1
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Shoup D, Priola SA. Grp78 destabilization of infectious prions is strain-specific and modified by multiple factors including accessory chaperones and pH. J Biol Chem 2024; 300:107346. [PMID: 38718859 PMCID: PMC11176782 DOI: 10.1016/j.jbc.2024.107346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 04/01/2024] [Accepted: 04/22/2024] [Indexed: 06/03/2024] Open
Abstract
Lethal neurodegenerative prion diseases result from the continuous accumulation of infectious and variably protease-resistant prion protein aggregates (PrPD) which are misfolded forms of the normally detergent soluble and protease-sensitive cellular prion protein. Molecular chaperones like Grp78 have been found to reduce the accumulation of PrPD, but how different cellular environments and other chaperones influence the ability of Grp78 to modify PrPD is poorly understood. In this work, we investigated how pH and protease-mediated structural changes in PrPD from two mouse-adapted scrapie prion strains, 22L and 87V, influenced processing by Grp78 in the presence or absence of chaperones Hsp90, DnaJC1, and Stip1. We developed a cell-free in vitro system to monitor chaperone-mediated structural changes to, and disaggregation of, PrPD. For both strains, Grp78 was most effective at structurally altering PrPD at low pH, especially when additional chaperones were present. While Grp78, DnaJC1, Stip1, and Hsp90 were unable to disaggregate the majority of PrPD from either strain, pretreatment of PrPD with proteases increased disaggregation of 22L PrPD compared to 87V, indicating strain-specific differences in aggregate structure were impacting chaperone activity. Hsp90 also induced structural changes in 87V PrPD as indicated by an increase in the susceptibility of its n-terminus to proteases. Our data suggest that, while chaperones like Grp78, DnaJC1, Stip1, and Hsp90 disaggregate only a small fraction of PrPD, they may still facilitate its clearance by altering aggregate structure and sensitizing PrPD to proteases in a strain and pH-dependent manner.
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Affiliation(s)
- Daniel Shoup
- Rocky Mountain Laboratories, Laboratory of Neurological Infections and Immunity, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA.
| | - Suzette A Priola
- Rocky Mountain Laboratories, Laboratory of Neurological Infections and Immunity, National Institute of Allergy & Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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2
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Race B, Baune C, Williams K, Striebel JF, Hughson AG, Chesebro B. Second passage experiments of chronic wasting disease in transgenic mice overexpressing human prion protein. Vet Res 2022; 53:111. [PMID: 36527166 PMCID: PMC9758843 DOI: 10.1186/s13567-022-01130-0] [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: 10/06/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022] Open
Abstract
Chronic wasting disease (CWD) is a prion disease of cervids including deer, elk, reindeer, and moose. Human consumption of cervids is common, therefore assessing the risk potential of CWD transmission to humans is critical. In a previous study, we tested CWD transmission via intracerebral inoculation into transgenic mice (tg66 and tgRM) that over-expressed human prion protein. Mice screened by traditional prion detection assays were negative. However, in a group of 88 mice screened by the ultrasensitive RT-QuIC assay, we identified 4 tg66 mice that produced inconsistent positive RT-QuIC reactions. These data could be false positive reactions, residual input inoculum or indicative of subclinical infections suggestive of cross species transmission of CWD to humans. Additional experiments were required to understand the nature of the prion seeding activity in this model. In this manuscript, second passage experiments using brains from mice with weak prion seeding activity showed they were not infectious to additional recipient tg66 mice. Clearance experiments showed that input CWD prion seeding activity was eliminated by 180 days in tg66 mice and PrPKO mice, which are unable to replicate prion protein, indicating that the weak positive levels of seeding activity detected at later time points was not likely residual inoculum. The failure of CWD prions to cause disease in tg66 after two sequential passages suggested that a strong species barrier prevented CWD infection of mice expressing human prion protein.
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Affiliation(s)
- Brent Race
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA.
