The amiloride-sensitive epithelial sodium channel (ENaC) plays a critical role in fluid and electrolyte homeostasis and consists of alpha, beta, and gamma subunits. The carboxyl terminus of each ENaC subunit contains a PPxY, motif which is believed to be important for interaction with the WW domains of the ubiquitin-protein ligase, Nedd4. Disruption of this interaction, as in Liddles syndrome, where mutations delete or alter the PPxY motif of either the beta or gamma subunits, has been proposed to result in increased ENaC activity. Here we present evidence that KIAA0439 protein, a close relative of Nedd4, is also a potential regulator of ENaC. We demonstrate that KIAA0439 WW domains bind all three ENaC subunits. We show that a recombinant KIAA0439 WW domain protein acts as a dominant negative mutant that can interfere with the Na(+)-dependent feedback inhibition of ENaC in whole-cell patch clamp experiments. We propose that KIAA0439 and Nedd4 proteins either play a redundant role in ENaC ...
Statement of the problem: The epithelial sodium channels (ENaC) play an important role in regulation of blood pressure (BP). Although the genes are identical in Dahl salt sensitive (S) and Dahl salt resistant (R) rats, expression of ENaC subunits is increased in kidneys of S rats on high salt diet. Intracerebroventricular (icv) infusion of ENaC blocker benzamil prevents Na+ induced hypertension. It was not known whether ENaC subunits are expressed in the brain and whether or not brain ENaC plays a role in regulation of [Na+] in CNS. Hypothesis: 1. Epithelial sodium channels are expressed in the brain. 2. Expression of ENaC is increased in the kidneys and brain of Dahl S rats on high salt diet. 3. ENaC in the brain contributes to regulation of [Na+] in the CSF and brain interstitium. Methods of investigation: We studied expression and distribution of the ENaC subunits and assessed the effects of icv infusion of Na+-rich aCSF in Wistar rats or high salt diet in Dahl S rats in different areas of ...
TY - JOUR. T1 - A novel tumor necrosis factor-mediated mechanism of direct epithelial sodium channel activation. AU - Czikora, István. AU - Alli, Abdel. AU - Bao, Hui Fang. AU - Kaftan, David. AU - Sridhar, Supriya. AU - Apell, Hans Jürgen. AU - Gorshkov, Boris. AU - White, Richard. AU - Zimmermann, Astrid. AU - Wendel, Albrecht. AU - Pauly-Evers, Meike. AU - Hamacher, Jürg. AU - Garcia-Gabay, Irène. AU - Fischer, Bernhard. AU - Verin, Alexander. AU - Bagi, Zsolt. AU - Pittet, Jean Francois. AU - Shabbir, Waheed. AU - Lemmens-Gruber, Rosa. AU - Chakraborty, Trinad. AU - Lazrak, Ahmed. AU - Matthay, Michael A.. AU - Eaton, Douglas C.. AU - Lucas, Rudolf. PY - 2014/9/1. Y1 - 2014/9/1. N2 - Rationale: Alveolar liquid clearance is regulated by Na+ uptake through the apically expressed epithelial sodium channel (ENaC) and basolaterally localized Na+-K+-ATPase in type II alveolar epithelial cells. Dysfunction of these Na+ transporters during pulmonary inflammation can contribute to pulmonary ...
2015 Elsevier Inc. The epithelial sodium channel (ENaC) plays a critical role in maintaining Na+ homeostasis in various tissues throughout the body. An understanding of the structure of the ENaC subunits has been developed from homology modeling based on the related acid sensing ion channel 1 (ASIC1) protein structure, as well as electrophysiological approaches. However, ENaC has several notable functional differences compared to ASIC1, thereby providing justification for determination of its three-dimensional structure. Unfortunately, this goal remains elusive due to several experimental challenges. Of the subunits that comprise a physiological hetero-trimeric αβγENaC, the α-subunit is unique in that it is capable of forming a homo-trimeric structure that conducts Na+ ions. Despite functional and structural interest in αENaC, a key factor complicating structural studies has been its interaction with multiple other proteins, disrupting its homogeneity. In order to address this issue, a ...
Sigma-Aldrich offers abstracts and full-text articles by [Bettina Krueger, Ursula Schlötzer-Schrehardt, Silke Haerteis, Matthias Zenkel, Verena E Chankiewitz, Kerstin U Amann, Friedrich E Kruse, Christoph Korbmacher].
