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Cinarli Yuksel F, Nicolaou P, Spontarelli K, Dohrn MF, Rebelo AP, Koutsou P, Georghiou A, Artigas P, Züchner SL, Kleopa KA, Christodoulou K. The phenotypic spectrum of pathogenic ATP1A1 variants expands: the novel p.P600R substitution causes demyelinating Charcot-Marie-Tooth disease. J Neurol 2023; 270:2576-2590. [PMID: 36738336 PMCID: PMC10130110 DOI: 10.1007/s00415-023-11581-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/17/2023] [Accepted: 01/18/2023] [Indexed: 02/05/2023]
Abstract
BACKGROUND Charcot-Marie-Tooth disease (CMT) is a genetically and clinically heterogeneous group of inherited neuropathies. Monoallelic pathogenic variants in ATP1A1 were associated with axonal and intermediate CMT. ATP1A1 encodes for the catalytic α1 subunit of the Na+/ K+ ATPase. Besides neuropathy, other associated phenotypes are spastic paraplegia, intellectual disability, and renal hypomagnesemia. We hereby report the first demyelinating CMT case due to a novel ATP1A1 variant. METHODS Whole-exome sequencing on the patient's genomic DNA and Sanger sequencing to validate and confirm the segregation of the identified p.P600R ATP1A1 variation were performed. To evaluate functional effects, blood-derived mRNA and protein levels of ATP1A1 and the auxiliary β1 subunit encoded by ATP1B1 were investigated. The ouabain-survival assay was performed in transfected HEK cells to assess cell viability, and two-electrode voltage clamp studies were performed in Xenopus oocytes. RESULTS The variant was absent in the local and global control datasets, falls within a highly conserved protein position, and is in a missense-constrained region. The expression levels of ATP1A1 and ATP1B1 were significantly reduced in the patient compared to healthy controls. Electrophysiology indicated that ATP1A1p.P600R injected Xenopus oocytes have reduced Na+/ K+ ATPase function. Moreover, HEK cells transfected with a construct encoding ATP1A1p.P600R harbouring variants that confers ouabain insensitivity displayed a significant decrease in cell viability after ouabain treatment compared to the wild type, further supporting the pathogenicity of this variant. CONCLUSION Our results further confirm the causative role of ATP1A1 in peripheral neuropathy and broaden the mutational and phenotypic spectrum of ATP1A1-associated CMT.
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Affiliation(s)
- Feride Cinarli Yuksel
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus
| | - Paschalis Nicolaou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus
| | - Kerri Spontarelli
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Maike F Dohrn
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL, USA.,Department of Neurology, RWTH Aachen University Hospital, Aachen, Germany
| | - Adriana P Rebelo
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Pantelitsa Koutsou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus
| | - Anthi Georghiou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Stephan L Züchner
- Dr. John T. Macdonald Foundation, Department of Human Genetics and John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL, USA
| | - Kleopas A Kleopa
- Neuroscience Department and the Centre for Neuromuscular Disorders, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus
| | - Kyproula Christodoulou
- Neurogenetics Department, The Cyprus Institute of Neurology and Genetics, 1683, Nicosia, Cyprus.
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2
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Levic DS, Bagnat M. Polarized transport of membrane and secreted proteins during lumen morphogenesis. Semin Cell Dev Biol 2023; 133:65-73. [PMID: 35307284 PMCID: PMC9481742 DOI: 10.1016/j.semcdb.2022.03.016] [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: 12/03/2021] [Revised: 03/09/2022] [Accepted: 03/12/2022] [Indexed: 10/18/2022]
Abstract
A ubiquitous feature of animal development is the formation of fluid-filled cavities or lumina, which transport gases and fluids across tissues and organs. Among different species, lumina vary drastically in size, scale, and complexity. However, all lumen formation processes share key morphogenetic principles that underly their development. Fundamentally, a lumen simply consists of epithelial cells that encapsulate a continuous internal space, and a common way of building a lumen is via opening and enlarging by filling it with fluid and/or macromolecules. Here, we discuss how polarized targeting of membrane and secreted proteins regulates lumen formation, mainly focusing on ion transporters in vertebrate model systems. We also discuss mechanistic differences observed among invertebrates and vertebrates and describe how the unique properties of the Na+/K+-ATPase and junctional proteins can promote polarization of immature epithelia to build lumina de novo in developing organs.
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Affiliation(s)
- Daniel S Levic
- Department of Cell Biology, Duke University, Durham, NC 27710, USA.
| | - Michel Bagnat
- Department of Cell Biology, Duke University, Durham, NC 27710, USA.
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3
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Arystarkhova E, Toustrup-Jensen MS, Holm R, Ko JK, Lee KE, Feschenko P, Ozelius LJ, Brashear A, Vilsen B, Sweadner KJ. Temperature instability of a mutation at a multidomain junction in Na,K-ATPase isoform ATP1A3 (p.Arg756His) produces a fever-induced neurological syndrome. J Biol Chem 2023; 299:102758. [PMID: 36462665 PMCID: PMC9860391 DOI: 10.1016/j.jbc.2022.102758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 11/18/2022] [Accepted: 11/19/2022] [Indexed: 12/02/2022] Open
Abstract
ATP1A3 encodes the α3 isoform of Na,K-ATPase. In the brain, it is expressed only in neurons. Human ATP1A3 mutations produce a wide spectrum of phenotypes, but particular syndromes are associated with unique substitutions. For arginine 756, at the junction of membrane and cytoplasmic domains, mutations produce encephalopathy during febrile infections. Here we tested the pathogenicity of p.Arg756His (R756H) in isogenic mammalian cells. R756H protein had sufficient transport activity to support cells when endogenous ATP1A1 was inhibited. It had half the turnover rate of wildtype, reduced affinity for Na+, and increased affinity for K+. There was modest endoplasmic reticulum retention during biosynthesis at 37 °C but little benefit from the folding drug phenylbutyrate (4-PBA), suggesting a tolerated level of misfolding. When cells were incubated at just 39 °C, however, α3 protein level dropped without loss of β subunit, paralleled by an increase of endogenous α1. Elevated temperature resulted in internalization of α3 from the surface along with some β subunit, accompanied by cytoplasmic redistribution of a marker of lysosomes and endosomes, lysosomal-associated membrane protein 1. After return to 37 °C, α3 protein levels recovered with cycloheximide-sensitive new protein synthesis. Heating in vitro showed activity loss at a rate 20- to 30-fold faster than wildtype, indicating a temperature-dependent destabilization of protein structure. Arg756 appears to confer thermal resistance as an anchor, forming hydrogen bonds among four linearly distant parts of the Na,K-ATPase structure. Taken together, our observations are consistent with fever-induced symptoms in patients.
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Affiliation(s)
- Elena Arystarkhova
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA.
| | | | - Rikke Holm
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Jae-Kyun Ko
- Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Kyung Eun Lee
- Department of Surgery, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Polina Feschenko
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Laurie J Ozelius
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Allison Brashear
- Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York, USA
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Kathleen J Sweadner
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA.
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4
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Roa-Velázquez D, Xoconostle-Cázares B, Benítez-Cardoza CG, Ortega-López J, Shoshani L, Morales-Ríos E, Gallardo-Hernández S. Expression, purification, and refolding of the recombinant extracellular domain β 1-subunit of the dog Na +/K +-ATPase of the epithelial cells. Protein Expr Purif 2022; 200:106167. [PMID: 36057422 DOI: 10.1016/j.pep.2022.106167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 08/24/2022] [Accepted: 08/26/2022] [Indexed: 11/25/2022]
Abstract
The β1-subunit of the Na+/K+-ATPase is a cell membrane protein, beyond its classic functions, it is also a cell adhesion molecule. β1-subunits on the lateral membrane of dog kidney epithelial cells trans-interact with β1-subunits from another neighboring cells. The β-β interaction is essential for the formation and stabilization of intercellular junctions. Previous studies on site-directed mutagenesis and in silico revealed that the interaction interface involves residues 198-207 and 221-229. However, it is necessary to report the interaction interface at the structural level experimentally. Here, we describe the successful cloning, overexpression in E. coli, and purification of the extracellular domain of the β1-subunit from inclusion bodies. Experimental characterization by size exclusion chromatography and DLS indicated similar hydrodynamic properties of the protein refolded. Structural analysis by circular dichroism and Raman spectroscopy revealed the secondary structures in the folded protein of type β-sheet, α-helix, random coil, and turn. We also performed β1-β1 interaction assays with the recombinant protein, showing dimers' formation (6xHisβ1-β1). Given our results, the recombinant extracellular domain of the β1-subunit is highly similar to the native protein, therefore the current work in our laboratory aims to characterize at the atomic level the interaction interface between EDβ1.
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Affiliation(s)
- Daniela Roa-Velázquez
- Programa de Doctorado en Nanociencias y Nanotecnología, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
| | - Beatriz Xoconostle-Cázares
- Departamento de Bioingeniería y Biotecnología, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
| | - Claudia G Benítez-Cardoza
- Laboratorio de Investigación Bioquímica, Escuela Nacional de Medicina y Homeopatía-Instituto Politécnico Nacional, Guillermo Massieu Helguera 239, Ciudad de México, 07320, Mexico.
| | - Jaime Ortega-López
- Departamento de Bioingeniería y Biotecnología, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
| | - Liora Shoshani
- Departamento de Fisiología Biofísica y Neurociencias, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
| | - Edgar Morales-Ríos
- Departamento de Bioquímica, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
| | - Salvador Gallardo-Hernández
- Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, Ciudad de México, 07360, Mexico.
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5
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Knobloch J, Müller C, Hildebrandt JP. Expression levels and activities of energy-yielding ATPases in the oligohaline neritid snail Theodoxus fluviatilis under changing environmental salinities. Biol Open 2022; 11:274356. [PMID: 35147181 PMCID: PMC8844442 DOI: 10.1242/bio.059190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 12/16/2021] [Indexed: 11/20/2022] Open
Abstract
The aquatic gastropod Theodoxus fluviatilis occurs in Europe and adjacent areas of Asia. The snail species has formed two genetically closely related subgroups, the freshwater ecotype (FW) and the brackish water ecotype (BW). Other than individuals of the FW ecotype, those of the BW ecotype survive in salinities of up to 28‰. Coastal aquatic ecosystems may be affected by climate change due to salinization. Thus, we investigated how the two Theodoxus ecotypes adjust to changes in environmental salinity, focusing on the question whether Na+/K+-ATPase or V-ATPase are regulated on the transcriptional, the translational or at the activity level under changing external salinities. Animals were gradually adjusted to extreme salinities in containers under long-day conditions and constant temperature. Whole body RNA- or protein extracts were prepared. Semi-quantitative PCR- and western blot-analyses did not reveal major changes in transcript or protein abundances for the two transporters under low or high salinity conditions. No significant changes in ATPase activities in whole body extracts of animals adjusted to high or low salinity conditions were detected. We conclude that constitutive expression of ATPases is sufficient to support osmotic and ion regulation in this species under changing salinities given the high level of tolerance with respect to changes in body fluid volume.
