1
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Roseman GP, Wu B, Wadolkowski MA, Harris DA, Millhauser GL. Intrinsic toxicity of the cellular prion protein is regulated by its conserved central region. FASEB J 2020; 34:8734-8748. [PMID: 32385908 DOI: 10.1096/fj.201902749rr] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 04/08/2020] [Accepted: 04/20/2020] [Indexed: 11/11/2022]
Abstract
The conserved central region (CR) of PrPC has been hypothesized to serve as a passive linker connecting the protein's toxic N-terminal and globular C-terminal domains. Yet, deletion of the CR causes neonatal fatality in mice, implying the CR possesses a protective function. The CR encompasses the regulatory α-cleavage locus, and additionally facilitates a regulatory metal ion-promoted interaction between the PrPC N- and C-terminal domains. To elucidate the role of the CR and determine why CR deletion generates toxicity, we designed PrPC constructs wherein either the cis-interaction or α-cleavage are selectively prevented. These constructs were interrogated using nuclear magnetic resonance, electrophysiology, and cell viability assays. Our results demonstrate the CR is not a passive linker and the native sequence is crucial for its protective role over the toxic N-terminus, irrespective of α-cleavage or the cis-interaction. Additionally, we find that the CR facilitates homodimerization of PrPC , attenuating the toxicity of the N-terminus.
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Affiliation(s)
- Graham P Roseman
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Bei Wu
- Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Mark A Wadolkowski
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
| | - David A Harris
- Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
| | - Glenn L Millhauser
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA
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2
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Hackl S, Becker CFW. Prion protein-Semisynthetic prion protein (PrP) variants with posttranslational modifications. J Pept Sci 2019; 25:e3216. [PMID: 31713950 PMCID: PMC6899880 DOI: 10.1002/psc.3216] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 08/23/2019] [Accepted: 08/23/2019] [Indexed: 12/16/2022]
Abstract
Deciphering the pathophysiologic events in prion diseases is challenging, and the role of posttranslational modifications (PTMs) such as glypidation and glycosylation remains elusive due to the lack of homogeneous protein preparations. So far, experimental studies have been limited in directly analyzing the earliest events of the conformational change of cellular prion protein (PrPC ) into scrapie prion protein (PrPSc ) that further propagates PrPC misfolding and aggregation at the cellular membrane, the initial site of prion infection, and PrP misfolding, by a lack of suitably modified PrP variants. PTMs of PrP, especially attachment of the glycosylphosphatidylinositol (GPI) anchor, have been shown to be crucially involved in the PrPSc formation. To this end, semisynthesis offers a unique possibility to understand PrP behavior invitro and invivo as it provides access to defined site-selectively modified PrP variants. This approach relies on the production and chemoselective linkage of peptide segments, amenable to chemical modifications, with recombinantly produced protein segments. In this article, advances in understanding PrP conversion using semisynthesis as a tool to obtain homogeneous posttranslationally modified PrP will be discussed.
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Affiliation(s)
- Stefanie Hackl
- University of Vienna, Faculty of Chemistry, Institute of Biological Chemistry, Vienna, Austria
| | - Christian F W Becker
- University of Vienna, Faculty of Chemistry, Institute of Biological Chemistry, Vienna, Austria
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3
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Kouadri A, El Khatib M, Cormenier J, Chauvet S, Zeinyeh W, El Khoury M, Macari L, Richaud P, Coraux C, Michaud-Soret I, Alfaidy N, Benharouga M. Involvement of the Prion Protein in the Protection of the Human Bronchial Epithelial Barrier Against Oxidative Stress. Antioxid Redox Signal 2019; 31:59-74. [PMID: 30569742 DOI: 10.1089/ars.2018.7500] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Aim: Bronchial epithelium acts as a defensive barrier against inhaled pollutants and microorganisms. This barrier is often compromised in inflammatory airway diseases that are characterized by excessive oxidative stress responses, leading to bronchial epithelial shedding, barrier failure, and increased bronchial epithelium permeability. Among proteins expressed in the junctional barrier and participating to the regulation of the response to oxidative and to environmental stresses is the cellular prion protein (PrPC). However, the role of PrPC is still unknown in the bronchial epithelium. Herein, we investigated the cellular mechanisms by which PrPC protein participates into the junctional complexes formation, regulation, and oxidative protection in human bronchial epithelium. Results: Both PrPC messenger RNA and mature protein were expressed in human epithelial bronchial cells. PrPC was localized in the apical domain and became lateral, at high degree of cell polarization, where it colocalized and interacted with adherens (E-cadherin/γ-catenin) and desmosomal (desmoglein/desmoplakin) junctional proteins. No interaction was detected with tight junction proteins. Disruption of such interactions induced the loss of the epithelial barrier. Moreover, we demonstrated that PrPC protection against copper-associated oxidative stress was involved in multiple processes, including the stability of adherens and desmosomal junctional proteins. Innovation: PrPC is a pivotal protein in the protection against oxidative stress that is associated with the degradation of adherens and desmosomal junctional proteins. Conclusion: Altogether, these results demonstrate that the loss of the integrity of the epithelial barrier by oxidative stress is attenuated by the activation of PrPC expression, where deregulation might be associated with respiratory diseases.
