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Fortino M, Arnesano F, Pietropaolo A. Unraveling Copper Exchange in the Atox1-Cu(I)-Mnk1 Heterodimer: A Simulation Approach. J Phys Chem B 2024. [PMID: 38780400 DOI: 10.1021/acs.jpcb.4c01026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Copper, an essential metal for various cellular processes, requires tight regulation to prevent cytotoxicity. Intracellular pathways crucial for maintaining optimal copper levels involve soluble and membrane transporters, namely, metallochaperones and P-type ATPases, respectively. In this study, we used a simulation workflow based on free-energy perturbation (FEP) theory and parallel bias metadynamics (PBMetaD) to predict the Cu(I) exchange mechanism between the human Cu(I) chaperone, Atox1, and one of its two physiological partners, ATP7A. ATP7A, also known as the Menkes disease protein, is a transmembrane protein and one of the main copper-transporting ATPases. It pumps copper into the trans-Golgi network for the maturation of cuproenzymes and is also essential for the efflux of excess copper across the plasma membrane. In this analysis, we utilized the nuclear magnetic resonance (NMR) structure of the Cu(I)-mediated complex between Atox1 and the first soluble domain of the Menkes protein (Mnk1) as a starting point. Independent free-energy simulations were conducted to investigate the dissociation of both Atox1 and Mnk1. The calculations revealed that the two dissociations require free energy values of 6.3 and 6.2 kcal/mol, respectively, following a stepwise dissociation mechanism.
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Affiliation(s)
- Mariagrazia Fortino
- Dipartimento di Scienze della Salute, Università Magna Graecia di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
| | - Fabio Arnesano
- Dipartimento di Chimica, Università di Bari "Aldo Moro", Via Orabona 4, 70125 Bari, Italy
| | - Adriana Pietropaolo
- Dipartimento di Scienze della Salute, Università Magna Graecia di Catanzaro, Viale Europa, 88100 Catanzaro, Italy
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2
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Zhou Y, Zhang L. The interplay between copper metabolism and microbes: in perspective of host copper-dependent ATPases ATP7A/B. Front Cell Infect Microbiol 2023; 13:1267931. [PMID: 38106478 PMCID: PMC10723777 DOI: 10.3389/fcimb.2023.1267931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 11/13/2023] [Indexed: 12/19/2023] Open
Abstract
Copper, a vital element in various physiological processes, is transported from the gastrointestinal tract to tissues and cells through diverse copper transporters. Among these transporters, ATP7A and ATP7B play significant roles in regulating systemic copper metabolism and exhibit precise regulation in their intracellular trafficking. These transporters undergo dynamic shuttling between the trans-Golgi network (TGN) and the plasma membrane via the endocytic recycling mechanism, which involves the retromer and other associated factors. Interestingly, the antimicrobial attribute of copper implies a potential connection between microbial infection and copper metabolism. Several microbes, including Salmonella enterica, Cryptococcus, Influenza A virus (IAV) and Zika virus (ZIKV) have been observed to impact the regulatory mechanisms of ATP7A/B, either directly or indirectly, as a means of survival. This review summarizes the key features and trafficking mechanisms of the copper transporters ATP7A/B, and examines the intricate interplay between microbes and copper metabolism. Ultimately, it highlights how microbes can perturb copper homeostasis through interactions with host factors, offering valuable insights into the mechanistic aspects of host-microbe interactions.