| | - Chase Baune
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA
| | - Katie Williams
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA
| | - James F Striebel
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA
| | - Andrew G Hughson
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA
| | - Bruce Chesebro
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South Fourth Street, Hamilton, MT, 59840, USA
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3
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Matamoros-Angles A, Hervera A, Soriano J, Martí E, Carulla P, Llorens F, Nuvolone M, Aguzzi A, Ferrer I, Gruart A, Delgado-García JM, Del Río JA. Analysis of co-isogenic prion protein deficient mice reveals behavioral deficits, learning impairment, and enhanced hippocampal excitability. BMC Biol 2022; 20:17. [PMID: 35027047 PMCID: PMC8759182 DOI: 10.1186/s12915-021-01203-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 12/02/2021] [Indexed: 12/22/2022] Open
Abstract
Background Cellular prion protein (PrPC) is a cell surface GPI-anchored protein, usually known for its role in the pathogenesis of human and animal prionopathies. However, increasing knowledge about the participation of PrPC in prion pathogenesis contrasts with puzzling data regarding its natural physiological role. PrPC is expressed in a number of tissues, including at high levels in the nervous system, especially in neurons and glial cells, and while previous studies have established a neuroprotective role, conflicting evidence for a synaptic function has revealed both reduced and enhanced long-term potentiation, and variable observations on memory, learning, and behavior. Such evidence has been confounded by the absence of an appropriate knock-out mouse model to dissect the biological relevance of PrPC, with some functions recently shown to be misattributed to PrPC due to the presence of genetic artifacts in mouse models. Here we elucidate the role of PrPC in the hippocampal circuitry and its related functions, such as learning and memory, using a recently available strictly co-isogenic Prnp0/0 mouse model (PrnpZH3/ZH3). Results We performed behavioral and operant conditioning tests to evaluate memory and learning capabilities, with results showing decreased motility, impaired operant conditioning learning, and anxiety-related behavior in PrnpZH3/ZH3 animals. We also carried in vivo electrophysiological recordings on CA3-CA1 synapses in living behaving mice and monitored spontaneous neuronal firing and network formation in primary neuronal cultures of PrnpZH3/ZH3 vs wildtype mice. PrPC absence enhanced susceptibility to high-intensity stimulations and kainate-induced seizures. However, long-term potentiation (LTP) was not enhanced in the PrnpZH3/ZH3 hippocampus. In addition, we observed a delay in neuronal maturation and network formation in PrnpZH3/ZH3 cultures. Conclusion Our results demonstrate that PrPC promotes neuronal network formation and connectivity. PrPC mediates synaptic function and protects the synapse from excitotoxic insults. Its deletion may underlie an epileptogenic-susceptible brain that fails to perform highly cognitive-demanding tasks such as associative learning and anxiety-like behaviors. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01203-0.
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Affiliation(s)
- A Matamoros-Angles
- Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Barcelona, Barcelona, Spain.,CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain.,Institute of Neuroscience, University of Barcelona, Barcelona, Spain.,Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - A Hervera
- Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Barcelona, Barcelona, Spain.,CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain.,Institute of Neuroscience, University of Barcelona, Barcelona, Spain
| | - J Soriano
- Departament de Física de la Materia Condensada, University of Barcelona, Barcelona, Spain.,Institute of Complex Systems (UBICS), University of Barcelona, Barcelona, Spain
| | - E Martí
- Department of Biomedicine, University of Barcelona, Barcelona, Spain.,Bioinformatics and Genomics, Center for Genomic Regulation, Barcelona, Spain
| | - P Carulla
- Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain.,Department of Cell Biology, Physiology, and Immunology, University of Barcelona, Barcelona, Spain.,CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain
| | - F Llorens
- CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain.,Department of Neurology, University Medical School, Göttingen, Germany.,Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Catalonia, Spain
| | - M Nuvolone
- Institute of Neuropathology, University Hospital of Zürich, Zürich, Switzerland.,Amyloidosis Center, Foundation IRCCS Policlinico San Matteo, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - A Aguzzi
- Institute of Neuropathology, University Hospital of Zürich, Zürich, Switzerland
| | - I Ferrer
- CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain.,Institute of Neuroscience, University of Barcelona, Barcelona, Spain.,Senior Consultant, Bellvitge University Hospital, IDIBELL (Bellvitge Biomedical Research Centre), L'Hospitalet de Llobregat, Spain.,Department of Pathology and Experimental Therapeutics, University of Barcelona, Barcelona, Spain
| | - A Gruart
- Division of Neurosciences, Pablo de Olavide University, 41013, Seville, Spain
| | - J M Delgado-García
- Division of Neurosciences, Pablo de Olavide University, 41013, Seville, Spain.
| | - J A Del Río
- Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain. .,Department of Cell Biology, Physiology, and Immunology, University of Barcelona, Barcelona, Spain. .,CIBERNED (Network Centre of Biomedical Research of Neurodegenerative Diseases), Institute of Health Carlos III, Barcelona, Spain. .,Institute of Neuroscience, University of Barcelona, Barcelona, Spain.