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Affiliation(s)
- Amal Kouadri
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Mariam El Khatib
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Johanna Cormenier
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Sylvain Chauvet
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Wael Zeinyeh
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Micheline El Khoury
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Laurence Macari
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
| | - Pierre Richaud
- 2 University of Aix-Marseille, CNRS, CEA, Institute of Bisosciences and Biotechnologies of Aix Marseille (BIAM), UMR 7265, CEA Cadarache, Saint-Paul-lez Durance, France
| | - Christelle Coraux
- 3 National Institute of Health and Medical Research (INSERM), UMR-S 903, Reims, France
| | | | - Nadia Alfaidy
- 4 University of Grenoble Alpes, INSERM U1036, CEA, BIG, BCI, Grenoble, France
| | - Mohamed Benharouga
- 1 University of Grenoble Alpes, CNRS, UMR 5249, CEA, BIG, CBM, Grenoble, France
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4
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Arkhipenko A, Syan S, Victoria GS, Lebreton S, Zurzolo C. PrPC Undergoes Basal to Apical Transcytosis in Polarized Epithelial MDCK Cells. PLoS One 2016; 11:e0157991. [PMID: 27389581 PMCID: PMC4936696 DOI: 10.1371/journal.pone.0157991] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 06/08/2016] [Indexed: 01/05/2023] Open
Abstract
The Prion Protein (PrP) is an ubiquitously expressed glycosylated membrane protein attached to the external leaflet of the plasma membrane via a glycosylphosphatidylinositol anchor (GPI). While the misfolded PrPSc scrapie isoform is the infectious agent of prion disease, the cellular isoform (PrPC) is an enigmatic protein with unclear function. Of interest, PrP localization in polarized MDCK cells is controversial and its mechanism of trafficking is not clear. Here we investigated PrP traffic in MDCK cells polarized on filters and in three-dimensional MDCK cysts, a more physiological model of polarized epithelia. We found that, unlike other GPI-anchored proteins (GPI-APs), PrP undergoes basolateral-to-apical transcytosis in fully polarized MDCK cells. Following this event full-length PrP and its cleavage fragments are segregated in different domains of the plasma membrane in polarized cells in both 2D and 3D cultures.