Autosomal recessive pseudohypoaldosteronism type 1 (PHA1) is a rare disorder characterized by sodium wasting, failure to thrive, hyperkalemia, hypovolemia and metabolic acidosis. It is due to mutations in the amiloride-sensitive epithelial sodium channel (ENaC) and is characterized by diminished response to aldosterone. Patients may present with life-threatening hyperkalemia, which must be recognized and appropriately treated. A 32-year-old female was referred to the National Institutes of Health (NIH) for evaluation of hyperkalemia and muscle pain. Her condition started in the second week of life, when she was brought to an outside hospital lethargic and unresponsive. At that time, she was hypovolemic, hyperkalemic and acidotic, and was eventually treated with sodium bicarbonate and potassium chelation. At the time of the presentation to the NIH, her laboratory evaluation revealed serum potassium 5.1 mmol/l (reference range: 3.4-5.1 mmol/l), aldosterone 2800 ng/dl (reference range: ≤21 ng/dl) ...
The epithelial sodium channel (ENaC) is a protein located at the apical membrane of polarised epithelial cells, primarily expressed in the epithelia of the gastrointestinal tract, lungs and kidney. ENaCs main function is that of absorbing sodium and it is strongly involved in regulating and maintaining total-body salt and water homeostasis, acting as the rate-limiting step for sodium reabsorption into the body. Its activity, therefore, is crucial for determining blood volume and, as a consequence, blood pressure. The sorting and trafficking of ENaC to the apical membrane is a tightly controlled process, requiring the interaction of multiple proteins and organelles. Although ENaC has been well-characterised, there are certain aspects about its trafficking which need to be clarified, such as defining the many proteins involved in the recycling of the channel to and from the apical membrane. A potential, novel candidate involved in ENaC recycling is the retromer complex. This endosome-associated ...
The epithelial sodium channel (short: ENaC, also: amiloride-sensitive sodium channel) is a membrane-bound ion channel that is selectively permeable to Na+ ions and that is assembled as a heterotrimer composed of three homologous subunits α or δ, β, and γ, These subunits are encoded by four genes: SCNN1A, SCNN1B, SCNN1G, and SCNN1D. It is involved primarily in the reabsorption of sodium ions at the collecting ducts of the kidneys nephrons. The apical membranes of many tight epithelia contain sodium channels that are characterized primarily by their high affinity for the diuretic blocker amiloride. These channels mediate the first step of active sodium reabsorption essential for the maintenance of body salt and water homeostasis. In vertebrates, the channels control reabsorption of sodium in kidney, colon, lung and sweat glands; they also play a role in taste perception. ENaC is located in the apical membrane of polarized epithelial cells in particular in the kidney (primarily in the ...
PubMed comprises more than 30 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
Regulation of transepithelial sodium transport by corticosteroids occurs in two phases: early and delayed. The early phase involves the activation and translocation of pre-existing epithelial sodium channels (ENaC); whereas, the delayed phase involves the de novo synthesis of ENaC. An important regulator of the early phase is the serum-and glucocorticoid-inducible kinase (SGK1). The traditional view is that SGK1 is involved in the activation and translocation of ENaC, thereby regulating the early phase of ENaC activity. On the other hand, the possible involvement of SGK1 during the de novo synthesis of ENaC has not been studied. In Chapter 1 we report the role of SGK1 in the delayed phase of corticosteroid regulation of ENaC transcription in cortical collecting duct cells. Using polymerase chain reaction (PCR) we determined that cells over-expressing SGK1 (FL-SGK1) had significantly higher levels of α and βENaC mRNA as compared to cells expressing dominant negative SGK1 (K127M-SGK1). ENaC is a ...
Background: Nearly one-third of the United States adult population suffers from hypertension. Hydrochlorothiazide (HCTZ), one of the most commonly used medications to treat hypertension, has variable efficacy. The renal epithelial sodium channel (ENaC) provides a mechanism for fine-tuning sodium excretion, and is a major regulator of blood pressure homeostasis. DOT1L, MLLT3, SIRT1, and SGK1 encode genes in a pathway that controls methylation of the histone H3 globular domain at lysine 79 (H3K79), thereby modulating expression of the ENaCα subunit. This study aimed to determine the role of variation in these regulatory genes on blood pressure response to HCTZ, and secondarily, untreated blood pressure.Methods: We investigated associations between genetic variations in this candidate pathway and HCTZ blood pressure response in two separate hypertensive cohorts (clinicaltrials.gov NCT00246519 and NCT00005520). In a secondary, exploratory analysis, we measured associations between these same ...
