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Maji S, Pirozzi M, Ruturaj, Pandey R, Ghosh T, Das S, Gupta A. Copper-independent lysosomal localisation of the Wilson disease protein ATP7B. Traffic 2023; 24:587-609. [PMID: 37846526 DOI: 10.1111/tra.12919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 09/10/2023] [Accepted: 09/23/2023] [Indexed: 10/18/2023]
Abstract
In hepatocytes, the Wilson disease protein ATP7B resides on the trans-Golgi network (TGN) and traffics to peripheral lysosomes to export excess intracellular copper through lysosomal exocytosis. We found that in basal copper or even upon copper chelation, a significant amount of ATP7B persists in the endolysosomal compartment of hepatocytes but not in non-hepatic cells. These ATP7B-harbouring lysosomes lie in close proximity of ~10 nm to the TGN. ATP7B constitutively distributes itself between the sub-domain of the TGN with a lower pH and the TGN-proximal lysosomal compartments. The presence of ATP7B on TGN-lysosome colocalising sites upon Golgi disruption suggested a possible exchange of ATP7B directly between the TGN and its proximal lysosomes. Manipulating lysosomal positioning significantly alters the localisation of ATP7B in the cell. Contrary to previous understanding, we found that upon copper chelation in a copper-replete hepatocyte, ATP7B is not retrieved back to TGN from peripheral lysosomes; rather, ATP7B recycles to these TGN-proximal lysosomes to initiate the next cycle of copper transport. We report a hitherto unknown copper-independent lysosomal localisation of ATP7B and the importance of TGN-proximal lysosomes but not TGN as the terminal acceptor organelle of ATP7B in its retrograde pathway.
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Affiliation(s)
- Saptarshi Maji
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | | | - Ruturaj
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Raviranjan Pandey
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Tamal Ghosh
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Santanu Das
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Arnab Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
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2
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Das S, Mohammed A, Mandal T, Maji S, Verma J, Ruturaj, Gupta A. Polarized trafficking and copper transport activity of ATP7B: a mutational approach to establish genotype-phenotype correlation in Wilson disease. Hum Mutat 2022; 43:1408-1429. [PMID: 35762218 DOI: 10.1002/humu.24428] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Revised: 06/22/2022] [Accepted: 06/24/2022] [Indexed: 11/07/2022]
Abstract
Mutation in ATP7B gene causes Wilson disease (WD) that is characterized by severe hepatic and neurological symptoms. ATP7B localizes at the trans-Golgi Network (TGN) transporting copper to copper-dependent enzymes and traffics in apically targeted vesicles upon intracellular copper elevation. To decode the cellular underpinnings of WD manifestation we investigated copper-responsive polarized trafficking and copper transport activity of fifteen WD causing point mutations in ATP7B. Amino-terminal mutations Gly85Val, Leu168Pro and Gly591Asp displayed TGN and sub-apical localization whereas, Leu492Ser mislocalized at the basolateral region. The actuator domain mutation Gly875Arg shows retention in the endoplasmic reticulum (ER), Ala874Val and Leu795Phe show partial targeting to TGN and post-Golgi vesicles. The Nucleotide-Binding Domain mutations His1069Gln and Leu1083Phe also display impaired targeting. The C-terminal mutations Leu1373Pro/Arg is arrested at ER but Ser1423Asn shows TGN localization. Transmembrane mutant Arg778Leu resides in ER and TGN while Arg969Gln is exclusively ER localized. Cellular Cu level does not alter the targeting of any of the studied mutations. Mutants that traffic to TGN exhibits biosynthetic function. Finally, we correlated cellular phenotypes with the clinical manifestation of the two most prevalent mutations; the early onset and more aggressive WD caused by Arg778Leu and the milder form of WD caused by mutation His1069Gln. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Santanu Das
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Ameena Mohammed
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Taniya Mandal
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Saptarshi Maji
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Jay Verma
- Maulana Azad Medical College, 2 Bahadur Shah Zafar Marg, New Delhi, Delhi, 110002, India
| | - Ruturaj
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
| | - Arnab Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
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3
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Wen MH, Xie X, Huang PS, Yang K, Chen TY. Crossroads between membrane trafficking machinery and copper homeostasis in the nerve system. Open Biol 2021; 11:210128. [PMID: 34847776 PMCID: PMC8633785 DOI: 10.1098/rsob.210128] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Imbalanced copper homeostasis and perturbation of membrane trafficking are two common symptoms that have been associated with the pathogenesis of neurodegenerative and neurodevelopmental diseases. Accumulating evidence from biophysical, cellular and in vivo studies suggest that membrane trafficking orchestrates both copper homeostasis and neural functions-however, a systematic review of how copper homeostasis and membrane trafficking interplays in neurons remains lacking. Here, we summarize current knowledge of the general trafficking itineraries for copper transporters and highlight several critical membrane trafficking regulators in maintaining copper homeostasis. We discuss how membrane trafficking regulators may alter copper transporter distribution in different membrane compartments to regulate intracellular copper homeostasis. Using Parkinson's disease and MEDNIK as examples, we further elaborate how misregulated trafficking regulators may interplay parallelly or synergistically with copper dyshomeostasis in devastating pathogenesis in neurodegenerative diseases. Finally, we explore multiple unsolved questions and highlight the existing challenges to understand how copper homeostasis is modulated through membrane trafficking.