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4
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Adão-Novaes J, Valverde R, Landemberger M, Silveira M, Simões-Pires E, Lowe J, Linden R. Substrain-related dependence of Cu(I)-ATPase activity among prion protein-null mice. Brain Res 2020; 1727:146550. [DOI: 10.1016/j.brainres.2019.146550] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 11/08/2019] [Accepted: 11/09/2019] [Indexed: 01/20/2023]
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5
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Minikel EV, Kuhn E, Cocco AR, Vallabh SM, Hartigan CR, Reidenbach AG, Safar JG, Raymond GJ, McCarthy MD, O'Keefe R, Llorens F, Zerr I, Capellari S, Parchi P, Schreiber SL, Carr SA. Domain-specific Quantification of Prion Protein in Cerebrospinal Fluid by Targeted Mass Spectrometry. Mol Cell Proteomics 2019; 18:2388-2400. [PMID: 31558565 PMCID: PMC6885701 DOI: 10.1074/mcp.ra119.001702] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/16/2019] [Indexed: 01/11/2023] Open
Abstract
Therapies currently in preclinical development for prion disease seek to lower prion protein (PrP) expression in the brain. Trials of such therapies are likely to rely on quantification of PrP in cerebrospinal fluid (CSF) as a pharmacodynamic biomarker and possibly as a trial endpoint. Studies using PrP ELISA kits have shown that CSF PrP is lowered in the symptomatic phase of disease, a potential confounder for reading out the effect of PrP-lowering drugs in symptomatic patients. Because misfolding or proteolytic cleavage could potentially render PrP invisible to ELISA even if its concentration were constant or increasing in disease, we sought to establish an orthogonal method for CSF PrP quantification. We developed a multi-species targeted mass spectrometry method based on multiple reaction monitoring (MRM) of nine PrP tryptic peptides quantified relative to an isotopically labeled recombinant protein standard for human samples, or isotopically labeled synthetic peptides for nonhuman species. Analytical validation experiments showed process replicate coefficients of variation below 15%, good dilution linearity and recovery, and suitable performance for both CSF and brain homogenate and across humans as well as preclinical species of interest. In n = 55 CSF samples from individuals referred to prion surveillance centers with rapidly progressive dementia, all six human PrP peptides, spanning the N- and C-terminal domains of PrP, were uniformly reduced in prion disease cases compared with individuals with nonprion diagnoses. Thus, lowered CSF PrP concentration in prion disease is a genuine result of the disease process and not an artifact of ELISA-based measurement. As a result, dose-finding studies for PrP lowering drugs may need to be conducted in presymptomatic at-risk individuals rather than in symptomatic patients. We provide a targeted mass spectrometry-based method suitable for preclinical quantification of CSF PrP as a tool for drug development.
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Affiliation(s)
- Eric Vallabh Minikel
- Chemical Biology and Therapeutics Science Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142; Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA 02115; Prion Alliance, Cambridge, MA 02139; Proteomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142.
| | - Eric Kuhn
- Proteomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142; Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA 02115
| | - Alexandra R Cocco
- Proteomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142
| | - Sonia M Vallabh
- Chemical Biology and Therapeutics Science Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142; Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, MA 02115; Prion Alliance, Cambridge, MA 02139
| | | | - Andrew G Reidenbach
- Chemical Biology and Therapeutics Science Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142
| | - Jiri G Safar
- Departments of Pathology and Neurology Case Western Reserve University, Cleveland, OH 44106
| | - Gregory J Raymond
- Laboratory of Persistent Viral Diseases, NIAID Rocky Mountain Labs, Hamilton, MT 59840
| | - Michael D McCarthy
- Environmental Health and Safety, Broad Institute of MIT and Harvard, Cambridge, MA 02142
| | - Rhonda O'Keefe
- Environmental Health and Safety, Broad Institute of MIT and Harvard, Cambridge, MA 02142
| | - Franc Llorens
- National Reference Center for TSE, Georg-August University, Göttingen, 37073, Germany; Biomedical Research Networking Center on Neurodegenerative Diseases (CIBERNED), L'Hospitalet de Llobregat, 08908, Barcelona, Spain
| | - Inga Zerr
- National Reference Center for TSE, Georg-August University, Göttingen, 37073, Germany
| | - Sabina Capellari
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, 40139, Italy; Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, 40123, Italy
| | - Piero Parchi
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, 40139, Italy; Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, 40138, Italy
| | - Stuart L Schreiber
- Chemical Biology and Therapeutics Science Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142; Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Steven A Carr
- Proteomics Platform, Broad Institute of MIT and Harvard, Cambridge, MA 02142.
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6
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Abstract
The cellular prion protein, PrPC, is a small, cell surface glycoprotein with a function that is currently somewhat ill defined. It is also the key molecule involved in the family of neurodegenerative disorders called transmissible spongiform encephalopathies, which are also known as prion diseases. The misfolding of PrPC to a conformationally altered isoform, designated PrPTSE, is the main molecular process involved in pathogenesis and appears to precede many other pathologic and clinical manifestations of disease, including neuronal loss, astrogliosis, and cognitive loss. PrPTSE is also believed to be the major component of the infectious "prion," the agent responsible for disease transmission, and preparations of this protein can cause prion disease when inoculated into a naïve host. Thus, understanding the biochemical and biophysical properties of both PrPC and PrPTSE, and ultimately the mechanisms of their interconversion, is critical if we are to understand prion disease biology. Although entire books could be devoted to research pertaining to the protein, herein we briefly review the state of knowledge of prion biochemistry, including consideration of prion protein structure, function, misfolding, and dysfunction.
