1
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Olde Hanhof CJA, Dilmen E, Yousef Yengej FA, Latta F, Ammerlaan CME, Schreurs J, Hooijmaijers L, Jansen J, Rookmaaker MB, Orhon I, Verhaar MC, Hoenderop JG. Differentiated mouse kidney tubuloids as a novel in vitro model to study collecting duct physiology. Front Cell Dev Biol 2023; 11:1086823. [PMID: 36760360 PMCID: PMC9905633 DOI: 10.3389/fcell.2023.1086823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/06/2023] [Indexed: 01/26/2023] Open
Abstract
Kidney tubuloids are cell models that are derived from human or mouse renal epithelial cells and show high similarities with their in vivo counterparts. Tubuloids grow polarized in 3D, allow for long-term expansion, and represent multiple segments of the nephron, as shown by their gene expression pattern. In addition, human tubuloids form tight, functional barriers and have been succesfully used for drug testing. Our knowledge of mouse tubuloids, on the other hand, is only minimal. In this study, we further characterized mouse tubuloids and differentiated them towards the collecting duct, which led to a significant upregulation of collecting duct-specific mRNAs of genes and protein expression, including the water channel AQP2 and the sodium channel ENaC. Differentiation resulted in polarized expression of collecting duct water channels AQP2 and AQP3. Also, a physiological response to desmopressin and forskolin stimulation by translocation of AQP2 to the apical membrane was demonstrated. Furthermore, amiloride-sensitive ENaC-mediated sodium uptake was shown in differentiated tubuloids using radioactive tracer sodium. This study demonstrates that mouse tubuloids can be differentiated towards the collecting duct and exhibit collecting duct-specific function. This illustrates the potential use of mouse kidney tubuloids as novel in vitro models to study (patho)physiology of kidney diseases.
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Affiliation(s)
- C. J. A. Olde Hanhof
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - E. Dilmen
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - F. A. Yousef Yengej
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, Netherlands,Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - F. Latta
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - C. M. E. Ammerlaan
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, Utrecht, Netherlands,Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - J. Schreurs
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - L. Hooijmaijers
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - J. Jansen
- Department of Pathology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands,Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Amalia Children’s Hospital, Nijmegen, Netherlands,Institute of Experimental Medicine and Systems Biology, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - M. B. Rookmaaker
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - I. Orhon
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - M. C. Verhaar
- Department of Nephrology and Hypertension, University Medical Center Utrecht, Utrecht, Netherlands
| | - J. G. Hoenderop
- Department of Molecular Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, Netherlands,*Correspondence: J. G. Hoenderop,
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2
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Gómez-Mellado VE, Chang JC, Ho-Mok KS, Bernardino Morcillo C, Kersten RHJ, Oude Elferink RPJ, Verhoeven AJ, Paulusma CC. ATP8B1 Deficiency Results in Elevated Mitochondrial Phosphatidylethanolamine Levels and Increased Mitochondrial Oxidative Phosphorylation in Human Hepatoma Cells. Int J Mol Sci 2022; 23:ijms232012344. [PMID: 36293199 PMCID: PMC9604224 DOI: 10.3390/ijms232012344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 10/11/2022] [Accepted: 10/12/2022] [Indexed: 11/20/2022] Open
Abstract
ATP8B1 is a phospholipid flippase that is deficient in patients with progressive familial intrahepatic cholestasis type 1 (PFIC1). PFIC1 patients suffer from severe liver disease but also present with dyslipidemia, including low plasma cholesterol, of yet unknown etiology. Here we show that ATP8B1 knockdown in HepG2 cells leads to a strong increase in the mitochondrial oxidative phosphorylation (OXPHOS) without a change in glycolysis. The enhanced OXPHOS coincides with elevated low-density lipoprotein receptor protein and increased mitochondrial fragmentation and phosphatidylethanolamine levels. Furthermore, expression of phosphatidylethanolamine N-methyltransferase, an enzyme that catalyzes the conversion of mitochondrial-derived phosphatidylethanolamine to phosphatidylcholine, was reduced in ATP8B1 knockdown cells. We conclude that ATP8B1 deficiency results in elevated mitochondrial PE levels that stimulate mitochondrial OXPHOS. The increased OXPHOS leads to elevated LDLR levels, which provides a possible explanation for the reduced plasma cholesterol levels in PFIC1 disease.
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Affiliation(s)
- Valentina E. Gómez-Mellado
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
| | - Jung-Chin Chang
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
- Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CS Utrecht, The Netherlands
| | - Kam S. Ho-Mok
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
| | - Carmen Bernardino Morcillo
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
| | - Remco H. J. Kersten
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
| | - Ronald P. J. Oude Elferink
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
| | - Arthur J. Verhoeven
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
| | - Coen C. Paulusma
- Amsterdam UMC, University of Amsterdam, Tytgat Institute for Liver and Intestinal Research, Meibergdreef 69, 1105 BK Amsterdam, The Netherlands
- Amsterdam Gastroenterology Endocrinology Metabolism, 1105 AZ Amsterdam, The Netherlands
- Correspondence:
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3
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Li LL, Ke XY, Jiang C, Qin SQ, Liu YY, Xian XH, Liu LZ, He JC, Chen YM, An HF, Sun N, Hu YH, Wang Y, Zhang LN, Lu QY. Na + , K + -ATPase participates in the protective mechanism of rat cerebral ischemia-reperfusion through the interaction with glutamate transporter-1. Fundam Clin Pharmacol 2021; 35:870-881. [PMID: 33481320 DOI: 10.1111/fcp.12652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/19/2021] [Indexed: 11/30/2022]
Abstract
Glutamate excitotoxicity in cerebral ischemia/reperfusion is an important cause of neurological damage. The aim of this study was to investigate the mechanism of Na+, K+-ATPase (NKA) involved in l ow concentration of ouabain (Oua, activating NKA)-induced protection of rat cerebral ischemia-reperfusion injury. The 2,3,5-triphenyltetrazolium chloride (TTC) staining and neurological deficit scores (NDS) were performed to evaluate rat cerebral injury degree respectively at 2 h, 6 h, 1 d and 3 d after reperfusion of middle cerebral artery occlusion (MCAO) 2 h in rats. NKA α1/α2 subunits and glutamate transporter-1 (GLT-1) protein expression were investigated by Western blotting. The cerebral infarct volume ratio were evidently decreased in Oua group vs MCAO/R group at 1 d and 3 d after reperfusion of 2 h MCAO in rats (*p < 0.05 ). Moreover, NDS were not significantly different (p > 0.05 ). NKA α1 was decreased at 6 h and 1 d after reperfusion of 2 h MCAO in rats, and was improved in Oua group. However, NKA α1 and α2 were increased at 3 d after reperfusion of 2 h MCAO in rats, and was decreased in Oua group. GLT-1 was decreased at 6 h, 1 d and 3 d after reperfusion of 2 h MCAO in rats, and was improved in Oua group. These data indicated that l ow concentration of Oua could improve MCAO/R injury through probably changing NKA α1/α2 and GLT-1 protein expression, then increasing GLT-1 function and promoting Glu transport and absorption, which could be useful to determine potential therapeutic strategies for patients with stroke. Low concentration of Oua improved rat MCAO/R injury via NKA α1/α2 and GLT-1.
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Affiliation(s)
- Lin-Lin Li
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Xue-Ying Ke
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Chen Jiang
- Forensic Medical College, Hebei Medical University, Hebei, China
| | - Shi-Qi Qin
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yang-Yang Liu
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Xiao-Hui Xian
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Li-Zhe Liu
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Jin-Chen He
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Ya-Meng Chen
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Hong-Fei An
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Nan Sun
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yue-Hua Hu
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yan Wang
- North China University of Science and Technology Affiliated Hospital, Hebei, China
| | - Li-Nan Zhang
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Qi-Yong Lu
- Department of Neurosurgery, Hengshui Fifth People's Hospital, Hebei, China
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4
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Moreno C, Yano S, Bezanilla F, Latorre R, Holmgren M. Transient Electrical Currents Mediated by the Na +/K +-ATPase: A Tour from Basic Biophysics to Human Diseases. Biophys J 2020; 119:236-242. [PMID: 32579966 PMCID: PMC7376075 DOI: 10.1016/j.bpj.2020.06.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/06/2020] [Accepted: 06/03/2020] [Indexed: 01/14/2023] Open
Abstract
The Na+/K+-ATPase is a chemical molecular machine responsible for the movement of Na+ and K+ ions across the cell membrane. These ions are moved against their electrochemical gradients, so the protein uses the free energy of ATP hydrolysis to transport them. In fact, the Na+/K+-ATPase is the single largest consumer of energy in most cells. In each pump cycle, the protein sequentially exports 3Na+ out of the cell, then imports 2K+ into the cell at an approximate rate of 200 cycles/s. In each half cycle of the transport process, there is a state in which ions are stably trapped within the permeation pathway of the protein by internal and external gates in their closed states. These gates are required to open alternately; otherwise, passive ion diffusion would be a wasteful end of the cell's energy. Once one of these gates open, ions diffuse from their binding sites to the accessible milieu, which involves moving through part of the electrical field across the membrane. Consequently, ions generate transient electrical currents first discovered more than 30 years ago. They have been studied in a variety of preparations, including native and heterologous expression systems. Here, we review three decades' worth of work using these transient electrical signals to understand the kinetic transitions of the movement of Na+ and K+ ions through the Na+/K+-ATPase and propose the significance that this work might have to the understanding of the dysfunction of human pump orthologs responsible for some newly discovered neurological pathologies.
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Affiliation(s)
- Cristina Moreno
- Molecular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Sho Yano
- Medical Genetics and Genomic Medicine Training Program, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Miguel Holmgren
- Molecular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland.
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5
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Snow JP, Westlake G, Klofas LK, Jeon S, Armstrong LC, Swoboda KJ, George AL, Ess KC. Neuronal modeling of alternating hemiplegia of childhood reveals transcriptional compensation and replicates a trigger-induced phenotype. Neurobiol Dis 2020; 141:104881. [PMID: 32348881 DOI: 10.1016/j.nbd.2020.104881] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 04/18/2020] [Accepted: 04/24/2020] [Indexed: 01/30/2023] Open
Abstract
Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disease caused by heterozygous de novo missense mutations in the ATP1A3 gene that encodes the neuronal specific α3 subunit of the Na,K-ATPase (NKA) pump. Mechanisms underlying patient episodes including environmental triggers remain poorly understood, and there are no empirically proven treatments for AHC. In this study, we generated patient-specific induced pluripotent stem cells (iPSCs) and isogenic controls for the E815K ATP1A3 mutation that causes the most phenotypically severe form of AHC. Using an in vitro iPSC-derived cortical neuron disease model, we found elevated levels of ATP1A3 mRNA in AHC lines compared to controls, without significant perturbations in protein expression. Microelectrode array analyses demonstrated that in cortical neuronal cultures, ATP1A3+/E815K iPSC-derived neurons displayed less overall activity than neurons differentiated from isogenic mutation-corrected and unrelated control cell lines. However, induction of cellular stress by elevated temperature revealed a hyperactivity phenotype following heat stress in ATP1A3+/E815K neurons compared to control lines. Treatment with flunarizine, a drug commonly used to prevent AHC episodes, did not impact this stress-triggered phenotype. These findings support the use of iPSC-derived neuronal cultures for studying complex neurodevelopmental conditions such as AHC and provide a platform for mechanistic discovery in a human disease model.
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Affiliation(s)
- John P Snow
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Grant Westlake
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lindsay K Klofas
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA
| | - Soyoun Jeon
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Laura C Armstrong
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kathryn J Swoboda
- Center for Genomic Medicine, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Kevin C Ess
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.
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6
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Remote sensing and signaling in kidney proximal tubules stimulates gut microbiome-derived organic anion secretion. Proc Natl Acad Sci U S A 2019; 116:16105-16110. [PMID: 31341083 PMCID: PMC6689987 DOI: 10.1073/pnas.1821809116] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Membrane transporters and receptors are responsible for balancing nutrient and metabolite levels to aid body homeostasis. Here, we report that proximal tubule cells in kidneys sense elevated endogenous, gut microbiome-derived, metabolite levels through EGF receptors and downstream signaling to induce their secretion by up-regulating the organic anion transporter-1 (OAT1). Remote metabolite sensing and signaling was observed in kidneys from healthy volunteers and rats in vivo, leading to induced OAT1 expression and increased removal of indoxyl sulfate, a prototypical microbiome-derived metabolite and uremic toxin. Using 2D and 3D human proximal tubule cell models, we show that indoxyl sulfate induces OAT1 via AhR and EGFR signaling, controlled by miR-223. Concomitantly produced reactive oxygen species (ROS) control OAT1 activity and are balanced by the glutathione pathway, as confirmed by cellular metabolomic profiling. Collectively, we demonstrate remote metabolite sensing and signaling as an effective OAT1 regulation mechanism to maintain plasma metabolite levels by controlling their secretion.