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Affiliation(s)
- Alexander Arkhipenko
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, 25-28 rue du docteur Roux, 75015, Paris, France
| | - Sylvie Syan
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, 25-28 rue du docteur Roux, 75015, Paris, France
| | - Guiliana Soraya Victoria
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, 25-28 rue du docteur Roux, 75015, Paris, France
| | - Stéphanie Lebreton
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, 25-28 rue du docteur Roux, 75015, Paris, France
| | - Chiara Zurzolo
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, 25-28 rue du docteur Roux, 75015, Paris, France
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5
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Massignan T, Cimini S, Stincardini C, Cerovic M, Vanni I, Elezgarai SR, Moreno J, Stravalaci M, Negro A, Sangiovanni V, Restelli E, Riccardi G, Gobbi M, Castilla J, Borsello T, Nonno R, Biasini E. A cationic tetrapyrrole inhibits toxic activities of the cellular prion protein. Sci Rep 2016; 6:23180. [PMID: 26976106 PMCID: PMC4791597 DOI: 10.1038/srep23180] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/29/2016] [Indexed: 12/11/2022] Open
Abstract
Prion diseases are rare neurodegenerative conditions associated with the conformational conversion of the cellular prion protein (PrPC) into PrPSc, a self-replicating isoform (prion) that accumulates in the central nervous system of affected individuals. The structure of PrPSc is poorly defined, and likely to be heterogeneous, as suggested by the existence of different prion strains. The latter represents a relevant problem for therapy in prion diseases, as some potent anti-prion compounds have shown strain-specificity. Designing therapeutics that target PrPC may provide an opportunity to overcome these problems. PrPC ligands may theoretically inhibit the replication of multiple prion strains, by acting on the common substrate of any prion replication reaction. Here, we characterized the properties of a cationic tetrapyrrole [Fe(III)-TMPyP], which was previously shown to bind PrPC, and inhibit the replication of a mouse prion strain. We report that the compound is active against multiple prion strains in vitro and in cells. Interestingly, we also find that Fe(III)-TMPyP inhibits several PrPC-related toxic activities, including the channel-forming ability of a PrP mutant, and the PrPC-dependent synaptotoxicity of amyloid-β (Aβ) oligomers, which are associated with Alzheimer’s Disease. These results demonstrate that molecules binding to PrPC may produce a dual effect of blocking prion replication and inhibiting PrPC-mediated toxicity.
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Affiliation(s)
- Tania Massignan
- Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy.,Dulbecco Telethon Institute, Laboratory of Prions and Amyloids, Centre for Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
| | - Sara Cimini
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy
| | - Claudia Stincardini
- Dulbecco Telethon Institute, Laboratory of Prions and Amyloids, Centre for Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
| | - Milica Cerovic
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy
| | - Ilaria Vanni
- Department of Food Safety and Veterinary Health, Istituto Superiore di Sanitá, 00161 Rome, Italy
| | - Saioa R Elezgarai
- Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy.,Dulbecco Telethon Institute, Laboratory of Prions and Amyloids, Centre for Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
| | - Jorge Moreno
- CIC bioGUNE, Parque tecnológico de Bizkaia, Derio 48160, Bizkaia, Spain
| | - Matteo Stravalaci
- Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy
| | - Alessandro Negro
- Department of Biomedical Sciences, University of Padova, 35121 Padova, Italy
| | - Valeria Sangiovanni
- Dulbecco Telethon Institute, Laboratory of Prions and Amyloids, Centre for Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
| | - Elena Restelli
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy
| | - Geraldina Riccardi
- Department of Food Safety and Veterinary Health, Istituto Superiore di Sanitá, 00161 Rome, Italy
| | - Marco Gobbi
- Department of Molecular Biochemistry and Pharmacology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy
| | - Joaquín Castilla
- CIC bioGUNE, Parque tecnológico de Bizkaia, Derio 48160, Bizkaia, Spain.,IKERBASQUE, Basque Foundation for Science, Bilbao 48013, Bizkaia, Spain
| | - Tiziana Borsello
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy.,Department of Pharmacological and Biomolecular Sciences, Milan University, 20133 Milan Italy
| | - Romolo Nonno
- Department of Food Safety and Veterinary Health, Istituto Superiore di Sanitá, 00161 Rome, Italy
| | - Emiliano Biasini
- Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, 20156 Milan, Italy.,Department of Food Safety and Veterinary Health, Istituto Superiore di Sanitá, 00161 Rome, Italy.,Dulbecco Telethon Institute, Laboratory of Prions and Amyloids, Centre for Integrative Biology (CIBIO), University of Trento, 38123 Trento, Italy
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6