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Affiliation(s)
- Jan Knobloch
- Animal Physiology and Biochemistry, Zoological Institute and Museum, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
| | - Christian Müller
- Animal Physiology and Biochemistry, Zoological Institute and Museum, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
| | - Jan-Peter Hildebrandt
- Animal Physiology and Biochemistry, Zoological Institute and Museum, University of Greifswald, Felix Hausdorff-Strasse 1, D-17489 Greifswald, Germany
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6
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Braun JL, Teng ACT, Geromella MS, Ryan CR, Fenech RK, MacPherson REK, Gramolini AO, Fajardo VA. Neuronatin promotes SERCA uncoupling and its expression is altered in skeletal muscles of high-fat diet-fed mice. FEBS Lett 2021; 595:2756-2767. [PMID: 34693525 DOI: 10.1002/1873-3468.14213] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 10/07/2021] [Accepted: 10/15/2021] [Indexed: 11/09/2022]
Abstract
Neuronatin (NNAT) is a transmembrane protein in the endoplasmic reticulum involved in metabolic regulation. It shares sequence homology with sarcolipin (SLN), which negatively regulates the sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA) that maintains energy homeostasis in muscles. Here, we examined whether NNAT could uncouple the Ca2+ transport activity of SERCA from ATP hydrolysis, similarly to SLN. NNAT significantly reduced Ca2+ uptake without altering SERCA activity, ultimately lowering the apparent coupling ratio of SERCA. This effect of NNAT was reversed by the adenylyl cyclase activator forskolin. Furthermore, soleus muscles from high fat diet (HFD)-fed mice showed a significant downregulation in NNAT content compared with chow-fed mice, whereas an upregulation in NNAT content was observed in fast-twitch muscles from HFD- versus chow- fed mice. Therefore, NNAT is a SERCA uncoupler in cells and may function in adaptive thermogenesis.
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Affiliation(s)
- Jessica L Braun
- Department of Kinesiology, Brock University, St. Catharines, Canada.,Centre for Bone and Muscle Health, Brock University, St. Catharines, Canada.,Centre for Neuroscience, Brock University, St. Catharines, Canada
| | - Allen C T Teng
- Department of Physiology, University of Toronto, Canada.,Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, Canada
| | - Mia S Geromella
- Department of Kinesiology, Brock University, St. Catharines, Canada.,Centre for Bone and Muscle Health, Brock University, St. Catharines, Canada.,Centre for Neuroscience, Brock University, St. Catharines, Canada
| | - Chantal R Ryan
- Centre for Neuroscience, Brock University, St. Catharines, Canada.,Department of Health Sciences, Brock University, St. Catharines, Canada
| | - Rachel K Fenech
- Centre for Neuroscience, Brock University, St. Catharines, Canada.,Department of Health Sciences, Brock University, St. Catharines, Canada
| | - Rebecca E K MacPherson
- Centre for Neuroscience, Brock University, St. Catharines, Canada.,Department of Health Sciences, Brock University, St. Catharines, Canada
| | - Anthony O Gramolini
- Department of Physiology, University of Toronto, Canada.,Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, Canada
| | - Val A Fajardo
- Department of Kinesiology, Brock University, St. Catharines, Canada.,Centre for Bone and Muscle Health, Brock University, St. Catharines, Canada.,Centre for Neuroscience, Brock University, St. Catharines, Canada
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7
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Gabrielli NM, Mazzocchi LC, Kryvenko V, Tello K, Herold S, Morty RE, Grimminger F, Dada LA, Seeger W, Sznajder JI, Vadász I. TRAF2 Is a Novel Ubiquitin E3 Ligase for the Na,K-ATPase β-Subunit That Drives Alveolar Epithelial Dysfunction in Hypercapnia. Front Cell Dev Biol 2021; 9:689983. [PMID: 34277634 PMCID: PMC8283768 DOI: 10.3389/fcell.2021.689983] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 06/09/2021] [Indexed: 11/20/2022] Open
Abstract
Several acute and chronic lung diseases are associated with alveolar hypoventilation leading to accumulation of CO2 (hypercapnia). The β-subunit of the Na,K-ATPase plays a pivotal role in maintaining epithelial integrity by functioning as a cell adhesion molecule and regulating cell surface stability of the catalytic α-subunit of the transporter, thereby, maintaining optimal alveolar fluid balance. Here, we identified the E3 ubiquitin ligase for the Na,K-ATPase β-subunit, which promoted polyubiquitination, subsequent endocytosis and proteasomal degradation of the protein upon exposure of alveolar epithelial cells to elevated CO2 levels, thus impairing alveolar integrity. Ubiquitination of the Na,K-ATPase β-subunit required lysine 5 and 7 and mutating these residues (but not other lysines) prevented trafficking of Na,K-ATPase from the plasma membrane and stabilized the protein upon hypercapnia. Furthermore, ubiquitination of the Na,K-ATPase β-subunit was dependent on prior phosphorylation at serine 11 by protein kinase C (PKC)-ζ. Using a protein microarray, we identified the tumor necrosis factor receptor-associated factor 2 (TRAF2) as the E3 ligase driving ubiquitination of the Na,K-ATPase β-subunit upon hypercapnia. Of note, prevention of Na,K-ATPase β-subunit ubiquitination was necessary and sufficient to restore the formation of cell-cell junctions under hypercapnic conditions. These results suggest that a hypercapnic environment in the lung may lead to persistent epithelial dysfunction in affected patients. As such, the identification of the E3 ligase for the Na,K-ATPase may provide a novel therapeutic target, to be employed in patients with acute or chronic hypercapnic respiratory failure, aiming to restore alveolar epithelial integrity.
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Affiliation(s)
- Nieves M. Gabrielli
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
| | - Luciana C. Mazzocchi
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
| | - Vitalii Kryvenko
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
| | - Khodr Tello
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
| | - Susanne Herold
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
| | - Rory E. Morty
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
- Department of Lung Development and Remodeling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Friedrich Grimminger
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
- Institute for Lung Health (ILH), Giessen, Germany
| | - Laura A. Dada
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Werner Seeger
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
- Department of Lung Development and Remodeling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
- Institute for Lung Health (ILH), Giessen, Germany
| | - Jacob I. Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - István Vadász
- Member of the German Center for Lung Research (DZL), Department of Internal Medicine, Justus Liebig University Giessen, Universities of Giessen and Marburg Lung Center (UGMLC), Giessen, Germany
- The Cardio-Pulmonary Institute (CPI), Giessen, Germany
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8
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Kryvenko V, Wessendorf M, Tello K, Herold S, Morty RE, Seeger W, Vadász I. Hypercapnia-induces IRE1α-driven Endoplasmic Reticulum-associated Degradation of the Na,K-ATPase β-subunit. Am J Respir Cell Mol Biol 2021; 65:615-629. [PMID: 34192507 DOI: 10.1165/rcmb.2021-0114oc] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Acute respiratory distress syndrome (ARDS) is often associated with elevated levels of CO2 (hypercapnia) and impaired alveolar fluid clearance. Misfolding of the Na,K-ATPase (NKA), a key molecule involved in both alveolar epithelial barrier tightness and in resolution of alveolar edema, in the endoplasmic reticulum (ER) may decrease plasma membrane (PM) abundance of the transporter. Here, we investigated how hypercapnia affects the NKA β-subunit (NKA-β) in the ER. Exposing murine precision-cut lung slices (PCLS) and human alveolar epithelial A549 cells to elevated CO2 levels led to a rapid decrease of NKA-β abundance in the ER and at the cell surface. Knockdown of ER alpha-mannosidase I (MAN1B1) and ER degradation enhancing alpha-mannosidase like protein 1 by siRNA or treatment with the MAN1B1 inhibitor, kifunensine rescued loss of NKA-β in the ER, suggesting ER-associated degradation (ERAD) of the enzyme. Furthermore, hypercapnia activated the unfolded protein response (UPR) by promoting phosphorylation of inositol-requiring enzyme 1α (IRE1α) and treatment with a siRNA against IRE1α prevented the decrease of NKA-β in the ER. Of note, the hypercapnia-induced phosphorylation of IRE1α was triggered by a Ca2+-dependent mechanism. Additionally, inhibition of the inositol trisphosphate receptor decreased phosphorylation levels of IRE1α in PCLS and A549 cells, suggesting that Ca2+ efflux from the ER might be responsible for IRE1α activation and ERAD of NKA-β. In conclusion, here we provide evidence that hypercapnia attenuates maturation of the regulatory subunit of NKA by activating IRE1α and promoting ERAD, which may contribute to impaired alveolar epithelial integrity in patients with ARDS and hypercapnia.
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Affiliation(s)
- Vitalii Kryvenko
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany
| | - Miriam Wessendorf
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany
| | - Khodr Tello
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany
| | - Susanne Herold
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany
| | - Rory E Morty
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany.,Max-Planck-Institute for Heart and Lung Research, Department of Lung Development and Remodeling, Bad Nauheim, Germany
| | - Werner Seeger
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany.,Max-Planck-Institute for Heart and Lung Research, Department of Lung Development and Remodeling, Bad Nauheim, Germany.,Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany
| | - István Vadász
- Justus Liebig University, Universities of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Department of Internal Medicine, Giessen, Germany.,The Cardio-Pulmonary Institute, Giessen, Germany;
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9
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Kryvenko V, Vagin O, Dada LA, Sznajder JI, Vadász I. Maturation of the Na,K-ATPase in the Endoplasmic Reticulum in Health and Disease. J Membr Biol 2021; 254:447-457. [PMID: 34114062 PMCID: PMC8192048 DOI: 10.1007/s00232-021-00184-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 05/08/2021] [Indexed: 12/11/2022]
Abstract
Abstract The Na,K-ATPase establishes the electrochemical gradient of cells by driving an active exchange of Na+ and K+ ions while consuming ATP. The minimal functional transporter consists of a catalytic α-subunit and a β-subunit with chaperon activity. The Na,K-ATPase also functions as a cell adhesion molecule and participates in various intracellular signaling pathways. The maturation and trafficking of the Na,K-ATPase include co- and post-translational processing of the enzyme in the endoplasmic reticulum (ER) and the Golgi apparatus and subsequent delivery to the plasma membrane (PM). The ER folding of the enzyme is considered as the rate-limiting step in the membrane delivery of the protein. It has been demonstrated that only assembled Na,K-ATPase α:β-complexes may exit the organelle, whereas unassembled, misfolded or unfolded subunits are retained in the ER and are subsequently degraded. Loss of function of the Na,K-ATPase has been associated with lung, heart, kidney and neurological disorders. Recently, it has been shown that ER dysfunction, in particular, alterations in the homeostasis of the organelle, as well as impaired ER-resident chaperone activity may impede folding of Na,K-ATPase subunits, thus decreasing the abundance and function of the enzyme at the PM. Here, we summarize our current understanding on maturation and subsequent processing of the Na,K-ATPase in the ER under physiological and pathophysiological conditions. Graphic Abstract ![]()
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Affiliation(s)
- Vitalii Kryvenko
- Department of Internal Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus Liebig University, Klinikstrasse 33, 35392, Giessen, Germany.,The Cardio-Pulmonary Institute (CPI), Giessen, Germany
| | - Olga Vagin
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.,Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | - Laura A Dada
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - István Vadász
- Department of Internal Medicine, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus Liebig University, Klinikstrasse 33, 35392, Giessen, Germany. .,The Cardio-Pulmonary Institute (CPI), Giessen, Germany.
