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Ríos-Medina Y, Rico-Chávez P, Martínez-Vieyra I, Durán-Álvarez JC, Rodriguez-Varela M, Rincón-Heredia R, Reyes-López C, Cerecedo D. Altered Plasma Membrane Lipid Composition in Hypertensive Neutrophils Impacts Epithelial Sodium Channel (ENaC) Endocytosis. Int J Mol Sci 2024; 25:4939. [PMID: 38732158 PMCID: PMC11084340 DOI: 10.3390/ijms25094939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 04/22/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
Biological membranes are composed of a lipid bilayer with embedded proteins, including ion channels like the epithelial sodium channel (ENaC), which are critical for sodium homeostasis and implicated in arterial hypertension (HTN). Changes in the lipid composition of the plasma membrane can significantly impact cellular processes related to physiological functions. We hypothesized that the observed overexpression of ENaC in neutrophils from HTN patients might result from alterations in the structuring domains within the plasma membrane, disrupting the endocytic processes responsible for ENaC retrieval. This study assessed the structural lipid composition of neutrophil plasma membranes from HTN patients along with the expression patterns of key elements regulating ENaC at the plasma membrane. Our findings suggest alterations in microdomain structure and SGK1 kinase activity, which could prolong ENaC presence on the plasma membrane. Additionally, we propose that the proteasomal and lysosomal degradation pathways are insufficient to diminish ENaC presence at the plasma membrane in HTN. These results highlight the importance of understanding ENaC retrieval mechanisms and suggest that targeting these mechanisms could provide insights for developing drugs to prevent and treat HTN.
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Affiliation(s)
- Yolanda Ríos-Medina
- Laboratorio de Hematobiología, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07230, Mexico; (Y.R.-M.); (P.R.-C.); (I.M.-V.)
| | - Pedro Rico-Chávez
- Laboratorio de Hematobiología, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07230, Mexico; (Y.R.-M.); (P.R.-C.); (I.M.-V.)
| | - Ivette Martínez-Vieyra
- Laboratorio de Hematobiología, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07230, Mexico; (Y.R.-M.); (P.R.-C.); (I.M.-V.)
| | - Juan C. Durán-Álvarez
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (J.C.D.-Á.); (M.R.-V.)
| | - Mario Rodriguez-Varela
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (J.C.D.-Á.); (M.R.-V.)
| | - Ruth Rincón-Heredia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
| | - César Reyes-López
- Laboratorio de Bioquímica Estructural, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07230, Mexico;
| | - Doris Cerecedo
- Laboratorio de Hematobiología, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07230, Mexico; (Y.R.-M.); (P.R.-C.); (I.M.-V.)
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Fujita H, Adachi C, Inoue T. Cholesterol-load evokes robust calcium response in macrophages: An early event toward cholesterol-induced macrophage death. Cell Calcium 2023; 113:102754. [PMID: 37196488 DOI: 10.1016/j.ceca.2023.102754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/27/2023] [Accepted: 05/09/2023] [Indexed: 05/19/2023]
Abstract
Macrophages in atherosclerotic lesions accumulate large amounts of unesterified cholesterol. Excess cholesterol load leads to cell death of macrophages, which is associated with the progression of atherosclerotic lesions. Calcium depletion in the endoplasmic reticulum (ER) and subsequent pro-apoptotic aberrant calcium signaling are key events in cholesterol-induced macrophage death. Although these concepts imply cytoplasmic calcium events in cholesterol-loaded macrophages, the mechanisms linking cholesterol accumulation to cytoplasmic calcium response have been poorly investigated. Based on our previous finding that extracellularly applied cholesterol evoked robust calcium oscillations in astrocytes, a type of glial cells in the brain, we hypothesized that cholesterol accumulation in macrophages triggers cytoplasmic calcium elevation. Here, we showed that cholesterol application induces calcium transients in THP-1-derived and peritoneal macrophages. Inhibition of inositol 1,4,5-trisphosphate receptors (IP3Rs) and l-type calcium channels (LTCCs) prevented cholesterol-induced calcium transients and ameliorated cholesterol-induced macrophage death. These results suggest that cholesterol-induced calcium transients through IP3Rs and LTCCs are crucial mechanisms underlying cholesterol-induced cell death of macrophages.
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Affiliation(s)
- Hirotaka Fujita
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, 162-8480, Japan
| | - Chihiro Adachi
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, 162-8480, Japan
| | - Takafumi Inoue
- Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Tokyo, 162-8480, Japan.
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Dapagliflozin Treatment Augments Bioactive Phosphatidylethanolamine Concentrations in Kidney Cortex Membrane Fractions of Hypertensive Diabetic db/db Mice and Alters the Density of Lipid Rafts in Mouse Proximal Tubule Cells. Int J Mol Sci 2023; 24:ijms24021408. [PMID: 36674924 PMCID: PMC9865226 DOI: 10.3390/ijms24021408] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/31/2022] [Accepted: 01/04/2023] [Indexed: 01/12/2023] Open
Abstract
In addition to inhibiting renal glucose reabsorption and allowing for glucose excretion, the sodium/glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin may be efficacious in treating various comorbidities associated with type 2 diabetes mellitus (T2DM). The molecular mechanisms by which dapagliflozin exerts its beneficial effects are largely unknown. We hypothesized dapagliflozin treatment in the diabetic kidney alters plasma membrane lipid composition, suppresses extracellular vesicle (EV) release from kidney cells, and disrupts lipid rafts in proximal tubule cells. In order to test this hypothesis, we treated diabetic db/db mice with dapagliflozin (N = 8) or vehicle (N = 8) and performed mass spectrometry-based lipidomics to investigate changes in the concentrations of membrane lipids in the kidney cortex. In addition, we isolated urinary EVs (uEVs) from urine samples collected during the active phase and the inactive phase of the mice and then probed for changes in membrane proteins enriched in the EVs. Multiple triacylglycerols (TAGs) were enriched in the kidney cortex membrane fractions of vehicle-treated diabetic db/db mice, while the levels of multiple phosphatidylethanolamines were significantly higher in similar mice treated with dapagliflozin. EV concentration and size were lesser in the urine samples collected during the inactive phase of dapagliflozin-treated diabetic mice. In cultured mouse proximal tubule cells treated with dapagliflozin, the lipid raft protein caveolin-1 shifted from less dense fractions to more dense sucrose density gradient fractions. Taken together, these results suggest dapagliflozin may regulate lipid-mediated signal transduction in the diabetic kidney.
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Musante I, Scudieri P, Venturini A, Guidone D, Caci E, Castellani S, Conese M, Galietta LJV. Peripheral localization of the epithelial sodium channel in the apical membrane of bronchial epithelial cells. Exp Physiol 2019; 104:866-875. [PMID: 30924990 DOI: 10.1113/ep087590] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/15/2019] [Indexed: 12/14/2022]
Abstract
NEW FINDINGS What is the central question of this study? What is the precise subcellular localization of the epithelial sodium channel (ENaC) in human airway epithelium? What is the main finding and its importance? ENaC protein has an unexpected localization in the peripheral region of the apical membrane of bronchial epithelial cells, very close to tight junctions. This may be important for the mechanism of Na+ absorption ABSTRACT: The epithelial sodium channel (ENaC) has a key role in absorbing fluid across the human airway epithelium. Altered activity of ENaC may perturb the process of mucociliary clearance, thus impairing the innate defence mechanisms against microbial agents. The proteins forming ENaC are present on the apical membrane of the epithelium. However, their precise localization is unknown. In the present study, we used two antibodies recognizing the α and β ENaC subunits. Both antibodies revealed a restricted localization of ENaC in the peripheral region of the apical membrane of cultured bronchial epithelial cells, close to but not overlapping with tight junctions. In contrast, the cystic fibrosis transmembrane conductance regulator chloride channel was more diffusely expressed on the whole apical membrane. Modulation of ENaC activity by aprotinin or elastase resulted in a decrease or increase in the peripheral localization, respectively. Our results suggest that sodium absorption is mainly occurring close to tight junctions where this cation may be rapidly expelled by the Na+ /K+ pump present in lateral membranes. This arrangement of channels and pumps may limit Na+ build-up in other regions of the cells.
