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Benarroch E. What Are the Roles of Cellular Prion Protein in Normal and Pathologic Conditions? Neurology 2024; 102:e209272. [PMID: 38484222 DOI: 10.1212/wnl.0000000000209272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 03/19/2024] Open
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2
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Taylor KM. The LIV-1 Subfamily of Zinc Transporters: From Origins to Present Day Discoveries. Int J Mol Sci 2023; 24:ijms24021255. [PMID: 36674777 PMCID: PMC9861476 DOI: 10.3390/ijms24021255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/03/2023] [Accepted: 01/06/2023] [Indexed: 01/11/2023] Open
Abstract
This review explains the origin of the LIV-1 family of zinc transporters, paying attention to how this family of nine human proteins was originally discovered. Structural and functional differences between these nine human LIV-1 family members and the five other ZIP transporters are examined. These differences are both related to aspects of the protein sequence, the conservation of important motifs and to the effect this may have on their overall function. The LIV-1 family are dependent on various post-translational modifications, such as phosphorylation and cleavage, which play an important role in their ability to transport zinc. These modifications and their implications are discussed in detail. Some of these proteins have been implicated in cancer which is examined. Furthermore, some additional areas of potential fruitful discovery are discussed and suggested as worthy of examination in the future.
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Affiliation(s)
- Kathryn M Taylor
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Redwood Building, King Edward VIIth Avenue, Cardiff CF10 3NB, UK
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3
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Kambe T, Taylor KM, Fu D. Zinc transporters and their functional integration in mammalian cells. J Biol Chem 2021; 296:100320. [PMID: 33485965 PMCID: PMC7949119 DOI: 10.1016/j.jbc.2021.100320] [Citation(s) in RCA: 95] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/15/2021] [Accepted: 01/20/2021] [Indexed: 12/14/2022] Open
Abstract
Zinc is a ubiquitous biological metal in all living organisms. The spatiotemporal zinc dynamics in cells provide crucial cellular signaling opportunities, but also challenges for intracellular zinc homeostasis with broad disease implications. Zinc transporters play a central role in regulating cellular zinc balance and subcellular zinc distributions. The discoveries of two complementary families of mammalian zinc transporters (ZnTs and ZIPs) in the mid-1990s spurred much speculation on their metal selectivity and cellular functions. After two decades of research, we have arrived at a biochemical description of zinc transport. However, in vitro functions are fundamentally different from those in living cells, where mammalian zinc transporters are directed to specific subcellular locations, engaged in dedicated macromolecular machineries, and connected with diverse cellular processes. Hence, the molecular functions of individual zinc transporters are reshaped and deeply integrated in cells to promote the utilization of zinc chemistry to perform enzymatic reactions, tune cellular responsiveness to pathophysiologic signals, and safeguard cellular homeostasis. At present, the underlying mechanisms driving the functional integration of mammalian zinc transporters are largely unknown. This knowledge gap has motivated a shift of the research focus from in vitro studies of purified zinc transporters to in cell studies of mammalian zinc transporters in the context of their subcellular locations and protein interactions. In this review, we will outline how knowledge of zinc transporters has been accumulated from in-test-tube to in-cell studies, highlighting new insights and paradigm shifts in our understanding of the molecular and cellular basis of mammalian zinc transporter functions.