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Affiliation(s)
- Yixuan Zhou
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- Department of Pathogen Biology, School of Clinical and Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
| | - Leiliang Zhang
- Department of Clinical Laboratory Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- Department of Pathogen Biology, School of Clinical and Basic Medical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, China
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3
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Wen MH, Xie X, Huang PS, Yang K, Chen TY. Crossroads between membrane trafficking machinery and copper homeostasis in the nerve system. Open Biol 2021; 11:210128. [PMID: 34847776 PMCID: PMC8633785 DOI: 10.1098/rsob.210128] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Imbalanced copper homeostasis and perturbation of membrane trafficking are two common symptoms that have been associated with the pathogenesis of neurodegenerative and neurodevelopmental diseases. Accumulating evidence from biophysical, cellular and in vivo studies suggest that membrane trafficking orchestrates both copper homeostasis and neural functions-however, a systematic review of how copper homeostasis and membrane trafficking interplays in neurons remains lacking. Here, we summarize current knowledge of the general trafficking itineraries for copper transporters and highlight several critical membrane trafficking regulators in maintaining copper homeostasis. We discuss how membrane trafficking regulators may alter copper transporter distribution in different membrane compartments to regulate intracellular copper homeostasis. Using Parkinson's disease and MEDNIK as examples, we further elaborate how misregulated trafficking regulators may interplay parallelly or synergistically with copper dyshomeostasis in devastating pathogenesis in neurodegenerative diseases. Finally, we explore multiple unsolved questions and highlight the existing challenges to understand how copper homeostasis is modulated through membrane trafficking.
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Affiliation(s)
- Meng-Hsuan Wen
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Xihong Xie
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Pei-San Huang
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
| | - Karen Yang
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Tai-Yen Chen
- Department of Chemistry, University of Houston, Houston, TX 77204, USA
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4
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Logeman BL, Wood LK, Lee J, Thiele DJ. Gene duplication and neo-functionalization in the evolutionary and functional divergence of the metazoan copper transporters Ctr1 and Ctr2. J Biol Chem 2017; 292:11531-11546. [PMID: 28507097 DOI: 10.1074/jbc.m117.793356] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 05/12/2017] [Indexed: 11/06/2022] Open
Abstract
Copper is an essential element for proper organismal development and is involved in a range of processes, including oxidative phosphorylation, neuropeptide biogenesis, and connective tissue maturation. The copper transporter (Ctr) family of integral membrane proteins is ubiquitously found in eukaryotes and mediates the high-affinity transport of Cu+ across both the plasma membrane and endomembranes. Although mammalian Ctr1 functions as a Cu+ transporter for Cu acquisition and is essential for embryonic development, a homologous protein, Ctr2, has been proposed to function as a low-affinity Cu transporter, a lysosomal Cu exporter, or a regulator of Ctr1 activity, but its functional and evolutionary relationship to Ctr1 is unclear. Here we report a biochemical, genetic, and phylogenetic comparison of metazoan Ctr1 and Ctr2, suggesting that Ctr2 arose over 550 million years ago as a result of a gene duplication event followed by loss of Cu+ transport activity. Using a random mutagenesis and growth selection approach, we identified amino acid substitutions in human and mouse Ctr2 proteins that support copper-dependent growth in yeast and enhance copper accumulation in Ctr1-/- mouse embryonic fibroblasts. These mutations revert Ctr2 to a more ancestral Ctr1-like state while maintaining endogenous functions, such as stimulating Ctr1 cleavage. We suggest key structural aspects of metazoan Ctr1 and Ctr2 that discriminate between their biological roles, providing mechanistic insights into the evolutionary, biochemical, and functional relationships between these two related proteins.
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Affiliation(s)
| | - L Kent Wood
- Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710 and
| | - Jaekwon Lee
- the Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588
| | - Dennis J Thiele
- From the Departments of Pharmacology and Cancer Biology, .,Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710 and.,Biochemistry, and
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5
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Zlatic S, Comstra HS, Gokhale A, Petris MJ, Faundez V. Molecular basis of neurodegeneration and neurodevelopmental defects in Menkes disease. Neurobiol Dis 2015; 81:154-61. [PMID: 25583185 DOI: 10.1016/j.nbd.2014.12.024] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/04/2014] [Accepted: 12/23/2014] [Indexed: 12/16/2022] Open
Abstract
ATP7A mutations impair copper metabolism resulting in three distinct genetic disorders in humans. These diseases are characterized by neurological phenotypes ranging from intellectual disability to neurodegeneration. Severe ATP7A loss-of-function alleles trigger Menkes disease, a copper deficiency condition where systemic and neurodegenerative phenotypes dominate clinical outcomes. The pathogenesis of these manifestations has been attributed to the hypoactivity of a limited number of copper-dependent enzymes, a hypothesis that we refer as the oligoenzymatic pathogenic hypothesis. This hypothesis, which has dominated the field for 25 years, only explains some systemic Menkes phenotypes. However, we argue that this hypothesis does not fully account for the Menkes neurodegeneration or neurodevelopmental phenotypes. Here, we propose revisions of the oligoenzymatic hypothesis that could illuminate the pathogenesis of Menkes neurodegeneration and neurodevelopmental defects through unsuspected overlap with other neurological conditions including Parkinson's, intellectual disability, and schizophrenia.