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7
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Cornelius F, Tsunekawa N, Toyoshima C. Distinct pH dependencies of Na +/K + selectivity at the two faces of Na,K-ATPase. J Biol Chem 2017; 293:2195-2205. [PMID: 29247005 DOI: 10.1074/jbc.ra117.000700] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 11/28/2017] [Indexed: 11/06/2022] Open
Abstract
The sodium pump (Na,K-ATPase) in animal cells is vital for actively maintaining ATP hydrolysis-powered Na+ and K+ electrochemical gradients across the cell membrane. These ion gradients drive co- and countertransport and are critical for establishing the membrane potential. It has been an enigma how Na,K-ATPase discriminates between Na+ and K+, despite the pumped ion on each side being at a lower concentration than the other ion. Recent crystal structures of analogs of the intermediate conformations E2·Pi·2K+ and Na+-bound E1∼P·ADP suggest that the dimensions of the respective binding sites in Na,K-ATPase are crucial in determining its selectivity. Here, we found that the selectivity at each membrane face is pH-dependent and that this dependence is unique for each face. Most notable was a strong increase in the specific affinity for K+ at the extracellular face (i.e. E2 conformation) as the pH is lowered from 7.5 to 5. We also observed a smaller increase in affinity for K+ on the cytoplasmic side (E1 conformation), which reduced the selectivity for Na+ Theoretical analysis of the pKa values of ion-coordinating acidic amino acid residues suggested that the face-specific pH dependences and Na+/K+ selectivities may arise from the protonation or ionization of key residues. The increase in K+ selectivity at low pH on the cytoplasmic face, for instance, appeared to be associated with Asp808 protonation. We conclude that changes in the ionization state of coordinating residues in Na,K-ATPase could contribute to altering face-specific ion selectivity.
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Affiliation(s)
- Flemming Cornelius
- From the Department of Biomedicine, University of Aarhus, Ole Worms Allé 6, 8000 Aarhus C, Denmark and
| | - Naoki Tsunekawa
- the Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032
| | - Chikashi Toyoshima
- the Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032
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8
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Meyer DJ, Gatto C, Artigas P. On the effect of hyperaldosteronism-inducing mutations in Na/K pumps. J Gen Physiol 2017; 149:1009-1028. [PMID: 29030398 PMCID: PMC5677107 DOI: 10.1085/jgp.201711827] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/25/2017] [Accepted: 09/05/2017] [Indexed: 11/29/2022] Open
Abstract
Mutated Na/K pumps in adrenal adenomas are thought to cause hyperaldosteronism via a gain-of-function effect involving a depolarizing inward current. The findings of Meyer et al. suggest instead that the common mechanism by which Na/K pump mutants lead to hyperaldosteronism is a loss-of-function. Primary aldosteronism, a condition in which too much aldosterone is produced and that leads to hypertension, is often initiated by an aldosterone-producing adenoma within the zona glomerulosa of the adrenal cortex. Somatic mutations of ATP1A1, encoding the Na/K pump α1 subunit, have been found in these adenomas. It has been proposed that a passive inward current transported by several of these mutant pumps is a "gain-of-function" activity that produces membrane depolarization and concomitant increases in aldosterone production. Here, we investigate whether the inward current through mutant Na/K pumps is large enough to induce depolarization of the cells that harbor them. We first investigate inward currents induced by these mutations in Xenopus Na/K pumps expressed in Xenopus oocytes and find that these inward currents are similar in amplitude to wild-type outward Na/K pump currents. Subsequently, we perform a detailed functional evaluation of the human Na/K pump mutants L104R, delF100-L104, V332G, and EETA963S expressed in Xenopus oocytes. By combining two-electrode voltage clamp with [3H]ouabain binding, we measure the turnover rate of these inward currents and compare it to the turnover rate for outward current through wild-type pumps. We find that the turnover rate of the inward current through two of these mutants (EETA963S and L104R) is too small to induce significant cell depolarization. Electrophysiological characterization of another hyperaldosteronism-inducing mutation, G99R, reveals the absence of inward currents under many different conditions, including in the presence of the regulator FXYD1 as well as with mammalian ionic concentrations and body temperatures. Instead, we observe robust outward currents, but with significantly reduced affinities for intracellular Na+ and extracellular K+. Collectively, our results point to loss-of-function as the common mechanism for the hyperaldosteronism induced by these Na/K pump mutants.
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Affiliation(s)
- Dylan J Meyer
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX.,School of Biological Sciences, Illinois State University, Normal, IL
| | - Craig Gatto
- School of Biological Sciences, Illinois State University, Normal, IL
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX
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9
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Caetano-Pinto P, Jamalpoor A, Ham J, Goumenou A, Mommersteeg M, Pijnenburg D, Ruijtenbeek R, Sanchez-Romero N, van Zelst B, Heil SG, Jansen J, Wilmer MJ, van Herpen CML, Masereeuw R. Cetuximab Prevents Methotrexate-Induced Cytotoxicity in Vitro through Epidermal Growth Factor Dependent Regulation of Renal Drug Transporters. Mol Pharm 2017; 14:2147-2157. [PMID: 28493713 PMCID: PMC5462489 DOI: 10.1021/acs.molpharmaceut.7b00308] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
The combination of methotrexate with
epidermal growth factor receptor
(EGFR) recombinant antibody, cetuximab, is currently being investigated
in treatment of head and neck carcinoma. As methotrexate is cleared
by renal excretion, we studied the effect of cetuximab on renal methotrexate
handling. We used human conditionally immortalized proximal tubule
epithelial cells overexpressing either organic anion transporter 1
or 3 (ciPTEC-OAT1/ciPTEC-OAT3) to examine OAT1 and OAT3, and the efflux
pumps breast cancer resistance protein (BCRP), multidrug resistance
protein 4 (MRP4), and P-glycoprotein (P-gp) in methotrexate handling
upon EGF or cetuximab treatment. Protein kinase microarrays and knowledge-based
pathway analysis were used to predict EGFR-mediated transporter regulation.
Cytotoxic effects of methotrexate were evaluated using the dimethylthiazol
bromide (MTT) viability assay. Methotrexate inhibited OAT-mediated
fluorescein uptake and decreased efflux of Hoechst33342 and glutathione-methylfluorescein
(GS-MF), which suggested involvement of OAT1/3, BCRP, and MRP4 in
transepithelial transport, respectively. Cetuximab reversed the EGF-increased
expression of OAT1 and BCRP as well as their membrane expressions
and transport activities, while MRP4 and P-gp were increased. Pathway
analysis predicted cetuximab-induced modulation of PKC and PI3K pathways
downstream EGFR/ERBB2/PLCg. Pharmacological inhibition of ERK decreased
expression of OAT1 and BCRP, while P-gp and MRP4 were increased. AKT
inhibition reduced all transporters. Exposure to methotrexate for
24 h led to a decreased viability, an effect that was reversed by
cetuximab. In conclusion, cetuximab downregulates OAT1 and BCRP while
upregulating P-gp and MRP4 through an EGFR-mediated regulation of
PI3K-AKT and MAPKK-ERK pathways. Consequently, cetuximab attenuates
methotrexate-induced cytotoxicity, which opens possibilities for further
research into nephroprotective comedication therapies.
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Affiliation(s)
- Pedro Caetano-Pinto
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands
| | - Amer Jamalpoor
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands
| | - Janneke Ham
- Department of Oncology, Radboud University Medical Center , 6525 GA Nijmegen, The Netherlands
| | - Anastasia Goumenou
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands
| | | | | | | | - Natalia Sanchez-Romero
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands.,Centro Investigación Biomédica de Aragón (CIBA), 50009 Zaragoza, Spain
| | - Bertrand van Zelst
- Department of Clinical Chemistry, ErasmusMC , 3015 CE Rotterdam, The Netherlands
| | - Sandra G Heil
- Department of Clinical Chemistry, ErasmusMC , 3015 CE Rotterdam, The Netherlands
| | - Jitske Jansen
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands
| | - Martijn J Wilmer
- Department of Pharmacology and Toxicology, Radboud Institute of Molecular Life Sciences, Radboudumc , 6500 HB Nijmegen, The Netherlands
| | - Carla M L van Herpen
- Department of Oncology, Radboud University Medical Center , 6525 GA Nijmegen, The Netherlands
| | - Rosalinde Masereeuw
- Division of Pharmacology, Utrecht Institute for Pharmaceutical Sciences, Faculty of Science, Utrecht University , 3584 CG Utrecht, The Netherlands
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10
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Isaksen TJ, Kros L, Vedovato N, Holm TH, Vitenzon A, Gadsby DC, Khodakhah K, Lykke-Hartmann K. Hypothermia-induced dystonia and abnormal cerebellar activity in a mouse model with a single disease-mutation in the sodium-potassium pump. PLoS Genet 2017; 13:e1006763. [PMID: 28472154 PMCID: PMC5436892 DOI: 10.1371/journal.pgen.1006763] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 05/18/2017] [Accepted: 04/17/2017] [Indexed: 11/18/2022] Open
Abstract
Mutations in the neuron-specific α3 isoform of the Na+/K+-ATPase are found in patients suffering from Rapid onset Dystonia Parkinsonism and Alternating Hemiplegia of Childhood, two closely related movement disorders. We show that mice harboring a heterozygous hot spot disease mutation, D801Y (α3+/D801Y), suffer abrupt hypothermia-induced dystonia identified by electromyographic recordings. Single-neuron in vivo recordings in awake α3+/D801Y mice revealed irregular firing of Purkinje cells and their synaptic targets, the deep cerebellar nuclei neurons, which was further exacerbated during dystonia and evolved into abnormal high-frequency burst-like firing. Biophysically, we show that the D-to-Y mutation abolished pump-mediated Na+/K+ exchange, but allowed the pumps to bind Na+ and become phosphorylated. These findings implicate aberrant cerebellar activity in α3 isoform-related dystonia and add to the functional understanding of the scarce and severe mutations in the α3 isoform Na+/K+-ATPase. The neurological spectrum associated with mutations in the ATP1A3 gene, encoding the α3 isoform of the Na+/K+-ATPase, is complex and still poorly understood. To elucidate the disease-specific pathophysiology, we examined a mouse model harboring the mutation D801Y, which was originally found in a patient with Rapid onset Dystonia Parkinsonism, but recently, also in a patient with Alternating Hemiplegia of Childhood. We found that this model exhibited motor deficits and developed dystonia when exposed to a drop in body temperature. Cerebellar in vivo recordings in awake mice revealed irregular firing of Purkinje cells and their synaptic targets, the deep cerebellar nuclei neurons, which was further exacerbated and evolved into abnormal high-frequency burst firing during dystonia. The development of specific neurological features within the ATP1A3 mutation spectrum, such as dystonia, are thought to reflect the functional consequences of each mutation, thus to investigate the consequence of the D801Y mutations we characterized mutated D-to-Y Na+/K+-ATPases expressed in Xenopus oocytes. These in vitro studies showed that the D-to-Y mutation abolishes pump-mediated Na+/K+ exchange, but still allows the pumps to bind Na+ and become phosphorylated, trapping them in conformations that instead support proton influx.
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Affiliation(s)
- Toke Jost Isaksen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Lieke Kros
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Natascia Vedovato
- The Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, New York, New York, United States of America
| | - Thomas Hellesøe Holm
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Ariel Vitenzon
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David C. Gadsby
- The Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, New York, New York, United States of America
| | - Kamran Khodakhah
- Dominick P Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Karin Lykke-Hartmann
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
- Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Aarhus C, Denmark
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- * E-mail:
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11
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Koenderink JB, Swarts HGP. Expression of Na,K-ATPase and H,K-ATPase Isoforms with the Baculovirus Expression System. Methods Mol Biol 2016; 1377:71-8. [PMID: 26695023 DOI: 10.1007/978-1-4939-3179-8_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
P-type ATPases can be expressed in several cell systems. The baculovirus expressions system uses an insect virus to enter and express proteins in Sf9 insect cells. This expression system is a lytic system in which the cells will die a few days after viral infection. Subsequently, the expressed proteins can be isolated. Insect cells are a perfect system to study P-type ATPases as they have little or no endogenous Na,K-ATPase activity and other ATPase activities can be inhibited easily. Here we describe in detail the expression and isolation of Na,K-ATPase and H,K-ATPase isoforms with the baculovirus expression system.
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Affiliation(s)
- Jan B Koenderink
- Pharmacology/Toxicology 149, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, 9101, 6500 HB, Nijmegen, The Netherlands.