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10
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Bejček J, Spiwok V, Kmoníčková E, Rimpelová S. Na +/K +-ATPase Revisited: On Its Mechanism of Action, Role in Cancer, and Activity Modulation. Molecules 2021; 26:molecules26071905. [PMID: 33800655 PMCID: PMC8061769 DOI: 10.3390/molecules26071905] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/18/2021] [Accepted: 03/24/2021] [Indexed: 01/08/2023] Open
Abstract
Maintenance of Na+ and K+ gradients across the cell plasma membrane is an essential process for mammalian cell survival. An enzyme responsible for this process, sodium-potassium ATPase (NKA), has been currently extensively studied as a potential anticancer target, especially in lung cancer and glioblastoma. To date, many NKA inhibitors, mainly of natural origin from the family of cardiac steroids (CSs), have been reported and extensively studied. Interestingly, upon CS binding to NKA at nontoxic doses, the role of NKA as a receptor is activated and intracellular signaling is triggered, upon which cancer cell death occurs, which lies in the expression of different NKA isoforms than in healthy cells. Two major CSs, digoxin and digitoxin, originally used for the treatment of cardiac arrhythmias, are also being tested for another indication—cancer. Such drug repositioning has a big advantage in smoother approval processes. Besides this, novel CS derivatives with improved performance are being developed and evaluated in combination therapy. This article deals with the NKA structure, mechanism of action, activity modulation, and its most important inhibitors, some of which could serve not only as a powerful tool to combat cancer, but also help to decipher the so-far poorly understood NKA regulation.
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Affiliation(s)
- Jiří Bejček
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
| | - Vojtěch Spiwok
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
| | - Eva Kmoníčková
- Department of Pharmacology, Second Faculty of Medicine, Charles University, Plzeňská 311, 150 00 Prague, Czech Republic;
| | - Silvie Rimpelová
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 166 28 Prague 6, Czech Republic; (J.B.); (V.S.)
- Faculty of Medicine in Pilsen, Charles University, Alej Svobody 76, 323 00 Pilsen, Czech Republic
- Correspondence: ; Tel.: +420-220-444-360
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11
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Kryvenko V, Vadász I. Molecular mechanisms of Na,K-ATPase dysregulation driving alveolar epithelial barrier failure in severe COVID-19. Am J Physiol Lung Cell Mol Physiol 2021; 320:L1186-L1193. [PMID: 33689516 PMCID: PMC8238442 DOI: 10.1152/ajplung.00056.2021] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A significant number of patients with coronavirus disease 2019 (COVID-19) develop acute respiratory distress syndrome (ARDS) that is associated with a poor outcome. The molecular mechanisms driving failure of the alveolar barrier upon severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remain incompletely understood. The Na,K-ATPase is an adhesion molecule and a plasma membrane transporter that is critically required for proper alveolar epithelial function by both promoting barrier integrity and resolution of excess alveolar fluid, thus enabling appropriate gas exchange. However, numerous SARS-CoV-2-mediated and COVID-19-related signals directly or indirectly impair the function of the Na,K-ATPase, thereby potentially contributing to disease progression. In this Perspective, we highlight some of the putative mechanisms of SARS-CoV-2-driven dysfunction of the Na,K-ATPase, focusing on expression, maturation, and trafficking of the transporter. A therapeutic mean to selectively inhibit the maladaptive signals that impair the Na,K-ATPase upon SARS-CoV-2 infection might be effective in reestablishing the alveolar epithelial barrier and promoting alveolar fluid clearance and thus advantageous in patients with COVID-19-associated ARDS.
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Affiliation(s)
- Vitalii Kryvenko
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Giessen, Germany.,The Cardio-Pulmonary Institute (CPI), Giessen, Germany
| | - István Vadász
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Giessen, Germany.,The Cardio-Pulmonary Institute (CPI), Giessen, Germany
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12
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Arystarkhova E, Ozelius LJ, Brashear A, Sweadner KJ. Misfolding, altered membrane distributions, and the unfolded protein response contribute to pathogenicity differences in Na,K-ATPase ATP1A3 mutations. J Biol Chem 2021; 296:100019. [PMID: 33144327 PMCID: PMC7949067 DOI: 10.1074/jbc.ra120.015271] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 10/22/2020] [Accepted: 11/03/2020] [Indexed: 02/06/2023] Open
Abstract
Missense mutations in ATP1A3, the α3 isoform of Na,K-ATPase, cause neurological phenotypes that differ greatly in symptoms and severity. A mechanistic basis for differences is lacking, but reduction of activity alone cannot explain them. Isogenic cell lines with endogenous α1 and inducible exogenous α3 were constructed to compare mutation properties. Na,K-ATPase is made in the endoplasmic reticulum (ER), but the glycan-free catalytic α subunit complexes with glycosylated β subunit in the ER to proceed through Golgi and post-Golgi trafficking. We previously observed classic evidence of protein misfolding in mutations with severe phenotypes: differences in ER retention of endogenous β1 subunit, impaired trafficking of α3, and cytopathology, suggesting that they misfold during biosynthesis. Here we tested two mutations associated with different phenotypes: D923N, which has a median age of onset of hypotonia or dystonia at 3 years, and L924P, with severe infantile epilepsy and profound impairment. Misfolding during biosynthesis in the ER activates the unfolded protein response, a multiarmed program that enhances protein folding capacity, and if that fails, triggers apoptosis. L924P showed more nascent protein retention in ER than D923N; more ER-associated degradation of α3 (ERAD); larger differences in Na,K-ATPase subunit distributions among subcellular fractions; and greater inactivation of eIF2α, a major defensive step of the unfolded protein response. In L924P there was also altered subcellular distribution of endogenous α1 subunit, analogous to a dominant negative effect. Both mutations showed pro-apoptotic sensitization by reduced phosphorylation of BAD. Encouragingly, however, 4-phenylbutyrate, a pharmacological corrector, reduced L924P ER retention, increased α3 expression, and restored morphology.
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Affiliation(s)
- Elena Arystarkhova
- Laboratory of Membrane Biology, Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA; Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA.
| | - Laurie J Ozelius
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Allison Brashear
- Department of Medicine, University of California at Davis Medical School, Sacramento, California, USA
| | - Kathleen J Sweadner
- Laboratory of Membrane Biology, Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, USA; Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA.
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13
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Marcus EA, Tokhtaeva E, Jimenez JL, Wen Y, Naini BV, Heard AN, Kim S, Capri J, Cohn W, Whitelegge JP, Vagin O. Helicobacter pylori infection impairs chaperone-assisted maturation of Na-K-ATPase in gastric epithelium. Am J Physiol Gastrointest Liver Physiol 2020; 318:G931-G945. [PMID: 32174134 PMCID: PMC7272721 DOI: 10.1152/ajpgi.00266.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Helicobacter pylori infection always induces gastritis, which may progress to ulcer disease or cancer. The mechanisms underlying mucosal injury by the bacteria are incompletely understood. Here, we identify a novel pathway for H. pylori-induced gastric injury, the impairment of maturation of the essential transport enzyme and cell adhesion molecule, Na-K-ATPase. Na-K-ATPase comprises α- and β-subunits that assemble in the endoplasmic reticulum (ER) before trafficking to the plasma membrane. Attachment of H. pylori to gastric epithelial cells increased Na-K-ATPase ubiquitylation, decreased its surface and total levels, and impaired ion balance. H. pylori did not alter degradation of plasmalemma-resident Na-K-ATPase subunits or their mRNA levels. Infection decreased association of α- and β-subunits with ER chaperone BiP and impaired assembly of α/β-heterodimers, as was revealed by quantitative mass spectrometry and immunoblotting of immunoprecipitated complexes. The total level of BiP was not altered, and the decrease in interaction with BiP was not observed for other BiP client proteins. The H. pylori-induced decrease in Na-K-ATPase was prevented by BiP overexpression, stopping protein synthesis, or inhibiting proteasomal, but not lysosomal, protein degradation. The results indicate that H. pylori impairs chaperone-assisted maturation of newly made Na-K-ATPase subunits in the ER independently of a generalized ER stress and induces their ubiquitylation and proteasomal degradation. The decrease in Na-K-ATPase levels is also seen in vivo in the stomachs of gerbils and chronically infected children. Further understanding of H. pylori-induced Na-K-ATPase degradation will provide insights for protection against advanced disease.NEW & NOTEWORTHY This work provides evidence that Helicobacter pylori decreases levels of Na-K-ATPase, a vital transport enzyme, in gastric epithelia, both in acutely infected cultured cells and in chronically infected patients and animals. The bacteria interfere with BiP-assisted folding of newly-made Na-K-ATPase subunits in the endoplasmic reticulum, accelerating their ubiquitylation and proteasomal degradation and decreasing efficiency of the assembly of native enzyme. Decreased Na-K-ATPase expression contributes to H. pylori-induced gastric injury.
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Affiliation(s)
- Elizabeth A. Marcus
- 1Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Elmira Tokhtaeva
- 2Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Jossue L. Jimenez
- 1Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Yi Wen
- 2Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Bita V. Naini
- 3Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Ashley N. Heard
- 1Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Samuel Kim
- 4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
| | - Joseph Capri
- 5Pasarow Mass Spectrometry Laboratory, The Neuropsychiatric Insititute–Semel Institute, University of California, Los Angeles, California
| | - Whitaker Cohn
- 5Pasarow Mass Spectrometry Laboratory, The Neuropsychiatric Insititute–Semel Institute, University of California, Los Angeles, California
| | - Julian P. Whitelegge
- 5Pasarow Mass Spectrometry Laboratory, The Neuropsychiatric Insititute–Semel Institute, University of California, Los Angeles, California
| | - Olga Vagin
- 2Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California,4Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California
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14
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Kryvenko V, Wessendorf M, Morty RE, Herold S, Seeger W, Vagin O, Dada LA, Sznajder JI, Vadász I. Hypercapnia Impairs Na,K-ATPase Function by Inducing Endoplasmic Reticulum Retention of the β-Subunit of the Enzyme in Alveolar Epithelial Cells. Int J Mol Sci 2020; 21:ijms21041467. [PMID: 32098115 PMCID: PMC7073107 DOI: 10.3390/ijms21041467] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 02/16/2020] [Accepted: 02/17/2020] [Indexed: 01/02/2023] Open
Abstract
Alveolar edema, impaired alveolar fluid clearance, and elevated CO2 levels (hypercapnia) are hallmarks of the acute respiratory distress syndrome (ARDS). This study investigated how hypercapnia affects maturation of the Na,K-ATPase (NKA), a key membrane transporter, and a cell adhesion molecule involved in the resolution of alveolar edema in the endoplasmic reticulum (ER). Exposure of human alveolar epithelial cells to elevated CO2 concentrations caused a significant retention of NKA-β in the ER and, thus, decreased levels of the transporter in the Golgi apparatus. These effects were associated with a marked reduction of the plasma membrane (PM) abundance of the NKA-α/β complex as well as a decreased total and ouabain-sensitive ATPase activity. Furthermore, our study revealed that the ER-retained NKA-β subunits were only partially assembled with NKA α-subunits, which suggests that hypercapnia modifies the ER folding environment. Moreover, we observed that elevated CO2 levels decreased intracellular ATP production and increased ER protein and, particularly, NKA-β oxidation. Treatment with α-ketoglutaric acid (α-KG), which is a metabolite that has been shown to increase ATP levels and rescue mitochondrial function in hypercapnia-exposed cells, attenuated the deleterious effects of elevated CO2 concentrations and restored NKA PM abundance and function. Taken together, our findings provide new insights into the regulation of NKA in alveolar epithelial cells by elevated CO2 levels, which may lead to the development of new therapeutic approaches for patients with ARDS and hypercapnia.