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Affiliation(s)
- Stephanie Zlatic
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | | | - Avanti Gokhale
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Michael J Petris
- Department of Biochemistry, University of Missouri, Columbia, MO 65211, USA
| | - Victor Faundez
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; Center for Social Translational Neuroscience, Emory University, Atlanta, GA 30322, USA.
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6
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Yi L, Kaler SG. Direct interactions of adaptor protein complexes 1 and 2 with the copper transporter ATP7A mediate its anterograde and retrograde trafficking. Hum Mol Genet 2015; 24:2411-25. [PMID: 25574028 DOI: 10.1093/hmg/ddv002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 01/05/2015] [Indexed: 11/12/2022] Open
Abstract
ATP7A is a P-type ATPase in which diverse mutations lead to X-linked recessive Menkes disease or occipital horn syndrome. Recently, two previously unknown ATP7A missense mutations, T994I and P1386S, were shown to cause an isolated distal motor neuropathy without clinical or biochemical features of other ATP7A disorders. These mutant alleles cause subtle defects in ATP7A intracellular trafficking, resulting in preferential plasma membrane localization compared with wild-type ATP7A. We reported previously that ATP7A(P1386S) causes unstable insertion of the eighth and final transmembrane segment, preventing proper position of the carboxyl-terminal tail in a proportion of mutant molecules. Here, we utilize this and other naturally occurring and engineered mutant ATP7A alleles to identify mechanisms of normal ATP7A trafficking. We show that adaptor protein (AP) complexes 1 and 2 physically interact with ATP7A and that binding is mediated in part by a carboxyl-terminal di-leucine motif. In contrast to other ATP7A missense mutations, ATP7A(P1386S) partially disturbs interactions with both APs, leading to abnormal axonal localization in transfected NSC-34 motor neurons and altered calcium-signaling following glutamate stimulation. Our results imply that AP-1 normally tethers ATP7A at the trans-Golgi network in the somatodendritic segments of motor neurons and that alterations affecting the ATP7A carboxyl-terminal tail induce release of the copper transporter to the axons or axonal membranes. The latter effects are intensified by diminished interaction with AP-2, impeding ATP7A retrograde trafficking. Taken together, these findings further illuminate the normal molecular mechanisms of ATP7A trafficking and suggest a pathophysiological basis for ATP7A-related distal motor neuropathy.
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Affiliation(s)
- Ling Yi
- Section on Translational Neuroscience, Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3754, USA
| | - Stephen G Kaler
- Section on Translational Neuroscience, Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3754, USA
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7
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Yi L, Kaler S. ATP7A trafficking and mechanisms underlying the distal motor neuropathy induced by mutations in ATP7A. Ann N Y Acad Sci 2014; 1314:49-54. [PMID: 24754450 DOI: 10.1111/nyas.12427] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Diverse mutations in the gene encoding the copper transporter ATP7A lead to X-linked recessive Menkes disease or occipital horn syndrome. Recently, two unique ATP7A missense mutations, T994I and P1386S, were shown to cause isolated adult-onset distal motor neuropathy. These mutations induce subtle defects in ATP7A intracellular trafficking resulting in preferential accumulation at the plasma membrane compared to wild-type ATP7A. Immunoprecipitation assays revealed abnormal interaction between ATP7A(T994I) and p97/VCP, a protein mutated in two autosomal dominant forms of motor neuron disease. Small-interfering RNA knockdown of valosin-containing protein corrected ATP7A(T994I) mislocalization. For ATP7A(P1386S) , flow cytometry documented that nonpermeabilized fibroblasts bound a C-terminal ATP7A antibody, suggesting unstable insertion of the eighth transmembrane segment due to a helix-breaker effect of the amino acid substitution. This could sabotage interaction of ATP7A(P1386S) with adaptor protein complexes. These molecular events appear to selectively disturb normal motor neuron function and lead to neurologic illness that takes years and sometimes decades to develop.
