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Johnston JG, Welch AK, Cain BD, Sayeski PP, Gumz ML, Wingo CS. Aldosterone: Renal Action and Physiological Effects. Compr Physiol 2023; 13:4409-4491. [PMID: 36994769 DOI: 10.1002/cphy.c190043] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.
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Affiliation(s)
- Jermaine G Johnston
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Amanda K Welch
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Brian D Cain
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
| | - Peter P Sayeski
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
| | - Michelle L Gumz
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
| | - Charles S Wingo
- Division of Nephrology, Hypertension and Renal Transplantation, Department of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
- Nephrology Section, Veteran Administration Medical Center, North Florida/South Georgia Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, Florida, USA
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A higher level of serum furin indicates a higher risk of microalbuminuria: results from a longitudinal study in Chinese adults. Clin Exp Nephrol 2020; 24:885-892. [PMID: 32770419 DOI: 10.1007/s10157-020-01912-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 06/01/2020] [Indexed: 01/02/2023]
Abstract
BACKGROUND Furin, a key enzyme of natriuretic peptide system, has been suggested to play a role in microalbuminuria, but the association between furin and microalbuminuria has been scarcely studied. METHODS Leveraging a longitudinal cohort of Chinese adults who had urinary albumin measured twice 4 years apart, we examined the cross-sectional and prospective associations of baseline serum furin with microalbuminuria, adjusting for age, sex, education level, smoking, drinking, obesity, blood pressure, glucose, lipids, and antihypertensive medications. RESULTS The cross-sectional analysis in 2175 participants (53 ± 10 years, 38% men) found that a 10-time higher level of serum furin was significantly associated with a 64% higher risk of having microalbuminuria (OR = 1.64, P = 0.005). The longitudinal analysis found a positive association between baseline serum furin and dynamic elevation of albumin excretion during follow-up. The prospective analysis in 1357 participants free of microalbuminuria at baseline found that a 10-time higher level of serum furin at baseline was significantly associated with a 1.28-time higher risk of developing microalbuminuria 4 years later (OR = 2.28, P < 0.001). CONCLUSIONS A higher level of serum furin at baseline predicted an increased risk of developing microalbuminuria in Chinese adults. These findings indicate that furin might be a predictor or a risk factor for microalbuminuria but the causality still needs more investigations.
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Association of Genetic Variation in the Epithelial Sodium Channel Gene with Urinary Sodium Excretion and Blood Pressure. Nutrients 2018; 10:nu10050612. [PMID: 29757959 PMCID: PMC5986492 DOI: 10.3390/nu10050612] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 11/17/2022] Open
Abstract
This study was performed to investigate whether genetic variation in the epithelial sodium channel (ENaC) is associated with 24-h urinary sodium excretion and blood pressure. A total of 3345 participants of the KoGES_Ansan and Ansung study were eligible for this study. Genomic DNA samples were isolated from peripheral blood and genotyped on the Affymetrix Genome-Wide Human SNP Array 5.0. Thirty-four single nucleotide polymorphisms (SNPs) were extracted for gene regions (SCNN1A, SCNN1B, and SCNN1G) as additive components by using Plink. Twenty-four-hour sodium excretions were estimated from spot urine samples using the Tanaka formula. The general linear model (GLM) was applied to assess the association between SNPs and urinary sodium excretion or blood pressure. In the SCNN1G gene, six SNPs (rs4073291, rs12934362, rs7404408, rs4494543, rs5735, and rs6497657) were significantly different in 24-h urinary sodium excretion according to gene variants. However, no difference was found in blood pressure among participants with gene variants of ENaC. Our finding indicated that 24-h urinary sodium excretions were different according to variants of the SCNN1G gene in large samples. Further studies to replicate these findings are warranted.
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Harvey BJ, Thomas W. Aldosterone-induced protein kinase signalling and the control of electrolyte balance. Steroids 2018; 133:67-74. [PMID: 29079406 DOI: 10.1016/j.steroids.2017.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 10/18/2017] [Accepted: 10/21/2017] [Indexed: 01/20/2023]
Abstract
Aldosterone acts through the mineralocorticoid receptor (MR) to modulate gene expression in target tissues. In the kidney, the principal action of aldosterone is to promote sodium conservation in the distal nephron and so indirectly enhance water conservation under conditions of hypotension. Over the last twenty years the rapid activation of protein kinase signalling cascades by aldosterone has been described in various tissues. This review describes the integration of rapid protein kinase D signalling responses with the non-genomic actions of aldosterone and transcriptional effects of MR activation.
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Affiliation(s)
- Brian J Harvey
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education Centre, Beaumont Hospital, Dublin, Ireland
| | - Warren Thomas
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education Centre, Beaumont Hospital, Dublin, Ireland; Perdana University - Royal College of Surgeons in Ireland School of Medicine, Serdang, Selangor, Malaysia.
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Lou Y, Zhang F, Luo Y, Wang L, Huang S, Jin F. Serum and Glucocorticoid Regulated Kinase 1 in Sodium Homeostasis. Int J Mol Sci 2016; 17:ijms17081307. [PMID: 27517916 PMCID: PMC5000704 DOI: 10.3390/ijms17081307] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 08/02/2016] [Accepted: 08/03/2016] [Indexed: 12/13/2022] Open
Abstract
The ubiquitously expressed serum and glucocorticoid regulated kinase 1 (SGK1) is tightly regulated by osmotic and hormonal signals, including glucocorticoids and mineralocorticoids. Recently, SGK1 has been implicated as a signal hub for the regulation of sodium transport. SGK1 modulates the activities of multiple ion channels and carriers, such as epithelial sodium channel (ENaC), voltage-gated sodium channel (Nav1.5), sodium hydrogen exchangers 1 and 3 (NHE1 and NHE3), sodium-chloride symporter (NCC), and sodium-potassium-chloride cotransporter 2 (NKCC2); as well as the sodium-potassium adenosine triphosphatase (Na+/K+-ATPase) and type A natriuretic peptide receptor (NPR-A). Accordingly, SGK1 is implicated in the physiology and pathophysiology of Na+ homeostasis. Here, we focus particularly on recent findings of SGK1’s involvement in Na+ transport in renal sodium reabsorption, hormone-stimulated salt appetite and fluid balance and discuss the abnormal SGK1-mediated Na+ reabsorption in hypertension, heart disease, edema with diabetes, and embryo implantation failure.
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Affiliation(s)
- Yiyun Lou
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
- Department of Gynaecology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou 310007, Zhejiang, China.
| | - Fan Zhang
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
| | - Yuqin Luo
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
| | - Liya Wang
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
| | - Shisi Huang
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
| | - Fan Jin
- Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, Zhejiang, China.
- Key Laboratory of Reproductive Genetics, National Ministry of Education (Zhejiang University), Women's Reproductive Healthy Laboratory of Zhejiang Province, Hangzhou 310058, Zhejiang, China.
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Caffeine intake antagonizes salt sensitive hypertension through improvement of renal sodium handling. Sci Rep 2016; 6:25746. [PMID: 27173481 PMCID: PMC4866033 DOI: 10.1038/srep25746] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 04/15/2016] [Indexed: 01/05/2023] Open
Abstract
High salt intake is a major risk factor for hypertension. Although acute caffeine intake produces moderate diuresis and natriuresis, caffeine increases the blood pressure (BP) through activating sympathetic activity. However, the long-term effects of caffeine on urinary sodium excretion and blood pressure are rarely investigated. Here, we investigated whether chronic caffeine administration antagonizes salt sensitive hypertension by promoting urinary sodium excretion. Dahl salt-sensitive (Dahl-S) rats were fed with high salt diet with or without 0.1% caffeine in drinking water for 15 days. The BP, heart rate and locomotor activity of rats was analyzed and urinary sodium excretion was determined. The renal epithelial Na+ channel (ENaC) expression and function were measured by in vivo and in vitro experiments. Chronic consumption of caffeine attenuates hypertension induced by high salt without affecting sympathetic nerve activity in Dahl-S rats. The renal α-ENaC expression and ENaC activity of rats decreased after chronic caffeine administration. Caffeine increased phosphorylation of AMPK and decrease α-ENaC expression in cortical collecting duct cells. Inhibiting AMPK abolished the effect of caffeine on α-ENaC. Chronic caffeine intake prevented the development of salt-sensitive hypertension through promoting urinary sodium excretion, which was associated with activation of renal AMPK and inhibition of renal tubular ENaC.