Epithelial Na+ channels historically have been classified according to their kinetics, pharmacology, and single channel conductance (see Palmer, 1992; Smith and Benos, 1991). The molecular identity of these channels was unknown until the cloning of the Na(5) channel (classification of Palmer, 1992) independently by Canessa et al. (1993, 1994), by Lingueglia et al. (1993), and Voilley et al. (1994). This channel is also referred to as the epithelial Na+ channel (ENaC)1 and is characterized by a 5-pS single channel conductance, long open and close times, high amiloride sensitivity (Ki , 100 nM), and high Na+ to K+ selectivity. ENaC is composed of three subunits, α, β, and γ, that are necessary to reconstitute the in vivo single channel properties and maximal amiloride-sensitive currents in Xenopus oocytes (Canessa et al., 1994).. The epithelial Na+ channel shares little molecular homology with other known ion channels (for review see Garty and Palmer, 1997). However, this channel belongs to a ...
Recent studies suggest that the epithelial sodium channel (ENaC) is expressed in the endothelial cells. To test whether high salt affects the NO production via regulation of endothelial ENaC, human umbilical vein endothelial cells (HUVECs) were incubated in solutions containing either normal or high sodium (additional 20 mM NaCl). Our data showed that high sodium treatment significantly increased α-, β-, and γ-ENaC expression levels in HUVECs. Using the cell-attached patch-clamp technique, we demonstrated that high sodium treatment significantly increased ENaC open probability (PO). Moreover, nitric oxide synthase (eNOS) phosphorylation (Ser 1177) levels and NO production were significantly decreased by high sodium in HUVECs; the effects of high sodium on eNOS phosphorylation and NO production were inhibited by a specific ENaC blocker, amiloride. Our results showed that high sodium decreased AMP-activated kinase (AMPK) phosphorylation in endothelial cells. On the other hand, metformin, an ...
In the present study, we confirmed ENaC expression in SDMAs, and we found that ENaC blockers reduced the contractile response to phenylephrine and serotonin. The EC50 values obtained in dose-response experiments with pharmacological ENaC inhibitors are similar to the published inhibition constant and IC50 values for ENaC in mammalian distal nephron segments and Xenopus oocytes expressing α, β, and γ ENaC (amiloride: 10 to 100 nmol/L; benzamil: 10 nmol/L).1,2 In addition, an amiloride derivative (ethyl isopropyl amiloride) did not affect the contractile response to phenylephrine. In situ hybridization and immunohistochemistry studies showed α, β, and γ ENaC expression in the tunica media and endothelial cells of SDMAs. In addition, amiloride-sensitive sodium currents were detected in primary cultures of mesenteric artery endothelial cells. These data indicate expression of all 3 of the ENaC subunits in SDMAs that would form trimeric channels with biophysical properties similar to the ...
The ubiquitin E3 protein ligase Nedd4-2 is a physiological regulator of the epithelial sodium channel ENaC, which is essential for transepithelial Na+ transport and is linked to Liddles syndrome, an autosomal dominant disorder of human salt-sensitive hypertension. Nedd4-2 function is negatively regulated by phosphorylation via a serum- and glucocorticoid-inducible protein kinase (Sgk1), which serves as a mechanism to inhibit the ubiquitination-dependent degradation of ENaC. We report here that 14-3-3 proteins participate in this regulatory process through a direct interaction with a phosphorylated form of human Nedd4-2 (a human gene product of KIAA0439, termed hNedd4-2). The interaction is dependent on Sgk1-catalyzed phosphorylation of hNedd4-2 at Ser-468. We found that this interaction preserved the activity of the Sgk1-stimulated ENaC-dependent Na+ current while disrupting the interaction decreased ENaC density on the Xenopus laevis oocytes surface possibly by enhancing Nedd4-2-mediated ...
