1
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Gale J, Aizenman E. The physiological and pathophysiological roles of copper in the nervous system. Eur J Neurosci 2024; 60:3505-3543. [PMID: 38747014 DOI: 10.1111/ejn.16370] [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: 11/12/2023] [Revised: 02/28/2024] [Accepted: 04/10/2024] [Indexed: 07/06/2024]
Abstract
Copper is a critical trace element in biological systems due the vast number of essential enzymes that require the metal as a cofactor, including cytochrome c oxidase, superoxide dismutase and dopamine-β-hydroxylase. Due its key role in oxidative metabolism, antioxidant defence and neurotransmitter synthesis, copper is particularly important for neuronal development and proper neuronal function. Moreover, increasing evidence suggests that copper also serves important functions in synaptic and network activity, the regulation of circadian rhythms, and arousal. However, it is important to note that because of copper's ability to redox cycle and generate reactive species, cellular levels of the metal must be tightly regulated to meet cellular needs while avoiding copper-induced oxidative stress. Therefore, it is essential that the intricate system of copper transporters, exporters, copper chaperones and copper trafficking proteins function properly and in coordinate fashion. Indeed, disorders of copper metabolism such as Menkes disease and Wilson disease, as well as diseases linked to dysfunction of copper-requiring enzymes, such as SOD1-linked amyotrophic lateral sclerosis, demonstrate the dramatic neurological consequences of altered copper homeostasis. In this review, we explore the physiological importance of copper in the nervous system as well as pathologies related to improper copper handling.
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Affiliation(s)
- Jenna Gale
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Elias Aizenman
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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2
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Ruturaj, Mishra M, Saha S, Maji S, Rodriguez-Boulan E, Schreiner R, Gupta A. Regulation of the apico-basolateral trafficking polarity of the homologous copper-ATPases ATP7A and ATP7B. J Cell Sci 2024; 137:jcs261258. [PMID: 38032054 PMCID: PMC10729821 DOI: 10.1242/jcs.261258] [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: 04/19/2023] [Accepted: 10/05/2023] [Indexed: 12/01/2023] Open
Abstract
The homologous P-type copper-ATPases (Cu-ATPases) ATP7A and ATP7B are the key regulators of copper homeostasis in mammalian cells. In polarized epithelia, upon copper treatment, ATP7A and ATP7B traffic from the trans-Golgi network (TGN) to basolateral and apical membranes, respectively. We characterized the sorting pathways of Cu-ATPases between TGN and the plasma membrane and identified the machinery involved. ATP7A and ATP7B reside on distinct domains of TGN in limiting copper conditions, and in high copper, ATP7A traffics to basolateral membrane, whereas ATP7B traverses common recycling, apical sorting and apical recycling endosomes en route to apical membrane. Mass spectrometry identified regulatory partners of ATP7A and ATP7B that include the adaptor protein-1 complex. Upon knocking out pan-AP-1, sorting of both Cu-ATPases is disrupted. ATP7A loses its trafficking polarity and localizes on both apical and basolateral surfaces in high copper. By contrast, ATP7B loses TGN retention but retained its trafficking polarity to the apical domain, which became copper independent. Using isoform-specific knockouts, we found that the AP-1A complex provides directionality and TGN retention for both Cu-ATPases, whereas the AP-1B complex governs copper-independent trafficking of ATP7B solely. Trafficking phenotypes of Wilson disease-causing ATP7B mutants that disrupts putative ATP7B-AP1 interaction further substantiates the role of AP-1 in apical sorting of ATP7B.
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Affiliation(s)
- Ruturaj
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Monalisa Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Soumyendu Saha
- 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
| | - Enrique Rodriguez-Boulan
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, NY 10021, USA
| | - Ryan Schreiner
- Division of Regenerative Medicine, Department of Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - 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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Palmgren M. P-type ATPases: Many more enigmas left to solve. J Biol Chem 2023; 299:105352. [PMID: 37838176 PMCID: PMC10654040 DOI: 10.1016/j.jbc.2023.105352] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 10/02/2023] [Accepted: 10/05/2023] [Indexed: 10/16/2023] Open
Abstract
P-type ATPases constitute a large ancient super-family of primary active pumps that have diverse substrate specificities ranging from H+ to phospholipids. The significance of these enzymes in biology cannot be overstated. They are structurally related, and their catalytic cycles alternate between high- and low-affinity conformations that are induced by phosphorylation and dephosphorylation of a conserved aspartate residue. In the year 1988, all P-type sequences available by then were analyzed and five major families, P1 to P5, were identified. Since then, a large body of knowledge has accumulated concerning the structure, function, and physiological roles of members of these families, but only one additional family, P6 ATPases, has been identified. However, much is still left to be learned. For each family a few remaining enigmas are presented, with the intention that they will stimulate interest in continued research in the field. The review is by no way comprehensive and merely presents personal views with a focus on evolution.
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Affiliation(s)
- Michael Palmgren
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
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4
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Karpenko MN, Muruzheva ZM, Ilyechova EY, Babich PS, Puchkova LV. Abnormalities in Copper Status Associated with an Elevated Risk of Parkinson's Phenotype Development. Antioxidants (Basel) 2023; 12:1654. [PMID: 37759957 PMCID: PMC10525645 DOI: 10.3390/antiox12091654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 08/10/2023] [Accepted: 08/16/2023] [Indexed: 09/29/2023] Open
Abstract
In the last 15 years, among the many reasons given for the development of idiopathic forms of Parkinson's disease (PD), copper imbalance has been identified as a factor, and PD is often referred to as a copper-mediated disorder. More than 640 papers have been devoted to the relationship between PD and copper status in the blood, which include the following markers: total copper concentration, enzymatic ceruloplasmin (Cp) concentration, Cp protein level, and non-ceruloplasmin copper level. Most studies measure only one of these markers. Therefore, the existence of a correlation between copper status and the development of PD is still debated. Based on data from the published literature, meta-analysis, and our own research, it is clear that there is a connection between the development of PD symptoms and the number of copper atoms, which are weakly associated with the ceruloplasmin molecule. In this work, the link between the risk of developing PD and various inborn errors related to copper metabolism, leading to decreased levels of oxidase ceruloplasmin in the circulation and cerebrospinal fluid, is discussed.
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Affiliation(s)
- Marina N. Karpenko
- I.P. Pavlov Department of Physiology, Research Institute of Experimental Medicine, 197376 St. Petersburg, Russia; (M.N.K.); (Z.M.M.)
- Institute of Biomedical Systems and Biotechnology, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia;
| | - Zamira M. Muruzheva
- I.P. Pavlov Department of Physiology, Research Institute of Experimental Medicine, 197376 St. Petersburg, Russia; (M.N.K.); (Z.M.M.)
- State Budgetary Institution of Health Care “Leningrad Regional Clinical Hospital”, 194291 St. Petersburg, Russia
| | - Ekaterina Yu. Ilyechova
- Institute of Biomedical Systems and Biotechnology, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia;
- Research Center of Advanced Functional Materials and Laser Communication Systems, ADTS Institute, ITMO University, 197101 St. Petersburg, Russia
- Department of Molecular Genetics, Research Institute of Experimental Medicine, 197376 St. Petersburg, Russia
| | - Polina S. Babich
- Department of Zoology and Genetics, Faculty of Biology, Herzen State Pedagogical University of Russia, 191186 St. Petersburg, Russia;
| | - Ludmila V. Puchkova
- Institute of Biomedical Systems and Biotechnology, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia;
- Research Center of Advanced Functional Materials and Laser Communication Systems, ADTS Institute, ITMO University, 197101 St. Petersburg, Russia
- Department of Molecular Genetics, Research Institute of Experimental Medicine, 197376 St. Petersburg, Russia
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5
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Orädd F, Steffen JH, Gourdon P, Andersson M. Copper binding leads to increased dynamics in the regulatory N-terminal domain of full-length human copper transporter ATP7B. PLoS Comput Biol 2022; 18:e1010074. [PMID: 36070320 PMCID: PMC9484656 DOI: 10.1371/journal.pcbi.1010074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 09/19/2022] [Accepted: 08/17/2022] [Indexed: 11/25/2022] Open
Abstract
ATP7B is a human copper-transporting P1B-type ATPase that is involved in copper homeostasis and resistance to platinum drugs in cancer cells. ATP7B consists of a copper-transporting core and a regulatory N-terminal tail that contains six metal-binding domains (MBD1-6) connected by linker regions. The MBDs can bind copper, which changes the dynamics of the regulatory domain and activates the protein, but the underlying mechanism remains unknown. To identify possible copper-specific structural dynamics involved in transport regulation, we constructed a model of ATP7B spanning the N-terminal tail and core catalytic domains and performed molecular dynamics (MD) simulations with (holo) and without (apo) copper ions bound to the MBDs. In the holo protein, MBD2, MBD3 and MBD5 showed enhanced mobilities, which resulted in a more extended N-terminal regulatory region. The observed separation of MBD2 and MBD3 from the core protein supports a mechanism where copper binding activates the ATP7B protein by reducing interactions among MBD1-3 and between MBD1-3 and the core protein. We also observed an increased interaction between MBD5 and the core protein that brought the copper-binding site of MBD5 closer to the high-affinity internal copper-binding site in the core protein. The simulation results assign specific, mechanistic roles to the metal-binding domains involved in ATP7B regulation that are testable in experimental settings. Living organisms depend upon active transport against gradients across biological membranes for survival. Such transport can be accomplished by ATP-dependent membrane protein transporters for which the activity must be regulated to maintain optimal concentrations in the cellular compartments. The regulatory mechanisms often involve structural responses inherent to the protein structure, which because of their dynamic nature can be hard to assess experimentally. A prime example is regulation of cellular copper levels by a copper-binding tail in the human copper transporter ATP7B. Dysregulation can cause severe diseases, for example the copper metabolism disorder Wilson’s disease, which is caused by mutations in ATP7B regulation machinery. Due to the practical difficulties in working with membrane proteins, most studies of ATP7B have been conducted in the absence of the membrane-bound protein core. Here, we used computer simulations of full-length ATP7B to study how structural dynamics in the regulatory tail differ between copper-bound and copper-free states. Copper induced increased dynamics in the tail, resulting in an overall movement towards the ion-binding site in the protein core. The simulations identified several, hitherto not reported, interactions between the regulatory tail and the protein core that can be targeted experimentally to enhance our understanding of this medically relevant regulatory mechanism.