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Lu X, Wang F, Liu M, Yang KT, Nau A, Kohan DE, Reese V, Richardson RS, Yang T. Activation of ENaC in collecting duct cells by prorenin and its receptor PRR: involvement of Nox4-derived hydrogen peroxide. Am J Physiol Renal Physiol 2015; 310:F1243-50. [PMID: 26697985 DOI: 10.1152/ajprenal.00492.2015] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 12/15/2015] [Indexed: 11/22/2022] Open
Abstract
The collecting duct (CD) has been recognized as an important source of prorenin/renin, and it also expresses (pro)renin receptor (PRR). The goal of this study was to examine the hypothesis that prorenin or renin via PRR regulates epithelial Na(+) channel (ENaC) activity in mpkCCD cells. Transepithelial Na(+) transport was measured by using a conventional epithelial volt-ohmmeter and was expressed as the calculated equivalent current (Ieq). Amiloride-inhibitable Ieq was used as a reflection of ENaC activity. Administration of prorenin in the nanomolar range induced a significant increase in Ieq that was detectable as early as 1 min, peaked at 5 min, and gradually returned to baseline within 15 min. These changes in Ieq were completely prevented by a newly developed PRR decoy inhibitor, PRO20. Prorenin-induced Ieq was inhibitable by amiloride. Compared with prorenin, renin was less effective in stimulating Ieq Prorenin-induced Ieq was attenuated by apocynin but enhanced by tempol, the latter effect being prevented by catalase. In response to prorenin treatment, the levels of total reactive oxygen species and H2O2 were both increased, as detected by spin-trap analysis and reactive oxygen species (ROS)-Glo H2O2 assay, respectively. Both siRNA-mediated Nox4 knockdown and the dual Nox1/4 inhibitor GKT137892 attenuated prorenin-induced Ieq Overall, our results demonstrate that activation of PRR by prorenin stimulates ENaC activity in CD cells via Nox4-derived H2O2.
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Affiliation(s)
- Xiaohan Lu
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Fei Wang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Mi Liu
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
| | - Kevin T Yang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Adam Nau
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Donald E Kohan
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Van Reese
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Russell S Richardson
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and
| | - Tianxin Yang
- Institute of Hypertension, Sun Yat-Sen University School of Medicine, Guangzhou, China; and Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, Utah
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Abstract
Aldosterone is a major regulator of Na(+) absorption and acts primarily by controlling the epithelial Na(+) channel (ENaC) function at multiple levels including transcription. ENaC consists of α, β, and γ subunits. In the classical model, aldosterone enhances transcription primarily by activating mineralocorticoid receptor (MR). However, how aldosterone induces chromatin alternation and thus leads to gene activation or repression remains largely unknown. Emerging evidence suggests that Dot1a-Af9 complex plays an important role in repression of αENaC by directly binding and modulating targeted histone H3 K79 hypermethylation at the specific subregions of αENaC promoter. Aldosterone impairs Dot1a-Af9 formation by decreasing expression of Dot1a and Af9 and by inducing Sgk1, which, in turn, phosphorylates Af9 at S435 to weaken Dot1a-Af9 interaction. MR counterbalances Dot1a-Af9 action by competing with Dot1a for binding Af9. Af17 derepresses αENaC by competitively interacting with Dot1a and facilitating Dot1a nuclear export. Consistently, MR(-/-) mice have impaired ENaC expression at day 5 after birth, which may contribute to progressive development of pseudohypoaldosteronism type 1 in a later stage. Af17(-/-) mice have decreased ENaC expression, renal Na(+) retention, and blood pressure. In contrast, Dot1l(AC) mice have increased αENaC expression, despite a 20% reduction of the principal cells. This chapter reviews these findings linking aldosterone action to ENaC transcription through chromatin modification. Future direction toward the understanding the role of Dot1a-Af9 complex beyond ENaC regulation, in particular, in renal fibrosis is also briefly discussed.
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Affiliation(s)
- Lihe Chen
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, USA; Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Xi Zhang
- Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Wenzheng Zhang
- Graduate School of Biomedical Sciences, The University of Texas Health Science Center at Houston, Houston, Texas, USA; Division of Renal Diseases and Hypertension, Department of Internal Medicine, University of Texas Medical School at Houston, Houston, Texas, USA.
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Hypertensive epigenetics: from DNA methylation to microRNAs. J Hum Hypertens 2015; 29:575-82. [PMID: 25631220 DOI: 10.1038/jhh.2014.132] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/18/2014] [Accepted: 12/09/2014] [Indexed: 01/13/2023]
Abstract
The major epigenetic features of mammalian cells include DNA methylation, posttranslational histone modifications and RNA-based mechanisms including those controlled by small non-coding RNAs (microRNAs (miRNAs)). An important aspect of epigenetic mechanisms is that they are potentially reversible and may be influenced by nutritional-environmental factors and through gene-environment interactions. Studies on epigenetic modulations could help us understand the mechanisms involved in essential hypertension and further prevent it's progress. This review is focused on new knowledge on the role of epigenetics, from DNA methylation to miRNAs, in essential hypertension.
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Fu Y, Vallon V. Mineralocorticoid-induced sodium appetite and renal salt retention: evidence for common signaling and effector mechanisms. Nephron Clin Pract 2014; 128:8-16. [PMID: 25376899 DOI: 10.1159/000368264] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
An increase in renal sodium chloride (salt) retention and an increase in sodium appetite are the body's responses to salt restriction or depletion in order to restore salt balance. Renal salt retention and increased sodium appetite can also be maladaptive and sustain the pathophysiology in conditions like salt-sensitive hypertension and chronic heart failure. Here we review the central role of the mineralocorticoid aldosterone in both the increase in renal salt reabsorption and sodium appetite. We discuss the working hypothesis that aldosterone activates similar signaling and effector mechanisms in the kidney and brain, including the mineralocorticoid receptor, the serum- and glucocorticoid-induced kinase SGK1, the ubiquitin ligase NEDD4-2, and the epithelial sodium channel ENaC. The latter also mediates the gustatory salt sensing in the tongue, which is required for the manifestation of increased salt intake. Effects of aldosterone on both the brain and kidney synergize with the effects of angiotensin II. Thus, mineralocorticoids appear to induce similar molecular pathways in the kidney, brain, and possibly tongue, which could provide opportunities for more effective therapeutic interventions. Inhibition of renal salt reabsorption is compensated by stimulation of salt appetite and vice versa; targeting both mechanisms should be more effective. Inhibiting the arousal to consume salty food may improve a patient's compliance to reducing salt intake. While a better understanding of the molecular mechanisms is needed and will provide new therapeutic options, current pharmacological interventions that target both salt retention and sodium appetite include mineralocorticoid receptor antagonists and potentially inhibitors of angiotensin II and ENaC.