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Affiliation(s)
- Ilaria Musante
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Paolo Scudieri
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Arianna Venturini
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Daniela Guidone
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Emanuela Caci
- UOC Genetica Medica, IRCCS Istituto Giannina Gaslini, Genova, Italy
| | - Stefano Castellani
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Massimo Conese
- Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Luis J V Galietta
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy.,Department of Translational Medical Sciences (DISMET), Federico II University of Naples, Naples, Italy
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Abstract
PURPOSE OF REVIEW Diabetic nephropathy, a major microvascular complication of diabetes and the most common cause of end-stage renal disease, is characterized by prominent accumulation of extracellular matrix. The membrane microdomains caveolae, and their integral protein caveolin-1, play critical roles in the regulation of signal transduction. In this review we discuss current knowledge of the contribution of caveolin-1/caveolae to profibrotic signaling and the pathogenesis of diabetic kidney disease, and assess its potential as a therapeutic target. RECENT FINDINGS Caveolin (cav)-1 is key to facilitating profibrotic signal transduction induced by several stimuli known to be pathogenic in diabetic nephropathy, including the most prominent factors hyperglycemia and angiotensin II. Phosphorylation of cav-1 on Y14 is an important regulator of these responses. In vivo studies support a pathogenic role for caveolae in the progression of diabetic nephropathy. Targeting caveolin-1/caveolae would enable inhibition of multiple profibrotic pathways, representing a novel and potentially potent therapeutic option for diabetic nephropathy.
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Affiliation(s)
- Richard Van Krieken
- Department of Medicine, Division of Nephrology, St. Joseph's Hospital, McMaster University, 50 Charlton Ave E, T3311, Hamilton, ON, L8N 4A6, Canada
| | - Joan C Krepinsky
- Department of Medicine, Division of Nephrology, St. Joseph's Hospital, McMaster University, 50 Charlton Ave E, T3311, Hamilton, ON, L8N 4A6, Canada.
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Regulation of glutamate transporter trafficking by Nedd4-2 in a Parkinson's disease model. Cell Death Dis 2017; 8:e2574. [PMID: 28151476 PMCID: PMC5386455 DOI: 10.1038/cddis.2016.454] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 11/05/2016] [Accepted: 12/07/2016] [Indexed: 01/06/2023]
Abstract
Glutamate transporters play a key role in glutamate clearance and protect the central nervous system from glutamate excitotoxicity. Dysfunctional glutamate transporters contribute to the pathogenesis of Parkinson's disease (PD); however, the mechanisms that underlie the regulation of glutamate transporters in PD are still not well characterized. Here we report that Nedd4-2 mediates the ubiquitination of glutamate transporters in 1-methyl-4- phenylpyridinium (MPP+)-treated astrocytes and in the midbrain of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP)-constructed PD model mice. Nedd4-2-mediated ubiquitination induces abnormal glutamate transporter trafficking between the membrane and cytoplasm and consequently decreases the expression and function of glutamate transporters in the membrane. Conversely, Nedd4-2 knockdown decreases glutamate transporter ubiquitination, promotes glutamate uptake and increases glutamate transporter expression in vitro and in vivo. We report for the first time that Nedd4-2 knockdown ameliorates movement disorders in PD mice and increases tyrosine hydroxylase expression in the midbrain and striatum of PD mice; Nedd4-2 knockdown also attenuates astrogliosis and reactive microgliosis in the MPTP model that may be associated with glutamate excitotoxicity. Furthermore, the SGK/PKC pathway is regulated downstream of Nedd4-2 in MPTP-treated mice. These findings indicate that Nedd4-2 may serve as a potential therapeutic target for the treatment of PD.
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Cholesterol influences potassium currents in inner hair cells isolated from guinea pig cochlea. Auris Nasus Larynx 2016; 44:46-51. [PMID: 27210104 DOI: 10.1016/j.anl.2016.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/05/2016] [Accepted: 04/16/2016] [Indexed: 11/21/2022]
Abstract
OBJECTIVE There is a correlation between serum hyperlipidemia and hearing loss. Cholesterol is an integral component of the cell membrane and regulates the activity of ion channels in the lipid bilayer. The aim of this study was to investigate the effects of cholesterol on the potassium currents in IHCs by using the cholesterol-depleting drug, MβCD, and water-soluble cholesterol. METHODS IHCs were acutely isolated from a mature guinea-pig cochlea and potassium currents were recorded. MβCD and water-soluble cholesterol were applied to IHCs under pressure puff pipettes. RESULTS IHCs showed outwardly rectifying currents (IK,f and IK,s) in response to depolarizing voltage pulses, with only a slight inward current (IK,n) when hyperpolarized. In 10mM MβCD solutions, the amplitude of outward K currents reversely decreased; however, fast activation kinetics was preserved. In contrast, in solution of 1mM water-soluble cholesterol, the amplitude of outward K currents reversely increased. At the membrane potential of +110mV, relative conductances were 0.87±0.07 and 1.18±0.11 in MβCD solutions and cholesterol solutions, respectively. CONCLUSION The amplitude of K currents in isolated IHCs was reversely changed by cholesterol-depleting drug and water-soluble cholesterol. These results demonstrated the possibility of the involvement of IHC function in hyperlipidemia-induced inner ear disorders.
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Chapter Five - Ubiquitination of Ion Channels and Transporters. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:161-223. [DOI: 10.1016/bs.pmbts.2016.02.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Abstract
Since the kidney is integral to maintenance of fluid and ion homeostasis, and therefore blood pressure regulation, its proper function is paramount. Circadian fluctuations in blood pressure, renal blood flow, glomerular filtration rate, and sodium and water excretion have been documented for decades, if not longer. Recent studies on the role of circadian clock proteins in the regulation of a variety of renal transport genes suggest that the molecular clock in the kidney controls circadian fluctuations in renal function. The circadian clock appears to be a critical regulator of renal function with important implications for the treatment of renal pathologies, which include chronic kidney disease and hypertension. The development, regulation, and mechanism of the kidney clock are reviewed here.
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Affiliation(s)
- Kristen Solocinski
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, FloridaDepartment of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida
| | - Michelle L Gumz
- Department of Medicine, Division of Nephrology, Hypertension, and Renal Transplantation, University of Florida, Gainesville, FloridaDepartment of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida
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Crespo-Castrillo A, Punzón E, de Pascual R, Maroto M, Padín JF, García-Álvarez I, Nanclares C, Ruiz-Pascual L, Gandía L, Fernández-Mayoralas A, García AG. Novel synthetic sulfoglycolipid IG20 facilitates exocytosis in chromaffin cells through the regulation of sodium channels. J Neurochem 2015; 135:880-96. [DOI: 10.1111/jnc.13357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/03/2015] [Accepted: 08/19/2015] [Indexed: 11/27/2022]
Affiliation(s)
- Andrea Crespo-Castrillo
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Eva Punzón
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Ricardo de Pascual
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Marcos Maroto
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Juan Fernando Padín
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | | | - Carmen Nanclares
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Lucía Ruiz-Pascual
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | - Luis Gandía
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
| | | | - Antonio G. García
- Instituto Teófilo Hernando; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Departamento de Farmacología; Facultad de Medicina; Universidad Autónoma de Madrid; Madrid Spain
- Servicio de Farmacología Clínica; Instituto de Investigación Sanitaria; Hospital Universitario de La Princesa; Madrid Spain
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Riling C, Kamadurai H, Kumar S, O'Leary CE, Wu KP, Manion EE, Ying M, Schulman BA, Oliver PM. Itch WW Domains Inhibit Its E3 Ubiquitin Ligase Activity by Blocking E2-E3 Ligase Trans-thiolation. J Biol Chem 2015; 290:23875-87. [PMID: 26245901 DOI: 10.1074/jbc.m115.649269] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 12/22/2022] Open
Abstract
Nedd4-family E3 ubiquitin ligases regulate an array of biologic processes. Autoinhibition maintains these catalytic ligases in an inactive state through several mechanisms. However, although some Nedd4 family members are activated by binding to Nedd4 family-interacting proteins (Ndfips), how binding activates E3 function remains unclear. Our data reveal how these two regulatory processes are linked functionally. In the absence of Ndfip1, the Nedd4 family member Itch can bind an E2 but cannot accept ubiquitin onto its catalytic cysteine. This is because Itch is autoinhibited by an intramolecular interaction between its HECT (homologous to the E6-AP carboxy terminus domain) and two central WW domains. Ndfip1 binds these WW domains to release the HECT, allowing trans-thiolation and Itch catalytic activity. This molecular switch also regulates the closely related family member WWP2. Importantly, multiple PY motifs are required for Ndfip1 to activate Itch, functionally distinguishing Ndfips from single PY-containing substrates. These data establish a novel mechanism for control of the function of a subfamily of Nedd4 E3 ligases at the level of E2-E3 trans-thiolation.