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Affiliation(s)
- Ling Yi
- Section on Translational Neuroscience, Molecular Medicine Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
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8
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The multi-layered regulation of copper translocating P-type ATPases. Biometals 2009; 22:177-90. [PMID: 19130269 DOI: 10.1007/s10534-008-9183-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Accepted: 12/07/2008] [Indexed: 12/21/2022]
Abstract
The copper-translocating Menkes (ATP7A, MNK protein) and Wilson (ATP7B, WND protein) P-type ATPases are pivotal for copper (Cu) homeostasis, functioning in the biosynthetic incorporation of Cu into copper-dependent enzymes of the secretory pathway, Cu detoxification via Cu efflux, and specialized roles such as systemic Cu absorption (MNK) and Cu excretion (WND). Essential to these functions is their Cu and hormone-responsive distribution between the trans-Golgi network (TGN) and exocytic vesicles located at or proximal to the apical (WND) or basolateral (MNK) cell surface. Intriguingly, MNK and WND Cu-ATPases expressed in the same tissues perform distinct yet complementary roles. While intramolecular differences may specify their distinct roles, cellular signaling components are predicted to be critical for both differences and synergy between these enzymes. This review focuses on these mechanisms, including the cell signaling pathways that influence trafficking and bi-functionality of Cu-ATPases. Phosphorylation events are hypothesized to play a central role in Cu homeostasis, promoting multi-layered regulation and cross-talk between cuproenzymes and Cu-independent mechanisms.
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9
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Lönnerdal B. Intestinal regulation of copper homeostasis: a developmental perspective. Am J Clin Nutr 2008; 88:846S-50S. [PMID: 18779306 DOI: 10.1093/ajcn/88.3.846s] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Stable-isotope studies in human infants and adults have shown that copper homeostasis occurs, but the contribution of the small intestine to this regulation is still not well understood. Copper first needs to be reduced to the cuprous form, most likely by Steap proteins on the apical membrane. Copper is subsequently absorbed by Ctr1 and then transferred in the enterocyte by the chaperone Atox1 to reach ATP7A for export from the cell. The role of ATP7B, shown to be present in the small intestine, is still poorly understood. In situations of high copper exposure, Ctr1 is endocytosed, metallothionein is induced, and ATP7A moves to a more basolateral localization. However, the ontogeny of regulation of copper homeostasis has received little attention. In rat pups, tissue copper and total-body (67)Cu retention decrease throughout postnatal development, whereas liver (67)Cu retention, serum copper, and ceruloplasmin activity increase. Total (67)Cu absorption decreases and intestinal (67)Cu retention increases with increased copper intake. During early infancy (day 10), copper supplementation increases intestinal copper and metallothionein gene expression, and Ctr1 protein levels increase, whereas Atp7A and Atp7B are unaffected. However, during late infancy (day 20), intestinal copper concentrations are unaffected by supplementation, but Ctr1, ATP7A, and Atp7B protein levels are higher than in controls. Thus, maturation of small intestine copper transport occurs through increased abundance and altered localization of Ctr1, Atp7A, and Atp7B. The mechanisms behind this maturation, including both transcriptional and posttranscriptional regulation, require further studies.
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Affiliation(s)
- Bo Lönnerdal
- Department of Nutrition, University of California, Davis, CA 95616, USA.