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Affiliation(s)
- Yiling Fu
- Department of Medicine, University of California San Diego, La Jolla, Calif., USA
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Associations of epithelial sodium channel genes with blood pressure: the GenSalt study. J Hum Hypertens 2014; 29:224-8. [PMID: 25231509 PMCID: PMC4357546 DOI: 10.1038/jhh.2014.78] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 06/25/2014] [Accepted: 07/18/2014] [Indexed: 01/19/2023]
Abstract
In order to investigate associations of SCNN1A, SCNN1G and SCNN1B genes with blood pressure (BP) in Han Chinese population, we included 2 880 participants did not use antihypertensive medication in the month prior to the baseline survey in the current analysis. Forty-four tag-SNPs in epithelial sodium channel (ENaC) genes were selected and genotyped and nine BP measurements were obtained during 3-day examination. In single-marker analyses, we identified significant associations of SCNN1A marker rs13306613 with diastolic BP (DBP) and SCNN1B marker rs12447134 with systolic BP (SBP) under codominant model after Bonferroni correction (P= 2.82×10−5 and 4.63×10−4, respectively). In addition, 5 SNPs in SCNN1G and 4 SNPs in SCNN1B achieved nominal significance for SBP, DBP or mean arterial pressure (MAP) under the additive model. For example, the minor C allele of rs5735 in SCNN1G gene was associated with decreased SBP, DBP and MAP (P=0.016, 5.41×10−3, and 4.36×10−3, respectively). Gene-based results showed significant associations of SCNN1G and SCNN1Bwith BP levels. This study suggested that ENaC genes play important roles in BP regulation in the Han Chinese population. Future studies are warranted to replicate these findings and functional studies are needed to identify true causal variants in ENaC genes.
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Abstract
Aldosterone regulates blood pressure through its effects on the kidney and the cardiovascular system. Dysregulation of aldosterone signalling can result in hypertension which in turn can lead to chronic pathologies of the kidney such as renal fibrosis and nephropathy. Aldosterone acts by binding to the mineralocorticoid receptor (MR), which acts as a ligand-dependent transcription factor in target tissues such as segments of the distal nephron including the connecting tubule and cortical collecting duct (CCD). Aldosterone also promotes the activation of protein kinase signalling cascades that are coupled to growth factor receptors and act directly on specific substrates in the cell membrane or cytoplasm. The rapid actions of aldosterone can also modulate gene expression through the phosphorylation of transcription factors. Aldosterone is a key regulator of Na(+) conservation in the distal nephron, largely through multiple mechanisms that modulate the activity of the epithelial Na(+) channel (ENaC). Aldosterone transcriptionally up-regulates the ENaCα subunit and also up regulates serum and glucocorticoid-regulated kinase-1 (SGK1) that indirectly regulates the ubiquitination of ENaC subunits. Aldosterone promotes the activation of protein kinase D1 (PKD1) which can modify the activity of ENaC and other transporters through effects on sub-cellular trafficking. In M1-CCD cells, early sub-cellular trafficking causes the redistribution of ENaC subunits within minutes of treatment with aldosterone. ENaC subunits can also interact directly with phosphatidylinositide signalling intermediates in the membrane and the mechanism by which PKD isoforms regulate protein trafficking is through the control of vesicle fission from the trans Golgi network by activation of phosphatidylinositol 4-kinaseIIIβ (PI4KIIIβ).
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Affiliation(s)
- Sinéad Quinn
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland
| | - Brian J Harvey
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland
| | - Warren Thomas
- Molecular Medicine Laboratories, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland.
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Capdevila JH, Pidkovka N, Mei S, Gong Y, Falck JR, Imig JD, Harris RC, Wang W. The Cyp2c44 epoxygenase regulates epithelial sodium channel activity and the blood pressure responses to increased dietary salt. J Biol Chem 2013; 289:4377-86. [PMID: 24368771 DOI: 10.1074/jbc.m113.508416] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Hypertension is a major risk factor for cerebral, cardiovascular, and renal disease, and its prevalence and devastating consequences raises a need for new strategies for its early diagnosis and treatment. We show here that lack of a Cyp2c44 epoxygenase causes dietary salt-sensitive hypertension, a common form of the human disease. Cyp2c44(-/-) mice on normal salt diets are normotensive but become hypertensive when fed high salt. Hypertensive Cyp2c44(-/-) mice show a hyperactive kidney epithelial sodium channel (ENaC) and reductions in ERK1/2 and ENaC subunit phosphorylation. The demonstration that amiloride, an ENaC inhibitor, lowers the blood pressure of hypertensive Cyp2c44(-/-) mice identifies a role for the channel in the hypertensive phenotype of the animals. These studies: (a) identify an antihypertensive role for the kidney Cyp2c44 epoxygenase and for its epoxyeicosatrienoic acid (EET) metabolites in the in vivo control of ENaC activity and the activation of mitogenic kinase pathways; (b) provide evidence for a Cyp2c44 epoxygenase, EET-mediated mechanism of ENaC regulation involving an ERK1/2-catalyzed threonine phosphorylation of the channel γ subunit: and (c) characterize a common scientific platform that could explain the seemingly unrelated biological activities attributed to the epoxygenase metabolites in cell proliferation, angiogenesis, channel activity, and blood pressure control. It is expected that these results will serve as a basis for the development of novel strategies for the early diagnosis and treatment of hypertension and of pathophysiologies associated with dysfunctional mitogenic signaling.
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Affiliation(s)
- Jorge H Capdevila
- From the Department of Medicine, Vanderbilt University, Nashville Tennessee 37232
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Christensen EI, Wagner CA, Kaissling B. Uriniferous tubule: structural and functional organization. Compr Physiol 2013; 2:805-61. [PMID: 23961562 DOI: 10.1002/cphy.c100073] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The uriniferous tubule is divided into the proximal tubule, the intermediate (thin) tubule, the distal tubule and the collecting duct. The present chapter is based on the chapters by Maunsbach and Christensen on the proximal tubule, and by Kaissling and Kriz on the distal tubule and collecting duct in the 1992 edition of the Handbook of Physiology, Renal Physiology. It describes the fine structure (light and electron microscopy) of the entire mammalian uriniferous tubule, mainly in rats, mice, and rabbits. The structural data are complemented by recent data on the location of the major transport- and transport-regulating proteins, revealed by morphological means(immunohistochemistry, immunofluorescence, and/or mRNA in situ hybridization). The structural differences along the uriniferous tubule strictly coincide with the distribution of the major luminal and basolateral transport proteins and receptors and both together provide the basis for the subdivision of the uriniferous tubule into functional subunits. Data on structural adaptation to defined functional changes in vivo and to genetical alterations of specified proteins involved in transepithelial transport importantly deepen our comprehension of the correlation of structure and function in the kidney, of the role of each segment or cell type in the overall renal function,and our understanding of renal pathophysiology.
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Pidkovka N, Rao R, Mei S, Gong Y, Harris RC, Wang WH, Capdevila JH. Epoxyeicosatrienoic acids (EETs) regulate epithelial sodium channel activity by extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated phosphorylation. J Biol Chem 2013; 288:5223-31. [PMID: 23283969 DOI: 10.1074/jbc.m112.407981] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The epithelial sodium channel (ENaC) participates in the regulation of plasma sodium and volume, and gain of function mutations in the human channel cause salt-sensitive hypertension. Roles for the arachidonic acid epoxygenase metabolites, the epoxyeicosatrienoic acids (EETs), in ENaC activity have been identified; however, their mechanisms of action remain unknown. In polarized M1 cells, 14,15-EET inhibited amiloride-sensitive apical to basolateral sodium transport as effectively as epidermal growth factor (EGF). The EET effects were associated with increased threonine phosphorylation of the ENaC β and γ subunits and abolished by inhibitors of (a) mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal regulated kinases 1 and 2 (MEK/ERK1/2) and (b) EGF receptor signaling. CYP2C44 epoxygenase knockdown blunted the sodium transport effects of EGF, and its 14,15-EET metabolite rescued the knockdown phenotype. The relevance of these findings is indicated by (a) the hypertension that results in mice administered cetuximab, an inhibitor of EGF receptor binding, and (b) immunological data showing an association between the pressure effects of cetuximab and reductions in ENaCγ phosphorylation. These studies (a) identify an ERK1/2-dependent mechanism for ENaC inhibition by 14,15-EET, (b) point to ENaC as a proximal target for EET-activated ERK1/2 mitogenic kinases, (c) characterize a mechanistic commonality between EGF and epoxygenase metabolites as ENaC inhibitors, and (d) suggest a CYP2C epoxygenase-mediated pathway for the regulation of distal sodium transport.
