scholarly journals MST3 Involvement in Na+ and K+ Homeostasis with Increasing Dietary Potassium Intake

2021 ◽  
Vol 22 (3) ◽  
pp. 999
Author(s):  
Chee-Hong Chan ◽  
Sheng-Nan Wu ◽  
Bo-Ying Bao ◽  
Houng-Wei Li ◽  
Te-Ling Lu
Keyword(s):  
Na Channel ◽  
Elevated Plasma ◽  
Wild Type ◽  
Potassium Intake ◽  
Dietary Potassium ◽  
K Secretion ◽  
Distal Tubules ◽  
Convoluted Tubules ◽  
Epithelial Na Channel ◽  
Lower Urinary

K+ loading inhibits NKCC2 (Na-K-Cl cotransporter) and NCC (Na-Cl cotransporter) in the early distal tubules, resulting in Na+ delivery to the late distal convoluted tubules (DCTs). In the DCTs, Na+ entry through ENaC (epithelial Na channel) drives K+ secretion through ROMK (renal outer medullary potassium channel). WNK4 (with-no-lysine 4) regulates the NCC/NKCC2 through SAPK (Ste20-related proline-alanine-rich kinase)/OSR1 (oxidative stress responsive). K+ loading increases intracellular Cl−, which binds to the WNK4, thereby inhibiting autophosphorylation and downstream signals. Acute K+ loading-deactivated NCC was not observed in Cl−-insensitive WNK4 mice, indicating that WNK4 was involved in K+ loading-inhibited NCC activity. However, chronic K+ loading deactivated NCC in Cl−-insensitive WNK4 mice, indicating that other mechanisms may be involved. We previously reported that mammalian Ste20-like protein kinase 3 (MST3/STK24) was expressed mainly in the medullary TAL (thick ascending tubule) and at lower levels in the DCTs. MST3−/− mice exhibited higher ENaC activity, causing hypernatremia and hypertension. To investigate MST3 function in maintaining Na+/K+ homeostasis in kidneys, mice were fed diets containing various concentrations of Na+ and K+. The 2% KCl diets induced less MST3 expression in MST3−/− mice than that in wild-type (WT) mice. The MST3−/− mice had higher WNK4, NKCC2-S130 phosphorylation, and ENaC expression, resulting in lower urinary Na+ and K+ excretion than those of WT mice. Lower urinary Na+ excretion was associated with elevated plasma [Na+] and hypertension. These results suggest that MST3 maintains Na+/K+ homeostasis in response to K+ loading by regulation of WNK4 expression and NKCC2 and ENaC activity.

scholarly journals Deletion of Kir5.1 Impairs Renal Ability to Excrete Potassium during Increased Dietary Potassium Intake

2019 ◽  
Vol 30 (8) ◽  
pp. 1425-1438 ◽  
Author(s):  
Peng Wu ◽  
Zhong-Xiuzi Gao ◽  
Dan-Dan Zhang ◽  
Xiao-Tong Su ◽  
Wen-Hui Wang ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Potassium Channel ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Plasma Potassium ◽  
Wild Type ◽  
High Potassium ◽  
Potassium Intake ◽  
Dietary Potassium ◽  
Low Potassium

BackgroundThe basolateral potassium channel in the distal convoluted tubule (DCT), comprising the inwardly rectifying potassium channel Kir4.1/Kir5.1 heterotetramer, plays a key role in mediating the effect of dietary potassium intake on the thiazide-sensitive NaCl cotransporter (NCC). The role of Kir5.1 (encoded by Kcnj16) in mediating effects of dietary potassium intake on the NCC and renal potassium excretion is unknown.MethodsWe used electrophysiology, renal clearance, and immunoblotting to study Kir4.1 in the DCT and NCC in Kir5.1 knockout (Kcnj16−/−) and wild-type (Kcnj16+/+) mice fed with normal, high, or low potassium diets.ResultsWe detected a 40-pS and 20-pS potassium channel in the basolateral membrane of the DCT in wild-type and knockout mice, respectively. Compared with wild-type, Kcnj16−/− mice fed a normal potassium diet had higher basolateral potassium conductance, a more negative DCT membrane potential, higher expression of phosphorylated NCC (pNCC) and total NCC (tNCC), and augmented thiazide-induced natriuresis. Neither high- nor low-potassium diets affected the basolateral DCT’s potassium conductance and membrane potential in Kcnj16−/− mice. Although high potassium reduced and low potassium increased the expression of pNCC and tNCC in wild-type mice, these effects were absent in Kcnj16−/− mice. High potassium intake inhibited and low intake augmented thiazide-induced natriuresis in wild-type but not in Kcnj16−/− mice. Compared with wild-type, Kcnj16−/− mice with normal potassium intake had slightly lower plasma potassium but were more hyperkalemic with prolonged high potassium intake and more hypokalemic during potassium restriction.ConclusionsKir5.1 is essential for dietary potassium’s effect on NCC and for maintaining potassium homeostasis.

scholarly journals Furosemide reduces BK-αβ4-mediated K+ secretion in mice on an alkaline high-K+ diet

2019 ◽  
Vol 316 (2) ◽  
pp. F341-F350 ◽  
Author(s):  
Bangchen Wang ◽  
Jun Wang-France ◽  
Huaqing Li ◽  
Steven C. Sansom
Keyword(s):  
Plasma Aldosterone ◽  
Elevated Plasma ◽  
Wild Type ◽  
Distal Nephron ◽  
Urine Ph ◽  
Alkaline Urine ◽  
High K ◽  
K Secretion ◽  
Cardioprotective Effects ◽  
Apical Localization