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Iraci N, Stincardini C, Barreca ML, Biasini E. Decoding the function of the N-terminal tail of the cellular prion protein to inspire novel therapeutic avenues for neurodegenerative diseases. Virus Res 2015; 207:62-8. [DOI: 10.1016/j.virusres.2014.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 09/18/2014] [Accepted: 10/14/2014] [Indexed: 01/13/2023]
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7
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Chu NK, Shabbir W, Bove-Fenderson E, Araman C, Lemmens-Gruber R, Harris DA, Becker CFW. A C-terminal membrane anchor affects the interactions of prion proteins with lipid membranes. J Biol Chem 2014; 289:30144-60. [PMID: 25217642 DOI: 10.1074/jbc.m114.587345] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Membrane attachment via a C-terminal glycosylphosphatidylinositol anchor is critical for conversion of PrP(C) into pathogenic PrP(Sc). Therefore the effects of the anchor on PrP structure and function need to be deciphered. Three PrP variants, including full-length PrP (residues 23-231, FL_PrP), N-terminally truncated PrP (residues 90-231, T_PrP), and PrP missing its central hydrophobic region (Δ105-125, ΔCR_PrP), were equipped with a C-terminal membrane anchor via a semisynthesis strategy. Analyses of the interactions of lipidated PrPs with phospholipid membranes demonstrated that C-terminal membrane attachment induces a different binding mode of PrP to membranes, distinct from that of non-lipidated PrPs, and influences the biochemical and conformational properties of PrPs. Additionally, fluorescence-based assays indicated pore formation by lipidated ΔCR_PrP, a variant that is known to be highly neurotoxic in transgenic mice. This finding was supported by using patch clamp electrophysiological measurements of cultured cells. These results provide new evidence for the role of the membrane anchor in PrP-lipid interactions, highlighting the importance of the N-terminal and the central hydrophobic domain in these interactions.
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Affiliation(s)
- Nam K Chu
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria
| | - Waheed Shabbir
- the Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, and
| | - Erin Bove-Fenderson
- the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Can Araman
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria
| | - Rosa Lemmens-Gruber
- the Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, and
| | - David A Harris
- the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Christian F W Becker
- From the Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria,
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8
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Patel A, Vasiljevic S, Jones IM. Unique structural properties associated with mouse prion Δ105-125 protein. Prion 2013; 7:235-43. [PMID: 23764837 PMCID: PMC3783109 DOI: 10.4161/pri.24429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Murine prion protein deleted for residues 105-125 is intrinsically neurotoxic and mediates a TSE-like phenotype in transgenic mice. Equivalent and overlapping deletions were expressed in E.coli, purified and analyzed. Among mutants spanning the region 95-135, a construct lacking solely residues 105-125 had distinct properties when compared with the full-length prion protein 23-231 or other deletions. This distinction was also apparent followed expression in eukaryotic cells. Unlike the full-length protein, all deletion mutants failed to bind to synthetic membranes in vitro. These data suggest a novel structure for the 105-125 deleted variant that may relate to its biological properties.
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Affiliation(s)
- Avnish Patel
- School of Biological Sciences, University of Reading, Reading, United Kingdom
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9
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Abstract
Growing evidence suggests that a physiological activity of the cellular prion protein (PrP(C)) plays a crucial role in several neurodegenerative disorders, including prion and Alzheimer's diseases. However, how the functional activity of PrP(C) is subverted to deliver neurotoxic signals remains uncertain. Transgenic (Tg) mice expressing PrP with a deletion of residues 105-125 in the central region (referred to as ΔCR PrP) provide important insights into this problem. Tg(ΔCR) mice exhibit neonatal lethality and massive degeneration of cerebellar granule neurons, a phenotype that is dose dependently suppressed by the presence of wild-type PrP. When expressed in cultured cells, ΔCR PrP induces large, ionic currents that can be detected by patch-clamping techniques. Here, we tested the hypothesis that abnormal ion channel activity underlies the neuronal death seen in Tg(ΔCR) mice. We find that ΔCR PrP induces abnormal ionic currents in neurons in culture and in cerebellar slices and that this activity sensitizes the neurons to glutamate-induced, calcium-mediated death. In combination with ultrastructural and biochemical analyses, these results demonstrate a role for glutamate-induced excitotoxicity in PrP-mediated neurodegeneration. A similar mechanism may operate in other neurodegenerative disorders attributable to toxic, β-rich oligomers that bind to PrP(C).