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Affiliation(s)
- Meng-Hsuan Wen
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Xihong Xie
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Pei-San Huang
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Karen Yang
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Tai-Yen Chen
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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4
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Lutsenko S. Dynamic and cell-specific transport networks for intracellular copper ions. J Cell Sci 2021; 134:272704. [PMID: 34734631 DOI: 10.1242/jcs.240523] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Copper (Cu) homeostasis is essential for the development and function of many organisms. In humans, Cu misbalance causes serious pathologies and has been observed in a growing number of diseases. This Review focuses on mammalian Cu(I) transporters and highlights recent studies on regulation of intracellular Cu fluxes. Cu is used by essential metabolic enzymes for their activity. These enzymes are located in various intracellular compartments and outside cells. When cells differentiate, or their metabolic state is otherwise altered, the need for Cu in different cell compartments change, and Cu has to be redistributed to accommodate these changes. The Cu transporters SLC31A1 (CTR1), SLC31A2 (CTR2), ATP7A and ATP7B regulate Cu content in cellular compartments and maintain Cu homeostasis. Increasing numbers of regulatory proteins have been shown to contribute to multifaceted regulation of these Cu transporters. It is becoming abundantly clear that the Cu transport networks are dynamic and cell specific. The comparison of the Cu transport machinery in the liver and intestine illustrates the distinct composition and dissimilar regulatory response of their Cu transporters to changing Cu levels.
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Affiliation(s)
- Svetlana Lutsenko
- Johns Hopkins Medical Institutes, Department of Physiology, Baltimore, MD 21205, USA
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5
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McCann CJ, Jayakanthan S, Siotto M, Yang N, Osipova M, Squitti R, Lutsenko S. Single nucleotide polymorphisms in the human ATP7B gene modify the properties of the ATP7B protein. Metallomics 2020; 11:1128-1139. [PMID: 31070637 DOI: 10.1039/c9mt00057g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Single nucleotide polymorphisms (SNPs) are the largest source of sequence variation in the human genome. However, their functional significance is not well understood. We show that SNPs in the Wilson disease gene, ATP7B, that produce amino-acid substitutions K832R and R952K, modulate ATP7B properties in vitro and influence serum copper (Cu) status in vivo. The presence of R832 is associated with a lower ATP7B abundance and a diminished trafficking in response to elevated Cu. The K832R substitution alters surface exposure of amino acid residues in the actuator domain and increases its conformational flexibility. All SNP-related ATP7B variants (R832/R952, R832/K952, K832/K952, and K832/R952) have Cu-transport activity. However, the activity of ATP7B-K832/K952 is lower compared to other variants. In humans, the presence of K952 is associated with a higher fraction of exchangeable Cu in serum. Thus, SNPs may modulate the properties of ATP7B and the organism Cu status.
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Affiliation(s)
- Courtney J McCann
- Department of Physiology, Johns Hopkins University, Baltimore, MD, USA.