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Affiliation(s)
- Fredrik Orädd
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - Jonas Hyld Steffen
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Pontus Gourdon
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Experimental Medical Science, Lund University, Lund, Sweden
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6
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Golgi Metal Ion Homeostasis in Human Health and Diseases. Cells 2022; 11:cells11020289. [PMID: 35053405 PMCID: PMC8773785 DOI: 10.3390/cells11020289] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 12/31/2021] [Accepted: 01/11/2022] [Indexed: 12/24/2022] Open
Abstract
The Golgi apparatus is a membrane organelle located in the center of the protein processing and trafficking pathway. It consists of sub-compartments with distinct biochemical compositions and functions. Main functions of the Golgi, including membrane trafficking, protein glycosylation, and sorting, require a well-maintained stable microenvironment in the sub-compartments of the Golgi, along with metal ion homeostasis. Metal ions, such as Ca2+, Mn2+, Zn2+, and Cu2+, are important cofactors of many Golgi resident glycosylation enzymes. The homeostasis of metal ions in the secretory pathway, which is required for proper function and stress response of the Golgi, is tightly regulated and maintained by transporters. Mutations in the transporters cause human diseases. Here we provide a review specifically focusing on the transporters that maintain Golgi metal ion homeostasis under physiological conditions and their alterations in diseases.
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7
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Uhlemann EME, Lee W, Tonelli M, Dmitriev OY. At sixes and sevens: cryptic domain in the metal binding chain of the human copper transporter ATP7A. Biophys J 2021; 120:4600-4607. [PMID: 34461106 DOI: 10.1016/j.bpj.2021.08.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/27/2021] [Accepted: 08/25/2021] [Indexed: 10/20/2022] Open
Abstract
ATP7A and ATP7B are structurally similar but functionally distinct active copper transporters that regulate copper levels in the human cells and deliver copper to the biosynthetic pathways. Both proteins have a chain of six cytosolic metal-binding domains (MBDs) believed to be involved in the copper-dependent regulation of the activity and intracellular localization of these enzymes. Although all the MBDs are quite similar in structure, their spacing differs markedly between ATP7A and ATP7B. We show by NMR that the long polypeptide between MBD1 and MBD2 of ATP7A forms an additional seventh metastable domain, which we called HMA1A (heavy metal associated domain 1A). The structure of HMA1A resembles the MBDs but contains no copper-binding site. The HMA1A domain, which is unique to ATP7A, may modulate regulatory interactions between MBD1-3, contributing to the distinct functional properties of ATP7A and ATP7B.
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Affiliation(s)
- Eva-Maria E Uhlemann
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Woonghee Lee
- Department of Chemistry, University of Colorado, Denver, Colorado
| | - Marco Tonelli
- National Magnetic Resonance Facility at Madison, University of Wisconsin, Madison, Wisconsin
| | - Oleg Y Dmitriev
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
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8
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Maung MT, Carlson A, Olea-Flores M, Elkhadragy L, Schachtschneider KM, Navarro-Tito N, Padilla-Benavides T. The molecular and cellular basis of copper dysregulation and its relationship with human pathologies. FASEB J 2021; 35:e21810. [PMID: 34390520 DOI: 10.1096/fj.202100273rr] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 06/23/2021] [Accepted: 07/07/2021] [Indexed: 12/16/2022]
Abstract
Copper (Cu) is an essential micronutrient required for the activity of redox-active enzymes involved in critical metabolic reactions, signaling pathways, and biological functions. Transporters and chaperones control Cu ion levels and bioavailability to ensure proper subcellular and systemic Cu distribution. Intensive research has focused on understanding how mammalian cells maintain Cu homeostasis, and how molecular signals coordinate Cu acquisition and storage within organs. In humans, mutations of genes that regulate Cu homeostasis or facilitate interactions with Cu ions lead to numerous pathologic conditions. Malfunctions of the Cu+ -transporting ATPases ATP7A and ATP7B cause Menkes disease and Wilson disease, respectively. Additionally, defects in the mitochondrial and cellular distributions and homeostasis of Cu lead to severe neurodegenerative conditions, mitochondrial myopathies, and metabolic diseases. Cu has a dual nature in carcinogenesis as a promotor of tumor growth and an inducer of redox stress in cancer cells. Cu also plays role in cancer treatment as a component of drugs and a regulator of drug sensitivity and uptake. In this review, we provide an overview of the current knowledge of Cu metabolism and transport and its relation to various human pathologies.
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Affiliation(s)
- May T Maung
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT, USA
| | - Alyssa Carlson
- Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT, USA
| | - Monserrat Olea-Flores
- Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Guerrero, Guerrero, Mexico
| | - Lobna Elkhadragy
- Department of Radiology, University of Illinois at Chicago, Chicago, IL, USA
| | - Kyle M Schachtschneider
- Department of Radiology, University of Illinois at Chicago, Chicago, IL, USA.,Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, IL, USA.,National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Napoleon Navarro-Tito
- Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Guerrero, Guerrero, Mexico
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9
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ATP7A-Regulated Enzyme Metalation and Trafficking in the Menkes Disease Puzzle. Biomedicines 2021; 9:biomedicines9040391. [PMID: 33917579 PMCID: PMC8067471 DOI: 10.3390/biomedicines9040391] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/01/2021] [Accepted: 04/02/2021] [Indexed: 12/12/2022] Open
Abstract
Copper is vital for numerous cellular functions affecting all tissues and organ systems in the body. The copper pump, ATP7A is critical for whole-body, cellular, and subcellular copper homeostasis, and dysfunction due to genetic defects results in Menkes disease. ATP7A dysfunction leads to copper deficiency in nervous tissue, liver, and blood but accumulation in other tissues. Site-specific cellular deficiencies of copper lead to loss of function of copper-dependent enzymes in all tissues, and the range of Menkes disease pathologies observed can now be explained in full by lack of specific copper enzymes. New pathways involving copper activated lysosomal and steroid sulfatases link patient symptoms usually related to other inborn errors of metabolism to Menkes disease. Additionally, new roles for lysyl oxidase in activation of molecules necessary for the innate immune system, and novel adapter molecules that play roles in ERGIC trafficking of brain receptors and other proteins, are emerging. We here summarize the current knowledge of the roles of copper enzyme function in Menkes disease, with a focus on ATP7A-mediated enzyme metalation in the secretory pathway. By establishing mechanistic relationships between copper-dependent cellular processes and Menkes disease symptoms in patients will not only increase understanding of copper biology but will also allow for the identification of an expanding range of copper-dependent enzymes and pathways. This will raise awareness of rare patient symptoms, and thus aid in early diagnosis of Menkes disease patients.
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10
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Das S, Maji S, Ruturaj, Bhattacharya I, Saha T, Naskar N, Gupta A. Retromer retrieves the Wilson disease protein ATP7B from endolysosomes in a copper-dependent manner. J Cell Sci 2020; 133:jcs246819. [PMID: 33268466 PMCID: PMC7611186 DOI: 10.1242/jcs.246819] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Accepted: 11/19/2020] [Indexed: 12/31/2022] Open
Abstract
The Wilson disease protein, ATP7B maintains copper (herein referring to the Cu+ ion) homeostasis in the liver. ATP7B traffics from trans-Golgi network to endolysosomes to export excess copper. Regulation of ATP7B trafficking to and from endolysosomes is not well understood. We investigated the fate of ATP7B after copper export. At high copper levels, ATP7B traffics primarily to acidic, active hydrolase (cathepsin-B)-positive endolysosomes and, upon subsequent copper chelation, returns to the trans-Golgi network (TGN). At high copper, ATP7B colocalizes with endolysosomal markers and with a core member of retromer complex, VPS35. Knocking down VPS35 did not abrogate the copper export function of ATP7B or its copper-responsive anterograde trafficking to vesicles; rather upon subsequent copper chelation, ATP7B failed to relocalize to the TGN, which was rescued by overexpressing wild-type VPS35. Overexpressing mutants of the retromer complex-associated proteins Rab7A and COMMD1 yielded a similar non-recycling phenotype of ATP7B. At high copper, VPS35 and ATP7B are juxtaposed on the same endolysosome and form a large complex that is stabilized by in vivo photoamino acid labeling and UV-crosslinking. We demonstrate that retromer regulates endolysosome to TGN trafficking of copper transporter ATP7B in a manner that is dependent upon intracellular copper.
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Affiliation(s)
- Santanu Das
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
| | - Saptarshi Maji
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
| | - Ruturaj
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
| | - Indira Bhattacharya
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
| | - Tanusree Saha
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
| | - Nabanita Naskar
- Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
| | - Arnab Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, India
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11
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Shanbhag VC, Gudekar N, Jasmer K, Papageorgiou C, Singh K, Petris MJ. Copper metabolism as a unique vulnerability in cancer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1868:118893. [PMID: 33091507 DOI: 10.1016/j.bbamcr.2020.118893] [Citation(s) in RCA: 181] [Impact Index Per Article: 45.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/13/2020] [Accepted: 10/15/2020] [Indexed: 02/07/2023]
Abstract
The last 25 years have witnessed tremendous progress in identifying and characterizing proteins that regulate the uptake, intracellular trafficking and export of copper. Although dietary copper is required in trace amounts, sufficient quantities of this metal are needed to sustain growth and development in humans and other mammals. However, copper is also a rate-limiting nutrient for the growth and proliferation of cancer cells. Oral copper chelators taken with food have been shown to confer anti-neoplastic and anti-metastatic benefits in animals and humans. Recent studies have begun to identify specific roles for copper in pathways of oncogenic signaling and resistance to anti-neoplastic drugs. Here, we review the general mechanisms of cellular copper homeostasis and discuss roles of copper in cancer progression, highlighting metabolic vulnerabilities that may be targetable in the development of anticancer therapies.