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10
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Delunardo F, Margutti P, Pontecorvo S, Colasanti T, Conti F, Riganò R, Profumo E, Siracusano A, Capozzi A, Prencipe M, Sorice M, Francia A, Ortona E. Screening of a microvascular endothelial cDNA library identifies rabaptin 5 as a novel autoantigen in Alzheimer's disease. J Neuroimmunol 2007; 192:105-12. [DOI: 10.1016/j.jneuroim.2007.09.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Revised: 09/17/2007] [Accepted: 09/17/2007] [Indexed: 10/22/2022]
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11
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Lutsenko S, Barnes NL, Bartee MY, Dmitriev OY. Function and regulation of human copper-transporting ATPases. Physiol Rev 2007; 87:1011-46. [PMID: 17615395 DOI: 10.1152/physrev.00004.2006] [Citation(s) in RCA: 536] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Copper-transporting ATPases (Cu-ATPases) ATP7A and ATP7B are evolutionarily conserved polytopic membrane proteins with essential roles in human physiology. The Cu-ATPases are expressed in most tissues, and their transport activity is crucial for central nervous system development, liver function, connective tissue formation, and many other physiological processes. The loss of ATP7A or ATP7B function is associated with severe metabolic disorders, Menkes disease, and Wilson disease. In cells, the Cu-ATPases maintain intracellular copper concentration by transporting copper from the cytosol across cellular membranes. They also contribute to protein biosynthesis by delivering copper into the lumen of the secretory pathway where metal ion is incorporated into copper-dependent enzymes. The biosynthetic and homeostatic functions of Cu-ATPases are performed in different cell compartments; targeting to these compartments and the functional activity of Cu-ATPase are both regulated by copper. In recent years, significant progress has been made in understanding the structure, function, and regulation of these essential transporters. These studies raised many new questions related to specific physiological roles of Cu-ATPases in various tissues and complex mechanisms that control the Cu-ATPase function. This review summarizes current data on the structural organization and functional properties of ATP7A and ATP7B as well as their localization and functions in various tissues, and discusses the current models of regulated trafficking of human Cu-ATPases.
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Affiliation(s)
- Svetlana Lutsenko
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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12
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La Fontaine S, Mercer JFB. Trafficking of the copper-ATPases, ATP7A and ATP7B: Role in copper homeostasis. Arch Biochem Biophys 2007; 463:149-67. [PMID: 17531189 DOI: 10.1016/j.abb.2007.04.021] [Citation(s) in RCA: 292] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 04/18/2007] [Accepted: 04/18/2007] [Indexed: 01/05/2023]
Abstract
Copper is essential for human health and copper imbalance is a key factor in the aetiology and pathology of several neurodegenerative diseases. The copper-transporting P-type ATPases, ATP7A and ATP7B are key molecules required for the regulation and maintenance of mammalian copper homeostasis. Their absence or malfunction leads to the genetically inherited disorders, Menkes and Wilson diseases, respectively. These proteins have a dual role in cells, namely to provide copper to essential cuproenzymes and to mediate the excretion of excess intracellular copper. A unique feature of ATP7A and ATP7B that is integral to these functions is their ability to sense and respond to intracellular copper levels, the latter manifested through their copper-regulated trafficking from the transGolgi network to the appropriate cellular membrane domain (basolateral or apical, respectively) to eliminate excess copper from the cell. Research over the last decade has yielded significant insight into the enzymatic properties and cell biology of the copper-ATPases. With recent advances in elucidating their localization and trafficking in human and animal tissues in response to physiological stimuli, we are progressing rapidly towards an integrated understanding of their physiological significance at the level of the whole animal. This knowledge in turn is helping to clarify the biochemical and cellular basis not only for the phenotypes conferred by individual Menkes and Wilson disease patient mutations, but also for the clinical variability of phenotypes associated with each of these diseases. Importantly, this information is also providing a rational basis for the applicability and appropriateness of certain diagnostic markers and therapeutic regimes. This overview will provide an update on the current state of our understanding of the localization and trafficking properties of the copper-ATPases in cells and tissues, the molecular signals and posttranslational interactions that govern their trafficking activities, and the cellular basis for the clinical phenotypes associated with disease-causing mutations.