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Monestier M, Pujol AM, Lamboux A, Cuillel M, Pignot-Paintrand I, Cassio D, Charbonnier P, Um K, Harel A, Bohic S, Gateau C, Balter V, Brun V, Delangle P, Mintz E. A liver-targeting Cu(i) chelator relocates Cu in hepatocytes and promotes Cu excretion in a murine model of Wilson's disease. Metallomics 2020; 12:1000-1008. [DOI: 10.1039/d0mt00069h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A hepatocyte-targeting chelator promotes Cu biliary excretion, hence restoring the physiological Cu detoxification pathway in a murine Wilson's disease model.
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Affiliation(s)
| | | | | | | | | | - Doris Cassio
- INSERM
- Univ. Paris Sud
- UMR U 1174
- F-91405 Orsay
- France
| | | | | | | | - Sylvain Bohic
- Inserm
- UA7
- Synchrotron Radiation for Biomedicine (STROBE)
- Grenoble
- France
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7
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Polishchuk RS, Polishchuk EV. From and to the Golgi - defining the Wilson disease protein road map. FEBS Lett 2019; 593:2341-2350. [PMID: 31408533 DOI: 10.1002/1873-3468.13575] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/01/2019] [Accepted: 08/08/2019] [Indexed: 11/05/2022]
Abstract
Recent studies highlight the continued growth in the identification of a variety of cellular functions that involve the Golgi apparatus. Apart from well-known membrane sorting/trafficking and glycosylation machineries, the Golgi harbors molecular platforms operating in intracellular signaling, cytoskeleton organization, and protein quality control mechanisms. One of new emerging Golgi functions consists in the regulation of copper homeostasis by coordinating the relocation and activity of copper transporters. Of these, the Cu-transporting ATPase ATP7B (known as Wilson disease protein) plays a key role in the maintenance of the Cu balance in the body via the supply of essential Cu to the systemic circulation and via elimination of excess Cu into the bile. These activities require tightly regulated shuttling of ATP7B between the Golgi and different post-Golgi compartments. Despite significant progress over recent years, a number of issues regarding ATP7B trafficking remain to be clarified. This review summarizes current views on ATP7B trafficking pathways from and to the Golgi and underscores the challenges that should be addressed to define the ATP7B trafficking routes and mechanisms in health and disease.
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Affiliation(s)
- Roman S Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Naples, Italy
| | - Elena V Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Naples, Italy.,ITMO University, St. Petersburg, Russia
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Overeem AW, Klappe K, Parisi S, Klöters-Planchy P, Mataković L, du Teil Espina M, Drouin CA, Weiss KH, van IJzendoorn SCD. Pluripotent stem cell-derived bile canaliculi-forming hepatocytes to study genetic liver diseases involving hepatocyte polarity. J Hepatol 2019; 71:344-356. [PMID: 30965071 DOI: 10.1016/j.jhep.2019.03.031] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 03/15/2019] [Accepted: 03/31/2019] [Indexed: 01/07/2023]
Abstract
BACKGROUND & AIMS Hepatocyte polarity is essential for the development of bile canaliculi and for safely transporting bile and waste products from the liver. Functional studies of autologous mutated proteins in the context of the polarized hepatocyte have been challenging because of the lack of appropriate cell models. The aims of this study were to obtain a patient-specific hepatocyte model that recapitulated hepatocyte polarity and to employ this model to study endogenous mutant proteins in liver diseases that involve hepatocyte polarity. METHODS Urine cell-derived pluripotent stem cells, taken from a patient with a homozygous mutation in ATP7B and a patient with a heterozygous mutation, were differentiated towards hepatocyte-like cells (hiHeps). HiHeps were also derived from a patient with MEDNIK syndrome. RESULTS Polarized hiHeps that formed in vivo-like bile canaliculi could be generated from embryonic and patient urine cell-derived pluripotent stem cells. HiHeps recapitulated polarized protein trafficking processes, exemplified by the Cu2+-induced redistribution of the copper transporter protein ATP7B to the bile canalicular domain. We demonstrated that, in contrast to the current dogma, the most frequent yet enigmatic Wilson disease-causing ATP7B-H1069Q mutation per se did not preclude trafficking of ATP7B to the trans-Golgi Network. Instead, it prevented its Cu2+-induced polarized redistribution to the bile canalicular domain, which could not be reversed by pharmacological folding chaperones. Finally, we demonstrate that hiHeps from a patient with MEDNIK syndrome, suffering from liver copper overload of unclear etiology, showed no defect in the Cu2+-induced redistribution of ATP7B to the bile canaliculi. CONCLUSIONS Functional cell polarity can be achieved in patient pluripotent stem cell-derived hiHeps, enabling, for the first time, the study of the endogenous mutant proteins, patient-specific pathogenesis and drug responses for diseases where hepatocyte polarity is a key factor. LAY SUMMARY This study demonstrates that cells that are isolated from urine can be reprogrammed in a dish towards hepatocytes that display architectural characteristics similar to those seen in the intact liver. The application of this methodology to cells from patients diagnosed with inherited copper metabolism-related liver diseases (that is, Wilson disease and MEDNIK syndrome) revealed unexpected and novel insights into patient mutation-specific disease mechanisms and drug responses.
