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McKenna MJ, Renaud JM, Ørtenblad N, Overgaard K. A century of exercise physiology: effects of muscle contraction and exercise on skeletal muscle Na +,K +-ATPase, Na + and K + ions, and on plasma K + concentration-historical developments. Eur J Appl Physiol 2024; 124:681-751. [PMID: 38206444 PMCID: PMC10879387 DOI: 10.1007/s00421-023-05335-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 09/27/2023] [Indexed: 01/12/2024]
Abstract
This historical review traces key discoveries regarding K+ and Na+ ions in skeletal muscle at rest and with exercise, including contents and concentrations, Na+,K+-ATPase (NKA) and exercise effects on plasma [K+] in humans. Following initial measures in 1896 of muscle contents in various species, including humans, electrical stimulation of animal muscle showed K+ loss and gains in Na+, Cl- and H20, then subsequently bidirectional muscle K+ and Na+ fluxes. After NKA discovery in 1957, methods were developed to quantify muscle NKA activity via rates of ATP hydrolysis, Na+/K+ radioisotope fluxes, [3H]-ouabain binding and phosphatase activity. Since then, it became clear that NKA plays a central role in Na+/K+ homeostasis and that NKA content and activity are regulated by muscle contractions and numerous hormones. During intense exercise in humans, muscle intracellular [K+] falls by 21 mM (range - 13 to - 39 mM), interstitial [K+] increases to 12-13 mM, and plasma [K+] rises to 6-8 mM, whilst post-exercise plasma [K+] falls rapidly, reflecting increased muscle NKA activity. Contractions were shown to increase NKA activity in proportion to activation frequency in animal intact muscle preparations. In human muscle, [3H]-ouabain-binding content fully quantifies NKA content, whilst the method mainly detects α2 isoforms in rats. Acute or chronic exercise affects human muscle K+, NKA content, activity, isoforms and phospholemman (FXYD1). Numerous hormones, pharmacological and dietary interventions, altered acid-base or redox states, exercise training and physical inactivity modulate plasma [K+] during exercise. Finally, historical research approaches largely excluded female participants and typically used very small sample sizes.
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Affiliation(s)
- Michael J McKenna
- Institute for Health and Sport, Victoria University, Melbourne, VIC, 8001, Australia.
- College of Physical Education, Southwest University, Chongqing, China.
- College of Sport Science, Zhuhai College of Science and Technology, Zhuhai, China.
| | - Jean-Marc Renaud
- Department of Cellular and Molecular Medicine, Neuromuscular Research Center, University of Ottawa, Ottawa, ON, Canada
| | - Niels Ørtenblad
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
| | - Kristian Overgaard
- Exercise Biology, Department of Public Health, Aarhus University, Aarhus, Denmark
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2
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Barlow IL, Mackay E, Wheater E, Goel A, Lim S, Zimmerman S, Woods I, Prober DA, Rihel J. The zebrafish mutant dreammist implicates sodium homeostasis in sleep regulation. eLife 2023; 12:RP87521. [PMID: 37548652 PMCID: PMC10406431 DOI: 10.7554/elife.87521] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/08/2023] Open
Abstract
Sleep is a nearly universal feature of animal behaviour, yet many of the molecular, genetic, and neuronal substrates that orchestrate sleep/wake transitions lie undiscovered. Employing a viral insertion sleep screen in larval zebrafish, we identified a novel gene, dreammist (dmist), whose loss results in behavioural hyperactivity and reduced sleep at night. The neuronally expressed dmist gene is conserved across vertebrates and encodes a small single-pass transmembrane protein that is structurally similar to the Na+,K+-ATPase regulator, FXYD1/Phospholemman. Disruption of either fxyd1 or atp1a3a, a Na+,K+-ATPase alpha-3 subunit associated with several heritable movement disorders in humans, led to decreased night-time sleep. Since atpa1a3a and dmist mutants have elevated intracellular Na+ levels and non-additive effects on sleep amount at night, we propose that Dmist-dependent enhancement of Na+ pump function modulates neuronal excitability to maintain normal sleep behaviour.
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Affiliation(s)
- Ida L Barlow
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Eirinn Mackay
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Emily Wheater
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Aimee Goel
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Sumi Lim
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
| | - Steve Zimmerman
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | | | - David A Prober
- Division of Biology and Biological Engineering, California Institute of TechnologyPasadenaUnited States
| | - Jason Rihel
- Department of Cell and Developmental Biology, University College LondonLondonUnited Kingdom
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3
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Peluffo RD, Hernández JA. The Na +,K +-ATPase and its stoichiometric ratio: some thermodynamic speculations. Biophys Rev 2023; 15:539-552. [PMID: 37681108 PMCID: PMC10480117 DOI: 10.1007/s12551-023-01082-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 06/18/2023] [Indexed: 09/09/2023] Open
Abstract
Almost seventy years after its discovery, the sodium-potassium adenosine triphosphatase (the sodium pump) located in the cell plasma membrane remains a source of novel mechanistic and physiologic findings. A noteworthy feature of this enzyme/transporter is its robust stoichiometric ratio under physiological conditions: it sequentially counter-transports three sodium ions and two potassium ions against their electrochemical potential gradients per each hydrolyzed ATP molecule. Here we summarize some present knowledge about the sodium pump and its physiological roles, and speculate whether energetic constraints may have played a role in the evolutionary selection of its characteristic stoichiometric ratio.
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Affiliation(s)
- R. Daniel Peluffo
- Group of Biophysical Chemistry, Department of Biological Sciences, CENUR Litoral Norte, Universidad de La República, Rivera 1350, CP: 50000 Salto, Uruguay
| | - Julio A. Hernández
- Biophysics and Systems Biology Section, Department of Cell and Molecular Biology, Facultad de Ciencias, Universidad de La República, Iguá 4225, CP: 11400 Montevideo, Uruguay
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4
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Zhang X, Lee W, Bian JS. Recent Advances in the Study of Na +/K +-ATPase in Neurodegenerative Diseases. Cells 2022; 11:cells11244075. [PMID: 36552839 PMCID: PMC9777075 DOI: 10.3390/cells11244075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 12/11/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Na+/K+-ATPase (NKA), a large transmembrane protein, is expressed in the plasma membrane of most eukaryotic cells. It maintains resting membrane potential, cell volume and secondary transcellular transport of other ions and neurotransmitters. NKA consumes about half of the ATP molecules in the brain, which makes NKA highly sensitive to energy deficiency. Neurodegenerative diseases (NDDs) are a group of diseases characterized by chronic, progressive and irreversible neuronal loss in specific brain areas. The pathogenesis of NDDs is sophisticated, involving protein misfolding and aggregation, mitochondrial dysfunction and oxidative stress. The protective effect of NKA against NDDs has been emerging gradually in the past few decades. Hence, understanding the role of NKA in NDDs is critical for elucidating the underlying pathophysiology of NDDs and identifying new therapeutic targets. The present review focuses on the recent progress involving different aspects of NKA in cellular homeostasis to present in-depth understanding of this unique protein. Moreover, the essential roles of NKA in NDDs are discussed to provide a platform and bright future for the improvement of clinical research in NDDs.
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Affiliation(s)
- Xiaoyan Zhang
- Department of Pharmacology, School of Medicine, Southern University of Science and Technology, Shenzhen 518055, China
| | - Weithye Lee
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117600, Singapore
| | - Jin-Song Bian
- Department of Pharmacology, School of Medicine, Southern University of Science and Technology, Shenzhen 518055, China
- Correspondence:
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5
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FXYD3 Expression Predicts Poor Prognosis in Renal Cell Carcinoma with Immunosuppressive Tumor Microenvironment. Cancers (Basel) 2022; 14:cancers14153596. [PMID: 35892856 PMCID: PMC9330147 DOI: 10.3390/cancers14153596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 07/15/2022] [Accepted: 07/17/2022] [Indexed: 11/17/2022] Open
Abstract
Simple Summary FXYD3 belongs to the protein-coding gene family associated with Na+/K+-ATPase enzymes and chloride ion channels. Recently, the biological role of FXYD3 has been reported in multiple cancers. Nevertheless, the prognostic value of FXYD3 expression has been undiscovered in clear renal cell carcinoma (KIRC). In this study, we assessed the datasets from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) dataset (GSE29609). We found the FXYD3 high KIRC patients had distinct clinical characteristics, including hypoxia and poor overall survival. Furthermore, the algorithms discovered that FXYD3 mRNA levels were associated with tumor purity, multiple types of the tumor infiltrating lymphocytes (TILs) and several genes related to T cell exhaustion. In conclusion, FXYD3 predicts a poor prognosis associated with hypoxia, pro-tumor TILs, and T cell exhaustion in KIRC. Abstract FXYD3 is a protein-coding gene, belonging to the FXYD protein family associated with Na+/K+-ATPase enzymes and chloride ion channels. Accumulating evidence suggests the biological role of FXYD3 in multiple cancers. However, the prognostic value of FXYD3 expression in clear renal cell carcinoma (KIRC) is unclear. Therefore, we evaluated the clinical data with tumor-infiltrating lymphocytes (TILs) and immunoinhibitory gene expression data using The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) dataset (GSE29609). First, the FXYD3 high KIRC patients had distinct clinical characteristics, including age, sex, disease stage, histological grade, and hypoxia-related gene expressions. Next, FXYD3 gene expression was correlated with poor overall survival in both TCGA and GSE29609 cohorts. The ESTIMATE algorithm revealed that higher FXYD3 mRNA levels were associated with increased infiltration of immune cells and tumor purity. Moreover, the FXYD3 high KIRC tissue harbored increased TILs such as B cells, CD8+ T cells, and M1 macrophage, whereas NK cells and neutrophils were decreased. In addition, we showed FXYD3 was co-expressed with several immunoinhibitory genes related to T cell exhaustion such as LGALS9, CTLA4, BTLA, PDCD1, and LAG3. In conclusion, FXYD3 is an unfavorable prognostic biomarker associated with hypoxia, pro-tumor TILs, and T cell exhaustion.