... Am J Physiol Renal Physiol. 2014 Nov 12;:ajprenal.00596.2013 Authors: Hyndman KA, Bugaj V, Mironova E, Stockand JD, Pollock JS Abstract With an increase in urine flow there is a significant increase in shear stress against the renal epithelium including the inner medullary col...
PubMed comprises more than 30 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
Join us for the APS Aldosterone and ENaC in Health and Disease: The Kidney and Beyond conference. This in-depth, four-day conference is the ninth in a series on the topic of aldosterone and the epithelial sodium channel (ENaC). Weve scheduled a four-day program of cutting-edge basic, clinical and translational research presented by top scientists in the field. Topic areas include:. ...
Jacquillet, Grégory and Chichger, Havovi and Unwin, Robert J. and Shirley, David G. (2013) Protease stimulation of renal sodium reabsorption in vivo by activation of the collecting duct epithelial sodium channel (ENaC). Nephrology Dialysis Transplantation, 28 (4). pp. 839-845. ISSN 1460-2385 ...
BOSTON and DURHAM, NC - Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) and Parion Sciences today announced that the companies will collaborate to develop investigational epithelial sodium channel (ENaC) inhibitors for the potential treatment of cystic fibrosis (CF) and other pulmonary diseases. Under the agreement, Vertex gains worldwide development and commercial rights to Parions investigational ENaC inhibitors, including P-1037 and P-1055, for CF and other pulmonary diseases. P-1037 is currently being evaluated in an exploratory Phase 2a study in people with CF, regardless of genotype, and Vertex and Parion plan to begin an additional Phase 2a study that adds P-1037 to treatment with the investigational combination of lumacaftor and ivacaftor for people with CF who have two copies of the F508del mutation. Parion will receive an $80 million up-front payment from Vertex with the potential to receive additional development and regulatory milestone payments and tiered royalties related to ...
The renal collecting duct is the nephron segment where the final urine content of acid equivalents and inorganic ions are determined. The role of two different cell types present in this nephron segment has been determined many years ago: principal cells that express the epithelial sodium channel ENaC and aquaporin 2, regulate electrolyte reabsorption, while intercalated cells, which express acid-base transporters and vacuolar H+-ATPase, maintain an apropriate acid-base balance. Recent evidence challenges this historical view. Rather than having independent and non-overlapping functions, the two cell types in the collecting duct appear to functionally cooperate to regulate acid-base and volume homeostasis via complex paracrine and endocrine interplay. This review summarizes these recent findings.
TGF-beta directs trafficking of the epithelial sodium channel ENaC which has implications for ion and fluid transport in acute lung injury ...
Spyryx Biosciences is developing inhaled, peptide therapeutics designed to maintain hydration on the airway surface, for the treatment of cystic fibrosis and
Sigma-Aldrich offers abstracts and full-text articles by [K J Coote, D Paisley, S Czarnecki, M Tweed, H Watson, A Young, R Sugar, M Vyas, N J Smith, U Baettig, P J Groot-Kormelink, M Gosling, R Lock, B Ethell, G Williams, A Schumacher, J Harris, W M Abraham, J Sabater, C T Poll, T Faller, S P Collingwood, H Danahay].
Principal Investigator:ONO Shuichi, Project Period (FY):1997 - 1998, Research Category:Grant-in-Aid for Scientific Research (C), Section:一般, Research Field:Kidney internal medicine
Background/Seeks: The aim of this study was to evaluate the feasibility of -fetoprotein (AFP) as a diagnostic tool for hepatocellular carcinoma (HCC) in Korean patients. patients was 0.757. The sensitivity, specificity, and positive predictive value of AFP was 50.55%, 87.70%, and 80.43%, respectively, at a cut-off of 20 ng/mL; 37.70%, 95.90%, and 90.20%, respectively, at a cut-off of 100 ng/mL, and 30.05%, 97.27%, and 91.67%, respectively, at a cut-off of 200 ng/mL. A cut-off of 100 ng/mL was more sensitive than one of 200 ng/mL with equivalent specificity and positive predictive value. Conclusions: The cut-off AFP value for early-stage HCC was 17.4 ng/mL. Our study cautiously suggests that AFP has a role in the diagnosis of HCC, which the correct worth of AFP for the analysis of HCC may be 100 ng/mL instead of 548472-68-0 supplier 200 ng/mL. check or the Mann-Whitney check for continuous factors. Our research was made to compare the perfect cut-off ideals of AFP by increasing the amount of ...