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Affiliation(s)
- Christopher Riling
- From the Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Hari Kamadurai
- the St. Jude Children's Research Hospital, Memphis, Tennessee 38105
| | | | - Claire E O'Leary
- From the Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Kuen-Phon Wu
- the St. Jude Children's Research Hospital, Memphis, Tennessee 38105
| | | | - Mingjie Ying
- the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104
| | - Brenda A Schulman
- the St. Jude Children's Research Hospital, Memphis, Tennessee 38105, the Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, and
| | - Paula M Oliver
- From the Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, the Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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Abstract
The circadian clock plays an integral role in the regulation of physiological processes, including the regulation of blood pressure. However, deregulation of the clock can lead to pathophysiological states including hypertension. Recent work has implicated the circadian clock genes in the regulation of processes in the heart, kidney, vasculature, and the metabolic organs, which are all critical in the regulation of the blood pressure. The goal of this review is to provide an introduction and general overview into the role of circadian clock genes in the regulation of blood pressure with a focus on their deregulation in the etiology of hypertension. This review will focus on the core circadian clock genes CLOCK, BMAL1, Per, and Cry.
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H-Ras mediates the inhibitory effect of epidermal growth factor on the epithelial Na+ channel. PLoS One 2015; 10:e0116938. [PMID: 25774517 PMCID: PMC4361710 DOI: 10.1371/journal.pone.0116938] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 12/01/2014] [Indexed: 11/21/2022] Open
Abstract
The present study investigates the role of small G-proteins of the Ras family in the epidermal growth factor (EGF)-activated cellular signalling pathway that downregulates activity of the epithelial Na+ channel (ENaC). We found that H-Ras is a key component of this EGF-activated cellular signalling mechanism in M1 mouse collecting duct cells. Expression of a constitutively active H-Ras mutant inhibited the amiloride-sensitive current. The H-Ras-mediated signalling pathway that inhibits activity of ENaC involves c-Raf, and that the inhibitory effect of H-Ras on ENaC is abolished by the MEK1/2 inhibitor, PD98059. The inhibitory effect of H-Ras is not mediated by Nedd4-2, a ubiquitin protein ligase that regulates the abundance of ENaC at the cell surface membrane, or by a negative effect of H-Ras on proteolytic activation of the channel. The inhibitory effects of EGF and H-Ras on ENaC, however, were not observed in cells in which expression of caveolin-1 (Cav-1) had been knocked down by siRNA. These findings suggest that the inhibitory effect of EGF on ENaC-dependent Na+ absorption is mediated via the H-Ras/c-Raf, MEK/ERK signalling pathway, and that Cav-1 is an essential component of this EGF-activated signalling mechanism. Taken together with reports that mice expressing a constitutive mutant of H-Ras develop renal cysts, our findings suggest that H-Ras may play a key role in the regulation of renal ion transport and renal development.
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Goel P, Manning JA, Kumar S. NEDD4-2 (NEDD4L): the ubiquitin ligase for multiple membrane proteins. Gene 2014; 557:1-10. [PMID: 25433090 DOI: 10.1016/j.gene.2014.11.051] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 11/14/2014] [Accepted: 11/21/2014] [Indexed: 12/20/2022]
Abstract
NEDD4-2 (also known as NEDD4L, neural precursor cell expressed developmentally down-regulated 4-like) is a ubiquitin protein ligase of the Nedd4 family which is known to bind and regulate a number of membrane proteins to aid in their internalization and turnover. Several of the NEDD4-2 substrates include ion channels, such as the epithelial and voltage-gated sodium channels. Given the critical function of NEDD4-2 in regulating membrane proteins, this ligase is essential for the maintenance of cellular homeostasis. In this article we review the biology and function of this important ubiquitin-protein ligase and discuss its pathophysiological significance.
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Affiliation(s)
- Pranay Goel
- Centre for Cancer Biology, University of South Australia, Adelaide, SA 5001, Australia; Department of Medicine, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Jantina A Manning
- Centre for Cancer Biology, University of South Australia, Adelaide, SA 5001, Australia
| | - Sharad Kumar
- Centre for Cancer Biology, University of South Australia, Adelaide, SA 5001, Australia; Department of Medicine, The University of Adelaide, Adelaide, SA 5005, Australia.
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Li XC, Gu V, Miguel-Qin E, Zhuo JL. Role of caveolin 1 in AT1a receptor-mediated uptake of angiotensin II in the proximal tubule of the kidney. Am J Physiol Renal Physiol 2014; 307:F949-61. [PMID: 25164083 DOI: 10.1152/ajprenal.00199.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Caveolin 1 (CAV-1) functions not only as a constitutive scaffolding protein of caveolae but also as a vesicular transporter and signaling regulator. In the present study, we tested the hypothesis that CAV-1 knockout (CAV-1 KO) inhibits ANG II type 1 [AT1 (AT1a)] receptor-mediated uptake of ANG II in the proximal tubule and attenuates blood pressure responses in ANG II-induced hypertension. To determine the role of CAV-1 in mediating the uptake of FITC-labeled ANG II, wild-type (WT) mouse proximal convoluted tubule cells were transfected with CAV-1 small interfering (si)RNA for 48 h before AT1 receptor-mediated uptake of FITC-labeled ANG II was studied. CAV-1 siRNA knocked down CAV-1 expression by >90% (P < 0.01) and inhibited FITC-labeled ANG II uptake by >50% (P < 0.01). Moreover, CAV-1 siRNA attenuated ANG II-induced activation of MAPK ERK1/2 and Na(+)/H(+) exchanger 3 expression, respectively (P < 0.01). To determine whether CAV-1 regulates ANG II uptake in the proximal tubule, Alexa 488-labeled ANG II was infused into anesthetized WT and CAV-1 KO mice for 60 min (20 ng/min iv). Imaging analysis revealed that Alexa 488-labeled ANG II uptake was decreased by >50% in CAV-1 KO mice (P < 0.01). Furthermore, Val(5)-ANG II was infused into WT and CAV-1 KO mice for 2 wk (1.5 mg·kg(-1)·day(-1) ip). Basal systolic pressure was higher, whereas blood pressure and renal excretory and signaling responses to ANG II were attenuated, in CAV-1 KO mice (P < 0.01). We concluded that CAV-1 plays an important role in AT1 receptor-mediated uptake of ANG II in the proximal tubule and modulates blood pressure and renal responses to ANG II.
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Division of Nephrology, Department of Medicine, and Cardiovascular Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Victor Gu
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Division of Nephrology, Department of Medicine, and Cardiovascular Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Elise Miguel-Qin
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Division of Nephrology, Department of Medicine, and Cardiovascular Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
| | - Jia L Zhuo
- Laboratory of Receptor and Signal Transduction, Department of Pharmacology and Toxicology, Division of Nephrology, Department of Medicine, and Cardiovascular Renal Research Center, University of Mississippi Medical Center, Jackson, Mississippi
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Caveolins redistribute in uterine epithelial cells during early pregnancy in the rat: An epithelial polarisation strategy? Histochem Cell Biol 2014; 142:555-67. [DOI: 10.1007/s00418-014-1236-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2014] [Indexed: 02/06/2023]
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17
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Zhang Y, Ding Y, Chen YG, Tao Q. NEDD4L regulates convergent extension movements in Xenopus embryos via Disheveled-mediated non-canonical Wnt signaling. Dev Biol 2014; 392:15-25. [PMID: 24833518 DOI: 10.1016/j.ydbio.2014.05.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 04/22/2014] [Accepted: 05/02/2014] [Indexed: 12/19/2022]
Abstract
During the early vertebrate body plan formation, convergent extension (CE) of dorsal mesoderm and neurectoderm is coordinated by the evolutionarily conserved non-canonical Wnt/PCP signaling. Disheveled (Dvl), a key mediator of Wnt/PCP signaling, is essential for the medial-lateral polarity formation in the cells undergoing convergent extension movements. NEDD4L, a highly conserved HECT type E3 ligase, has been reported to regulate the stability of multiple substrates including Dvl2. Here we demonstrate that NEDD4L is required for the cellular polarity formation and convergent extension in the early Xenopus embryos. Depletion of NEDD4L in early Xenopus embryos results in the loss of mediolateral polarity of the convergent-extending mesoderm cells and the shortened body axis, resembling those defects caused by the disruption of non-canonical Wnt signaling. Depletion of xNEDD4L also blocks the elongation of the animal explants in response to endogenous mesoderm inducing signals and partially compromises the expression of Brachyury. Importantly, reducing Dvl2 expression can largely rescue the cellular polarity and convergent extension defects in NEDD4L-depleted embryos and explants. Together with the data that NEDD4L reduces Dvl2 protein expression in the frog embryos, our findings suggest that regulation of Dvl protein levels by NEDD4L is essential for convergent extension during early Xenopus embryogenesis.