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Affiliation(s)
- Sharon La Fontaine
- Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, 221 Burwood Highway, Burwood, Vic. 3125, Australia.
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13
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Nyasae L, Bustos R, Braiterman L, Eipper B, Hubbard A. Dynamics of endogenous ATP7A (Menkes protein) in intestinal epithelial cells: copper-dependent redistribution between two intracellular sites. Am J Physiol Gastrointest Liver Physiol 2007; 292:G1181-94. [PMID: 17158254 DOI: 10.1152/ajpgi.00472.2006] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We report for the first time on the copper-dependent behavior of endogenous ATP7A in two types of polarized intestinal epithelia, rat enterocytes in vivo and filter-grown Caco-2 cells, an accepted in vitro model of human small intestine. We used high-resolution, confocal immunofluorescence combined with quantitative cell surface biotinylation and found that the vast majority of endogenous ATP7A was localized intracellularly under all copper conditions. In copper-depleted cells, virtually all of the ATP7A localized to a post-TGN compartment, with <3% of the total protein detectable at the basolateral cell surface. When copper levels were elevated, ATP7A dispersed to the cell periphery in punctae whose pattern did not overlap with the steady-state distributions of post-Golgi, endosomal, or basolateral membrane markers; only approximately 8-10% of the recovered ATP7A was detected at the basolateral cell surface. These results raise several questions regarding prevailing models of ATP7A dynamics and the mechanism of copper efflux.
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Affiliation(s)
- L Nyasae
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21210, USA
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14
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Murgia C, Vespignani I, Rami R, Perozzi G. The Znt4 mutation inlethal milk mice affects intestinal zinc homeostasis through the expression of other Zn transporters. GENES & NUTRITION 2006; 1:61-70. [PMID: 18850221 PMCID: PMC3454819 DOI: 10.1007/bf02829937] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 03/30/2006] [Indexed: 10/22/2022]
Abstract
The lethal milk mouse syndrome is caused by a point mutation in the zinc transporter gene ZnT4 resulting in defective zinc secretion in the milk of homozygous mutant dams. Pups of any genotype fed solely on lm milk die within the first two weeks of neonatal life, displaying zinc deficiency symptoms. Homozygous mutant pups survive when foster nursed by wild type dams and show signs of mild zinc deficiency in adulthood. To further investigate the role of ZnT4 in zinc secretion in the intestinal epithelium, we have studied the expression by real time quantitative PCR of mutant ZnT4 and of other zinc transporters of the Zip and ZnT families, in the jejunum of homozygous lm mice and of the isogenic wild type strain C57BL/ 6J. We report in this paper that expression of the mutant ZnT4 mRNA, carrying a premature translational termination codon (ZnT4/lm), is almost absent in tissues from lm mice, probably as a result of degradation by the Nonsense Mediated mRNA Decay (NMD) Pathway. In the jejunum of mutant mice, we also observed decreased expression of the uptake zinc transporter Zip4, paralleled by increased levels of both metallothionein genes MTI and MTII. Zinc supplementation of lm mice in the drinking water did not result in further decrease of Zip4 expression, but led to full induction of MT mRNAs. These results lead us to conclude that, although in the enterocytes of lm mice the absence of the zinc secretion activity mediated by ZnT4 results in increased intracellular zinc concentration, other zinc efflux activities are able to maintain the level of zinc ions below the threshold necessary for full induction of metallothioneins.