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Affiliation(s)
- Nataliya Pidkovka
- Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA
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16
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Watt GB, Ismail NAS, Caballero AG, Land SC, Wilson SM. Epithelial Na⁺ channel activity in human airway epithelial cells: the role of serum and glucocorticoid-inducible kinase 1. Br J Pharmacol 2012; 166:1272-89. [PMID: 22250980 PMCID: PMC3417446 DOI: 10.1111/j.1476-5381.2012.01860.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Revised: 11/24/2011] [Accepted: 12/05/2011] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Glucocorticoids appear to control Na⁺ absorption in pulmonary epithelial cells via a mechanism dependent upon serum and glucocorticoid-inducible kinase 1 (SGK1), a kinase that allows control over the surface abundance of epithelial Na⁺ channel subunits (α-, β- and γ-ENaC). However, not all data support this model and the present study re-evaluates this hypothesis in order to clarify the mechanism that allows glucocorticoids to control ENaC activity. EXPERIMENTAL APPROACH Electrophysiological studies explored the effects of agents that suppress SGK1 activity upon glucocorticoid-induced ENaC activity in H441 human airway epithelial cells, whilst analyses of extracted proteins explored the associated changes to the activities of endogenous protein kinase substrates and the overall/surface expression of ENaC subunits. KEY RESULTS Although dexamethasone-induced (24 h) ENaC activity was dependent upon SGK1, prolonged exposure to this glucocorticoid did not cause sustained activation of this kinase and neither did it induce a coordinated increase in the surface abundance of α-, β- and γ-ENaC. Brief (3 h) exposure to dexamethasone, on the other hand, did not evoke Na⁺ current but did activate SGK1 and cause SGK1-dependent increases in the surface abundance of α-, β- and γ-ENaC. CONCLUSIONS AND IMPLICATIONS Although glucocorticoids activated SGK1 and increased the surface abundance of α-, β- and γ-ENaC, these responses were transient and could not account for the sustained activation of ENaC. The maintenance of ENaC activity did, however, depend upon SGK1 and this protein kinase must therefore play an important but permissive role in glucocorticoid-induced ENaC activation.
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Affiliation(s)
- Gordon B Watt
- Centre for Cardiovascular and Lung Research, Division of Medical Sciences, College of Medicine, Dentistry & Nursing, University of Dundee, Dundee, UK
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17
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Soundararajan R, Lu M, Pearce D. Organization of the ENaC-regulatory machinery. Crit Rev Biochem Mol Biol 2012; 47:349-59. [PMID: 22506713 DOI: 10.3109/10409238.2012.678285] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The control of fluid and electrolyte homeostasis in vertebrates requires the integration of a diverse set of signaling inputs, which control epithelial Na(+) transport, the principal ionic component of extracellular fluid. The key site of regulation is a segment of the kidney tubules, frequently termed the aldosterone-sensitive distal nephron, wherein the epithelial Na(+) channel (or ENaC) mediates apical ion entry. Na(+) transport in this segment is strongly regulated by the salt-retaining hormone, aldosterone, which acts through the mineralocorticoid receptor (MR) to influence the expression of a selected set of target genes, most notably the serine-threonine kinase SGK1, which phosphorylates and inhibits the E3 ubiquitin ligase Nedd4-2. It has long been known that ENaC activity is tightly regulated in vertebrate epithelia. Recent evidence suggests that SGK1 and Nedd4-2, along with other ENaC-regulatory proteins, physically associate with each other and with ENaC in a multi-protein complex. The various components of the complex are regulated by diverse signaling networks, including steroid receptor-, PI3-kinase-, mTOR-, and Raf-MEK-ERK-dependent pathways. In this review, we focus on the organization of the targets of these pathways by multi-domain scaffold proteins and lipid platforms into a unified complex, thereby providing a molecular basis for signal integration in the control of ENaC.
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Affiliation(s)
- Rama Soundararajan
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, CA 94143, USA
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18
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Soundararajan R, Pearce D, Ziera T. The role of the ENaC-regulatory complex in aldosterone-mediated sodium transport. Mol Cell Endocrinol 2012; 350:242-7. [PMID: 22101317 PMCID: PMC3270213 DOI: 10.1016/j.mce.2011.11.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/11/2011] [Accepted: 11/03/2011] [Indexed: 12/29/2022]
Abstract
The mineralocorticoid aldosterone is indispensable for the control of blood pressure and fluid volume in mammals. It acts in large part to increase the abundance and activity of the epithelial Na(+) channel (ENaC), which mediates apical Na(+) entry in the distal parts of the kidney tubules. Aldosterone acts through the mineralocorticoid receptor to alter the transcription of specific genes, including SGK1 and GILZ1. Recent evidence suggests that these key aldosterone-regulated factors function within a unique multi-protein ENaC-regulatory-complex that governs the net cell surface expression and activity of the channel. Another aldosterone-induced protein, CNK3 (connector enhancer of kinase suppressor of Ras 3), also stimulates ENaC and has all of the features of a scaffolding protein. With these observations in mind, we discuss the possibility that CNK3 coordinates the dynamic assembly of the ENaC-regulatory-complex, and promotes context-appropriate aldosterone signal transduction in the regulation of epithelial Na(+) transport.
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Affiliation(s)
- Rama Soundararajan
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
| | - David Pearce
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California 94143
| | - Tim Ziera
- Division of Nephrology, Department of Medicine, University of California San Francisco, San Francisco, California 94143
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Borsting E, Cheng VPC, Glass CK, Vallon V, Cunard R. Peroxisome proliferator-activated receptor-γ agonists repress epithelial sodium channel expression in the kidney. Am J Physiol Renal Physiol 2011; 302:F540-51. [PMID: 22169011 DOI: 10.1152/ajprenal.00306.2011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Thiazolidinediones (TZDs), known as peroxisome proliferator-activated receptor (PPAR) agonists, are used to treat type 2 diabetes. However, ∼5% of patients experience the treatment-limiting side effect of edema. Studies have implicated activation of the epithelial sodium channel (ENaC) as a cause of TZD-induced fluid retention, although there have been conflicting reports. The goal of this study was to resolve the role of PPARγ in control of ENaC isoforms in the kidney. Herein, we demonstrate in mice that rosiglitazone (RGZ), a PPARγ ligand, increases body weight and abdominal fat pad fluid content and reduces hematocrit. Seven days of RGZ decreases ENaCα and ENaCβ mRNA and ENaCγ protein expression in the kidney cortex, and acute treatment for 5 h with pioglitazone, another potent TZD, does not increase renal ENaC isoform mRNA or protein expression. Pioglitazone also decreases ENaCα and ENaCγ mRNA expression in a cortical collecting duct cell line. As no direct transcriptional studies had been conducted, we examined the PPARγ-dependent regulation of ENaC. Pioglitazone represses ENaCγ promoter activity, and this repression is partially relieved by inhibition of protein synthesis. Chromatin immunoprecipitation assays revealed that repression is associated with a decrease in histone H4K5 acetylation at the proximal ENaCγ promoter. In summary, TZDs do not increase ENaC mRNA expression in the kidney, and in fact repress the ENaCγ promoter via an indirect transcriptional mechanism.