, ENaC Alpha blocking peptide, GTX88256-PEP, Applications: Apuri, Blocking, ELISA; Affinity purification, Blocking, ELISA; CrossReactivity: Human
Several advancements have been made in delineating the role of NOX 2 and NOX 4 isoforms in ENaC regulation, and further work has explored novel redox-sensitive signal transduction pathways that regulate lung ENaC. In particular, it has been shown that NOX 2 and NOX 4 are expressed in alveolar epithelial type 1 and type 2 cells. Furthermore, gp91phox, the catalytic domain of Rac-1-dependent NOX enzymes, has been coimmunoprecipitated with the α-ENaC subunit (35, 90). The proximity of RS release with active Na+ channel subunit indicates that these unstable, reactive molecules can indeed regulate apically located channels embedded in the cell membrane before targeted dismutation of the RS. Further evidence indicating an important role of NOX-derived RS includes studies in which inhibition of the small G protein Rac-1, using NSC-23766 compound, inhibited both O2·− production and ENaC activity in the alveolar epithelium. In the same study, tracheally instilling NSC-23766 alongside saline ...
Read "Stimulation of ENaC Activity by Rosiglitazone is PPARγ-Dependent and Correlates with SGK1 Expression Increase, The Journal of Membrane Biology" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
A6 model renal epithelial cells were stably transfected with enhanced green fluorescent protein (EGFP)-tagged alpha- or beta-subunits of the epithelial Na(+) channel (ENaC). Transfected RNA and proteins were both expressed in low abundance, similar to the endogenous levels of ENaC in native cells. In living cells, laser scanning confocal microscopy revealed a predominantly subapical distribution of EGFP-labeled subunits, suggesting a readily accessible pool of subunits available to participate in Na(+) transport. The basal level of Na(+) transport in the clonal lines was enhanced two- to fourfold relative to the parent line. Natriferic responses to insulin or aldosterone were similar in magnitude to the parent line, while forskolin-stimulated Na(+) transport was 64% greater than control in both the alpha- and beta-transfected lines. In response to forskolin, EGFP-labeled channel subunits traffic to the apical membrane. These data suggest that channel regulators, not the channel per se, form the rate
This gene encodes a member of the peptidase S1 or chymotrypsin family of serine proteases. The encoded preproprotein is proteolytically processed to generate light and heavy chains that associate via a disulfide bond to form the heterodimeric enzyme. This enzyme is highly expressed in prostate epithelia and is one of several proteolytic enzymes found in seminal fluid. This protease exhibits trypsin-like substrate specificity, cleaving protein substrates at the carboxyl terminus of lysine or arginine residues. The encoded protease partially mediates proteolytic activation of the epithelial sodium channel, a regulator of sodium balance, and may also play a role in epithelial barrier formation. [provided by RefSeq, Feb 2016 ...
TY - JOUR. T1 - Cerebrovascular Consequences of Pseudohyperaldosteronism. AU - Smith, Jonathan H.. AU - Lindor, Noralane Morey. AU - Rabinstein, Alejandro. PY - 2012. Y1 - 2012. N2 - The study of mechanistically defined forms of hypertension may provide insight into the relationship between hypertension and stroke. The author retrospectively studied a cohort of 23 individuals with pseudohyperaldosteronism (PHA), a condition associated with pathologic activation of the distal nephron epithelial sodium channel but low renin and aldosterone levels. During a median follow-up of 11years (range: 1-30), 4 of 23 (17.4%) patients had a cerebrovascular event recorded. Intracranial hemorrhage was not observed in any patient. Cerebrovascular events tended to occur in older patients, minorities, and patients with a later diagnosis of PHA and additional vascular risk factors. In addition to strict blood pressure control, patients with PHA should have early evaluation and treatment of other vascular risk ...
Parion Sciences is developing P 1037 (VX 371), a long-acting inhaled epithelial sodium channel (ENaC) inhibitor, for the treatment of cystic fibrosis (CF) and
Lazrak A, Jurkuvenaite A, Ness EC, Zhang S, Woodworth BA, Muhlebach MS, Stober VP, Lim YP, Garantziotis S, Matalon S.Inter- α-inhibitor blocks epithelial sodium channel activation and decreases nasal potential differences in ΔF508 mice. Am J Respir Cell Mol Biol. 2014 May;50(5):953-62 ...