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10
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Solomon IH, Biasini E, Harris DA. Ion channels induced by the prion protein: mediators of neurotoxicity. Prion 2012; 6:40-5. [PMID: 22453177 DOI: 10.4161/pri.6.1.18627] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Prion diseases comprise a group of rapidly progressive and invariably fatal neurodegenerative disorders for which there are no effective treatments. While conversion of the cellular prion protein (PrP(C)) to a β-sheet rich isoform (PrP(Sc) ) is known to be a critical event in propagation of infectious prions, the identity of the neurotoxic form of PrP and its mechanism of action remain unclear. Insights into this mechanism have been provided by studying PrP molecules harboring deletions and point mutations in the conserved central region, encompassing residues 105-125. When expressed in transgenic mice, PrP deleted for these residues (Δ105-125) causes a spontaneous neurodegenerative illness that is reversed by co-expression of wild-type PrP. In cultured cells, Δ105-125 PrP confers hypersensitivity to certain cationic antibiotics and induces spontaneous ion channel activity that can be recorded by electrophysiological techniques. We have utilized these drug-hypersensitization and current-inducing activities to identify which PrP domains and subcellular locations are required for toxicity. We present an ion channel model for the toxicity of Δ105-125 PrP and related mutants and speculate how a similar mechanism could mediate PrP(Sc)-associated toxicity. Therapeutic regimens designed to inhibit prion-induced toxicity, as well as formation of PrP(Sc) , may prove to be the most clinically beneficial.
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Affiliation(s)
- Isaac H Solomon
- Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
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11
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Biasini E, Turnbaugh JA, Massignan T, Veglianese P, Forloni G, Bonetto V, Chiesa R, Harris DA. The toxicity of a mutant prion protein is cell-autonomous, and can be suppressed by wild-type prion protein on adjacent cells. PLoS One 2012; 7:e33472. [PMID: 22428057 PMCID: PMC3299791 DOI: 10.1371/journal.pone.0033472] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 02/09/2012] [Indexed: 12/25/2022] Open
Abstract
Insight into the normal function of PrPC, and how it can be subverted to produce neurotoxic effects, is provided by PrP molecules carrying deletions encompassing the conserved central region. The most neurotoxic of these mutants, Δ105–125 (called ΔCR), produces a spontaneous neurodegenerative illness when expressed in transgenic mice, and this phenotype can be dose-dependently suppressed by co-expression of wild-type PrP. Whether the toxic activity of ΔCR PrP and the protective activity or wild-type PrP are cell-autonomous, or can be exerted on neighboring cells, is unknown. To investigate this question, we have utilized co-cultures of differentiated neural stem cells derived from mice expressing ΔCR or wild-type PrP. Cells from the two kinds of mice, which are marked by the presence or absence of GFP, are differentiated together to yield neurons, astrocytes, and oligodendrocytes. As a surrogate read-out of ΔCR PrP toxicity, we assayed sensitivity of the cells to the cationic antibiotic, Zeocin. In a previous study, we reported that cells expressing ΔCR PrP are hypersensitive to the toxic effects of several cationic antibiotics, an effect that is suppressed by co-expression of wild type PrP, similar to the rescue of the neurodegenerative phenotype observed in transgenic mice. Using this system, we find that while ΔCR-dependent toxicity is cell-autonomous, the rescuing activity of wild-type PrP can be exerted in trans from nearby cells. These results provide important insights into how ΔCR PrP subverts a normal physiological function of PrPC, and the cellular mechanisms underlying the rescuing process.
