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Cao XY, Liu Y, Kan JS, Huang XX, Kambey PA, Zhang CT, Gao J. Microglial SIX2 suppresses lipopolysaccharide (LPS)-induced neuroinflammation by up-regulating FXYD2 expression. Brain Res Bull 2024; 212:110970. [PMID: 38688414 DOI: 10.1016/j.brainresbull.2024.110970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 04/15/2024] [Accepted: 04/26/2024] [Indexed: 05/02/2024]
Abstract
Parkinson's disease (PD) is a severe neurodegenerative disease associated with the loss of dopaminergic (DA) neurons in the substantia nigra (SN). Although its pathogenesis remains unclear, microglia-mediated neuroinflammation significantly contributes to the development of PD. Here we showed that the sine oculis homeobox (SIX) homologue family transcription factors SIX2 exerted significant effects on neuroinflammation. The SIX2 protein, which is silenced during development, was reactivated in lipopolysaccharide (LPS)-treated microglia. The reactivated SIX2 in microglia mitigated the LPS induced inflammatory effects, and then reduced the toxic effect of conditioned media (CM) of microglia on co-cultured MES23.5 DA cells. Using the LPS-stimulated Cx3cr1-CreERT2 mouse model, we also demonstrated that the highly-expressed SIX2 in microglia obviously attenuated neuroinflammation and protected the DA neurons in SN. Further RNA-Seq analysis on the inflammatory activated microglia revealed that the SIX2 exerted these effects via up-regulating the FXYD domain containing ion transport regulator 2 (FXYD2). Taken together, our study demonstrated that SIX2 was an endogenous anti-inflammatory factor in microglia, and it exerted anti-neuroinflammatory effects by regulating the expression of FXYD2, which provides new ideas for anti-neuroinflammation in PD.
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Affiliation(s)
- Xia-Yin Cao
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Yi Liu
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Jia-Shuo Kan
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xin-Xing Huang
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Piniel Alphayo Kambey
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Can-Tang Zhang
- Department of Respiratory and Critical Care, the Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Jin Gao
- Department of Neurobiology and Cellular biology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China.
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2
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Zhang Z, Tang Y, Li L, Yang W, Xu Y, Zhou J, Ma K, Zhang K, Zhuang H, Gong Y, Gong K. Downregulation of FXYD2 Is Associated with Poor Prognosis and Increased Regulatory T Cell Infiltration in Clear Cell Renal Cell Carcinoma. J Immunol Res 2022; 2022:4946197. [PMID: 36313180 PMCID: PMC9606837 DOI: 10.1155/2022/4946197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 09/15/2022] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND FXYD2, a gene coding for the γ subunit of Na+/K+-ATPase, was demonstrated to involve in carcinogenesis recently. However, the specific role of FXYD2 in clear cell renal cell carcinoma (ccRCC) remains unknown. The current study was conducted to investigate the expression, biological function, and potentially immune-related mechanisms of FXYD2 in ccRCC. Materials and methods. The data from TCGA-KIRC, ICGC, GEO, Oncomine, ArrayExpress, TIMER, HPA datasets, and our clinical samples were used to determine and validate the expression level, prognostic roles, and potentially immune-related mechanisms in ccRCC. Cell function assays were performed to investigate the biological role of FXYD2 in vitro. RESULTS FXYD2 was identified to be downregulated in ccRCC tissue compared to normal tissue, which was confirmed by our RT-PCR, WB, and IHC analyses. Kaplan-Meier survival analysis and Cox regression analysis suggested that downregulated FXYD2 could independently predict poor survival of ccRCC patients. Through the ESTIMATE algorithm, ssGSEA algorithm, CIBERSORT algorithm, TIMER database, and our laboratory experiment, FXYD2 was found to correlate with the immune landscape, especially regulatory T cells (Treg), in ccRCC. Gain-of-function experiment revealed that FXYD2 could restrain cell proliferation, migration, and invasion in vitro. Functional enrichment analysis illustrated that TGF-β-SMAD2/3, Notch, and PI3K-Akt-mTOR signaling pathways may be potential signaling pathways of FXYD2 in ccRCC. CONCLUSIONS Downregulation of FXYD2 is associated with ccRCC tumorigenesis, poor prognosis, and increased Treg infiltration in ccRCC, which may be related to TGF-β-SMAD2/3, Notch, and PI3K-Akt-mTOR signaling pathways. This will probably provide a novel prognostic marker and potential therapeutic target for ccRCC.
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Affiliation(s)
- Zedan Zhang
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Yanlin Tang
- Shantou University Medical College, Shantou, China
| | - Lei Li
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Wuping Yang
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Yawei Xu
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Jingcheng Zhou
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Kaifang Ma
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Kenan Zhang
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Hongkai Zhuang
- Department of Hepatobiliary Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Yanqing Gong
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
| | - Kan Gong
- Department of Urology, Peking University First Hospital, Beijing, China
- Hereditary Kidney Cancer Research Center, Peking University First Hospital, Beijing, China
- Institute of Urology, Peking University, Beijing, China
- National Urological Cancer Center, Beijing, China
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3
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Yap JQ, Seflova J, Sweazey R, Artigas P, Robia SL. FXYD proteins and sodium pump regulatory mechanisms. J Gen Physiol 2021; 153:211866. [PMID: 33688925 PMCID: PMC7953255 DOI: 10.1085/jgp.202012633] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 02/03/2021] [Indexed: 12/12/2022] Open
Abstract
The sodium/potassium-ATPase (NKA) is the enzyme that establishes gradients of sodium and potassium across the plasma membrane. NKA activity is tightly regulated for different physiological contexts through interactions with single-span transmembrane peptides, the FXYD proteins. This diverse family of regulators has in common a domain containing a Phe-X-Tyr-Asp (FXYD) motif, two conserved glycines, and one serine residue. In humans, there are seven tissue-specific FXYD proteins that differentially modulate NKA kinetics as appropriate for each system, providing dynamic responsiveness to changing physiological conditions. Our understanding of how FXYD proteins contribute to homeostasis has benefitted from recent advances described in this review: biochemical and biophysical studies have provided insight into regulatory mechanisms, genetic models have uncovered remarkable complexity of FXYD function in integrated physiological systems, new posttranslational modifications have been identified, high-resolution structural studies have revealed new details of the regulatory interaction with NKA, and new clinical correlations have been uncovered. In this review, we address the structural determinants of diverse FXYD functions and the special roles of FXYDs in various physiological systems. We also discuss the possible roles of FXYDs in protein trafficking and regulation of non-NKA targets.
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Affiliation(s)
- John Q Yap
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Jaroslava Seflova
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
| | - Ryan Sweazey
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
| | - Seth L Robia
- Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, IL
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4
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Demine S, Schulte ML, Territo PR, Eizirik DL. Beta Cell Imaging-From Pre-Clinical Validation to First in Man Testing. Int J Mol Sci 2020; 21:E7274. [PMID: 33019671 PMCID: PMC7582644 DOI: 10.3390/ijms21197274] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/21/2020] [Accepted: 09/28/2020] [Indexed: 12/14/2022] Open
Abstract
There are presently no reliable ways to quantify human pancreatic beta cell mass (BCM) in vivo, which prevents an accurate understanding of the progressive beta cell loss in diabetes or following islet transplantation. Furthermore, the lack of beta cell imaging hampers the evaluation of the impact of new drugs aiming to prevent beta cell loss or to restore BCM in diabetes. We presently discuss the potential value of BCM determination as a cornerstone for individualized therapies in diabetes, describe the presently available probes for human BCM evaluation, and discuss our approach for the discovery of novel beta cell biomarkers, based on the determination of specific splice variants present in human beta cells. This has already led to the identification of DPP6 and FXYD2ga as two promising targets for human BCM imaging, and is followed by a discussion of potential safety issues, the role for radiochemistry in the improvement of BCM imaging, and concludes with an overview of the different steps from pre-clinical validation to a first-in-man trial for novel tracers.
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Affiliation(s)
- Stephane Demine
- Indiana Biosciences Research Institute, Indianapolis, IN 46202, USA;
| | - Michael L. Schulte
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (M.L.S.); (P.R.T.)
| | - Paul R. Territo
- Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (M.L.S.); (P.R.T.)
- Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Decio L. Eizirik
- Indiana Biosciences Research Institute, Indianapolis, IN 46202, USA;
- ULB Center for Diabetes Research, Medical Faculty, Université Libre de Bruxelles (ULB), 1070 Brussels, Belgium
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5
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Groß A, Chernyakov D, Gallwitz L, Bornkessel N, Edemir B. Deletion of Von Hippel-Lindau Interferes with Hyper Osmolality Induced Gene Expression and Induces an Unfavorable Gene Expression Pattern. Cancers (Basel) 2020; 12:cancers12020420. [PMID: 32059438 PMCID: PMC7073186 DOI: 10.3390/cancers12020420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 01/31/2020] [Accepted: 02/06/2020] [Indexed: 12/19/2022] Open
Abstract
Loss of von Hippel–Lindau (VHL) protein function can be found in more than 90% of patients with clear cell renal carcinoma (ccRCC). Mice lacking Vhl function in the kidneys have urine concentration defects due to postulated reduction of the hyperosmotic gradient. Hyperosmolality is a kidney-specific microenvironment and induces a unique gene expression pattern. This gene expression pattern is inversely regulated in patients with ccRCC with consequences for cancer-specific survival. Within this study, we tested the hypothesis if Vhl function influences the hyperosmolality induced changes in gene expression. We made use of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology to inhibit functional Vhl expression in murine collecting duct cell line. Loss of Vhl function induced morphological changes within the cells similar to epithelial to mesenchymal transition like phenotype. Vhl-deficient cells migrated faster and proliferated slower compared to control cells. Gene expression profiling showed significant changes in gene expression patterns in Vhl-deficient cells compared to control cells. Several genes with unfavorable outcomes showed induced and genes with favorable outcomes for patients with renal cancer reduced gene expression level. Under hyperosmotic condition, the expression of several hyperosmolality induced genes, with favorable prognostic value, was downregulated in cells that do not express functional Vhl. Taken together, this study shows that Vhl interferes with hyperosmotic signaling pathway and hyperosmolality affected pathways might represent new promising targets.
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Affiliation(s)
| | | | | | | | - Bayram Edemir
- Correspondence: ; Tel.: +49-345-557-4890; Fax: +49-345-557-2950
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6
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Hormonal regulation of Na +-K +-ATPase from the evolutionary perspective. CURRENT TOPICS IN MEMBRANES 2019; 83:315-351. [PMID: 31196608 DOI: 10.1016/bs.ctm.2019.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Na+-K+-ATPase, an α/β heterodimer, is an ancient enzyme that maintains Na+ and K+ gradients, thus preserving cellular ion homeostasis. In multicellular organisms, this basic housekeeping function is integrated to fulfill the needs of specialized organs and preserve whole-body homeostasis. In vertebrates, Na+-K+-ATPase is essential for many fundamental physiological processes, such as nerve conduction, muscle contraction, nutrient absorption, and urine excretion. During vertebrate evolution, three key developments contributed to diversification and integration of Na+-K+-ATPase functions. Generation of novel α- and β-subunits led to formation of multiple Na+-K+-ATPase isoenyzmes with distinct functional characteristics. Development of a complex endocrine system enabled efficient coordination of diverse Na+-K+-ATPase functions. Emergence of FXYDs, small transmembrane proteins that regulate Na+-K+-ATPase, opened new ways to modulate its function. FXYDs are a vertebrate innovation and an important site of hormonal action, suggesting they played an especially prominent role in evolving interaction between Na+-K+-ATPase and the endocrine system in vertebrates.
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7
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Kemmner S, Bachmann Q, Steiger S, Lorenz G, Honarpisheh M, Foresto-Neto O, Wang S, Carbajo-Lozoya J, Alt V, Schulte C, Chmielewski S, Bluyssen HAR, Heemann U, Baumann M, Lech M, Schmaderer C. STAT1 regulates macrophage number and phenotype and prevents renal fibrosis after ischemia-reperfusion injury. Am J Physiol Renal Physiol 2018; 316:F277-F291. [PMID: 30403164 DOI: 10.1152/ajprenal.00004.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Renal ischemia-reperfusion injury (IRI) leads to acute kidney injury or delayed allograft function, which predisposes to fibrosis in the native kidney or kidney transplant. Here we investigated the role of the signal transducer and activator of transcription 1 (STAT1) in inflammatory responses following renal IRI. Our study showed that a subsequent stimulation of Janus-activated kinase 2/STAT1 and Toll-like receptor 4 pathways led to greater STAT1 activation followed by increased cytokine transcription compared with single-pathway stimulation in murine renal tubular cells. Moreover, we observed increased activation of STAT1 under hypoxic conditions. In vivo, STAT1-/- mice displayed less acute tubular necrosis and decreased macrophage infiltration 24 h after renal ischemia. However, investigation of the healing phase (30 days after IRI) revealed significantly more fibrosis in STAT1-/- than in wild-type kidneys. In addition, we demonstrated increased macrophage infiltration in STAT1-/- kidneys. Flow cytometry analysis revealed that STAT1 deficiency drives an alternatively activated macrophage phenotype, which is associated with downregulated cluster of differentiation 80 expression, decreased intracellular reactive oxygen species production, and enhanced ability for phagocytosis. Furthermore, we detected immunohistochemically enhanced STAT1 expression in human renal allograft biopsies with no interstitial fibrosis/tubular atrophy (IF/TA) compared with specimens with severe IF/TA without specific etiology. Thus, STAT1 activation drives macrophages toward an alternatively activated phenotype and enhances fibrogenesis indicating a potential STAT1-driven protective mechanism in tissue repair after ischemic injury.
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Affiliation(s)
- Stephan Kemmner
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Quirin Bachmann
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Stefanie Steiger
- Medizinische Klinik und Poliklinik IV, Department of Nephrology, Klinikum der Ludwig-Maximilians-Universität München, Munich , Germany
| | - Georg Lorenz
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Mohsen Honarpisheh
- Medizinische Klinik und Poliklinik IV, Department of Nephrology, Klinikum der Ludwig-Maximilians-Universität München, Munich , Germany
| | - Orestes Foresto-Neto
- Medizinische Klinik und Poliklinik IV, Department of Nephrology, Klinikum der Ludwig-Maximilians-Universität München, Munich , Germany
| | - Shijun Wang
- Pediatric Research Center, Hannover Medical School , Hannover , Germany
| | - Javier Carbajo-Lozoya
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Verena Alt
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Christian Schulte
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Stefan Chmielewski
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany.,Department of Human Molecular Genetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznań , Poznań , Poland
| | - Hans A R Bluyssen
- Department of Human Molecular Genetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznań , Poznań , Poland
| | - Uwe Heemann
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Marcus Baumann
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
| | - Maciej Lech
- Medizinische Klinik und Poliklinik IV, Department of Nephrology, Klinikum der Ludwig-Maximilians-Universität München, Munich , Germany
| | - Christoph Schmaderer
- Department of Nephrology, Klinikum Rechts der Isar, Technical University of Munich , Munich , Germany
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8
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Mayan H, Farfel Z, Karlish SJD. Renal Mg handling, FXYD2 and the central role of the Na,K-ATPase. Physiol Rep 2018; 6:e13843. [PMID: 30175537 PMCID: PMC6119663 DOI: 10.14814/phy2.13843] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 07/30/2018] [Accepted: 08/01/2018] [Indexed: 12/15/2022] Open
Abstract
This article examines the central role of Na,K-ATPase (α1β1FXYD2) in renal Mg handling, especially in distal convoluted tubule (DCT), the segment responsible for final regulation of Mg balance. By considering effects of Na,K-ATPase on intracellular Na and K concentrations, and driving forces for Mg transport, we propose a consistent rationale explaining basal Mg reabsorption in DCT and altered Mg reabsorption in some human diseases. FXYD2 (γ subunit) is a regulatory subunit that adapts functional properties of Na,K-ATPase to cellular requirements. Mutations in FXYD2 (G41R), and transcription factors (HNF-1B and PCBD1) that affect FXYD2 expression are associated with hypomagnesemia with hypermagnesuria. These mutations result in impaired interactions of FXYD2 with Na,K-ATPase. Renal Mg wasting implies that Na,K-ATPase is inhibited, but in vitro studies show that FXYD2 itself inhibits Na,K-ATPase activity, raising K0.5 Na. However, FXYD2 also stabilizes the protein by amplifying specific interactions with phosphatidylserine and cholesterol within the membrane. Renal Mg wasting associated with impaired Na,K-ATPase/FXYD2 interactions is explained simply by destabilization and inactivation of Na,K-ATPase. We consider also the role of the Na,K-ATPase in Mg (and Ca) handling in Gitelman syndrome and Familial hyperkalemia and hypertension (FHHt). Renal Mg handling serves as a convenient marker for Na,K-ATPase activity in DCT.