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Affiliation(s)
- Vinit C Shanbhag
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, United States of America; The Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211, United States of America
| | - Nikita Gudekar
- Genetics Area Program, University of Missouri, Columbia, MO 65211, United States of America; The Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211, United States of America
| | - Kimberly Jasmer
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, United States of America; The Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211, United States of America
| | - Christos Papageorgiou
- Department of Medicine, University of Missouri, Columbia, MO 65211, United States of America
| | - Kamal Singh
- The Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211, United States of America; Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, United States of America
| | - Michael J Petris
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, United States of America; Department of Ophthalmology, University of Missouri, Columbia, MO 65211, United States of America; Genetics Area Program, University of Missouri, Columbia, MO 65211, United States of America; The Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211, United States of America.
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12
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Carotenuto R, Capriello T, Cofone R, Galdiero G, Fogliano C, Ferrandino I. Impact of copper in Xenopus laevis liver: Histological damages and atp7b downregulation. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 188:109940. [PMID: 31757510 DOI: 10.1016/j.ecoenv.2019.109940] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 11/07/2019] [Accepted: 11/09/2019] [Indexed: 06/10/2023]
Abstract
Copper is an essential micronutrient but its excess in the dietary can be toxic. Both copper deficiency and abundance can occur in natural conditions and can lead to pathological dysfunctions. Many of the toxic effects of copper, such as increased lipid peroxidation in cell membranes and DNA damage, are due to its role in the generation of oxygen free radicals. Copper is released into the environment by both natural sources and human activities and it can damage organisms and ecosystems. In the present work the effects of copper has been studied on Xenopus laevis, an interesting model organism, after three weeks of exposure at 1 mg/L of CuCl, concentration allowed in the water for human use. The effects of this metal were analysed on the liver at light microscope by Hematoxylin-Eosin, Mallory, Pas and Perls stainings to evaluate the general histology, the glycogen metabolism and presence of hemosiderin. Moreover the number and area of melanomoacrophages, known as inflammation parameters, were assessment. Finally, we investigated the expression of atp7b gene and localization of respective ATP7B protein, the membrane protein involved in Cu detoxication. The achieved results showed that copper, even at a low concentration, causes serious histological alterations of liver. It induces an increase in the size and number of melanomacrophages and higher amount of hemosiderin in the treated than controls. Moreover, it alters the gene expression and localization of ATP7B protein. The data are indicative that an exposition at low and chronic concentration of copper in Xenopus laevis damages seriously the liver. For this reason it's important to consider this metal one of the pollutants involved in the decline of the amphibians and for its possible effects in other vertebrates including humans.
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Affiliation(s)
- Rosa Carotenuto
- Department of Biology, University of Naples "Federico II", Naples, Italy
| | - Teresa Capriello
- Department of Biology, University of Naples "Federico II", Naples, Italy
| | - Rita Cofone
- Department of Biology, University of Naples "Federico II", Naples, Italy
| | - Giuseppe Galdiero
- Department of Biology, University of Naples "Federico II", Naples, Italy
| | - Chiara Fogliano
- Department of Biology, University of Naples "Federico II", Naples, Italy
| | - Ida Ferrandino
- Department of Biology, University of Naples "Federico II", Naples, Italy.
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13
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Tang N, Sandahl TD, Ott P, Kepp KP. Computing the Pathogenicity of Wilson's Disease ATP7B Mutations: Implications for Disease Prevalence. J Chem Inf Model 2019; 59:5230-5243. [PMID: 31751128 DOI: 10.1021/acs.jcim.9b00852] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Genetic variations in the gene encoding the copper-transport protein ATP7B are the primary cause of Wilson's disease. Controversially, clinical prevalence seems much smaller than the prevalence estimated by genetic screening tools, causing fear that many people are undiagnosed, although early diagnosis and treatment is essential. To address this issue, we benchmarked 16 state-of-the-art computational disease-prediction methods against established data of missense ATP7B mutations. Our results show that the quality of the methods varies widely. We show the importance of optimizing the threshold of the methods used to distinguish pathogenic from nonpathogenic mutations against data of clinically confirmed pathogenic and nonpathogenic mutations. We find that most methods use thresholds that predict too many ATP7B mutations to be pathogenic. Thus, our findings explain the current controversy on Wilson's disease prevalence because meta-analysis and text search methods include many computational estimates that lead to higher disease prevalence than clinically observed. As proteins and diseases differ widely, a one-size-fits-all threshold cannot distinguish pathogenic and nonpathogenic mutations efficiently, as shown here. We also show that amino acid changes with small evolutionary substitution probability, mainly due to amino acid volume, are more associated with the disease, implying a pathological effect on the conformational state of the protein, which could affect copper transport or adenosine triphosphate recognition and hydrolysis. These findings may be a first step toward a more quantitative genotype-phenotype relationship of Wilson's disease.
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Affiliation(s)
- Ning Tang
- DTU Chemistry , Technical University of Denmark , Kemitorvet 206 , 2800 Kongens Lyngby , Denmark
| | - Thomas D Sandahl
- Department of Hepatology and Gastroenterology , Aarhus University Hospital , 8200 Aarhus , Denmark
| | - Peter Ott
- Department of Hepatology and Gastroenterology , Aarhus University Hospital , 8200 Aarhus , Denmark
| | - Kasper P Kepp
- DTU Chemistry , Technical University of Denmark , Kemitorvet 206 , 2800 Kongens Lyngby , Denmark
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14
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Purkait K, Ruturaj, Mukherjee A, Gupta A. ATP7B Binds Ruthenium(II) p-Cymene Half-Sandwich Complexes: Role of Steric Hindrance and Ru-I Coordination in Rescuing the Sequestration. Inorg Chem 2019; 58:15659-15670. [PMID: 31657924 DOI: 10.1021/acs.inorgchem.9b02780] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ruthenium(II/III) complexes are predicted to be efficient alternatives to platinum drug-resistant cancers but have never been investigated for sequestration and efflux by Cu-ATPases (ATP7A or ATP7B) overexpressed in resistant cancer cells, although a major cause of platinum drug resistance is found to be sequestration of platinum chemotherapeutic agents by thiol donors glutathione (GSH) or the Cys-X-X-Cys (CXXC) motifs in the Cu-ATPases in cytosol. Here, we show for the first time that ATP7B efficiently sequesters ruthenium(II) η6-p-cymene complexes. We present seven complexes, [RuII(η6-p-cym)(L)X](PF6) (1-7; L = L1-L3, X = Cl, Br, and I), out of which two resists deactivation by the cellular thiol, glutathione (GSH). The results show that Ru-I coordination and a moderate steric factor increase resistance to GSH and the CXXC motif. RuII-I-coordinated 3 and 7 showed resistance to sequestration by ATP7B. 3 displays highest resistance against GSH and does not trigger ATP7B trafficking in the liver cancer cell line. It escapes ATP7B-mediated sequestration and triggers apoptosis. Thus, with a suitable bidentate ligand and iodido leaving group, RuII(η6-p-cym) complexes may display strong kinetic inertness to inhibit the ATP7B detoxification pathway. Inductively coupled plasma mass spectrometry data show higher retention of 3 and 7 inside the cell with time compared to 4, supporting ATP7B-mediated sequestration.
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15
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Petruzzelli R, Polishchuk RS. Activity and Trafficking of Copper-Transporting ATPases in Tumor Development and Defense against Platinum-Based Drugs. Cells 2019; 8:E1080. [PMID: 31540259 PMCID: PMC6769697 DOI: 10.3390/cells8091080] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 09/10/2019] [Accepted: 09/12/2019] [Indexed: 02/06/2023] Open
Abstract
Membrane trafficking pathways emanating from the Golgi regulate a wide range of cellular processes. One of these is the maintenance of copper (Cu) homeostasis operated by the Golgi-localized Cu-transporting ATPases ATP7A and ATP7B. At the Golgi, these proteins supply Cu to newly synthesized enzymes which use this metal as a cofactor to catalyze a number of vitally important biochemical reactions. However, in response to elevated Cu, the Golgi exports ATP7A/B to post-Golgi sites where they promote sequestration and efflux of excess Cu to limit its potential toxicity. Growing tumors actively consume Cu and employ ATP7A/B to regulate the availability of this metal for oncogenic enzymes such as LOX and LOX-like proteins, which confer higher invasiveness to malignant cells. Furthermore, ATP7A/B activity and trafficking allow tumor cells to detoxify platinum (Pt)-based drugs (like cisplatin), which are used for the chemotherapy of different solid tumors. Despite these noted activities of ATP7A/B that favor oncogenic processes, the mechanisms that regulate the expression and trafficking of Cu ATPases in malignant cells are far from being completely understood. This review summarizes current data on the role of ATP7A/B in the regulation of Cu and Pt metabolism in malignant cells and outlines questions and challenges that should be addressed to understand how ATP7A and ATP7B trafficking mechanisms might be targeted to counteract tumor development.
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Affiliation(s)
- Raffaella Petruzzelli
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy.
| | - Roman S Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy.
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16
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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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17
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Stalke A, Pfister ED, Baumann U, Eilers M, Schäffer V, Illig T, Auber B, Schlegelberger B, Brackmann R, Prokisch H, Krooss S, Bohne J, Skawran B. Homozygous frame shift variant in ATP7B exon 1 leads to bypass of nonsense-mediated mRNA decay and to a protein capable of copper export. Eur J Hum Genet 2019; 27:879-887. [PMID: 30723317 DOI: 10.1038/s41431-019-0345-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 12/06/2018] [Accepted: 01/05/2019] [Indexed: 12/13/2022] Open
Abstract
Wilson disease (WD) is an autosomal recessive disease of copper excess due to pathogenic variants in the ATP7B gene coding for a copper-transporting ATPase. We present a 5-year-old girl with the homozygous frame shift variant NM_000053.3: c.19_20del in exon 1 of ATP7B (consecutive exon numbering with c.1 as first nucleotide of exon 1), detected by whole-exome sequencing as a secondary finding. The variant leads to a premature termination codon in exon 2. The girl exhibited no WD symptoms and no abnormalities in liver biopsy. ATP7B liver mRNA expression was comparable to healthy controls suggesting that nonsense-mediated mRNA decay (NMD) could be bypassed by the mechanism of translation reinitiation. To verify this hypothesis, a CMV-driven ATP7B minigene (pcDNA3) was equipped with the authentic ATP7B 5' untranslated region and a truncated intron 2. We introduced c.19_20del by site-directed mutagenesis and overexpressed the constructs in HEK293T cells. We analyzed ATP7B expression by qRT-PCR, northern and western blot, and examined protein function by copper export capacity assays. Northern blot, qRT-PCR, and western blot revealed that c.19_20del ATP7B mRNA and protein is expressed in size and amount comparable to wild-type. Copper export capacity was also comparable to wild-type. Our results indicate that c.19_20del in ATP7B is able to bypass NMD by translation reinitiation, demonstrating that the classification of truncating variants as pathogenic without additional investigations should be done carefully.