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Affiliation(s)
- Emiliano Biasini
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, United States of America
- Dulbecco Telethon Institute, Milan, Italy
- Department of Neuroscience, Mario Negri Institute, Milan, Italy
- * E-mail: (EB); (DAH)
| | - Jessie A. Turnbaugh
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Tania Massignan
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, United States of America
- Dulbecco Telethon Institute, Milan, Italy
- Department of Biochemistry and Molecular Pharmacology, Mario Negri Institute, Milan, Italy
| | | | | | - Valentina Bonetto
- Dulbecco Telethon Institute, Milan, Italy
- Department of Biochemistry and Molecular Pharmacology, Mario Negri Institute, Milan, Italy
| | - Roberto Chiesa
- Dulbecco Telethon Institute, Milan, Italy
- Department of Neuroscience, Mario Negri Institute, Milan, Italy
| | - David A. Harris
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail: (EB); (DAH)
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12
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Abstract
Transgenic mice expressing prion protein (PrP) molecules with several different internal deletions display spontaneous neurodegenerative phenotypes that can be dose-dependently suppressed by coexpression of wild-type PrP. Each of these deletions, including the largest one (Δ32-134), retains 9 aa immediately following the signal peptide cleavage site (residues 23-31; KKRPKPGGW). These residues have been implicated in several biological functions of PrP, including endocytic trafficking and binding of glycosaminoglycans. We report here on our experiments to test the role of this domain in the toxicity of deleted forms of PrP. We find that transgenic mice expressing Δ23-134 PrP display no clinical symptoms or neuropathology, in contrast to mice expressing Δ32-134 PrP, suggesting that residues 23-31 are essential for the toxic phenotype. Using a newly developed cell culture assay, we narrow the essential region to amino acids 23-26, and we show that mutant PrP toxicity is not related to the role of the N-terminal residues in endocytosis or binding to endogenous glycosaminoglycans. However, we find that mutant PrP toxicity is potently inhibited by application of exogenous glycosaminoglycans, suggesting that the latter molecules block an essential interaction between the N terminus of PrP and a membrane-associated target site. Our results demonstrate that a short segment containing positively charged amino acids at the N terminus of PrP plays an essential role in mediating PrP-related neurotoxicity. This finding identifies a protein domain that may serve as a drug target for amelioration of prion neurotoxicity.
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13
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Solomon IH, Khatri N, Biasini E, Massignan T, Huettner JE, Harris DA. An N-terminal polybasic domain and cell surface localization are required for mutant prion protein toxicity. J Biol Chem 2011; 286:14724-36. [PMID: 21385869 DOI: 10.1074/jbc.m110.214973] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
There is evidence that alterations in the normal physiological activity of PrP(C) contribute to prion-induced neurotoxicity. This mechanism has been difficult to investigate, however, because the normal function of PrP(C) has remained obscure, and there are no assays available to measure it. We recently reported that cells expressing PrP deleted for residues 105-125 exhibit spontaneous ionic currents and hypersensitivity to certain classes of cationic drugs. Here, we utilize cell culture assays based on these two phenomena to test how changes in PrP sequence and/or cellular localization affect the functional activity of the protein. We report that the toxic activity of Δ105-125 PrP requires localization to the plasma membrane and depends on the presence of a polybasic amino acid segment at the N terminus of PrP. Several different deletions spanning the central region as well as three disease-associated point mutations also confer toxic activity on PrP. The sequence domains identified in our study are also critical for PrP(Sc) formation, suggesting that common structural features may govern both the functional activity of PrP(C) and its conversion to PrP(Sc).
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Affiliation(s)
- Isaac H Solomon
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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14
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Solomon IH, Huettner JE, Harris DA. Neurotoxic mutants of the prion protein induce spontaneous ionic currents in cultured cells. J Biol Chem 2010; 285:26719-26. [PMID: 20573963 DOI: 10.1074/jbc.m110.134619] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The mechanisms by which prions kill neurons and the role of the cellular prion protein in this process are enigmatic. Insight into these questions is provided by the neurodegenerative phenotypes of transgenic mice expressing prion protein (PrP) molecules with deletions of conserved amino acids in the central region. We report here that expression in transfected cells of the most toxic of these PrP deletion mutants (Delta105-125) induces large, spontaneous ionic currents that can be detected by patch-clamping techniques. These currents are produced by relatively non-selective, cation-permeable channels or pores in the cell membrane and can be silenced by overexpression of wild-type PrP, as well as by treatment with a sulfated glycosaminoglycan. Similar currents are induced by PrP molecules carrying several different point mutations in the central region that cause familial prion diseases in humans. The ionic currents described here are distinct from those produced in artificial lipid membranes by synthetic peptides derived from the PrP sequence because they are induced by membrane-anchored forms of PrP that are synthesized by cells and that are found in vivo. Our results indicate that the neurotoxicity of some mutant forms of PrP is attributable to enhanced ion channel activity and that wild-type PrP possesses a channel-silencing activity. Drugs that block PrP-associated channels or pores may therefore represent novel therapeutic agents for treatment of patients with prion diseases.