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Affiliation(s)
- Emily Borsting
- Research and Medicine Services, Div. of Nephrology, Veterans Affairs San Diego Healthcare System, San Diego, CA 92161, USA
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20
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Gumz ML, Cheng KY, Lynch IJ, Stow LR, Greenlee MM, Cain BD, Wingo CS. Regulation of αENaC expression by the circadian clock protein Period 1 in mpkCCD(c14) cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1799:622-9. [PMID: 20868778 DOI: 10.1016/j.bbagrm.2010.09.003] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Revised: 07/23/2010] [Accepted: 09/15/2010] [Indexed: 11/24/2022]
Abstract
The epithelial sodium channel (ENaC) mediates the fine-tuned regulation of external sodium (Na) balance. The circadian clock protein Period 1 (Per1) is an aldosterone-induced gene that regulates mRNA expression of the rate-limiting alpha subunit of ENaC (αENaC). In the present study, we examined the effect of Per1 on αENaC in the cortex, the site of greatest ENaC activity in the collecting duct, and examined the mechanism of Per1 action on αENaC. Compared to wild type mice, Per1 knockout mice exhibited a 50% reduction of steady state αENaC mRNA levels in the cortex. Importantly, siRNA-mediated knockdown of Per1 decreased total αENaC protein levels in mpkCCD(c14) cells, a widely used model of the murine cortical collecting duct (CCD). Per1 regulated basal αENaC expression and participated in the aldosterone-mediated regulation of αENaC in mpkCCD(c14) cells. Because circadian clock proteins mediate their effects as part of multi-protein complexes at E-box response elements in the promoters of target genes, the ability of Per1 to interact with these sequences from the αENaC promoter was tested. For the first time, we show that Per1 and Clock are present at an E-box response element found in the αENaC promoter. Together these data support an important role for the circadian clock protein Per1 in the direct regulation of αENaC transcription and have important implications for understanding the role of the circadian clock in the regulation of renal function.
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21
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Renauld S, Tremblay K, Ait-Benichou S, Simoneau-Roy M, Garneau H, Staub O, Chraïbi A. Stimulation of ENaC Activity by Rosiglitazone is PPARγ-Dependent and Correlates with SGK1 Expression Increase. J Membr Biol 2010; 236:259-70. [DOI: 10.1007/s00232-010-9297-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 08/10/2010] [Indexed: 02/02/2023]
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22
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Reisenauer MR, Anderson M, Huang L, Zhang Z, Zhou Q, Kone BC, Morris AP, Lesage GD, Dryer SE, Zhang W. AF17 competes with AF9 for binding to Dot1a to up-regulate transcription of epithelial Na+ channel alpha. J Biol Chem 2010; 284:35659-69. [PMID: 19864429 DOI: 10.1074/jbc.m109.038448] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
We previously reported that Dot1a.AF9 complex represses transcription of the epithelial Na(+) channel subunit alpha (alpha-ENaC) gene in mouse inner medullary collecting duct mIMCD3 cells and mouse kidney. Aldosterone relieves this repression by down-regulating the complex through various mechanisms. Whether these mechanisms are sufficient and conserved in human cells or can be applied to other aldosterone-regulated genes remains largely unknown. Here we demonstrate that human embryonic kidney 293T cells express the three ENaC subunits and all of the ENaC transcriptional regulators examined. These cells respond to aldosterone and display benzamil-sensitive Na(+) currents, as measured by whole-cell patch clamping. We also show that AF17 and AF9 competitively bind to the same domain of Dot1a in multiple assays and have antagonistic effects on expression of an alpha-ENaC promoter-luciferase construct. Overexpression of Dot1a or AF9 decreased mRNA expression of the ENaC subunits and their transcriptional regulators and reduced benzamil-sensitive Na(+) currents. AF17 overexpression caused the opposite effects, accompanied by redirection of Dot1a from the nucleus to the cytoplasm and reduction in histone H3 K79 methylation. The nuclear export inhibitor leptomycin B blocked the effect of AF17 overexpression on H3 K79 hypomethylation. RNAi-mediated knockdown of AF17 yielded nuclear enrichment of Dot1a and histone H3 K79 hypermethylation. As with AF9, AF17 displays nuclear and cytoplasmic co-localization with Sgk1. Therefore, AF17 competes with AF9 to bind Dot1a, decreases Dot1a nuclear expression by possibly facilitating its nuclear export, and relieves Dot1a.AF9-mediated repression of alpha-ENaC and other target genes.
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Affiliation(s)
- Mary Rose Reisenauer
- Department of Internal Medicine, University of Texas Health Science Center, Houston, Texas 77030, USA
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23
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Loffing J, Korbmacher C. Regulated sodium transport in the renal connecting tubule (CNT) via the epithelial sodium channel (ENaC). Pflugers Arch 2009; 458:111-35. [PMID: 19277701 DOI: 10.1007/s00424-009-0656-0] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 02/18/2009] [Accepted: 02/22/2009] [Indexed: 12/29/2022]
Abstract
The aldosterone-sensitive distal nephron (ASDN) includes the late distal convoluted tubule 2, the connecting tubule (CNT) and the collecting duct. The appropriate regulation of sodium (Na(+)) absorption in the ASDN is essential to precisely match urinary Na(+) excretion to dietary Na(+) intake whilst taking extra-renal Na(+) losses into account. There is increasing evidence that Na(+) transport in the CNT is of particular importance for the maintenance of body Na(+) balance and for the long-term control of extra-cellular fluid volume and arterial blood pressure. Na(+) transport in the CNT critically depends on the activity and abundance of the amiloride-sensitive epithelial sodium channel (ENaC) in the luminal membrane of the CNT cells. As a rate-limiting step for transepithelial Na(+) transport, ENaC is the main target of hormones (e.g. aldosterone, angiotensin II, vasopressin and insulin/insulin-like growth factor 1) to adjust transepithelial Na(+) transport in this tubular segment. In this review, we highlight the structural and functional properties of the CNT that contribute to the high Na(+) transport capacity of this segment. Moreover, we discuss some aspects of the complex pathways and molecular mechanisms involved in ENaC regulation by hormones, kinases, proteases and associated proteins that control its function. Whilst cultured cells and heterologous expression systems have greatly advanced our knowledge about some of these regulatory mechanisms, future studies will have to determine the relative importance of the various pathways in the native tubule and in particular in the CNT.
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24
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Hasler U. Controlled aquaporin-2 expression in the hypertonic environment. Am J Physiol Cell Physiol 2009; 296:C641-53. [PMID: 19211910 DOI: 10.1152/ajpcell.00655.2008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The corticomedullary osmolality gradient is the driving force for water reabsorption occurring in the kidney. In the collecting duct, this gradient allows luminal water to move across aquaporin (AQP) water channels, thereby increasing urine concentration. However, this same gradient exposes renal cells to great osmotic challenges. These cells must constantly adapt to fluctuations of environmental osmolality that challenge cell volume and incite functional change. This implies profound alterations of cell phenotype regarding water permeability. AQP2 is an essential component of the urine concentration mechanism whose controlled expression dictates apical water permeability of collecting duct principal cells. This review focuses on changes of AQP2 abundance and trafficking in hypertonicity-challenged cells. Intracellular mechanisms governing these events are discussed and the biological relevance of altered AQP2 expression by hypertonicity is outlined.
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Affiliation(s)
- Udo Hasler
- Service de Néphrologie, Fondation pour Recherches Médicales, 64 Ave. de la Roseraie, CH-1211, Geneva 4, Switzerland.