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6
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Na/K-ATPase Ion Transport and Receptor-Mediated Signaling Pathways. J Membr Biol 2021; 254:443-446. [PMID: 34724099 DOI: 10.1007/s00232-021-00207-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2021] [Indexed: 10/19/2022]
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7
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Bubb KJ, Tang O, Gentile C, Moosavi SM, Hansen T, Liu CC, Di Bartolo BA, Figtree GA. FXYD1 Is Protective Against Vascular Dysfunction. Hypertension 2021; 77:2104-2116. [PMID: 33934624 DOI: 10.1161/hypertensionaha.120.16884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Kristen J Bubb
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia (K.J.B.)
| | - Owen Tang
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Royal North Shore Hospital, St Leonards, NSW, Australia (O.T., T.H., C.-C.L., B.A.D.B., G.A.F.)
| | - Carmine Gentile
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,University of Technology Sydney, Ultimo, NSW, Australia (C.G., S.M.M.)
| | - Seyed M Moosavi
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,University of Technology Sydney, Ultimo, NSW, Australia (C.G., S.M.M.)
| | - Thomas Hansen
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Royal North Shore Hospital, St Leonards, NSW, Australia (O.T., T.H., C.-C.L., B.A.D.B., G.A.F.)
| | - Chia-Chi Liu
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Royal North Shore Hospital, St Leonards, NSW, Australia (O.T., T.H., C.-C.L., B.A.D.B., G.A.F.).,Heart Research Institute, Newtown, NSW, Australia (C.-C.L.)
| | - Belinda A Di Bartolo
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Royal North Shore Hospital, St Leonards, NSW, Australia (O.T., T.H., C.-C.L., B.A.D.B., G.A.F.)
| | - Gemma A Figtree
- From the University of Sydney, Kolling Institute of Medical Research, Cardiothoracic and Vascular Health (K.J.B., O.T., C.G., S.M.M., T.H., C.-C.L., B.A.D.B., G.A.F.).,Royal North Shore Hospital, St Leonards, NSW, Australia (O.T., T.H., C.-C.L., B.A.D.B., G.A.F.)
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8
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Newly Discovered Micropeptide Regulators of SERCA Form Oligomers but Bind to the Pump as Monomers. J Mol Biol 2019; 431:4429-4443. [PMID: 31449798 DOI: 10.1016/j.jmb.2019.07.037] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/26/2019] [Accepted: 07/31/2019] [Indexed: 12/22/2022]
Abstract
The recently-discovered single-span transmembrane proteins endoregulin (ELN), dwarf open reading frame (DWORF), myoregulin (MLN), and another-regulin (ALN) are reported to bind to the SERCA calcium pump in a manner similar to that of known regulators of SERCA activity, phospholamban (PLB) and sarcolipin (SLN). To determine how micropeptide assembly into oligomers affects the availability of the micropeptide to bind to SERCA in a regulatory complex, we used co-immunoprecipitation and fluorescence resonance energy transfer (FRET) to quantify micropeptide oligomerization and SERCA-binding. Micropeptides formed avid homo-oligomers with high-order stoichiometry (n > 2 protomers per homo-oligomer), but it was the monomeric form of all micropeptides that interacted with SERCA. In view of these two alternative binding interactions, we evaluated the possibility that oligomerization occurs at the expense of SERCA-binding. However, even the most avidly oligomeric micropeptide species still showed robust FRET with SERCA, and there was a surprising positive correlation between oligomerization affinity and SERCA-binding. This comparison of micropeptide family members suggests that the same structural determinants that support oligomerization are also important for binding to SERCA. Moreover, the unique oligomerization/SERCA-binding profile of DWORF is in harmony with its distinct role as a PLB-competing SERCA activator, in contrast to the inhibitory function of the other SERCA-binding micropeptides.
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9
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Wyckelsma VL, Perry BD, Bangsbo J, McKenna MJ. Inactivity and exercise training differentially regulate abundance of Na +-K +-ATPase in human skeletal muscle. J Appl Physiol (1985) 2019; 127:905-920. [PMID: 31369327 DOI: 10.1152/japplphysiol.01076.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Physical inactivity is a global health risk that can be addressed through application of exercise training suitable for an individual's health and age. People's willingness to participate in physical activity is often limited by an initially poor physical capability and early onset of fatigue. One factor associated with muscle fatigue during intense contractions is an inexcitability of skeletal muscle cells, reflecting impaired transmembrane Na+/K+ exchange and membrane depolarization, which are regulated via the transmembranous protein Na+-K+-ATPase (NKA). This short review focuses on the plasticity of NKA in skeletal muscle in humans after periods of altered usage, exploring NKA upregulation with exercise training and downregulation with physical inactivity. In human skeletal muscle, the NKA content quantified by [3H]ouabain binding site content shows robust, yet tightly constrained, upregulation of 8-22% with physical training, across a broad range of exercise training types. Muscle NKA content in humans undergoes extensive downregulation with injury that involves substantial muscular inactivity. Surprisingly, however, no reduction in NKA content was found in the single study that investigated short-term disuse. Despite clear findings that exercise training and injury modulate NKA content, the adaptability of the individual NKA isoforms in muscle (α1-3 and β1-3) and of the accessory and regulatory protein FXYD1 are surprisingly inconsistent across studies, for exercise training as well as for injury/disuse. Potential reasons for this are explored. Finally, we provide suggestions for future studies to provide greater understanding of NKA regulation during exercise training and inactivity in humans.
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Affiliation(s)
- V L Wyckelsma
- Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia
| | - B D Perry
- Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia.,School of Science and Health, Western Sydney University, Penrith, New South Wales, Australia
| | - J Bangsbo
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark
| | - M J McKenna
- Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia
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10
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Missense variants in ATP1A3 and FXYD gene family are associated with childhood-onset schizophrenia. Mol Psychiatry 2018; 25:821-830. [PMID: 29895895 PMCID: PMC6291354 DOI: 10.1038/s41380-018-0103-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 05/07/2018] [Accepted: 05/14/2018] [Indexed: 11/09/2022]
Abstract
Childhood-onset schizophrenia (COS) is a rare and severe form of schizophrenia defined as onset before age of 13. Here we report on two unrelated cases diagnosed with both COS and alternating hemiplegia of childhood (AHC), and for whom two distinct pathogenic de novo variants were identified in the ATP1A3 gene. ATP1A3 encodes the α-subunit of a neuron-specific ATP-dependent transmembrane sodium-potassium pump. Using whole exome sequencing data derived from a cohort of 17 unrelated COS cases, we also examined ATP1A3 and all of its interactors known to be expressed in the brain to establish if variants could be identified. This led to the identification of a third case with a possibly damaging missense mutation in ATP1A3 and three others cases with predicted pathogenic missense variants in the FXYD gene family (FXYD1, FXYD6, and FXYD6-FXYD2 readthrough). FXYD genes encode proteins that modulate the ATP-dependant pump function. This report is the first to identify variants in the same pathway for COS. Our COS study illustrates the interest of stratifying a complex condition according to the age of onset for the identification of deleterious variants. Whereas ATP1A3 is a replicated gene in rare neuropediatric diseases, this gene has previously been linked with COS in only one case report. The association with rare variants in FXYD gene family is novel and highlights the interest of exploring these genes in COS as well as in pediatric neurodevelopmental disorders.
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Na +/K +-ATPase response to salinity change and its correlation with FXYD11 expression in Anguilla marmorata. J Comp Physiol B 2017; 187:973-984. [PMID: 28280923 DOI: 10.1007/s00360-017-1059-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 01/07/2017] [Accepted: 01/18/2017] [Indexed: 10/24/2022]
Abstract
The Na+/K+-ATPase (NKA) is a primary electrogenic protein that promotes ion transport in teleosts. FXYD11 is a putative regulatory subunit of the NKA pump. The regulation of Na +/K + -ATPase and FXYD11 is of critical importance for osmotic homeostasis. To investigate the changes of the two genes under different salinity environments, we first identified NKA (AmNKAα1) and FXYD11 (AmFXYD11) in Anguilla marmorata, and then evaluated the mRNA levels of NKA and FXYD11 as well as the activity of NKA in the gill and kidney at different timepoints (0, 1, 3, 6, 12, 24, 48, 72, 96, and 360 h) under three salinity conditions-0‰ (fresh water: FW), 10‰ (brackish water: BW), and 25‰ (seawater: SW). In the gill, the mRNA levels of AmNKAα1 and AmFXYD11 and the enzyme activity of AmNKAα1 were higher in BW and SW than in FW; the protein abundance was positively correlated with the specific activity of NKA in BW/SW. However, in the kidney, the mRNA level of AmNKAα1 in the BW group was higher than that in the FW group. In addition, AmFXYD mRNA levels in both BW and SW groups were significantly lower than that in the FW control group. These results suggested that AmFXYD11 was tissue specific in response to different salinity environment. Our results clearly demonstrated the important roles of AmNKAα1 and AmFXYD11 in osmotic homeostasis of juvenile A. marmorata under saline environment.
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12
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Hu P, Li S, Zhong Y, Mu X, Gui L, Zhang J. Identification of fxyd genes from the spotted scat (Scatophagus argus): molecular cloning, tissue-specific expression, and response to acute hyposaline stress. Comp Biochem Physiol B Biochem Mol Biol 2014; 174:15-22. [PMID: 24878493 DOI: 10.1016/j.cbpb.2014.05.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/17/2014] [Accepted: 05/20/2014] [Indexed: 11/24/2022]
Abstract
By interacting with Na(+), K(+)-ATPase (NKA), the FXYD domain-containing ion transport regulator (FXYD) is involved in teleost osmoregulation, but knowledge of FXYD in marine fish is limited. In the present study, fxyd11 and fxyd12 were identified from the spotted scat (Scatophagus argus), and the two members of the FXYD protein family were expressed in a tissue-specific manner. Fxyd11 mRNA was predominantly expressed in gills, whereas fxyd12 mRNA was mainly distributed in kidneys and intestines. Acute hyposaline stress altered the activity of NKA and the expression of fxyd11 and fxyd12 in gills, kidneys, and intestines. Branchial fxyd11 mRNA expression remained at a low level during freshwater acclimation, whereas NKA activity increased, showing a negative correlation that differed from previous reports. Similarly, renal expression of fxyd11 and fxyd12 mRNA was negatively correlated with NKA activity. Unlike in gills and kidneys, intestinal NKA activity and mRNA expression of fxyd11 and fxyd12 were comparably suppressed. Taken together, the salinity-dependent expression of fxyd11 and fxyd12, and correlation with NKA activity suggested that both fxyd11 and fxyd12 were involved in the response to acute hyposaline challenge in the spotted scat.
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Affiliation(s)
- Pan Hu
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Siqi Li
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Yong Zhong
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Xingjiang Mu
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Lang Gui
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China
| | - Junbin Zhang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Ministry of Education, College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China.