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van der Mark VA, Ghiboub M, Marsman C, Zhao J, van Dijk R, Hiralall JK, Ho-Mok KS, Castricum Z, de Jonge WJ, Oude Elferink RPJ, Paulusma CC. Phospholipid flippases attenuate LPS-induced TLR4 signaling by mediating endocytic retrieval of Toll-like receptor 4. Cell Mol Life Sci 2016; 74:715-730. [PMID: 27628304 PMCID: PMC5272906 DOI: 10.1007/s00018-016-2360-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 08/31/2016] [Accepted: 09/06/2016] [Indexed: 01/01/2023]
Abstract
P4-ATPases are lipid flippases that catalyze the transport of phospholipids to create membrane phospholipid asymmetry and to initiate the biogenesis of transport vesicles. Here we show, for the first time, that lipid flippases are essential to dampen the inflammatory response and to mediate the endotoxin-induced endocytic retrieval of Toll-like receptor 4 (TLR4) in human macrophages. Depletion of CDC50A, the β-subunit that is crucial for the activity of multiple P4-ATPases, resulted in endotoxin-induced hypersecretion of proinflammatory cytokines, enhanced MAP kinase signaling and constitutive NF-κB activation. In addition, CDC50A-depleted THP-1 macrophages displayed reduced tolerance to endotoxin. Moreover, endotoxin-induced internalization of TLR4 was strongly reduced and coincided with impaired endosomal MyD88-independent signaling. The phenotype of CDC50A-depleted cells was also induced by separate knockdown of two P4-ATPases, namely ATP8B1 and ATP11A. We conclude that lipid flippases are novel elements of the innate immune response that are essential to attenuate the inflammatory response, possibly by mediating endotoxin-induced internalization of TLR4.
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Affiliation(s)
- Vincent A van der Mark
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Mohammed Ghiboub
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Casper Marsman
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Jing Zhao
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Remco van Dijk
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Johan K Hiralall
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Kam S Ho-Mok
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Zoë Castricum
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Wouter J de Jonge
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Ronald P J Oude Elferink
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands
| | - Coen C Paulusma
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Meibergdreef 69-71, 1105 BK, Amsterdam, The Netherlands.
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13
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Holm R, Toustrup-Jensen MS, Einholm AP, Schack VR, Andersen JP, Vilsen B. Neurological disease mutations of α3 Na +,K +-ATPase: Structural and functional perspectives and rescue of compromised function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1807-1828. [PMID: 27577505 DOI: 10.1016/j.bbabio.2016.08.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 08/19/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
Na+,K+-ATPase creates transmembrane ion gradients crucial to the function of the central nervous system. The α-subunit of Na+,K+-ATPase exists as four isoforms (α1-α4). Several neurological phenotypes derive from α3 mutations. The effects of some of these mutations on Na+,K+-ATPase function have been studied in vitro. Here we discuss the α3 disease mutations as well as information derived from studies of corresponding mutations of α1 in the light of the high-resolution crystal structures of the Na+,K+-ATPase. A high proportion of the α3 disease mutations occur in the transmembrane sector and nearby regions essential to Na+ and K+ binding. In several cases the compromised function can be traced to disturbance of the Na+ specific binding site III. Recently, a secondary mutation was found to rescue the defective Na+ binding caused by a disease mutation. A perspective is that it may be possible to develop an efficient pharmaceutical mimicking the rescuing effect.
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Affiliation(s)
- Rikke Holm
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | | | - Anja P Einholm
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Vivien R Schack
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Jens P Andersen
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
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14
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Stanley CM, Gagnon DG, Bernal A, Meyer DJ, Rosenthal JJ, Artigas P. Importance of the Voltage Dependence of Cardiac Na/K ATPase Isozymes. Biophys J 2016; 109:1852-62. [PMID: 26536262 DOI: 10.1016/j.bpj.2015.09.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/11/2015] [Accepted: 09/10/2015] [Indexed: 11/25/2022] Open
Abstract
Cardiac cells express more than one isoform of the Na, K-ATPase (NKA), the heteromeric enzyme that creates the Na(+) and K(+) gradients across the plasmalemma. Cardiac isozymes contain one catalytic α-subunit isoform (α1, α2, or α3) associated with an auxiliary β-subunit isoform (β1 or β2). Past studies using biochemical approaches have revealed minor kinetic differences between isozymes formed by different α-β isoform combinations; these results make it difficult to understand the physiological requirement for multiple isoforms. In intact cells, however, NKA enzymes operate in a more complex environment, which includes a substantial transmembrane potential. We evaluated the voltage dependence of human cardiac NKA isozymes expressed in Xenopus oocytes, and of native NKA isozymes in rat ventricular myocytes, using normal mammalian physiological concentrations of Na(+)o and K(+)o. We demonstrate that although α1 and α3 pumps are functional at all physiologically relevant voltages, α2β1 pumps and α2β2 pumps are inhibited by ∼75% and ∼95%, respectively, at resting membrane potentials, and only activate appreciably upon depolarization. Furthermore, phospholemman (FXYD1) inhibits pump function without significantly altering the pump's voltage dependence. Our observations provide a simple explanation for the physiological relevance of the α2 subunit (∼20% of total α subunits in rat ventricle): they act as a reserve and are recruited into action for extra pumping during the long-lasting cardiac action potential, where most of the Na(+) entry occurs. This strong voltage dependence of α2 pumps also helps explain how cardiotonic steroids, which block NKA pumps, can be a beneficial treatment for heart failure: by only inhibiting the α2 pumps, they selectively reduce NKA activity during the cardiac action potential, leading to an increase in systolic Ca(2+), due to reduced extrusion through the Na/Ca exchanger, without affecting resting Na(+) and Ca(2+) concentrations.
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Affiliation(s)
- Christopher M Stanley
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Dominique G Gagnon
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas; Department of Physics, Texas Tech University, Lubbock, Texas
| | - Adam Bernal
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Dylan J Meyer
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Joshua J Rosenthal
- Universidad de Puerto Rico, Recinto de Ciencias Médicas, Instituto de Neurobiología, San Juan, Puerto Rico
| | - Pablo Artigas
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas.
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15
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de Waart DR, Naik J, Utsunomiya KS, Duijst S, Ho-Mok K, Bolier AR, Hiralall J, Bull LN, Bosma PJ, Oude Elferink RP, Paulusma CC. ATP11C targets basolateral bile salt transporter proteins in mouse central hepatocytes. Hepatology 2016; 64:161-74. [PMID: 26926206 PMCID: PMC5266587 DOI: 10.1002/hep.28522] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 02/25/2016] [Indexed: 12/16/2022]
Abstract
UNLABELLED ATP11C is a homolog of ATP8B1, both of which catalyze the transport of phospholipids in biological membranes. Mutations in ATP8B1 cause progressive familial intrahepatic cholestasis type1 in humans, which is characterized by a canalicular cholestasis. Mice deficient in ATP11C are characterized by a conjugated hyperbilirubinemia and an unconjugated hypercholanemia. Here, we have studied the hypothesis that ATP11C deficiency interferes with basolateral uptake of unconjugated bile salts, a process mediated by organic anion-transporting polypeptide (OATP) 1B2. ATP11C localized to the basolateral membrane of central hepatocytes in the liver lobule of control mice. In ATP11C-deficient mice, plasma total bilirubin levels were 6-fold increased, compared to control, of which ∼65% was conjugated and ∼35% unconjugated. Plasma total bile salts were 10-fold increased and were mostly present as unconjugated species. Functional studies in ATP11C-deficient mice indicated that hepatic uptake of unconjugated bile salts was strongly impaired whereas uptake of conjugated bile salts was unaffected. Western blotting and immunofluorescence analysis demonstrated near absence of basolateral bile salt uptake transporters OATP1B2, OATP1A1, OATP1A4, and Na(+) -taurocholate-cotransporting polypeptide only in central hepatocytes of ATP11C-deficient liver. In vivo application of the proteasome inhibitor, bortezomib, partially restored expression of these proteins, but not their localization. Furthermore, we observed post-translational down-regulation of ATP11C protein in livers from cholestatic mice, which coincided with reduced OATP1B2 levels. CONCLUSIONS ATP11C is essential for basolateral membrane localization of multiple bile salt transport proteins in central hepatocytes and may act as a gatekeeper to prevent hepatic bile salt overload. Conjugated hyperbilirubinemia and unconjugated hypercholanemia and loss of OATP expression in ATP11C-deficient liver strongly resemble the characteristics of Rotor syndrome, suggesting that mutations in ATP11C can predispose to Rotor syndrome. (Hepatology 2016;64:161-174).
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Affiliation(s)
- Dirk R. de Waart
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Jyoti Naik
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Suzanne Duijst
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Kam Ho-Mok
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - A. Ruth Bolier
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Johan Hiralall
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Laura N. Bull
- Liver Center Laboratory, Department of Medicine, and Institute for Human Genetics, University of California San Francisco, San Francisco, CA
| | - Piter J. Bosma
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Ronald P.J. Oude Elferink
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Coen C. Paulusma
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
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16
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The phospholipid flippase ATP8B1 mediates apical localization of the cystic fibrosis transmembrane regulator. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2280-8. [PMID: 27301931 DOI: 10.1016/j.bbamcr.2016.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/10/2016] [Indexed: 11/23/2022]
Abstract
Progressive familial intrahepatic cholestasis type 1 (PFIC1) is caused by mutations in the gene encoding the phospholipid flippase ATP8B1. Apart from severe cholestatic liver disease, many PFIC1 patients develop extrahepatic symptoms characteristic of cystic fibrosis (CF), such as pulmonary infection, sweat gland dysfunction and failure to thrive. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel essential for epithelial fluid transport. Previously it was shown that CFTR transcript levels were strongly reduced in livers of PFIC1 patients. Here we have investigated the hypothesis that ATP8B1 is important for proper CFTR expression and function. We analyzed CFTR expression in ATP8B1-depleted intestinal and pulmonary epithelial cell lines and assessed CFTR function by measuring short-circuit currents across transwell-grown ATP8B1-depleted intestinal T84 cells and by a genetically-encoded fluorescent chloride sensor. In addition, we studied CFTR surface expression upon induction of CFTR transcription. We show that CFTR protein levels are strongly reduced in the apical membrane of human ATP8B1-depleted intestinal and pulmonary epithelial cell lines, a phenotype that coincided with reduced CFTR activity. Apical membrane insertion upon induction of ectopically-expressed CFTR was strongly impaired in ATP8B1-depleted cells. We conclude that ATP8B1 is essential for correct apical localization of CFTR in human intestinal and pulmonary epithelial cells, and that impaired CFTR localization underlies some of the extrahepatic phenotypes observed in ATP8B1 deficiency.
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Stern WM, Desikan M, Hoad D, Jaffer F, Strigaro G, Sander JW, Rothwell JC, Sisodiya SM. Spontaneously Fluctuating Motor Cortex Excitability in Alternating Hemiplegia of Childhood: A Transcranial Magnetic Stimulation Study. PLoS One 2016; 11:e0151667. [PMID: 26999520 PMCID: PMC4801356 DOI: 10.1371/journal.pone.0151667] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 03/02/2016] [Indexed: 01/01/2023] Open
Abstract
Background Alternating hemiplegia of childhood is a very rare and serious neurodevelopmental syndrome; its genetic basis has recently been established. Its characteristic features include typically-unprovoked episodes of hemiplegia and other transient or more persistent neurological abnormalities. Methods We used transcranial magnetic stimulation to assess the effect of the condition on motor cortex neurophysiology both during and between attacks of hemiplegia. Nine people with alternating hemiplegia of childhood were recruited; eight were successfully tested using transcranial magnetic stimulation to study motor cortex excitability, using single and paired pulse paradigms. For comparison, data from ten people with epilepsy but not alternating hemiplegia, and ten healthy controls, were used. Results One person with alternating hemiplegia tested during the onset of a hemiplegic attack showed progressively diminishing motor cortex excitability until no response could be evoked; a second person tested during a prolonged bilateral hemiplegic attack showed unusually low excitability. Three people tested between attacks showed asymptomatic variation in cortical excitability, not seen in controls. Paired pulse paradigms, which probe intracortical inhibitory and excitatory circuits, gave results similar to controls. Conclusions We report symptomatic and asymptomatic fluctuations in motor cortex excitability in people with alternating hemiplegia of childhood, not seen in controls. We propose that such fluctuations underlie hemiplegic attacks, and speculate that the asymptomatic fluctuation we detected may be useful as a biomarker for disease activity.