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Affiliation(s)
- Haim Mayan
- Department of Medicine ESheba Medical CenterRamat GanIsrael
- Laboratory of Biochemical PharmacologySheba Medical CenterRamat GanIsrael
- Sackler School of MedicineTel Aviv UniversityTel AvivIsrael
| | - Zvi Farfel
- Department of Medicine ESheba Medical CenterRamat GanIsrael
- Laboratory of Biochemical PharmacologySheba Medical CenterRamat GanIsrael
- Sackler School of MedicineTel Aviv UniversityTel AvivIsrael
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovothIsrael
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9
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Ventéo S, Laffray S, Wetzel C, Rivat C, Scamps F, Méchaly I, Bauchet L, Raoul C, Bourinet E, Lewin GR, Carroll P, Pattyn A. Fxyd2 regulates Aδ- and C-fiber mechanosensitivity and is required for the maintenance of neuropathic pain. Sci Rep 2016; 6:36407. [PMID: 27805035 PMCID: PMC5090990 DOI: 10.1038/srep36407] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 10/12/2016] [Indexed: 01/24/2023] Open
Abstract
Identification of the molecular mechanisms governing sensory neuron subtype excitability is a key requisite for the development of treatments for somatic sensory disorders. Here, we show that the Na,K-ATPase modulator Fxyd2 is specifically required for setting the mechanosensitivity of Aδ-fiber low-threshold mechanoreceptors and sub-populations of C-fiber nociceptors, a role consistent with its restricted expression profile in the spinal somatosensory system. We also establish using the spared nerve injury model of neuropathic pain, that loss of Fxyd2 function, either constitutively in Fxyd2−/− mice or acutely in neuropathic rats, efficiently alleviates mechanical hypersensitivity induced by peripheral nerve lesions. The role of Fxyd2 in modulating Aδ- and C-fibers mechanosensitivity likely accounts for the anti-allodynic effect of Fxyd2 knockdown. Finally, we uncover the evolutionarily conserved restricted expression pattern of FXYD2 in human dorsal root ganglia, thus identifying this molecule as a potentially promising therapeutic target for peripheral neuropathic pain management.
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Affiliation(s)
- Stéphanie Ventéo
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Sophie Laffray
- UMR5203, INSERM U1191, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France.,Université de Montpellier, Place Eugène Bataillon, 34090 Montpellier, France
| | - Christiane Wetzel
- Department of Neuroscience, Max-Delbrück Center for Molecular Medicine, Robert-Rössle Str. 10, D-13125 Berlin, Germany
| | - Cyril Rivat
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France.,Université de Montpellier, Place Eugène Bataillon, 34090 Montpellier, France
| | - Frédérique Scamps
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Ilana Méchaly
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France.,Université de Montpellier, Place Eugène Bataillon, 34090 Montpellier, France
| | - Luc Bauchet
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France.,Département de Neurochirurgie, Hôpital Gui de Chauliac, CHU, 80 avenue Augustin Fliche, 34295 Montpellier, France
| | - Cédric Raoul
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Emmanuel Bourinet
- UMR5203, INSERM U1191, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France
| | - Gary R Lewin
- Department of Neuroscience, Max-Delbrück Center for Molecular Medicine, Robert-Rössle Str. 10, D-13125 Berlin, Germany
| | - Patrick Carroll
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France
| | - Alexandre Pattyn
- INSERM U1051, Institut des Neurosciences de Montpellier, Hôpital St Eloi, 80 rue Augustin Fliche, 34091 Montpellier, France
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10
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Segerstolpe Å, Palasantza A, Eliasson P, Andersson EM, Andréasson AC, Sun X, Picelli S, Sabirsh A, Clausen M, Bjursell MK, Smith DM, Kasper M, Ämmälä C, Sandberg R. Single-Cell Transcriptome Profiling of Human Pancreatic Islets in Health and Type 2 Diabetes. Cell Metab 2016; 24:593-607. [PMID: 27667667 PMCID: PMC5069352 DOI: 10.1016/j.cmet.2016.08.020] [Citation(s) in RCA: 944] [Impact Index Per Article: 118.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 06/13/2016] [Accepted: 08/26/2016] [Indexed: 12/25/2022]
Abstract
Hormone-secreting cells within pancreatic islets of Langerhans play important roles in metabolic homeostasis and disease. However, their transcriptional characterization is still incomplete. Here, we sequenced the transcriptomes of thousands of human islet cells from healthy and type 2 diabetic donors. We could define specific genetic programs for each individual endocrine and exocrine cell type, even for rare δ, γ, ε, and stellate cells, and revealed subpopulations of α, β, and acinar cells. Intriguingly, δ cells expressed several important receptors, indicating an unrecognized importance of these cells in integrating paracrine and systemic metabolic signals. Genes previously associated with obesity or diabetes were found to correlate with BMI. Finally, comparing healthy and T2D transcriptomes in a cell-type resolved manner uncovered candidates for future functional studies. Altogether, our analyses demonstrate the utility of the generated single-cell gene expression resource.
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Affiliation(s)
- Åsa Segerstolpe
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, 171 77 Stockholm, Sweden; Integrated Cardio Metabolic Center (ICMC), Karolinska Institutet, 141 57 Huddinge, Sweden
| | - Athanasia Palasantza
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Pernilla Eliasson
- Cardiovascular and Metabolic Diseases (CVMD), Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | - Eva-Marie Andersson
- Cardiovascular and Metabolic Diseases (CVMD), Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | - Anne-Christine Andréasson
- Cardiovascular and Metabolic Diseases (CVMD), Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | - Xiaoyan Sun
- Department of Biosciences and Nutrition and Center for Innovative Medicine, Novum, Karolinska Institutet, 141 83 Huddinge, Sweden
| | - Simone Picelli
- Ludwig Institute for Cancer Research, 171 77 Stockholm, Sweden
| | - Alan Sabirsh
- Cardiovascular and Metabolic Diseases (CVMD), Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | - Maryam Clausen
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | | | - David M Smith
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, Cambridge Science Park, Milton Road, Cambridge CB4 0WG, UK
| | - Maria Kasper
- Department of Biosciences and Nutrition and Center for Innovative Medicine, Novum, Karolinska Institutet, 141 83 Huddinge, Sweden
| | - Carina Ämmälä
- Cardiovascular and Metabolic Diseases (CVMD), Innovative Medicines and Early Development Biotech Unit (iMed), AstraZeneca, 431 83 Mölndal, Sweden
| | - Rickard Sandberg
- Department of Cell and Molecular Biology (CMB), Karolinska Institutet, 171 77 Stockholm, Sweden; Integrated Cardio Metabolic Center (ICMC), Karolinska Institutet, 141 57 Huddinge, Sweden; Ludwig Institute for Cancer Research, 171 77 Stockholm, Sweden.
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11
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Froehlich JW, Kostel SA, Cho PS, Briscoe AC, Steen H, Vaezzadeh AR, Lee RS. Urinary Proteomics Yield Pathological Insights for Ureteropelvic Junction Obstruction. Mol Cell Proteomics 2016; 15:2607-15. [PMID: 27215552 DOI: 10.1074/mcp.m116.059386] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 01/14/2023] Open
Abstract
Prenatal hydronephrosis is a common condition that may spontaneously resolve after birth. However, this condition can result in renal damage and requires surgical correction in a number of cases. Preventing renal damage is paramount, but existing diagnostic technology is invasive, exposes infants to radiation, is costly, and is often indeterminate. A better understanding of the pathophysiology of renal obstruction as reflected in the urinary proteome may provide new insights into the disease that could potentially alter the clinical management of hydronephrosis. We performed a quantitative proteomics study of urine that was surgically obtained from eight clinically significant, unilaterally obstructed infants versus eight healthy controls, with the goal of identifying quantitatively varying proteins and the biological networks associated with them. Notably, urine was obtained from both the obstructed kidney and the bladder. Over 1100 proteins were identified, and a total of 76 quantitatively varying proteins were identified. Proteins involved in oxidative stress, inflammation, and renal disease pathways showed the most significant abundance differences. This study gives a deeper understanding of the critical proteomic changes associated with renal obstruction and represents the deepest proteomic profile of renal obstruction to date.