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Affiliation(s)
- Yan Zhang
- The State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yi Ding
- The State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China; School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ye-Guang Chen
- The State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| | - Qinghua Tao
- School of Life Sciences, Tsinghua University, Beijing 100084, China.
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18
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Andrukhova O, Slavic S, Smorodchenko A, Zeitz U, Shalhoub V, Lanske B, Pohl EE, Erben RG. FGF23 regulates renal sodium handling and blood pressure. EMBO Mol Med 2014; 6:744-59. [PMID: 24797667 PMCID: PMC4203353 DOI: 10.1002/emmm.201303716] [Citation(s) in RCA: 239] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Fibroblast growth factor-23 (FGF23) is a bone-derived hormone regulating renal phosphate reabsorption and vitamin D synthesis in renal proximal tubules. Here, we show that FGF23 directly regulates the membrane abundance of the Na(+):Cl(-) co-transporter NCC in distal renal tubules by a signaling mechanism involving the FGF receptor/αKlotho complex, extracellular signal-regulated kinase 1/2 (ERK1/2), serum/glucocorticoid-regulated kinase 1 (SGK1), and with-no lysine kinase-4 (WNK4). Renal sodium (Na(+)) reabsorption and distal tubular membrane expression of NCC are reduced in mouse models of Fgf23 and αKlotho deficiency. Conversely, gain of FGF23 function by injection of wild-type mice with recombinant FGF23 or by elevated circulating levels of endogenous Fgf23 in Hyp mice increases distal tubular Na(+) uptake and membrane abundance of NCC, leading to volume expansion, hypertension, and heart hypertrophy in a αKlotho and dietary Na(+)-dependent fashion. The NCC inhibitor chlorothiazide abrogates FGF23-induced volume expansion and heart hypertrophy. Our findings suggest that FGF23 is a key regulator of renal Na(+) reabsorption and plasma volume, and may explain the association of FGF23 with cardiovascular risk in chronic kidney disease patients.
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Affiliation(s)
| | | | | | - Ute Zeitz
- University of Veterinary Medicine Vienna, Vienna, Austria
| | | | - Beate Lanske
- Harvard School of Dental Medicine, Boston, MA, USA
| | - Elena E Pohl
- University of Veterinary Medicine Vienna, Vienna, Austria
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19
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Johansson HM, Newman DR, Sannes PL. Whole-genome analysis of temporal gene expression during early transdifferentiation of human lung alveolar epithelial type 2 cells in vitro. PLoS One 2014; 9:e93413. [PMID: 24690998 PMCID: PMC3972118 DOI: 10.1371/journal.pone.0093413] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 03/05/2014] [Indexed: 12/21/2022] Open
Abstract
It is generally accepted that the surfactant-producing pulmonary alveolar epithelial type II (AT2) cell acts as the progenitor of the type I (AT1) cell, but the regulatory mechanisms involved in this relationship remain the subject of active investigation. While previous studies have established a number of specific markers that are expressed during transdifferentiation from AT2 to AT1 cells, we hypothesized that additional, previously unrecognized, signaling pathways and relevant cellular functions are transcriptionally regulated at early stages of AT2 transition. In this study, a discovery-based gene expression profile analysis was undertaken of freshly isolated human AT2 (hAT2) cells grown on extracellular matrix (ECM) substrata known to either support (type I collagen) or retard (Matrigel) the early transdifferentiation process into hAT1-like cells over the first three days. Cell type-specific expression patterns analyzed by Illumina Human HT-12 BeadChip yielded over 300 genes that were up- or down-regulated. Candidate genes significantly induced or down-regulated during hAT2 transition to hAT1-like cells compared to non-transitioning hAT2 cells were identified. Major functional groups were also recognized, including those of signaling and cytoskeletal proteins as well as genes of unknown function. Expression of established signatures of hAT2 and hAT1 cells, such as surfactant proteins, caveolin-1, and channels and transporters, was confirmed. Selected novel genes further validated by qRT-PCR, protein expression analysis, and/or cellular localization included SPOCK2, PLEKHO1, SPRED1, RAB11FIP1, PTRF/CAVIN-1 and RAP1GAP. These results further demonstrate the utility of genome-wide analysis to identify relevant, novel cell type-specific signatures of early ECM-regulated alveolar epithelial transdifferentiation processes in vitro.
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Affiliation(s)
- Helena Morales Johansson
- Department of Molecular Biomedical Sciences, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Donna R. Newman
- Department of Molecular Biomedical Sciences, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Philip L. Sannes
- Department of Molecular Biomedical Sciences, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
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21
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Richards J, Jeffers LA, All SC, Cheng KY, Gumz ML. Role of Per1 and the mineralocorticoid receptor in the coordinate regulation of αENaC in renal cortical collecting duct cells. Front Physiol 2013; 4:253. [PMID: 24062694 PMCID: PMC3775537 DOI: 10.3389/fphys.2013.00253] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 08/28/2013] [Indexed: 11/22/2022] Open
Abstract
Renal function and blood pressure (BP) exhibit a circadian pattern of variation, but the molecular mechanism underlying this circadian regulation is not fully understood. We have previously shown that the circadian clock protein Per1 positively regulates the basal and aldosterone-mediated expression of the alpha subunit of the renal epithelial sodium channel (αENaC). The mechanism of this regulation has not been determined however. To further elucidate the mechanism of mineralocorticoid receptor (MR) and Per1 action, site-directed mutagenesis, DNA pull-down assays and chromatin immunoprecipitation (ChIP) methods were used to investigate the coordinate regulation of αENaC by Per1 and MR. Mutation of two circadian response E-boxes in the human αENaC promoter abolished both basal and aldosterone-mediated promoter activity. DNA pull down assays demonstrated the interaction of both MR and Per1 with the E-boxes from the αENaC promoter. These observations were corroborated by ChIP experiments showing increased occupancy of MR and Per1 on an E-box of the αENaC promoter in the presence of aldosterone. This is the first report of an aldosterone-mediated increase in Per1 on a target gene promoter. Taken together, these results demonstrate the novel finding that Per1 and MR mediate the aldosterone response of αENaC through DNA/protein interaction in renal collecting duct cells.
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Affiliation(s)
- Jacob Richards
- Department of Medicine, University of Florida Gainesville, FL, USA ; Department of Biochemistry and Molecular Biology, University of Florida Gainesville, FL, USA
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22
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Liu YF, Swart M, Ke Y, Ly K, McDonald FJ. Functional interaction of COMMD3 and COMMD9 with the epithelial sodium channel. Am J Physiol Renal Physiol 2013; 305:F80-9. [PMID: 23637203 DOI: 10.1152/ajprenal.00158.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The epithelial sodium channel (ENaC) plays an important role in controlling Na⁺ homeostasis, extracellular fluid volume, and blood pressure. Copper metabolism Murr1 domain-containing protein 1 (COMMD1) interacts with ENaC and downregulates ENaC. COMMD1 belongs to the COMMD family consisting of COMMD1-10, and all COMMD family members share a C-terminal COMM domain. Here, we report that COMMD2-10 also interacts with ENaC, and COMMD3 and COMMD9 were selected for further study. Amiloride-sensitive current in mammalian epithelia expressing ENaC was significantly reduced by COMMD3 or COMMD9, and ENaC expression at the cell surface was significantly decreased in the presence of COMMD3 or COMMD9. COMMD3 and COMMD9 retained their ability to reduce current when COMMD1 was knocked down. COMMD3 and COMMD9 were widely expressed in kidney and were colocalized with ENaC in renal collecting duct cells. These data suggest that COMMD3 and COMMD9 may be endogenous regulators of ENaC to regulate Na⁺ transport through altering ENaC cell surface expression.