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Affiliation(s)
- Amelie Stalke
- Department of Human Genetics, Hannover Medical School, Hannover, Germany. .,Division of Pediatric Gastroenterology and Hepatology, Department of Kidney, Liver and Metabolic Disease, Hannover Medical School, Hannover, Germany.
| | - Eva-Doreen Pfister
- Division of Pediatric Gastroenterology and Hepatology, Department of Kidney, Liver and Metabolic Disease, Hannover Medical School, Hannover, Germany
| | - Ulrich Baumann
- Division of Pediatric Gastroenterology and Hepatology, Department of Kidney, Liver and Metabolic Disease, Hannover Medical School, Hannover, Germany
| | - Marlies Eilers
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Vera Schäffer
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Thomas Illig
- Department of Human Genetics, Hannover Medical School, Hannover, Germany.,Hannover Unified Biobank, Hannover Medical School, Hannover, Germany
| | - Bernd Auber
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | | | - Renate Brackmann
- Department of Child and Adolescent Medicine, Klinikum Herford, Herford, Germany
| | - Holger Prokisch
- Institute of Human Genetics, Helmholtz Center Munich, Neuherberg, Germany.,Institute of Human Genetics, Technical University Munich, Munich, Germany
| | - Simon Krooss
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Jens Bohne
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Britta Skawran
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
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18
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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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19
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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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20
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Ariöz C, Li Y, Wittung-Stafshede P. The six metal binding domains in human copper transporter, ATP7B: molecular biophysics and disease-causing mutations. Biometals 2017; 30:823-840. [PMID: 29063292 PMCID: PMC5684295 DOI: 10.1007/s10534-017-0058-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 10/05/2017] [Indexed: 12/16/2022]
Abstract
Wilson Disease (WD) is a hereditary genetic disorder, which coincides with a dysfunctional copper (Cu) metabolism caused by mutations in ATP7B, a membrane-bound P1B-type ATPase responsible for Cu export from hepatic cells. The N-terminal part (~ 600 residues) of the multi-domain 1400-residue ATP7B constitutes six metal binding domains (MBDs), each of which can bind a copper ion, interact with other ATP7B domains as well as with different proteins. Although the ATP7B's MBDs have been investigated in vitro and in vivo intensively, it remains unclear how these domains modulate overall structure, dynamics, stability and function of ATP7B. The presence of six MBDs is unique to mammalian ATP7B homologs, and many WD causing missense mutations are found in these domains. Here, we have summarized previously reported in vitro biophysical data on the MBDs of ATP7B and WD point mutations located in these domains. Besides the demonstration of where the research field stands today, this review showcasts the need for further biophysical investigation about the roles of MBDs in ATP7B function. Molecular mechanisms of ATP7B are important not only in the development of new WD treatment but also for other aspects of human physiology where Cu transport plays a role.
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Affiliation(s)
- Candan Ariöz
- Department of Biology and Biological Engineering, Division of Chemical Biology, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden
| | - Yaozong Li
- Department of Chemistry, Umeå University, Kemihuset A, Linnaeus väg 10, 901 87 Umeå, Sweden
| | - Pernilla Wittung-Stafshede
- Department of Biology and Biological Engineering, Division of Chemical Biology, Chalmers University of Technology, Kemigården 4, 412 96 Gothenburg, Sweden
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21
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Yu CH, Yang N, Bothe J, Tonelli M, Nokhrin S, Dolgova NV, Braiterman L, Lutsenko S, Dmitriev OY. The metal chaperone Atox1 regulates the activity of the human copper transporter ATP7B by modulating domain dynamics. J Biol Chem 2017; 292:18169-18177. [PMID: 28900031 DOI: 10.1074/jbc.m117.811752] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 09/01/2017] [Indexed: 01/28/2023] Open
Abstract
The human transporter ATP7B delivers copper to the biosynthetic pathways and maintains copper homeostasis in the liver. Mutations in ATP7B cause the potentially fatal hepatoneurological disorder Wilson disease. The activity and intracellular localization of ATP7B are regulated by copper, but the molecular mechanism of this regulation is largely unknown. We show that the copper chaperone Atox1, which delivers copper to ATP7B, and the group of the first three metal-binding domains (MBD1-3) are central to the activity regulation of ATP7B. Atox1-Cu binding to ATP7B changes domain dynamics and interactions within the MBD1-3 group and activates ATP hydrolysis. To understand the mechanism linking Atox1-MBD interactions and enzyme activity, we have determined the MBD1-3 conformational space using small angle X-ray scattering and identified changes in MBD dynamics caused by apo-Atox1 and Atox1-Cu by solution NMR. The results show that copper transfer from Atox1 decreases domain interactions within the MBD1-3 group and increases the mobility of the individual domains. The N-terminal segment of MBD1-3 was found to interact with the nucleotide-binding domain of ATP7B, thus physically coupling the domains involved in copper binding and those involved in ATP hydrolysis. Taken together, the data suggest a regulatory mechanism in which Atox1-mediated copper transfer activates ATP7B by releasing inhibitory constraints through increased freedom of MBD1-3 motions.
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Affiliation(s)
- Corey H Yu
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Nan Yang
- the Department of Physiology, Johns Hopkins Medical University, Baltimore, Maryland 21205, and
| | - Jameson Bothe
- the National Magnetic Resonance Facility at Madison, University of Wisconsin, Madison, Wisconsin 53706
| | - Marco Tonelli
- the National Magnetic Resonance Facility at Madison, University of Wisconsin, Madison, Wisconsin 53706
| | - Sergiy Nokhrin
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Natalia V Dolgova
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Lelita Braiterman
- the Department of Physiology, Johns Hopkins Medical University, Baltimore, Maryland 21205, and
| | - Svetlana Lutsenko
- the Department of Physiology, Johns Hopkins Medical University, Baltimore, Maryland 21205, and
| | - Oleg Y Dmitriev
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada,
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22
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Yu CH, Dolgova NV, Dmitriev OY. Dynamics of the metal binding domains and regulation of the human copper transporters ATP7B and ATP7A. IUBMB Life 2017; 69:226-235. [DOI: 10.1002/iub.1611] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 02/03/2017] [Indexed: 01/20/2023]
Affiliation(s)
- Corey H. Yu
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
| | - Natalia V. Dolgova
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
| | - Oleg Y. Dmitriev
- Department of Biochemistry; University of Saskatchewan; Saskatoon SK Canada
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23
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Phelps M, Stuelsatz P, Yablonka-Reuveni Z. Expression profile and overexpression outcome indicate a role for βKlotho in skeletal muscle fibro/adipogenesis. FEBS J 2016; 283:1653-68. [PMID: 26881702 DOI: 10.1111/febs.13682] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 01/29/2016] [Accepted: 02/12/2016] [Indexed: 12/01/2022]
Abstract
Regeneration of skeletal muscles is required throughout life to ensure optimal performance. Therefore, a better understanding of the resident cells involved in muscle repair is essential. Muscle repair relies on satellite cells (SCs), the resident myogenic progenitors, but also involves the contribution of interstitial cells including fibro/adipocyte progenitors (FAPs). To elucidate the role of the fibroblast growth factor (FGF) signaling in these two cell populations, we previously analyzed freshly isolated cells for their FGF receptor (FGFR) signature. Transcript analysis of the four Fgfr genes revealed distinct expression profiles for SCs and FAPs, raising the possibility that these two cell types have different FGF-mediated processes. Here, we pursued this hypothesis exploring the role of the Klotho genes, whose products are known to function as FGFR co-receptors for the endocrine FGF subfamily. Isolated SC and FAP populations were analyzed in culture, exhibiting spontaneous myogenic or adipogenic differentiation, respectively. αKlotho expression was not detected in either population. βKlotho expression, while not detected in SCs, was strongly upregulated in FAPs entering adipogenic differentiation, coinciding with expression of a panel of adipogenic genes and preceding the appearance of intracellular lipid droplets. Overexpression of βKlotho in mouse cell line models enhanced adipogenesis in NIH3T3 fibroblasts but had no effect on C2C12 myogenic cells. Our study supports a pro-adipogenic role for βKlotho in skeletal muscle fibro/adipogenesis and calls for further research on involvement of the FGF-FGFR-βKlotho axis in the fibro/adipogenic infiltration associated with functional deterioration of skeletal muscle in aging and muscular dystrophy.