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13
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Li Y, Zhang X, Xu S, Ge J, Liu J, Li L, Fang G, Meng Y, Zhang H, Sun X. Expression and clinical significance of FXYD3 in endometrial cancer. Oncol Lett 2014; 8:517-522. [PMID: 25013464 PMCID: PMC4081380 DOI: 10.3892/ol.2014.2170] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 04/10/2014] [Indexed: 11/23/2022] Open
Abstract
FXYD3 expression is upregulated in numerous cancer cell types. The present study compared the FXDY3 expression in normal endometrium, premalignant lesion and endometrial cancer tissue samples, and investigated the correlation between FXDY3 expression and clinicopathological features. FXYD3 expression was analyzed by streptavidin-peroxidase immunohistochemistry in 21 normal endometrial tissue samples, 18 atypical endometrial hyperplasia samples and 50 tissues obtained from patients diagnosed with endometrial cancer. The percentage of FXYD3-positive cell expression in the normal endometrium, atypical hyperplasia and endometrial cancer tissues samples was 0, 22, and 26%, respectively. The differences between the atypical hyperplasia and endometrial cancer groups were statistically significant when compared with the normal group (P=0.007 and P=0.037, respectively). There was no significant difference between the atypical hyperplasia and endometrial cancer groups. The percentage of FXYD3-positive cells correlated with the fertility frequency (P<0.05). In conclusion, FXYD3 is a potential biomarker for endometrial cancer, and its upregulation may be an early event in endometrial carcinoma progression. In addition, FXYD3 expression in endometrial carcinoma correlates with fertility frequency.
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Affiliation(s)
- Yifei Li
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Xia Zhang
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Shuwen Xu
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Jing Ge
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Jing Liu
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Lin Li
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Guiying Fang
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Yali Meng
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Hongzhen Zhang
- Department of Obstetrics and Gynecology, First Hospital of Hebei Medical University, Shijiazhuang, Hebei, P.R. China
| | - Xiaofeng Sun
- Department of Oncology, Institute of Clinical and Experimental Medicine, Country Council of Östergötland, University of Linköping, Linköping 58185, Sweden
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14
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Changes in the Distribution of the α 3 Na(+)/K(+) ATPase Subunit in Heterozygous Lurcher Purkinje Cells as a Genetic Model of Chronic Depolarization during Development. Int J Cell Biol 2014; 2014:152645. [PMID: 24719618 PMCID: PMC3955620 DOI: 10.1155/2014/152645] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/28/2013] [Accepted: 01/13/2014] [Indexed: 11/30/2022] Open
Abstract
A common assumption of excitotoxic mechanisms in the nervous system is that the ionic imbalance resulting from overstimulation of glutamate receptors and increased Na+ and Ca++ influx overwhelms cellular energy metabolic systems leading to cell death. The goal of this study was to examine how a chronic Na+ channel leak current in developing Purkinje cells in the heterozygous Lurcher mutant (+/Lc) affects the expression and distribution of the α3 subunit of the Na+/K+ ATPase pump, a key component of the homeostasis system that maintains ionic equilibrium in neurons. The expression pattern of the catalytic α3 Na+/K+ ATPase subunit was analyzed by immunohistochemistry, histochemistry, and Western Blots in wild type (WT) and +/Lc cerebella at postnatal days P10, P15, and P25 to determine if there are changes in the distribution of active Na+/K+ ATPase subunits in degenerating Purkinje cells. The results suggest that the expression of the catalytic α3 subunit is altered in chronically depolarized +/Lc Purkinje cells, although the density of active Na+/K+ ATPase pumps is not significantly altered compared with WT in the cerebellar cortex at P15, and then declines from P15 to P25 in the +/Lc cerebellum as the +/Lc Purkinje cells degenerate.
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15
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Cirri E, Kirchner C, Becker S, Katz A, Karlish SJ, Apell HJ. Surface charges of the membrane crucially affect regulation of Na,K-ATPase by phospholemman (FXYD1). J Membr Biol 2013; 246:967-79. [PMID: 24105627 DOI: 10.1007/s00232-013-9600-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/24/2013] [Indexed: 01/02/2023]
Abstract
The human α1/His10-β1 isoform of Na,K-ATPase has been reconstituted as a complex with and without FXYD1 into proteoliposomes of various lipid compositions in order to study the effect of the regulatory subunit on the half-saturating Na⁺ concentration (K(½)) of Na⁺ ions for activation of the ion pump. It has been shown that the fraction of negatively charged lipid in the bilayer crucially affects the regulatory properties. At low concentrations of the negatively charged lipid DOPS (<10 %), FXYD1 increases K(½) of Na⁺ ions for activation of the ion pump. Phosphorylation of FXYD1 by protein kinase A at Ser68 abrogates this effect. Conversely, for proteoliposomes made with high concentrations of DOPS (>10 %), little or no effect of FXYD1 on the K(½) of Na⁺ ions is observed. Depending on ionic strength and lipid composition of the proteoliposomes, FXYD1 can alter the K(½) of Na⁺ ions by up to twofold. We propose possible molecular mechanisms to explain the regulatory effects of FXYD1 and the influence of charged lipid and protein phosphorylation. In particular, the positively charged C-terminal helix of FXYD1 appears to be highly mobile and may interact with the cytoplasmic N domain of the α-subunit, the interaction being strongly affected by phosphorylation at Ser68 and the surface charge of the membrane.
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Affiliation(s)
- Erica Cirri
- Department of Biology and Graduate School of Chemical Biology, University of Konstanz, 78464, Constance, Germany
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16
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Henry SP, Liang S, Akdemir KC, de Crombrugghe B. The postnatal role of Sox9 in cartilage. J Bone Miner Res 2012; 27:2511-25. [PMID: 22777888 PMCID: PMC3502666 DOI: 10.1002/jbmr.1696] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 06/05/2012] [Accepted: 06/22/2012] [Indexed: 11/09/2022]
Abstract
Sox9 is an essential transcription factor for the differentiation of the chondrocytic lineage during embryonic development. To test whether Sox9 continues to play a critical role in cartilaginous tissues in the adult mice, we used an inducible, genetic strategy to disrupt the Sox9 gene postnatally in these tissues. The postnatal inactivation of Sox9 led to stunted growth characterized by decreased proliferation, increased cell death, and dedifferentiation of growth plate chondrocytes. Upon postnatal Sox9 inactivation in the articular cartilage, the sulfated proteoglycan and aggrecan content of the uncalcified cartilage were rapidly depleted and the degradation of aggrecan was accompanied by higher ADAMTS5 immunostaining and increased detection of the aggrecan neoepitope, NITEGE. In spite of the severe loss of Collagen 2a1 mRNA, the Collagen II protein persisted in the articular cartilage, and no histopathological signs of osteoarthritis were observed. The homeostasis of the intervertebral disk (IVD) was dramatically altered upon Sox9 depletion, resulting in disk compression and subsequent degeneration. Inactivation of Sox9 in the IVD markedly reduced the expression of several genes encoding extracellular matrix proteins, as well as some of the enzymes responsible for their posttranslational modification. Furthermore, the loss of Sox9 in the IVD decreased the expression of cytokines, cell-surface receptors, and ion channels, suggesting that Sox9 coordinates a large genetic program that is instrumental for the proper homeostasis of the cells contained in the IVD postnatally. Our results indicate that Sox9 has an essential role in the physiological control of cartilaginous tissues in adult mice. © 2012 American Society for Bone and Mineral Research.
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Affiliation(s)
- Stephen P Henry
- Department of Genetics, The University of Texas M.D. Anderson Cancer Center; Houston, TX, USA.
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17
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Tang CH, Lai DY, Lee TH. Effects of salinity acclimation on Na(+)/K(+)-ATPase responses and FXYD11 expression in the gills and kidneys of the Japanese eel (Anguilla japonica). Comp Biochem Physiol A Mol Integr Physiol 2012; 163:302-10. [PMID: 22885345 DOI: 10.1016/j.cbpa.2012.07.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/25/2012] [Accepted: 07/30/2012] [Indexed: 11/16/2022]
Abstract
Na(+)/K(+)-ATPase (NKA) is a primary active pump provides the driving force for ion-transporting systems in the osmoregulatory tissues of teleosts. Therefore, modulation of NKA expression or activity and its regulatory subunit, FXYD protein, is essential for teleosts in salinity adaptation. To understand the mechanisms for modulation of NKA in catadromous fishes, NKA expression and activity, cloning and mRNA expression of FXYD11 (AjFXYD11) were examined in Japanese eel (Anguilla japonica) exposed to fresh water (FW) and seawater (SW; 35‰). Expression and activity of NKA as well as mRNA expression of AjFXYD11 in gills were elevated in SW eel compared to FW eel. Conversely, NKA responses in eel kidneys were higher in FW group than SW group, whereas no significant difference was found in renal AjFXYD11 expression between the two groups. Comparison of NKA activity and AjFXYD11 expression between two osmoregulatory tissues suggested that AjFXYD11 plays a specific, functional role in gills. However, since cortisol plays an important role for regulation of ion transport in teleost SW acclimation and gill AjFXYD11 expression was elevated in SW eel, the organ culture approach was used to study the effect of cortisol on gill AjFXYD11 mRNA expression. Our results revealed that cortisol treatment increased the levels of gill AjFXYD11 transcripts. This finding suggested that cortisol could be involved in the regulation of NKA by altering AjFXYD11 expression during the process of SW acclimation in A. japonica. Taken together, the differential expression of branchial and renal NKA and AjFXYD11 implicated their roles in the osmotic homeostasis of Japanese eel exposed to environments of different salinities.
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Affiliation(s)
- Cheng-Hao Tang
- Institute of Marine Biotechnology, National Dong Hwa University, Pingtung 944, Taiwan
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18
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Chibalin AV, Heiny JA, Benziane B, Prokofiev AV, Vasiliev AV, Kravtsova VV, Krivoi II. Chronic nicotine modifies skeletal muscle Na,K-ATPase activity through its interaction with the nicotinic acetylcholine receptor and phospholemman. PLoS One 2012; 7:e33719. [PMID: 22442718 PMCID: PMC3307752 DOI: 10.1371/journal.pone.0033719] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 02/15/2012] [Indexed: 11/23/2022] Open
Abstract
Our previous finding that the muscle nicotinic acetylcholine receptor (nAChR) and the Na,K-ATPase interact as a regulatory complex to modulate Na,K-ATPase activity suggested that chronic, circulating nicotine may alter this interaction, with long-term changes in the membrane potential. To test this hypothesis, we chronically exposed rats to nicotine delivered orally for 21–31 days. Chronic nicotine produced a steady membrane depolarization of ∼3 mV in the diaphragm muscle, which resulted from a net change in electrogenic transport by the Na,K-ATPase α2 and α1 isoforms. Electrogenic transport by the α2 isoform increased (+1.8 mV) while the activity of the α1 isoform decreased (−4.4 mV). Protein expression of Na,K-ATPase α1 or α2 isoforms and the nAChR did not change; however, the content of α2 subunit in the plasma membrane decreased by 25%, indicating that its stimulated electrogenic transport is due to an increase in specific activity. The physical association between the nAChR, the Na,K-ATPase α1 or α2 subunits, and the regulatory subunit of the Na,K-ATPase, phospholemman (PLM), measured by co-immuno precipitation, was stable and unchanged. Chronic nicotine treatment activated PKCα/β2 and PKCδ and was accompanied by parallel increases in PLM phosphorylation at Ser63 and Ser68. Collectively, these results demonstrate that nicotine at chronic doses, acting through the nAChR-Na,K-ATPase complex, is able to modulate Na,K-ATPase activity in an isoform-specific manner and that the regulatory range includes both stimulation and inhibition of enzyme activity. Cholinergic modulation of Na,K-ATPase activity is achieved, in part, through activation of PKC and phosphorylation of PLM.