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Affiliation(s)
- William M. Stern
- NIHR University College London Hospitals Biomedical Research Centre, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom
- Epilepsy Society, Chalfont St Peter, SL9 0RJ, United Kingdom
| | - Mahalekshmi Desikan
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, United Kingdom
| | - Damon Hoad
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, United Kingdom
| | - Fatima Jaffer
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom
| | - Gionata Strigaro
- Department of Translational Medicine, Section of Neurology, University of Piemonte Orientale “A. Avogadro”, Novara, Italy
| | - Josemir W. Sander
- NIHR University College London Hospitals Biomedical Research Centre, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom
- Epilepsy Society, Chalfont St Peter, SL9 0RJ, United Kingdom
- Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
| | - John C. Rothwell
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, United Kingdom
| | - Sanjay M. Sisodiya
- NIHR University College London Hospitals Biomedical Research Centre, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom
- Epilepsy Society, Chalfont St Peter, SL9 0RJ, United Kingdom
- * E-mail:
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18
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van Loon EPM, Pulskens WP, van der Hagen EAE, Lavrijsen M, Vervloet MG, van Goor H, Bindels RJM, Hoenderop JGJ. Shedding of klotho by ADAMs in the kidney. Am J Physiol Renal Physiol 2015; 309:F359-68. [PMID: 26155844 DOI: 10.1152/ajprenal.00240.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 07/01/2015] [Indexed: 11/22/2022] Open
Abstract
The anti-aging gene klotho plays an important role in Ca(2+) and phosphate homeostasis. Membrane-bound klotho is an essential coreceptor for fibroblast growth factor-23 and can be cleaved by proteases, including a disintegrin and metalloproteinase (ADAM)10 and ADAM17. Cleavage of klotho occurs at a site directly above the plasma membrane (α-cut) or between the KL1 and KL2 domain (β-cut), resulting in soluble full-length klotho or KL1 and KL2 fragments, respectively. The aim of the present study was to gain insights into the mechanisms behind klotho cleavage processes in the kidney. Klotho shedding was demonstrated using a Madin-Darby canine kidney cell line stably expressing klotho and human embryonic kidney-293 cells transiently transfected with klotho. Here, we report klotho expression on both the basolateral and apical membrane, with a higher abundance of klotho at the apical membrane and in the apical media. mRNA expression of ADAM17 and klotho were enriched in mouse distal convoluted and connecting tubules. In vitro ADAM/matrix metalloproteinase inhibition by TNF484 resulted in a concentration-dependent inhibition of the α-cut, with a less specific effect on β-cut shedding. In vivo TNF484 treatment in wild-type mice did not change urinary klotho levels. However, ADAM/matrix metalloproteinase inhibition did increase renal and duodenal mRNA expression of phosphate transporters, whereas serum phosphate levels were significantly decreased. In conclusion, our data show that renal cells preferentially secrete klotho to the apical side and suggest that ADAMs are responsible for α-cut cleavage.
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Affiliation(s)
- Ellen P M van Loon
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Wilco P Pulskens
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Eline A E van der Hagen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marla Lavrijsen
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Marc G Vervloet
- Department of Nephrology, VU University Medical Center, Amsterdam, The Netherlands; and
| | - Harry van Goor
- Department of Pathology and Medical Biology, University Medical Center Groningen, Groningen, The Netherlands
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joost G J Hoenderop
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands;
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19
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Vedovato N, Gadsby DC. Route, mechanism, and implications of proton import during Na+/K+ exchange by native Na+/K+-ATPase pumps. ACTA ACUST UNITED AC 2014; 143:449-64. [PMID: 24688018 PMCID: PMC3971657 DOI: 10.1085/jgp.201311148] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Na+/K+ pump is a hybrid transporter that can also import protons at physiological K+ and Na+ concentrations. A single Na+/K+-ATPase pumps three Na+ outwards and two K+ inwards by alternately exposing ion-binding sites to opposite sides of the membrane in a conformational sequence coupled to pump autophosphorylation from ATP and auto-dephosphorylation. The larger flow of Na+ than K+ generates outward current across the cell membrane. Less well understood is the ability of Na+/K+ pumps to generate an inward current of protons. Originally noted in pumps deprived of external K+ and Na+ ions, as inward current at negative membrane potentials that becomes amplified when external pH is lowered, this proton current is generally viewed as an artifact of those unnatural conditions. We demonstrate here that this inward current also flows at physiological K+ and Na+ concentrations. We show that protons exploit ready reversibility of conformational changes associated with extracellular Na+ release from phosphorylated Na+/K+ pumps. Reversal of a subset of these transitions allows an extracellular proton to bind an acidic side chain and to be subsequently released to the cytoplasm. This back-step of phosphorylated Na+/K+ pumps that enables proton import is not required for completion of the 3 Na+/2 K+ transport cycle. However, the back-step occurs readily during Na+/K+ transport when external K+ ion binding and occlusion are delayed, and it occurs more frequently when lowered extracellular pH raises the probability of protonation of the externally accessible carboxylate side chain. The proton route passes through the Na+-selective binding site III and is distinct from the principal pathway traversed by the majority of transported Na+ and K+ ions that passes through binding site II. The inferred occurrence of Na+/K+ exchange and H+ import during the same conformational cycle of a single molecule identifies the Na+/K+ pump as a hybrid transporter. Whether Na+/K+ pump–mediated proton inflow may have any physiological or pathophysiological significance remains to be clarified.
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Affiliation(s)
- Natascia Vedovato
- The Laboratory of Cardiac/Membrane Physiology, The Rockefeller University, New York, NY 10065
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20
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Gozalpour E, Greupink R, Bilos A, Verweij V, van den Heuvel JJMW, Masereeuw R, Russel FGM, Koenderink JB. Convallatoxin: a new P-glycoprotein substrate. Eur J Pharmacol 2014; 744:18-27. [PMID: 25264938 DOI: 10.1016/j.ejphar.2014.09.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/18/2014] [Accepted: 09/19/2014] [Indexed: 02/08/2023]
Abstract
Digitalis-like compounds (DLCs), such as digoxin and digitoxin that are derived from digitalis species, are currently used to treat heart failure and atrial fibrillation, but have a narrow therapeutic index. Drug-drug interactions at the transporter level are frequent causes of DLCs toxicity. P-glycoprotein (P-gp, ABCB1) is the primary transporter of digoxin and its inhibitors influence pharmacokinetics and disposition of digoxin in the human body; however, the involvement of P-gp in the disposition of other DLCs is currently unknown. In present study, the transport of fourteen DLCs by human P-gp was studied using membrane vesicles originating from human embryonic kidney (HEK293) cells overexpressing P-gp. DLCs were quantified by liquid chromatography-mass spectrometry (LC-MS). The Lily of the Valley toxin, convallatoxin, was identified as a P-gp substrate (Km: 1.1±0.2 mM) in the vesicular assay. Transport of convallatoxin by P-gp was confirmed in rat in vivo, in which co-administration with the P-gp inhibitor elacridar, resulted in increased concentrations in brain and kidney cortex. To address the interaction of convallatoxin with P-gp on a molecular level, the effect of nine alanine mutations was compared with the substrate N-methyl quinidine (NMQ). Phe343 appeared to be more important for transport of NMQ than convallatoxin, while Val982 was particularly relevant for convallatoxin transport. We identified convallatoxin as a new P-gp substrate and recognized Val982 as an important amino acid involved in its transport. These results contribute to a better understanding of the interaction of DLCs with P-gp.
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Affiliation(s)
- Elnaz Gozalpour
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Rick Greupink
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Albert Bilos
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Vivienne Verweij
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Jeroen J M W van den Heuvel
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Rosalinde Masereeuw
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Frans G M Russel
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Jan B Koenderink
- Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
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21
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van der Mark VA, de Waart DR, Ho-Mok KS, Tabbers MM, Voogt HW, Oude Elferink RPJ, Knisely AS, Paulusma CC. The lipid flippase heterodimer ATP8B1-CDC50A is essential for surface expression of the apical sodium-dependent bile acid transporter (SLC10A2/ASBT) in intestinal Caco-2 cells. Biochim Biophys Acta Mol Basis Dis 2014; 1842:2378-86. [PMID: 25239307 DOI: 10.1016/j.bbadis.2014.09.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/04/2014] [Accepted: 09/05/2014] [Indexed: 12/12/2022]
Abstract
Deficiency of the phospholipid flippase ATPase, aminophospholipid transporter, class I, type 8B, member 1 (ATP8B1) causes progressive familial intrahepatic cholestasis type 1 (PFIC1) and benign recurrent intrahepatic cholestasis type 1 (BRIC1). Apart from cholestasis, many patients also suffer from diarrhea of yet unknown etiology. Here we have studied the hypothesis that intestinal ATP8B1 deficiency results in bile salt malabsorption as a possible cause of PFIC1/BRIC1 diarrhea. Bile salt transport was studied in ATP8B1-depleted intestinal Caco-2 cells. Apical membrane localization was studied by a biotinylation approach. Fecal bile salt and electrolyte contents were analyzed in stool samples of PFIC1 patients, of whom some had undergone biliary diversion or liver transplantation. Bile salt uptake by the apical sodium-dependent bile salt transporter solute carrier family 10 (sodium/bile acid cotransporter), member 2 (SLC10A2) was strongly impaired in ATP8B1-depleted Caco-2 cells. The reduced SLC10A2 activity coincided with strongly reduced apical membrane localization, which was caused by impaired apical membrane insertion of SLC10A2. Moreover, we show that endogenous ATP8B1 exists in a functional heterodimer with transmembrane protein 30A (CDC50A) in Caco-2 cells. Analyses of stool samples of post-transplant PFIC1 patients demonstrated that bile salt content was not changed, whereas sodium and chloride concentrations were elevated and potassium levels were decreased. The ATP8B1-CDC50A heterodimer is essential for the apical localization of SLC10A2 in Caco-2 cells. Diarrhea in PFIC1/BRIC1 patients has a secretory origin to which SLC10A2 deficiency may contribute. This results in elevated luminal bile salt concentrations and consequent enhanced electrolyte secretion and/or reduced electrolyte resorption.
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Affiliation(s)
- Vincent A van der Mark
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands.
| | - D Rudi de Waart
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Kam S Ho-Mok
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - Merit M Tabbers
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands
| | - Heleen W Voogt
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital, Academic Medical Center, Amsterdam, The Netherlands
| | - Ronald P J Oude Elferink
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
| | - A S Knisely
- Institute of Liver Studies, King's College Hospital, London, UK
| | - Coen C Paulusma
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands
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22
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A missense variant of the ATP1A2 gene is associated with a novel phenotype of progressive sensorineural hearing loss associated with migraine. Eur J Hum Genet 2014; 23:639-45. [PMID: 25138102 DOI: 10.1038/ejhg.2014.154] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2013] [Revised: 06/25/2014] [Accepted: 07/02/2014] [Indexed: 11/08/2022] Open
Abstract
Hereditary sensorineural hearing loss is an extremely clinical and genetic heterogeneous disorder in humans. Especially, syndromic hearing loss is subdivided by combinations of various phenotypes, and each subtype is related to different genes. We present a new form of progressive hearing loss with migraine found to be associated with a variant in the ATP1A2 gene. The ATP1A2 gene has been reported as the major genetic cause of familial migraine by several previous studies. A Korean family presenting progressive hearing loss with migraine was ascertained. The affected members did not show any aura or other neurologic symptoms during migraine attacks, indicating on a novel phenotype of syndromic hearing loss. To identify the causative gene, linkage analysis and whole-exome sequencing were performed. A novel missense variant, c.571G>A (p.(Val191Met)), was identified in the ATP1A2 gene that showed co-segregation with the phenotype in the family. In silico studies suggest that this variant causes a change in hydrophobic interactions and thereby slightly destabilize the A-domain of Na(+)/K(+)-ATPase. However, functional studies failed to show any effect of the p.(Val191Met) substitution on the catalytic rate of this enzyme. We describe a new phenotype of progressive hearing loss with migraine associated with a variant in the ATP1A2 gene. This study suggests that a variant in Na(+)/K(+)-ATPase can be involved in both migraine and hearing loss.
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23
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Weigand KM, Messchaert M, Swarts HG, Russel FG, Koenderink JB. Alternating Hemiplegia of Childhood mutations have a differential effect on Na+,K+-ATPase activity and ouabain binding. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1010-6. [DOI: 10.1016/j.bbadis.2014.03.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/26/2014] [Accepted: 03/02/2014] [Indexed: 10/25/2022]
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24
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Biochemical characterization of sporadic/familial hemiplegic migraine mutations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1693-700. [DOI: 10.1016/j.bbamem.2014.03.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/26/2014] [Accepted: 03/27/2014] [Indexed: 12/13/2022]
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25
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Heinzen EL, Arzimanoglou A, Brashear A, Clapcote SJ, Gurrieri F, Goldstein DB, Jóhannesson SH, Mikati MA, Neville B, Nicole S, Ozelius LJ, Poulsen H, Schyns T, Sweadner KJ, van den Maagdenberg A, Vilsen B. Distinct neurological disorders with ATP1A3 mutations. Lancet Neurol 2014; 13:503-14. [PMID: 24739246 DOI: 10.1016/s1474-4422(14)70011-0] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Genetic research has shown that mutations that modify the protein-coding sequence of ATP1A3, the gene encoding the α3 subunit of Na(+)/K(+)-ATPase, cause both rapid-onset dystonia parkinsonism and alternating hemiplegia of childhood. These discoveries link two clinically distinct neurological diseases to the same gene, however, ATP1A3 mutations are, with one exception, disease-specific. Although the exact mechanism of how these mutations lead to disease is still unknown, much knowledge has been gained about functional consequences of ATP1A3 mutations using a range of in-vitro and animal model systems, and the role of Na(+)/K(+)-ATPases in the brain. Researchers and clinicians are attempting to further characterise neurological manifestations associated with mutations in ATP1A3, and to build on the existing molecular knowledge to understand how specific mutations can lead to different diseases.