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Affiliation(s)
- Andrew C Gill
- School of Chemistry, Joseph Banks Laboratories, University of Lincoln, Lincoln, United Kingdom; Division of Neurobiology, The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, United Kingdom.
| | - Andrew R Castle
- Division of Neurobiology, The Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, United Kingdom
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Inhibition of IL-1β Signaling Normalizes NMDA-Dependent Neurotransmission and Reduces Seizure Susceptibility in a Mouse Model of Creutzfeldt-Jakob Disease. J Neurosci 2017; 37:10278-10289. [PMID: 28924012 DOI: 10.1523/jneurosci.1301-17.2017] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 07/31/2017] [Accepted: 08/23/2017] [Indexed: 11/21/2022] Open
Abstract
Creutzfeldt-Jakob disease (CJD) is a neurodegenerative disorder caused by prion protein (PrP) misfolding, clinically recognized by cognitive and motor deficits, electroencephalographic abnormalities, and seizures. Its neurophysiological bases are not known. To assess the potential involvement of NMDA receptor (NMDAR) dysfunction, we analyzed NMDA-dependent synaptic plasticity in hippocampal slices from Tg(CJD) mice, which model a genetic form of CJD. Because PrP depletion may result in functional upregulation of NMDARs, we also analyzed PrP knock-out (KO) mice. Long-term potentiation (LTP) at the Schaffer collateral-commissural synapses in the CA1 area of ∼100-d-old Tg(CJD) mice was comparable to that of wild-type (WT) controls, but there was an inversion of metaplasticity, with increased GluN2B phosphorylation, which is indicative of enhanced NMDAR activation. Similar but less marked changes were seen in PrP KO mice. At ∼300 d of age, the magnitude of LTP increased in Tg(CJD) mice but decreased in PrP KO mice, indicating divergent changes in hippocampal synaptic responsiveness. Tg(CJD) but not PrP KO mice were intrinsically more susceptible than WT controls to focal hippocampal seizures induced by kainic acid. IL-1β-positive astrocytes increased in the Tg(CJD) hippocampus, and blocking IL-1 receptor signaling restored normal synaptic responses and reduced seizure susceptibility. These results indicate that alterations in NMDA-dependent glutamatergic transmission in Tg(CJD) mice do not depend solely on PrP functional loss. Moreover, astrocytic IL-1β plays a role in the enhanced synaptic responsiveness and seizure susceptibility, suggesting that targeting IL-1β signaling may offer a novel symptomatic treatment for CJD.SIGNIFICANCE STATEMENT Dementia and myoclonic jerks develop in individuals with Creutzfeldt-Jakob disease (CJD), an incurable brain disorder caused by alterations in prion protein structure. These individuals are prone to seizures and have high brain levels of the inflammatory cytokine IL-1β. Here we show that blocking IL-1β receptors with anakinra, the human recombinant form of the endogenous IL-1 receptor antagonist used to treat rheumatoid arthritis, normalizes hippocampal neurotransmission and reduces seizure susceptibility in a CJD mouse model. These results link neuroinflammation to defective neurotransmission and the enhanced susceptibility to seizures in CJD and raise the possibility that targeting IL-1β with clinically available drugs may be beneficial for symptomatic treatment of the disease.
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8
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Abstract
The misfolding of the cellular prion protein (PrPC) causes fatal neurodegenerative diseases. Yet PrPC is highly conserved in mammals, suggesting that it exerts beneficial functions preventing its evolutionary elimination. Ablation of PrPC in mice results in well-defined structural and functional alterations in the peripheral nervous system. Many additional phenotypes were ascribed to the lack of PrPC, but some of these were found to arise from genetic artifacts of the underlying mouse models. Here, we revisit the proposed physiological roles of PrPC in the central and peripheral nervous systems and highlight the need for their critical reassessment using new, rigorously controlled animal models.
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Affiliation(s)
- Marie-Angela Wulf
- Institute of Neuropathology, University of Zurich, Rämistrasse 100, CH-8091, Zürich, Switzerland
| | - Assunta Senatore
- Institute of Neuropathology, University of Zurich, Rämistrasse 100, CH-8091, Zürich, Switzerland
| | - Adriano Aguzzi
- Institute of Neuropathology, University of Zurich, Rämistrasse 100, CH-8091, Zürich, Switzerland.
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9
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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: 128] [Impact Index Per Article: 18.3] [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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10
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Abstract
Since its discovery the cellular prion protein (encoded by the Prnp gene) has been associated with a large number of functions. The proposed functions rank from basic cellular processes such as cell cycle and survival to neural functions such as behavior and neuroprotection, following a pattern similar to that of Moore's law for electronics. In addition, particular interest is increasing in the participation of Prnp in neurodegeneration. However, in recent years a redefinition of these functions has begun, since examples of previously attributed functions were increasingly re-associated with other proteins. Most of these functions are linked to so-called "Prnp-flanking genes" that are close to the genomic locus of Prnp and which are present in the genome of some Prnp mouse models. In addition, their role in neuroprotection against convulsive insults has been confirmed in recent studies. Lastly, in recent years a large number of models indicating the participation of different domains of the protein in apoptosis have been uncovered. However, after more than 10 years of molecular dissection our view is that the simplest mechanistic model in PrP(C)-mediated cell death should be considered, as Ockham's razor theory suggested.