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Affiliation(s)
- Michael Phelps
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA
| | - Pascal Stuelsatz
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA
| | - Zipora Yablonka-Reuveni
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA
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24
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Gupta A, Schell MJ, Bhattacharjee A, Lutsenko S, Hubbard AL. Myosin Vb mediates Cu+ export in polarized hepatocytes. J Cell Sci 2016; 129:1179-89. [PMID: 26823605 DOI: 10.1242/jcs.175307] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 01/20/2016] [Indexed: 02/06/2023] Open
Abstract
The cellular machinery responsible for Cu(+)-stimulated delivery of the Wilson-disease-associated protein ATP7B to the apical domain of hepatocytes is poorly understood. We demonstrate that myosin Vb regulates the Cu(+)-stimulated delivery of ATP7B to the apical domain of polarized hepatic cells, and that disruption of the ATP7B-myosin Vb interaction reduces the apical surface expression of ATP7B. Overexpression of the myosin Vb tail, which competes for binding of subapical cargos to myosin Vb bound to subapical actin, disrupted the surface expression of ATP7B, leading to reduced cellular Cu(+) export. The myosin-Vb-dependent targeting step occurred in parallel with hepatocyte-like polarity. If the myosin Vb tail was expressed acutely in cells just prior to the establishment of polarity, it appeared as part of an intracellular apical compartment, centered on γ-tubulin. ATP7B became selectively arrested in this compartment at high [Cu(+)] in the presence of myosin Vb tail, suggesting that these compartments are precursors of donor-acceptor transfer stations for apically targeted cargos of myosin Vb. Our data suggest that reduced hepatic Cu(+) clearance in idiopathic non-Wilsonian types of disease might be associated with the loss of function of myosin Vb.
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Affiliation(s)
- Arnab Gupta
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Michael J Schell
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
| | | | - Svetlana Lutsenko
- Department of Physiology, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Ann L Hubbard
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD 21205, USA
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25
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Lalioti V, Peiró R, Pérez-Berlanga M, Tsuchiya Y, Muñoz A, Villalba T, Sanchez C, Sandoval IV. Basolateral sorting and transcytosis define the Cu+-regulated translocation of ATP7B to the bile canaliculus. J Cell Sci 2016; 129:2190-201. [DOI: 10.1242/jcs.184663] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 03/28/2016] [Indexed: 01/22/2023] Open
Abstract
The Cu+ pump ATP7B plays an irreplaceable role in the elimination of excess Cu+ by the hepatocyte into the bile. The traffic and site of ATP7B action is a subject of controversy. One current proposal is that an increase in intracellular Cu+ results in the translocation of ATP7B to the lysosomes and excretion of excess Cu+ by lysosomal mediated exocytosis at the bile canaliculus. Here we show that ATP7B is transported from the trans-Golgi network to the bile canaliculus by basolateral sorting and endocytosis, and microtubule mediated transcytosis through the subapical compartment. Trafficking ATP7B is not incorporated into lysosomes and addition of Cu+ does not cause relocalization of lysosomes and the appearance of lysosome markers in the bile canaliculus. Our data describes the pathway of the Cu+-mediated transport of ATP7B from the TGN to the bile canaliculus and indicates that the bile canaliculus is the prime site of ATP7B action in the elimination of excess Cu+.
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Affiliation(s)
- Vasiliki Lalioti
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Ramón Peiró
- Genomics and Massive Sequencing, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Manuela Pérez-Berlanga
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Yo Tsuchiya
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Angeles Muñoz
- Optical and Confocal Microscopy, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Teresa Villalba
- Optical and Confocal Microscopy, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Carlos Sanchez
- Optical and Confocal Microscopy, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
| | - Ignacio V. Sandoval
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain
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26
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Zhu M, Dong Y, Ni W, Wu ZY. Defective roles of ATP7B missense mutations in cellular copper tolerance and copper excretion. Mol Cell Neurosci 2015; 67:31-6. [PMID: 26032686 DOI: 10.1016/j.mcn.2015.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 05/05/2015] [Accepted: 05/27/2015] [Indexed: 11/29/2022] Open
Abstract
Wilson's disease (WD) is a hereditary disorder of copper metabolism resulting from mutations within ATP7B. Clinical investigations showed that ATP7B missense mutations cause a wide variety of symptoms in WD patients, which implies that those mutations might affect ATP7B function in a number of ways and each would have deleterious consequences on normal copper distribution and lead to WD. Nonetheless, it is still unknown about the influences of those mutations on ATP7B function of increasing copper excretion and enhancing cellular copper tolerance. Here we established the stable expression cell lines of wild-type (WT) ATP7B and its four missense mutants (R778L, R919G, T935M and P992L), tested cellular copper tolerance and copper excretion using those cell lines, and also observed cellular distribution of WT ATP7B proteins and those mutants in transiently transfected cells. We found that extrinsic expressing WT ATP7B reduced CuCl2-induced copper accumulation and enhanced cellular copper tolerance by accelerating copper excretion, which was selectively compromised by R778L and P992L mutations. Further investigation showed that R778L mutation disrupted the subcellular localization and trafficking of ATP7B proteins, whereas P992L mutation only affected the trafficking of ATP7B. This indicates that ATP7B missense mutants have distinct effects on cellular copper tolerance.
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Affiliation(s)
- Min Zhu
- Department of Neurology and Research Center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China; Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yi Dong
- Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Wang Ni
- Department of Neurology and Research Center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China
| | - Zhi-Ying Wu
- Department of Neurology and Research Center of Neurology in Second Affiliated Hospital, and the Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou, China.
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Braiterman LT, Gupta A, Chaerkady R, Cole RN, Hubbard AL. Communication between the N and C termini is required for copper-stimulated Ser/Thr phosphorylation of Cu(I)-ATPase (ATP7B). J Biol Chem 2015; 290:8803-19. [PMID: 25666620 DOI: 10.1074/jbc.m114.627414] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Indexed: 11/06/2022] Open
Abstract
The Wilson disease protein ATP7B exhibits copper-dependent trafficking. In high copper, ATP7B exits the trans-Golgi network and moves to the apical domain of hepatocytes where it facilitates elimination of excess copper through the bile. Copper levels also affect ATP7B phosphorylation. ATP7B is basally phosphorylated in low copper and becomes more phosphorylated ("hyperphosphorylated") in elevated copper. The functional significance of hyperphosphorylation remains unclear. We showed that hyperphosphorylation occurs even when ATP7B is restricted to the trans-Golgi network. We performed comprehensive phosphoproteomics of ATP7B in low versus high copper, which revealed that 24 Ser/Thr residues in ATP7B could be phosphorylated, and only four of these were copper-responsive. Most of the phosphorylated sites were found in the N- and C-terminal cytoplasmic domains. Using truncation and mutagenesis, we showed that inactivation or elimination of all six N-terminal metal binding domains did not block copper-dependent, reversible, apical trafficking but did block hyperphosphorylation in hepatic cells. We showed that nine of 15 Ser/Thr residues in the C-terminal domain were phosphorylated. Inactivation of 13 C-terminal phosphorylation sites reduced basal phosphorylation and eliminated hyperphosphorylation, suggesting that copper binding at the N terminus propagates to the ATP7B C-terminal region. C-terminal mutants with either inactivating or phosphomimetic substitutions showed little effect upon copper-stimulated trafficking, indicating that trafficking does not depend on phosphorylation at these sites. Thus, our studies revealed that copper-dependent conformational changes in the N-terminal region lead to hyperphosphorylation at C-terminal sites, which seem not to affect trafficking and may instead fine-tune copper sequestration.
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Affiliation(s)
| | | | - Raghothama Chaerkady
- the Mass Spectrometry and Proteomics Facility, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Robert N Cole
- the Mass Spectrometry and Proteomics Facility, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Ogra Y. Molecular mechanisms underlying copper homeostasis in Mammalian cells. Nihon Eiseigaku Zasshi 2015; 69:136-45. [PMID: 24858509 DOI: 10.1265/jjh.69.136] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Copper (Cu) is an essential metal for living organisms that utilize oxygen for respiration and is required as a cofactor of redox-regulating enzymes, such as superoxide dismutase, ceruloplasmin, lysyl oxidase, tyrosinase, and dopamine β-hydroxylase. However, the redox-active property of this metal may have toxic effects on cells due to the generation of harmful reactive oxygen species. Given these circumstances, it is said that cells have a dependable system for Cu homeostasis that efficiently distributes this essential metal to cuproenzymes, thereby preventing damage to proteins, nucleic acids, sugars, and lipids. In particular, influx, efflux, and intracellular distribution with maintenance of the oxidation state of Cu are strictly regulated. Several groups of Cu-regulating factors have been identified in mammalian cells, i.e., Cu transporters, Cu chaperones, Cu-binding proteins/peptides, and others. In this review, the features of the Cu-regulating factors are concisely examined in terms of molecular mechanisms underlying Cu homeostasis in cells.
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Affiliation(s)
- Yasumitsu Ogra
- Laboratory of Chemical Toxicology and Environmental Health, Showa Pharmaceutical University
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Nyasae LK, Schell MJ, Hubbard AL. Copper directs ATP7B to the apical domain of hepatic cells via basolateral endosomes. Traffic 2014; 15:1344-65. [PMID: 25243755 DOI: 10.1111/tra.12229] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/16/2014] [Indexed: 01/01/2023]
Abstract
Physiologic Cu levels regulate the intracellular location of the Cu ATPase ATP7B. Here, we determined the routes of Cu-directed trafficking of endogenous ATP7B in the polarized hepatic cell line WIF-B and in the liver in vivo. Copper (10 µm) caused ATP7B to exit the trans-Golgi network (TGN) in vesicles, which trafficked via large basolateral endosomes to the apical domain within 1 h. Although perturbants of luminal acidification had little effect on the TGN localization of ATP7B in low Cu, they blocked delivery to the apical membrane in elevated Cu. If the vesicular proton-pump inhibitor bafilomycin-A1 (Baf) was present with Cu, ATP7B still exited the TGN, but accumulated in large endosomes located near the coverslip, in the basolateral region. Baf washout restored ATP7B trafficking to the apical domain. If ATP7B was staged apically in high Cu, Baf addition promoted the accumulation of ATP7B in subapical endosomes, indicating a blockade of apical recycling, with concomitant loss of ATP7B at the apical membrane. The retrograde pathway to the TGN, induced by Cu removal, was far less affected by Baf than the anterograde (Cu-stimulated) case. Overall, loss of acidification-impaired Cu-regulated trafficking of ATP7B at two main sites: (i) sorting and exit from large basolateral endosomes and (ii) recycling via endosomes near the apical membrane.