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Affiliation(s)
- John W Froehlich
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
| | - Stephen A Kostel
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
| | - Patricia S Cho
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
| | - Andrew C Briscoe
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
| | - Hanno Steen
- §Proteomics Center at Children's Hospital Boston, Boston, MA ¶Department of Pathology, Children's Hospital Boston and Harvard Medical School, Boston, MA
| | - Ali R Vaezzadeh
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
| | - Richard S Lee
- From the ‡Department of Urology and the Urological Diseases Research Center, §Proteomics Center at Children's Hospital Boston, Boston, MA
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12
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Arystarkhova E. Beneficial Renal and Pancreatic Phenotypes in a Mouse Deficient in FXYD2 Regulatory Subunit of Na,K-ATPase. Front Physiol 2016; 7:88. [PMID: 27014088 PMCID: PMC4779850 DOI: 10.3389/fphys.2016.00088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 02/22/2016] [Indexed: 11/25/2022] Open
Abstract
The fundamental role of Na,K-ATPase in eukaryotic cells calls for complex and efficient regulation of its activity. Besides alterations in gene expression and trafficking, kinetic properties of the pump are modulated by reversible association with single span membrane proteins, the FXYDs. Seven members of the family are expressed in a tissue-specific manner, affecting pump kinetics in all possible permutations. This mini-review focuses on functional properties of FXYD2 studied in transfected cells, and on noteworthy and unexpected phenotypes discovered in a Fxyd2−∕− mouse. FXYD2, the gamma subunit, reduces activity of Na,K-ATPase either by decreasing affinity for Na+, or reducing Vmax. FXYD2 mRNA splicing and editing provide another layer for regulation of Na,K-ATPase. In kidney of knockouts, there was elevated activity for Na,K-ATPase and for NCC and NKCC2 apical sodium transporters. That should lead to sodium retention and hypertension, however, the mice were in sodium balance and normotensive. Adult Fxyd2−∕− mice also exhibited a mild pancreatic phenotype with enhanced glucose tolerance, elevation of circulating insulin, but no insulin resistance. There was an increase in beta cell proliferation and beta cell mass that correlated with activation of the PI3K-Akt pathway. The Fxyd2−∕− mice are thus in a highly desirable state: the animals are resistant to Na+ retention, and showed improved glucose control, i.e., they display favorable metabolic adaptations to protect against development of salt-sensitive hypertension and diabetes. Investigation of the mechanisms of these adaptations in the mouse has the potential to unveil a novel therapeutic FXYD2-dependent strategy.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Neurosurgery, Massachusetts General Hospital Boston, MA, USA
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13
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Rauhala L, Hämäläinen L, Dunlop TW, Pehkonen P, Bart G, Kokkonen M, Tammi M, Tammi R, Pasonen-Seppänen S. The organic osmolyte betaine induces keratin 2 expression in rat epidermal keratinocytes — A genome-wide study in UVB irradiated organotypic 3D cultures. Toxicol In Vitro 2015; 30:462-75. [DOI: 10.1016/j.tiv.2015.09.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 09/01/2015] [Accepted: 09/12/2015] [Indexed: 12/18/2022]
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14
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Arystarkhova E, Ralph DL, Liu YB, Bouley R, McDonough AA, Sweadner KJ. Paradoxical activation of the sodium chloride cotransporter (NCC) without hypertension in kidney deficient in a regulatory subunit of Na,K-ATPase, FXYD2. Physiol Rep 2014; 2:2/12/e12226. [PMID: 25472608 PMCID: PMC4332208 DOI: 10.14814/phy2.12226] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Na,K‐ATPase generates the driving force for sodium reabsorption in the kidney.
Na,K‐ATPase functional properties are regulated by small proteins belonging to the FXYD
family. In kidney FXYD2 is the most abundant: it is an inhibitory subunit expressed in almost every
nephron segment. Its absence should increase sodium pump activity and promote Na+
retention, however, no obvious renal phenotype was detected in mice with global deletion of FXYD2
(Arystarkhova et al. 2013). Here, increased total cortical Na,K‐ATPase activity was
documented in the Fxyd2−/− mouse, without increased
α1β1 subunit expression. We tested the hypothesis
that adaptations occur in distal convoluted tubule (DCT), a major site of sodium adjustments.
Na,K‐ATPase immunoreactivity in DCT was unchanged, and there was no DCT hypoplasia. There was
a marked activation of thiazide‐sensitive sodium chloride cotransporter (NCC; Slc12a3) in
DCT, predicted to increase Na+ reabsorption in this segment. Specifically, NCC
total increased 30% and NCC phosphorylated at T53 and S71, associated with activation,
increased 4‐6 fold. The phosphorylation of the closely related thick ascending limb (TAL)
apical NKCC2 (Slc12a1) increased at least twofold. Abundance of the total and cleaved (activated)
forms of ENaC α‐subunit was not different between genotypes.
Nonetheless, no elevation of blood pressure was evident despite the fact that NCC and NKCC2 are in
states permissive for Na+ retention. Activation of NCC and NKCC2 may reflect an
intracellular linkage to elevated Na,K‐ATPase activity or a compensatory response to
Na+ loss proximal to the TAL and DCT. We discovered a substantial activation of renal NCC cotransporter in mice genetically depleted
for the regulatory inhibitory subunit of Na,K‐ATPase, FXYD2. Surprisingly, no significant
changes in urine output as well as elevation of blood pressure were detected suggesting compensatory
adaptation elsewhere in nephron
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Massachusetts General Hospital, Boston, Massachusetts
| | - Donna L Ralph
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Yi Bessie Liu
- Laboratory of Membrane Biology, Massachusetts General Hospital, Boston, Massachusetts
| | - Richard Bouley
- MGH Center for Systems Biology, Program in Membrane Biology, Massachusetts General Hospital, Boston, Massachusetts
| | - Alicia A McDonough
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Kathleen J Sweadner
- Laboratory of Membrane Biology, Massachusetts General Hospital, Boston, Massachusetts
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15
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FXYD2c Plays a Potential Role in Modulating Na+/K+-ATPase Activity in HK-2 Cells Upon Hypertonic Challenge. J Membr Biol 2013; 247:93-105. [DOI: 10.1007/s00232-013-9615-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 11/08/2013] [Indexed: 01/07/2023]
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16
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Arystarkhova E, Liu YB, Salazar C, Stanojevic V, Clifford RJ, Kaplan JH, Kidder GM, Sweadner KJ. Hyperplasia of pancreatic beta cells and improved glucose tolerance in mice deficient in the FXYD2 subunit of Na,K-ATPase. J Biol Chem 2013; 288:7077-85. [PMID: 23344951 DOI: 10.1074/jbc.m112.401190] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Restoration of the functional potency of pancreatic islets either through enhanced proliferation (hyperplasia) or increase in size (hypertrophy) of beta cells is a major objective for intervention in diabetes. We have obtained experimental evidence that global knock-out of a small, single-span regulatory subunit of Na,K-ATPase, FXYD2, alters glucose control. Adult Fxyd2(-/-) mice showed significantly lower blood glucose levels, no signs of peripheral insulin resistance, and improved glucose tolerance compared with their littermate controls. Strikingly, there was a substantial hyperplasia in pancreatic beta cells from the Fxyd2(-/-) mice compared with the wild type littermates, compatible with an observed increase in the level of circulating insulin. No changes were seen in the exocrine compartment of the pancreas, and the mice had only a mild, well-adapted renal phenotype. Morphometric analysis revealed an increase in beta cell mass in KO compared with WT mice. This appears to explain a phenotype of hyperinsulinemia. By RT-PCR, Western blot, and immunocytochemistry we showed the FXYD2b splice variant in pancreatic beta cells from wild type mice. Phosphorylation of Akt kinase was significantly higher under basal conditions in freshly isolated islets from Fxyd2(-/-) mice compared with their WT littermates. Inducible expression of FXYD2 in INS 832/13 cells produced a reduction in the phosphorylation level of Akt, and phosphorylation was restored in parallel with degradation of FXYD2. Thus we suggest that in pancreatic beta cells FXYD2 plays a role in Akt signaling pathways associated with cell growth and proliferation.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory Membrane Biology, Massachusetts General Hospital, Boston, Massachusetts 2114, USA.