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Affiliation(s)
- José A del Río
- a Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC) , Parc Científic de Barcelona, Barcelona , Spain.,b Department of Cell Biology, Physiology and Inmunology , Facultat de Biologia, Universitat de Barcelona , Barcelona , Spain.,c Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Barcelona , Spain
| | - Rosalina Gavín
- a Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia (IBEC) , Parc Científic de Barcelona, Barcelona , Spain.,b Department of Cell Biology, Physiology and Inmunology , Facultat de Biologia, Universitat de Barcelona , Barcelona , Spain.,c Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED) , Barcelona , Spain
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11
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Mehrabian M, Hildebrandt H, Schmitt-Ulms G. NCAM1 Polysialylation: The Prion Protein's Elusive Reason for Being? ASN Neuro 2016; 8:8/6/1759091416679074. [PMID: 27879349 PMCID: PMC5122176 DOI: 10.1177/1759091416679074] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 09/08/2016] [Accepted: 10/02/2016] [Indexed: 01/06/2023] Open
Abstract
Much confusion surrounds the physiological function of the cellular prion protein (PrPC). It is, however, anticipated that knowledge of its function will shed light on its contribution to neurodegenerative diseases and suggest ways to interfere with the cellular toxicity central to them. Consequently, efforts to elucidate its function have been all but exhaustive. Building on earlier work that uncovered the evolutionary descent of the prion founder gene from an ancestral ZIP zinc transporter, we recently investigated a possible role of PrPC in a morphogenetic program referred to as epithelial-to-mesenchymal transition (EMT). By capitalizing on PrPC knockout cell clones in a mammalian cell model of EMT and using a comparative proteomics discovery strategy, neural cell adhesion molecule-1 emerged as a protein whose upregulation during EMT was perturbed in PrPC knockout cells. Follow-up work led us to observe that PrPC regulates the polysialylation of the neural cell adhesion molecule NCAM1 in cells undergoing morphogenetic reprogramming. In addition to governing cellular migration, polysialylation modulates several other cellular plasticity programs PrPC has been phenotypically linked to. These include neurogenesis in the subventricular zone, controlled mossy fiber sprouting and trimming in the hippocampal formation, hematopoietic stem cell renewal, myelin repair and maintenance, integrity of the circadian rhythm, and glutamatergic signaling. This review revisits this body of literature and attempts to present it in light of this novel contextual framework. When approached in this manner, a coherent model of PrPC acting as a regulator of polysialylation during specific cell and tissue morphogenesis events comes into focus.
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Affiliation(s)
- Mohadeseh Mehrabian
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Hildebrandt
- Institute for Cellular Chemistry, Hannover Medical School, Hannover, Germany
| | - Gerold Schmitt-Ulms
- Tanz Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, Canada .,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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12
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Genetic background modulates outcome of therapeutic amyloid peptides in treatment of neuroinflammation. J Neuroimmunol 2016; 298:42-50. [PMID: 27609274 DOI: 10.1016/j.jneuroim.2016.06.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 05/27/2016] [Accepted: 06/22/2016] [Indexed: 12/17/2022]
Abstract
Amyloid hexapeptide molecules are effective in the treatment of the murine model of neuroinflammation, known as experimental autoimmune encephalomyelitis (EAE). Efficacy however differs between two inbred mouse strains, C57BL/6J (B6) and C57BL/10SnJ (B10). Amyloid hexapeptide treatments improved the clinical outcomes of B6, but not B10 mice, indicating that genetic background influences therapeutic efficacy. Moreover, although previous studies indicated that prion protein deficiency results in more severe EAE in B6 mice, we observed no such effect in B10 mice. In addition, we found that amyloid hexapeptide treatments of B10 and B6 mice elicited differential IL4 responses. Thus, the modulatory potential of prion protein and related treatments with other amyloid hexapeptides in EAE depends on mouse strain.
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13
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Nuvolone M, Hermann M, Sorce S, Russo G, Tiberi C, Schwarz P, Minikel E, Sanoudou D, Pelczar P, Aguzzi A. Strictly co-isogenic C57BL/6J-Prnp-/- mice: A rigorous resource for prion science. J Exp Med 2016; 213:313-27. [PMID: 26926995 PMCID: PMC4813672 DOI: 10.1084/jem.20151610] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 01/25/2016] [Indexed: 12/18/2022] Open
Abstract
Although its involvement in prion replication and neurotoxicity during transmissible spongiform encephalopathies is undisputed, the physiological role of the cellular prion protein (PrP(C)) remains enigmatic. A plethora of functions have been ascribed to PrP(C) based on phenotypes of Prnp(-/-) mice. However, all currently available Prnp(-/-) lines were generated in embryonic stem cells from the 129 strain of the laboratory mouse and mostly crossed to non-129 strains. Therefore, Prnp-linked loci polymorphic between 129 and the backcrossing strain resulted in systematic genetic confounders and led to erroneous conclusions. We used TALEN-mediated genome editing in fertilized mouse oocytes to create the Zurich-3 (ZH3) Prnp-ablated allele on a pure C57BL/6J genetic background. Genomic, transcriptional, and phenotypic characterization of Prnp(ZH3/ZH3) mice failed to identify phenotypes previously described in non-co-isogenic Prnp(-/-) mice. However, aged Prnp(ZH3/ZH3) mice developed a chronic demyelinating peripheral neuropathy, confirming the crucial involvement of PrP(C) in peripheral myelin maintenance. This new line represents a rigorous genetic resource for studying the role of PrP(C) in physiology and disease.