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Affiliation(s)
- Lydia K Nyasae
- Department of Cell Biology, The Johns Hopkins School of Medicine, 725 N. Wolfe Street, Baltimore, MD, 20184, USA
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Gao S, Yin T, Xu B, Ma Y, Hu M. Amino acid facilitates absorption of copper in the Caco-2 cell culture model. Life Sci 2014; 109:50-6. [DOI: 10.1016/j.lfs.2014.05.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/23/2014] [Accepted: 05/30/2014] [Indexed: 10/25/2022]
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Lalioti V, Hernandez-Tiedra S, Sandoval IV. DKWSLLL, a versatile DXXXLL-type signal with distinct roles in the Cu(+)-regulated trafficking of ATP7B. Traffic 2014; 15:839-60. [PMID: 24831241 DOI: 10.1111/tra.12176] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 05/09/2014] [Accepted: 05/09/2014] [Indexed: 11/27/2022]
Abstract
In the liver, the P-type ATPase and membrane pump ATP7B plays a crucial role in Cu(+) donation to cuproenzymes and in the elimination of excess Cu(+). ATP7B is endowed with a COOH-cytoplasmic (DE)XXXLL-type traffic signal. We find that accessory (Lys -3, Trp -2, Ser -1 and Leu +2) and canonical (D -4, Leu 0 and Leu +1) residues confer the DKWSLLL signal with the versatility required for the Cu(+)-regulated cycling of ATP7B between the trans-Golgi network (TGN) and the plasma membrane (PM). The separate mutation of these residues caused a disruption of the signal, resulting in different ATP7B distribution phenotypes. These phenotypes indicate the key roles of specific residues at separate steps of ATP7B trafficking, including sorting at the TGN, transport from the TGN to the PM and its endocytosis, and recycling to the TGN and PM. The distinct roles of ATP7B in the TGN and PM and the variety of phenotypes caused by the mutation of the canonical and accessory residues of the DKWSLLL signal can explain the separate or joined presentation of Wilson's cuprotoxicosis and the dysfunction of the cuproenzymes that accept Cu(+) at the TGN.
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Affiliation(s)
- Vasiliki Lalioti
- Centro Biología Molecular Severo Ochoa, Cantoblanco, 28049, Madrid, Spain
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Distinct phenotype of a Wilson disease mutation reveals a novel trafficking determinant in the copper transporter ATP7B. Proc Natl Acad Sci U S A 2014; 111:E1364-73. [PMID: 24706876 DOI: 10.1073/pnas.1314161111] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Wilson disease (WD) is a monogenic autosomal-recessive disorder of copper accumulation that leads to liver failure and/or neurological deficits. WD is caused by mutations in ATP7B, a transporter that loads Cu(I) onto newly synthesized cupro-enzymes in the trans-Golgi network (TGN) and exports excess copper out of cells by trafficking from the TGN to the plasma membrane. To date, most WD mutations have been shown to disrupt ATP7B activity and/or stability. Using a multidisciplinary approach, including clinical analysis of patients, cell-based assays, and computational studies, we characterized a patient mutation, ATP7B(S653Y), which is stable, does not disrupt Cu(I) transport, yet renders the protein unable to exit the TGN. Bulky or charged substitutions at position 653 mimic the phenotype of the patient mutation. Molecular modeling and dynamic simulation suggest that the S653Y mutation induces local distortions within the transmembrane (TM) domain 1 and alter TM1 interaction with TM2. S653Y abolishes the trafficking-stimulating effects of a secondary mutation in the N-terminal apical targeting domain. This result indicates a role for TM1/TM2 in regulating conformations of cytosolic domains involved in ATP7B trafficking. Taken together, our experiments revealed an unexpected role for TM1/TM2 in copper-regulated trafficking of ATP7B and defined a unique class of WD mutants that are transport-competent but trafficking-defective. Understanding the precise consequences of WD-causing mutations will facilitate the development of advanced mutation-specific therapies.
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Safaei R, Adams PL, Mathews RA, Manorek G, Howell SB. The role of metal binding and phosphorylation domains in the regulation of cisplatin-induced trafficking of ATP7B. Metallomics 2014; 5:964-72. [PMID: 23803742 DOI: 10.1039/c3mt00131h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The copper (Cu) exporter ATP7B mediates cellular resistance to cisplatin (cDDP) by increasing drug efflux. ATP7B binds and sequesters cDDP in into secretory vesicles. Upon cDDP exposure ATP7B traffics from the trans-Golgi network (TGN) to the periphery of the cell in a manner that requires the cysteine residues in its metal binding domains (MBD). To elucidate the role of the various domains of ATP7B in its cDDP-induced trafficking we expressed a series of mCherry-tagged variants of ATP7B in HEK293T cells and analyzed their subcellular localization in basal media and after a 1 h exposure to 30 μM cDDP. The wild type ATP7B and a variant in which the cysteines in the CXXC motifs of MBD 1-5 were converted to serines trafficked out of the trans-Golgi (TGN) when exposed to cDDP. Conversion of the cysteines in all 6 of the CXXC motifs to serines, or in only the sixth MBD, rendered ATP7B incapable of trafficking on exposure to cDDP. Truncation of MBD1-5 or MBD1-6 resulted in the loss of TGN localization. Addition of the first 63 amino acids of ATP7B to these variants restored TGN localization to a great extent and enabled the MBD1-5 variant to undergo cDDP-induced trafficking. A variant of ATP7B in which the aspartate 1027 residue in the phosphorylation domain was converted to glutamine localized to the TGN but was incapable of cDDP-induced trafficking. These results demonstrate that the CXXC motif in the sixth MBD and the catalytic activity of ATP7B are required for cDDP-induced trafficking as they are for Cu-induced redistribution of ATP7B; this provides further evidence that cDDP mimics Cu with respect to the molecular mechanisms by they control the subcellular distribution of ATP7B.
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Affiliation(s)
- Roohangiz Safaei
- Moores Cancer Center, University of California, San Diego, 3855 Health Sciences Drive, La Jolla, CA 92093-0819, USA
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Abstract
Hepatocytes, like other epithelia, are situated at the interface between the organism's exterior and the underlying internal milieu and organize the vectorial exchange of macromolecules between these two spaces. To mediate this function, epithelial cells, including hepatocytes, are polarized with distinct luminal domains that are separated by tight junctions from lateral domains engaged in cell-cell adhesion and from basal domains that interact with the underlying extracellular matrix. Despite these universal principles, hepatocytes distinguish themselves from other nonstriated epithelia by their multipolar organization. Each hepatocyte participates in multiple, narrow lumina, the bile canaliculi, and has multiple basal surfaces that face the endothelial lining. Hepatocytes also differ in the mechanism of luminal protein trafficking from other epithelia studied. They lack polarized protein secretion to the luminal domain and target single-spanning and glycosylphosphatidylinositol-anchored bile canalicular membrane proteins via transcytosis from the basolateral domain. We compare this unique hepatic polarity phenotype with that of the more common columnar epithelial organization and review our current knowledge of the signaling mechanisms and the organization of polarized protein trafficking that govern the establishment and maintenance of hepatic polarity. The serine/threonine kinase LKB1, which is activated by the bile acid taurocholate and, in turn, activates adenosine monophosphate kinase-related kinases including AMPK1/2 and Par1 paralogues has emerged as a key determinant of hepatic polarity. We propose that the absence of a hepatocyte basal lamina and differences in cell-cell adhesion signaling that determine the positioning of tight junctions are two crucial determinants for the distinct hepatic and columnar polarity phenotypes.
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Affiliation(s)
- Aleksandr Treyer
- Albert Einstein College of Medicine, Department of Developmental and Molecular Biology, Bronx, New York, USA
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35
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Zhu M, Ni W, Dong Y, Wu ZY. EGFP tags affect cellular localization of ATP7B mutants. CNS Neurosci Ther 2013; 19:346-51. [PMID: 23607698 DOI: 10.1111/cns.12091] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/03/2013] [Accepted: 02/04/2013] [Indexed: 01/22/2023] Open
Abstract
AIMS Wilson's disease is an autosomal recessive disorder of copper metabolism due to mutations within ATP7B gene. Clinical investigations indicate that ATP7B truncations are associated with an early age of onset when compared to its missense mutations. In vitro studies show that mislocalization of ATP7B mutants is involved in disease-causing mechanisms. Enhanced green fluorescent protein (EGFP) tags are commonly used in in vitro studies of cellular localization of ATP7B mutants. However, there is still much unknown about cellular localization of ATP7B truncations. METHODS Here, we subcloned full-length human wild-type, a missense mutation (T935M), and four truncating mutants (E332X, Q511X, Q547X, Q819X) of ATP7B into pEGFP-C1, pEGFP-N2 and pCMV-myc, and transfected Chinese hamster ovary (CHO) and SH-SY5Y cells with them, respectively. RESULTS ATP7B truncations all showed a diffuse and homogenous distribution pattern within the cytosol of CHO and SH-SY5Y cells, whereas its wild-type proteins and T935M mutation were clustered in the Golgi apparatus. Furthermore, we found that EGFP tags at N- or C-terminal would severely affect cellular localization of ATP7B truncations, and EGFP tags at N-terminal also have an influence on T935M localization. CONCLUSION EGFP tags may not be suitable for the detection of cellular localization of ATP7B mutants.