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Affiliation(s)
- Alexander V. Chibalin
- Department of Molecular Medicine and Surgery, Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
- * E-mail: (AC); (IIK)
| | - Judith A. Heiny
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio, United States of America
| | - Boubacar Benziane
- Department of Molecular Medicine and Surgery, Integrative Physiology, Karolinska Institutet, Stockholm, Sweden
| | - Alexander V. Prokofiev
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
| | - Alexander V. Vasiliev
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
| | - Violetta V. Kravtsova
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
| | - Igor I. Krivoi
- Department of General Physiology, St. Petersburg State University, St. Petersburg, Russia
- * E-mail: (AC); (IIK)
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19
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New Insights into the Regulation of Na+,K+-ATPase by Ouabain. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 294:99-132. [DOI: 10.1016/b978-0-12-394305-7.00002-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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20
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Kimura T, Han W, Pagel P, Nairn AC, Caplan MJ. Protein phosphatase 2A interacts with the Na,K-ATPase and modulates its trafficking by inhibition of its association with arrestin. PLoS One 2011; 6:e29269. [PMID: 22242112 PMCID: PMC3248462 DOI: 10.1371/journal.pone.0029269] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 11/23/2011] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The P-type ATPase family constitutes a collection of ion pumps that form phosphorylated intermediates during ion transport. One of the best known members of this family is the Na⁺,K⁺-ATPase. The catalytic subunit of the Na⁺,K⁺-ATPase includes several functional domains that determine its enzymatic and trafficking properties. METHODOLOGY/PRINCIPAL FINDINGS Using the yeast two-hybrid system we found that protein phosphatase 2A (PP2A) catalytic C-subunit is a specific Na⁺,K⁺-ATPase interacting protein. PP-2A C-subunit interacted with the Na⁺,K⁺-ATPase, but not with the homologous sequences of the H⁺,K⁺-ATPase. We confirmed that the Na⁺,K⁺-ATPase interacts with a complex of A- and C-subunits in native rat kidney. Arrestins and G-protein coupled receptor kinases (GRKs) are important regulators of G-protein coupled receptor (GPCR) signaling, and they also regulate Na⁺,K⁺-ATPase trafficking through direct association. PP2A inhibits association between the Na⁺,K⁺-ATPase and arrestin, and diminishes the effect of arrestin on Na⁺,K⁺-ATPase trafficking. GRK phosphorylates the Na⁺,K⁺-ATPase and PP2A can at least partially reverse this phosphorylation. CONCLUSIONS/SIGNIFICANCE Taken together, these data demonstrate that the sodium pump belongs to a growing list of ion transport proteins that are regulated through direct interactions with the catalytic subunit of a protein phosphatase.
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Affiliation(s)
- Toru Kimura
- Department of Pharmacology and Toxicology, Kyorin University School of Medicine, Mitaka, Tokyo, Japan
- Departments of Cellular & Molecular Physiology and
| | - WonSun Han
- Departments of Cellular & Molecular Physiology and
| | | | - Angus C. Nairn
- Psychiatry, Yale University School of Medicine New Haven, Connecticut, United States of America
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21
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Morth JP, Pedersen BP, Buch-Pedersen MJ, Andersen JP, Vilsen B, Palmgren MG, Nissen P. A structural overview of the plasma membrane Na+,K+-ATPase and H+-ATPase ion pumps. Nat Rev Mol Cell Biol 2011; 12:60-70. [PMID: 21179061 DOI: 10.1038/nrm3031] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasma membrane ATPases are primary active transporters of cations that maintain steep concentration gradients. The ion gradients and membrane potentials derived from them form the basis for a range of essential cellular processes, in particular Na(+)-dependent and proton-dependent secondary transport systems that are responsible for uptake and extrusion of metabolites and other ions. The ion gradients are also both directly and indirectly used to control pH homeostasis and to regulate cell volume. The plasma membrane H(+)-ATPase maintains a proton gradient in plants and fungi and the Na(+),K(+)-ATPase maintains a Na(+) and K(+) gradient in animal cells. Structural information provides insight into the function of these two distinct but related P-type pumps.
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Affiliation(s)
- J Preben Morth
- Danish National Research Foundation, Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Denmark
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22
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Abstract
During acute lung injury edema accumulates in the alveolar space, resulting in hypoxemia due to intrapulmonary shunt. The alveolar Na,K-ATPase, by effecting active Na(+) transport, is essential for removing edema from the alveolar spaces. However, during hypoxia it is endocytosed and degraded, which results in decreased Na,K-ATPase function and impaired lung edema clearance. Na,K-ATPase endocytosis and degradation require the phosphorylation and subsequent ubiquitination of the Na,K-ATPase. These events are the results of cross-talk between post-translational modifications, and how ubiquitination of a specific protein can result from injurious extracellular stimuli. Here, we review current knowledge on the regulation of Na,K-ATPase activity during lung injury, focusing on the role of Na,K-ATPase ubiquitination during hypoxia. A better understanding of these signaling pathways can be of relevance for the design of novel treatments to ameliorate the deleterious effects of acute lung injury.
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23
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George AJ, Gordon L, Beissbarth T, Koukoulas I, Holsinger RMD, Perreau V, Cappai R, Tan SS, Masters CL, Scott HS, Li QX. A serial analysis of gene expression profile of the Alzheimer's disease Tg2576 mouse model. Neurotox Res 2010; 17:360-79. [PMID: 19760337 DOI: 10.1007/s12640-009-9112-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 06/22/2009] [Accepted: 08/31/2009] [Indexed: 10/20/2022]
Abstract
Serial analysis of gene expression (SAGE), a technique that allows for the simultaneous detection of expression levels of the entire genome without a priori knowledge of gene sequences, was used to examine the transcriptional expression pattern of the Tg2576 mouse model of Alzheimer's disease (AD). Pairwise comparison between the Tg2576 and nontransgenic SAGE libraries identified a number of differentially expressed genes in the Tg2576 SAGE library, some of which were not previously revealed by the microarray studies. Real-time PCR was used to validate a panel of genes selected from the SAGE analysis in the Tg2576 mouse brain, as well as the hippocampus and temporal cortex of sporadic AD and normal age-matched controls. NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 5 (NDUFA5) and FXYD domain-containing ion transport regulator 6 (FXYD6) were found to be significantly decreased in the Tg2576 mouse brain and AD hippocampus. PTEN-induced putative kinase 1 (PINK1), phosphatidylethanolamine binding protein (PEBP), crystalline mu (CRYM), and neurogranin (NRGN) were significantly decreased in AD tissues. The gene ontologies represented in the Tg2576 data were statistically analyzed and demonstrated a significant under-representation of genes involved with G-protein-coupled receptor signaling and odorant binding, while genes significantly over-represented were focused on cellular communication and cellular physiological processes. The novel approach of profiling the Tg2576 mouse brain using SAGE has identified different genes that could subsequently be examined for their potential as peripheral diagnostic and prognostic markers for Alzheimer's disease.
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Affiliation(s)
- Amee J George
- Department of Pathology, The University of Melbourne and The Mental Health Research Institute of Victoria, Parkville, VIC 3052, Australia
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24
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Floyd RV, Wray S, Martín-Vasallo P, Mobasheri A. Differential cellular expression of FXYD1 (phospholemman) and FXYD2 (gamma subunit of Na, K-ATPase) in normal human tissues: a study using high density human tissue microarrays. Ann Anat 2009; 192:7-16. [PMID: 19879113 DOI: 10.1016/j.aanat.2009.09.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Revised: 08/03/2009] [Accepted: 09/15/2009] [Indexed: 01/02/2023]
Abstract
FXYD proteins have been proposed to function as regulators of Na, K-ATPase function by lowering affinities of the system for potassium and sodium. However, their distribution in normal human tissues has not been studied. We have therefore used immunohistochemistry and semi-quantitative histomorphometric analysis to determine the relative expression at the protein level and distribution of FXYD1 (phospholemman) and FXYD2 (gamma subunit of Na, K-ATPase) in human Tissue MicroArrays (TMAs). Expression of FXYD1 was abundant in heart, kidney, placenta, skeletal muscle, gastric and anal mucosa, small intestine and colon. Lower FXYD1 expression was detected in uterine, intestinal and bladder smooth muscle, choroid plexus, liver, gallbladder, spleen, breast, prostate and epididymis. The tissue distribution of FXYD2 was less extensive compared to that of FXYD1. There was an abundant expression in kidney and choroid plexus and moderate expression in placenta, amniotic membranes, breast epithelium, salivary glands, pancreas and uterine endometrium. Weaker FXYD2 expression was detected in the adrenal medulla, liver, gallbladder, bladder and pancreas. The common denominator in the distribution of FXYD1 and FXYD2 was expression in highly active transport epithelia of the kidney, choroid plexus, placenta and salivary glands. This study reveals, in human tissues, the specific expression of FXYD proteins, which may associate with Na, K-ATPase in selected cell types and modulate its catalytic properties.
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Affiliation(s)
- Rachel V Floyd
- Physiological Laboratory, Department of Physiology, School of Biomedical Sciences, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK
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25
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Altered Na+ transport after an intracellular alpha-subunit deletion reveals strict external sequential release of Na+ from the Na/K pump. Proc Natl Acad Sci U S A 2009; 106:15507-12. [PMID: 19706387 DOI: 10.1073/pnas.0903752106] [Citation(s) in RCA: 40] [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 Na/K pump actively exports 3 Na(+) in exchange for 2 K(+) across the plasmalemma of animal cells. As in other P-type ATPases, pump function is more effective when the relative affinity for transported ions is altered as the ion binding sites alternate between opposite sides of the membrane. Deletion of the five C-terminal residues from the alpha-subunit diminishes internal Na(+) (Na(i)(+)) affinity approximately 25-fold [Morth et al. (2007) Nature 450:1043-1049]. Because external Na(+) (Na(o)(+)) binding is voltage-dependent, we studied the reactions involving this process by using two-electrode and inside-out patch voltage clamp in normal and truncated (DeltaKESYY) Xenopus-alpha1 pumps expressed in oocytes. We observed that DeltaKESYY (i) decreased both Na(o)(+) and Na(i)(+) apparent affinities in the absence of K(o)(+), and (ii) did not affect apparent Na(o)(+) affinity at high K(o)(+). These results support a model of strict sequential external release of Na(+) ions, where the Na(+)-exclusive site releases Na(+) before the sites shared with K(+) and the DeltaKESYY deletion only reduces Na(o)(+) affinity at the shared sites. Moreover, at nonsaturating K(o)(+), DeltaKESYY induced an inward flow of Na(+) through Na/K pumps at negative potentials. Guanidinium(+) can also permeate truncated pumps, whereas N-methyl-D-glucamine cannot. Because guanidinium(o)(+) can also traverse normal Na/K pumps in the absence of both Na(o)(+) and K(o)(+) and can also inhibit Na/K pump currents in a Na(+)-like voltage-dependent manner, we conclude that the normal pathway transited by the first externally released Na(+) is large enough to accommodate guanidinium(+).