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Affiliation(s)
- Mario Nuvolone
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland
| | - Mario Hermann
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland Institute of Laboratory Animal Science, University of Zurich, 8091 Zurich, Switzerland
| | - Silvia Sorce
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland
| | - Giancarlo Russo
- Functional Genomics Center Zurich (FGCZ), 8057 Zurich, Switzerland
| | - Cinzia Tiberi
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland
| | - Petra Schwarz
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland
| | - Eric Minikel
- Prion Alliance, Cambridge, MA 02139 Broad Institute, Cambridge, MA 02142 Analytical and Translational Genetics Unit, Massachusetts General Hospital, Boston, MA 02114
| | - Despina Sanoudou
- Fourth Department of Internal Medicine, Attikon Hospital, Medical School, University of Athens, 115 27 Athens, Greece
| | - Pawel Pelczar
- Institute of Laboratory Animal Science, University of Zurich, 8091 Zurich, Switzerland
| | - Adriano Aguzzi
- Institute of Neuropathology, University Hospital of Zurich, 8091 Zurich, Switzerland
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Abstract
Aggregation of misfolded host proteins in the central nervous system is believed to be important in the pathogenic process in several neurodegenerative diseases of humans, including prion diseases, Alzheimer’s disease, and Parkinson’s disease. In these diseases, protein misfolding and aggregation appear to expand through a process of seeded polymerization. Prion diseases occur in both humans and animals and are experimentally transmissible orally or by injection, thus providing a controllable model of other neurodegenerative protein misfolding diseases. In rodents and ruminants, prion disease has a slow course, lasting months to years. Although prion infectivity has been detected in brain tissue at 3 to 4 weeks postinfection (p.i.), the details of early prion replication in the brain are not well understood. Here we studied the localization and quantitation of PrPSc generation in vivo starting at 30 min postmicroinjection of scrapie into the brain. In C57BL mice at 3 days p.i., generation of new PrPSc was detected by immunohistochemistry and immunoblot assays, and at 7 days p.i., new generation was confirmed by real-time quaking-induced conversion assay. The main site of new PrPSc generation was near the outer basement membrane of small and medium blood vessels. The finding and localization of replication at this site so early after injection have not been reported previously. This predominantly perivascular location suggested that structural components of the blood vessel basement membrane or perivascular astrocytes might act as cofactors in the initial generation of PrPSc. The location of PrPSc replication at the basement membrane also implies a role for the brain interstitial fluid drainage in the early infection process. Neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and prion diseases, of humans are characterized by misfolding and aggregation of certain proteins, resulting in the destruction of brain tissue. In these diseases, the damage process spreads progressively within the central nervous system, but only prion diseases are known to be transmissible between individuals. Here we used microinjection of infectious prion protein (PrPSc) into the mouse brain to model early events of iatrogenic prion transmission via surgical instruments or tissue grafts. At 3 and 7 days postinjection, we detected the generation of new PrPSc, mostly on the outer walls of blood vessels near the injection site. This location and very early replication were surprising and unique. Perivascular prion replication suggested the transport of injected PrPSc via brain interstitial fluid to the basement membranes of blood vessels, where interactions with possible cofactors made by astrocytes or endothelia might facilitate the earliest cycles of prion infection.
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Carulla P, Llorens F, Matamoros-Angles A, Aguilar-Calvo P, Espinosa JC, Gavín R, Ferrer I, Legname G, Torres JM, del Río JA. Involvement of PrP(C) in kainate-induced excitotoxicity in several mouse strains. Sci Rep 2015; 5:11971. [PMID: 26155834 PMCID: PMC4648388 DOI: 10.1038/srep11971] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 06/12/2015] [Indexed: 01/14/2023] Open
Abstract
The cellular prion protein (PrP(C)) has been associated with a plethora of cellular functions ranging from cell cycle to neuroprotection. Mice lacking PrP(C) show an increased susceptibility to epileptic seizures; the protein, then, is neuroprotective. However, lack of experimental reproducibility has led to considering the possibility that other factors besides PrP(C) deletion, such as the genetic background of mice or the presence of so-called "Prnp flanking genes", might contribute to the reported susceptibility. Here, we performed a comparative analysis of seizure-susceptibility using characterized Prnp(+/+) and Prnp(0/0) mice of B6129, B6.129, 129/Ola or FVB/N genetic backgrounds. Our study indicates that PrP(C) plays a role in neuroprotection in KA-treated cells and mice. For this function, PrP(C) should contain the aa32-93 region and needs to be linked to the membrane. In addition, some unidentified "Prnp-flanking genes" play a role parallel to PrP(C) in the KA-mediated responses in B6129 and B6.129 Prnp(0/0) mice.