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Affiliation(s)
- Yong Feng Liu
- Department of Physiology, University of Otago, Dunedin, New Zealand
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23
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Richards J, Gumz ML. Mechanism of the circadian clock in physiology. Am J Physiol Regul Integr Comp Physiol 2013; 304:R1053-64. [PMID: 23576606 DOI: 10.1152/ajpregu.00066.2013] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
It has been well established that the circadian clock plays a crucial role in the regulation of almost every physiological process. It also plays a critical role in pathophysiological states including those of obesity and diabetes. Recent evidence has highlighted the potential for targeting the circadian clock as a potential drug target. New studies have also demonstrated the existence of "clock-independent effects" of the circadian proteins, leading to exciting new avenues of research in the circadian clock field in physiology. The goal of this review is to provide an introduction to and overview of the circadian clock in physiology, including mechanisms, targets, and role in disease states. The role of the circadian clocks in the regulation of the cardiovascular system, renal function, metabolism, the endocrine system, immune, and reproductive systems will be discussed.
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Affiliation(s)
- Jacob Richards
- Department of Medicine, University of Florida, Gainesville, FL, USA
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24
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Parton RG, del Pozo MA. Caveolae as plasma membrane sensors, protectors and organizers. Nat Rev Mol Cell Biol 2013; 14:98-112. [PMID: 23340574 DOI: 10.1038/nrm3512] [Citation(s) in RCA: 639] [Impact Index Per Article: 58.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Caveolae are submicroscopic, plasma membrane pits that are abundant in many mammalian cell types. The past few years have seen a quantum leap in our understanding of the formation, dynamics and functions of these enigmatic structures. Caveolae have now emerged as vital plasma membrane sensors that can respond to plasma membrane stresses and remodel the extracellular environment. Caveolae at the plasma membrane can be removed by endocytosis to regulate their surface density or can be disassembled and their structural components degraded. Coat proteins, called cavins, work together with caveolins to regulate the formation of caveolae but also have the potential to dynamically transmit signals that originate in caveolae to various cellular destinations. The importance of caveolae as protective elements in the plasma membrane, and as membrane organizers and sensors, is highlighted by links between caveolae dysfunction and human diseases, including muscular dystrophies and cancer.
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Affiliation(s)
- Robert G Parton
- Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072, Australia.
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25
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Richards J, Greenlee MM, Jeffers LA, Cheng KY, Guo L, Eaton DC, Gumz ML. Inhibition of αENaC expression and ENaC activity following blockade of the circadian clock-regulatory kinases CK1δ/ε. Am J Physiol Renal Physiol 2012; 303:F918-27. [PMID: 22832921 DOI: 10.1152/ajprenal.00678.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Increasing evidence suggests that the circadian clock plays an important role in the control of renal function and blood pressure. We previously showed that the circadian clock protein Period (Per)1, positively regulates the expression of the rate limiting subunit of the renal epithelial sodium channel (αENaC), which contributes to blood pressure regulation. Casein kinases 1δ and 1ε (CK1δ/ε) are critical regulators of clock proteins. CK1δ/ε must phosphorylate the circadian clock protein Per1 in order for the latter to enter the nucleus. We used a commercially available CK1δ/ε inhibitor, PF670462, to test the effect of CK1δ/ε blockade and inhibited Per1 nuclear entry on αENaC in a model of the renal cortical collecting duct (mpkCCD(c14) cells). CK1δ/ε blockade prevented Per1 and Clock from interacting with an E-box from the αENaC promoter. CK1δ/ε inhibition reduced αENaC mRNA levels by <60%. A similar decrease in αENaC mRNA was observed following siRNA-mediated CK1δ/ε knock-down. Inhibition of CK1δ/ε effectively prevented the transcriptional response of αENaC to aldosterone, suggesting an interaction between the circadian clock and aldosterone-mediated regulation of αENaC. CK1δ/ε inhibition significantly reduced αENaC but increased Caveolin-1 membrane protein levels; transepithelial current, a measure of ENaC activity, was decreased. Importantly, single channel analysis in amphibian renal cells demonstrated a dramatic decrease in the number of patches with observable ENaC current following CK1δ/ε inhibition. The present study shows for the first time that CK1δ/ε inhibition and impaired Per1 nuclear entry results in decreased αENaC expression and ENaC activity, providing further support for direct control of ENaC by the circadian clock.
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Affiliation(s)
- Jacob Richards
- 1600 SW Archer Rd., Box 100224, Gainesville, FL 32610, USA.
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26
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Stow LR, Richards J, Cheng KY, Lynch IJ, Jeffers LA, Greenlee MM, Cain BD, Wingo CS, Gumz ML. The circadian protein period 1 contributes to blood pressure control and coordinately regulates renal sodium transport genes. Hypertension 2012; 59:1151-6. [PMID: 22526258 DOI: 10.1161/hypertensionaha.112.190892] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The circadian clock protein period 1 (Per1) contributes to the regulation of expression of the α subunit of the renal epithelial sodium channel at the basal level and in response to the mineralocorticoid hormone aldosterone. The goals of the present study were to define the role of Per1 in the regulation of additional renal sodium handling genes in cortical collecting duct cells and to evaluate blood pressure (BP) in mice lacking functional Per1. To determine whether Per1 regulates additional genes important in renal sodium handling, a candidate gene approach was used. Immortalized collecting duct cells were transfected with a nontarget small interfering RNA or a Per1-specific small interfering RNA. Expression of the genes for α-epithelial sodium channel and Fxyd5, a positive regulator of Na, K-ATPase activity, decreased in response to Per1 knockdown. Conversely, mRNA expression of caveolin 1, Ube2e3, and ET-1, all negative effectors of epithelial sodium channel, was induced after Per1 knockdown. These results led us to evaluate BP in Per1 KO mice. Mice lacking Per1 exhibit significantly reduced BP and elevated renal ET-1 levels compared with wild-type animals. Given the established role of renal ET-1 in epithelial sodium channel inhibition and BP control, elevated renal ET-1 is one possible explanation for the lower BP observed in Per1 KO mice. These data support a role for the circadian clock protein Per1 in the coordinate regulation of genes involved in renal sodium reabsorption. Importantly, the lower BP observed in Per1 KO mice compared with wild-type mice suggests a role for Per1 in BP control as well.
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Affiliation(s)
- Lisa R Stow
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA
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27
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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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28
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Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 273] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
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Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
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29
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Rosenhouse‐Dantsker A, Mehta D, Levitan I. Regulation of Ion Channels by Membrane Lipids. Compr Physiol 2012; 2:31-68. [DOI: 10.1002/cphy.c110001] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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30
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Thomas SV, Kathpalia PP, Rajagopal M, Charlton C, Zhang J, Eaton DC, Helms MN, Pao AC. Epithelial sodium channel regulation by cell surface-associated serum- and glucocorticoid-regulated kinase 1. J Biol Chem 2011; 286:32074-85. [PMID: 21784856 PMCID: PMC3173222 DOI: 10.1074/jbc.m111.278283] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 07/20/2011] [Indexed: 11/06/2022] Open
Abstract
Serum- and glucocorticoid-regulated kinase 1 (sgk1) participates in diverse biological processes, including cell growth, apoptosis, and sodium homeostasis. In the cortical collecting duct of the kidney, sgk1 regulates sodium transport by stimulating the epithelial sodium channel (ENaC). Control of subcellular localization of sgk1 may be an important mechanism for modulating specificity of sgk1 function; however, which subcellular locations are required for sgk1-regulated ENaC activity in collecting duct cells has yet to be established. Using cell surface biotinylation studies, we detected endogenous sgk1 at the apical cell membrane of aldosterone-stimulated mpkCCD(c14) collecting duct cells. The association of sgk1 with the cell membrane was enhanced when ENaC was co-transfected with sgk1 in kidney cells, suggesting that ENaC brings sgk1 to the cell surface. Furthermore, association of endogenous sgk1 with the apical cell membrane of mpkCCD(c14) cells could be modulated by treatments that increase or decrease ENaC expression at the apical membrane; forskolin increased the association of sgk1 with the apical surface, whereas methyl-β-cyclodextrin decreased the association of sgk1 with the apical surface. Single channel recordings of excised inside-out patches from the apical membrane of aldosterone-stimulated A6 collecting duct cells revealed that the open probability of ENaC was sensitive to the sgk1 inhibitor GSK650394, indicating that endogenous sgk1 is functionally active at the apical cell membrane. We propose that the association of sgk1 with the apical cell membrane, where it interacts with ENaC, is a novel means by which sgk1 specifically enhances ENaC activity in aldosterone-stimulated collecting duct cells.