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17
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Identification of a crab gill FXYD2 protein and regulation of crab microsomal Na,K-ATPase activity by mammalian FXYD2 peptide. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2588-97. [DOI: 10.1016/j.bbamem.2012.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 05/07/2012] [Accepted: 05/08/2012] [Indexed: 01/20/2023]
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18
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Li X, McClellan ME, Tanito M, Garteiser P, Towner R, Bissig D, Berkowitz BA, Fliesler SJ, Woodruff ML, Fain GL, Birch DG, Khan MS, Ash JD, Elliott MH. Loss of caveolin-1 impairs retinal function due to disturbance of subretinal microenvironment. J Biol Chem 2012; 287:16424-34. [PMID: 22451674 DOI: 10.1074/jbc.m112.353763] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Caveolin-1 (Cav-1), an integral component of caveolar membrane domains, is expressed in several retinal cell types, including photoreceptors, retinal vascular endothelial cells, Müller glia, and retinal pigment epithelium (RPE) cells. Recent evidence links Cav-1 to ocular diseases, including autoimmune uveitis, diabetic retinopathy, and primary open angle glaucoma, but its role in normal vision is largely undetermined. In this report, we show that ablation of Cav-1 results in reduced inner and outer retinal function as measured, in vivo, by electroretinography and manganese-enhanced MRI. Somewhat surprisingly, dark current and light sensitivity were normal in individual rods (recorded with suction electrode methods) from Cav-1 knock-out (KO) mice. Although photoreceptor function was largely normal, in vitro, the apparent K(+) affinity of the RPE-expressed α1-Na(+)/K(+)-ATPase was decreased in Cav-1 KO mice. Cav-1 KO retinas also displayed unusually tight adhesion with the RPE, which could be resolved by brief treatment with hyperosmotic medium, suggesting alterations in outer retinal fluid homeostasis. Collectively, these findings demonstrate that reduced retinal function resulting from Cav-1 ablation is not photoreceptor-intrinsic but rather involves impaired subretinal and/or RPE ion/fluid homeostasis.
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Affiliation(s)
- Xiaoman Li
- Department of Ophthalmology and Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA
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19
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Gopalani NK, Meena RN, Prasad DN, Ilavazhagan G, Sharma M. Cooperativity between inhibition of cytosolic K+ efflux and AMPK activation during suppression of hypoxia-induced cellular apoptosis. Int J Biochem Cell Biol 2011; 44:211-23. [PMID: 22064248 DOI: 10.1016/j.biocel.2011.10.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 10/13/2011] [Accepted: 10/25/2011] [Indexed: 02/05/2023]
Abstract
Cellular potassium homeostasis has recently emerged as a critical regulator of apoptosis in response to variety of stimuli. However, functional hierarchy of this phenomenon in the apoptotic cascade and therefore, its significance as a pathway for intervention is not fully established. Chronic hypoxia, a known threat to cell survival, also modulates cellular potassium homeostasis. In this study, we tested if hypoxia-induced apoptosis in lymphocytes can be prevented by modulating cellular K+ homeostasis. We observed that chronic hypoxia accelerated the rate of apoptosis in resting murine splenocytes concomitant with cytosolic K+ efflux. We tested several modalities including elevated extracellular potassium besides various K+ channel inhibitors to curtail hypoxia-induced K+ efflux and interestingly, established that the supplementation of KCl in extracellular medium was most effective in preventing hypoxia-induced apoptosis in these cells. Subsequent mechanistic dissection of pathways underlying this phenomenon revealed that besides effectively inhibiting hypoxia-induced efflux of K+ ion and its downstream cell-physiological consequences; elevated extracellular KCl modulated steady state levels of cellular ATP and culminated in stabilization of AMPKα with pro-survival consequences. Also, interestingly, global gene expression profiling revealed that KCl supplementation down regulated a distinct p53-regulated cellular sub-network of genes involved in regulation of DNA replication. Additionally, we present experimental evidence for the functional role of AMPK and p53 activation during suppression of hypoxia-induced apoptosis. In conclusion, our study highlights a novel bimodal effect wherein cooperativity between restoration of K+ homeostasis and a sustainable 'metabolic quiescence' induced by AMPK activation appeared indispensible for curtailing hypoxia-induced apoptosis.
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Affiliation(s)
- Nomesh K Gopalani
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences (DIPAS), DRDO, Delhi, India
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20
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Desforges B, Savarin P, Bounedjah O, Delga S, Hamon L, Curmi PA, Pastré D. Gap junctions favor normal rat kidney epithelial cell adaptation to chronic hypertonicity. Am J Physiol Cell Physiol 2011; 301:C705-16. [PMID: 21677260 DOI: 10.1152/ajpcell.00128.2011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Upon hypertonic stress most often resulting from high salinity, cells need to balance their osmotic pressure by accumulating neutral osmolytes called compatible osmolytes like betaine, myo-inositol, and taurine. However, the massive uptake of compatible osmolytes is a slow process compared with other defense mechanisms related to oxidative or heat stress. This is especially critical for cycling cells as they have to double their volume while keeping a hospitable intracellular environment for the molecular machineries. Here we propose that clustered cells can accelerate the supply of compatible osmolytes to cycling cells via the transit, mediated by gap junctions, of compatible osmolytes from arrested to cycling cells. Both experimental results in epithelial normal rat kidney cells and theoretical estimations show that gap junctions indeed play a key role in cell adaptation to chronic hypertonicity. These results can provide basis for a better understanding of the functions of gap junctions in osmoregulation not only for the kidney but also for many other epithelia. In addition to this, we suggest that cancer cells that do not communicate via gap junctions poorly cope with hypertonic environments thus explaining the rare occurrence of cancer coming from the kidney medulla.
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Affiliation(s)
- Bénédicte Desforges
- Laboratoire Structure-Activité des Biomolécules Normales et Pathologiques, Institut National de la Santé et de la Recherche Médicale U, Université Evry-Val d’Essonne, France
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21
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Sweadner KJ, Pascoa JL, Salazar CA, Arystarkhova E. Post-transcriptional control of Na,K-ATPase activity and cell growth by a splice variant of FXYD2 protein with modified mRNA. J Biol Chem 2011; 286:18290-300. [PMID: 21460224 DOI: 10.1074/jbc.m111.241901] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In kidney, FXYD proteins regulate Na,K-ATPase in a nephron segment-specific way. FXYD2 is the most abundant renal FXYD but is not expressed in most renal cell lines unless induced by hypertonicity. Expression by transfection of FXYD2a or FXYD2b splice variants in NRK-52E cells reduces the apparent Na(+) affinity of the Na,K-ATPase and slows the cell proliferation rate. Based on RT-PCR, mRNAs for both splice variants were expressed in wild type NRK-52E cells as low abundance species. DNA sequencing of the PCR products revealed a base alteration from C to T in FXYD2b but not FXYD2a from both untreated and hypertonicity-treated NRK-52E cells. The 172C→T sequence change exposed a cryptic KKXX endoplasmic reticulum retrieval signal via a premature stop codon. The truncation affected trafficking of FXYD2b and its association with Na,K-ATPase and blocked its effect on enzyme kinetics and cell growth. The data may be explained by altered splicing or selective RNA editing of FXYD2b, a supplementary process that would ensure that it was inactive even if transcribed and translated, in these cells that normally express only FXYD2a. 172C→T mutation was also identified after mutagenesis of FXYD2b by error-prone PCR coupled with a selection for cell proliferation. Furthermore, the error-prone PCR alone introduced the mutation with high frequency, implying a structural peculiarity. The data confirm truncation of FXYD2b as a potential mechanism to regulate the amount of FXYD2 at the cell surface to control activity of Na,K-ATPase and cell growth.
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Affiliation(s)
- Kathleen J Sweadner
- Laboratory of Membrane Biology, Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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22
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Mishra NK, Peleg Y, Cirri E, Belogus T, Lifshitz Y, Voelker DR, Apell HJ, Garty H, Karlish SJD. FXYD proteins stabilize Na,K-ATPase: amplification of specific phosphatidylserine-protein interactions. J Biol Chem 2011; 286:9699-712. [PMID: 21228272 DOI: 10.1074/jbc.m110.184234] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
FXYD proteins are a family of seven small regulatory proteins, expressed in a tissue-specific manner, that associate with Na,K-ATPase as subsidiary subunits and modulate kinetic properties. This study describes an additional property of FXYD proteins as stabilizers of Na,K-ATPase. FXYD1 (phospholemman), FXYD2 (γ subunit), and FXYD4 (CHIF) have been expressed in Escherichia coli and purified. These FXYD proteins associate spontaneously in vitro with detergent-soluble purified recombinant human Na,K-ATPase (α1β1) to form α1β1FXYD complexes. Compared with the control (α1β1), all three FXYD proteins strongly protect Na,K-ATPase activity against inactivation by heating or excess detergent (C(12)E(8)), with effectiveness FXYD1 > FXYD2 ≥ FXYD4. Heating also inactivates E(1) ↔ E(2) conformational changes and cation occlusion, and FXYD1 protects strongly. Incubation of α1β1 or α1β1FXYD complexes with guanidinium chloride (up to 6 m) causes protein unfolding, detected by changes in protein fluorescence, but FXYD proteins do not protect. Thus, general protein denaturation is not the cause of thermally mediated or detergent-mediated inactivation. By contrast, the experiments show that displacement of specifically bound phosphatidylserine is the primary cause of thermally mediated or detergent-mediated inactivation, and FXYD proteins stabilize phosphatidylserine-Na,K-ATPase interactions. Phosphatidylserine probably binds near trans-membrane segments M9 of the α subunit and the FXYD protein, which are in proximity. FXYD1, FXYD2, and FXYD4 co-expressed in HeLa cells with rat α1 protect strongly against thermal inactivation. Stabilization of Na,K-ATPase by three FXYD proteins in a mammalian cell membrane, as well the purified recombinant Na,K-ATPase, suggests that stabilization is a general property of FXYD proteins, consistent with a significant biological function.