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Affiliation(s)
- Patricia Carulla
- 1] Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain [2] Department of Cell Biology, Universitat de Barcelona, Barcelona, Spain [3] Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain
| | - Franc Llorens
- 1] Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain [2] Department of Cell Biology, Universitat de Barcelona, Barcelona, Spain [3] Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain [4] German Center for Neurodegenerative Diseases (DZNE), Robert-Koch Str. 40, 37075, Göttingen, Germany
| | - Andreu Matamoros-Angles
- 1] Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain [2] Department of Cell Biology, Universitat de Barcelona, Barcelona, Spain [3] Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain
| | | | - Juan Carlos Espinosa
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain
| | - Rosalina Gavín
- 1] Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain [2] Department of Cell Biology, Universitat de Barcelona, Barcelona, Spain [3] Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain
| | - Isidre Ferrer
- 1] Institut de Neuropatologia, IDIBELL-Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain [2] Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain
| | - Giuseppe Legname
- Laboratory of Prion Biology, Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy
| | - Juan Maria Torres
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain
| | - José A del Río
- 1] Molecular and Cellular Neurobiotechnology, Institute of Bioengineering of Catalonia (IBEC), Parc Científic de Barcelona, Barcelona, Spain [2] Department of Cell Biology, Universitat de Barcelona, Barcelona, Spain [3] Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Barcelona, Spain
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Race B, Phillips K, Meade-White K, Striebel J, Chesebro B. Increased infectivity of anchorless mouse scrapie prions in transgenic mice overexpressing human prion protein. J Virol 2015; 89:6022-32. [PMID: 25810548 PMCID: PMC4442444 DOI: 10.1128/jvi.00362-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 03/18/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Prion protein (PrP) is found in all mammals, mostly as a glycoprotein anchored to the plasma membrane by a C-terminal glycosylphosphatidylinositol (GPI) linkage. Following prion infection, host protease-sensitive prion protein (PrPsen or PrPC) is converted into an abnormal, disease-associated, protease-resistant form (PrPres). Biochemical characteristics, such as the PrP amino acid sequence, and posttranslational modifications, such as glycosylation and GPI anchoring, can affect the transmissibility of prions as well as the biochemical properties of the PrPres generated. Previous in vivo studies on the effects of GPI anchoring on prion infectivity have not examined cross-species transmission. In this study, we tested the effect of lack of GPI anchoring on a species barrier model using mice expressing human PrP. In this model, anchorless 22L prions derived from tg44 mice were more infectious than 22L prions derived from C57BL/10 mice when tested in tg66 transgenic mice, which expressed wild-type anchored human PrP at 8- to 16-fold above normal. Thus, the lack of the GPI anchor on the PrPres from tg44 mice appeared to reduce the effect of the mouse-human PrP species barrier. In contrast, neither source of prions induced disease in tgRM transgenic mice, which expressed human PrP at 2- to 4-fold above normal. IMPORTANCE Prion protein (PrP) is found in all mammals, usually attached to cells by an anchor molecule called GPI. Following prion infection, PrP is converted into a disease-associated form (PrPres). While most prion diseases are species specific, this finding is not consistent, and species barriers differ in strength. The amino acid sequence of PrP varies among species, and this variability affects prion species barriers. However, other PrP modifications, including glycosylation and GPI anchoring, may also influence cross-species infectivity. We studied the effect of PrP GPI anchoring using a mouse-to-human species barrier model. Experiments showed that prions produced by mice expressing only anchorless PrP were more infectious than prions produced in mice expressing anchored PrP. Thus, the lack of the GPI anchor on prions reduced the effect of the mouse-human species barrier. Our results suggest that prion diseases that produce higher levels of anchorless PrP may pose an increased risk for cross-species infection.
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Affiliation(s)
- Brent Race
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Katie Phillips
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Kimberly Meade-White
- Rocky Mountain Veterinary Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - James Striebel
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Bruce Chesebro
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
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17
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Makzhami S, Passet B, Halliez S, Castille J, Moazami-Goudarzi K, Duchesne A, Vilotte M, Laude H, Mouillet-Richard S, Béringue V, Vaiman D, Vilotte JL. The prion protein family: a view from the placenta. Front Cell Dev Biol 2014; 2:35. [PMID: 25364742 PMCID: PMC4207016 DOI: 10.3389/fcell.2014.00035] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 07/22/2014] [Indexed: 02/01/2023] Open
Abstract
Based on its developmental pattern of expression, early studies suggested the implication of the mammalian Prion protein PrP, a glycosylphosphatidylinositol-anchored ubiquitously expressed and evolutionary conserved glycoprotein encoded by the Prnp gene, in early embryogenesis. However, gene invalidation in several species did not result in obvious developmental abnormalities and it was only recently that it was associated in mice with intra-uterine growth retardation and placental dysfunction. A proposed explanation for this lack of easily detectable developmental-related phenotype is the existence in the genome of one or more gene (s) able to compensate for the absence of PrP. Indeed, two other members of the Prnp gene family have been recently described, Doppel and Shadoo, and the consequences of their invalidation alongside that of PrP tested in mice. No embryonic defect was observed in mice depleted for Doppel and PrP. Interestingly, the co-invalidation of PrP and Shadoo in two independent studies led to apparently conflicting observations, with no apparent consequences in one report and the observation of a developmental defect of the ectoplacental cone that leads to early embryonic lethality in the other. This short review aims at summarizing these recent, apparently conflicting data highlighting the related biological questions and associated implications in terms of animal and human health.