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Affiliation(s)
- Min Zhu
- Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, China
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Telianidis J, Hung YH, Materia S, Fontaine SL. Role of the P-Type ATPases, ATP7A and ATP7B in brain copper homeostasis. Front Aging Neurosci 2013; 5:44. [PMID: 23986700 PMCID: PMC3750203 DOI: 10.3389/fnagi.2013.00044] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 08/05/2013] [Indexed: 12/21/2022] Open
Abstract
Over the past two decades there have been significant advances in our understanding of copper homeostasis and the pathological consequences of copper dysregulation. Cumulative evidence is revealing a complex regulatory network of proteins and pathways that maintain copper homeostasis. The recognition of copper dysregulation as a key pathological feature in prominent neurodegenerative disorders such as Alzheimer's, Parkinson's, and prion diseases has led to increased research focus on the mechanisms controlling copper homeostasis in the brain. The copper-transporting P-type ATPases (copper-ATPases), ATP7A and ATP7B, are critical components of the copper regulatory network. Our understanding of the biochemistry and cell biology of these complex proteins has grown significantly since their discovery in 1993. They are large polytopic transmembrane proteins with six copper-binding motifs within the cytoplasmic N-terminal domain, eight transmembrane domains, and highly conserved catalytic domains. These proteins catalyze ATP-dependent copper transport across cell membranes for the metallation of many essential cuproenzymes, as well as for the removal of excess cellular copper to prevent copper toxicity. A key functional aspect of these copper transporters is their copper-responsive trafficking between the trans-Golgi network and the cell periphery. ATP7A- and ATP7B-deficiency, due to genetic mutation, underlie the inherited copper transport disorders, Menkes and Wilson diseases, respectively. Their importance in maintaining brain copper homeostasis is underscored by the severe neuropathological deficits in these disorders. Herein we will review and update our current knowledge of these copper transporters in the brain and the central nervous system, their distribution and regulation, their role in normal brain copper homeostasis, and how their absence or dysfunction contributes to disturbances in copper homeostasis and neurodegeneration.
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Affiliation(s)
- Jonathon Telianidis
- Strategic Research Centre for Molecular and Medical Research, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
- Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
| | - Ya Hui Hung
- Oxidation Biology Unit, Florey Institute of Neuroscience and Mental HealthParkville, VIC, Australia
- Centre for Neuroscience Research, The University of MelbourneParkville, VIC, Australia
| | - Stephanie Materia
- Strategic Research Centre for Molecular and Medical Research, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
- Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
| | - Sharon La Fontaine
- Strategic Research Centre for Molecular and Medical Research, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
- Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin UniversityBurwood, VIC, Australia
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Polishchuk R, Lutsenko S. Golgi in copper homeostasis: a view from the membrane trafficking field. Histochem Cell Biol 2013; 140:285-95. [PMID: 23846821 DOI: 10.1007/s00418-013-1123-8] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/28/2013] [Indexed: 01/06/2023]
Abstract
Copper is essential for a variety of important biological processes as a cofactor and regulator of many enzymes. Incorporation of copper into the secreted and plasma membrane-targeted cuproenzymes takes place in Golgi, a compartment central for normal copper homeostasis. The Golgi complex harbors copper-transporting ATPases, ATP7A and ATP7B that transfer copper from the cytosol into Golgi lumen for incorporation into copper-dependent enzymes. The Golgi complex also sends these ATPases to appropriate post-Golgi destinations to ensure correct Cu fluxes in the body and to avoid potentially toxic copper accumulation. Mutations in ATP7A or ATP7B or in the proteins that regulate their trafficking affect their exit from Golgi or subsequent retrieval to this organelle. This, in turn, disrupts the homeostatic Cu balance, resulting in copper deficiency (Menkes disease) or copper overload (Wilson disease). Research over the last decade has yielded significant insights into the enzymatic properties and cell biology of the copper ATPases. However, the mechanisms through which the Golgi regulates trafficking of ATP7A/7B and, therefore, maintains Cu homeostasis remain unclear. This review summarizes current data on the role of the Golgi in Cu metabolism and outlines questions and challenges that should be addressed to understand ATP7A and ATP7B trafficking mechanisms in health and disease.
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Affiliation(s)
- Roman Polishchuk
- Telethon Institute of Genetics and Medicine TIGEM, Via Pietro Castellino, 111, 80131 Naples, Italy.
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Grosse B, Degrouard J, Jaillard D, Cassio D. Build them up and break them down: Tight junctions of cell lines expressing typical hepatocyte polarity with a varied repertoire of claudins. Tissue Barriers 2013; 1:e25210. [PMID: 24665408 PMCID: PMC3783225 DOI: 10.4161/tisb.25210] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Revised: 05/28/2013] [Accepted: 05/29/2013] [Indexed: 12/14/2022] Open
Abstract
Tight junctions (TJs) of cells expressing simple epithelial polarity have been extensively studied, but less is known about TJs of cells expressing complex polarity. In this paper we analyzed, TJs of four different lines, that form bile canaliculi (BC) and express typical hepatocyte polarity; WIF-B9, 11–3, Can 3–1, Can 10. Striking differences were observed in claudin expression. None of the cell lines produced claudin-1. WIF-B9 and 11–3 expressed only claudin-2 while Can 3–1 and Can 10 expressed claudin-2,-3,-4,-5. TJs of these two classes of lines differed in their ultra-stucture, paracellular permeability, and robustness. Lines expressing a large claudin repertoire, especially Can 10, had complex and efficient TJs, that were maintained when cells were depleted in calcium. Inversely, TJs of WIF-B9 and 11–3 were leaky, permissive and dismantled by calcium depletion. Interestingly, we found that during the polarization process, TJ proteins expressed by all lines were sequentially settled in a specific order: first occludin, ZO-1 and cingulin, then JAM-A and ZO-2, finally claudin-2. Claudins expressed only in Can lines were also sequentially settled: claudin-3 was the first settled. Inhibition of claudin-3 expression delayed BC formation in Can10 and induced the expression of simple epithelial polarity. These results highlight the role of claudins in the settlement and the efficiency of TJs in lines expressing typical hepatocyte polarity. Can 10 seems to be the most promising of these lines because of its claudin repertoire near that of hepatocytes and its capacity to form extended tubular BC sealed by efficient TJs.
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Affiliation(s)
- Brigitte Grosse
- Inserm, UMR-S 757; Orsay, France ; Université Paris-Sud; Orsay, France
| | | | | | - Doris Cassio
- Inserm, UMR-S 757; Orsay, France ; Université Paris-Sud; Orsay, France
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Gupta A, Lutsenko S. Evolution of copper transporting ATPases in eukaryotic organisms. Curr Genomics 2012; 13:124-33. [PMID: 23024604 PMCID: PMC3308323 DOI: 10.2174/138920212799860661] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 09/22/2011] [Accepted: 09/29/2011] [Indexed: 11/22/2022] Open
Abstract
Copper is an essential nutrient for most life forms, however in excess it can be harmful. The ATP-driven copper pumps (Copper-ATPases) play critical role in living organisms by maintaining appropriate copper levels in cells and tissues. These evolutionary conserved polytopic membrane proteins are present in all phyla from simplest life forms (bacteria) to highly evolved eukaryotes (Homo sapiens). The presumed early function in metal detoxification remains the main function of Copper-ATPases in prokaryotic kingdom. In eukaryotes, in addition to removing excess copper from the cell, Copper-ATPases have another equally important function - to supply copper to copper dependent enzymes within the secretory pathway. This review focuses on the origin and diversification of Copper ATPases in eukaryotic organisms. From a single Copper ATPase in protozoans, a divergence into two functionally distinct ATPases is observed with the evolutionary appearance of chordates. Among the key functional domains of Copper-ATPases, the metal-binding N-terminal domain could be responsible for functional diversification of the copper ATPases during the course of evolution.
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Affiliation(s)
- Arnab Gupta
- Department of Physiology, Johns Hopkins University, Baltimore, MD 21205, USA
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Hasan NM, Gupta A, Polishchuk E, Yu CH, Polishchuk R, Dmitriev OY, Lutsenko S. Molecular events initiating exit of a copper-transporting ATPase ATP7B from the trans-Golgi network. J Biol Chem 2012; 287:36041-50. [PMID: 22898812 DOI: 10.1074/jbc.m112.370403] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The copper-transporting ATPase ATP7B has a dual intracellular localization: the trans-Golgi network (TGN) and cytosolic vesicles. Changes in copper levels, kinase-mediated phosphorylation, and mutations associated with Wilson disease alter the steady-state distribution of ATP7B between these compartments. To identify a primary molecular event that triggers ATP7B exit from the TGN, we characterized the folding, activity, and trafficking of the ATP7B variants with mutations within the regulatory N-terminal domain (N-ATP7B). We found that structural changes disrupting the inter-domain contacts facilitate ATP7B exit from the TGN. Mutating Ser-340/341 in the N-ATP7B individually or together to Ala, Gly, Thr, or Asp produced active protein and shifted the steady-state localization of ATP7B to vesicles, independently of copper levels. The Ser340/341G mutant had a lower kinase-mediated phosphorylation under basal conditions and no copper-dependent phosphorylation. Thus, negative charges introduced by copper-dependent phosphorylation are not obligatory for ATP7B trafficking from the TGN. The Ser340/341A mutation did not alter the overall fold of N-ATP7B, but significantly decreased interactions with the nucleotide-binding domain, mimicking consequences of copper binding to N-ATP7B. We propose that structural changes that specifically alter the inter-domain contacts initiate exit of ATP7B from the TGN, whereas increased phosphorylation may be needed to maintain an open interface between the domains.
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Affiliation(s)
- Nesrin M Hasan
- Department of Physiology, Johns Hopkins University, Baltimore, Maryland 21205, USA
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Abstract
The polarized distribution of proteins and lipids at the surface membrane of epithelial cells results in the formation of an apical and a basolateral domain, which are separated by tight junctions. The generation and maintenance of epithelial polarity require elaborate mechanisms that guarantee correct sorting and vectorial delivery of cargo molecules. This dynamic process involves the interaction of sorting signals with sorting machineries and the formation of transport carriers. Here we review the recent advances in the field of polarized sorting in epithelial cells. We especially highlight the role of lipid rafts in apical sorting.