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Affiliation(s)
- Erin L Heinzen
- Center for Human Genome Variation, Duke University, School of Medicine, Durham, NC, USA; Department of Medicine, Section of Medical Genetics, Duke University, School of Medicine, Durham, NC, USA.
| | - Alexis Arzimanoglou
- Epilepsy, Sleep and Pediatric Neurophysiology Department, HFME, University Hospitals of Lyon, France; Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, UMR 5292, INSERM U1028, Lyon, France
| | - Allison Brashear
- Department of Neurology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | | | - Fiorella Gurrieri
- Istituto di Genetica Medica, Università Cattolica S Cuore, Rome, Italy
| | - David B Goldstein
- Center for Human Genome Variation, Duke University, School of Medicine, Durham, NC, USA; Department of Molecular Genetics and Microbiology, Duke University, School of Medicine, Durham, NC, USA
| | | | - Mohamad A Mikati
- Division of Pediatric Neurology, Duke University, School of Medicine, Durham, NC, USA; Department of Neurobiology, Duke University, School of Medicine, Durham, NC, USA
| | - Brian Neville
- Institute of Child Health, University College London, London, UK
| | - Sophie Nicole
- Institut National de la Santé et de la Recherche Médicale, U975, Centre de Recherche de l'Institut du Cerveau et de la Moelle, Paris, France; Centre National de la Recherche Scientifique, UMR7225, Paris, France; Université Pierre et Marie Curie Paris VI, UMRS975, Paris, France
| | - Laurie J Ozelius
- Department of Genetics and Genomic Sciences and Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hanne Poulsen
- Danish Research Institute for Translational Neuroscience, Nordic-EMBL Partnership of Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
| | - Tsveta Schyns
- European Network for Research on Alternating Hemiplegia (ENRAH), Brussels, Belgium
| | | | - Arn van den Maagdenberg
- Department of Human Genetics and Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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26
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Spiller S, Friedrich T. Functional analysis of human Na +/K +-ATPase familial or sporadic hemiplegic migraine mutations expressed in Xenopus oocytes. World J Biol Chem 2014; 5:240-253. [PMID: 24921013 PMCID: PMC4050117 DOI: 10.4331/wjbc.v5.i2.240] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 03/13/2014] [Accepted: 04/11/2014] [Indexed: 02/05/2023] Open
Abstract
AIM: Functional characterization of ATP1A2 mutations that are related to familial or sporadic hemiplegic migraine (FHM2, SHM).
METHODS: cRNA of human Na+/K+-ATPase α2- and β1-subunits were injected in Xenopus laevis oocytes. FHM2 or SHM mutations of residues located in putative α/β interaction sites or in the α2-subunit’s C-terminal region were investigated. Mutants were analyzed by the two-electrode voltage-clamp (TEVC) technique on Xenopus oocytes. Stationary K+-induced Na+/K+ pump currents were measured, and the voltage dependence of apparent K+ affinity was investigated. Transient currents were recorded as ouabain-sensitive currents in Na+ buffers to analyze kinetics and voltage-dependent pre-steady state charge translocations. The expression of constructs was verified by preparation of plasma membrane and total membrane fractions of cRNA-injected oocytes.
RESULTS: Compared to the wild-type enzyme, the mutants G900R and E902K showed no significant differences in the voltage dependence of K+-induced currents, and analysis of the transient currents indicated that the extracellular Na+ affinity was not affected. Mutant G855R showed no pump activity detectable by TEVC. Also for L994del and Y1009X, pump currents could not be recorded. Analysis of the plasma and total membrane fractions showed that the expressed proteins were not or only minimally targeted to the plasma membrane. Whereas the mutation K1003E had no impact on K+ interaction, D999H affected the voltage dependence of K+-induced currents. Furthermore, kinetics of the transient currents was altered compared to the wild-type enzyme, and the apparent affinity for extracellular Na+ was reduced.
CONCLUSION: The investigated FHM2/SHM mutations influence protein function differently depending on the structural impact of the mutated residue.
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27
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Jansen J, Schophuizen CMS, Wilmer MJ, Lahham SHM, Mutsaers HAM, Wetzels JFM, Bank RA, van den Heuvel LP, Hoenderop JG, Masereeuw R. A morphological and functional comparison of proximal tubule cell lines established from human urine and kidney tissue. Exp Cell Res 2014; 323:87-99. [PMID: 24560744 DOI: 10.1016/j.yexcr.2014.02.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 01/22/2014] [Accepted: 02/09/2014] [Indexed: 10/25/2022]
Abstract
Promising renal replacement therapies include the development of a bioartificial kidney using functional human kidney cell models. In this study, human conditionally immortalized proximal tubular epithelial cell (ciPTEC) lines originating from kidney tissue (ciPTEC-T1 and ciPTEC-T2) were compared to ciPTEC previously isolated from urine (ciPTEC-U). Subclones of all ciPTEC isolates formed tight cell layers on Transwell inserts as determined by transepithelial resistance, inulin diffusion, E-cadherin expression and immunocytochemisty. Extracellular matrix genes collagen I and -IV α1 were highly present in both kidney tissue derived matured cell lines (p<0.001) compared to matured ciPTEC-U, whereas matured ciPTEC-U showed a more pronounced fibronectin I and laminin 5 gene expression (p<0.01 and p<0.05, respectively). Expression of the influx carrier Organic Cation Transporter 2 (OCT-2), and the efflux pumps P-glycoprotein (P-gp), Multidrug Resistance Protein 4 (MRP4) and Breast Cancer Resistance Protein (BCRP) were confirmed in the three cell lines using real-time PCR and Western blotting. The activities of OCT-2 and P-gp were sensitive to specific inhibition in all models (p<0.001). The highest activity of MRP4 and BCRP was demonstrated in ciPTEC-U (p<0.05). Finally, active albumin reabsorption was highest in ciPTEC-T2 (p<0.001), while Na(+)-dependent phosphate reabsorption was most abundant in ciPTEC-U (p<0.01). In conclusion, ciPTEC established from human urine or kidney tissue display comparable functional PTEC specific transporters and physiological characteristics, providing ideal human tools for bioartificial kidney development.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B, Member 1/biosynthesis
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP Binding Cassette Transporter, Subfamily G, Member 2
- ATP-Binding Cassette Transporters/biosynthesis
- ATP-Binding Cassette Transporters/metabolism
- Bioartificial Organs
- Cadherins/biosynthesis
- Cell Adhesion Molecules/biosynthesis
- Cell Culture Techniques
- Cell Line
- Collagen Type I/biosynthesis
- Collagen Type I/metabolism
- Fibronectins/biosynthesis
- Humans
- Inulin/metabolism
- Kidney Tubules, Proximal/cytology
- Kidneys, Artificial
- Multidrug Resistance-Associated Proteins/biosynthesis
- Multidrug Resistance-Associated Proteins/metabolism
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/metabolism
- Octamer Transcription Factor-2/antagonists & inhibitors
- Octamer Transcription Factor-2/biosynthesis
- Octamer Transcription Factor-2/metabolism
- Tissue Engineering
- Transendothelial and Transepithelial Migration/physiology
- Urine/cytology
- Kalinin
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Affiliation(s)
- J Jansen
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Pediatrics, Radboud University Medical Center, The Netherlands
| | - C M S Schophuizen
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Pediatrics, Radboud University Medical Center, The Netherlands
| | - M J Wilmer
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - S H M Lahham
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - H A M Mutsaers
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Pediatrics, Radboud University Medical Center, The Netherlands
| | - J F M Wetzels
- Department of Nephrology, Radboud University Medical Center, The Netherlands
| | - R A Bank
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - L P van den Heuvel
- Department of Pediatrics, Radboud University Medical Center, The Netherlands; Department of Pediatrics, Catholic University Leuven, Leuven, Belgium
| | - J G Hoenderop
- Department of Physiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - R Masereeuw
- Department of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands.
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28
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Familial hemiplegic migraine mutations affect Na,K-ATPase domain interactions. Biochim Biophys Acta Mol Basis Dis 2013; 1832:2173-9. [PMID: 23954377 DOI: 10.1016/j.bbadis.2013.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 08/07/2013] [Accepted: 08/08/2013] [Indexed: 11/20/2022]
Abstract
Familial hemiplegic migraine (FHM) is a monogenic variant of migraine with aura. One of the three known causative genes, ATP1A2, which encodes the α2 isoform of Na,K-ATPase, causes FHM type 2 (FHM2). Over 50 FHM2 mutations have been reported, but most have not been characterized functionally. Here we study the molecular mechanism of Na,K-ATPase α2 missense mutations. Mutants E700K and P786L inactivate or strongly reduce enzyme activity. Glutamic acid 700 is located in the phosphorylation (P) domain and the mutation most likely disrupts the salt bridge with Lysine 35, thereby destabilizing the interaction with the actuator (A) domain. Mutants G900R and E902K are present in the extracellular loop at the interface of the α and β subunit. Both mutants likely hamper the interaction between these subunits and thereby decrease enzyme activity. Mutants E174K, R548C and R548H reduce the Na(+) and increase the K(+) affinity. Glutamic acid 174 is present in the A domain and might form a salt bridge with Lysine 432 in the nucleotide binding (N) domain, whereas Arginine 548, which is located in the N domain, forms a salt bridge with Glutamine 219 in the A domain. In the catalytic cycle, the interactions of the A and N domains affect the K(+) and Na(+) affinities, as observed with these mutants. Functional consequences were not observed for ATP1A2 mutations found in two sporadic hemiplegic migraine cases (Y9N and R879Q) and in migraine without aura (R51H and C702Y).
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29
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Dürr KL, Tavraz NN, Spiller S, Friedrich T. Measuring cation transport by Na,K- and H,K-ATPase in Xenopus oocytes by atomic absorption spectrophotometry: an alternative to radioisotope assays. J Vis Exp 2013:e50201. [PMID: 23462593 DOI: 10.3791/50201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Whereas cation transport by the electrogenic membrane transporter Na(+),K(+)-ATPase can be measured by electrophysiology, the electroneutrally operating gastric H(+),K(+)-ATPase is more difficult to investigate. Many transport assays utilize radioisotopes to achieve a sufficient signal-to-noise ratio, however, the necessary security measures impose severe restrictions regarding human exposure or assay design. Furthermore, ion transport across cell membranes is critically influenced by the membrane potential, which is not straightforwardly controlled in cell culture or in proteoliposome preparations. Here, we make use of the outstanding sensitivity of atomic absorption spectrophotometry (AAS) towards trace amounts of chemical elements to measure Rb(+) or Li(+) transport by Na(+),K(+)- or gastric H(+),K(+)-ATPase in single cells. Using Xenopus oocytes as expression system, we determine the amount of Rb(+) (Li(+)) transported into the cells by measuring samples of single-oocyte homogenates in an AAS device equipped with a transversely heated graphite atomizer (THGA) furnace, which is loaded from an autosampler. Since the background of unspecific Rb(+) uptake into control oocytes or during application of ATPase-specific inhibitors is very small, it is possible to implement complex kinetic assay schemes involving a large number of experimental conditions simultaneously, or to compare the transport capacity and kinetics of site-specifically mutated transporters with high precision. Furthermore, since cation uptake is determined on single cells, the flux experiments can be carried out in combination with two-electrode voltage-clamping (TEVC) to achieve accurate control of the membrane potential and current. This allowed e.g. to quantitatively determine the 3Na(+)/2K(+) transport stoichiometry of the Na(+),K(+)-ATPase and enabled for the first time to investigate the voltage dependence of cation transport by the electroneutrally operating gastric H(+),K(+)-ATPase. In principle, the assay is not limited to K(+)-transporting membrane proteins, but it may work equally well to address the activity of heavy or transition metal transporters, or uptake of chemical elements by endocytotic processes.