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26
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Han F, Tucker AL, Lingrel JB, Despa S, Bers DM. Extracellular potassium dependence of the Na+-K+-ATPase in cardiac myocytes: isoform specificity and effect of phospholemman. Am J Physiol Cell Physiol 2009; 297:C699-705. [PMID: 19570895 DOI: 10.1152/ajpcell.00063.2009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cardiac Na(+)-K(+)-ATPase (NKA) regulates intracellular Na(+), which in turn affects intracellular Ca(2+) and contractility via the Na(+)/Ca(2+) exchanger. Extracellular K(+) concentration ([K(+)]) is a central regulator of NKA activity. Phospholemman (PLM) has recently been recognized as a critical regulator of NKA in the heart. PLM reduces the intracellular Na(+) affinity of NKA, an effect relieved by PLM phosphorylation. Here we tested whether the NKA alpha(1)- vs. alpha(2)- isoforms have different external K(+) sensitivity and whether PLM and PKA activation affects the NKA affinity for K(+) in mouse cardiac myocytes. We measured the external [K(+)] dependence of the pump current generated by the ouabain-resistant NKA isoform in myocytes from wild-type (WT) mice (i.e., current due to NKA-alpha(1)) and mice in which the NKA isoforms have swapped ouabain affinities (alpha(1) is ouabain sensitive and alpha(2) is ouabain resistant) to assess current due to NKA-alpha(2). We found that NKA-alpha(1) has a higher affinity for external K(+) than NKA-alpha(2) [half-maximal pump activation (K(0.5)) = 1.5 +/- 0.1 vs. 2.9 +/- 0.3 mM]. The apparent external K(+) affinity of NKA was significantly lower in myocytes from WT vs. PLM-knockout mice (K(0.5) = 2.0 +/- 0.2 vs. 1.05 +/- 0.08 mM). However, PKA activation by isoproterenol (1 microM) did not alter the K(0.5) of NKA for external K(+) in WT myocytes. We conclude that 1) NKA-alpha(1) has higher affinity for K(+) than NKA-alpha(2) in cardiac myocytes, 2) PLM decreases the apparent external K(+) affinity of NKA, and 3) phosphorylation of PLM at the cytosolic domain does not alter apparent extracellular K(+) affinity of NKA.
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Affiliation(s)
- Fei Han
- Department of Pathology, Northwestern University, Feinberg School of Chicago, Chicago, Illinois, USA
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27
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Yakushev SS, Kumskova EM, Rubtsov AM, Lopina OD. Effect of colchicine on sensitivity of duck salt gland Na,K-ATPase to Na+. BIOCHEMISTRY (MOSCOW) 2008; 73:990-4. [PMID: 18976215 DOI: 10.1134/s0006297908090058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Low molecular mass proteins of the FXYD family that affect the sensitivity of Na,K-ATPase to Na+ and K+ are known to be present in Na,K-ATPases in various tissues. In particular, in Na,K-ATPase from kidney a gamma-subunit (with electrophoretic mobility corresponding to molecular mass of about 10 kD) is present, and Na,K-ATPase preparations from heart contain phospholemman (electrophoretic mobility of this protein corresponds to molecular mass of 13-14 kD), which provides for the interaction of heart Na,K-ATPase with cytoskeletal microtubules. Disruption of microtubules by colchicine removes phospholemman from heart Na,K-ATPase preparations. The goal of the present study was to reveal a low molecular mass protein (probably a member of FXYD family) in preparation of Na,K-ATPase from duck salt glands. Immunoprecipitation of solubilized duck salt gland Na,K-ATPase using antibodies against alpha1-subunit results in the coprecipitation of a 13 kD protein with the Na,K-ATPase complex. Treatment of homogenate from duck salt glands with colchicine removes this protein from the purified preparation of Na,K-ATPase. Simultaneously, we observed a decrease in the sensitivity of Na,K-ATPase to Na+ at pH 6.5. However, colchicine treatment of homogenate from rabbit kidney does not affect either the sensitivity of Na,K-ATPase obtained from this homogenate to Na+ or the content of 10 kD protein (presumably gamma-subunit). The data suggest that phospholemman (or a similar member of the FXYD family) tightly interacts with Na,K-ATPase from duck salt glands and binds it to microtubules, simultaneously participating in the regulation of the sensitivity of Na,K-ATPase to Na+.
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Affiliation(s)
- S S Yakushev
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
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28
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Abstract
Cardiac glycosides are a diverse family of naturally derived compounds that bind to and inhibit Na+/K+-ATPase. Members of this family have been in clinical use for many years for the treatment of heart failure and atrial arrhythmia, and the mechanism of their positive inotropic effect is well characterized. Exciting recent findings have suggested additional signalling modes of action of Na+/K+-ATPase, implicating cardiac glycosides in the regulation of several important cellular processes and highlighting potential new therapeutic roles for these compounds in various diseases. Perhaps most notably, the increased susceptibility of cancer cells to these compounds supports their potential use as cancer therapies, and the first generation of glycoside-based anticancer drugs are currently in clinical trials.
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29
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Kasturi S, Ismail-Beigi F. Effect of thyroid hormone on the distribution and activity of Na, K-ATPase in ventricular myocardium. Arch Biochem Biophys 2008; 475:121-7. [PMID: 18457653 DOI: 10.1016/j.abb.2008.04.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 04/16/2008] [Accepted: 04/17/2008] [Indexed: 01/29/2023]
Abstract
Employing detergent-free sucrose-density gradient fractionation method we isolated cholesterol-rich lighter membrane fractions containing approximately 10% of protein, approximately 30% of cholesterol in membranes of ventricular myocardium. Cholesterol-rich lighter membrane fractions contain >70% of Na, K-ATPase and caveolins 1 and 3 and <10% of beta-actin. Treatment of hypothyroid rats with T(3) increased the relative abundance of both alpha1 and beta1 Na, K-ATPase subunits in total membranes by 4- to 5-fold (with no change in caveolin-3), and resulted in 1.9-fold increase in enzyme activity. T(3)-induced Na, K-ATPase subunits were preferentially distributed to the lighter fractions (#s 4, 5 and 6); and increased abundance of alpha1 and beta1 were 34-70% and 43-68%, respectively. We conclude that the activity of Na, K-ATPase is not uniform in cardiac membranes, and while a significant amount of Na, K-ATPase is present in cardiac cholesterol-rich membrane fractions, the intrinsic activity is significantly less than the enzyme present in relatively cholesterol-poor membranes.
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Affiliation(s)
- Sriram Kasturi
- Division of Clinical and Molecular Endocrinology, Department of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4951, USA
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Connell JMC, MacKenzie SM, Freel EM, Fraser R, Davies E. A lifetime of aldosterone excess: long-term consequences of altered regulation of aldosterone production for cardiovascular function. Endocr Rev 2008; 29:133-54. [PMID: 18292466 DOI: 10.1210/er.2007-0030] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Up to 15% of patients with essential hypertension have inappropriate regulation of aldosterone; although only a minority have distinct adrenal tumors, recent evidence shows that mineralocorticoid receptor activation contributes to the age-related blood pressure rise and illustrates the importance of aldosterone in determining cardiovascular risk. Aldosterone also has a major role in progression and outcome of ischemic heart disease. These data highlight the need to understand better the regulation of aldosterone synthesis and its action. Aldosterone effects are mediated mainly through classical nuclear receptors that alter gene transcription. In classic epithelial target tissues, signaling mechanisms are relatively well defined. However, aldosterone has major effects in nonepithelial tissues that include increased synthesis of proinflammatory molecules and reactive oxygen species; it remains unclear how these effects are controlled and how receptor specificity is maintained. Variation in aldosterone production reflects interaction of genetic and environmental factors. Although the environmental factors are well understood, the genetic control of aldosterone synthesis is still the subject of debate. Aldosterone synthase (encoded by the CYP11B2 gene) controls conversion of deoxycorticosterone to aldosterone. Polymorphic variation in CYP11B2 is associated with increased risk of hypertension, but the molecular mechanism that accounts for this is not known. Altered 11beta-hydroxylase efficiency (conversion of deoxycortisol to cortisol) as a consequence of variation in the neighboring gene (CYP11B1) may be important in contributing to altered control of aldosterone synthesis, so that the risk of hypertension may reflect a digenic effect, a concept that is discussed further. There is evidence that a long-term increase in aldosterone production from early life is determined by an interaction of genetic and environmental factors, leading to the eventual phenotypes of aldosterone-associated hypertension and cardiovascular damage in middle age and beyond. The importance of aldosterone has generated interest in its therapeutic modulation. Disadvantages associated with spironolactone (altered libido, gynecomastia) have led to a search for alternative mineralocorticoid receptor antagonists. Of these, eplerenone has been shown to reduce cardiovascular risk after myocardial infarction. The benefits and disadvantages of this therapeutic approach are discussed.
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Affiliation(s)
- John M C Connell
- Division of Cardiovascular and Medical Sciences, British Heart Foundation Glasgow Cardiovascular Research Centre, 126 University Place, Glasgow, United Kingdom.
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Liu JG, Zhou NX, Xia HT, Li CG, Li YZ, Li CH. Expression of FXYD6 in pancreatic adenocarcinoma and its clinical significance. Shijie Huaren Xiaohua Zazhi 2008; 16:540-543. [DOI: 10.11569/wcjd.v16.i5.540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the expression of FXYD6 in pancreatic carcinoma and its clinical significance.
METHODS: Immunohistochemistry was used to detect the expression of FXYD6. The relation between the expression of FXYD6 and the clinical pathological factors was analyzed.
RESULTS: FXYD6 was expressed in 42 of 47 pancreatic carcinoma tissue samples. The positive expression rate of FXYD6 in 47 pancreatic cancer tissue samples was 89.34% (42/47). Compared to the expression of FXYD6 in normal pancreatic tissue samples, the expression of FXYD6 in pancreatic carcinoma tissue samples had a statistically significant difference (χ2 = 10.8631, P = 0.0125). According to the FXYD6 expression level, 47 patients were divided into high expression group and low expression group. There was no statistically significant difference in age, gender, tumor size and distant metastasis between the two groups, while there were statistical significances in tumor-differentiation degree(χ2 = 11.562, P = 0.0031), lymphatic metastasis (χ2 = 4.1947, P = 0.0406), TNM staging (χ2 = 9.5995, P = 0.0223). The expression level of FXYD6 protein was related to tumor size (r = 0.2991), differentiation degree (r = 0.6980), lymphatic metastasis (r = 0.4971) and distant metastasis (r = 0.4967).