Special high-K diets have cardioprotective effects and are often warranted in conjunction with diuretics such as furosemide for treating hypertension. However, it is not understood how a high-K diet (HK) influences the actions of diuretics on renal K+ handling. Furosemide acidifies the urine by increasing acid secretion via the Na+-H+ exchanger 3 (NHE3) in TAL and vacuolar H+-ATPase (V-ATPase) in the distal nephron. We previously found that an alkaline urine is required for large conductance Ca2+-activated K+ (BK)-αβ4-mediated K+ secretion in mice on HK. We therefore hypothesized that furosemide could reduce BK-αβ4-mediated K+ secretion by acidifying the urine. Treating with furosemide (drinking water) for 11 days led to decreased urine pH in both wild-type (WT) and BK-β4-knockout mice (BK-β4-KO) with increased V-ATPase expression and elevated plasma aldosterone levels. However, furosemide decreased renal K+ clearance and elevated plasma [K+] in WT but not BK-β4-KO. Western blotting and immunofluorescence staining showed that furosemide treatment decreased cortical expression of BK-β4 and reduced apical localization of BK-α in connecting tubules. Addition of the carbonic anhydrase inhibitor, acetazolamide, to furosemide water restored urine pH along with renal K+ clearance and plasma [K+] to control levels. Acetazolamide plus furosemide also restored the cortical expression of BK-β4 and BK-α in connecting tubules. These results indicate that in mice adapted to HK, furosemide reduces BK-αβ4-mediated K+ secretion by acidifying the urine.

scholarly journals Determination of Epithelial Na+ Channel Subunit Stoichiometry from Single-Channel Conductances

2007 ◽  
Vol 130 (1) ◽  
pp. 55-70 ◽  
Author(s):  
Arun Anantharam ◽  
Lawrence G. Palmer
Keyword(s):  
Single Channel ◽  
Transition Amplitude ◽  
Single Species ◽  
Na Channel ◽  
Channel Measurements ◽  
Wild Type ◽  
Α Subunit ◽  
Subunit Stoichiometry ◽  
Current Transition ◽  
Epithelial Na Channel

The epithelial Na+ channel (ENaC) is a multimeric membrane protein consisting of three subunits, α, β, and γ. The total number of subunits per functional channel complex has been described variously to follow either a tetrameric arrangement of 2α:1β:1γ or a higher-ordered stoichiometry of 3α:3β:3γ. Therefore, while it is clear that all three ENaC subunits are required for full channel activity, the number of the subunits required remains controversial. We used a new approach, based on single-channel measurements in Xenopus oocytes to address this issue. Individual mutations that alter single-channel conductance were made in pore-lining residues of ENaC α, β, or γ subunits. Recordings from patches in oocytes expressing a single species, wild type or mutant, of α, β, and γ showed a well-defined current transition amplitude with a single Gaussian distribution. When cRNAs for all three wild-type subunits were mixed with an equimolar amount of a mutant α-subunit (either S589D or S592T), amplitudes corresponding to pure wild-type or mutant conductances could be observed in the same patch, along with a third intermediate amplitude most likely arising from channels with at least one wild-type and at least 1 mutant α-subunit. However, intermediate or hybrid conductances were not observed with coexpression of wild-type and mutant βG529A or γG534E subunits. Our results support a tetrameric arrangement of ENaC subunits where 2α, 1β, and 1γ come together around central pore.

Dietary Potassium Intake and Mortality in a Prospective Hemodialysis Cohort

2020 ◽  
Author(s):  
Yoko Narasaki ◽  
Yusuke Okuda ◽  
Sara S. Kalantar ◽  
Amy S. You ◽  
Alejandra Novoa ◽  
...  
Keyword(s):  
Potassium Intake ◽  
Dietary Potassium

scholarly journals Differential Effects of Protein Kinase C on the Levels of Epithelial Na+Channel Subunit Proteins

2000 ◽  
Vol 275 (33) ◽  
pp. 25760-25765 ◽  
Author(s):  
James D. Stockand ◽  
Hui-Fang Bao ◽  
Julie Schenck ◽  
Bela Malik ◽  
Pam Middleton ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Na Channel ◽  
Differential Effects ◽  
Kinase C ◽  
Epithelial Na Channel

scholarly journals CRISPR/Cas9 Mediated Knock Down of δ-ENaC Blunted the TNF-Induced Activation of ENaC in A549 Cells

2021 ◽  
Vol 22 (4) ◽  
pp. 1858
Author(s):  
Waheed Shabbir ◽  
Nermina Topcagic ◽  
Mohammed Aufy ◽  
Murat Oz
Keyword(s):  
A549 Cells ◽  
Na Channel ◽  
Na Current ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Knock Down ◽  
Whole Cell Patch Clamp ◽  
Glycosylation Sites ◽  
Epithelial Na Channel

Tumor necrosis factor (TNF) is known to activate the epithelial Na+ channel (ENaC) in A549 cells. A549 cells are widely used model for ENaC research. The role of δ-ENaC subunit in TNF-induced activation has not been studied. In this study we hypothesized that δ-ENaC plays a major role in TNF-induced activation of ENaC channel in A549 cells which are widely used model for ENaC research. We used CRISPR/Cas 9 approach to knock down (KD) the δ-ENaC in A549 cells. Western blot and immunofluorescence assays were performed to analyze efficacy of δ-ENaC protein KD. Whole-cell patch clamp technique was used to analyze the TNF-induced activation of ENaC. Overexpression of wild type δ-ENaC in the δ-ENaC KD of A549 cells restored the TNF-induced activation of whole-cell Na+ current. Neither N-linked glycosylation sites nor carboxyl terminus domain of δ-ENaC was necessary for the TNF-induced activation of whole-cell Na+ current in δ-ENaC KD of A549 cells. Our data demonstrated that in A549 cells the δ-ENaC plays a major role in TNF-induced activation of ENaC.

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