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Affiliation(s)
- Sheela V. Thomas
- From the Department of Medicine, Division of Nephrology, Stanford University, Stanford, California 94305
| | - Paru P. Kathpalia
- From the Department of Medicine, Division of Nephrology, Stanford University, Stanford, California 94305
| | - Madhumitha Rajagopal
- From the Department of Medicine, Division of Nephrology, Stanford University, Stanford, California 94305
| | - Carol Charlton
- From the Department of Medicine, Division of Nephrology, Stanford University, Stanford, California 94305
| | - Jianning Zhang
- the Department of Medicine, Division of Nephrology, University of Texas, Southwestern Medical Center, Dallas, Texas 75390, and
| | - Douglas C. Eaton
- the Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - My N. Helms
- the Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Alan C. Pao
- From the Department of Medicine, Division of Nephrology, Stanford University, Stanford, California 94305
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31
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Lee IH, Song SH, Campbell CR, Kumar S, Cook DI, Dinudom A. Regulation of the epithelial Na+ channel by the RH domain of G protein-coupled receptor kinase, GRK2, and Galphaq/11. J Biol Chem 2011; 286:19259-69. [PMID: 21464134 DOI: 10.1074/jbc.m111.239772] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The G protein-coupled receptor kinase (GRK2) belongs to a family of protein kinases that phosphorylates agonist-activated G protein-coupled receptors, leading to G protein-receptor uncoupling and termination of G protein signaling. GRK2 also contains a regulator of G protein signaling homology (RH) domain, which selectively interacts with α-subunits of the Gq/11 family that are released during G protein-coupled receptor activation. We have previously reported that kinase activity of GRK2 up-regulates activity of the epithelial sodium channel (ENaC) in a Na(+) absorptive epithelium by blocking Nedd4-2-dependent inhibition of ENaC. In the present study, we report that GRK2 also regulates ENaC by a mechanism that does not depend on its kinase activity. We show that a wild-type GRK2 (wtGRK2) and a kinase-dead GRK2 mutant ((K220R)GRK2), but not a GRK2 mutant that lacks the C-terminal RH domain (ΔRH-GRK2) or a GRK2 mutant that cannot interact with Gαq/11/14 ((D110A)GRK2), increase activity of ENaC. GRK2 up-regulates the basal activity of the channel as a consequence of its RH domain binding the α-subunits of Gq/11. We further found that expression of constitutively active Gαq/11 mutants significantly inhibits activity of ENaC. Conversely, co-expression of siRNA against Gαq/11 increases ENaC activity. The effect of Gαq on ENaC activity is not due to change in ENaC membrane expression and is independent of Nedd4-2. These findings reveal a novel mechanism by which GRK2 and Gq/11 α-subunits regulate the activity ENaC.
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Affiliation(s)
- Il-Ha Lee
- Discipline of Physiology, The Bosch Institute, Faculty of Medicine, The University of Sydney, Sydney, NSW 2006, Australia
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32
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Ousingsawat J, Mirza M, Tian Y, Roussa E, Schreiber R, Cook DI, Kunzelmann K. Rotavirus toxin NSP4 induces diarrhea by activation of TMEM16A and inhibition of Na+ absorption. Pflugers Arch 2011; 461:579-89. [PMID: 21399895 DOI: 10.1007/s00424-011-0947-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 02/18/2011] [Accepted: 02/21/2011] [Indexed: 01/05/2023]
Abstract
Rotavirus infection is the most frequent cause for severe diarrhea in infants, killing more than 600,000 every year. The nonstructural protein NSP4 acts as a rotavirus enterotoxin, inducing secretory diarrhea without any structural organ damage. Electrolyte transport was assessed in the colonic epithelium from pups and adult mice using Ussing chamber recordings. Western blots and immunocytochemistry was performed in intestinal tissues from wild-type and TMEM16A knockout mice. Ion channel currents were recorded using patch clamp techniques. We show that the synthetic NSP4(114-135) peptide uses multiple pro-secretory pathways to induce diarrhea, by activating the recently identified Ca2+ -activated Cl- channel TMEM16A, and by inhibiting Na+ absorption by the epithelial Na+ channel ENaC and the Na+ /glucose cotransporter SGLT1. Activation of secretion and inhibition of Na+ absorption by NSP4(114-135), respectively, could be potently suppressed by wheat germ agglutinin which probably competes with NSP4(114-135) for binding to an unknown glycolipid receptor. The present paper gives a clue as to mechanisms of rotavirus-induced diarrhea and suggests wheat germ agglutinin as a simple and effective therapy.
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Affiliation(s)
- Jiraporn Ousingsawat
- Institut für Physiologie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
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Nethe M, Hordijk PL. A model for phospho-caveolin-1-driven turnover of focal adhesions. Cell Adh Migr 2011; 5:59-64. [PMID: 20948305 DOI: 10.4161/cam.5.1.13702] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The regulation of Focal Adhesion (FA) dynamics is a key aspect of cellular motility. FAs concentrate integrins and associated cytoskeletal elements as well as a large number of regulatory proteins, including adapters, kinases and small GTPases of the Rho Family. We have recently shown that activated Rac1 can localize to FAs and can initiate the accumulation of the adapter protein Caveolin1 (Cav1) at FAs. As reported by several groups including ours, this translocation requires Cav1 phosphorylation at Tyr14, presumably by Src. Here we provide additional data regarding this process and briefly review recent literature. Finally, we incorporated the different pieces of available information into a mechanistic model. This model proposes that local Rac1 activation initiates a series of events that involve endosomal traffic of Cav1 and Src, targeting these proteins to or near FAs. Next, within specific membrane domains, Src can mediate the phosphorylation of Cav1 at Tyr 14, which is important for the stable FA localization of Cav1. Finally, dephosphorylation of Cav1 may represent a key step required for internalization, FA turnover and cell motility.
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Affiliation(s)
- Micha Nethe
- Department of Molecular Cell Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
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Levic S, Yamoah EN. Plasticity in membrane cholesterol contributes toward electrical maturation of hearing. J Biol Chem 2010; 286:5768-73. [PMID: 21163952 DOI: 10.1074/jbc.m110.186486] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Advances in refining the "fluid mosaic" model of the plasma membrane have revealed that it is wrought with an ordered lipid composition that undergoes remarkable plasticity during cell development. Despite the evidence that specific signaling proteins and ion channels gravitate toward these lipid microdomains, identification of their functional impact remains a formidable challenge. We report that in contrast to matured auditory hair cells, depletion of membrane cholesterol in developing hair cells produced marked potentiation of voltage-gated K(+) currents (I(Kv)). The enhanced magnitude of I(Kv) in developing hair cells was in keeping with the reduced cholesterol-rich microdomains in matured hair cells. Remarkably, potentiation of the cholesterol-sensitive current was sufficient to abolish spontaneous activity, a functional blueprint of developing and regenerating hair cells. Collectively, these findings provide evidence that developmental plasticity of lipid microdomains and the ensuing changes in K(+) currents are important determinants of one of the hallmarks in the maturation of hearing.
