT-PCR before and after treatment, of the two groups. RESULTS: The total effective rate of the study group was higher than that of the control group, while the VAS score, time of onset of BTP, dose of morphine, incidence of adverse events, QOL score, and relative WNK1 expression in the PB were lower than those of the control group (p<0.05). CONCLUSION: Combination treatment with controlled-release morphine tablets and celecoxib can be extensively used in the clinical setting because it effectively improves the symptoms, QOL score, and adverse effects in patients with osteocarcinoma-related pain.

Functional identification of protein phosphatase 1-binding consensus residues in NBCe1-B

Protein phosphatase 1 (PP1) is involved in various signal transduction mechanisms as an extensive regulator. The PP1 catalytic subunit (PP1c) recognizes and binds to PP1-binding consensus residues (FxxR/KxR/K) in NBCe1-B. Consequently, we focused on identifying the function of the PP1-binding consensus residue, ⁹²²FMDRLK⁹²⁷ , in NBCe1-B. Using site-directed mutagenesis and co-immunoprecipitation assays, we revealed that in cases where the residues were substituted (F922A, R925A, and K927A) or deleted (deletion of amino acids 922–927), NBCe1-B mutants inhibited PP1 binding to NBCe1-B. Additionally, by recording the intracellular pH, we found that PP1-binding consensus residues in NBCe1-B were not only critical for NBCe1-B activity, but also relevant to its surface expression level. Therefore, we reported that NBCe1-B, as a substrate of PP1, contains these residues in the C-terminal region and that the direct interaction between NBCe1-B and PP1 is functionally critical in controlling the regulation of the HCO₃⁻ transport. These results suggested that like IRBIT, PP1 was another novel regulator of HCO₃⁻ secretion in several types of epithelia.

Change in expression of WNK1 in spinal cord of a rat model with bone cancer pain / 中国药理学通报

Aim To investigate the changes in the ex-pression of WNK1 in spinal cord of a rat model with bone cancer pain. Methods Female SD rats, weig-hing 170 ~200 g, were randomly divided into three groups:normal control group (group C, n=3), sham operation group ( group S, n =3 ) and bone cancer pain group ( group BCP, n =24 ) . Group C was not given any treatment, and group S was injected into the bone marrow of left tibia with 5 μl PBS solution while group BCP with 5 μl WALKER 256 mammary gland cancer cell suspension (approximately 1 × 105 cells). Mechanical paw withdrawal threshold ( MWT ) was measured at d1 before inoculation ( baseline) and d3, 6,9,10,11,12 after inoculation. Group S and C were sacrificed at d 12 while group BCP at d 3 ,6 ,9 ,12 after inoculation and spinal cord ( L4~6 ) were removed at different time points for detection of WNK1 mRNA ex-pression by qRT-PCR and WNK1 protein expression by Western blot. Results Compared with group C and S,group BCP’ s MWT started to decrease since d 3 ( P0. 05 ) while the protein expression upregulated since d6 and also showed an in-creasing trend to d 12 ( P<0. 01 ) . Conclusion The expression of WNK1 in spinal cord of a rat model with bone cancer pain increased abnormally, which may be involved in the occurrence and maintenance of a rat model with bone cancer pain.

Ca2+ is a Regulator of the WNK/OSR1/NKCC Pathway in a Human Salivary Gland Cell Line