Rabbit polyclonal antibody raised against recombinant Rat Scnn1b. Recombinant protein corresponding to Scnn1b C-terminus (amino acids 617-638). (PAB28792) - Products - Abnova
At the pinnacle of the companys Global Vision strategy - the reorganization of products into three distinct groups - the Art series has been designed from the get-go as an alternative to the best that the camera brands can offer.. The latest model in the lineup, the 20mm f1.4 DG HSM A is intended to complement the latest high-resolution full-frame DSLRs, and incorporates a complex optical construction consisting of 15 elements in 11 groups. The company says the new 20mm is highly-corrected for sagittal coma flare through the adoption of an optimized layout and aspherical elements. Control of axial (longitudinal) chromatic aberration was also a high priority with this model, and the company explains that it is reduced by careful matching of converging and diverging lenses; however, the 20mm also adopts two FLD (fluorite-like) elements and five ED glass elements to further reduce color fringing. Like the earlier Art series models, it has a sonic-type (HSM) AF motor for smooth and near-silent AF, ...
Experience AMDs newly designed thermal solution - The Wraith Cooler that delivers near-silent operation and is practically inaudible when installed in your PC.
I have an Hitachi 7K1000 in a home server, and it was loud especially considering the system is a very quiet MODT build. I used the Hitachi drive utility Feature Tool v2.08 and changed the firmware settings to low power and quiet and now I consider the drive near-silent. The default settings are for high performance. I am guessing that for such a dramatic drop in sound level, the spindle speeds must be lowered. I havent yet tested the change in power consumption. Does anyone know exactly how the Hitachi firmware accomplishes this reduction? If it does lower spindle speed, then we now have two sources for green and quiet drives ...
TY - JOUR. T1 - The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes. T2 - Dipnoi). AU - Uchiyama, Minoru. AU - Maejima, Sho. AU - Yoshie, Sumio. AU - Kubo, Yoshihiro. AU - Konno, Norifumi. AU - Joss, Jean M P. PY - 2012. Y1 - 2012. N2 - Epithelial sodium channel (ENaC) is a Na+-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na+ absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCα, β and γ proteins. The nENaCα, β and γ subunits are closely related to ...
The amiloride-sensitive epithelial sodium channel (ENaC) is a heteromultimer of three homologous subunits (alpha-, beta-, and gamma- subunits). To study the role of the beta-subunit in vivo, we analyzed mice in which the betaENaC gene locus was disrupted. These mice showed low levels of betaENaC mRNA expression in kidney (approximately 1%), lung (approximately 1%), and colon (approximately 4%). In homozygous mutant betaENaC mice, no betaENaC protein could be detected with immunofluorescent staining. At birth, there was a small delay in lung- liquid clearance that paralleled diminished amiloride-sensitive Na+ absorption in tracheal explants. With normal salt intake, these mice showed a normal growth rate. However, in vivo, adult betaENaC m/m mice exhibited a significantly reduced ENaC activity in colon and elevated plasma aldosterone levels, suggesting hypovolemia and pseudohypoaldosteronism type 1. This phenotype was clinically silent, as betaENaC m/m mice showed no weight loss, normal plasma Na+ and K+
Expression of the α-subunit of the amiloride-sensitive sodium channel (αENaC) is regulated by a number of factors in the lung, including oxygen partial pressure (Po2). As transcriptional activation is a mechanism for raising cellular mRNA levels, we investigated the effect of physiological changes in Po2 on the activity of the redox-sensitive transcription factor nuclear factor κB (NF-κB) and transcriptional activity of 5′-flanking regions of the human αENaC gene using luciferase reporter-gene vectors transiently transfected into human adult alveolar carcinoma A549 cells. By Western blotting we confirmed the presence of NF-κB p65 but not p50 in these cells. Transiently increasing Po2 from 23 to 42mmHg for 24h evoked a significant increase in NF-κB DNA-binding activity and transactivation of a NF-κB-driven luciferase construct (pGLNF-κBpro), which was blocked by the NF-κB activation inhibitor sulphasalazine (5mM). Transcriptional activity of αENaC-luciferase constructs containing ...