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25
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Vasquez MM, Castro R, Seidner SR, Henson BM, Ashton DJ, Mustafa SB. Induction of serum- and glucocorticoid-induced kinase-1 (SGK1) by cAMP regulates increases in alpha-ENaC. J Cell Physiol 2008; 217:632-42. [PMID: 18615584 DOI: 10.1002/jcp.21534] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Alpha-ENaC expression and activity is regulated by a variety of hormones including beta-adrenergic agonists via the second messenger cAMP. We evaluated the early intermediate pathways involved in the up-regulation of SGK1 by DbcAMP and whether SGK1 is a prerequisite for induction of alpha-ENaC expression. Submandibular gland epithelial (SMG-C6) cells treated with DbcAMP (1 mM) induced both SGK1 mRNA and protein expression. DbcAMP-stimulated SGK1 mRNA expression was decreased by actinomycin D and mRNA and protein expressions were attenuated by PKA inhibitors (H-89 and KT5720). Inhibition of PI3-K with either LY294002 or dominant negative PI3-K reduced DbcAMP-stimulated SGK1 protein and mRNA levels, attenuated the phosphorylation of CREB (a cAMP-activated transcription factor) and decreased alpha-ENaC protein levels and Na(+) transport. In addition, the combination of PKA inhibitors with dominant negative PI3-K synergistically inhibited DbcAMP-induced Na(+) transport. Inhibition of SGK1 expression by siRNA decreased but did not obliterate DbcAMP-induced alpha-ENaC expression. Thus, in a cell line which endogenously exhibits minimal alpha-ENaC expression, induction of SGK1 by DbcAMP occurs via the PI3-K and PKA pathways. Increased alpha-ENaC levels and function are partly dependent upon the early induction of SGK1 expression.
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Affiliation(s)
- Margarita M Vasquez
- Department of Pediatrics/Division of Neonatology, University of Texas Health Science Center, San Antonio, Texas 78229, USA.
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26
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Araki N, Umemura M, Miyagi Y, Yabana M, Miki Y, Tamura K, Uchino K, Aoki R, Goshima Y, Umemura S, Ishigami T. Expression, transcription, and possible antagonistic interaction of the human Nedd4L gene variant: implications for essential hypertension. Hypertension 2008; 51:773-7. [PMID: 18268134 DOI: 10.1161/hypertensionaha.107.102061] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Net sodium balances in humans are maintained through various ion transporters expressed along the entire nephron. Among these ion transporters, epithelial sodium channels (ENaC) located along the aldosterone-sensitive distal nephron (ASDN) play a pivotal role in the homeostasis of sodium balance. This is supported by analyses of inherited hypertensive disorders, showing that genes encoding ENaC and other modulatory proteins cause hereditary hypertension, such as Liddle syndrome. Among various modulating proteins, E3 ubiquitin ligase, Nedd4L, binds the PY motif of ENaC COOH terminals and catalyzes ubiquitination of the NH(2) terminus of the protein for subsequent degradation. Both evolutionarily conserved and evolutionarily new C2 domains of human Nedd4L, a cryptic splice variant resulting in a disrupted isoform product formed by a frame-shift mutation, were reported previously. We focused on one of the isoforms, isoform I, generated by SNP (rs4149601), and studied its expression and interactions with other isoforms by molecular biological, immunohistochemical, and electrophysiological methods. We found that isoform I may interact with other human isoforms in a dominant-negative fashion. Such interactions might abnormally increase sodium reabsorption. Taken together, our analyses suggest that the human Nedd4L gene, especially the evolutionarily new isoform I, is a candidate gene for hypertension.
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Affiliation(s)
- Naomi Araki
- Department of Medical Science and Cardio-Renal Medicine, Yokohama City University Graduate School of Medicine, Kanagawa-ken, Japan
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27
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Zhang W, Xia X, Reisenauer MR, Rieg T, Lang F, Kuhl D, Vallon V, Kone BC. Aldosterone-induced Sgk1 relieves Dot1a-Af9-mediated transcriptional repression of epithelial Na+ channel alpha. J Clin Invest 2007; 117:773-83. [PMID: 17332896 PMCID: PMC1804379 DOI: 10.1172/jci29850] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Accepted: 01/02/2007] [Indexed: 01/17/2023] Open
Abstract
Aldosterone plays a major role in the regulation of salt balance and the pathophysiology of cardiovascular and renal diseases. Many aldosterone-regulated genes--including that encoding the epithelial Na+ channel (ENaC), a key arbiter of Na+ transport in the kidney and other epithelia--have been identified, but the mechanisms by which the hormone modifies chromatin structure and thus transcription remain unknown. We previously described the basal repression of ENaCalpha by a complex containing the histone H3 Lys79 methyltransferase disruptor of telomeric silencing alternative splice variant a (Dot1a) and the putative transcription factor ALL1-fused gene from chromosome 9 (Af9) as well as the release of this repression by aldosterone treatment. Here we provide evidence from renal collecting duct cells and serum- and glucocorticoid-induced kinase-1 (Sgk1) WT and knockout mice that Sgk1 phosphorylated Af9, thereby impairing the Dot1a-Af9 interaction and leading to targeted histone H3 Lys79 hypomethylation at the ENaCalpha promoter and derepression of ENaCalpha transcription. Thus, Af9 is a physiologic target of Sgk1, and Sgk1 negatively regulates the Dot1a-Af9 repressor complex that controls transcription of ENaCalpha and likely other aldosterone-induced genes.
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Affiliation(s)
- Wenzheng Zhang
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Xuefeng Xia
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Mary Rose Reisenauer
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Timo Rieg
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Florian Lang
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Dietmar Kuhl
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Volker Vallon
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
| | - Bruce C. Kone
- Departments of Internal Medicine and Integrative Biology and Pharmacology, University of Texas Medical School at Houston, Houston, Texas, USA.
Departments of Medicine and Pharmacology, University of California, San Diego, and VA Medical Center, San Diego, California, USA.
Department of Physiology, University of Tübingen, Tübingen, Germany.
Department of Biology, Chemistry, and Pharmacy, Free University Berlin, Berlin, Germany.
Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, Houston, Texas, USA
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Abstract
Recent investigations point to an important role for peptidases in regulating transcellular ion transport by the epithelial Na(+) channel, ENaC. Several peptidases, including furins and proteasomal hydrolases, modulate ENaC maturation and disposal. More idiosyncratically, apical Na(+) transport by ENaC in polarized epithelia of kidney, airway, and gut is stimulated constitutively by one or more trypsin-family serine peptidases, as revealed by inhibition of amiloride-sensitive Na(+) transport by broad-spectrum antipeptidases, including aprotinin and bikunin/SPINT2. In vitro, the transporting activity of aprotinin-suppressed ENaC can be restored by exposure to trypsin. The prototypical channel-activating peptidase (CAP) is a type 1 membrane-anchored tryptic peptidase first identified in Xenopus kidney cells. Frog CAP1 strongly upregulates Na(+) transport when coexpressed with ENaC in oocytes. The amphibian enzyme's apparent mammalian orthologue is prostasin, otherwise known as CAP1, which is coexpressed with ENaC in a variety of epithelia. In airway cells, prostasin is the major basal regulator of ENaC activity, as suggested by inhibition and knockdown experiments. Other candidate regulators of mature ENaC include CAP2/TMPRSS4 and CAP3/matriptase (also known as membrane-type serine protease 1/ST14). Mammalian CAPs are potential targets for treatment of ENaC-mediated Na(+) hyperabsorption by the airway in cystic fibrosis (CF) and by the kidney in hypertension. CAPs can be important for mammalian development, as indicated by embryonic lethality in mice with null mutations of CAP1/prostasin. Mice with selectively knocked out expression of CAP1/prostasin in the epidermis and mice with globally knocked out expression of CAP3/matriptase exhibit phenotypically similar defects in skin barrier function and neonatal death from dehydration. In rats, transgenic overexpression of human prostasin disturbs salt balance and causes hypertension. Thus, several converging lines of evidence indicate that ENaC function is regulated by peptidases, and that such regulation is critical for embryonic development and adult function of organs such as skin, kidney, and lung.