CONCLUSION: FXYD6 protein plays an important role in the development and progression of pancreatic cancer.
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Affiliation(s)
- Kevin R Mackenzie
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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Dou CQ, Yue X, Zhou NX. Effect of human antisense FXYD6 on the proliferation and invasion of human cholangiocarcinoma cells in vitro. Shijie Huaren Xiaohua Zazhi 2007; 15:929-935. [DOI: 10.11569/wcjd.v15.i9.929] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of human antisense FXYD6 (FXYD domain containing ion transport regulator 6) on the proliferation and invasion of human cholangiocarcinoma cell line QBC939 in vitro.
METHODS: Human cholangiocarcinoma cell line QBC939 was transfected with the plasmid expressing human antisense FXYD6. Meanwhile, the empty vector and non-transfection group were designed. The mRNA transcription level of hFXYD6 was assayed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) with SYBR Green I, and the expression of hFXYD6 protein was detected by immunohistochemistry. MTT and the colony-forming assay were used to measure the ability of cell growth. The cell cycle distribution was analyzed by flow cytometry and Transwell chamber model was employed to test the ability of cell invasion in vitro.
RESULTS: In comparison with the cells transfected with empty vector or without transfection, QBC939 cells transfected with antisense hFXYD6 had a significant decrease in mRNA transcription and protein expression. The cell doubling time was augmented (46.8 h vs 34.5 h, 35.3 h), whereas the colony formation was decreased (24.3% ± 5.3% vs 61.0% ± 8.5%, 58.0% ± 5.6%; P < 0.001). The G1-phase cell population was obviously increased (66.4% ± 2.9% vs 33.5% ± 2.3%, 39.4% ± 3.7%, P < 0.001), but the S-phase one was decreased (18.6% ± 1.6% vs 36.2% ± 2.1%, 34.1% ± 1.6%, P < 0.001). The cells moved from the upper chamber into the lower one in Transwell chamber assay had no marked difference. Between the cells without transfection and transfected with empty vector, there were no significant differences in cell doubling time, colony forming ability, cell cycle distribution and the ability of cell invasion in vitro.
CONCLUSION: Transfection of antisense hFXYD6 can inhibit the ability of cell proliferation, but it has no effect on the ability of cell invasion in human cholangiocarcinoma cell line QBC939 in vitro.
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Srivastava S, Cala SE, Coetzee WA, Artman M. Phospholemman expression is high in the newborn rabbit heart and declines with postnatal maturation. Biochem Biophys Res Commun 2007; 355:338-41. [PMID: 17303081 PMCID: PMC1847634 DOI: 10.1016/j.bbrc.2007.01.194] [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: 01/20/2007] [Accepted: 01/26/2007] [Indexed: 11/28/2022]
Abstract
Phospholemman (PLM) is a small sarcolemmal protein that modulates the activities of Na(+)/K(+)-ATPase and the Na(+)/Ca(2+) exchanger (NCX), thus contributing to the maintenance of intracellular Na(+) and Ca(2+) homeostasis. We characterized the expression and subcellular localization of PLM, NCX, and the Na(+)/K(+)-ATPase alpha1-subunit during perinatal development. Western blotting demonstrates that PLM (15kDa), NCX (120kDa), and Na(+)/K(+)-ATPase alpha-1 (approximately 100kDa) proteins are all more than 2-fold higher in ventricular membrane fractions from newborn rabbit hearts (1-4-day old) compared to adult hearts. Our immunocytochemistry data demonstrate that PLM, NCX, and Na(+)/K(+)-ATPase are all expressed at the sarcolemma of newborn ventricular myocytes. Taken together, our data indicate that PLM, NCX, and Na(+)/K(+)-ATPase alpha-1 proteins have similar developmental expression patterns in rabbit ventricular myocardium. Thus, PLM may have an important regulatory role in maintaining cardiac Na(+) and Ca(2+) homeostasis during perinatal maturation.
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Affiliation(s)
- Shekhar Srivastava
- Department of Pharmacology, New York University School of Medicine, New York, NY 10016
- The Skirball Institute, New York University School of Medicine, New York, NY 10016
| | - Steven E. Cala
- Department of Medicine, Wayne State University School of Medicine, Detroit, Michigan
| | - William A. Coetzee
- Pediatric Cardiology, New York University School of Medicine, New York, NY 10016
| | - Michael Artman
- Department of Pediatrics, University of Iowa, Iowa City, IA 52242
- Corresponding Author: Michael Artman, Children’s Hospital of Iowa, 2636 JCP, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, Phone 319-356-0469; Fax 319-384-6440, Email
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Ramnanan CJ, Storey KB. Suppression of Na+/K+-ATPase activity during estivation in the land snail Otala lactea. ACTA ACUST UNITED AC 2006; 209:677-88. [PMID: 16449562 DOI: 10.1242/jeb.02052] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Entry into the hypometabolic state of estivation requires a coordinated suppression of the rate of cellular ATP turnover, including both ATP-generating and ATP-consuming reactions. As one of the largest consumers of cellular ATP, the plasma membrane Na+/K+-ATPase is a potentially key target for regulation during estivation. Na+/K+-ATPase was investigated in foot muscle and hepatopancreas of the land snail Otala lactea, comparing active and estivating states. In both tissues enzyme properties changed significantly during estivation: maximal activity was reduced by about one-third, affinity for Mg.ATP was reduced (Km was 40% higher), and activation energy (derived from Arrhenius plots) was increased by approximately 45%. Foot muscle Na+/K+-ATPase from estivated snails also showed an 80% increase in Km Na+ and a 60% increase in Ka Mg2+ as compared with active snails, whereas hepatopancreas Na+/K+-ATPase showed a 70% increase in I50 K+ during estivation. Western blotting with antibodies recognizing the alpha subunit of Na+/K+-ATPase showed no change in the amount of enzyme protein during estivation. Instead, the estivation-responsive change in Na+/K+-ATPase activity was linked to posttranslational modification. In vitro incubations manipulating endogenous kinase and phosphatase activities indicated that Na+/K+-ATPase from estivating snails was a high phosphate, low activity form, whereas dephosphorylation returned the enzyme to a high activity state characteristic of active snails. Treatment with protein kinases A, C or G could all mediate changes in enzyme properties in vitro that mimicked the effect of estivation, whereas treatments with protein phosphatase 1 or 2A had the opposite effect. Reversible phosphorylation control of Na+/K+-ATPase can provide the means of coordinating ATP use by this ion pump with the rates of ATP generation by catabolic pathways in estivating snails.
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Affiliation(s)
- Christopher J Ramnanan
- Institute of Biochemistry, College of Natural Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6
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36
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Lifshitz Y, Lindzen M, Garty H, Karlish SJD. Functional interactions of phospholemman (PLM) (FXYD1) with Na+,K+-ATPase. Purification of alpha1/beta1/PLM complexes expressed in Pichia pastoris. J Biol Chem 2006; 281:15790-9. [PMID: 16608841 DOI: 10.1074/jbc.m601993200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human FXYD1 (phospholemman, PLM) has been expressed in Pichia pastoris with porcine alpha1/His10-beta1 subunits of Na+,K+-ATPase or alone. Dodecyl-beta-maltoside-soluble complexes of alpha1/beta1/PLM have been purified by metal chelate chromatography, either from membranes co-expressing alpha1,His10-beta1, and PLM or by in vitro reconstitution of PLM with alpha1/His10-beta1 subunits. Comparison of functional properties of purified alpha1/His10-beta1 and alpha1/His10-beta1/PLM complexes show that PLM lowered K0.5 for Na+ ions moderately (approximately 30%) but did not affect the turnover rate or Km of ATP for activating Na+,K+-ATPase activity. PLM also stabilized the alpha1/His10-beta1 complex. In addition, PLM markedly (>3-fold) reduced the K0.5 of Na+ ions for activating Na+-ATPase activity. In membranes co-expressing alpha1/His10-beta1 with PLM the K0.5 of Na+ ions was also reduced, compared with the control, excluding the possibility that detergent or lipid in purified complexes compromise functional interactions. When expressed in HeLa cells with rat alpha1, rat PLM significantly raised the K0.5 of Na+ ions, whereas for a chimeric molecule consisting of transmembranes segments of PLM and extramembrane segments of FXYD4, the K0.5 of Na+ ions was significantly reduced, compared with the control. The opposite functional effects in P. pastoris and HeLa cells are correlated with endogenous phosphorylation of PLM at Ser68 or unphosphorylated PLM, respectively, as detected with antibodies, which recognize PLM phosphorylated at Ser68 (protein kinase A site) or unphosphorylated PLM. We hypothesize that PLM interacts with alpha1/His10-beta1 subunits at multiple locations, the different functional effects depending on the degree of phosphorylation at Ser68. We discuss the role of PLM in regulation of Na+,K+-ATPase in cardiac or skeletal muscle cells.
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Affiliation(s)
- Yael Lifshitz
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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Mao H, Ferguson TS, Cibulsky SM, Holmqvist M, Ding C, Fei H, Levitan IB. MONaKA, a novel modulator of the plasma membrane Na,K-ATPase. J Neurosci 2006; 25:7934-43. [PMID: 16135750 PMCID: PMC6725465 DOI: 10.1523/jneurosci.0635-05.2005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We have cloned and characterized mouse and human variants of MONaKA, a novel protein that interacts with and modulates the plasma membrane Na,K-ATPase. MONaKA was cloned based on its sequence homology to the Drosophila Slowpoke channel-binding protein dSlob, but mouse and human MONaKA do not bind to mammalian Slowpoke channels. At least two splice variants of MONaKA exist; the splicing is conserved perfectly between mouse and human, suggesting that it serves some important function. Both splice variants of MONaKA are expressed widely throughout the CNS and peripheral nervous system, with different splice variant expression ratios in neurons and glia. A yeast two-hybrid screen with MONaKA as bait revealed that it binds tightly to the beta1 and beta3 subunits of the Na,K-ATPase. The association between MONaKA and Na,K-ATPase beta subunits was confirmed further by coimmunoprecipitation from transfected cells, mouse brain, and cultured mouse astrocytes. A glutathione S-transferase-MONaKA fusion protein inhibits Na,K-ATPase activity from whole brain or cultured astrocytes. Furthermore, transfection of MONaKA inhibits 86Rb+ uptake via the Na,K-ATPase in intact cells. These results are consistent with the hypothesis that MONaKA modulates brain Na,K-ATPase and may thereby participate in the regulation of electrical excitability and synaptic transmission.