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Affiliation(s)
- Chiara Murgia
- INRAN, National Research Institute on Food and Nutrition, via Ardeatina 546, 00178 Roma, Italy
| | - Isabella Vespignani
- INRAN, National Research Institute on Food and Nutrition, via Ardeatina 546, 00178 Roma, Italy
| | - Rita Rami
- INRAN, National Research Institute on Food and Nutrition, via Ardeatina 546, 00178 Roma, Italy
| | - Giuditta Perozzi
- INRAN, National Research Institute on Food and Nutrition, via Ardeatina 546, 00178 Roma, Italy
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15
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Monty JF, Llanos RM, Mercer JFB, Kramer DR. Copper exposure induces trafficking of the menkes protein in intestinal epithelium of ATP7A transgenic mice. J Nutr 2005; 135:2762-6. [PMID: 16317117 DOI: 10.1093/jn/135.12.2762] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The final steps in the absorption and excretion of copper at the molecular level are accomplished by 2 closely related proteins that catalyze the ATP-dependent transport of copper across the plasma membrane. These proteins, ATP7A and ATP7B, are encoded by the genes affected in human genetic copper-transport disorders, namely, Menkes and Wilson diseases. We studied the effect of copper perfusion of an isolated segment of the jejunum of ATP7A transgenic mice on the intracellular distribution of ATP7A by immunofluorescence of frozen sections. Our results indicate that ATP7A is retained in the trans-Golgi network under copper-limiting conditions, but relocalized to a vesicular compartment adjacent to the basolateral membrane in intestines perfused with copper. The findings support the hypothesis that the basolateral transport of copper from the enterocyte into the portal blood may involve ATP7A pumping copper into a vesicular compartment followed by exocytosis to release the copper, rather than direct pumping of copper across the basolateral membrane.
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Affiliation(s)
- Jean-François Monty
- Center for Cellular and Molecular Biology, School of Biological and Chemical Sciences, Deakin University, Burwood, Victoria, Australia
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16
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Guo Y, Nyasae L, Braiterman LT, Hubbard AL. NH2-terminal signals in ATP7B Cu-ATPase mediate its Cu-dependent anterograde traffic in polarized hepatic cells. Am J Physiol Gastrointest Liver Physiol 2005; 289:G904-16. [PMID: 15994426 DOI: 10.1152/ajpgi.00262.2005] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cu is an essential cofactor of cellular proteins but is toxic in its free state. The hepatic Cu-ATPase ATP7B has two functions in Cu homeostasis: it loads Cu+ onto newly synthesized apoceruloplasmin in the secretory pathway, thereby activating the plasma protein; and it participates in the excretion of excess Cu+ into the bile. To carry out these two functions, the membrane protein responds to changes in intracellular Cu levels by cycling between the Golgi and apical region. We used polarized hepatic WIF-B cells and high-resolution confocal microscopy to map the itinerary of endogenous and exogenous ATP7B under different Cu conditions. In Cu-depleted cells, ATP7B resided in a post-trans-Golgi network compartment that also contained syntaxin 6, whereas in Cu-loaded cells, the protein relocated to unique vesicles very near to the apical plasma membrane as well as the membrane itself. To determine the role of ATP7B's cytoplasmic NH2 terminus in regulating its intracellular movements, we generated seven mutations/deletions in this large [approximately 650 amino acid (AA)] domain and analyzed the Cu-dependent behavior of the mutant ATP7B proteins in WIF-B cells. Truncation of the ATP7B NH2 terminus up to the fifth copper-binding domain (CBD5) yielded an active ATPase that was insensitive to cellular Cu levels and constitutively trafficked to the opposite (basolateral) plasma membrane domain. Fusion of the NH2-terminal 63 AA of ATP7B to the truncated protein restored both its Cu responsiveness and correct intracellular targeting. These results indicate that important targeting information is contained in this relatively short sequence, which is absent from the related CuATPase, ATP7A.