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Affiliation(s)
- Taiho Kambe
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kathryn M Taylor
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | - Dax Fu
- Department of Physiology, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
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4
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Singh N, Chaudhary S, Ashok A, Lindner E. Prions and prion diseases: Insights from the eye. Exp Eye Res 2020; 199:108200. [PMID: 32858007 DOI: 10.1016/j.exer.2020.108200] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 07/24/2020] [Accepted: 08/21/2020] [Indexed: 12/30/2022]
Abstract
Prion diseases are invariably fatal neurodegenerative disorders that have gained much publicity due to their transmissible nature. Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common human prion disorder, with an incidence of 1 in a million. Inherited prion disorders are relatively rare, and associated with mutations in the prion protein gene. More than 50 different point mutations, deletions, and insertions have been identified so far. Most are autosomal dominant and fully penetrant. Prion disorders also occur in animals, and are of major concern because of the potential for spreading to humans. The principal pathogenic event underlying all prion disorders is a change in the conformation of prion protein (PrPC) from a mainly α-helical to a β-sheet rich isoform, PrP-scrapie (PrPSc). Accumulation of PrPSc in the brain parenchyma is the major cause of neuronal degeneration. The mechanism by which PrPSc is transmitted, propagates, and causes neurodegenerative changes has been investigated over the years, and several clues have emerged. Efforts are also ongoing for identifying specific and sensitive diagnostic tests for sCJD and animal prion disorders, but success has been limited. The eye is suitable for these evaluations because it shares several anatomical and physiological features with the brain, and can be observed in vivo during disease progression. The retina, considered an extension of the central nervous system, is involved extensively in prion disorders. Accordingly, Optical Coherence Tomography and electroretinogram have shown some promise as pre-mortem diagnostic tests for human and animal prion disorders. However, a complete understanding of the physiology of PrPC and pathobiology of PrPSc in the eye is essential for developing specific and sensitive tests. Below, we summarize recent progress in ocular physiology and pathology in prion disorders, and the eye as an anatomically accessible site to diagnose, monitor disease progression, and test therapeutic options.
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Affiliation(s)
- Neena Singh
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.
| | - Suman Chaudhary
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ajay Ashok
- Departments of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ewald Lindner
- Department of Ophthalmology, Medical University of Graz, Auenbruggerplatz 4, 8036, Graz, Austria
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Leighton PLA, Kanyo R, Neil GJ, Pollock NM, Allison WT. Prion gene paralogs are dispensable for early zebrafish development and have nonadditive roles in seizure susceptibility. J Biol Chem 2018; 293:12576-12592. [PMID: 29903907 DOI: 10.1074/jbc.ra117.001171] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 06/07/2018] [Indexed: 11/06/2022] Open
Abstract
Normally folded prion protein (PrPC) and its functions in healthy brains remain underappreciated compared with the intense study of its misfolded forms ("prions," PrPSc) during the pathobiology of prion diseases. This impedes the development of therapeutic strategies in Alzheimer's and prion diseases. Disrupting the zebrafish homologs of PrPC has provided novel insights; however, mutagenesis of the zebrafish paralog prp2 did not recapitulate previous dramatic developmental phenotypes, suggesting redundancy with the prp1 paralog. Here, we generated zebrafish prp1 loss-of-function mutant alleles and dual prp1-/-;prp2-/- mutants. Zebrafish prp1-/- and dual prp1-/-;prp2-/- mutants resemble mammalian Prnp knockouts insofar as they lack overt phenotypes, which surprisingly contrasts with reports of severe developmental phenotypes when either prp1 or prp2 is knocked down acutely. Previous studies suggest that PrPC participates in neural cell development/adhesion, including in zebrafish where loss of prp2 affects adhesion and deposition patterns of lateral line neuromasts. In contrast with the expectation that prp1's functions would be redundant to prp2, they appear to have opposing functions in lateral line neurodevelopment. Similarly, loss of prp1 blunted the seizure susceptibility phenotypes observed in prp2 mutants, contrasting the expected exacerbation of phenotypes if these prion gene paralogs were serving redundant roles. In summary, prion mutant fish lack the overt phenotypes previously predicted, and instead they have subtle phenotypes similar to mammals. No evidence was found for functional redundancy in the zebrafish prion gene paralogs, and the phenotypes observed when each gene is disrupted individually are consistent with ancient functions of prion proteins in neurodevelopment and modulation of neural activity.