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Affiliation(s)
- Arend W Overeem
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Karin Klappe
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Silvia Parisi
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | | | - Lavinija Mataković
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Marines du Teil Espina
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Christian A Drouin
- Service de Dermatologie, Centre Hospitalier du Grand Portage, Rivière du Loup, Québec, Canada
| | - Karl Heinz Weiss
- University Hospital Heidelberg, Internal Medicine IV, Heidelberg, Germany
| | - Sven C D van IJzendoorn
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
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9
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Bidaud-Meynard A, Bossard F, Schnúr A, Fukuda R, Veit G, Xu H, Lukacs GL. Transcytosis maintains CFTR apical polarity in the face of constitutive and mutation-induced basolateral missorting. J Cell Sci 2019; 132:jcs.226886. [PMID: 30975917 DOI: 10.1242/jcs.226886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 04/02/2019] [Indexed: 12/22/2022] Open
Abstract
Apical polarity of cystic fibrosis transmembrane conductance regulator (CFTR) is essential for solute and water transport in secretory epithelia and can be impaired in human diseases. Maintenance of apical polarity in the face of CFTR non-polarized delivery and inefficient apical retention of mutant CFTRs lacking PDZ-domain protein (NHERF1, also known as SLC9A3R1) interaction, remains enigmatic. Here, we show that basolateral CFTR delivery originates from biosynthetic (∼35%) and endocytic (∼65%) recycling missorting. Basolateral channels are retrieved via basolateral-to-apical transcytosis (hereafter denoted apical transcytosis), enhancing CFTR apical expression by two-fold and suppressing its degradation. In airway epithelia, CFTR transcytosis is microtubule-dependent but independent of Myo5B, Rab11 proteins and NHERF1 binding to its C-terminal DTRL motif. Increased basolateral delivery due to compromised apical recycling and accelerated internalization upon impaired NHERF1-CFTR association is largely counterbalanced by efficient CFTR basolateral internalization and apical transcytosis. Thus, transcytosis represents a previously unrecognized, but indispensable, mechanism for maintaining CFTR apical polarity that acts by attenuating its constitutive and mutation-induced basolateral missorting.
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Affiliation(s)
| | - Florian Bossard
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - Andrea Schnúr
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - Ryosuke Fukuda
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - Guido Veit
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - Haijin Xu
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Montréal, QC, H3G 1Y6, Canada .,Department of Biochemistry, McGill University, Montréal, QC, H3G 1Y6, Canada
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10
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Trafficking mechanisms of P-type ATPase copper transporters. Curr Opin Cell Biol 2019; 59:24-33. [PMID: 30928671 DOI: 10.1016/j.ceb.2019.02.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 02/13/2019] [Accepted: 02/26/2019] [Indexed: 12/13/2022]
Abstract
Copper is an essential micronutrient required for oxygen-dependent enzymes, yet excess of the metal is a toxicant. The tug-of-war between these copper activities is balanced by chaperones and membrane transporters, which control copper distribution and availability. The P-type ATPase transporters, ATP7A and ATP7B, regulate cytoplasmic copper by pumping copper out of cells or into the endomembrane system. Mutations in ATP7A and ATP7B cause diseases that share neuropsychiatric phenotypes, which are similar to phenotypes observed in mutations affecting cytoplasmic trafficking complexes required for ATP7A/B dynamics. Here, we discuss evidence indicating that phenotypes associated to genetic defects in trafficking complexes, such as retromer and the adaptor complex AP-1, result in part from copper dyshomeostasis due to mislocalized ATP7A and ATP7B.