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Affiliation(s)
- Isaac H Solomon
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Christensen HM, Dikranian K, Li A, Baysac KC, Walls KC, Olney JW, Roth KA, Harris DA. A highly toxic cellular prion protein induces a novel, nonapoptotic form of neuronal death. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 176:2695-706. [PMID: 20472884 DOI: 10.2353/ajpath.2010.091007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Several different deletions within the N-terminal tail of the prion protein (PrP) induce massive neuronal death when expressed in transgenic mice. This toxicity is dose-dependently suppressed by coexpression of full-length PrP, suggesting that it results from subversion of a normal physiological activity of cellular PrP. We performed a combined biochemical and morphological analysis of Tg(DeltaCR) mice, which express PrP carrying a 21-aa deletion (residues 105-125) within a highly conserved region of the protein. Death of cerebellar granule neurons in Tg(DeltaCR) mice is not accompanied by activation of either caspase-3 or caspase-8 or by increased levels of the autophagy marker, LC3-II. In electron micrographs, degenerating granule neurons displayed a unique morphology characterized by heterogeneous condensation of the nuclear matrix without formation of discrete chromatin masses typical of neuronal apoptosis. Our data demonstrate that perturbations in PrP functional activity induce a novel, nonapoptotic, nonautophagic form of neuronal death whose morphological features are reminiscent of those associated with excitotoxic stress.
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Affiliation(s)
- Heather M Christensen
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, USA
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Unexpected tolerance of alpha-cleavage of the prion protein to sequence variations. PLoS One 2010; 5:e9107. [PMID: 20161712 PMCID: PMC2817006 DOI: 10.1371/journal.pone.0009107] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2009] [Accepted: 01/19/2010] [Indexed: 11/25/2022] Open
Abstract
The cellular form of the prion protein, PrPC, undergoes extensive proteolysis at the α site (109K↓H110). Expression of non-cleavable PrPC mutants in transgenic mice correlates with neurotoxicity, suggesting that α-cleavage is important for PrPC physiology. To gain insights into the mechanisms of α-cleavage, we generated a library of PrPC mutants with mutations in the region neighbouring the α-cleavage site. The prevalence of C1, the carboxy adduct of α-cleavage, was determined for each mutant. In cell lines of disparate origin, C1 prevalence was unaffected by variations in charge and hydrophobicity of the region neighbouring the α-cleavage site, and by substitutions of the residues in the palindrome that flanks this site. Instead, α-cleavage was size-dependently impaired by deletions within the domain 106–119. Almost no cleavage was observed upon full deletion of this domain. These results suggest that α-cleavage is executed by an α-PrPase whose activity, despite surprisingly limited sequence specificity, is dependent on the size of the central region of PrPC.
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Massignan T, Stewart RS, Biasini E, Solomon IH, Bonetto V, Chiesa R, Harris DA. A novel, drug-based, cellular assay for the activity of neurotoxic mutants of the prion protein. J Biol Chem 2009; 285:7752-65. [PMID: 19940127 DOI: 10.1074/jbc.m109.064949] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In prion diseases, the infectious isoform of the prion protein (PrP(Sc)) may subvert a normal, physiological activity of the cellular isoform (PrP(C)). A deletion mutant of the prion protein (Delta105-125) that produces a neonatal lethal phenotype when expressed in transgenic mice provides a window into the normal function of PrP(C) and how it can be corrupted to produce neurotoxic effects. We report here the surprising and unexpected observation that cells expressing Delta105-125 PrP and related mutants are hypersensitive to the toxic effects of two classes of antibiotics (aminoglycosides and bleomycin analogues) that are commonly used for selection of stably transfected cell lines. This unusual phenomenon mimics several essential features of Delta105-125 PrP toxicity seen in transgenic mice, including rescue by co-expression of wild type PrP. Cells expressing Delta105-125 PrP are susceptible to drug toxicity within minutes, suggesting that the mutant protein enhances cellular accumulation of these cationic compounds. Our results establish a screenable cellular phenotype for the activity of neurotoxic forms of PrP, and they suggest possible mechanisms by which these molecules could produce their pathological effects in vivo.
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Affiliation(s)
- Tania Massignan
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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