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Affiliation(s)
- Vitalii Kryvenko
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
- The Cardio-Pulmonary Institute (CPI), 35392 Giessen, Germany
| | - Miriam Wessendorf
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
| | - Rory E. Morty
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
- The Cardio-Pulmonary Institute (CPI), 35392 Giessen, Germany
- Department of Lung Development and Remodeling, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Susanne Herold
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
- The Cardio-Pulmonary Institute (CPI), 35392 Giessen, Germany
| | - Werner Seeger
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
- The Cardio-Pulmonary Institute (CPI), 35392 Giessen, Germany
- Department of Lung Development and Remodeling, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Olga Vagin
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA;
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA
| | - Laura A. Dada
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (L.A.D.); (J.I.S.)
| | - Jacob I. Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA; (L.A.D.); (J.I.S.)
| | - István Vadász
- Department of Internal Medicine, Justus Liebig University, Universities of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), 35392 Giessen, Germany; (V.K.); (M.W.); (R.E.M.); (S.H.); (W.S.)
- The Cardio-Pulmonary Institute (CPI), 35392 Giessen, Germany
- Correspondence: ; Tel.: +49-641-985-42354; Fax: +49-641-985-42359
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15
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Rayi PR, Koyavski L, Chakraborty D, Bagrov A, Kaphzan H. α1-Na/K-ATPase inhibition rescues aberrant dendritic calcium dynamics and memory deficits in the hippocampus of an Angelman syndrome mouse model. Prog Neurobiol 2019; 182:101676. [DOI: 10.1016/j.pneurobio.2019.101676] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 07/08/2019] [Accepted: 07/31/2019] [Indexed: 12/23/2022]
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16
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Factors in the disease severity of ATP1A3 mutations: Impairment, misfolding, and allele competition. Neurobiol Dis 2019; 132:104577. [PMID: 31425744 DOI: 10.1016/j.nbd.2019.104577] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 07/22/2019] [Accepted: 08/14/2019] [Indexed: 12/21/2022] Open
Abstract
Dominant mutations of ATP1A3, a neuronal Na,K-ATPase α subunit isoform, cause neurological disorders with an exceptionally wide range of severity. Several new mutations and their phenotypes are reported here (p.Asp366His, p.Asp742Tyr, p.Asp743His, p.Leu924Pro, and a VUS, p.Arg463Cys). Mutations associated with mild or severe phenotypes [rapid-onset dystonia-parkinsonism (RDP), alternating hemiplegia of childhood (AHC), or early infantile epileptic encephalopathy (EIEE)] were expressed in HEK-293 cells. Paradoxically, the severity of human symptoms did not correlate with whether there was enough residual activity to support cell survival. We hypothesized that distinct cellular consequences may result not only from pump inactivation but also from protein misfolding. Biosynthesis was investigated in four tetracycline-inducible isogenic cell lines representing different human phenotypes. Two cell biological complications were found. First, there was impaired trafficking of αβ complex to Golgi apparatus and plasma membrane, as well as changes in cell morphology, for two mutations that produced microcephaly or regions of brain atrophy in patients. Second, there was competition between exogenous mutant ATP1A3 (α3) and endogenous ATP1A1 (α1) so that their sum was constant. This predicts that in patients, the ratio of normal to mutant ATP1A3 proteins will vary when misfolding occurs. At the two extremes, the results suggest that a heterozygous mutation that only impairs Na,K-ATPase activity will produce relatively mild disease, while one that activates the unfolded protein response could produce severe disease and may result in death of neurons independently of ion pump inactivation.
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17
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Li S, Dai Z, Yang D, Li W, Dai H, Sun B, Liu X, Xie X, Xu R, Zhao X. Targeting β2 subunit of Na +/K +-ATPase induces glioblastoma cell apoptosis through elevation of intracellular Ca 2. Am J Cancer Res 2019; 9:1293-1308. [PMID: 31285960 PMCID: PMC6610052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 02/18/2019] [Indexed: 06/09/2023] Open
Abstract
Glioblastoma (GBM) is the most frequent brain cancer with poor prognosis and few therapies and urgently requires effective treatments. Na+/K+-ATPase is considered as a target for GBM therapy and development of anticancer drugs. Cardiac glycosides bind the Na+/K+-ATPase α subunit to inhibit enzymatic activity and are promising candidates for anticancer drug development including GBM. However, the comparatively higher doses required for effective anticancer actions cause severe cardiotoxicity. Selectively targeting the ATPase Na+/K+ transporting subunit beta 2 (ATP1B2) that is not expressed in the heart might avoid the cardiotoxicity. However, the effect of targeting ATP1B2 in GBM remains unknown. In this study, we found that high ATP1B2 expression is significantly associated with poor prognosis of patients with GBM. ATP1B2 silencing in GBM cells resulted in remarkably cell cycle arrest at the G2/M phase and apoptosis with concomitant increase in intracellular Ca2+ and activation of p38 kinase, similar to Na+/K+-ATPase inhibition by the classic cardiac glycoside digoxin. ATP1B2 is expressed higher in glioblastoma stem-like cells (GSCs) than in GBM cells and its downregulation induces apoptosis of GSCs. Furthermore, inducible ATP1B2 knockdown significantly inhibit tumor growth in vivo. Our data suggest ATP1B2 has potential as a therapeutic target for GBM.
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Affiliation(s)
- Shirong Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
- Kunming College of Life Science, University of Chinese Academy of SciencesKunming 650204, Yunnan, China
| | - Zhi Dai
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
| | - Dong Yang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
| | - Wenxuan Li
- College of Life Sciences, Sichuan UniversityChengdu 610064, Sichuan, China
| | - Hongjuan Dai
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
| | - Bin Sun
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
| | - Xiuyun Liu
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
- Kunming College of Life Science, University of Chinese Academy of SciencesKunming 650204, Yunnan, China
| | - Xin Xie
- Stake Key Laboratory of Drug Research, The National Center for Drug Screening, Shanghai Institute of Materia Medica, Chinese Academy of SciencesShanghai 201203, China
| | - Rong Xu
- Department of Neurosurgery, Huashan Hospital, Fudan UniversityShanghai 200040, China
| | - Xudong Zhao
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan ProvinceKunming 650223, Yunnan, China
- CAS Center for Excellence in Animal Evolution and Genetics, Chinese Academy of SciencesKunming 650223, China
- Kunming Key Laboratory of Healthy Aging Molecular Mechanism StudyKunming 650223, Yunnan, China
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18
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Li B, Huang X, Xu X, Ning W, Dai H, Wang C. The profibrotic effect of downregulated Na,K‑ATPase β1 subunit in alveolar epithelial cells during lung fibrosis. Int J Mol Med 2019; 44:273-280. [PMID: 31115510 DOI: 10.3892/ijmm.2019.4201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 04/08/2019] [Indexed: 11/06/2022] Open
Abstract
Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease characterized by progressive lung scarring and excessive extracellular matrix depositon. When stimulated, alveolar epithelial cells (AECs) are aberrantly activated, the expression of profibrotic molecules is enhanced, and lung fibrosis is promoted, but the mechanism for this is unclear. It has been reported that a downregulation of the Na,K‑ATPase β1 subunit in renal epithelial cells is involved in renal fibrosis development, but the role of this protein in lung fibrosis remains unknown. In the present study, the expression of the Na,K‑ATPase β1 subunit was revealed to be markedly decreased in AECs of patients with IPF and a bleomycin‑induced pulmonary fibrosis mouse model. Treatment with transforming growth factor β‑1 led to significantly downregulation of the Na,K‑ATPase β1 subunit in lung adenocarcioma A549 cells. Furthermore, the knockdown of the Na,K‑ATPase β1 subunit in A549 cells resulted in the upregulation of profibrotic molecules, activation of the neurogenic locus notch homolog protein 1 and extracellular signal‑regulated kinase 1/2 signaling pathways and induction of endoplasmic reticulum stress. These findings reveal that the downregulation of the Na,K‑ATPase β1 subunit enhances the expression of profibrotic molecules in AECs and may contribute to IPF pathogenesis.
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Affiliation(s)
- Biyun Li
- Department of Pulmonary and Critical Care Medicine, China‑Japan Friendship School of Clinical Medicine, Peking University, Beijing 100029, P.R. China
| | - Xiaoxi Huang
- Department of Medical Research, Beijing Chao‑Yang Hospital, Beijing 100020, P.R. China
| | - Xuefeng Xu
- Department of Surgical Intensive Care Unit, Beijing An‑Zhen Hospital, Capital Medical University, Beijing 100029, P.R. China
| | - Wen Ning
- Department of Genetics and Cellular Biology, College of Life Sciences, Nankai University, Tianjin 300071, P.R. China
| | - Huaping Dai
- Department of Pulmonary and Critical Care Medicine, China‑Japan Friendship School of Clinical Medicine, Peking University, Beijing 100029, P.R. China
| | - Chen Wang
- Department of Pulmonary and Critical Care Medicine, China‑Japan Friendship School of Clinical Medicine, Peking University, Beijing 100029, P.R. China
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19
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Zhang SH, Liu DX, Wang L, Li YH, Wang YH, Zhang H, Su ZK, Fang WG, Qin XX, Shang DS, Li B, Han XN, Zhao WD, Chen YH. A CASPR1-ATP1B3 protein interaction modulates plasma membrane localization of Na +/K +-ATPase in brain microvascular endothelial cells. J Biol Chem 2019; 294:6375-6386. [PMID: 30792309 DOI: 10.1074/jbc.ra118.006263] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 02/13/2019] [Indexed: 01/01/2023] Open
Abstract
Contactin-associated protein 1 (CASPR1 or CNTNAP1) was recently reported to be expressed in brain microvascular endothelial cells (BMECs), the major component of the blood-brain barrier. To investigate CASPR1's physiological role in BMECs, here we used CASPR1 as a bait in a yeast two-hybrid screen to identify CASPR1-interacting proteins and identified the β3 subunit of Na+/K+-ATPase (ATP1B3) as a CASPR1-binding protein. Using recombinant and purified CASPR1, RNAi, GST-pulldown, immunofluorescence, immunoprecipitation, and Na+/K+-ATPase activity assays, we found that ATP1B3's core proteins, but not its glycosylated forms, interact with CASPR1, which was primarily located in the endoplasmic reticulum of BMECs. CASPR1 knockdown reduced ATP1B3 glycosylation and prevented its plasma membrane localization, phenotypes that were reversed by expression of full-length CASPR1. We also found that the CASPR1 knockdown reduces the plasma membrane distribution of the α1 subunit of Na+/K+-ATPase, which is the major component assembled with ATP1B3 in the complete Na+/K+-ATPase complex. The binding of CASPR1 with ATP1B3, but not the α1 subunit, indicated that CASPR1 binds with ATP1B3 to facilitate the assembly of Na+/K+-ATPase. Furthermore, the activity of Na+/K+-ATPase was reduced in CASPR1-silenced BMECs. Interestingly, shRNA-mediated CASPR1 silencing reduced glutamate efflux through the BMECs. These results demonstrate that CASPR1 binds with ATP1B3 and thereby contributes to the regulation of Na+/K+-ATPase maturation and trafficking to the plasma membrane in BMECs. We conclude that CASPR1-mediated regulation of Na+/K+-ATPase activity is important for glutamate transport across the blood-brain barrier.