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11
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Reed E, Lutsenko S, Bandmann O. Animal models of Wilson disease. J Neurochem 2018; 146:356-373. [PMID: 29473169 PMCID: PMC6107386 DOI: 10.1111/jnc.14323] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Revised: 02/04/2018] [Accepted: 02/12/2018] [Indexed: 02/06/2023]
Abstract
Wilson disease (WD) is an autosomal recessive disorder of copper metabolism manifesting with hepatic, neurological and psychiatric symptoms. The limitations of the currently available therapy for WD (particularly in the management of neuropsychiatric disease), together with our limited understanding of key aspects of this illness (e.g. neurological vs. hepatic presentation) justify the ongoing need to study WD in suitable animal models. Four animal models of WD have been established: the Long-Evans Cinnamon rat, the toxic-milk mouse, the Atp7b knockout mouse and the Labrador retriever. The existing models of WD all show good similarity to human hepatic WD and have been helpful in developing an improved understanding of the human disease. As mammals, the mouse, rat and canine models also benefit from high homology to the human genome. However, important differences exist between these mammalian models and human disease, particularly the absence of a convincing neurological phenotype. This review will first provide an overview of our current knowledge of the orthologous genes encoding ATP7B and the closely related ATP7A protein in C. elegans, Drosophila and zebrafish (Danio rerio) and then summarise key characteristics of rodent and larger mammalian models of ATP7B-deficiency.
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Affiliation(s)
- Emily Reed
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Baltimore, USA
| | | | - Oliver Bandmann
- Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Baltimore, USA
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12
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Groba SR, Guttmann S, Niemietz C, Bernick F, Sauer V, Hachmöller O, Karst U, Zischka H, Zibert A, Schmidt HH. Downregulation of hepatic multi-drug resistance protein 1 (MDR1) after copper exposure. Metallomics 2018; 9:1279-1287. [PMID: 28805879 DOI: 10.1039/c7mt00189d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Copper homeostasis is strictly regulated in mammalian cells. We investigated the adaptation of hepatocytes after long-term copper exposure. Copper-resistant hepatoma HepG2 cell lines lacking ATP7B were generated. Growth, copper accumulation, gene expression, and transport were determined. Hepatocyte-like cells derived from a Wilson disease (WD) patient and the liver of a WD animal model were also studied. The rapidly gained copper resistance was found to be stable, as subculturing of cells in the absence of added copper (weaning) did not restore copper sensitivity. Intracellular copper levels and the expression of MT1 and HSP70 were increased, whereas the expression of CTR1 was reduced. However, the values normalized after weaning. In contrast, downregulation of multi-drug resistance protein 1 (MDR1), encoding P-glycoprotein (P-gp), was shown to be permanent. Calcein assays confirmed the downregulation of MDR1 in the resistant cell lines. MDR1 knockdown by siRNA resulted in increased copper resistance and decreased intracellular copper. Treatment of the resistant cells with verapamil, a known inducer of MDR1, was followed by increased copper-induced toxicity. Downregulation of MDR1 was also observed in hepatocyte-like cells derived from a WD patient after copper exposure. In addition, MDR1 was downregulated in Long-Evans Cinnamon rats when the liver copper was elevated. The results indicate that downregulation of MDR1 is an adaptation of hepatic cells after sustained copper exposure when ATP7B is non-functional. Our data add to the versatile functions of MDR1 in the hepatocyte and may have an impact on the treatment of copper-related diseases, prominently WD.
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Affiliation(s)
- Sara Reinartz Groba
- Klinik für Transplantationsmedizin, Universitätsklinikum Münster, Albert-Schweitzer-Campus 1, Gebäude A14, 48149 Münster, Germany.