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30
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Folmer DE, Mok KS, de Wee SW, Duijst S, Hiralall JK, Seppen J, Oude Elferink RPJ, Paulusma CC. Cellular localization and biochemical analysis of mammalian CDC50A, a glycosylated β-subunit for P4 ATPases. J Histochem Cytochem 2012; 60:205-18. [PMID: 22253360 DOI: 10.1369/0022155411435705] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CDC50 proteins are β-subunits for P4 ATPases, which upon heterodimerization form a functional phospholipid translocation complex. Emerging evidence in mouse models and men links mutations in P4 ATPase genes with human disease. This study analyzed the tissue distribution and cellular localization of CDC50A, the most abundant and ubiquitously expressed CDC50 homologue in the mouse. The authors have raised antibodies that detect mouse and human CDC50A and studied CDC50A localization and glycosylation status in mouse liver cells. CDC50A is a terminal-glycosylated glycoprotein and is expressed in hepatocytes and liver sinusoidal endothelial cells, where it resides in detergent-resistant membranes. In pancreas and stomach, CDC50A localized to secretory vesicles, whereas in the kidney, CDC50A localized to the apical region of proximal convoluted tubules of the cortex. In WIF-B9 cells, CDC50A partially costains with the trans-Golgi network. Data suggest that CDC50A is present as a fully glycosylated protein in vivo, which presumes interaction with distinct P4 ATPases.
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Affiliation(s)
- Dineke E Folmer
- Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, Netherlands
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31
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Yu H, Ratheal I, Artigas P, Roux B. Molecular Mechanisms of K+ Selectivity in Na/K Pump. Aust J Chem 2012. [DOI: 10.1071/ch12026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The sodium–potassium (Na/K) pump plays an essential role in maintaining cell volume and secondary active transport of other solutes by establishing the Na+ and K+ concentration gradients across the plasma membrane of animal cells. The recently determined crystal structures of the Na/K pump to atomic resolution provide a new impetus to investigate molecular determinants governing the binding of Na+ and K+ ions and conformational transitions during the functional cycle. The pump cycle is generally described by the alternating access mechanism, in which the pump toggles between different conformational states, where ions can bind from either the intracellular or the extracellular side. However, important issues concerning the selectivity of the Na/K pump remain to be addressed. In particular, two out of the three binding sites are shared between Na+ and K+ and it is not clear how the protein is able to select K+ over Na+ when it is in the outwardly facing phosphorylated conformation (E2P), and Na+ over K+ when it is in the inwardly facing conformation (E1). In this review article, we will first briefly review the recent advancement in understanding the microscopic mechanism of K+ selectivity in the Na/K pump at the E2·Pi state and then outline the remaining challenges to be addressed about ion selectivity.
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32
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Yu H, Ratheal IM, Artigas P, Roux B. Protonation of key acidic residues is critical for the K⁺-selectivity of the Na/K pump. Nat Struct Mol Biol 2011; 18:1159-63. [PMID: 21909093 PMCID: PMC3190665 DOI: 10.1038/nsmb.2113] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2011] [Accepted: 07/04/2011] [Indexed: 12/25/2022]
Abstract
The sodium-potassium (Na/K) pump is a P-type ATPase that generates Na+ and K+ concentration gradients across the cell membrane. For each ATP molecule, the pump extrudes three Na+ and imports two K+ by alternating between outward- and inward-facing conformations that preferentially bind K+ or Na+, respectively. Remarkably, the selective K+ and Na+ binding sites share several residues, and how the pump is able to achieve the selectivity required for the functional cycle is unclear. Here, free energy perturbation molecular dynamics (FEP/MD) simulations based on the crystal structures of the Na/K pump in a K+-loaded state (E2·Pi) reveal that protonation of the high-field acidic side-chains involved in the binding sites is critical to achieve the proper K+ selectivity. This prediction is tested with electrophysiological experiments showing that the selectivity of the E2P state for K+ over Na+ is affected by extracellular pH.
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Affiliation(s)
- Haibo Yu
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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Folmer DE, van der Mark VA, Ho-Mok KS, Oude Elferink RPJ, Paulusma CC. Differential effects of progressive familial intrahepatic cholestasis type 1 and benign recurrent intrahepatic cholestasis type 1 mutations on canalicular localization of ATP8B1. Hepatology 2009; 50:1597-605. [PMID: 19731236 DOI: 10.1002/hep.23158] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
UNLABELLED Mutations in ATP8B1 cause progressive familial intrahepatic cholestasis type 1 (PFIC1) and benign recurrent intrahepatic cholestasis type 1 (BRIC1), forming a spectrum of cholestatic disease. Whereas PFIC1 is a progressive, endstage liver disease, BRIC1 patients suffer from episodic periods of cholestasis that resolve spontaneously. At present it is not clear how the type and location of the mutations relate to the clinical manifestations of PFIC1 and BRIC1. ATP8B1 localizes to the canalicular membrane of hepatocytes where it mediates the inward translocation of phosphatidylserine. ATP8B1 interacts with CDC50A, which is required for endoplasmic reticulum exit and plasma membrane localization. In this study we analyzed a panel of missense mutations causing PFIC1 (G308V, D554N, G1040R) or BRIC1 (D70N, I661T). In addition, we included two mutations that have been associated with intrahepatic cholestasis of pregnancy (ICP) (D70N, R867C). We examined the effect of these mutations on protein stability and interaction with CDC50A in Chinese hamster ovary cells, and studied the subcellular localization in WIF-B9 cells. Protein stability was reduced for three out of six mutations studied. Two out of three PFIC1 mutant proteins did not interact with CDC50A, whereas BRIC1/ICP mutants displayed reduced interaction. Importantly, none of the PFIC1 mutants were detectable in the canalicular membrane of WIF-B9 cells, whereas all BRIC1/ICP mutants displayed the same cellular staining pattern as wild-type ATP8B1. Our data indicate that PFIC1 mutations lead to the complete absence of canalicular expression, whereas in BRIC1/ICP residual protein is expressed in the canalicular membrane. CONCLUSION These data provide an explanation for the difference in severity between the phenotypes of PFIC1 and BRIC1.
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Affiliation(s)
- Dineke E Folmer
- AMC Liver Center, Academic Medical Center, Amsterdam, The Netherlands
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Cairo ER, Swarts HGP, Wilmer MJG, Willems PHGM, Levtchenko EN, De Pont JJHHM, Koenderink JB. FXYD2 and Na,K-ATPase expression in isolated human proximal tubular cells: disturbed upregulation on renal hypomagnesemia? J Membr Biol 2009; 231:117-24. [PMID: 19865785 PMCID: PMC2776943 DOI: 10.1007/s00232-009-9210-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 10/08/2009] [Indexed: 11/05/2022]
Abstract
Autosomal dominant renal hypomagnesemia (OMIM 154020), associated with hypocalciuria, has been linked to a 121G to A mutation in the FXYD2 gene. To gain insight into the molecular mechanisms linking this mutation to the clinical phenotype, we studied isolated proximal tubular cells from urine of a patient and a healthy subject. Cells were immortalized and used to assess the effects of hypertonicity-induced overexpression of FXYD2 on amount, activity and apparent affinities for Na+, K+ and ATP of Na,K-ATPase. Both cell lines expressed mRNA for FXYD2a and FXYD2b, and patient cells contained both the wild-type and mutated codons. FXYD2 protein expression was lower in patient cells and could be increased in both cell lines upon culturing in hyperosmotic medium but to a lesser extent in patient cells. Similarly, hyperosmotic culturing increased Na,K-ATPase protein expression and ATP hydrolyzing activity but, again, to a lesser extent in patient cells. Apparent affinities of Na,K-ATPase for Na+, K+ and ATP did not differ between patient and control cells or after hyperosmotic induction. We conclude that human proximal tubular cells respond to a hyperosmotic challenge with an increase in FXYD2 and Na,K-ATPase protein expression, though to a smaller absolute extent in patient cells.
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Affiliation(s)
- Edinio R Cairo
- Department of Biochemistry, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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Altered Na+ transport after an intracellular alpha-subunit deletion reveals strict external sequential release of Na+ from the Na/K pump. Proc Natl Acad Sci U S A 2009; 106:15507-12. [PMID: 19706387 DOI: 10.1073/pnas.0903752106] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Na/K pump actively exports 3 Na(+) in exchange for 2 K(+) across the plasmalemma of animal cells. As in other P-type ATPases, pump function is more effective when the relative affinity for transported ions is altered as the ion binding sites alternate between opposite sides of the membrane. Deletion of the five C-terminal residues from the alpha-subunit diminishes internal Na(+) (Na(i)(+)) affinity approximately 25-fold [Morth et al. (2007) Nature 450:1043-1049]. Because external Na(+) (Na(o)(+)) binding is voltage-dependent, we studied the reactions involving this process by using two-electrode and inside-out patch voltage clamp in normal and truncated (DeltaKESYY) Xenopus-alpha1 pumps expressed in oocytes. We observed that DeltaKESYY (i) decreased both Na(o)(+) and Na(i)(+) apparent affinities in the absence of K(o)(+), and (ii) did not affect apparent Na(o)(+) affinity at high K(o)(+). These results support a model of strict sequential external release of Na(+) ions, where the Na(+)-exclusive site releases Na(+) before the sites shared with K(+) and the DeltaKESYY deletion only reduces Na(o)(+) affinity at the shared sites. Moreover, at nonsaturating K(o)(+), DeltaKESYY induced an inward flow of Na(+) through Na/K pumps at negative potentials. Guanidinium(+) can also permeate truncated pumps, whereas N-methyl-D-glucamine cannot. Because guanidinium(o)(+) can also traverse normal Na/K pumps in the absence of both Na(o)(+) and K(o)(+) and can also inhibit Na/K pump currents in a Na(+)-like voltage-dependent manner, we conclude that the normal pathway transited by the first externally released Na(+) is large enough to accommodate guanidinium(+).
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Tavraz NN, Friedrich T, Dürr KL, Koenderink JB, Bamberg E, Freilinger T, Dichgans M. Diverse functional consequences of mutations in the Na+/K+-ATPase alpha2-subunit causing familial hemiplegic migraine type 2. J Biol Chem 2008; 283:31097-106. [PMID: 18728015 DOI: 10.1074/jbc.m802771200] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Mutations in ATP1A2, the gene coding for the Na(+)/K(+)-ATPase alpha(2)-subunit, are associated with both familial hemiplegic migraine and sporadic cases of hemiplegic migraine. In this study, we examined the functional properties of 11 ATP1A2 mutations associated with familial or sporadic hemiplegic migraine, including missense mutations (T263M, T376M, R383H, A606T, R763H, M829R, R834Q, R937P, and X1021R), a deletion mutant (del(K935-S940)ins(I)), and a frameshift mutation (S966fs). According to the Na(+)/K(+)-ATPase crystal structure, a subset of the mutated residues (Ala(606), Arg(763), Met(829), and Arg(834)) is involved in important interdomain H-bond networks, and the C terminus of the enzyme, which is elongated by the X1021R mutation, has been implicated in voltage dependence and formation of a third Na(+)-binding site. Upon heterologous expression in Xenopus oocytes, the analysis of electrogenic transport properties, Rb(+) uptake, and protein expression revealed pronounced and markedly diverse functional alterations in all ATP1A2 mutants. Abnormalities included a complete loss of function (T376M), impaired plasma membrane expression (del(K935-S940)ins(I) and S966fs), and altered apparent affinities for extracellular cations or reduced enzyme turnover (R383H, A606T, R763H, R834Q, and X1021R). In addition, changes in the voltage dependence of pump currents and the increased rate constants of the voltage jump-induced redistribution between E(1)P and E(2)P states were observed. Thus, mutations that disrupt distinct interdomain H-bond patterns can cause abnormal conformational flexibility and exert long range consequences on apparent cation affinities or voltage dependence. Of interest, the X1021R mutation severely impaired voltage dependence and kinetics of Na(+)-translocating partial reactions, corroborating the critical role of the C terminus of Na(+)/K(+)-ATPase in these processes.
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Affiliation(s)
- Neslihan N Tavraz
- Technical University of Berlin, Institute of Chemistry, D-10623 Berlin, Germany
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van der Velde AE, Vrins CLJ, van den Oever K, Seemann I, Oude Elferink RPJ, van Eck M, Kuipers F, Groen AK. Regulation of direct transintestinal cholesterol excretion in mice. Am J Physiol Gastrointest Liver Physiol 2008; 295:G203-G208. [PMID: 18511744 DOI: 10.1152/ajpgi.90231.2008] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Biliary secretion is generally considered to be an obligate step in the pathway of excess cholesterol excretion from the body. We have recently shown that an alternative route exists. Direct transintestinal cholesterol efflux (TICE) contributes significantly to cholesterol removal in mice. Our aim was to investigate whether the activity of this novel pathway can be influenced by dietary factors. In addition, we studied the role of cholesterol acceptors at the luminal side of the enterocyte. Mice were fed a Western-type diet (0.25% wt/wt cholesterol; 16% wt/wt fat), a high-fat diet (no cholesterol; 24% wt/wt fat), or high-cholesterol diet (2% wt/wt), and TICE was measured by isolated intestinal perfusion. Bile salt-phospholipid mixtures served as cholesterol acceptor. Western-type and high-fat diet increased TICE by 50 and 100%, respectively. In contrast, the high-cholesterol diet did not influence TICE. Intestinal scavenger receptor class B type 1 (Sr-B1) mRNA and protein levels correlated with the rate of TICE. Unexpectedly, although confirming a role for Sr-B1, TICE was significantly increased in Sr-B1-deficient mice. Apart from the long-term effect of diets on TICE, acute effects by luminal cholesterol acceptors were also investigated. The phospholipid content of perfusate was the most important regulator of TICE; bile salt concentration or hydrophobicity of bile salts had little effect. In conclusion, TICE can be manipulated by dietary intervention. Specific dietary modifications might provide means to stimulate TICE and, thereby, to enhance total cholesterol turnover.