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Affiliation(s)
- Shu-Hong Zhang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and.,the Department of Cell Biology, School of Basic Medicine, Jiamusi University, 258 Xuefu Street, Jiamusi 154007, Heilongjiang Province, China
| | - Dong-Xin Liu
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Li Wang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Yu-Hua Li
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Yan-Hua Wang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Hu Zhang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Zheng-Kang Su
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Wen-Gang Fang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Xiao-Xue Qin
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - De-Shu Shang
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Bo Li
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Xiao-Ning Han
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Wei-Dong Zhao
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
| | - Yu-Hua Chen
- From the Department of Developmental Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, and Key Laboratory of Medical Cell Biology, Ministry of Education, China Medical University, 77 Puhe Road, Shenbei New District, Shenyang 110122, China and
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Skrenkova K, Lee S, Lichnerova K, Kaniakova M, Hansikova H, Zapotocky M, Suh YH, Horak M. N-Glycosylation Regulates the Trafficking and Surface Mobility of GluN3A-Containing NMDA Receptors. Front Mol Neurosci 2018; 11:188. [PMID: 29915530 PMCID: PMC5994540 DOI: 10.3389/fnmol.2018.00188] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 05/15/2018] [Indexed: 12/20/2022] Open
Abstract
N-methyl-D-aspartate receptors (NMDARs) play critical roles in both excitatory neurotransmission and synaptic plasticity. NMDARs containing the nonconventional GluN3A subunit have different functional properties compared to receptors comprised of GluN1/GluN2 subunits. Previous studies showed that GluN1/GluN2 receptors are regulated by N-glycosylation; however, limited information is available regarding the role of N-glycosylation in GluN3A-containing NMDARs. Using a combination of microscopy, biochemistry, and electrophysiology in mammalian cell lines and rat hippocampal neurons, we found that two asparagine residues (N203 and N368) in the GluN1 subunit and three asparagine residues (N145, N264 and N275) in the GluN3A subunit are required for surface delivery of GluN3A-containing NMDARs. Furthermore, deglycosylation and lectin-based analysis revealed that GluN3A subunits contain extensively modified N-glycan structures, including hybrid/complex forms of N-glycans. We also found (either using a panel of inhibitors or by studying human fibroblasts derived from patients with a congenital disorder of glycosylation) that N-glycan remodeling is not required for the surface delivery of GluN3A-containing NMDARs. Finally, we found that the surface mobility of GluN3A-containing NMDARs in hippocampal neurons is increased following incubation with 1-deoxymannojirimycin (DMM, an inhibitor of the formation of the hybrid/complex forms of N-glycans) and decreased in the presence of specific lectins. These findings provide new insight regarding the mechanisms by which neurons can regulate NMDAR trafficking and function.
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Affiliation(s)
- Kristyna Skrenkova
- Department of Cellular Neurophysiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Department of Neurochemistry, Institute of Experimental Medicine of the Czech Academy of Sciences, Prague, Czechia.,Department of Physiology, Faculty of Science, Charles University in Prague, Prague, Czechia
| | - Sanghyeon Lee
- Department of Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, South Korea
| | - Katarina Lichnerova
- Department of Cellular Neurophysiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Department of Neurochemistry, Institute of Experimental Medicine of the Czech Academy of Sciences, Prague, Czechia
| | - Martina Kaniakova
- Department of Neurochemistry, Institute of Experimental Medicine of the Czech Academy of Sciences, Prague, Czechia
| | - Hana Hansikova
- Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czechia
| | - Martin Zapotocky
- Department of Computational Neuroscience, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Young Ho Suh
- Department of Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, South Korea
| | - Martin Horak
- Department of Cellular Neurophysiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Department of Neurochemistry, Institute of Experimental Medicine of the Czech Academy of Sciences, Prague, Czechia
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Bernhem K, Blom H, Brismar H. Quantification of endogenous and exogenous protein expressions of Na,K-ATPase with super-resolution PALM/STORM imaging. PLoS One 2018; 13:e0195825. [PMID: 29694368 PMCID: PMC5918999 DOI: 10.1371/journal.pone.0195825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 03/30/2018] [Indexed: 01/19/2023] Open
Abstract
Transient transfection of fluorescent fusion proteins is a key enabling technology in fluorescent microscopy to spatio-temporally map cellular protein distributions. Transient transfection of proteins may however bypass normal regulation of expression, leading to overexpression artefacts like misallocations and excess amounts. In this study we investigate the use of STORM and PALM microscopy to quantitatively monitor endogenous and exogenous protein expression. Through incorporation of an N-terminal hemagglutinin epitope to a mMaple3 fused Na,K-ATPase (α1 isoform), we analyze the spatial and quantitative changes of plasma membrane Na,K-ATPase localization during competitive transient expression. Quantification of plasma membrane protein density revealed a time dependent increase of Na,K-ATPase, but no increase in size of protein clusters. Results show that after 41h transfection, the total plasma membrane density of Na,K-ATPase increased by 63% while the endogenous contribution was reduced by 16%.
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Affiliation(s)
- Kristoffer Bernhem
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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Repositioning of Somatic Golgi Apparatus Is Essential for the Dendritic Establishment of Adult-Born Hippocampal Neurons. J Neurosci 2017; 38:631-647. [PMID: 29217690 DOI: 10.1523/jneurosci.1217-17.2017] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 10/02/2017] [Accepted: 10/29/2017] [Indexed: 01/22/2023] Open
Abstract
New dentate granule cells (DGCs) are continuously generated, and integrate into the preexisting hippocampal network in the adult brain. How an adult-born neuron with initially simple spindle-like morphology develops into a DGC, consisting of a single apical dendrite with further branches, remains largely unknown. Here, using retroviruses to birth date and manipulate newborn neurons, we examined initial dendritic formation and possible underlying mechanisms. We found that GFP-expressing newborn cells began to establish a DGC-like morphology at ∼7 d after birth, with a primary dendrite pointing to the molecular layer, but at this stage, with several neurites in the neurogenic zone. Interestingly, the Golgi apparatus, an essential organelle for neurite growth and maintenance, was dynamically repositioning in the soma of newborn cells during this initial integration stage. Two weeks after birth, by which time most neurites in the neurogenic zone were eliminated, a compact Golgi apparatus was positioned exclusively at the base of the primary dendrite. We analyzed the presence of Golgi-associated genes using single-cell transcriptomes of newborn DGCs, and among Golgi-related genes, found the presence of STK25 and STRAD, regulators of embryonic neuronal development. When we knocked down either of these two proteins, we found Golgi mislocalization and extensive aberrant dendrite formation. Furthermore, overexpression of a mutated form of STRAD, underlying the disorder polyhydramnios, megalencephaly, and symptomatic epilepsy, characterized by abnormal brain development and intractable epilepsy, caused similar defects in Golgi localization and dendrite formation in adult-born neurons. Together, our findings reveal a role for Golgi repositioning in regulating the initial integration of adult-born DGCs.SIGNIFICANCE STATEMENT Since the discovery of the continuous generation of new neurons in the adult hippocampus, extensive effort was directed toward understanding the functional contribution of these newborn neurons to the existing hippocampal circuit and associated behaviors, while the molecular mechanisms controlling their early morphological integration are less well understood. Dentate granule cells (DGCs) have a single, complex, apical dendrite. The events leading adult-born DGCs' to transition from simple spindle-like morphology to mature dendrite morphology are largely unknown. We studied establishment of newborn DGCs dendritic pattern and found it was mediated by a signaling pathway regulating precise localization of the Golgi apparatus. Furthermore, this Golgi-associated mechanism for dendrite establishment might be impaired in a human genetic epilepsy syndrome, polyhydramnios, megalencephaly, and symptomatic epilepsy.
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A SINE Insertion in ATP1B2 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA2). G3-GENES GENOMES GENETICS 2017; 7:2729-2737. [PMID: 28620085 PMCID: PMC5555477 DOI: 10.1534/g3.117.043018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Spongy degeneration with cerebellar ataxia (SDCA) is a genetically heterogeneous neurodegenerative disorder with autosomal recessive inheritance in Malinois dogs, one of the four varieties of the Belgian Shepherd breed. Using a combined linkage and homozygosity mapping approach we identified an ∼10.6 Mb critical interval on chromosome 5 in a Malinois family with four puppies affected by cerebellar dysfunction. Visual inspection of the 10.6 Mb interval in whole-genome sequencing data from one affected puppy revealed a 227 bp SINE insertion into the ATP1B2 gene encoding the β2 subunit of the Na+/K+-ATPase holoenzyme (ATP1B2:c.130_131insLT796559.1:g.50_276). The SINE insertion caused aberrant RNA splicing. Immunohistochemistry suggested a reduction of ATP1B2 protein expression in the central nervous system of affected puppies. Atp1b2 knockout mice had previously been reported to show clinical and neurohistopathological findings similar to the affected Malinois puppies. Therefore, we consider ATP1B2:c.130_131ins227 the most likely candidate causative variant for a second subtype of SDCA in Malinois dogs, which we propose to term spongy degeneration with cerebellar ataxia subtype 2 (SDCA2). Our study further elucidates the genetic and phenotypic complexity underlying cerebellar dysfunction in Malinois dogs and provides the basis for a genetic test to eradicate one specific neurodegenerative disease from the breeding population in Malinois and the other varieties of the Belgian Shepherd breed. ATP1B2 thus represents another candidate gene for human inherited cerebellar ataxias, and SDCA2-affected Malinois puppies may serve as a naturally occurring animal model for this disorder.
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Chakraborty D, Fedorova OV, Bagrov AY, Kaphzan H. Selective ligands for Na+/K+-ATPase α isoforms differentially and cooperatively regulate excitability of pyramidal neurons in distinct brain regions. Neuropharmacology 2017; 117:338-351. [DOI: 10.1016/j.neuropharm.2017.02.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/24/2017] [Accepted: 02/17/2017] [Indexed: 11/28/2022]
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25
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Patel S. Plant-derived cardiac glycosides: Role in heart ailments and cancer management. Biomed Pharmacother 2016; 84:1036-1041. [PMID: 27780131 DOI: 10.1016/j.biopha.2016.10.030] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 10/08/2016] [Accepted: 10/10/2016] [Indexed: 12/20/2022] Open
Abstract
Cardiac glycosides, the cardiotonic steroids such as digitalis have been in use as heart ailment remedy since ages. They manipulate the renin-angiotensin axis to improve cardiac output. However; their safety and efficacy have come under scrutiny in recent times, as poisoning and accidental mortalities have been observed. In order to better understand and exploit them as cardiac ionotropes, studies are being pursued using different cardiac glycosides such as digitoxin, digoxin, ouabain, oleandrin etc. Several cardiac glycosides as peruvoside have shown promise in cancer control, especially ovary cancer and leukemia. Functional variability of these glycosides has revealed that not all cardiac glycosides are alike. Apart from their specific affinity to sodium-potassium ATPase, their therapeutic dosage and behavior in poly-morbidity conditions needs to be considered. This review presents a concise account of the key findings in recent years with adequate elaboration of the mechanisms. This compilation is expected to contribute towards management of cardiac, cancer, even viral ailments.
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Affiliation(s)
- Seema Patel
- Bioinformatics and Medical Informatics Research Center, San Diego State University, 5500 Campanile Dr San Diego, CA 92182, USA.