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Affiliation(s)
- Carole Planès
- INSERM U773, Centre de Recherche Biomédicale Bichat-Beaujon (CRB3), Université Paris 7, 75018 Paris, France
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Sorkina T, Miranda M, Dionne KR, Hoover BR, Zahniser NR, Sorkin A. RNA interference screen reveals an essential role of Nedd4-2 in dopamine transporter ubiquitination and endocytosis. J Neurosci 2006; 26:8195-205. [PMID: 16885233 PMCID: PMC6673793 DOI: 10.1523/jneurosci.1301-06.2006] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The function of the dopamine transporter (DAT) to terminate dopamine neurotransmission is regulated by endocytic trafficking of DAT. To elucidate the mechanisms of DAT endocytosis, we generated a fully functional mutant of the human DAT in which a hemagglutinin epitope (HA) was incorporated into the second extracellular loop. The endocytosis assay, based on the uptake of an HA antibody, was designed to study constitutive- and protein kinase C (PKC)-dependent internalization of HA-DAT expressed in non-neuronal cells and rat dopaminergic neurons. Large-scale RNA interference analysis of PKC-dependent endocytosis of HA-DAT revealed the essential and specific role of an E3 ubiquitin ligase, Nedd4-2 (neural precursor cell expressed, developmentally downregulated 4-2), as well as the involvement of adaptor proteins present in clathrin-coated pits, such as epsin, Eps15 (epidermal growth factor pathway substrate clone 15), and Eps15R (Eps15-related protein). Depletion of Nedd4-2 resulted in a dramatic reduction of PKC-dependent ubiquitination of DAT. Endogenous Nedd4-2, epsin, and Eps15 were coimmunoprecipitated with heterologously expressed human HA-DAT and endogenous DAT isolated from rat striatum. A new mechanistic model of DAT endocytosis is proposed whereby the PKC-induced ubiquitination of DAT mediated by Nedd4-2 leads to interaction of DAT with adaptor proteins in coated pits and acceleration of DAT endocytosis.
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Zhang W, Xia X, Reisenauer MR, Hemenway CS, Kone BC. Dot1a-AF9 complex mediates histone H3 Lys-79 hypermethylation and repression of ENaCalpha in an aldosterone-sensitive manner. J Biol Chem 2006; 281:18059-68. [PMID: 16636056 PMCID: PMC3015183 DOI: 10.1074/jbc.m601903200] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Aldosterone is a major regulator of epithelial Na(+) absorption and acts in large part through induction of the epithelial Na(+) channel (ENaC) gene in the renal collecting duct. We previously identified Dot1a as an aldosterone early repressed gene and a repressor of ENaCalpha transcription through mediating histone H3 Lys-79 methylation associated with the ENaCalpha promoter. Here, we report a novel aldosterone-signaling network involving AF9, Dot1a, and ENaCalpha. AF9 and Dot1a interact in vitro and in vivo as evidenced in multiple assays and colocalize in the nuclei of mIMCD3 renal collecting duct cells. Overexpression of AF9 results in hypermethylation of histone H3 Lys-79 at the endogenous ENaCalpha promoter at most, but not all subregions examined, repression of endogenous ENaCalpha mRNA expression and acts synergistically with Dot1a to inhibit ENaCalpha promoter-luciferase constructs. In contrast, RNA interference-mediated knockdown of AF9 causes the opposite effects. Chromatin immunoprecipitation assays reveal that overexpressed FLAG-AF9, endogenous AF9, and Dot1a are each associated with the ENaCalpha promoter. Aldosterone negatively regulates AF9 expression at both mRNA and protein levels. Thus, Dot1a-AF9 modulates histone H3 Lys-79 methylation at the ENaCalpha promoter and represses ENaCalpha transcription in an aldosterone-sensitive manner. This mechanism appears to be more broadly applicable to other aldosterone-regulated genes because overexpression of AF9 alone or in combination with Dot1a inhibited mRNA levels of three other known aldosterone-inducible genes in mIMCD3 cells.
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Affiliation(s)
- Wenzheng Zhang
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Xuefeng Xia
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Mary Rose Reisenauer
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Charles S. Hemenway
- Department of Pediatrics and the Tulane Cancer Center, Tulane University School of Medicine, New Orleans, Louisiana 70112
| | - Bruce C. Kone
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, Texas 77030
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas 77030
- Department of The Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, University of Texas Health Science Center at Houston, Houston, Texas 77030
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31
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Sheng S, Carattino MD, Bruns JB, Hughey RP, Kleyman TR. Furin cleavage activates the epithelial Na+channel by relieving Na+self-inhibition. Am J Physiol Renal Physiol 2006; 290:F1488-96. [PMID: 16449353 DOI: 10.1152/ajprenal.00439.2005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Epithelial Na+channels (ENaC) are inhibited by extracellular Na+, a process referred to as Na+self-inhibition. We previously demonstrated that mutation of key residues within two furin cleavage consensus sites in α, or one site in γ, blocked subunit proteolysis and inhibited channel activity when mutant channels were expressed in Xenopus laevis oocytes (Hughey RP, Bruns JB, Kinlough CL, Harkleroad KL, Tong Q, Carattino MD, Johnson JP, Stockand JD, and Kleyman TR. J Biol Chem 279: 18111–18114, 2004). Cleavage of subunits was also blocked by these mutations when expressed in Madin-Darby canine kidney cells, and both subunit cleavage and channel activity were blocked when wild-type subunits were expressed in furin-deficient Chinese hamster ovary cells. We now report that channels with mutant α-subunits lacking either one or both furin cleavage sites exhibited a marked enhancement of the Na+self-inhibition response, while channels with a mutant γ-subunit showed a modestly enhanced Na+self-inhibition response. Analysis of Na+self-inhibition at varying [Na+] indicates that channels containing mutant α-subunits exhibit an increased Na+affinity. At the single-channel level, channels with a mutant α-subunit had a low open probability ( Po) in the presence of a high external [Na+] in the patch pipette. Podramatically increased when trypsin was also present, or when a low external [Na+] was in the patch pipette. Our results suggest that furin cleavage of ENaC subunits activates the channels by relieving Na+self-inhibition and that activation requires that the α-subunit be cleaved twice. Moreover, we demonstrate for the first time a clear relationship between ENaC Poand extracellular [Na+], supporting the notion that Na+self-inhibition reflects a Poreduction due to high extracellular [Na+].
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Affiliation(s)
- Shaohu Sheng
- Dept. of Medicine, Univ. of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Saxena SK, Singh M, Shibata H, Kaur S, George C. Rab4 GTP/GDP modulates amiloride-sensitive sodium channel (ENaC) function in colonic epithelia. Biochem Biophys Res Commun 2005; 340:726-33. [PMID: 16389071 DOI: 10.1016/j.bbrc.2005.12.036] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Accepted: 12/06/2005] [Indexed: 01/02/2023]
Abstract
The sodium-selective amiloride-sensitive epithelial sodium channel (ENaC) mediates electrogenic sodium re-absorption in tight epithelia. ENaC expression at the plasma membrane requires regulated transport, processing, and macromolecular assembly of subunit proteins in a defined and highly compartmentalized manner. Ras-related Rab GTPases monitor these processes in a highly regulated sequence of events. In order to evaluate the role of Rab proteins in ENaC function, Rab4 wild-type (WT), the GTPase-deficient mutant Rab4Q67L, and the dominant negative GDP-locked mutant Rab4S22N were over-expressed in the colon cancer cell line, HT-29 and amiloride-sensitive currents were recorded. Rab4 over-expression inhibited amiloride-sensitive currents. The effect was reversed by introducing Rab4-neutralizing antibody and Rab4 specific SiRNA. The GDP-locked Rab4 mutant inhibited, while GTPase-deficient mutant moderately stimulated amiloride-sensitive currents. Active status of Rab4 was confirmed by GTP overlay assay, while its expression was verified by Western blotting. Immunoprecipitation and pull-down assay suggest protein-protein interaction between Rab4 and ENaC. In addition, the functional modulation coincides with concomitant changes in ENaC expression at the cell surface and in intracellular pool. We propose that Rab4 is a critical element that regulates ENaC function by mechanisms that include GTP-GDP status, recycling, and expression level. Our observations imply that channel expression in apical membranes of epithelial cell system incorporates RabGTPase as an essential determinant of channel function and adds an exciting paradigm to ENaC therapeutics.