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Dürr KL, Tavraz NN, Zimmermann D, Bamberg E, Friedrich T. Characterization of Na,K-ATPase and H,K-ATPase Enzymes with Glycosylation-Deficient β-Subunit Variants by Voltage-Clamp Fluorometry in Xenopus Oocytes. Biochemistry 2008; 47:4288-97. [DOI: 10.1021/bi800092k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katharina L. Dürr
- Max Volmer Laboratory for Biophysical Chemistry, Institute of Chemistry, Technical University of Berlin, Secr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt/Main, Germany, and Chemical and Pharmaceutical Sciences Department, Johann Wolfgang Goethe University Frankfurt, Max-von-Laue-Strasse 1, 7-9, D-60439 Frankfurt/Main, Germany
| | - Neslihan N. Tavraz
- Max Volmer Laboratory for Biophysical Chemistry, Institute of Chemistry, Technical University of Berlin, Secr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt/Main, Germany, and Chemical and Pharmaceutical Sciences Department, Johann Wolfgang Goethe University Frankfurt, Max-von-Laue-Strasse 1, 7-9, D-60439 Frankfurt/Main, Germany
| | - Dirk Zimmermann
- Max Volmer Laboratory for Biophysical Chemistry, Institute of Chemistry, Technical University of Berlin, Secr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt/Main, Germany, and Chemical and Pharmaceutical Sciences Department, Johann Wolfgang Goethe University Frankfurt, Max-von-Laue-Strasse 1, 7-9, D-60439 Frankfurt/Main, Germany
| | - Ernst Bamberg
- Max Volmer Laboratory for Biophysical Chemistry, Institute of Chemistry, Technical University of Berlin, Secr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt/Main, Germany, and Chemical and Pharmaceutical Sciences Department, Johann Wolfgang Goethe University Frankfurt, Max-von-Laue-Strasse 1, 7-9, D-60439 Frankfurt/Main, Germany
| | - Thomas Friedrich
- Max Volmer Laboratory for Biophysical Chemistry, Institute of Chemistry, Technical University of Berlin, Secr. PC 14, Strasse des 17. Juni 135, D-10623 Berlin, Germany, Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt/Main, Germany, and Chemical and Pharmaceutical Sciences Department, Johann Wolfgang Goethe University Frankfurt, Max-von-Laue-Strasse 1, 7-9, D-60439 Frankfurt/Main, Germany
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Impaired routing of wild type FXYD2 after oligomerisation with FXYD2-G41R might explain the dominant nature of renal hypomagnesemia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:398-404. [DOI: 10.1016/j.bbamem.2007.10.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 10/09/2007] [Accepted: 10/10/2007] [Indexed: 11/21/2022]
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40
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Paulusma CC, Folmer DE, Ho-Mok KS, de Waart DR, Hilarius PM, Verhoeven AJ, Oude Elferink RPJ. ATP8B1 requires an accessory protein for endoplasmic reticulum exit and plasma membrane lipid flippase activity. Hepatology 2008; 47:268-78. [PMID: 17948906 DOI: 10.1002/hep.21950] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
UNLABELLED Mutations in ATP8B1 cause progressive familial intrahepatic cholestasis type 1 and benign recurrent intrahepatic cholestasis type 1. Previously, we have shown in mice that Atp8b1 deficiency leads to enhanced biliary excretion of phosphatidylserine, and we hypothesized that ATP8B1 is a flippase for phosphatidylserine. However, direct evidence for this function is still lacking. In Saccharomyces cerevisiae, members of the Cdc50p/Lem3p family are essential for proper function of the ATP8B1 homologs. We have studied the role of two human members of this family, CDC50A and CDC50B, in the routing and activity of ATP8B1. When only ATP8B1 was expressed in Chinese hamster ovary cells, the protein localized to the endoplasmic reticulum. Coexpression with CDC50 proteins resulted in relocalization of ATP8B1 from the endoplasmic reticulum to the plasma membrane. Only when ATP8B1 was coexpressed with CDC50 proteins was a 250%-500% increase in the translocation of fluorescently labeled phosphatidylserine observed. Importantly, natural phosphatidylserine exposure in the outer leaflet of the plasma membrane was reduced by 17%-25% in cells coexpressing ATP8B1 and CDC50 proteins in comparison with cells expressing ATP8B1 alone. The coexpression of ATP8B1 and CDC50A in WIF-B9 cells resulted in colocalization of both proteins in the canalicular membrane. CONCLUSION Our data indicate that CDC50 proteins are pivotal factors in the trafficking of ATP8B1 to the plasma membrane and thus may be essential determinants of ATP8B1-related disease. In the plasma membrane, ATP8B1 functions as a flippase for phosphatidylserine. Finally, CDC50A may be the potential beta-subunit or chaperone for ATP8B1 in hepatocytes.
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Affiliation(s)
- Coen C Paulusma
- AMC Liver Center, Academic Medical Center, Amsterdam, The Netherlands.
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Huls M, Kramers C, Levtchenko EN, Wilmer MJG, Dijkman HBPM, Kluijtmans LAJ, van der Hoorn JWA, Russel FGM, Masereeuw R. P-glycoprotein-deficient mice have proximal tubule dysfunction but are protected against ischemic renal injury. Kidney Int 2007; 72:1233-41. [PMID: 17851469 DOI: 10.1038/sj.ki.5002522] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The multidrug resistance gene 1 product, P-glycoprotein (P-gp), is expressed in several excretory organs, including the apical membrane of proximal tubules. After inducing acute renal failure, P-gp expression is upregulated and this might be a protective function by pumping out toxicants and harmful products of oxidative stress. We characterized renal function of P-gp knockout mice and studied its consequences in renal ischemic damage. Compared with wild-type mice, knockout mice have a lower glomerular filtration rate and renal plasma flow. An augmented urinary excretion of sodium, numerous amino acids, calcium, glucose, and low molecular weight proteins was observed along with an increased diuresis. A higher lithium plasma clearance in the knockout mice suggested proximal tubular dysfunction. Electron microscopy showed mitochondrial abnormalities in proximal tubular cells that could account for decreased adenosine triphosphate levels in the cortex. After inducing ischemia, wild-type mice showed a decrease in creatinine clearance and severe proximal tubular necrosis. In contrast, knockout mice had no signs of tubular damage. Our data indicate that P-gp knockout mice have impaired renal function but are protected against ischemic renal injury.
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Affiliation(s)
- M Huls
- Department of Pharmacology and Toxicology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Groen A, Kunne C, Paulusma CC, Kramer W, Agellon LB, Bull LN, Oude Elferink RPJ. Intestinal bile salt absorption in Atp8b1 deficient mice. J Hepatol 2007; 47:114-22. [PMID: 17448567 DOI: 10.1016/j.jhep.2007.02.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Revised: 02/04/2007] [Accepted: 02/12/2007] [Indexed: 12/04/2022]
Abstract
BACKGROUND/AIMS Mutations in the ATP8B1 gene can cause Progressive Familial Intrahepatic Cholestasis type 1. We have previously reported that Atp8b1(G308V/G308V) mice, a model for PFIC1, have slightly, but significantly, higher baseline serum bile salt (BS) concentrations compared to wt mice. Upon BS feeding, serum BS concentrations strongly increased in Atp8b1-deficient mice. Despite these findings, we observed only mildly impaired canalicular BS transport. In the present report we tested the hypothesis that Atp8b1(G308V/G308V) mice hyperabsorb BS in the intestine during BS feeding. METHODS Intestinal BS absorption was measured in intestinal perfusion and in intestinal explants. In addition, we measured BS concentrations in portal blood. Ileal expression of the Fxr-targets Asbt, Ilbp and Shp was assessed. RESULTS In wt and Atp8b1(G308V/G308V) mice, intestinal taurocholate absorption is primarily mediated by the ileal bile salt transporter Asbt. Neither of the experimental systems revealed enhanced absorption of BS in Atp8b1(G308V/G308V) mice compared to wt mice. In line with these observations, we found no difference in the ileal protein expression of Asbt. Induction of Shp expression during BS feeding also demonstrated that Fxr signalling is intact in Atp8b1(G308V/G308V) mice. CONCLUSIONS The accumulation of BS in plasma of Atp8b1(G308V/G308V) mice during BS feeding is not caused by increased intestinal BS absorption.
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Affiliation(s)
- Annemiek Groen
- AMC Liver Center, Academic Medical Center, Room S1-166, Meibergdreef 69-71, 1105 BK Amsterdam, The Netherlands
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Paulusma CC, Groen A, Kunne C, Ho-Mok KS, Spijkerboer AL, Rudi de Waart D, Hoek FJ, Vreeling H, Hoeben KA, van Marle J, Pawlikowska L, Bull LN, Hofmann AF, Knisely AS, Oude Elferink RPJ. Atp8b1 deficiency in mice reduces resistance of the canalicular membrane to hydrophobic bile salts and impairs bile salt transport. Hepatology 2006; 44:195-204. [PMID: 16799980 DOI: 10.1002/hep.21212] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Progressive familial intrahepatic cholestasis type 1 (PFIC1, Byler disease, OMIM 211600) is a severe inherited liver disease caused by mutations in ATP8B1. ATP8B1 is a member of the type 4 subfamily of P-type ATPases, which are phospholipid flippases. PFIC1 patients generally develop end-stage liver disease before the second decade of life. The disease is characterized by impaired biliary bile salt excretion, but the mechanism whereby impaired ATP8B1 function results in cholestasis is unclear. In a mouse model for PFIC1, we observed decreased resistance of the hepatocanalicular membrane to hydrophobic bile salts as evidenced by enhanced biliary recovery of phosphatidylserine, cholesterol, and ectoenzymes. In liver specimens from PFIC1 patients, but not in those from control subjects, ectoenzyme expression at the canalicular membrane was markedly deficient. In isolated mouse livers Atp8b1 deficiency impaired the transport of hydrophobic bile salts into bile. In conclusion, our study shows that Atp8b1 deficiency causes loss of canalicular phospholipid membrane asymmetry that in turn renders the canalicular membrane less resistant toward hydrophobic bile salts. The loss of phospholipid asymmetry may subsequently impair bile salt transport and cause cholestasis.
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Affiliation(s)
- Coen C Paulusma
- Amsterdam Liver Center, Department of Experimental Hepatology, Academic Medical Center, Amsterdam, the Netherlands.
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Todt U, Dichgans M, Jurkat-Rott K, Heinze A, Zifarelli G, Koenderink JB, Goebel I, Zumbroich V, Stiller A, Ramirez A, Friedrich T, Göbel H, Kubisch C. Rare missense variants in ATP1A2 in families with clustering of common forms of migraine. Hum Mutat 2006; 26:315-21. [PMID: 16110494 DOI: 10.1002/humu.20229] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Migraine is a recurrent neurovascular disease. Its two most common forms-migraine without aura (MO) and migraine with aura (MA)-both show familial clustering and a complex pattern of inheritance. Familial hemiplegic migraine (FHM) is a rare monogenic subform caused by mutations in the calcium channel gene CACNA1A or the Na(+)/K(+)-ATPase gene ATP1A2. An involvement of FHM genes in the pathogenesis of common forms of migraine is not proven. We therefore systematically screened ATP1A2 in families with several members affected by MA and/or MO. We identified two novel missense alterations [c.520G>A (p.E174 K) and c.1544G>A (p.C515Y)] in two out of 45 families, which were not found in 520 control chromosomes. Functional studies of these variants in Xenopus oocytes by two-electrode voltage clamp measurements and radiochemical determination of ATPase activity showed that C515Y leads to a complete loss of function comparable with the effect of FHM-mutations whereas for E174 K no functional alteration could be found in the in vitro assays. In conclusion we propose that rare variants in ATP1A2 are involved in the susceptibility to common forms of migraine, because of 1) the absence of alterations in controls, 2) the particular pattern of segregation in both families, 3) the high conservation of mutated residues in Na(+)/K(+)-ATPases, 4) the functional effect of C515Y, and 5) the involvement of ATP1A2 in a monogenic form of migraine.