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Affiliation(s)
- Hua Mao
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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38
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Zouzoulas A, Blostein R. Regions of the Catalytic α Subunit of Na,K-ATPase Important for Functional Interactions with FXYD 2. J Biol Chem 2006; 281:8539-44. [PMID: 16446368 DOI: 10.1074/jbc.m512700200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma modulator (FXYD 2) is a member of the FXYD family of single transmembrane proteins that modulate the kinetic behavior of Na,K-ATPase. This study concerns the identification of regions in the alpha subunit that are important for its functional interaction with gamma. An important effect of gamma is to increase K+ antagonism of cytoplasmic Na+ activation apparent as an increase in KNa' at high [K+]. We show that although gamma associates with alpha1, alpha2, and alpha3 isoforms, it increases the KNa' of alpha1 and alpha3 but not alpha2. Accordingly, chimeras of alpha1 and alpha2 were used to identify regions of alpha critical for the increased KNa'. As with alpha1 and alpha2, all chimeras associate with gamma. Kinetic analysis of alpha2front/alpha1back chimeras indicate that the C-terminal (Lys907-Tyr1018) region of alpha1, which includes transmembrane (TM)9 close to gamma, is important for the increase in KNa'. However, similar experiments with alpha1front/alpha2back chimeras indicate a modulatory role of the loop between TMs 7 and 8. Thus, as long as the alpha1 L7/8 loop is present, replacement of TM9 of alpha1 with that of alpha2 does not abrogate the gamma effect on KNa'. In contrast, as long as TM9 is that of alpha1, replacement of L7/8 of alpha1 with that of alpha2 does not abolish the effect. It is suggested that structural association of the TM regions of alpha and FXYD 2 is not the sole determinant of this effect of FXYD on KNa' but is subject to long range modulation by the extramembranous L7/8 loop of alpha.
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Affiliation(s)
- Athina Zouzoulas
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1A4, Canada
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Abstract
The Na,K-adenosine triphosphatase (ATPase), or sodium pump, has been well studied for its role in the regulation of ion homeostasis in mammalian cells. Recent studies suggest that Na,K-ATPase might have multiple functions such as a role in the regulation of tight junction structure and function, induction of polarity, regulation of actin dynamics, control of cell movement, and cell signaling. These functions appear to be modulated by Na,K-ATPase enzyme activity as well as protein-protein interactions of the alpha and beta subunits. In this review we attempt to differentiate functions associated with enzyme activity and subunit interactions. In addition, the consequence of impaired Na,K-ATPase function or reduced subunit expression levels in kidney diseases such as cancer, tubulointerstitial fibrosis, and ischemic nephropathy are discussed.
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Affiliation(s)
- Sigrid A Rajasekaran
- Department of Pathology and Laboratory Medicine, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
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40
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Lindzen M, Gottschalk KE, Füzesi M, Garty H, Karlish SJD. Structural interactions between FXYD proteins and Na+,K+-ATPase: alpha/beta/FXYD subunit stoichiometry and cross-linking. J Biol Chem 2005; 281:5947-55. [PMID: 16373350 DOI: 10.1074/jbc.m512063200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interactions of rat FXYD4 (corticosteroid hormone-induced factor (CHIF)), FXYD2 (gamma), or FXYD1 (phospholemman (PLM)) proteins with rat alpha1 subunits of Na(+),K(+)-ATPase have been analyzed by co-immunoprecipitation and covalent cross-linking. In detergent-solubilized membranes from HeLa cells expressing both gamma and CHIF or CHIF and hemagglutinin A-tagged CHIF, mixed complexes of CHIF and gamma or CHIF and hemagglutinin A-tagged CHIF with alpha/beta subunits are undetectable. This implies that the alpha/beta/FXYD protomer is the major species in detergent solution. A lipid-soluble cysteine-cysteine bifunctional reagent, dibromobimane, cross-links CHIF to alpha in colonic membranes but not gamma or PLM to alpha in kidney or heart membranes, respectively. Sequence comparisons of the FXYD proteins suggested that Cys-49 in the trans-membrane segment of CHIF could be involved. In detergent-solubilized HeLa cell membranes, dibromobimane cross-links wild-type CHIF to alpha but not the C49F mutant, and also the corresponding F36C mutant but not wild-type gammab, and F48C but not wild-type PLM. C140S, C338A, C804A, and C966S mutants of the alpha subunit have been expressed. Only the C140S mutant prevents cross-linking with CHIF. The data demonstrated the proximity of trans-membrane segments of CHIF, gamma, and PLM to M2 of alpha. Molecular modeling is consistent with location of the trans-membrane segment of all FXYD proteins between M2, M6, and M9 and the proximity of Cys-49 of CHIF or Phe-36 of gamma with Cys-140 of M2. Cross-linking also demonstrated CHIF-alpha and CHIF-beta proximities in extra-membrane regions, similar to the evidence for gamma-alpha and gamma-beta cross-links.
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Affiliation(s)
- Moshit Lindzen
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
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41
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Fletcher N, Wahlström D, Lundberg R, Nilsson CB, Nilsson KC, Stockling K, Hellmold H, Håkansson H. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) alters the mRNA expression of critical genes associated with cholesterol metabolism, bile acid biosynthesis, and bile transport in rat liver: a microarray study. Toxicol Appl Pharmacol 2005; 207:1-24. [PMID: 16054898 DOI: 10.1016/j.taap.2004.12.003] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 12/02/2004] [Accepted: 12/03/2004] [Indexed: 12/30/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent hepatotoxin that exerts its toxicity through binding to the aryl hydrocarbon receptor (AhR) and the subsequent induction or repression of gene transcription. In order to further identify novel genes and pathways that may be associated with TCDD-induced hepatotoxicity, we investigated gene changes in rat liver following exposure to single oral doses of TCDD. Male Sprague-Dawley rats were administered single doses of 0.4 microg/kg bw or 40 microg/kg bw TCDD and killed at 6 h, 24 h, or 7 days, for global analyses of gene expression. In general, low-dose TCDD exposure resulted in greater than 2-fold induction of genes coding for a battery of phase I and phase II metabolizing enzymes including CYP1A1, CYP1A2, NADPH quinone oxidoreductase, UGT1A6/7, and metallothionein 1. However, 0.4 microg/kg bw TCDD also altered the expression of Gadd45a and Cyclin D1, suggesting that even low-dose TCDD exposure can alter the expression of genes indicative of cellular stress or DNA damage and associated with cell cycle control. At the high-dose, widespread changes were observed for genes encoding cellular signaling proteins, cellular adhesion, cytoskeletal and membrane transport proteins as well as transcripts coding for lipid, carbohydrate and nitrogen metabolism. In addition, decreased expression of cytochrome P450 7A1, short heterodimer partner (SHP; gene designation nr0b2), farnesyl X receptor (FXR), Ntcp, and Slc21a5 (oatp2) were observed and confirmed by RT-PCR analyses in independent rat liver samples. Altered expression of these genes implies major deregulation of cholesterol metabolism and bile acid synthesis and transport. We suggest that these early and novel changes have the potential to contribute significantly to TCDD induced hepatotoxicity and hypercholesterolemia.
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Affiliation(s)
- Nick Fletcher
- Institute of Environmental Medicine, Karolinska Institutet, Nobels vag 13, Stockholm, Sweden
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Abstract
The Na,K-ATPase comprises a family of isozymes that catalyze the active transport of cytoplasmic Na+ for extracellular K+ at the plasma membrane of cells. Isozyme diversity for the Na,K-ATPase results from the association of different molecular forms of the alpha (alpha1, alpha2, alpha3, and alpha4) and beta (beta1, beta2, and beta3) subunits that constitute the enzyme. The various isozymes are characterized by unique enzymatic properties and a highly regulated pattern of expression that depends on cell type, developmental stage, and hormonal stimulation. The molecular complexity of the Na,K-ATPase goes beyond its alpha and beta isoforms and, in certain tissues, other accessory proteins associate with the enzyme. These small membrane-bound polypeptides, known as the FXYD proteins, modulate the kinetic characteristics of the Na,K-ATPase. The experimental evidence available suggests that the molecular and functional heterogeneity of the Na,K-ATPase is a physiologically relevant event that serves the specialized functions of cells. This article focuses on the functional properties, regulation, and the biological relevance of the Na,K-ATPase isozymes as a mechanism for the tissue-specific control of Na+ and K+ homeostasis.
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Affiliation(s)
- Gustavo Blanco
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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Paulusma CC, Oude Elferink RPJ. The type 4 subfamily of P-type ATPases, putative aminophospholipid translocases with a role in human disease. Biochim Biophys Acta Mol Basis Dis 2005; 1741:11-24. [PMID: 15919184 DOI: 10.1016/j.bbadis.2005.04.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Revised: 04/21/2005] [Accepted: 04/25/2005] [Indexed: 11/22/2022]
Abstract
The maintenance of phospholipid asymmetry in membrane bilayers is a paradigm in cell biology. However, the mechanisms and proteins involved in phospholipid translocation are still poorly understood. Members of the type 4 subfamily of P-type ATPases have been implicated in the translocation of phospholipids from the outer to the inner leaflet of membrane bilayers. In humans, several inherited disorders have been identified which are associated with loci harboring type 4 P-type ATPase genes. Up to now, one inherited disorder, Byler disease or progressive familial intrahepatic cholestasis type 1 (PFIC1), has been directly linked to mutations in a type 4 P-type ATPase gene. How the absence of an aminophospholipid translocase activity relates to this severe disease is, however, still unclear. Studies in the yeast Saccharomyces cerevisiae have recently identified important roles for type 4 P-type ATPases in intracellular membrane- and protein-trafficking events. These processes require an (amino)phospholipid translocase activity to initiate budding or fusion of membrane vesicles from or with other membranes. The studies in yeast have greatly contributed to our cell biological insight in membrane dynamics and intracellular-trafficking events; if this knowledge can be translated to mammalian cells and organs, it will help to elucidate the molecular mechanisms which underlie severe inherited human diseases such as Byler disease.
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Affiliation(s)
- C C Paulusma
- Department of Experimental Hepatology, Academic Medical Center/AMC Liver Center, Meibergdreef 69-71, 1105 BK Amsterdam, The Netherlands.