Wnk kinase maintains cell volume, regulating various transporters such as sodium-chloride cotransporter, potassium-chloride cotransporter, and sodium-potassium-chloride cotransporter 1 (NKCC1) through the phosphorylation of oxidative stress responsive kinase 1 (OSR1) and STE20/SPS1-related proline/alanine-rich kinase (SPAK). However, the activating mechanism of Wnk kinase in specific tissues and specific conditions is broadly unclear. In the present study, we used a human salivary gland (HSG) cell line as a model and showed that Ca2+ may have a role in regulating Wnk kinase in the HSG cell line. Through this study, we found that the HSG cell line expressed molecules participating in the WNK-OSR1-NKCC pathway, such as Wnk1, Wnk4, OSR1, SPAK, and NKCC1. The HSG cell line showed an intracellular Ca2+ concentration ([Ca2+]i) increase in response to hypotonic stimulation, and the response was synchronized with the phosphorylation of OSR1. Interestingly, when we inhibited the hypotonically induced [Ca2+]i increase with nonspecific Ca2+ channel blockers such as 2-aminoethoxydiphenyl borate, gadolinium, and lanthanum, the phosphorylated OSR1 level was also diminished. Moreover, a cyclopiazonic acid-induced passive [Ca2+]i elevation was evoked by the phosphorylation of OSR1, and the amount of phosphorylated OSR1 decreased when the cells were treated with BAPTA, a Ca2+ chelator. Finally, through that process, NKCC1 activity also decreased to maintain the cell volume in the HSG cell line. These results indicate that Ca2+ may regulate the WNK-OSR1 pathway and NKCC1 activity in the HSG cell line. This is the first demonstration that indicates upstream Ca2+ regulation of the WNK-OSR1 pathway in intact cells.

WNK4 kinase-mediated inhibitory effect on expression of BK channel via lysosomal pathway / 中华肾脏病杂志

Objective To investigate the mechanism underlying the WNK4 kinasemediated inhibitory effect on BK channel. Methods Cos-7 cells were cotransfected with BK in combination with either CD4 (control group) or wild type WNK4 (WNK4-WT).Immunostaining and confocal microscopy,chemiluminescence,Western blotting analysis were then employed to determine the BK localization in cells,BK surface expression and total protein level,respectively.To further investigate whether the reduction of BK protein expression is due to an increase in degradation through a lysosomal pathway,BK protein level was determined after treated with bafilomycin A1(Baf A1),a proton pump inhibitor affecting lysosomal degradation. Results Immunostaining and confocal microscopic study showed that BK was localized both in plasma membrane and cytosol in the control group.After cells transfected with WNK4-WT,BK expression was markedly reduced.Chemiluminescent assay found that BK surface expression level was 299.9±18.6 in the control group,whereas it was significantly reduced (148.4±13.7,P＜0.01) in the WNK4-WT group.Western blotting analysis showed that total BK protein level was markedly reduced in the presence of WNK4-WT compared to the control group.WNK4-WT was shown to significantly reduce the BK total protein level (42.3％±15.2％) compared to the control group (100％) (P＜0.01).When the cells was treated with Bafilomycin A1 (Baf A1,0.5 μmol/L),WNK4-mediated reduction in BK protein was reversed (82.2％±12.1％,P＜0.05). Conclusions WNK4 inhibits total and surface protein expression of BK in Cos-7 cells whick is likely due to an increase in BK degradation through a lysosomal pathway.

Study on the association between genetic polymorphism on WNK4 genes and essential hypertension among Kazakhs ethnic population,in Xinjiang / 中华流行病学杂志

Objective To investigate whether G1155942T polymorphism in WNK4 gene is associated with essential hypertension in a population with Kazakhs ethnicity,in Xinjiang.Methods This study covered 563 hypertension patients and 346 normotensive controls.The variant of G1155942T was determined by the TaqMan probe real-time PCR method.Some biochemical indices such as glucose (GLU),triglyeeride (TG) and total cholesterol (TC) were also measured.All of these results were under logistic regression analysis.Addictive model was applied to assess the interactive effects between WNK4 gene G1155942T mutation and environmental factors on hypertension. Results The G1155942T polymorphism was consistent with Hardy-Weinberg expectations in both case and control groups.Genotype and allele frequencies of G1155942T were observed (P=0.004,P=0.003).Data through logistic regression analysis showed that factors as age,BMI,total cholesterol as well as the GT + TT genotype frequencies of Exon 8 G1155942T polymorphism in WNK4 were responsible for the increased risks for hypertension.Positive interactions between G1155942T mutation and gender,BMI,GLU,the OR were 3.75 (95% CI:1.19-11.80),5.77 (95% CI:1.93-17.21 ) and 8.67 (95% CI:1.03-72.99),respectively.Conclusion Our result suggested that the Exon 8 G1155942T polymorphism in WNK4 gene was associated with hypertension in the studied Kazakhs ethnic group in Xinjiang and the T allele might be the risk factor for essential hypertension.There were interactive effects between WNK4 gene G1155942T mutation,gender,BMI,and GLU.