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26
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Habeck M, Tokhtaeva E, Nadav Y, Ben Zeev E, Ferris SP, Kaufman RJ, Bab-Dinitz E, Kaplan JH, Dada LA, Farfel Z, Tal DM, Katz A, Sachs G, Vagin O, Karlish SJD. Selective Assembly of Na,K-ATPase α2β2 Heterodimers in the Heart: DISTINCT FUNCTIONAL PROPERTIES AND ISOFORM-SELECTIVE INHIBITORS. J Biol Chem 2016; 291:23159-23174. [PMID: 27624940 DOI: 10.1074/jbc.m116.751735] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Indexed: 12/31/2022] Open
Abstract
The Na,K-ATPase α2 subunit plays a key role in cardiac muscle contraction by regulating intracellular Ca2+, whereas α1 has a more conventional role of maintaining ion homeostasis. The β subunit differentially regulates maturation, trafficking, and activity of α-β heterodimers. It is not known whether the distinct role of α2 in the heart is related to selective assembly with a particular one of the three β isoforms. We show here by immunofluorescence and co-immunoprecipitation that α2 is preferentially expressed with β2 in T-tubules of cardiac myocytes, forming α2β2 heterodimers. We have expressed human α1β1, α2β1, α2β2, and α2β3 in Pichia pastoris, purified the complexes, and compared their functional properties. α2β2 and α2β3 differ significantly from both α2β1 and α1β1 in having a higher K0.5K+ and lower K0.5Na+ for activating Na,K-ATPase. These features are the result of a large reduction in binding affinity for extracellular K+ and shift of the E1P-E2P conformational equilibrium toward E1P. A screen of perhydro-1,4-oxazepine derivatives of digoxin identified several derivatives (e.g. cyclobutyl) with strongly increased selectivity for inhibition of α2β2 and α2β3 over α1β1 (range 22-33-fold). Molecular modeling suggests a possible basis for isoform selectivity. The preferential assembly, specific T-tubular localization, and low K+ affinity of α2β2 could allow an acute response to raised ambient K+ concentrations in physiological conditions and explain the importance of α2β2 for cardiac muscle contractility. The high sensitivity of α2β2 to digoxin derivatives explains beneficial effects of cardiac glycosides for treatment of heart failure and potential of α2β2-selective digoxin derivatives for reducing cardiotoxicity.
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Affiliation(s)
| | - Elmira Tokhtaeva
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Yotam Nadav
- From the Department of Biomolecular Sciences and
| | - Efrat Ben Zeev
- Israel National Centre for Personalized Medicine, Weizmann Institute of Science, Rehovoth 7610001, Israel
| | - Sean P Ferris
- the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | - Randal J Kaufman
- the Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109
| | | | - Jack H Kaplan
- the Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, and
| | - Laura A Dada
- the Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
| | - Zvi Farfel
- From the Department of Biomolecular Sciences and.,the School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Daniel M Tal
- From the Department of Biomolecular Sciences and
| | - Adriana Katz
- From the Department of Biomolecular Sciences and
| | - George Sachs
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073
| | - Olga Vagin
- the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073,
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Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
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Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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28
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Blom H, Bernhem K, Brismar H. Sodium pump organization in dendritic spines. NEUROPHOTONICS 2016; 3:041803. [PMID: 27175374 PMCID: PMC4855081 DOI: 10.1117/1.nph.3.4.041803] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/04/2016] [Indexed: 05/16/2023]
Affiliation(s)
- Hans Blom
- Royal Institute of Technology, Department of Applied Physics, Roslagstullsbacken 21, Stockholm 10691, SwedenbScience for Life Laboratory, Advanced Light Microscopy Facility, Tomtebodavägen 23A, Solna 17165, Sweden
| | - Kristoffer Bernhem
- Royal Institute of Technology, Department of Applied Physics, Roslagstullsbacken 21, Stockholm 10691, Sweden
| | - Hjalmar Brismar
- Royal Institute of Technology, Department of Applied Physics, Roslagstullsbacken 21, Stockholm 10691, SwedenbScience for Life Laboratory, Advanced Light Microscopy Facility, Tomtebodavägen 23A, Solna 17165, SwedencKarolinska Institutet, Department of Wome
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29
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Tokhtaeva E, Sun H, Deiss-Yehiely N, Wen Y, Soni PN, Gabrielli NM, Marcus EA, Ridge KM, Sachs G, Vazquez-Levin M, Sznajder JI, Vagin O, Dada LA. The O-glycosylated ectodomain of FXYD5 impairs adhesion by disrupting cell-cell trans-dimerization of Na,K-ATPase β1 subunits. J Cell Sci 2016; 129:2394-406. [PMID: 27142834 DOI: 10.1242/jcs.186148] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 04/26/2016] [Indexed: 12/24/2022] Open
Abstract
FXYD5 (also known as dysadherin), a regulatory subunit of the Na,K-ATPase, impairs intercellular adhesion by a poorly understood mechanism. Here, we determined whether FXYD5 disrupts the trans-dimerization of Na,K-ATPase molecules located in neighboring cells. Mutagenesis of the Na,K-ATPase β1 subunit identified four conserved residues, including Y199, that are crucial for the intercellular Na,K-ATPase trans-dimerization and adhesion. Modulation of expression of FXYD5 or of the β1 subunit with intact or mutated β1-β1 binding sites demonstrated that the anti-adhesive effect of FXYD5 depends on the presence of Y199 in the β1 subunit. Immunodetection of the plasma membrane FXYD5 was prevented by the presence of O-glycans. Partial FXYD5 deglycosylation enabled antibody binding and showed that the protein level and the degree of O-glycosylation were greater in cancer than in normal cells. FXYD5-induced impairment of adhesion was abolished by both genetic and pharmacological inhibition of FXYD5 O-glycosylation. Therefore, the extracellular O-glycosylated domain of FXYD5 impairs adhesion by interfering with intercellular β1-β1 interactions, suggesting that the ratio between FXYD5 and α1-β1 heterodimer determines whether the Na,K-ATPase acts as a positive or negative regulator of intercellular adhesion.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, USA
| | - Haying Sun
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Nimrod Deiss-Yehiely
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Yi Wen
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, USA
| | - Pritin N Soni
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Nieves M Gabrielli
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA Instituto de Biología y Medicina Experimental (CONICET-FIBYME), Buenos Aires C1418ADN, Argentina
| | - Elizabeth A Marcus
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, USA Department of Pediatrics, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA
| | - Karen M Ridge
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - George Sachs
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, USA
| | - Mónica Vazquez-Levin
- Instituto de Biología y Medicina Experimental (CONICET-FIBYME), Buenos Aires C1418ADN, Argentina
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Olga Vagin
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA 90095, USA Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA 90095, USA
| | - Laura A Dada
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Laird JG, Pan Y, Modestou M, Yamaguchi DM, Song H, Sokolov M, Baker SA. Identification of a VxP Targeting Signal in the Flagellar Na+ /K+ -ATPase. Traffic 2015; 16:1239-53. [PMID: 26373354 DOI: 10.1111/tra.12332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 09/11/2015] [Accepted: 09/11/2015] [Indexed: 12/15/2022]
Abstract
Na(+) /K(+) -ATPase (NKA) participates in setting electrochemical gradients, cardiotonic steroid signaling and cellular adhesion. Distinct isoforms of NKA are found in different tissues and subcellular localization patterns. For example, NKA α1 is widely expressed, NKA α3 is enriched in neurons and NKA α4 is a testes-specific isoform found in sperm flagella. In some tissues, ankyrin, a key component of the membrane cytoskeleton, can regulate the trafficking of NKA. In the retina, NKA and ankyrin-B are expressed in multiple cell types and immunostaining for each is striking in the synaptic layers. Labeling for NKA is also prominent along the inner segment plasma membrane (ISPM) of photoreceptors. NKA co-immunoprecipitates with ankyrin-B, but on a subcellular level colocalization of these two proteins varies dependent on the cell type. We used transgenic Xenopus laevis tadpoles to evaluate the subcellular trafficking of NKA in photoreceptors. GFP-NKA α3 and α1 are localized to the ISPM, but α4 is localized to outer segments (OSs). We identified a VxP motif responsible for the OS targeting by using a series of chimeric and mutant NKA constructs. This motif is similar to previously identified ciliary targeting motifs. Given the structural similarities between OSs and flagella, our findings shed light on the subcellular targeting of this testes-specific NKA isoform.
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Affiliation(s)
- Joseph G Laird
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Yuan Pan
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Current address: Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Modestos Modestou
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - David M Yamaguchi
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Hongman Song
- Department of Ophthalmology, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV, 26506, USA.,Current address: Section for Translational Research in Retina & Macular Degeneration, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD, 20892, USA
| | - Maxim Sokolov
- Department of Ophthalmology, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV, 26506, USA
| | - Sheila A Baker
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
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Khundmiri SJ. Advances in understanding the role of cardiac glycosides in control of sodium transport in renal tubules. J Endocrinol 2014; 222:R11-24. [PMID: 24781255 DOI: 10.1530/joe-13-0613] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cardiotonic steroids have been used for the past 200 years in the treatment of congestive heart failure. As specific inhibitors of membrane-bound Na(+)/K(+) ATPase, they enhance cardiac contractility through increasing myocardial cell calcium concentration in response to the resulting increase in intracellular Na concentration. The half-minimal concentrations of cardiotonic steroids required to inhibit Na(+)/K(+) ATPase range from nanomolar to micromolar concentrations. In contrast, the circulating levels of cardiotonic steroids under physiological conditions are in the low picomolar concentration range in healthy subjects, increasing to high picomolar levels under pathophysiological conditions including chronic kidney disease and heart failure. Little is known about the physiological function of low picomolar concentrations of cardiotonic steroids. Recent studies have indicated that physiological concentrations of cardiotonic steroids acutely stimulate the activity of Na(+)/K(+) ATPase and activate an intracellular signaling pathway that regulates a variety of intracellular functions including cell growth and hypertrophy. The effects of circulating cardiotonic steroids on renal salt handling and total body sodium homeostasis are unknown. This review will focus on the role of low picomolar concentrations of cardiotonic steroids in renal Na(+)/K(+) ATPase activity, cell signaling, and blood pressure regulation.
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Affiliation(s)
- Syed Jalal Khundmiri
- Division of Nephrology and HypertensionDepartment of MedicineDepartment of Physiology and BiophysicsUniversity of Louisville, 570 S. Preston Street, Louisville, Kentucky 40202, USADivision of Nephrology and HypertensionDepartment of MedicineDepartment of Physiology and BiophysicsUniversity of Louisville, 570 S. Preston Street, Louisville, Kentucky 40202, USA
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Cragle FK, Baldini G. Mild lipid stress induces profound loss of MC4R protein abundance and function. Mol Endocrinol 2014; 28:357-67. [PMID: 24506538 DOI: 10.1210/me.2013-1357] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Food intake is controlled at the central level by the melanocortin pathway in which the agonist α-MSH binds to melanocortin 4 receptor (MC4R), a Gs-coupled G protein-coupled receptor expressed by neurons in the paraventricular nuclei of the hypothalamus, which signals to reduce appetite. Consumption of a high-fat diet induces hypothalamic accumulation of palmitate, endoplasmic reticulum (ER) stress, apoptosis, and unresponsiveness to prolonged treatment with MC4R agonists. Here we have modeled effects of lipid stress on MC4R by using mHypoE-42 immortalized hypothalamic neurons expressing endogenous MC4R and Neuro2A cells expressing a tagged MC4R reporter, HA-MC4R-GFP. In the hypothalamic neurons, exposure to elevated palmitate in the physiological range induced splicing of X-box binding protein 1, but it did not activate C/EBP-homologous protein or induce increased levels of cleaved caspase-3, indicating mild ER stress. Such mild ER stress coexisted with a minimal loss of MC4R mRNA and yet a profound loss of cAMP signaling in response to incubation with the agonist. These findings were mirrored in the Neuro2A cells expressing HA-MC4R-GFP, in which protein abundance of the tagged receptor was decreased, whereas the activity per receptor number was maintained. The loss of cAMP signaling in response to α-MSH by elevated palmitate was corrected by treatment with a chemical chaperone, 4-phenylbutyrate in both mHypoE-42 hypothalamic neurons and in Neuro2A cells in which protein abundance of HA-MC4R-GFP was increased. The data indicate that posttranscriptional decrease of MC4R protein contribute to lower the response to α-MSH in hypothalamic neurons exposed to even a mild level of lipid stress and that a chemical chaperone corrects such a defect.