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Affiliation(s)
- Snezana Levic
- Department of Anesthesiology and Pain Medicine, Program in Communication Science, University of California Davis School of Medicine, Davis, California 95618, USA
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35
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Awayda MS, Awayda KL, Pochynyuk O, Bugaj V, Stockand JD, Ortiz RM. Acute cholesterol-induced anti-natriuretic effects: role of epithelial Na+ channel activity, protein levels, and processing. J Biol Chem 2010; 286:1683-95. [PMID: 21041305 DOI: 10.1074/jbc.m110.159194] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The epithelial Na(+) channel (ENaC) is modulated by membrane lipid composition. However, the effect of an in vivo change of membrane composition is unknown. We examined the effect of a 70-day enhanced cholesterol diet (ECD) on ENaC and renal Na(+) handling. Rats were fed a standard chow or one supplemented with 1% cholesterol and 0.5% cholic acid (ECD). ECD animals exhibited marked anti-diuresis and anti-natriuresis (40 and 47%), which peaked at 1-3 weeks. Secondary compensation returned urine output and urinary Na(+) excretion to control levels by week 10. During these initial changes, there were no accompanying effects on systolic blood pressure, serum creatinine, or urinary creatinine excretion, indicating that the these effects of ECD preceded those which modify renal filtration and blood pressure. The effects of ECD on ENaC were evaluated by measuring the relative protein content of α, β, and γ subunits. α and γ blots were further examined for subunit cleavage (a process that activates ENaC). No significant changes were observed in α and β levels throughout the study. However, levels of cleaved γ were elevated, suggesting that ENaC was activated. The changes of γ persisted at week 10 and were accompanied by additional subunit fragments, indicating potential changes of γ-cleaving proteases. Enhanced protease activity, and specifically that which could act on the second identified cleavage site in γ, was verified in a newly developed urinary protease assay. These results predict enhanced ENaC activity, an effect that was confirmed in patch clamp experiments of principal cells of split open collecting ducts, where ENaC open probability was increased by 40% in the ECD group. These data demonstrate a complex series of events and a new regulatory paradigm that is initiated by ECD prior to the onset of elevated blood pressure. These events lead to changes of renal Na(+) handling, which occur in part by effects on extracellular γ-ENaC cleavage.
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Affiliation(s)
- Mouhamed S Awayda
- Department of Physiology and Biophysics, State University of New York, Buffalo, New York 14214, USA.
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36
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Abstract
Many types of ion channel localize to cholesterol and sphingolipid-enriched regions of the plasma membrane known as lipid microdomains or 'rafts'. The precise physiological role of these unique lipid microenvironments remains elusive due largely to difficulties associated with studying these potentially extremely small and dynamic domains. Nevertheless, increasing evidence suggests that membrane rafts regulate channel function in a number of different ways. Raft-enriched lipids such as cholesterol and sphingolipids exert effects on channel activity either through direct protein-lipid interactions or by influencing the physical properties of the bilayer. Rafts also appear to selectively recruit interacting signalling molecules to generate subcellular compartments that may be important for efficient and selective signal transduction. Direct interaction with raft-associated scaffold proteins such as caveolin can also influence channel function by altering gating kinetics or by affecting trafficking and surface expression. Selective association of ion channels with specific lipid microenvironments within the membrane is thus likely to be an important and fundamental regulatory aspect of channel physiology. This brief review highlights some of the existing evidence for raft modulation of channel function.
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Affiliation(s)
- Caroline Dart
- Biosciences Building, School of Biological Sciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
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37
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Butterworth MB. Regulation of the epithelial sodium channel (ENaC) by membrane trafficking. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1166-77. [PMID: 20347969 DOI: 10.1016/j.bbadis.2010.03.010] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 03/15/2010] [Accepted: 03/20/2010] [Indexed: 02/07/2023]
Abstract
The epithelial Na(+) channel (ENaC) is a major regulator of salt and water reabsorption in a number of epithelial tissues. Abnormalities in ENaC function have been directly linked to several human disease states including Liddle syndrome, psuedohypoaldosteronism, and cystic fibrosis and may be implicated in salt-sensitive hypertension. ENaC activity in epithelial cells is regulated both by open probability and channel number. This review focuses on the regulation of ENaC in the cells of the kidney cortical collecting duct by trafficking and recycling. The trafficking of ENaC is discussed in the broader context of epithelial cell vesicle trafficking. Well-characterized pathways and protein interactions elucidated using epithelial model cells are discussed, and the known overlap with ENaC regulation is highlighted. In following the life of ENaC in CCD epithelial cells the apical delivery, internalization, recycling, and destruction of the channel will be discussed. While a number of pathways presented still need to be linked to ENaC regulation and many details of the regulation of ENaC trafficking remain to be elucidated, knowledge of these mechanisms may provide further insights into ENaC activity in normal and disease states.
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Affiliation(s)
- Michael B Butterworth
- Department Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Ke Y, Butt AG, Swart M, Liu YF, McDonald FJ. COMMD1 downregulates the epithelial sodium channel through Nedd4-2. Am J Physiol Renal Physiol 2010; 298:F1445-56. [PMID: 20237237 DOI: 10.1152/ajprenal.00257.2009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The epithelial sodium channel (ENaC) is important for the long-term control of Na(+) homeostasis and blood pressure. Our previous studies demonstrated that Copper Metabolism Murr1 Domain-containing protein 1 (COMMD1; previously known as Murr1), a protein involved in copper metabolism, inhibited amiloride-sensitive current in Xenopus laevis oocytes expressing ENaC (J Biol Chem 279: 5429, 2004). In this study, we report that COMMD1 inhibits amiloride-sensitive current in mammalian epithelial cells expressing ENaC, that the COMM domain of COMMD1 is sufficient for this effect, and that knockdown of COMMD1 increases amiloride-sensitive current. COMMD1 is coexpressed with ENaC in rat kidney medulla cells. COMMD1 increased ubiquitin modification of ENaC and decreased its cell surface expression. COMMD1 abolished insulin-stimulated amiloride-sensitive current and attenuated the stimulation of current by activated serum and glucocorticoid-regulated kinase (SGK1). COMMD1 was found to interact with both SGK1 and Akt1/protein kinase B, and knockdown of COMMD1 enhanced the stimulatory effect of both SGK1 and Akt1 on amiloride-sensitive current. COMMD1's effects were reduced in the presence of ENaC proteins containing PY motif mutations, abolished in the presence of a dominant negative form of Nedd4-2, and knockdown of COMMD1 reduced the inhibitory effect of Nedd4-2 on ENaC, but did not enhance current when Nedd4-2 was knocked down. These data suggest that COMMD1 modulates Na(+) transport in epithelial cells through regulation of ENaC cell surface expression and this effect is likely mediated via Nedd4-2.
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Affiliation(s)
- Ying Ke
- Department of Physiology, University of Otago, Dunedin, New Zealand
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Eaton DC, Malik B, Bao HF, Yu L, Jain L. Regulation of epithelial sodium channel trafficking by ubiquitination. PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY 2010; 7:54-64. [PMID: 20160149 PMCID: PMC3137150 DOI: 10.1513/pats.200909-096js] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 11/02/2009] [Indexed: 01/13/2023]
Abstract
Amiloride-sensitive epithelial sodium (Na(+)) channels (ENaC) play a crucial role in Na(+) transport and fluid reabsorption in the kidney, lung, and colon. The magnitude of ENaC-mediated Na(+) transport in epithelial cells depends on the average open probability of the channels and the number of channels on the apical surface of epithelial cells. The number of channels in the apical membrane, in turn, depends upon a balance between the rate of ENaC insertion and the rate of removal from the apical membrane. ENaC is made up of three homologous subunits, alpha, beta, and gamma. The C-terminal domain of all three subunits is intracellular and contains a proline rich motif (PPxY). Mutations or deletion of this PPxY motif in the beta and gamma subunits prevent the binding of one isoform of a specific ubiquitin ligase, neural precursor cell expressed developmentally down-regulated protein (Nedd4-2) to the channel in vitro and in transfected cell systems, thereby impeding ubiquitin conjugation of the channel subunits. Ubiquitin conjugation would seem to imply that ENaC turnover is determined by the ubiquitin-proteasome system, but when MDCK cells are transfected with ENaC, ubiquitin conjugation apparently leads to lysosomal degradation. However, in untransfected epithelial cells (A6) expressing endogenous ENaC, ENaC appears to be degraded by the ubiquitin-proteasome system. Nonetheless, in both transfected and untransfected cells, the rate of ENaC degradation is apparently controlled by the rate of Nedd4-2-mediated ENaC ubiquitination. Controlling the rate of degradation is apparently important enough to have multiple, redundant pathways to control Nedd4-2 and ENaC ubiquitination.