Mutations of WNK gene in patients with hypokalemic salt-losing tubulopathies / 上海交通大学学报（医学版）

Objective To explore the molecular mechanisms involved in hypokalemic salt-losing tubulopathies ( SLTs) through genetic screening of WNK gene in patients with SLTs. Methods Forty-four kindreds of SLTs were diagnosed Batter's syndrome or Gitelman's syndrome after CLCNKB and SLC12A3 sequencing and analysis, 8 of whose phenotype can not be simply attributed to CLCNKB or SLC12A3 mutations. Primers for PCR-amplified exons of WNK4 and WNK1 gene in genomic DNA were designed, and direct sequencing was performed to analyse the PCR products. Results Two missense mutations of WNK1, Ile~(1172)→ Met (I1172M) and Ser~(2047) → Asn (S2047N), were identified. Both of these 2 mutations segregated with the disease in SLTs kindred. Conclusion Two heterozygote missense mutations of WNK1 gene (I1172 M and S2047N) were found in 8 SLTs kindreds, indicating that WNK1 might be another gene responsible for hypokalemic salt-losing tubulopathies.

WNKs: protein kinases with a unique kinase domain

WNKs (with-no-lysine [K]) are a family of serine-threonine protein kinases with an atypical placement of the catalytic lysine relative to all other protein kinases. The roles of WNK kinases in regulating ion transport were first revealed by the findings that mutations of two members cause a genetic hypertension and hyperkalemia syndrome. More recent studies suggest that WNKs are pleiotropic protein kinases with important roles in many cell processes in addition to ion transport. Here, we review roles of WNK kinases in the regulation of ion balance, cell signaling, survival, and proliferation, and embryonic organ development.

Expression of WNK genes in the mouse kidney / 中华肾脏病杂志

Objective To investigate the expression of WNK1 and WNK4 genes in the mouse kidney. Methods The probes corresponding to the genes were amplified by RT PCR from mouse kidney, and then Northern blotting was performed on mouse multiple tissues membrane. The fragments were cloned into pGEM T vector,the correct plasmids were linearized and transcripted into RNA probes in vitro. In situ hybridization was performed on the mouse kidney sections. Results WNK1 gene was widely expressed in mouse tissues. There was a 9 5 kb strong signal in kidney. WNK4 gene was mainly expressed in kidney and had a 4 4 kb signal. In situ hybridization showed WNK1 gene was mostly expressed in the distal convoluted tubule whereas WNK4 gene was expressed in the medullary collecting ducts besides the distal convoluted tubules. Conclusion Both WNK1 and WNK4 genes were expressed in kidney. WNK4 was expressed more widely than WNK1 in mouse kidney.

Investigation of the role of WNK4 gene Ala589Ser polymorphism in essential hypertension / 解放军医学杂志

Objective To investigate the role of WNK4 gene Exon8 Ala589Ser polymorphism in the pathogenesis of essential hypertension. Methods This study included 259 hypertensive patients and 235 normotensive patients as control subjects. Exon8 Ala589Ser polymorphism in WNK4 was investigated by PCR-RFLP and confirmed by direct sequencing. Genotype, genotype frequencies and allele frequencies of the polymorphism were compared among patients with essential hypertension and control subjects. At the same time, some clinical biochemical variables, such as the blood sugar and lipids in both groups. All of these results were analyzed with Logistic regression analysis to determine whether the risk of hypertension is associated with the polymorphism and the determined biochemical variables. Results The allele frequency of Exon8 Ala589Ser polymorphism in WNK4 in hypertensive patients was significantly higher (P