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Affiliation(s)
- Sunil K Saxena
- Center for Cell and Molecular Biology, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
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Bianchi G. Genetic variations of tubular sodium reabsorption leading to “primary” hypertension: from gene polymorphism to clinical symptoms. Am J Physiol Regul Integr Comp Physiol 2005; 289:R1536-49. [PMID: 16278339 DOI: 10.1152/ajpregu.00441.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The definition of the most appropriate strategy to demonstrate causation of a given genetic-molecular mechanism in a complex multifactorial polygenic disease like hypertension is hampered by the underestimation of the complexity arising from the genetic and environmental interactions. To disentangle this complexity, we developed a strategy based on six steps: 1) isolation of a rodent model of hypertension (Milan hypertensive strain and Milan normotensive strain) that shares some pathophysiological abnormalities with human primary hypertension; 2) definition in the model of the sequence of events linking these abnormalities to a genetic molecular mechanism; 3) determination of the polymorphism of the three adducin genes discovered in the model both in rats and in humans; 4) comparison at biochemical and physiological levels between the rodent models and the hypertensive carriers of the “mutated” gene variants; 5) evaluation of the impact of the adducin genes in hypertension and its organ complications with association and linkage studies in humans, also considering the genetic and environmental interactions; and 6) development of a pharmacogenomic approach aimed at establishing the therapeutic benefit of a drug interfering with the sequence of events triggered by adducin and their effect's size. The bulk of data obtained demonstrates the importance of a multidisciplinary approach considering a variety of genetic and environmental interactions. Adducin functions within the cells as a heterodimer composed of a combination of three subunits. Each of these subunits is coded by genes mapping to different chromosomes. Therefore, the interaction among these genes, taken together with the interactions with other modulatory genes or with the environment, is indispensable to establish the adducin clinical impact. The hypothesis that adducin polymorphism favors the development of hypertension via an increased tubular sodium reabsorption is well supported by a series of consistent experimental and clinical data. Many mechanistic aspects, underlying the link between these genes and clinical symptoms, need to be clarified. The clinical effect size of adducin must be established also with the contribution of pharmacogenomics with a drug that selectively interferes with the sequence of events triggered by the mutated adducin.
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Affiliation(s)
- Giuseppe Bianchi
- School of Nephrology, Univ. Vita Salute San Raffaele, Division of Nephrology, Dialysis and Hypertension, San Raffaele Hospital, Via Olgettina 60, 20132 Milan, Italy.
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Umadevi N, Kumar S, Narayana N. Crystallization and preliminary X-ray diffraction studies of the WW4 domain of the Nedd4-2 ubiquitin-protein ligase. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:1084-6. [PMID: 16511241 PMCID: PMC1978143 DOI: 10.1107/s174430910503767x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 11/16/2005] [Indexed: 11/11/2022]
Abstract
Ubiquitin-mediated protein modification via covalent attachment of ubiquitin has emerged as one of the most common regulatory processes in all eukaryotes. Nedd4-2, closely related to neuronal precursor cell-expressed developmentally down-regulated 4 (Nedd4), is a multimodular ubiquitin-protein ligase comprised of four WW domains and a Hect domain. The WW domains recognize the proline-rich motifs on the multi-subunit amiloride-sensitive epithelial sodium channel (ENaC). To gain insights into the binding of the WW domain to proline-rich peptides, a protein fragment (78 amino acids) containing the fourth WW domain (WW4) of the Nedd4-2 protein was purified and crystallized and X-ray diffraction data were collected. A data set was obtained to 2.5 A resolution from a cryocooled single crystal at a synchrotron source. The crystals belong to the tetragonal space group P4(1)2(1)2 (or P4(3)2(1)2), with unit-cell parameters a = b = 113.43, c = 103.21 A. Analysis of the self-rotation function suggests the presence of four WW4 molecules in the asymmetric unit, with a high unit-cell solvent content of 74%.
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Affiliation(s)
- N. Umadevi
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
| | - S. Kumar
- Hanson Institute, IMVS, PO Box 14, Rundle Mall, Adelaide, SA 5000, Australia
| | - N. Narayana
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
- Correspondence e-mail:
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Thomas CP, Liu KZ, Vats HS. Medroxyprogesterone acetate binds the glucocorticoid receptor to stimulate alpha-ENaC and sgk1 expression in renal collecting duct epithelia. Am J Physiol Renal Physiol 2005; 290:F306-12. [PMID: 16189295 DOI: 10.1152/ajprenal.00062.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Medroxyprogesterone acetate (MPA), a widely used synthetic progestational contraceptive, occasionally leads to Cushingoid side effects such as hypertension, fluid retention, and centripetal obesity. We investigated the effect of MPA on classic mineralocorticoid target genes, alpha-epithelial Na channel (ENaC) and sgk1, in the collecting duct. In adrenalectomized mice, aldosterone, dexamethasone, and MPA increased alpha-ENaC mRNA levels in kidney cortex. MPA and dexamethasone, but not progesterone, dose dependently increased alpha-ENaC and sgk1 mRNA in M-1 and in Madin-Darby canine kidney-C7 cells, both collecting duct cell lines. The stimulatory effect of MPA and dexamethasone on alpha-ENaC expression was inhibited by RU-38486, a combined glucocorticoid receptor (GR) and progesterone receptor (PR) antagonist, but not by Org31710, a pure PR antagonist. MPA and dexamethasone dose dependently increased alpha-ENaC promoter-driven luciferase activity in M-1 cells, which was not inhibited by Org31710, indicating that MPA regulates alpha-ENaC in a PR-independent manner. When tested in HT29 cells, MPA could only stimulate alpha-ENaC-driven reporter activity when GR was coexpressed, confirming the requirement for functional GR in the transcriptional effect of MPA. The activation of steroid receptors such as GR can explain the apparent glucocorticoid effects of MPA, independent of PR activation.
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Affiliation(s)
- Christie P Thomas
- Division of Nephrology, Department of Internal Medicine, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242-1081, USA.
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36
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Bhalla V, Daidié D, Li H, Pao AC, LaGrange LP, Wang J, Vandewalle A, Stockand JD, Staub O, Pearce D. Serum- and glucocorticoid-regulated kinase 1 regulates ubiquitin ligase neural precursor cell-expressed, developmentally down-regulated protein 4-2 by inducing interaction with 14-3-3. Mol Endocrinol 2005; 19:3073-84. [PMID: 16099816 DOI: 10.1210/me.2005-0193] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Serum- and glucocorticoid-regulated kinase 1 (SGK1) is an aldosterone-regulated early response gene product that regulates the activity of several ion transport proteins, most notably that of the epithelial sodium channel (ENaC). Recent evidence has established that SGK1 phosphorylates and inhibits Nedd4-2 (neural precursor cell-expressed, developmentally down-regulated protein 4-2), a ubiquitin ligase that decreases cell surface expression of the channel and possibly stimulates its degradation. The mechanistic basis for this SGK1-induced Nedd4-2 inhibition is currently unknown. In this study we show that SGK1-mediated phosphorylation of Nedd4-2 induces its interaction with members of the 14-3-3 family of regulatory proteins. Through functional characterization of Nedd4-2-mutant proteins, we demonstrate that this interaction is required for SGK1-mediated inhibition of Nedd4-2. The concerted action of SGK1 and 14-3-3 appears to disrupt Nedd4-2-mediated ubiquitination of ENaC, thus providing a mechanism by which SGK1 modulates the ENaC-mediated Na(+) current. Finally, the expression pattern of 14-3-3 is also consistent with a functional role in distal nephron Na(+) transport. These results demonstrate a novel, physiologically significant role for 14-3-3 proteins in modulating ubiquitin ligase-dependent pathways in the control of epithelial ion transport.
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Affiliation(s)
- Vivek Bhalla
- Division of Nephrology, Department of Medicine, University of California-San Francisco, San Francisco, CA 94143-0532, USA
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