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Affiliation(s)
- Douglas C Eaton
- Department of Physiology, Whitehead Biomedical Research Building, 615 Micheal Street, Suite 601, Atlanta, GA 30322, USA.
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Hu H, O'Mullane LM, Cummins MM, Campbell CR, Hosoda Y, Poronnik P, Dinudom A, Cook DI. Negative regulation of Ca(2+) influx during P2Y(2) purinergic receptor activation is mediated by Gbetagamma-subunits. Cell Calcium 2010; 47:55-64. [PMID: 20056275 DOI: 10.1016/j.ceca.2009.11.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 11/03/2009] [Accepted: 11/11/2009] [Indexed: 12/01/2022]
Abstract
We have previously reported that P2Y(2) purinoceptors and muscarinic M(3) receptors trigger Ca(2+) responses in HT-29 cells that differ in their timecourse, the Ca(2+) response to P2Y(2) receptor activation being marked by a more rapid decline of intracellular Ca(2+) concentration ([Ca(2+)](i)) after the peak response and that this rapid decline of [Ca(2+)](i) was slowed in cells expressing heterologous beta-adrenergic receptor kinase (betaARK). In the present study, we demonstrate that, during P2Y(2) receptor activation, betaARK expression increases the rate of Gd(3+)-sensitive Mn(2+) influx, a measure of the rate of store-operated Ca(2+) entry from the extracellular space, during P2Y(2) activation and that this effect of betaARK is mimicked by exogenous alpha-subunits of G(q), G(11) and G(i2). The effect of betaARK on the rate of Mn(2+) influx is thus attributable to its ability to scavenge G protein betagamma-subunits released during activation of P2Y(2) receptor. We further find that the effect of betaARK on the rate of Mn(2+) influx during P2Y(2) receptor activation can be overcome by arachidonic acid. In addition, the UTP-induced Mn(2+) influx rate was significantly increased by inhibitors of phospholipase A(2) (PLA(2)) and an siRNA directed against PLA(2)beta, but not by an siRNA directed against PLA(2)alpha or by inhibitors of arachidonic acid metabolism. These findings provide evidence for the existence of a P2Y(2) receptor-activated signalling system that acts in parallel with depletion of intracellular Ca(2+) stores to inhibit Ca(2+) influx across the cell membrane. This signalling process is mediated via Gbetagamma and involves PLA(2)beta and arachidonic acid.
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Affiliation(s)
- Haibi Hu
- The University of Sydney, New South Wales, Australia
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41
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Abstract
A variety of ion channels, including members of all major ion channel families, have been shown to be regulated by changes in the level of membrane cholesterol and partition into cholesterol-rich membrane domains. In general, several types of cholesterol effects have been described. The most common effect is suppression of channel activity by an increase in membrane cholesterol, an effect that was described for several types of inwardly-rectifying K(+) channels, voltage-gated K(+) channels, Ca(+2) sensitive K(+) channels, voltage-gated Na(+) channels, N-type voltage-gated Ca(+2) channels and volume-regulated anion channels. In contrast, several types of ion channels, such as epithelial amiloride-sensitive Na(+) channels and Transient Receptor Potential channels, as well as some of the types of inwardly-rectifying and voltage-gated K(+) channels were shown to be inhibited by cholesterol depletion. Cholesterol was also shown to alter the kinetic properties and current-voltage dependence of several voltage-gated channels. Finally, maintaining membrane cholesterol level is required for coupling ion channels to signalling cascades. In terms of the mechanisms, three general mechanisms have been proposed: (i) specific interactions between cholesterol and the channel protein, (ii) changes in the physical properties of the membrane bilayer and (iii) maintaining the scaffolds for protein-protein interactions. The goal of this review is to describe systematically the role of cholesterol in regulation of the major types of ion channels and to discuss these effects in the context of the models proposed.
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Affiliation(s)
- Irena Levitan
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
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42
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Reed AAC, Loh NY, Terryn S, Lippiat JD, Partridge C, Galvanovskis J, Williams SE, Jouret F, Wu FTF, Courtoy PJ, Nesbit MA, Rorsman P, Devuyst O, Ashcroft FM, Thakker RV. CLC-5 and KIF3B interact to facilitate CLC-5 plasma membrane expression, endocytosis, and microtubular transport: relevance to pathophysiology of Dent's disease. Am J Physiol Renal Physiol 2009; 298:F365-80. [PMID: 19940036 PMCID: PMC2822520 DOI: 10.1152/ajprenal.00038.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal tubular reabsorption is important for extracellular fluid homeostasis and much of this occurs via the receptor-mediated endocytic pathway. This pathway is disrupted in Dent’s disease, an X-linked renal tubular disorder that is characterized by low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, and renal failure. Dent's disease is due to mutations of CLC-5, a chloride/proton antiporter, expressed in endosomes and apical membranes of renal tubules. Loss of CLC-5 function alters receptor-mediated endocytosis and trafficking of megalin and cubilin, although the underlying mechanisms remain to be elucidated. Here, we report that CLC-5 interacts with kinesin family member 3B (KIF3B), a heterotrimeric motor protein that facilitates fast anterograde translocation of membranous organelles. Using yeast two-hybrid, glutathione-S-transferase pull-down and coimmunoprecipitation assays, the COOH terminus of CLC-5 and the coiled-coil and globular domains of KIF3B were shown to interact. This was confirmed in vivo by endogenous coimmunoprecipitation of CLC-5 and KIF3B and codistribution with endosomal markers in mouse kidney fractions. Confocal live cell imaging in kidney cells further demonstrated association of CLC-5 and KIF3B, and transport of CLC-5-containing vesicles along KIF3B microtubules. KIF3B overexpression and underexpression, using siRNA, had reciprocal effects on whole cell chloride current amplitudes, CLC-5 cell surface expression, and endocytosis of albumin and transferrin. Clcn5Y/− mouse kidneys and isolated proximal tubular polarized cells showed increased KIF3B expression, whose effects on albumin endocytosis were dependent on CLC-5 expression. Thus, the CLC-5 and KIF3B interaction is important for CLC-5 plasma membrane expression and for facilitating endocytosis and microtubular transport in the kidney.
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Affiliation(s)
- Anita A C Reed
- Academic Endocrine Unit, Nuffield Department of Medicine, University of Oxford, Oxford Centre for Diabetes, Endocrinology, and Metabolism, Churchill Hospital, Oxford, United Kingdom
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O'Mullane LM, Cook DI, Dinudom A. Purinergic regulation of the epithelial Na+ channel. Clin Exp Pharmacol Physiol 2009; 36:1016-22. [PMID: 19566815 DOI: 10.1111/j.1440-1681.2009.05256.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
1. The epithelial Na(+) channel (ENaC) is a major conductive pathway that transports Na(+) across the apical membrane of the distal nephron, the respiratory tract, the distal colon and the ducts of exocrine glands. The ENaC is regulated by hormonal and humoral factors, including extracellular nucleotides that are available from the epithelial cells themselves. 2. Extracellular nucleotides, via the P2Y2 receptors (P2Y2Rs) at the basolateral and apical membrane of the epithelia, trigger signalling systems that inhibit the activity of the ENaC and activate Ca(2+) -dependent Cl(-) secretion. 3. Recent data from our laboratory suggest that stimulation of the P2Y2Rs at the basolateral membrane inhibits ENaC activity by a signalling mechanism that involves G beta gamma subunits freed from a pertussis toxin (PTX)-sensitive G-protein and phospholipase C (PLC) beta 4. A similar signalling mechanism is also partially responsible for inhibition of the ENaC during activation of apical P2Y2Rs. 4. Stimulation of apical P2Y2Rs also activates an additional signalling mechanism that inhibits the ENaC and involves the activated Galpha subunit of a PTX-insensitive G-protein and activation of an unidentified PLC. The effect of this PTX-insensitive system requires the activity of the basolateral Na(+)/K(+)/2Cl(-) cotransporter.
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Affiliation(s)
- Lauren M O'Mullane
- Discipline of Physiology, The Bosch Institute, Faculty of Medicine, The University of Sydney, Sydney, New South Wales, Australia
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