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Affiliation(s)
- Neeraj Kumar Mishra
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovoth 76100, Israel
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23
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Hutton JC, Davidson HW. Getting beta all the time: discovery of reliable markers of beta cell mass. Diabetologia 2010; 53:1254-7. [PMID: 20411233 DOI: 10.1007/s00125-010-1762-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 03/26/2010] [Indexed: 10/19/2022]
Affiliation(s)
- J C Hutton
- Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Mail Stop B140, 1775 Aurora Court, Aurora, CO, 80045, USA.
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24
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Flamez D, Roland I, Berton A, Kutlu B, Dufrane D, Beckers MC, De Waele E, Rooman I, Bouwens L, Clark A, Lonneux M, Jamar JF, Goldman S, Maréchal D, Goodman N, Gianello P, Van Huffel C, Salmon I, Eizirik DL. A genomic-based approach identifies FXYD domain containing ion transport regulator 2 (FXYD2)gammaa as a pancreatic beta cell-specific biomarker. Diabetologia 2010; 53:1372-83. [PMID: 20379810 DOI: 10.1007/s00125-010-1714-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 01/13/2010] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Non-invasive imaging of the pancreatic beta cell mass (BCM) requires the identification of novel and specific beta cell biomarkers. We have developed a systems biology approach to the identification of promising beta cell markers. METHODS We followed a functional genomics strategy based on massive parallel signal sequencing (MPSS) and microarray data obtained in human islets, purified primary rat beta cells, non-beta cells and INS-1E cells to identify promising beta cell markers. Candidate biomarkers were validated and screened using established human and macaque (Macacus cynomolgus) tissue microarrays. RESULTS After a series of filtering steps, 12 beta cell-specific membrane proteins were identified. For four of the proteins we selected or produced antibodies targeting specifically the human proteins and their splice variants; all four candidates were confirmed as islet-specific in human pancreas. Two splice variants of FXYD domain containing ion transport regulator 2 (FXYD2), a regulating subunit of the Na(+)-K(+)-ATPase, were identified as preferentially present in human pancreatic islets. The presence of FXYD2gammaa was restricted to pancreatic islets and selectively detected in pancreatic beta cells. Analysis of human fetal pancreas samples showed the presence of FXYD2gammaa at an early stage (15 weeks). Histological examination of pancreatic sections from individuals with type 1 diabetes or sections from pancreases of streptozotocin-treated Macacus cynomolgus monkeys indicated a close correlation between loss of FXYD2gammaa and loss of insulin-positive cells. CONCLUSIONS/INTERPRETATION We propose human FXYD2gammaa as a novel beta cell-specific biomarker.
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Affiliation(s)
- D Flamez
- Laboratory of Experimental Medicine, Université Libre de Bruxelles, Route de Lennik 808, 1070, Brussels, Belgium.
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25
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Lingrel JB. The physiological significance of the cardiotonic steroid/ouabain-binding site of the Na,K-ATPase. Annu Rev Physiol 2010; 72:395-412. [PMID: 20148682 DOI: 10.1146/annurev-physiol-021909-135725] [Citation(s) in RCA: 225] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Na,K-ATPase is the membrane "pump" that generates the Na(+) and K(+) gradients across the plasma membrane that drives many physiological processes. This enzyme is highly sensitive to inhibition by cardiotonic steroids, most notably the digitalis/ouabain class of compounds, which have been used for centuries to treat congestive heart failure and arrhythmias. The amino acids that constitute the ouabain-binding site are highly conserved across the evolutionary spectrum. This could be fortuitous or could result from this site being conserved because it has an important biological function. New physiological approaches using genetically engineered mice are being used to define the biological significance of the "receptor function" of the Na,K-ATPase and its regulation by potential endogenous cardiotonic steroid-like compounds. These studies extend the reach of earlier studies involving the biochemical purification of endogenous regulatory ligands.
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Affiliation(s)
- Jerry B Lingrel
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0524, USA.
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26
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Cairo ER, Swarts HGP, Wilmer MJG, Willems PHGM, Levtchenko EN, De Pont JJHHM, Koenderink JB. FXYD2 and Na,K-ATPase expression in isolated human proximal tubular cells: disturbed upregulation on renal hypomagnesemia? J Membr Biol 2009; 231:117-24. [PMID: 19865785 PMCID: PMC2776943 DOI: 10.1007/s00232-009-9210-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 10/08/2009] [Indexed: 11/05/2022]
Abstract
Autosomal dominant renal hypomagnesemia (OMIM 154020), associated with hypocalciuria, has been linked to a 121G to A mutation in the FXYD2 gene. To gain insight into the molecular mechanisms linking this mutation to the clinical phenotype, we studied isolated proximal tubular cells from urine of a patient and a healthy subject. Cells were immortalized and used to assess the effects of hypertonicity-induced overexpression of FXYD2 on amount, activity and apparent affinities for Na+, K+ and ATP of Na,K-ATPase. Both cell lines expressed mRNA for FXYD2a and FXYD2b, and patient cells contained both the wild-type and mutated codons. FXYD2 protein expression was lower in patient cells and could be increased in both cell lines upon culturing in hyperosmotic medium but to a lesser extent in patient cells. Similarly, hyperosmotic culturing increased Na,K-ATPase protein expression and ATP hydrolyzing activity but, again, to a lesser extent in patient cells. Apparent affinities of Na,K-ATPase for Na+, K+ and ATP did not differ between patient and control cells or after hyperosmotic induction. We conclude that human proximal tubular cells respond to a hyperosmotic challenge with an increase in FXYD2 and Na,K-ATPase protein expression, though to a smaller absolute extent in patient cells.
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Affiliation(s)
- Edinio R Cairo
- Department of Biochemistry, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Kobayashi H, Yamada Y, Kanayama S, Furukawa N, Noguchi T, Haruta S, Yoshida S, Sakata M, Sado T, Oi H. The role of hepatocyte nuclear factor-1beta in the pathogenesis of clear cell carcinoma of the ovary. Int J Gynecol Cancer 2009; 19:471-9. [PMID: 19407577 DOI: 10.1111/igc.0b013e3181a19eca] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
PROBLEM Clear cell carcinoma (CCC) of the ovary has a number of features distinguishing it from other epithelial ovarian carcinomas (EOC) because of its characteristic histology and biology, frequent concurrence with endometriotic lesion, and highly chemoresistant nature resulting in an extremely poor prognosis. The incidence of CCC has been steadily increasing in Japan. They comprise approximately 20% of all EOC. Understanding the mechanisms of CCC development and elucidating pathogenesis and pathophysiology are intrinsic to prevention and effective therapies for CCC. METHOD OF STUDY This article reviews the English language literature for biology, pathogenesis, and pathophysiological studies on endometriosis-associated EOC. Several data are discussed in the context of endometriosis and CCC biology. RESULTS Recent studies based on genome-wide expression analysis technology have noted specific expression of hepatocyte nuclear factor-1beta (HNF-1beta) in endometriosis and CCC, suggesting that early differentiation into the clear cell lineage takes place in the endometriosis. The HNF-1beta-dependent pathway of CCC will be discussed, which are providing new insights into regulation of apoptosis and glycogen synthesis and resistance of CCC to anticancer agents. CONCLUSIONS This review summarizes recent advances in the HNF-1beta and its target genes; the potential challenges to the understanding of carcinogenesis, pathogenesis, and pathophysiology of CCC; and a possible novel model is proposed.