The amiloride-sensitive epithelial sodium channel is a highly selective sodium channel that constitutes the rate-limiting step of sodium reabsorption in distal nephrons. It consists of at least 3 subunits (a, /?, and y) of similar structure and plays an important role in sodium and fluid homeostasis. Defects of this channel have been critically implicated in Liddle syndrome (pseudoaldosteronism) and pseudohypoaldosteronism type 1. A sample of 48 individuals from 23 nuclear families was selected from Anhui, China. We sequenced 12 exons and flanking intronic sequences and discovered a new 207-bp intron located in the previously described exon X of Thomas et al. (1996). In addition, 4 novel single nucleotide polymorphisms were identified; 3 were in exon 3 and 1 was in exon 13. Furthermore, 2 base substitutions in exon 13 were present in all the Chinese subjects compared with the published European SCNN1G DNA sequence.
Surprisingly, mammalian genomes encode only eight to nine independent DEG/ENaC subunits, whereas the genomes of the worm C. elegans and various Drosophila species harbor a significantly larger number of DEG/ENaC-like genes [31 in Drosophila melanogaster and 30 in C. elegans (Bazopoulou et al. 2007; Ben-Shahar 2011; Liu et al. 2003a; Liu et al. 2003b; Studer et al. 2011)]. Consequently, DEG/ENaC genes represent one of the largest ion channel families in the Drosophila genome. The high diversification of DEG/ENaC protein sequences across distant animal species makes it difficult to evaluate whether the family expanded in some invertebrate species or whether it contracted in vertebrates. Nevertheless, the remarkable diversity of ppk genes in Drosophila suggests two alternative hypotheses. The first would suggest DEG/ENaC ion channels serve a wider range of physiological functions relative to their roles in mammals. An alternative hypothesis would be that DEG/ENaC channels in Drosophila evolved to ...
Airway disease such as asthma and infection is the cause substantial morbidity and mortality in the world today. Although modern medicine has developed many drugs for these conditions, these diseases remain highly prevalent and are often difficult to treat. Short palate, lung and nasal epithelium clone 1 (SPLUNC1) is an abundant multi-functional protein in the airway. It has been reported to have immune-modulatory, surfactant and anti-microbial functions, and it regulates the airway surface liquid (ASL) height through the epithelial sodium channel (ENaC). This study focuses on utilizing SPLUNC1s protective properties in combatting airway disease. Airway hyperresponsiveness (AHR) is a characteristic feature of asthma, yet its pathophysiology is still poorly understood. SPLUNC1 is dysregulated in allergic rhinitis and chronic rhinosinusitis with nasal polyps. However, SPLUNC1 regulation in asthmatics has not been investigated. Here, we show that in allergic asthmatic humans and house dust mite ...
TY - JOUR. T1 - Differential effects of protein kinase C on the levels of epithelial Na+ channel subunit proteins. AU - Stockand, James D. AU - Hui-Fang, B.. AU - Schenck, J.. AU - Malik, B.. AU - Middleton, P.. AU - Schlanger, L. E.. AU - Eaton, D. C.. PY - 2000/8/18. Y1 - 2000/8/18. N2 - Regulation of epithelial Na+ channel (ENaC) subunit levels by protein kinase C (PKC) was investigated in A6 cells. PKC activation altered ENaC subunit levels, differentially decreasing the levels of both β and γ, but not αENaC. Temporal regulation of β and γENaC by PKC differed; γENaC decreased with a time constant of3.7 ± 1.0 h, whereas βENaC decreased in 13.9 ±3.0h. Activation of PKC also resulted in a decrease in trans-epithelial Na+ reabsorption for up to 48h. PMA activation of PKC resulted in negative feedback inhibition of PKC protein levels beginning within 4h. Both β and γENaC levels, as well as transport tended toward pretreatment values after 48 h of PMA treatment. PKC inhibitors ...