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Affiliation(s)
- Samira Makzhami
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
| | - Bruno Passet
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
| | - Sophie Halliez
- INRA, U892 Virologie et Immunologie Moléculaires Jouy-en-Josas, France
| | - Johan Castille
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
| | | | - Amandine Duchesne
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
| | - Marthe Vilotte
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
| | - Hubert Laude
- INRA, U892 Virologie et Immunologie Moléculaires Jouy-en-Josas, France
| | - Sophie Mouillet-Richard
- INSERM, UMR-S1124 Signalisation et Physiopathologie Neurologique, Université Paris Descartes Paris, France
| | - Vincent Béringue
- INRA, U892 Virologie et Immunologie Moléculaires Jouy-en-Josas, France
| | - Daniel Vaiman
- Faculté Paris Descartes, UMR8104 CNRS, U1016 INSERM, Institut Cochin Paris, France
| | - Jean-Luc Vilotte
- INRA, UMR1313 Génétique Animale et Biologie Intégrative Jouy-en-Josas, France
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Nuvolone M, Kana V, Hutter G, Sakata D, Mortin-Toth SM, Russo G, Danska JS, Aguzzi A. SIRPα polymorphisms, but not the prion protein, control phagocytosis of apoptotic cells. ACTA ACUST UNITED AC 2013; 210:2539-52. [PMID: 24145514 PMCID: PMC3832919 DOI: 10.1084/jem.20131274] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Prnp(-/-) mice lack the prion protein PrP(C) and are resistant to prion infections, but variable phenotypes have been reported in Prnp(-/-) mice and the physiological function of PrP(C) remains poorly understood. Here we examined a cell-autonomous phenotype, inhibition of macrophage phagocytosis of apoptotic cells, previously reported in Prnp(-/-) mice. Using formal genetic, genomic, and immunological analyses, we found that the regulation of phagocytosis previously ascribed to PrP(C) is instead controlled by a linked locus encoding the signal regulatory protein α (Sirpa). These findings indicate that control of phagocytosis was previously misattributed to the prion protein and illustrate the requirement for stringent approaches to eliminate confounding effects of flanking genes in studies modeling human disease in gene-targeted mice. The plethora of seemingly unrelated functions attributed to PrP(C) suggests that additional phenotypes reported in Prnp(-/-) mice may actually relate to Sirpa or other genetic confounders.
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Affiliation(s)
- Mario Nuvolone
- Institute of Neuropathology, University Hospital of Zurich, CH-8091 Zurich, Switzerland
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Striebel JF, Race B, Chesebro B. Prion protein and susceptibility to kainate-induced seizures: genetic pitfalls in the use of PrP knockout mice. Prion 2013; 7:280-5. [PMID: 23851597 PMCID: PMC3904312 DOI: 10.4161/pri.25738] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Prion protein (PrP) is a cell surface glycoprotein which is required for susceptibility to prion infection and disease. However, PrP is expressed in many different cell types located in numerous organs. Therefore, in addition to its role in prion diseases, PrP may have a large variety of other biological functions involving the nervous system and other systems. We recently showed that susceptibility to kainate-induced seizures differed in Prnp−/− and Prnp+/+ mice on the C57BL/10SnJ background. However, in a genetic complementation experiment a PrP expressing transgene was not able to rescue the Prnp+/+ phenotype. Thus the apparent effect of PrP on seizures was actually due to genes flanking the Prnp−/− gene rather that the Prnp deletion itself. We discuss here several pitfalls in the use of Prnp−/− genotypes expressed in various mouse genetic backgrounds to determine the functions of PrP. In particular, the use of Prnp−/− mice with heterogeneous mixed genetic backgrounds may have weakened the conclusions of many previous experiments. Use of either co-isogenic mice or congenic mice with more homogeneous genetic backgrounds is now feasible. For congenic mice, the potential problem of flanking genes can be mitigated by the use of appropriate transgene rescue experiments to confirm the conclusions.
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Affiliation(s)
- James F Striebel
- Laboratory of Persistent Viral Diseases; Rocky Mountain Laboratories; National Institute of Allergy and Infectious Diseases; Hamilton, MO USA
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