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Affiliation(s)
- Hiroshi Kobayashi
- Department of Obstetrics and Gynecology, Nara Medical University, Japan.
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28
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Zhu H, Zhang L, Amin AR, Li Y. Coordinated upregulation of a series of endogenous antioxidants and phase 2 enzymes as a novel strategy for protecting renal tubular cells from oxidative and electrophilic stress. Exp Biol Med (Maywood) 2008; 233:753-65. [PMID: 18408143 DOI: 10.3181/0801-rm-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In view of the crucial involvement of oxidative and electrophilic stress in various kidney disorders, this study was undertaken to test the hypothesis that pharmacologically-mediated coordinated upregulation of endogenous renal antioxidants and phase 2 enzymes is an effective strategy for renal protection. Notably, studies on the pharmacological inducibility of a series of antioxidants and phase 2 enzymes in renal tubular cells are lacking. Here we reported that incubation of normal rat kidney (NRK-52E) proximal tubular cells with low micromolar concentrations (10-50 microM) of the cruciferous nutraceutical, 1,2-dithiole-3-thione (D3T), led to a significant concentration-dependent induction of a wide spectrum of antioxidants and phase 2 enzymes, including catalase (CAT), reduced form of glutathione (GSH), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), NAD(P)H:quinone oxidoreductase 1 (NQO1), and heme oxygenase (HO). We further observed that D3T treatment also increased the protein and mRNA expression for CAT, gamma-glutamylcysteine ligase, GR, GST-A, GST-M, NQO1, and HO-1. Incubation of the renal tubular cells with H(2)O(2), SIN-1-derived peroxynitrite, or 4-hydroxy-2-nonenal led to concentration-dependent decreases in cell viability. Pretreatment of the renal tubular cells with 10-50 microM D3T afforded remarkable protection against the nephrocytotoxicity elicited by the above oxidative and electrophilic species. The D3T-mediated cytoprotection showed a concentration-dependent relationship. Taken together, this study for the first time comprehensively characterized the inducibility by a unique nutraceutical of a wide spectrum of antioxidative and phase 2 defenses in renal tubular cells at the levels of enzyme activity as well as protein and mRNA expression, and demonstrated that such a coordinated upregulation of cellular defenses led to remarkable protection of renal tubular cell from oxidative and electrophilic stress. Because of the crucial role of oxidative and electrophilic stress in inflammatory injury, D3T-mediated coordinated induction of endogenous antioxidative and phase 2 defenses may also serve as an important anti-inflammatory mechanism in kidneys.
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Affiliation(s)
- Hong Zhu
- Division of Biomedical Sciences, Edward Via Virginia College of Osteopathic Medicine, Virginia Tech Corporate Research Center, Blacksburg, Virginia 24060, USA
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29
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Arystarkhova E, Donnet C, Muñoz-Matta A, Specht SC, Sweadner KJ. Multiplicity of expression of FXYD proteins in mammalian cells: dynamic exchange of phospholemman and gamma-subunit in response to stress. Am J Physiol Cell Physiol 2006; 292:C1179-91. [PMID: 17050615 DOI: 10.1152/ajpcell.00328.2006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functional properties of Na-K-ATPase can be modified by association with FXYD proteins, expressed in a tissue-specific manner. Here we show that expression of FXYDs in cell lines does not necessarily parallel the expression pattern of FXYDs in the tissue(s) from which the cells originate. While being expressed only in lacis cells in the juxtaglomerular apparatus and in blood vessels in kidney, FXYD1 was abundant in renal cell lines of proximal tubule origin (NRK-52E, LLC-PK1, and OK cells). Authenticity of FXYD1 as a part of Na-K-ATPase in NRK-52E cells was demonstrated by co-purification, co-immunoprecipitation, and co-localization. Induction of FXYD2 by hypertonicity (500 mosmol/kgH(2)O with NaCl for 48 h or adaptation to 700 mosmol/kgH(2)O) correlated with downregulation of FXYD1 at mRNA and protein levels. The response to hypertonicity was influenced by serum factors and entailed, first, dephosphorylation of FXYD1 at Ser(68) (1-5 h) and, second, induction of FXYD2a and a decrease in FXYD1 with longer exposure. FXYD1 was completely replaced with FXYD2a in cells adapted to 700 mosmol/kgH(2)O and showed a significantly decreased sodium affinity. Thus dephosphorylation of FXYD1 followed by exchange of regulatory subunits is utilized to make a smooth transition of properties of Na-K-ATPase. We also observed expression of mRNA for multiple FXYDs in various cell lines. The expression was dynamic and responsive to physiological stimuli. Moreover, we demonstrated expression of FXYD5 protein in HEK-293 and HeLa cells. The data imply that FXYDs are obligatory rather than auxiliary components of Na-K-ATPase, and their interchangeability underlies responses of Na-K-ATPase to cellular stress.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Massachusetts General Hospital, Boston, MA 02114, USA.
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30
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Capasso JM, Rivard CJ, Berl T. Silencing and overexpression of the gamma-subunit of Na-K-ATPase directly affect survival of IMCD3 cells in response to hypertonic stress. Am J Physiol Renal Physiol 2006; 291:F1142-7. [PMID: 16804105 DOI: 10.1152/ajprenal.00077.2006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gamma-subunit of Na-K-ATPase is robustly expressed in inner medullary collecting duct (IMCD)3 cells either acutely challenged or adapted to hypertonicity but not under isotonic conditions. Circumstantial evidence suggests that this protein may be important for the survival of renal cells in a hypertonic environment. However, no direct proof for such a contention has been forthcoming. The complete mRNA sequences of either gamma-subunit isoforms were spliced into an expression vector and transfected into IMCD3 cells. Multiple clones stably expressed gamma-subunit protein under isotonic conditions. Clones expressing the gamma(b) isoform showed enhanced survival at lethal acute hypertonicity compared with either gamma(a) isoform or empty vector (control) expressing clones. We also evaluated the loss of gamma-subunit expression on the survival of IMCD3 cells exposed to hypertonicity employing silencing RNA techniques. Multiple stable gamma-subunit-specific siRNA clones were obtained and exposed to sublethal hypertonicity. Under these conditions, both the level of gamma mRNA and protein was essentially undetectable. The impact of silencing gamma-subunit expression resulted in a 70% reduction at 48 h (P < 0.01) in cell survival compared with empty vector (control) clones. gamma siRNA clones showed a 45% decrease in myo-inositol uptake compared with controls after an 18-h exposure to sublethal hypertonicity. Taken together, these data demonstrate a direct and critical role of the gamma-subunit on IMCD3 cell survival and/or adaptation in response to ionic hypertonic stress.
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Affiliation(s)
- Juan M Capasso
- Division of Renal Diseases and Hypertension, Univeristy of Colorado Health Sciences Center, 4200 E. 9th Ave., Denver, CO 80262, USA
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31
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Cortes VF, Veiga-Lopes FE, Barrabin H, Alves-Ferreira M, Fontes CFL. The gamma subunit of Na+, K+-ATPase: role on ATPase activity and regulatory phosphorylation by PKA. Int J Biochem Cell Biol 2006; 38:1901-13. [PMID: 16815075 DOI: 10.1016/j.biocel.2006.05.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Revised: 05/05/2006] [Accepted: 05/10/2006] [Indexed: 11/23/2022]
Abstract
In kidney, Na+, K+-ATPase is an oligomer (alphabeta gamma) with equimolar amounts of essential alpha and beta subunits and one small hydrophobic FXYD protein (gamma subunit). This report describes gamma subunit as an activator of pig kidney outer medulla Na+, K+-ATPase in aqueous medium. The effects of gamma subunit on Na+, K+-ATPase were dose-dependent and preincubation-dependent. Changes in alphabeta/gamma stoichiometry did not alter Km1 for ATP, and slightly increased Km2, but Vmax was increased at both catalytic and regulatory sites. Hydroxylamine treatment of enzyme phosphorylated by ATP (E-P), in the presence of additional gamma subunit, revealed that 52% of the E-P accumulation was not via acyl-phosphate formation. The gamma subunit was phosphorylated by endogenous kinases and by commercial catalytic subunit of protein kinase A (PKA). Additionally, we demonstrated that PKA phosphorylation of gamma subunit increased its capacity to stimulate ATP hydrolysis. These results suggest that gamma subunit can act as an intrinsic Na+, K+-ATPase regulator in kidney.