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Affiliation(s)
- Faith K Cragle
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
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Henriksen C, Kjaer-Sorensen K, Einholm AP, Madsen LB, Momeni J, Bendixen C, Oxvig C, Vilsen B, Larsen K. Molecular cloning and characterization of porcine Na⁺/K⁺-ATPase isoforms α1, α2, α3 and the ATP1A3 promoter. PLoS One 2013; 8:e79127. [PMID: 24236096 PMCID: PMC3827302 DOI: 10.1371/journal.pone.0079127] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 09/17/2013] [Indexed: 11/18/2022] Open
Abstract
Na⁺/K⁺-ATPase maintains electrochemical gradients of Na⁺ and K⁺ essential for a variety of cellular functions including neuronal activity. The α-subunit of the Na⁺/K⁺-ATPase exists in four different isoforms (α1-α4) encoded by different genes. With a view to future use of pig as an animal model in studies of human diseases caused by Na⁺/K⁺-ATPase mutations, we have determined the porcine coding sequences of the α1-α3 genes, ATP1A1, ATP1A2, and ATP1A3, their chromosomal localization, and expression patterns. Our ATP1A1 sequence accords with the sequences from several species at five positions where the amino acid residue of the previously published porcine ATP1A1 sequence differs. These corrections include replacement of glutamine 841 with arginine. Analysis of the functional consequences of substitution of the arginine revealed its importance for Na⁺ binding, which can be explained by interaction of the arginine with the C-terminus, stabilizing one of the Na⁺ sites. Quantitative real-time PCR expression analyses of porcine ATP1A1, ATP1A2, and ATP1A3 mRNA showed that all three transcripts are expressed in the embryonic brain as early as 60 days of gestation. Expression of α3 is confined to neuronal tissue. Generally, the expression patterns of ATP1A1, ATP1A2, and ATP1A3 transcripts were found similar to their human counterparts, except for lack of α3 expression in porcine heart. These expression patterns were confirmed at the protein level. We also report the sequence of the porcine ATP1A3 promoter, which was found to be closely homologous to its human counterpart. The function and specificity of the porcine ATP1A3 promoter was analyzed in transgenic zebrafish, demonstrating that it is active and drives expression in embryonic brain and spinal cord. The results of the present study provide a sound basis for employing the ATP1A3 promoter in attempts to generate transgenic porcine models of neurological diseases caused by ATP1A3 mutations.
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Affiliation(s)
- Carina Henriksen
- Department of Molecular Biology and Genetics, Aarhus University, Tjele, Denmark
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | | | | | - Lone Bruhn Madsen
- Department of Molecular Biology and Genetics, Aarhus University, Tjele, Denmark
| | - Jamal Momeni
- Department of Molecular Biology and Genetics, Aarhus University, Tjele, Denmark
| | - Christian Bendixen
- Department of Molecular Biology and Genetics, Aarhus University, Tjele, Denmark
| | - Claus Oxvig
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
| | - Knud Larsen
- Department of Molecular Biology and Genetics, Aarhus University, Tjele, Denmark
- * E-mail:
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Liebmann T, Blom H, Aperia A, Brismar H. Nanoscale elucidation of Na,K-ATPase isoforms in dendritic spines. ACTA ACUST UNITED AC 2013. [DOI: 10.1186/2192-2853-2-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Abstract
Background
The dimensions of neuronal synapses suggest that optical super-resolution imaging methods are necessary for thorough investigation of protein distributions and interactions. Nanoscopic evaluation of neuronal samples has presented practical hurdles, but advancing methods are making synaptic protein topology and quantification measurements feasible. This work explores the application of Photoactivated Localization Microscopy (PALM) pointillistic super-resolution imaging for investigation of the membrane bound sodium pump, the Na,K-ATPase, in matured neurons.
Results
Two isoforms of the sodium pump (ATP1a1 and ATP1a3) were studied in cultured neurons using the PALM-compatible fluorescent proteins PAGFP and mEos. Nanoscopic imaging reveals a compartmentalized distribution of sodium pumps in dendritic spines. Several nanoclusters of pumps are typically found in the spine head and fewer in the spine neck. The density of sodium pumps was estimated from a quantification of detected single molecules at 450–650 pump copies/μm2 in the spine heads.
Conclusions
We have utilized PALM for dissection of nanoscale localization in mature cultured neurons and demonstrated similar topology and quantification estimates with PAGFP and mEos. PALM topology assessments of the sodium pump appeared similar to previous STED studies, though quantification estimates varied, implying that labeling strategies, sample analysis and choice of nanoscopic imaging method can be critical factors for correct molecular quantification.
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Lourenço J, Pereira R, Gonçalves F, Mendo S. SSH gene expression profile of Eisenia andrei exposed in situ to a naturally contaminated soil from an abandoned uranium mine. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2013; 88:16-25. [PMID: 23164450 DOI: 10.1016/j.ecoenv.2012.10.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 10/12/2012] [Accepted: 10/13/2012] [Indexed: 06/01/2023]
Abstract
The effects of the exposure of earthworms (Eisenia andrei) to contaminated soil from an abandoned uranium mine, were assessed through gene expression profile evaluation by Suppression Subtractive Hybridization (SSH). Organisms were exposed in situ for 56 days, in containers placed both in a contaminated and in a non-contaminated site (reference). Organisms were sampled after 14 and 56 days of exposure. Results showed that the main physiological functions affected by the exposure to metals and radionuclides were: metabolism, oxireductase activity, redox homeostasis and response to chemical stimulus and stress. The relative expression of NADH dehydrogenase subunit 1 and elongation factor 1 alpha was also affected, since the genes encoding these enzymes were significantly up and down-regulated, after 14 and 56 days of exposure, respectively. Also, an EST with homology for SET oncogene was found to be up-regulated. To the best of our knowledge, this is the first time that this gene was identified in earthworms and thus, further studies are required, to clarify its involvement in the toxicity of metals and radionuclides. Considering the results herein presented, gene expression profiling proved to be a very useful tool to detect earthworms underlying responses to metals and radionuclides exposure, pointing out for the detection and development of potential new biomarkers.
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Affiliation(s)
- Joana Lourenço
- Departamento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
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Tokhtaeva E, Clifford RJ, Kaplan JH, Sachs G, Vagin O. Subunit isoform selectivity in assembly of Na,K-ATPase α-β heterodimers. J Biol Chem 2012; 287:26115-25. [PMID: 22696220 DOI: 10.1074/jbc.m112.370734] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To catalyze ion transport, the Na,K-ATPase must contain one α and one β subunit. When expressed by transfection in various expression systems, each of the four α subunit isoforms can assemble with each of the three β subunit isoforms and form an active enzyme, suggesting the absence of selective α-β isoform assembly. However, it is unknown whether in vivo conditions the α-β assembly is random or isoform-specific. The α(2)-β(2) complex was selectively immunoprecipitated by both anti-α(2) and anti-β(2) antibodies from extracts of mouse brain, which contains cells co-expressing multiple Na,K-ATPase isoforms. Neither α(1)-β(2) nor α(2)-β(1) complexes were detected in the immunoprecipitates. Furthermore, in MDCK cells co-expressing α(1), β(1), and β(2) isoforms, a greater fraction of the β(2) subunits was unassembled with α(1) as compared with that of the β(1) subunits, indicating preferential association of the α(1) isoform with the β(1) isoform. In addition, the α(1)-β(2) complex was less resistant to various detergents than the α(1)-β(1) complex isolated from MDCK cells or the α(2)-β(2) complex isolated from mouse brain. Therefore, the diversity of the α-β Na,K-ATPase heterodimers in vivo is determined not only by cell-specific co-expression of particular isoforms, but also by selective association of the α and β subunit isoforms.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California 90073, USA
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37
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Tokhtaeva E, Sachs G, Sun H, Dada LA, Sznajder JI, Vagin O. Identification of the amino acid region involved in the intercellular interaction between the β1 subunits of Na+/K+ -ATPase. J Cell Sci 2012; 125:1605-16. [PMID: 22328500 DOI: 10.1242/jcs.100149] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Epithelial junctions depend on intercellular interactions between β(1) subunits of the Na(+)/K(+)-ATPase molecules of neighboring cells. The interaction between dog and rat subunits is less effective than the interaction between two dog β(1) subunits, indicating the importance of species-specific regions for β(1)-β(1) binding. To identify these regions, the species-specific amino acid residues were mapped on a high-resolution structure of the Na(+)/K(+)-ATPase β(1) subunit to select those exposed towards the β(1) subunit of the neighboring cell. These exposed residues were mutated in both dog and rat YFP-linked β(1) subunits (YFP-β(1)) and also in the secreted extracellular domain of the dog β(1) subunit. Five rat-like mutations in the amino acid region spanning residues 198-207 of the dog YFP-β(1) expressed in Madin-Darby canine kidney (MDCK) cells decreased co-precipitation of the endogenous dog β(1) subunit with YFP-β(1) to the level observed between dog β(1) and rat YFP-β(1). In parallel, these mutations impaired the recognition of YFP-β(1) by the dog-specific antibody that inhibits cell adhesion between MDCK cells. Accordingly, dog-like mutations in rat YFP-β(1) increased both the (YFP-β(1))-β(1) interaction in MDCK cells and recognition by the antibody. Conversely, rat-like mutations in the secreted extracellular domain of the dog β(1) subunit increased its interaction with rat YFP-β(1) in vitro. In addition, these mutations resulted in a reduction of intercellular adhesion between rat lung epithelial cells following addition of the secreted extracellular domain of the dog β(1) subunit to a cell suspension. Therefore, the amino acid region 198-207 is crucial for both trans-dimerization of the Na(+)/K(+)-ATPase β(1) subunits and cell-cell adhesion.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, VAGLAHS/West LA, Building 113, Room 324, 11301 Wilshire Boulevard, Los Angeles, CA 90073, USA
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Vagin O, Dada LA, Tokhtaeva E, Sachs G. The Na-K-ATPase α₁β₁ heterodimer as a cell adhesion molecule in epithelia. Am J Physiol Cell Physiol 2012; 302:C1271-81. [PMID: 22277755 DOI: 10.1152/ajpcell.00456.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ion gradients generated by the Na-K-ATPase play a critical role in epithelia by driving transepithelial transport of various solutes. The efficiency of this Na-K-ATPase-driven vectorial transport depends on the integrity of epithelial junctions that maintain polar distribution of membrane transporters, including the basolateral sodium pump, and restrict paracellular diffusion of solutes. The review summarizes the data showing that, in addition to pumping ions, the Na-K-ATPase located at the sites of cell-cell junction acts as a cell adhesion molecule by interacting with the Na-K-ATPase of the adjacent cell in the intercellular space accompanied by anchoring to the cytoskeleton in the cytoplasm. The review also discusses the experimental evidence on the importance of a specific amino acid region in the extracellular domain of the Na-K-ATPase β(1) subunit for the Na-K-ATPase trans-dimerization and intercellular adhesion. Furthermore, a possible role of N-glycans linked to the Na-K-ATPase β(1) subunit in regulation of epithelial junctions by modulating β(1)-β(1) interactions is discussed.