Collecting duct (CD) renin is stimulated by angiotensin (Ang) II, providing a pathway for Ang I generation and further conversion to Ang II. Ang II stimulates the epithelial sodium channel via the Ang II type 1 receptor and increases mineralocorticoid receptor activity attributed to increased aldosterone release. Our objective was to determine whether CD renin augmentation is mediated directly by Ang II type 1 receptor or via the epithelial sodium channel and mineralocorticoid receptor. In vivo studies examined the effects of epithelial sodium channel blockade (amiloride; 5 mg/kg per day) on CD renin expression and urinary renin content in Ang II-infused rats (80 ng/min, 2 weeks). Ang II infusion increased systolic blood pressure, medullary renin mRNA, urinary renin content, and intrarenal Ang II levels. Amiloride cotreatment did not alter these responses despite a reduction in the rate of progression of systolic blood pressure. In primary cultures of inner medullary CD cells, renin mRNA and ...
Using pharmacological screening of a wide spectrum of ion channel antagonists, we found that low concentrations of amiloride inhibited the spiking of water gustatory receptor neurons in Drosophila. Interestingly, several previous studies also demonstrated the effect of amiloride on the spiking of these receptor neurons in the flesh fly and blowfly (Liscia et al., 1997; Sadakata et al., 2002). Using physiological recordings, behavioral assays, and mutational analyses, we identified PPK28 as the putative amiloride-sensitive receptor for gustatory water reception. Further gain-of-function studies showed that PPK28 is sufficient to confer hypoosmotic activity. These results suggest that PPK28 is a good candidate for the Drosophila gustatory water receptor.. The IC50 of amiloride necessary to inhibit the gustatory water response (∼20 μm) was about two orders of magnitude higher than that observed for mammalian ENaC; however, it was comparable to that used for the Drosophila RPK channel (Adams et ...
The SCNN1A gene provides instructions for making one piece, the alpha subunit, of a protein complex called the epithelial sodium channel (ENaC). The channel is composed of alpha, beta, and gamma subunits, each of which is produced from a different gene. These channels are found at the surface of certain cells called epithelial cells in many tissues of the body, including the kidneys, lungs, and sweat glands. The ENaC channel transports sodium into cells.. In the kidney, ENaC channels take sodium into cells in response to signals that sodium levels in the body are too low. From the kidney cells, this sodium is returned to the bloodstream rather than being removed from the body (a process called reabsorption). In addition to regulating the amount of sodium in the body, the flow of sodium ions helps control the movement of water in tissues. For example, ENaC channels in lung cells help regulate the amount of fluid in the lungs. ...
Cholinergic polymodal chemosensory cells in the mammalian urethra (urethral brush cells = UBC) functionally express the canonical bitter and umami taste transduction signaling cascade. Here, we aimed to determine whether UBC are functionally equipped for the perception of salt through ENaC (epithelial sodium channel). Cholinergic UBC were isolated from ChAT-eGFP reporter mice (ChAT = choline acetyltransferase). RT-PCR showed mRNA expression of ENaC subunits Scnn1a, Scnn1b, and Scnn1g in urethral epithelium and isolated UBC. Scnn1a could also be detected by next generation sequencing in 4/6 (66%) single UBC, two of them also expressed the bitter receptor Tas2R108. Strong expression of Scnn1a was seen in some urothelial umbrella cells and in 65% of UBC (30/46 cells) in a Scnn1a reporter mouse strain. Intracellular [Ca2+] was recorded in isolated UBC stimulated with the bitter substance denatonium benzoate (25 mM), ATP (0.5 mM) and NaCl (50 mM, on top of 145 mM Na+ and 153 mM Cl- baseline in ...
Acute lung injury (ALI) leading to acute respiratory distress (ARDS) is a global health concern. ARDS patients have significant pulmonary inflammation leading to flooding of the pulmonary alveoli. This prevents normal gas exchange with consequent hypoxemia, and causes mortality. A thin fluid layer in the alveoli is normal. The maintenance of this thin layer results from fluid movement out of the pulmonary capillaries into the alveolar interstitium driven by vascular hydrostatic pressure and then through alveolar tight junctions. This is then balanced by fluid reabsorption from the alveolar space mediated by transepithelial salt and water transport through alveolar cells. Reabsorption is a two-step process: first, sodium enters via sodium-permeable channels in the apical membranes of alveolar type 1 and 2 cells followed by active extrusion of sodium into the interstitium by the basolateral Na+, K+-ATPase. Anions follow the cationic charge gradient and water follows the salt-induced osmotic