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Safaei R, Adams PL, Maktabi MH, Mathews RA, Howell SB. The CXXC motifs in the metal binding domains are required for ATP7B to mediate resistance to cisplatin. J Inorg Biochem 2012; 110:8-17. [PMID: 22459168 DOI: 10.1016/j.jinorgbio.2012.02.016] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 02/01/2012] [Accepted: 02/20/2012] [Indexed: 01/01/2023]
Abstract
The copper (Cu) exporter ATP7B mediates resistance to cisplatin (cDDP) but details of the mechanism are unknown. We explored the role of the CXXC motifs in the metal binding domains (MBDs) of ATP7B by investigating binding of cDDP to the sixth metal binding domain (MBD6) or a variant in which the CXXC motif was converted to SXXS. Platinum measurement showed that cDDP bound to wild type MBD6 but not to the SXXS variant. Wild type ATP7B rendered ovarian 2008 cells resistant to cDDP. In 2008 and in HEK293T cells, wild type ATP7B trafficked from TGN to peripheral locations in response to Cu or cDDP. A variant in which the CXXC motifs in all 6 MBDs were converted to SXXS localized correctly to the TGN but failed to traffic when exposed to either Cu or cDDP. Deletion of either the first 5 MBDs or all 6 MBDs resulted in failure to localize to the TGN. Neither the SXXS variant nor the deletion variant was able to mediate resistance to cDDP. We conclude that cDDP binds to the CXXC motifs of ATP7B and that this interaction is essential to the trafficking of ATP7B and to its ability to mediate resistance to cDDP.
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Affiliation(s)
- Roohangiz Safaei
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093-0819, USA.
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Hasan NM, Lutsenko S. Regulation of copper transporters in human cells. CURRENT TOPICS IN MEMBRANES 2012; 69:137-61. [PMID: 23046650 DOI: 10.1016/b978-0-12-394390-3.00006-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Copper is essential for normal growth and development of human organisms. The role of copper as a cofactor of important metabolic enzymes, such as cytochrome c oxidase, superoxide dismutase, lysyl oxidase, dopamine-β-hydroxylase, and many others, has been well established. In recent years, new regulatory roles of copper have emerged. Accumulating evidence points to the involvement of copper in lipid metabolism, antimicrobial defense, neuronal activity, resistance of tumor cells to platinum-based chemotherapeutic drugs, kinase-mediated signal transduction, and other essential cellular processes. For many of these processes, the precise mechanism of copper action remains to be established. Nevertheless, it is increasingly clear that many regulatory and signaling events are associated with changes in the intracellular localization and abundance of copper transporters, as well as distinct compartmentalization of copper itself. In this review, we discuss current data on regulation of the localization and abundance of copper transporters in response to metabolic and signaling events in human cells. Regulation by kinase-mediated phosphorylation will be addressed along with the emerging area of the redox-driven control of copper transport. We highlight mechanistic questions that await further testing.
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Affiliation(s)
- Nesrin M Hasan
- Department of Physiology, Johns Hopkins University, Baltimore, MD, USA
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Braiterman L, Nyasae L, Leves F, Hubbard AL. Critical roles for the COOH terminus of the Cu-ATPase ATP7B in protein stability, trans-Golgi network retention, copper sensing, and retrograde trafficking. Am J Physiol Gastrointest Liver Physiol 2011; 301:G69-81. [PMID: 21454443 PMCID: PMC3129927 DOI: 10.1152/ajpgi.00038.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
ATP7A and ATP7B are copper-transporting P-type ATPases that are essential to eukaryotic copper homeostasis and must traffic between intracellular compartments to carry out their functions. Previously, we identified a nine-amino acid sequence (F37-E45) in the NH(2) terminus of ATP7B that is required to retain the protein in the Golgi when copper levels are low and target it apically in polarized hepatic cells when copper levels rise. To understand further the mechanisms regulating the intracellular dynamics of ATP7B, using multiple functional assays, we characterized the protein phenotypes of 10 engineered and Wilson disease-associated mutations in the ATP7B COOH terminus in polarized hepatic cells and fibroblasts. We also examined the behavior of a chimera between ATP7B and ATP7A. Our results clearly demonstrate the importance of the COOH terminus of ATP7B in the protein's copper-responsive apical trafficking. L1373 at the end of transmembrane domain 8 is required for protein stability and Golgi retention in low copper, the trileucine motif (L1454-L1456) is required for retrograde trafficking, and the COOH terminus of ATP7B exhibits a higher sensitivity to copper than does ATP7A. Importantly, our results demonstrating that four Wilson disease-associated missense mutations behaved in a wild-type manner in all our assays, together with current information in the literature, raise the possibility that several may not be disease-causing mutations.
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Affiliation(s)
- L. Braiterman
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - L. Nyasae
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - F. Leves
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - A. L. Hubbard
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland
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Jimenez-Movilla M, Dean J. ZP2 and ZP3 cytoplasmic tails prevent premature interactions and ensure incorporation into the zona pellucida. J Cell Sci 2011; 124:940-50. [PMID: 21378311 DOI: 10.1242/jcs.079988] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The zona pellucida contains three proteins (ZP1, ZP2, ZP3), the precursors of which possess signal peptides, 'zona' domains and short (9-15 residue) cytoplasmic tails downstream of a transmembrane domain. The ectodomains of ZP2 and ZP3 are sufficient to form the insoluble zona matrix and yet each protein traffics through oocytes without oligomerization. ZP2 and ZP3 were fluorescently tagged and molecular interactions were assayed by fluorescent complementation in CHO cells and growing oocytes. ZP2 and ZP3 traffic independently, but colocalize at the plasma membrane. However, protein-protein interactions were observed only after release and incorporation of ZP2 and ZP3 into the extracellular matrix surrounding mouse oocytes. In the absence of their hydrophilic cytoplasmic tails, ZP2 and ZP3 interacted within the cell and did not participate in the zona pellucida. A heterologous GPI-anchored 'zona' domain protein fused with the cytoplasmic tails was integrated into the zona matrix. We conclude that the cytoplasmic tails are sufficient and necessary to prevent intracellular oligomerization while ensuring incorporation of processed ZP2 and ZP3 into the zona pellucida.
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Affiliation(s)
- Maria Jimenez-Movilla
- Laboratory of Cellular and Developmental Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA
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Chotani MA, Flavahan NA. Intracellular α(2C)-adrenoceptors: storage depot, stunted development or signaling domain? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1495-503. [PMID: 21605601 DOI: 10.1016/j.bbamcr.2011.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 05/03/2011] [Accepted: 05/06/2011] [Indexed: 12/11/2022]
Abstract
G-protein coupled receptors (GPCRs) are generally considered to function as cell surface signaling structures that respond to extracellular mediators, many of which do not readily access the cell's interior. Indeed, most GPCRs are preferentially targeted to the plasma membrane. However, some receptors, including α(2C)-Adrenoceptors, challenge conventional concepts of GPCR activity by being preferentially retained and localized within intracellular organelles. This review will address the issues associated with this unusual GPCR localization and discuss whether it represents a novel sub-cellular niche for GPCR signaling, whether these receptors are being stored for rapid deployment to the cell surface, or whether they represent immature or incomplete receptor systems.
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Affiliation(s)
- Maqsood A Chotani
- Center for Cardiovascular and Pulmonary Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH 43205, USA
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Cellular copper levels determine the phenotype of the Arg875 variant of ATP7B/Wilson disease protein. Proc Natl Acad Sci U S A 2011; 108:5390-5. [PMID: 21406592 DOI: 10.1073/pnas.1014959108] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
In human disorders, the genotype-phenotype relationships are often complex and influenced by genetic and/or environmental factors. Wilson disease (WD) is a monogenic disorder caused by mutations in the copper-transporting P-type ATPase ATP7B. WD shows significant phenotypic diversity even in patients carrying identical mutations; the basis for such diverse manifestations is unknown. We demonstrate that the 2623A/G polymorphism (producing the Gly(875) → Arg substitution in the A-domain of ATP7B) drastically alters the intracellular properties of ATP7B, whereas copper reverses the effects. Under basal conditions, the common Gly(875) variant of ATP7B is targeted to the trans-Golgi network (TGN) and transports copper into the TGN lumen. In contrast, the Arg(875) variant is located in the endoplasmic reticulum (ER) and does not deliver copper to the TGN. Elevated copper corrects the ATP7B-Arg(875) phenotype. Addition of only 0.5-5 μM copper triggers the exit of ATP7B-Arg(875) from the ER and restores copper delivery to the TGN. Analysis of the recombinant A-domains by NMR suggests that the ER retention of ATP7B-Arg(875) is attributable to increased unfolding of the Arg(875)-containing A-domain. Copper is not required for the folding of ATP7B-Arg(875) during biosynthesis, but it stabilizes protein and stimulates its activity. A chemotherapeutical drug, cisplatin, that mimics a copper-bound state of ATP7B also corrects the "disease-like" phenotype of ATP7B-Arg(875) and promotes its TGN targeting and transport function. We conclude that in populations harboring the Arg(875) polymorphism, the levels of bioavailable copper may play a vital role in the manifestations of WD.
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Wang Y, Hodgkinson V, Zhu S, Weisman GA, Petris MJ. Advances in the understanding of mammalian copper transporters. Adv Nutr 2011; 2:129-37. [PMID: 22332042 PMCID: PMC3065767 DOI: 10.3945/an.110.000273] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Copper (Cu) is an essential micronutrient. Its ability to exist in 2 oxidation states (Cu(1+) and Cu(2+)) allows it to function as an enzymatic cofactor in hydrolytic, electron transfer, and oxygen utilization reactions. Cu transporters CTR1, ATP7A, and ATP7B play key roles in ensuring that adequate Cu is available for Cu-requiring processes and the prevention of excess Cu accumulation within cells. Two diseases of Cu metabolism, Menkes disease and Wilson disease, which are caused by mutations in ATP7A and ATP7B, respectively, exemplify the critical importance of regulating Cu balance in humans. Herein, we review recent studies of the biochemical and cell biological characteristics of CTR1, ATP7A, and ATP7B, as well as emerging roles for Cu in new areas of physiology.
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Affiliation(s)
- Yanfang Wang
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Victoria Hodgkinson
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Sha Zhu
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Gary A. Weisman
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211
| | - Michael J. Petris
- Department of Biochemistry, University of Missouri, Columbia, MO 65211,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO 65211,Christopher S. Bond Life Science Center, University of Missouri, Columbia, MO 65211,To whom correspondence should be addressed. E-mail:
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In silico modeling of the Menkes copper-translocating P-type ATPase 3rd metal binding domain predicts that phosphorylation regulates copper-binding. Biometals 2011; 24:477-87. [DOI: 10.1007/s10534-011-9410-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 01/06/2011] [Indexed: 12/17/2022]
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