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Affiliation(s)
- Olga Vagin
- Department of Physiology, School of Medicine, University of California Los Angeles and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, California, USA.
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Akimova OA, Van Huysse J, Tremblay J, Orlov SN. Low efficiency of functional translation of ouabain-resistant α2-Na(+),K(+)-ATPase mRNA in C7-MDCK epithelial cells. Can J Physiol Pharmacol 2011; 90:83-8. [PMID: 22188474 DOI: 10.1139/y11-113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Na(+),K(+)-ATPase is a heterodimer consisting of catalytic α1-α4 and regulatory β1-β3 subunits. Recently, we reported that transfection with ouabain-resistant α1R-Na(+),K(+)-ATPase rescues renal epithelial C7-MDCK cells exclusively expressing the ouabain-sensitive α1S-isoform from the cytotoxic action of ouabain. To explore the role of α2 subunit in ion transport and cytotoxic action of ouabain, we compared the effect of ouabain on K(+) ((86)Rb) influx and the survival of ouabain-treated C7-MDCK cells stably transfected with α1R- and α2R-Na(+),K(+)-ATPase. α2R mRNA in transfected cells was ∼8-fold more abundant than α1R mRNA, whereas immunoreactive α2R protein content was 5-fold lower than endogenous α1S protein. A concentration of 10 µmol/L ouabain led to complete inhibition of (86)Rb influx both in mock- and α2R-transfected cells, whereas maximal inhibition of (86)Rb influx in α1R-transfectd cells was observed at 1000 µmol/L ouabain. In contrast to the massive death of mock- and α2R-transfected cells exposed to 3 µmol/L ouabain , α1R-cells survived after 24 h incubation with 1000 µmol/L ouabain. Thus, our results show that unlike α1R, the presence of α2R-Na(+),K(+)-ATPase subunit mRNA and immunoreactive protein does not contribute to Na(+)/K(+) pump activity, and does not rescue C7-MDCK cells from the cytotoxic action of ouabain. Our results also suggest that the lack of impact of transfected α2-Na(+),K(+)-ATPase on Na(+)/K(+) pump activity and cell survival can be attributed to the low efficiency of its translation and (or) delivery to the plasma membrane of renal epithelial cells.
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Affiliation(s)
- Olga A Akimova
- Research Centre, Centre hospitalier de l'Université de Montréal (CRCHUM) - Technopôle Angus, 2901 Rachel East, Montreal, QC H1W 4A4, Canada
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Tokhtaeva E, Sachs G, Souda P, Bassilian S, Whitelegge JP, Shoshani L, Vagin O. Epithelial junctions depend on intercellular trans-interactions between the Na,K-ATPase β₁ subunits. J Biol Chem 2011; 286:25801-12. [PMID: 21642423 DOI: 10.1074/jbc.m111.252247] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
N-Glycans of the Na,K-ATPase β₁ subunit are important for intercellular adhesion in epithelia, suggesting that epithelial junctions depend on N-glycan-mediated interactions between the β₁ subunits of neighboring cells. The level of co-immunoprecipitation of the endogenous β₁ subunit with various YFP-linked β₁ subunits expressed in Madin-Darby canine kidney cells was used to assess β₁-β₁ interactions. The amount of co-precipitated endogenous dog β₁ was greater with dog YFP-β₁ than with rat YFP-β₁, showing that amino acid-mediated interactions are important for β₁-β₁ binding. Co-precipitation of β₁ was also less with the unglycosylated YFP-β₁ than with glycosylated YFP-β₁, indicating a role for N-glycans. Mixing cells expressing dog YFP-β₁ with non-transfected cells increased the amount of co-precipitated β₁, confirming the presence of intercellular (YFP-β₁)-β₁ complexes. Accordingly, disruption of intercellular junctions decreased the amount of co-precipitated β₁ subunits. The decrease in β₁ co-precipitation both with rat YFP-β₁ and unglycosylated YFP-β₁ was associated with decreased detergent stability of junctional proteins and increased paracellular permeability. Reducing N-glycan branching by specific inhibitors increased (YFP-β₁)-β₁ co-precipitation and strengthened intercellular junctions. Therefore, interactions between the β₁ subunits of neighboring cells maintain integrity of intercellular junctions, and alterations in the β₁ subunit N-glycan structure can regulate stability and tightness of intercellular junctions.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, California 90073, USA
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Friedrich U, Stöhr H, Hilfinger D, Loenhardt T, Schachner M, Langmann T, Weber BH. The Na/K-ATPase is obligatory for membrane anchorage of retinoschisin, the protein involved in the pathogenesis of X-linked juvenile retinoschisis. Hum Mol Genet 2010; 20:1132-42. [DOI: 10.1093/hmg/ddq557] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Tokhtaeva E, Sachs G, Vagin O. Diverse pathways for maturation of the Na,K-ATPase β1 and β2 subunits in the endoplasmic reticulum of Madin-Darby canine kidney cells. J Biol Chem 2010; 285:39289-302. [PMID: 20937802 PMCID: PMC2998159 DOI: 10.1074/jbc.m110.172858] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 10/05/2010] [Indexed: 01/05/2023] Open
Abstract
Proper folding of the Na,K-ATPase β subunits followed by assembly with the α subunits is necessary for their export from the endoplasmic reticulum (ER). Here we examine roles of the ER lectin chaperone, calnexin, and non-lectin chaperone, BiP, in folding and quality control of the β(1) and β(2) subunits in Madin-Darby canine kidney cells. Short term prevention of glycan-calnexin interactions by castanospermine slightly increases ER retention of β(1), suggesting minor involvement of calnexin in subunit folding. However, both prolonged incubation with castanospermine and removal of N-glycosylation sites do not affect the α(1)-assembly or trafficking of β(1) but increase the amount of the β(1)-bound BiP, showing that BiP can compensate for calnexin in assisting β(1) folding. In contrast to β(1), prevention of either N-glycosylation or glycan-calnexin interactions abolishes the α(1)-assembly and export of β(2) from the ER despite increased β(2)-BiP binding. Mutations in the α(1)-interacting regions of β(1) and β(2) subunits impair α(1) assembly but do not affect folding of the β subunits tested by their sensitivity to trypsin. At the same time, these mutations increase the amount of β-bound BiP but not of β-bound calnexin and increase ER retention of both β-isoforms. BiP, therefore, prevents the ER export of folded but α(1)-unassembled β subunits. These α(1)-unassembled β subunits are degraded faster than α(1)-bound β subunits, preventing ER overload. In conclusion, folding of the β(1) and β(2) subunits is assisted predominantly by BiP and calnexin, respectively. Folded β(1) and β(2) either assemble with α(1) or bind BiP. The α(1)-bound β subunits traffic to the Golgi, whereas BiP-bound β subunits are retained and degraded in the ER.
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Affiliation(s)
- Elmira Tokhtaeva
- From the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California 90073
| | - George Sachs
- From the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California 90073
| | - Olga Vagin
- From the Department of Physiology, School of Medicine, UCLA and Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California 90073
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Padilla-Benavides T, Roldán ML, Larre I, Flores-Benitez D, Villegas-Sepúlveda N, Contreras RG, Cereijido M, Shoshani L. The polarized distribution of Na+,K+-ATPase: role of the interaction between {beta} subunits. Mol Biol Cell 2010; 21:2217-25. [PMID: 20444976 PMCID: PMC2893986 DOI: 10.1091/mbc.e10-01-0081] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Na+,K+-ATPase polarity depends on the interaction between the β subunits of Na+,K+-ATPases located on neighboring cells. In the present work, we use energy transfer methods (FRET), in vivo to demonstrate that these β subunits interact directly at the intercellular space of epithelial cells. The very existence of higher metazoans depends on the vectorial transport of substances across epithelia. A crucial element of this transport is the membrane enzyme Na+,K+-ATPase. Not only is this enzyme distributed in a polarized manner in a restricted domain of the plasma membrane but also it creates the ionic gradients that drive the net movement of glucose, amino acids, and ions across the entire epithelium. In a previous work, we have shown that Na+,K+-ATPase polarity depends on interactions between the β subunits of Na+,K+-ATPases located on neighboring cells and that these interactions anchor the entire enzyme at the borders of the intercellular space. In the present study, we used fluorescence resonance energy transfer and coprecipitation methods to demonstrate that these β subunits have sufficient proximity and affinity to permit a direct interaction, without requiring any additional extracellular molecules to span the distance.
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Affiliation(s)
- Teresita Padilla-Benavides
- Department of Physiology Biophysics and Neurosciences, and Department of Molecular Biomedicine, Center for Research and Advanced Studies, CINVESTAV-IPN, Mexico DF 07300, Mexico
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Tokhtaeva E, Munson K, Sachs G, Vagin O. N-glycan-dependent quality control of the Na,K-ATPase beta(2) subunit. Biochemistry 2010; 49:3116-28. [PMID: 20199105 DOI: 10.1021/bi100115a] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Bulky hydrophilic N-glycans stabilize the proper tertiary structure of glycoproteins. In addition, N-glycans comprise the binding sites for the endoplasmic reticulum (ER)-resident lectins that assist correct folding of newly synthesized glycoproteins. To reveal the role of N-glycans in maturation of the Na,K-ATPase beta(2) subunit in the ER, the effects of preventing or modifying the beta(2) subunit N-glycosylation on trafficking of the subunit and its binding to the ER lectin chaperone, calnexin, were studied in MDCK cells. Preventing N-glycosylation abolishes binding of the beta(2) subunit to calnexin and results in the ER retention of the subunit. Furthermore, the fully N-glycosylated beta(2) subunit is retained in the ER when glycan-calnexin interactions are prevented by castanospermine, showing that N-glycan-mediated calnexin binding is required for correct subunit folding. Calnexin binding persists for several hours after translation is stopped with cycloheximide, suggesting that the beta(2) subunit undergoes repeated post-translational calnexin-assisted folding attempts. Homology modeling of the beta(2) subunit using the crystal structure of the alpha(1)-beta(1) Na,K-ATPase shows the presence of a relatively hydrophobic amino acid cluster proximal to N-glycosylation sites 2 and 7. Combined, but not separate, removal of sites 2 and 7 dramatically impairs calnexin binding and prevents the export of the beta(2) subunit from the ER. Similarly, hydrophilic substitution of two hydrophobic amino acids in this cluster disrupts both beta(2)-calnexin binding and trafficking of the subunit to the Golgi. Therefore, the hydrophobic residues in the proximity of N-glycans 2 and 7 are required for post-translational calnexin binding to these N-glycans in incompletely folded conformers, which, in turn, is necessary for maturation of the Na,K-ATPase beta(2) subunit.
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Affiliation(s)
- Elmira Tokhtaeva
- Department of Physiology, School of Medicine, UCLA, and Veterans Administration Greater Los Angeles Health Care System, VAGLAHS/West LA, Building 113, Room 324, 11301 Wilshire Boulevard, Los Angeles, California 90073, USA
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