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Affiliation(s)
- Y Guo
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Safaei R, Howell SB. Copper transporters regulate the cellular pharmacology and sensitivity to Pt drugs. Crit Rev Oncol Hematol 2005; 53:13-23. [PMID: 15607932 DOI: 10.1016/j.critrevonc.2004.09.007] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2004] [Indexed: 11/19/2022] Open
Abstract
Recent studies have demonstrated that the major Cu influx transporter CTR1 regulates tumor cell uptake of cisplatin (DDP), carboplatin (CBDCA) and oxaliplatin (L-OHP), and that the two Cu efflux transporters ATP7A and ATP7B regulate the efflux of these drugs. Evidence for the concept that these platinum (Pt) drugs enter cells and are distributed to various subcellular compartments via transporters that have evolved to manage Cu homeostasis includes the demonstration of: (1) bidirectional cross-resistance between cells selected for resistance to either the Pt drugs or Cu; (2) parallel changes in the transport of Pt and Cu drugs in resistant cells; (3) altered cytotoxic sensitivity and Pt drug accumulation in cells transfected with Cu transporters; and (4) altered expression of Cu transporters in Pt drug-resistant tumors. Appreciation of the role of the Cu transporters in the development of resistance to DDP, CBDCA, and L-OHP offers novel insights into strategies for preventing or reversing resistance to this very important family of anticancer drugs.
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Affiliation(s)
- Roohangiz Safaei
- Department of Medicine and the Rebecca and John Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093-0058, USA.
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Safaei R, Holzer AK, Katano K, Samimi G, Howell SB. The role of copper transporters in the development of resistance to Pt drugs. J Inorg Biochem 2004; 98:1607-13. [PMID: 15458823 DOI: 10.1016/j.jinorgbio.2004.05.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2004] [Revised: 05/12/2004] [Accepted: 05/12/2004] [Indexed: 12/30/2022]
Abstract
Recent studies in yeast, mouse and human cells suggest that the conserved metal binding transporters of the Cu homeostasis pathway can mediate resistance to Pt drugs in cancer cells. This review summarizes the data available from these studies. The observation that cells selected for resistance to Cu or the Pt drugs display bidirectional cross-resistance, parallel defects in the transport of Cu and the Pt drugs and altered expression of Cu transporters is consistent with the concept that the Cu homeostasis proteins regulate sensitivity to the Pt drugs by influencing their uptake, efflux and intracellular distribution. This model is supported by the finding that when mammalian and yeast cells are genetically engineered to express altered levels of the Cu transporters they exhibit altered sensitivity to Pt drugs and are defective in intracellular Pt accumulation due to altered uptake and/or efflux rates. Negative associations between the expression of ATP7A and ATP7B and the outcome of Pt therapy further support the significance of the Cu homeostasis proteins as both markers of and contributors to Pt resistance.
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Affiliation(s)
- Roohangiz Safaei
- Department of Medicine and the Rebecca and John Moores Cancer Center, University of California, 9500 Gilman Drive, San Diego, La Jolla, CA 92093-0058, USA.
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Armendariz AD, Gonzalez M, Loguinov AV, Vulpe CD. Gene expression profiling in chronic copper overload reveals upregulation ofPrnpandApp. Physiol Genomics 2004; 20:45-54. [PMID: 15467011 DOI: 10.1152/physiolgenomics.00196.2003] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The level at which copper becomes toxic is not clear. Several studies have indicated that copper causes oxidative stress; however, most have tested very high levels of copper exposure. We currently have only a limited understanding of the protective systems that operate in cells chronically exposed to copper. Additionally, the limits of homeostatic regulation are not known, making it difficult to define the milder effects of copper excess. Furthermore, a robust assay to facilitate the diagnosis of copper excess and to distinguish mild, moderate, and severe copper overload is needed. To address these issues, we have investigated the effects on steady-state gene expression of chronic copper overload in a cell culture model system using cDNA microarrays. For this study we utilized cells from genetic models of copper overload: fibroblast cells from two mouse mutants, C57BL/6- Atp7aMobrand C57BL/6- Atp7aModap. These cell lines accumulate copper to abnormally high levels in normal culture media due to a defect in copper export from the cell. We identified 12 differentially expressed genes in common using our outlier identification methods. Surprisingly, our results show no evidence of oxidative stress in the copper-loaded cells. In addition, candidate components perhaps responsible for a copper-specific homeostatic response are identified. The genes that encode for the prion protein and the amyloid-β precursor protein, two known copper-binding proteins, are upregulated in both cell lines.
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Affiliation(s)
- Angela D Armendariz
- Department of Nutritional Science and Toxicology, University of California, Berkeley 94720, USA
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