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13
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Gupta A, Das S, Ray K. A glimpse into the regulation of the Wilson disease protein, ATP7B, sheds light on the complexity of mammalian apical trafficking pathways. Metallomics 2018; 10:378-387. [PMID: 29473088 DOI: 10.1039/c7mt00314e] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Wilson disease (WD), a Mendelian disorder of copper metabolism caused by mutations in the ATP7B gene, manifests a large spectrum of phenotypic variability. This phenomenon of extensive symptom variation is not frequently associated with a monogenic disorder. We hypothesize that the phenotypic variability in WD is primarily driven by the variations in interacting proteins that regulate the ATP7B function and localization in the cell. Based on existing literature, we delineated a potential molecular mechanism for ATP7B mediated copper transport in the milieu of its interactome, its dysfunction in WD and the resulting variability in the phenotypic manifestation. Understanding the copper-induced apical trafficking of ATP7B also significantly contributes to the appreciation of the complexities of the ligand-induced transport pathway. We believe that this holistic view of WD will pave the way for a better opportunity for rational drug design and therapeutics.
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Affiliation(s)
- Arnab Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research - Kolkata (IISER K), Mohanpur 741246, West Bengal, India.
| | - Santanu Das
- Department of Biological Sciences, Indian Institute of Science Education and Research - Kolkata (IISER K), Mohanpur 741246, West Bengal, India.
| | - Kunal Ray
- Academy of Scientific & Innovative Research (AcSIR), CSIR - HRDC Campus, Ghaziabad, Uttar Pradesh - 201002, India
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14
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Guttmann S, Bernick F, Naorniakowska M, Michgehl U, Groba SR, Socha P, Zibert A, Schmidt HH. Functional Characterization of Novel ATP7B Variants for Diagnosis of Wilson Disease. Front Pediatr 2018; 6:106. [PMID: 29761093 PMCID: PMC5937294 DOI: 10.3389/fped.2018.00106] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 04/03/2018] [Indexed: 12/14/2022] Open
Abstract
Background: Diagnosis of rare Wilson disease (WD) in pediatric patients is difficult, in particular when hepatic manifestation is absent. Genetic analysis of ATP7B represents the single major determinant of the diagnostic scoring system in WD children having mild symptoms. Objectives: To assess the impact of molecularly expressed ATP7B gene products in order to assist diagnosis of Wilson disease in pediatric patients having a novel mutation and subtle neuropsychiatric disease. Methods: The medical history, clinical presentation, biochemical parameters, and the genetic analysis of ATP7B were determined. Due to ambiguous clinical and biochemical findings and identification of a novel compound ATP7B mutation with unknown disease-causing status, a molecular analysis of the ATP7B gene products in a previously well characterized cell model was performed. Results: The ATP7B variants were transgenically expressed and the respective gene function molecularly characterized. Despite normal mRNA expression, low ATP7B protein expression of the mutants p.L168P and p.S1423N was observed (34.3 ± 8% and 66.0 ± 8%, respectively). Copper exposure did not result in decreased viability of transgenic cells as compared to wild type. Intracellular copper accumulation was reduced (≤47.9 ± 8%) and intracellular protein trafficking was impaired. Conclusion: Our report suggests that functional characterization of novel ATP7B mutants can assist diagnosis; however mild functional impairments of ATP7B variants may hamper the value of such approaches.
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Affiliation(s)
- Sarah Guttmann
- Medizinische Klinik B für Gastroenterologie und Hepatologie, Universitätsklinikum Münster, Münster, Germany
| | - Friedrich Bernick
- Medizinische Klinik B für Gastroenterologie und Hepatologie, Universitätsklinikum Münster, Münster, Germany
| | - Magdalena Naorniakowska
- Department of Gastroenterology, Hepatology, Nutritional Disorders and Pediatrics, The Children's Memorial Health Institute, Warsaw, Poland
| | - Ulf Michgehl
- Internal Medicine D, Molecular Nephrology, University Hospital of Münster, Münster, Germany
| | - Sara Reinartz Groba
- Medizinische Klinik B für Gastroenterologie und Hepatologie, Universitätsklinikum Münster, Münster, Germany
| | - Piotr Socha
- Internal Medicine D, Molecular Nephrology, University Hospital of Münster, Münster, Germany
| | - Andree Zibert
- Medizinische Klinik B für Gastroenterologie und Hepatologie, Universitätsklinikum Münster, Münster, Germany
| | - Hartmut H Schmidt
- Medizinische Klinik B für Gastroenterologie und Hepatologie, Universitätsklinikum Münster, Münster, Germany
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