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Affiliation(s)
- Vanessa Faria Cortes
- Instituto de Bioquímica Médica, Programa de Biologia Estrutural, Lab. LERPA-Estrutura e Regulação de Proteínas e ATPases, Alameda Bahuinia 400, prédio do CCS, bloco H2-026, Universidade Federal do Rio de Janeiro, CEP 21941-590, Rio de Janeiro, RJ, Brazil
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Duckworth EAM, Butler T, Collier L, Collier S, Pennypacker KR. NF-kappaB protects neurons from ischemic injury after middle cerebral artery occlusion in mice. Brain Res 2006; 1088:167-75. [PMID: 16630592 DOI: 10.1016/j.brainres.2006.02.103] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Revised: 02/22/2006] [Accepted: 02/22/2006] [Indexed: 12/20/2022]
Abstract
Knowledge about the molecular mechanisms of neuronal survival following ischemia is crucial to the development of therapeutic interventions for victims of stroke. Previous research in our laboratory has implicated nuclear factor-kappaB (NF-kappaB) as contributing to neuronal survival in response to toxic or ischemic brain insult, with in vivo models having focused on the rat. To take advantage of genetic alterations available in the mouse, we utilized a murine transient endovascular middle cerebral artery occlusion (MCAO) model to examine the influence of NF-kappaB on neuronal survival. When brains were immunostained for the nuclear localization sequence (NLS) of the p50 subunit of NF-kappaB, a unilateral increase in immunoreactivity was seen, especially in pyramidal cell layers of the ipsilateral (stroked) hippocampus. When transgenic mice lacking p50 were compared with non-transgenic counterparts using Fluoro-Jade, a marker for neurodegeneration, both the hippocampus and striatum showed enhanced neurodegeneration at various survival times after 1 h of MCAO. In the hippocampus specifically, there was an eightfold increase in Fluoro-jade staining in the p50 knockout group vs. the non-transgenic group. Sections double stained for Fluoro-Jade and NF-kappaB activity (using a mouse engineered with a NF-kappaB responsive promoter driving a LacZ gene to produce beta galactosidase) demonstrated neuronal degeneration only in regions sparsely showing NF-kappaB activity, and those demonstrating NF-kappaB activity failed to degenerate. These data provide evidence that NF-kappaB participates in survival signaling following temporary focal ischemia, and thus may represent an attractive target for pharmacologic activation in the treatment of stroke.
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Affiliation(s)
- Edward A M Duckworth
- Department of Neurological Surgery, University of South Florida College of Medicine, Tampa, FL 33612, USA
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Abstract
FXYD proteins belong to a family of small-membrane proteins. Recent experimental evidence suggests that at least five of the seven members of this family, FXYD1 (phospholemman), FXYD2 (gamma-subunit of Na-K-ATPase), FXYD3 (Mat-8), FXYD4 (CHIF), and FXYD7, are auxiliary subunits of Na-K-ATPase and regulate Na-K-ATPase activity in a tissue- and isoform-specific way. These results highlight the complexity of the regulation of Na+ and K+ handling by Na-K-ATPase, which is necessary to ensure appropriate tissue functions such as renal Na+ reabsorption, muscle contractility, and neuronal excitability. Moreover, a mutation in FXYD2 has been linked to cases of human hypomagnesemia, indicating that perturbations in the regulation of Na-K-ATPase by FXYD proteins may be critically involved in pathophysiological states. A better understanding of this novel regulatory mechanism of Na-K-ATPase should help in learning more about its role in pathophysiological states. This review summarizes the present knowledge of the role of FXYD proteins in the modulation of Na-K-ATPase as well as of other proteins, their regulation, and their structure-function relationship.
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Affiliation(s)
- Käthi Geering
- Dept. of Pharmacology and Toxicology, Univ. of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland.
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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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Arystarkhova E, Sweadner KJ. Splice Variants of the Gamma Subunit (FXYD2) and Their Significance in Regulation of the Na, K-ATPase in Kidney. J Bioenerg Biomembr 2005; 37:381-6. [PMID: 16691469 DOI: 10.1007/s10863-005-9475-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The recent discovery of a family of single-span membrane proteins (the FXYD proteins) introduced a new direction to the rather complicated area of regulation of Na, K-ATPase. At least six members of the family have been shown to associate with the Na, K-ATPase in a cell- and tissue-specific manner, while four of them, namely the gamma subunit (FXYD2), CHIF (FXYD4), phospholemman (FXYD1), and dysadherin (FXYD5) have been identified in kidney. All four exhibited different effects on the properties of the pump in heterologous expression systems. Taken along with their non-overlapping expression patterns in the nephron, this provides a potential structural basis for the segment-specific properties of the Na, K-ATPase that had been reported in a number of papers on kidney physiology. This brief review summarizes our own contributions on structure/functional characterization of one of the family members, the gamma subunit (FXYD2). The focus is on splice variants of gamma, their structural similarity and yet distinct effects conferred to Na, K-ATPase.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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36
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Lubarski I, Pihakaski-Maunsbach K, Karlish SJD, Maunsbach AB, Garty H. Interaction with the Na,K-ATPase and Tissue Distribution of FXYD5 (Related to Ion Channel). J Biol Chem 2005; 280:37717-24. [PMID: 16148001 DOI: 10.1074/jbc.m506397200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
FXYD5 (related to ion channel, dysadherin) is a member of the FXYD family of single span type I membrane proteins. Five members of this group have been shown to interact with the Na,K-ATPase and to modulate its properties. However, FXYD5 is structurally different from other family members and has been suggested to play a role in regulating E-cadherin and promoting metastasis (Ino, Y., Gotoh, M., Sakamoto, M., Tsukagoshi, K., and Hirohashi, S. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 365-370). The goal of this study was to determine whether FXYD5 can modulate the Na,K-ATPase activity, establish its cellular and tissue distribution, and characterize its biochemical properties. Anti-FXYD5 antibodies detected a 24-kDa polypeptide that was preferentially expressed in kidney, intestine, spleen, and lung. In kidney, FXYD5 resides in the basolateral membrane of the connecting tubule, the collecting tubule, and the intercalated cells of the collecting duct. However, there is also labeling of the apical membrane in long thin limb of Henle's loop. FXYD5 was effectively immunoprecipitated by antibodies to the alpha subunit of Na,K-ATPase and the anti-FXYD5 antibody immunoprecipitates alpha. Co-expressing FXYD5 with the alpha1 and beta1 subunits of the Na,K-ATPase in Xenopus oocytes elicited a more than 2-fold increase in pump activity, measured either as ouabain-blockable outward current or as ouabain-sensitive (86)Rb(+) uptake. Thus, as found with other FXYD proteins, FXYD5 interacts with the Na,K-ATPase and modulates its properties.
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Affiliation(s)
- Irina Lubarski
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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Jones DH, Li TY, Arystarkhova E, Barr KJ, Wetzel RK, Peng J, Markham K, Sweadner KJ, Fong GH, Kidder GM. Na,K-ATPase from mice lacking the gamma subunit (FXYD2) exhibits altered Na+ affinity and decreased thermal stability. J Biol Chem 2005; 280:19003-11. [PMID: 15755730 DOI: 10.1074/jbc.m500697200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gamma subunit of the Na,K-ATPase, a 7-kDa single-span membrane protein, is a member of the FXYD gene family. Several FXYD proteins have been shown to bind to Na,K-ATPase and modulate its properties, and each FXYD protein appears to alter enzyme kinetics differently. Different results have sometimes been obtained with different experimental systems, however. To test for effects of gamma in a native tissue environment, mice lacking a functional gamma subunit gene (Fxyd2) were generated. These mice were viable and without observable pathology. Prior work in the mouse embryo showed that gamma is expressed at the blastocyst stage. However, there was no delay in blastocele formation, and the expected Mendelian ratios of offspring were obtained even with Fxyd2-/- dams. In adult Fxyd2-/- mouse kidney, splice variants of gamma that have different nephron segment-specific expression patterns were absent. Purified gamma-deficient renal Na,K-ATPase displayed higher apparent affinity for Na+ without significant change in apparent affinity for K+. Affinity for ATP, which was expected to be decreased, was instead slightly increased. The results suggest that regulation of Na+ sensitivity is a major functional role for this protein, whereas regulation of ATP affinity may be context-specific. Most importantly, this implies that gamma and other FXYD proteins have their effects by local and not global conformation change. Na,K-ATPase lacking the gamma subunit had increased thermal lability. Combined with other evidence that gamma participates in an early step of thermal denaturation, this indicates that FXYD proteins may play an important structural role in the enzyme complex.
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Affiliation(s)
- D Holstead Jones
- Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada
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