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Affiliation(s)
- Patricia L A Leighton
- From the Department of Biological Sciences and the Centre for Prion and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Richard Kanyo
- From the Department of Biological Sciences and the Centre for Prion and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Gavin J Neil
- From the Department of Biological Sciences and the Centre for Prion and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Niall M Pollock
- From the Department of Biological Sciences and the Centre for Prion and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - W Ted Allison
- From the Department of Biological Sciences and the Centre for Prion and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
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6
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Castle AR, Gill AC. Physiological Functions of the Cellular Prion Protein. Front Mol Biosci 2017; 4:19. [PMID: 28428956 PMCID: PMC5382174 DOI: 10.3389/fmolb.2017.00019] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 03/22/2017] [Indexed: 01/09/2023] Open
Abstract
The prion protein, PrPC, is a small, cell-surface glycoprotein notable primarily for its critical role in pathogenesis of the neurodegenerative disorders known as prion diseases. A hallmark of prion diseases is the conversion of PrPC into an abnormally folded isoform, which provides a template for further pathogenic conversion of PrPC, allowing disease to spread from cell to cell and, in some circumstances, to transfer to a new host. In addition to the putative neurotoxicity caused by the misfolded form(s), loss of normal PrPC function could be an integral part of the neurodegenerative processes and, consequently, significant research efforts have been directed toward determining the physiological functions of PrPC. In this review, we first summarise important aspects of the biochemistry of PrPC before moving on to address the current understanding of the various proposed functions of the protein, including details of the underlying molecular mechanisms potentially involved in these functions. Over years of study, PrPC has been associated with a wide array of different cellular processes and many interacting partners have been suggested. However, recent studies have cast doubt on the previously well-established links between PrPC and processes such as stress-protection, copper homeostasis and neuronal excitability. Instead, the functions best-supported by the current literature include regulation of myelin maintenance and of processes linked to cellular differentiation, including proliferation, adhesion, and control of cell morphology. Intriguing connections have also been made between PrPC and the modulation of circadian rhythm, glucose homeostasis, immune function and cellular iron uptake, all of which warrant further investigation.
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Brethour D, Mehrabian M, Williams D, Wang X, Ghodrati F, Ehsani S, Rubie EA, Woodgett JR, Sevalle J, Xi Z, Rogaeva E, Schmitt-Ulms G. A ZIP6-ZIP10 heteromer controls NCAM1 phosphorylation and integration into focal adhesion complexes during epithelial-to-mesenchymal transition. Sci Rep 2017; 7:40313. [PMID: 28098160 PMCID: PMC5241876 DOI: 10.1038/srep40313] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 12/02/2016] [Indexed: 01/06/2023] Open
Abstract
The prion protein (PrP) evolved from the subbranch of ZIP metal ion transporters comprising ZIPs 5, 6 and 10, raising the prospect that the study of these ZIPs may reveal insights relevant for understanding the function of PrP. Building on data which suggested PrP and ZIP6 are critical during epithelial-to-mesenchymal transition (EMT), we investigated ZIP6 in an EMT paradigm using ZIP6 knockout cells, mass spectrometry and bioinformatic methods. Reminiscent of PrP, ZIP6 levels are five-fold upregulated during EMT and the protein forms a complex with NCAM1. ZIP6 also interacts with ZIP10 and the two ZIP transporters exhibit interdependency during their expression. ZIP6 contributes to the integration of NCAM1 in focal adhesion complexes but, unlike cells lacking PrP, ZIP6 deficiency does not abolish polysialylation of NCAM1. Instead, ZIP6 mediates phosphorylation of NCAM1 on a cluster of cytosolic acceptor sites. Substrate consensus motif features and in vitro phosphorylation data point toward GSK3 as the kinase responsible, and interface mapping experiments identified histidine-rich cytoplasmic loops within the ZIP6/ZIP10 heteromer as a novel scaffold for GSK3 binding. Our data suggests that PrP and ZIP6 inherited the ability to interact with NCAM1 from their common ZIP ancestors but have since diverged to control distinct posttranslational modifications of NCAM1.