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Affiliation(s)
- Unda Todt
- Institut für Humangenetik, Universitätsklinikum Bonn, Bonn, Germany
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45
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Huls M, van den Heuvel JJMW, Dijkman HBPM, Russel FGM, Masereeuw R. ABC transporter expression profiling after ischemic reperfusion injury in mouse kidney. Kidney Int 2006; 69:2186-93. [PMID: 16612327 DOI: 10.1038/sj.ki.5000407] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Renal ATP binding cassette (ABC) transporters have an important role in the elimination of metabolic waste products and compounds foreign to the body. The kidney has the ability to tightly control the expression of these efflux transporters to maintain homeostasis, and as a major mechanism of adaptation to environmental stress. In the present study, we investigated the expression of 45 ABC transporter genes in the mouse kidney under basal conditions, after induction of ischemia and after regeneration. Two days after clamping, mice showed a 76% decrease in renal creatinine clearance, which improved clearly within 7 days. This was confirmed by histological examinations. Seven days after ischemia, real-time quantitative Polymerase chain reaction data showed that transcript abundance of abcb1, abcb11, and abcc4 was increased, and that of abca3, abcc2, and abcg2 decreased. Expression of all transporters returned to baseline after 14 days, except for abcb11, which was reduced. Abcb11 is the major liver canalicular bile salt export pump. Here we show for the first time expression in the kidney and localization of the transporter to the apical membrane of proximal tubules. The presence of another novel renal transporter, abca3, was confirmed by Western blotting. Immunohistochemistry showed that abca3 is localized to the peritubular capillaries and apical membrane of proximal tubules. In conclusion, after inducing ischemic reperfusion injury in the kidney, ABC transporters appear to be differentially regulated, which might be associated with the renal regeneration process. Furthermore, we showed for the first time expression and subcellular localization of abcb11 and abca3 in mouse kidney.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B
- ATP Binding Cassette Transporter, Subfamily B, Member 1
- ATP Binding Cassette Transporter, Subfamily B, Member 11
- ATP Binding Cassette Transporter, Subfamily G, Member 2
- ATP-Binding Cassette Transporters/analysis
- ATP-Binding Cassette Transporters/biosynthesis
- ATP-Binding Cassette Transporters/genetics
- Animals
- Blotting, Western
- Gene Expression Profiling
- Gene Expression Regulation
- Immunohistochemistry
- Kidney/chemistry
- Kidney/pathology
- Kidney Tubules, Proximal/chemistry
- Kidney Tubules, Proximal/pathology
- Male
- Membrane Transport Proteins/analysis
- Membrane Transport Proteins/genetics
- Mice
- Mice, Inbred Strains
- Multidrug Resistance-Associated Protein 2
- Multidrug Resistance-Associated Proteins/analysis
- Multidrug Resistance-Associated Proteins/genetics
- Reperfusion Injury/genetics
- Reperfusion Injury/pathology
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- M Huls
- Department of Pharmacology and Toxicology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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van Ham M, Kemperman L, Wijers M, Fransen J, Hendriks W. Subcellular localization and differentiation-induced redistribution of the protein tyrosine phosphatase PTP-BL in Neuroblastoma cells. Cell Mol Neurobiol 2006; 25:1225-44. [PMID: 16388334 DOI: 10.1007/s10571-005-8500-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2004] [Indexed: 11/28/2022]
Abstract
1. In cells of epithelial origin the protein tyrosine phosphatase PTP-BL is predominantly localized at the apical membrane of polarized cells. This large submembranous multidomain PTP is also expressed in cells of neuronal origin. We studied the localization of PTP-BL in mouse neuroblastoma cells utilizing EGFP-tagged versions of the protein. 2. In proliferating Neuro-2a cells, immunofluorescence and immuno-electron microscopy revealed a submembranous FERM domain-dependent localization at cell-cell boundaries for EGFP-PTP-BL. Additionally, significant amounts of EGFP-PTP-BL are located in the cytoplasm as well as in nuclei. Upon serum depletion-induced differentiation of Neuro-2a cells, a partial shift of EGFP-PTP-BL from a cortical localization to cytoskeleton-like F-actin-positive structures is observed. Parallel biochemical studies corroborate this finding and reveal a serum depletion-induced shift of EFGP-PTP-BL from a membrane(-associated) fraction to an NP40-soluble cytoskeletal fraction. 3. Different pools of PTP-BL-containing protein complexes can be discerned in neuronal cells, reflecting distinct molecular microenvironments in which PTP-BL may exert its function.
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Affiliation(s)
- Marco van Ham
- Department of Cell Biology, Institute of Cellular Signalling, Nijmegen Centre for Molecular Life Sciences, Radbound University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Qiu LY, Swarts HGP, Tonk ECM, Willems PHGM, Koenderink JB, De Pont JJHHM. Conversion of the Low Affinity Ouabain-binding Site of Non-gastric H,K-ATPase into a High Affinity Binding Site by Substitution of Only Five Amino Acids. J Biol Chem 2006; 281:13533-13539. [PMID: 16531406 DOI: 10.1074/jbc.m600551200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P-type ATPases of the IIC subfamily exhibit large differences in sensitivity toward ouabain. This allows a strategy in which ouabain-insensitive members of this subfamily are used as template for mutational elucidation of the ouabain-binding site. With this strategy, we recently identified seven amino acids in Na,K-ATPase that conferred high affinity ouabain binding to gastric H,K-ATPase (Qiu, L. Y., Krieger, E., Schaftenaar, G., Swarts, H. G. P., Willems, P. H. G. M., De Pont, J. J. H. H. M., and Koenderink, J. B. (2005) J. Biol. Chem. 280, 32349-32355). Because important, but identical, amino acids were not recognized in that study, here we used the non-gastric H,K-ATPase, which is rather ouabain-insensitive, as template. The catalytic subunit of this enzyme, in which several amino acids from Na,K-ATPase were incorporated, was expressed with the Na,K-ATPase beta1 subunit in Xenopus laevis oocytes. A chimera containing 14 amino acids, located in M4, M5, and M6, which are unique to Na,K-ATPase, displayed high affinity ouabain binding. Four of these residues, all located in M5, appeared dispensable for high affinity binding. Individual mutation of the remaining 10 residues to their non-gastric H,K-ATPase counterparts yielded five amino acids (Glu312,Gly319, Pro778, Leu795, and Cys802) whose mutation resulted in a loss of ouabain binding. In a final gain-of-function experiment, we introduced these five amino acids in different combinations in non-gastric H,K-ATPase and demonstrated that all five were essential for high affinity ouabain binding. The non-gastric H,K-ATPase with these five mutations had a similar apparent affinity for ouabain as the wild type Na,K-ATPase and showed a 2000 times increased affinity for ouabain in the NH4+-stimulated ATPase activity in membranes of transfected Sf9 cells.
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Affiliation(s)
- Li Yan Qiu
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Herman G P Swarts
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Elisa C M Tonk
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Peter H G M Willems
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Jan B Koenderink
- Department of Pharmacology/Toxicology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands
| | - Jan Joep H H M De Pont
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen 6500 HB, The Netherlands.
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van Abel M, Hoenderop JGJ, van der Kemp AWCM, Friedlaender MM, van Leeuwen JPTM, Bindels RJM. Coordinated control of renal Ca2+ transport proteins by parathyroid hormone. Kidney Int 2005; 68:1708-21. [PMID: 16164647 DOI: 10.1111/j.1523-1755.2005.00587.x] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The kidney is one of the affected organs involved in the clinical symptoms of parathyroid hormone (PTH)-related disorders, like primary hyperparathyroidism and familial hypocalciuric hypercalcemia. The molecular mechanism(s) underlying alterations in renal Ca(2+) handling in these disorders is poorly understood. METHODS Parathyroidectomized and PTH-supplemented rats and mice infused with the calcimimetic compound NPS R-467 were used to study the in vivo effect of PTH on the expression of renal transcellular Ca(2+) transport proteins, including the epithelial Ca(2+) channel transient receptor potential, vanilloid, member 5 (TRPV5), calbindins, and the Na(+)/Ca(2+)-exchanger (NCX1). In addition, the effect of PTH on transepithelial Ca(2+) transport in rabbit connecting tubule/cortical collecting duct (CNT/CCD) primary cultures was determined. RESULTS Decreased PTH levels in parathyroidectomized rats or NPS R-467-infused mice, resulted in reduced expression of these proteins, which is consistent with diminished Ca(2+) reabsorption, causing the development of the observed hypocalcemia. PTH supplementation of parathyroidectomized rats restored the expression of the renal Ca(2+) transport machinery and serum Ca(2+) levels, independent of serum 1,25-dihydroxyvitamin D(3) levels and renal vitamin D or Ca(2+)-sensing receptor mRNA abundance. Inhibition of the PTH-stimulated transepithelial Ca(2+) transport by the TRPV5-specific inhibitor ruthenium red reduced the PTH-stimulated expression of calbindin-D(28K) and NCX1 in rabbit CNT/CCD primary cultures. CONCLUSION PTH stimulates renal Ca(2+) reabsorption through the coordinated expression of renal transcellular Ca(2+) transport proteins. Moreover, the PTH-induced stimulation is enhanced by the magnitude of the Ca(2+) influx through the gatekeeper TRPV5, which in turn facilitates the expression of the downstream Ca(2+) transport proteins. Therefore, the renal transcellular Ca(2+) transport proteins, including TRPV5, could contribute to the pathogenesis of PTH-related disorders.
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Affiliation(s)
- Monique van Abel
- Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Grewer C, Rauen T. Electrogenic glutamate transporters in the CNS: molecular mechanism, pre-steady-state kinetics, and their impact on synaptic signaling. J Membr Biol 2005; 203:1-20. [PMID: 15834685 PMCID: PMC2389879 DOI: 10.1007/s00232-004-0731-6] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2004] [Accepted: 12/06/2004] [Indexed: 12/12/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian CNS. The spatiotemporal profile of the glutamate concentration in the synapse is critical for excitatory synaptic signalling. The control of this spatiotemporal concentration profile requires the presence of large numbers of synaptically localized glutamate transporters that remove pre-synaptically released glutamate by uptake into neurons and adjacent glia cells. These glutamate transporters are electrogenic and utilize energy stored in the transmembrane potential and the Na+/K+-ion concentration gradients to accumulate glutamate in the cell. This review focuses on the kinetic and electrogenic properties of glutamate transporters, as well as on the molecular mechanism of transport. Recent results are discussed that demonstrate the multistep nature of the transporter reaction cycle. Results from pre-steady-state kinetic experiments suggest that at least four of the individual transporter reaction steps are electrogenic, including reactions associated with the glutamate-dependent transporter halfcycle. Furthermore, the kinetic similarities and differences between some of the glutamate transporter subtypes and splice variants are discussed. A molecular mechanism of glutamate transport is presented that accounts for most of the available kinetic data. Finally, we discuss how synaptic glutamate transporters impact on glutamate receptor activity and how transporters may shape excitatory synaptic transmission.
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Affiliation(s)
- C Grewer
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA.
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Koenderink JB, Zifarelli G, Qiu LY, Schwarz W, De Pont JJHHM, Bamberg E, Friedrich T. Na,K-ATPase mutations in familial hemiplegic migraine lead to functional inactivation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1669:61-8. [PMID: 15843000 DOI: 10.1016/j.bbamem.2005.01.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 01/10/2005] [Accepted: 01/10/2005] [Indexed: 12/14/2022]
Abstract
The Na,K-ATPase is an ion-translocating transmembrane protein that actively maintains the electrochemical gradients for Na+ and K+ across the plasma membrane. The functional protein is a heterodimer comprising a catalytic alpha-subunit (four isoforms) and an ancillary beta-subunit (three isoforms). Mutations in the alpha2-subunit have recently been implicated in familial hemiplegic migraine type 2, but almost no thorough studies of the functional consequences of these mutations have been provided. We investigated the functional properties of the mutations L764P and W887R in the human Na,K-ATPase alpha2-subunit upon heterologous expression in Xenopus oocytes. No Na,K-ATPase-specific pump currents could be detected in cells expressing these mutants. The binding of radiolabelled [3H]ouabain to intact cells suggested that this could be due to a lack of plasma membrane expression. However, plasma membrane isolation showed that the mutated pumps are well expressed at the plasma membrane. 86Rb+-flux and ATPase activity measurements demonstrated that the mutants are inactive. Therefore, the primary disease-causing mechanism is loss-of-function of the Na,K-ATPase alpha2-isoform.
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Affiliation(s)
- Jan B Koenderink
- Department of Biochemistry, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500HB Nijmegen, The Netherlands
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