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44
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Kelly CE, Ram ML, Francis SA, Houle TD, Cala SE. Identification of a cytoskeleton-bound form of phospholemman with unique C-terminal immunoreactivity. J Membr Biol 2005; 202:127-35. [PMID: 15798901 DOI: 10.1007/s00232-004-0724-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2004] [Revised: 10/19/2004] [Indexed: 10/25/2022]
Abstract
Phospholemman (PLM) is a 72-amino acid transmembrane protein thought to function in Na,K-ATPase regulation or assembly, similar to other members of the FXYD family of proteins. Unique to PLM among these regulatory proteins are sites for C-terminal phosphorylation by PKA and PKC, although a role for phosphorylation in PLM function remains unclear. To study PLM phosphorylation, we used PLM phosphopeptides to generate antibodies to specifically detect phosphorylated PLM. Peptide affinity chromatography isolated two populations of antibodies: one reacting with standard PLM, a collection of closely-spaced 15-kDa protein bands by SDS-PAGE. About 20% of PLM antibodies reacted specifically with a single distinct form of PLM. Levels of this second immunological form (PLM-b) were increased with overexpression of PLM cDNA, and also reacted with a monoclonal antibody against the PLM N-terminus. In complete contrast to standard PLM, however, PLM-b was quantitatively insoluble in nonionic detergents and was released from tight binding by colchicine. Antibodies to PLM-b were present in two different antisera raised to the phosphorylated C-terminal peptide (residues 57-70), but not in antiserum raised to the non-phosphorylated C-terminal peptide. Despite an apparent relationship between PLM-b and phosphorylated PLM, PLM-b levels were not affected by treatment of heart cells with isoproterenol. PLM-b appears to represent a cytoskeleton-attached detergent-insoluble form of PLM with distinctive C-terminal immunoreactivity that might have implications for PLM structure and function.
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Affiliation(s)
- C E Kelly
- Program in Molecular and Cellular Cardiology, Wayne State University School of Medicine, 421 East Canfield Avenue, Detroit, MI 48201, USA
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Zouzoulas A, Dunham PB, Blostein R. The Effect of the Gamma Modulator on Na/K Pump Activity of Intact Mammalian Cells. J Membr Biol 2005; 204:49-56. [PMID: 16007503 DOI: 10.1007/s00232-005-0746-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Revised: 03/30/2005] [Indexed: 11/30/2022]
Abstract
This study concerns the modulatory effects of the gamma modulator of the Na/K pump, in particular whether the effects seen in previous experiments with isolated membranes are relevant to Na/K pump behavior in intact mammalian cells. For this purpose, HeLa cells previously transfected with the rat Na/K catalytic subunit were used. The results show that both variants of the regulator, gammaa and gammab, decrease the apparent affinity of the pump for Na(+) and cause a modest increase in apparent ATP affinity as seen in measurements of ouabain-sensitive (86)Rb(K(+)) influx into cells in which ATP was varied using antimycin A and glucose. Equivalent results had been obtained previously in our analyses of Na,K-ATPase activity of membrane fragments, i.e., an increase in K(0.5(Na)) at high K(+) concentration and a decrease in K'(ATP). Comparison of clones of gamma-transfected and mock-transfected cells (with similar V(max) values) indicated that gamma causes a modest approximately 30% increase in the steady-state concentration of intracellular Na(+). Furthermore, for both gammaa and gammab, values of intracellular Na(+) were similar to those predicted from the kinetic constants, K(0.5(Na)) and V(max). Finally, there was a gamma-mediated increase in apparent affinity for extracellular K(+), which had not been detected in assays of permeabilized membranes.
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Affiliation(s)
- A Zouzoulas
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada
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Abstract
Na,K-ATPase is responsible for maintaining the correct concentrations of sodium and potassium in lens cells. Na,K-ATPase activity is different in the two cell types that make up the lens, epithelial cells and fibers; specific activity in the epithelium is higher than in fibers. In some parts of the fiber mass Na,K-ATPase activity is barely detectable. There is a large body of evidence that suggests Na,K-ATPase-mediated ion transport by the epithelium contributes significantly to the regulation of ionic composition in the entire lens. In some species different Na,K-ATPase isoforms are present in epithelium and fibers but in general, fibers and epithelium express a similar amount of Na,K-ATPase protein. Turnover of Na,K-ATPase by protein synthesis may contribute to preservation of high Na,K-ATPase activity in the epithelium. In ageing lens fibers, oxidation, and glycation may decrease Na,K-ATPase activity. Na,K-ATPase activity in lens fibers and epithelium also may be subject to regulation as the result of protein tyrosine phosphorylation. Moreover, activation of G protein-coupled receptors by agonists such as endothelin-1 elicits changes of Na,K-ATPase activity. The asymmetrical distribution of Na,K-ATPase activity in the epithelium and fibers may contribute to ionic currents that flow in and around the lens. Studies on human cataract and experimental cataract in animals reveal changes of Na,K-ATPase activity but no clear pattern is evident. However, there is a convincing link between abnormal elevation of lens sodium and the opacification of the lens cortex that occurs in age-related human cataract.
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Affiliation(s)
- Nicholas A Delamere
- Department of Ophthalmology and Visual Sciences, School of Medicine, Louisville, Kentucky, USA.
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Hirose S, Kaneko T, Naito N, Takei Y. Molecular biology of major components of chloride cells. Comp Biochem Physiol B Biochem Mol Biol 2004; 136:593-620. [PMID: 14662288 DOI: 10.1016/s1096-4959(03)00287-2] [Citation(s) in RCA: 225] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Current understanding of chloride cells (CCs) is briefly reviewed with emphasis on molecular aspects of their channels, transporters and regulators. Seawater-type and freshwater-type CCs have been identified based on their shape, location and response to different ionic conditions. Among the freshwater-type CCs, subpopulations are emerging that are implicated in the uptake of Na(+), Cl(-) and Ca(2+), respectively, and can be distinguished by their shape of apical crypt and affinity for lectins. The major function of the seawater CC is transcellular secretion of Cl(-), which is accomplished by four major channels and transporters: (1). CFTR Cl(-) channel, (2). Na(+),K(+)-ATPase, (3). Na(+)/K(+)/2Cl(-) cotransporter and (4). a K(+) channel. The first three components have been cloned and characterized, but concerning the K(+) channel that is essential for the continued generation of the driving force by Na(+),K(+)-ATPase, only one candidate is identified. Although controversial, freshwater CCs seem to perform the uptake of Na(+), Cl(-) and Ca(2+) in a manner analogous to but slightly different from that seen in the absorptive epithelia of mammalian kidney and intestine since freshwater CCs face larger concentration gradients than ordinary epithelial cells. The components involved in these processes are beginning to be cloned, but their CC localization remains to be established definitively. The most important yet controversial issue is the mechanism of Na(+) uptake. Two models have been postulated: (i). the original one involves amiloride-sensitive electroneutral Na(+)/H(+) exchanger (NHE) with the driving force generated by Na(+),K(+)-ATPase and carbonic anhydrase (CA) and (ii). the current model suggests that Na(+) uptake occurs through an amiloride-sensitive epithelial sodium channel (ENaC) electrogenically coupled to H(+)-ATPase. While fish ENaC remains to be identified by molecular cloning and database mining, fish NHE has been cloned and shown to be highly expressed on the apical membrane of CCs, reviving the original model. The CC is also involved in acid-base regulation. Analysis using Osorezan dace (Tribolodon hakonensis) living in a pH 3.5 lake demonstrated marked inductions of Na(+),K(+)-ATPase, CA-II, NHE3, Na(+)/HCO(3)(-) cotransporter-1 and aquaporin-3 in the CCs on acidification, leading to a working hypothesis for the mechanism of Na(+) retention and acid-base regulation.
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Affiliation(s)
- Shigehisa Hirose
- Department of Biological Sciences, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
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Abstract
Because nearly all structure/function studies on Na(+)/K(+)-ATPase have been done on enzymes prepared in the presence of SDS, we have studied previously unrecognized consequences of SDS interaction with the enzyme. When the purified membrane-bound kidney enzyme was solubilized with SDS or TDS concentrations just sufficient to cause complete solubilization, but not at concentrations severalfold higher, the enzyme retained quaternary structure, exhibiting alpha,alpha-, alpha,beta-, beta,beta-, and alpha,gamma-associations as detected by chemical cross-linking. The presence of solubilized oligomers was confirmed by sucrose density gradient centrifugation. This solubilized enzyme had no ATPase activity and was not phosphorylated by ATP, but it retained the ability to occlude Rb(+) and Na(+). This, and comparison of cross-linking patterns obtained with different reagents, suggested that the transmembrane domains of the enzyme are more resistant to SDS-induced unfolding than its other domains. These findings (a). indicate that the partially unfolded oligomer(s) retaining partial function is the intermediate in the SDS-induced denaturation of the native membrane enzyme having the minimum oligomeric structure of (alpha,beta,gamma)(2) and (b). suggest potential functions for Na(+)/K(+)-ATPase with intrinsically unfolded domains. Mixtures of solubilized/partially unfolded enzyme and membrane-bound enzyme exhibited cross-linking patterns and Na(+) occlusion capacities different from those of either enzyme species, suggesting that the two interact. Formation of the partially unfolded enzyme during standard purification procedure for the preparation of the membrane-bound enzyme was shown, indicating that it is necessary to ensure the separation of the partially unfolded enzyme from the membrane-bound enzyme to avoid the distortion of the properties of the latter.
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Affiliation(s)
- Alexander V Ivanov
- Department of Pharmacology, Medical College of Ohio, Toledo, Ohio 43614-5804, USA
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Kadowaki K, Sugimoto K, Yamaguchi F, Song T, Watanabe Y, Singh K, Tokuda M. Phosphohippolin expression in the rat central nervous system. ACTA ACUST UNITED AC 2004; 125:105-12. [PMID: 15193427 DOI: 10.1016/j.molbrainres.2004.03.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/16/2004] [Indexed: 11/18/2022]
Abstract
The FXYD family is a small single-span membrane protein family; recently, we have identified a novel member of this family from the cDNA library of the rat hippocampus and named phosphohippolin (Php) (Mol. Br. Res. vol. 86, 2001). The deduced amino acid sequence of this novel Php comprises 93 residues with a core motif of FXYD and a single transmembrane domain. This indicates that Php belongs to FXYD6 subfamily of the seven FXYD subfamilies (FXYD1-7). Php shows a 48.1% homology with rat phospholemman (FXYD1), a transmembrane family protein. In this study, polyclonal antibodies against the carboxyl-terminal sequence of rat Php were raised and purified. The spatial expression of the Php protein was in the neuronal fibers of the medial part of lateral habenula nucleus, thalamus, hypothalamus, stria terminalis, zona incerta, amygdaloid body and cingulum, olfactory bulb, hippocampus, cerebral cortex and cerebellum. A unique Php distribution was identified in the cerebellum, with a predominant expression pattern in the granule layer of lobules VI-IX of the posterior lobe. Developmental studies demonstrated that the highest level of Php expression was seen in the postnatal (PN) 3-week-old rat brain, and a significant amount of Php still existed in the adult brain. These findings suggest that Php may play an important role in the excitability of neurons in the central nervous system during postnatal development, as well as those in the adult brain.
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Affiliation(s)
- Kae Kadowaki
- Department of Cell Physiology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki-cho, 761-0793, Japan
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