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Affiliation(s)
- Dylan Brethour
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Laboratory Medicine &Pathobiology, University of Toronto, Ontario, Canada
| | - Mohadeseh Mehrabian
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Laboratory Medicine &Pathobiology, University of Toronto, Ontario, Canada
| | - Declan Williams
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada
| | - Xinzhu Wang
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Laboratory Medicine &Pathobiology, University of Toronto, Ontario, Canada
| | - Farinaz Ghodrati
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Laboratory Medicine &Pathobiology, University of Toronto, Ontario, Canada
| | - Sepehr Ehsani
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Elizabeth A Rubie
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - James R Woodgett
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Jean Sevalle
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada
| | - Zhengrui Xi
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada
| | - Ekaterina Rogaeva
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Neurology, University of Toronto, Ontario, Canada
| | - Gerold Schmitt-Ulms
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Ontario, Canada.,Department of Laboratory Medicine &Pathobiology, University of Toronto, Ontario, Canada
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Singh N, Asthana A, Baksi S, Desai V, Haldar S, Hari S, Tripathi AK. The prion-ZIP connection: From cousins to partners in iron uptake. Prion 2016; 9:420-8. [PMID: 26689487 PMCID: PMC4964862 DOI: 10.1080/19336896.2015.1118602] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Converging observations from disparate lines of inquiry are beginning to clarify the cause of brain iron dyshomeostasis in sporadic Creutzfeldt-Jakob disease (sCJD), a neurodegenerative condition associated with the conversion of prion protein (PrPC), a plasma membrane glycoprotein, from α-helical to a β-sheet rich PrP-scrapie (PrPSc) isoform. Biochemical evidence indicates that PrPC facilitates cellular iron uptake by functioning as a membrane-bound ferrireductase (FR), an activity necessary for the transport of iron across biological membranes through metal transporters. An entirely different experimental approach reveals an evolutionary link between PrPC and the Zrt, Irt-like protein (ZIP) family, a group of proteins involved in the transport of zinc, iron, and manganese across the plasma membrane. Close physical proximity of PrPC with certain members of the ZIP family on the plasma membrane and increased uptake of extracellular iron by cells that co-express PrPC and ZIP14 suggest that PrPC functions as a FR partner for certain members of this family. The connection between PrPC and ZIP proteins therefore extends beyond common ancestry to that of functional cooperation. Here, we summarize evidence supporting the facilitative role of PrPC in cellular iron uptake, and implications of this activity on iron metabolism in sCJD brains.
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Affiliation(s)
- Neena Singh
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Abhishek Asthana
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Shounak Baksi
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Vilok Desai
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Swati Haldar
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Sahi Hari
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
| | - Ajai K Tripathi
- a Department of Pathology ; School of Medicine; Case Western Reserve University ; Cleveland , OH USA
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Mehrabian M, Ehsani S, Schmitt-Ulms G. An emerging role of the cellular prion protein as a modulator of a morphogenetic program underlying epithelial-to-mesenchymal transition. Front Cell Dev Biol 2014; 2:53. [PMID: 25453033 PMCID: PMC4233941 DOI: 10.3389/fcell.2014.00053] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 09/03/2014] [Indexed: 12/31/2022] Open
Abstract
Knowledge of phenotypic changes the cellular prion protein (PrP(C)) contributes to may provide novel avenues for understanding its function. Here we consider data from functional knockout/down studies and protein-protein interaction analyses from the perspective of PrP's relationship to its ancestral ZIP metal ion transporting proteins. When approached in this manner, a role of PrP(C) as a modulator of a complex morphogenetic program that underlies epithelial-to-mesenchymal transition (EMT) emerges. To execute EMT, cells have to master the challenge to shift from cell-cell to cell-substrate modes of adherence. During this process, cell-cell junctions stabilized by E-cadherins are replaced by focal adhesions that mediate cell-substrate contacts. A similar reprogramming occurs during distinct organogenesis events that have been shown to rely on ZIP transporters. A model is presented that sees ZIP transporters, and possibly also PrP(C), affect this balance of adherence modes at both the transcriptional and post-translational levels.
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Affiliation(s)
- Mohadeseh Mehrabian
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto Toronto, ON, Canada ; Department of Laboratory Medicine and Pathobiology, University of Toronto Toronto, ON, Canada
| | - Sepehr Ehsani
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto Toronto, ON, Canada ; Department of Laboratory Medicine and Pathobiology, University of Toronto Toronto, ON, Canada
| | - Gerold Schmitt-Ulms
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto Toronto, ON, Canada ; Department of Laboratory Medicine and Pathobiology, University of Toronto Toronto, ON, Canada
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