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Kovacs GG, Budka H. Molecular pathology of human prion diseases. Int J Mol Sci 2009; 10:976-99. [PMID: 19399233 PMCID: PMC2672014 DOI: 10.3390/ijms10030976] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 02/27/2009] [Accepted: 03/04/2009] [Indexed: 12/18/2022] Open
Abstract
Prion diseases are fatal neurodegenerative conditions in humans and animals. In this review, we summarize the molecular background of phenotypic variability, relation of prion protein (PrP) to other proteins associated with neurodegenerative diseases, and pathogenesis of neuronal vulnerability. PrP exists in different forms that may be present in both diseased and non-diseased brain, however, abundant disease-associated PrP together with tissue pathology characterizes prion diseases and associates with transmissibility. Prion diseases have different etiological background with distinct pathogenesis and phenotype. Mutations of the prion protein gene are associated with genetic forms. The codon 129 polymorphism in combination with the Western blot pattern of PrP after proteinase K digestion serves as a basis for molecular subtyping of sporadic Creutzfeldt-Jakob disease. Tissue damage may result from several parallel, interacting or subsequent pathways that involve cellular systems associated with synapses, protein processing, oxidative stress, autophagy, and apoptosis.
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Affiliation(s)
| | - Herbert Budka
- Author to whom correspondence should be addressed; E-Mail:
; Tel. +43-1-40400-5500; Fax: +43-1-40400-5511
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352
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Abstract
The hallmark of transmissible spongiform encephalopathies (TSEs or prion diseases) is the accumulation of an abnormally folded, partially protease-resistant form (PrP-res) of the normal protease-sensitive prion protein (PrP-sen). PrP-sen is attached to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. In vitro, the anchor and the local membrane environment are important for the conversion of PrP-sen to PrP-res. In vivo, however, the anchor is not necessary because transgenic mice expressing anchorless PrP-sen accumulate PrP-res and replicate infectivity. To clarify the role of the GPI anchor in TSE infection, cells expressing GPI-anchored PrP-sen, anchorless PrP-sen, or both forms of PrP-sen were exposed to the mouse scrapie strain 22L. Cells expressing anchored PrP-sen produced PrP-res after exposure to 22L. Surprisingly, while cells expressing anchorless PrP-sen made anchorless PrP-res in the first 96 h postinfection, no PrP-res was detected at later passes. In contrast, when cells expressing both forms of PrP-sen were exposed to 22L, both anchored and anchorless PrP-res were detected over multiple passes. Consistent with the in vitro data, scrapie-infected cells expressing anchored PrP-sen transmitted disease to mice whereas cells expressing anchorless PrP-sen alone did not. These results demonstrate that the GPI anchor on PrP-sen is important for the persistent infection of cells in vitro. Our data suggest that cells expressing anchorless PrP-sen are not directly infected with scrapie. Thus, PrP-res formation in transgenic mice expressing anchorless PrP-sen may be occurring extracellularly.
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353
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Singh A, Mohan ML, Isaac AO, Luo X, Petrak J, Vyoral D, Singh N. Prion protein modulates cellular iron uptake: a novel function with implications for prion disease pathogenesis. PLoS One 2009; 4:e4468. [PMID: 19212444 PMCID: PMC2637434 DOI: 10.1371/journal.pone.0004468] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 12/26/2008] [Indexed: 01/18/2023] Open
Abstract
Converging evidence leaves little doubt that a change in the conformation of prion protein (PrPC) from a mainly α-helical to a β-sheet rich PrP-scrapie (PrPSc) form is the main event responsible for prion disease associated neurotoxicity. However, neither the mechanism of toxicity by PrPSc, nor the normal function of PrPC is entirely clear. Recent reports suggest that imbalance of iron homeostasis is a common feature of prion infected cells and mouse models, implicating redox-iron in prion disease pathogenesis. In this report, we provide evidence that PrPC mediates cellular iron uptake and transport, and mutant PrP forms alter cellular iron levels differentially. Using human neuroblastoma cells as models, we demonstrate that over-expression of PrPC increases intra-cellular iron relative to non-transfected controls as indicated by an increase in total cellular iron, the cellular labile iron pool (LIP), and iron content of ferritin. As a result, the levels of iron uptake proteins transferrin (Tf) and transferrin receptor (TfR) are decreased, and expression of iron storage protein ferritin is increased. The positive effect of PrPC on ferritin iron content is enhanced by stimulating PrPC endocytosis, and reversed by cross-linking PrPC on the plasma membrane. Expression of mutant PrP forms lacking the octapeptide-repeats, the membrane anchor, or carrying the pathogenic mutation PrP102L decreases ferritin iron content significantly relative to PrPC expressing cells, but the effect on cellular LIP and levels of Tf, TfR, and ferritin is complex, varying with the mutation. Neither PrPC nor the mutant PrP forms influence the rate or amount of iron released into the medium, suggesting a functional role for PrPC in cellular iron uptake and transport to ferritin, and dysfunction of PrPC as a significant contributing factor of brain iron imbalance in prion disorders.
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Affiliation(s)
- Ajay Singh
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Maradumane L. Mohan
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Alfred Orina Isaac
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Xiu Luo
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jiri Petrak
- Department of Pathological Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
| | - Daniel Vyoral
- Department of Pathological Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
| | - Neena Singh
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail: .
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354
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Aggregated, wild-type prion protein causes neurological dysfunction and synaptic abnormalities. J Neurosci 2009; 28:13258-67. [PMID: 19052217 DOI: 10.1523/jneurosci.3109-08.2008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The neurotoxic forms of the prion protein (PrP) that cause neurodegeneration in prion diseases remain to be conclusively identified. Considerable evidence points to the importance of noninfectious oligomers of PrP in the pathogenic process. In this study, we describe lines of Tg(WT) transgenic mice that over-express wild-type PrP by either approximately 5-fold or approximately 10-fold (depending on whether the transgene array is, respectively, hemizygous or homozygous). Homozygous but not hemizygous Tg(WT) mice develop a spontaneous neurodegenerative illness characterized clinically by tremor and paresis. Both kinds of mice accumulate large numbers of punctate PrP deposits in the molecular layer of the cerebellum as well as in several other brain regions, and they display abnormally enlarged synaptic terminals accompanied by a dramatic proliferation of membranous structures. The over-expressed PrP in Tg(WT) mice assembles into an insoluble form that is mildly protease-resistant and is recognizable by aggregation-specific antibodies, but that is not infectious in transmission experiments. Together, our results demonstrate that noninfectious aggregates of wild-type PrP are neurotoxic, particularly to synapses, and they suggest common pathogenic mechanisms shared by prion diseases and nontransmissible neurodegenerative disorders associated with protein misfolding.
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355
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356
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Race B, Meade-White K, Oldstone MBA, Race R, Chesebro B. Detection of prion infectivity in fat tissues of scrapie-infected mice. PLoS Pathog 2008; 4:e1000232. [PMID: 19057664 PMCID: PMC2585054 DOI: 10.1371/journal.ppat.1000232] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 11/05/2008] [Indexed: 02/04/2023] Open
Abstract
Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. Transmission of prion disease from cattle to humans resulted in banning human consumption of ruminant nervous system and certain other tissues. In the present study, we surveyed tissue distribution of prion infectivity in mice with prion disease. We show for the first time detection of infectivity in white and brown fat. Since high amounts of ruminant fat are consumed by humans and also incorporated into animal feed, fat-containing tissues may pose a previously unappreciated hazard for spread of prion infection. Prion diseases, also known as transmissible spongiform encephalopathies, are infectious progressive fatal neurodegenerative diseases which affect humans as well as wild and domestic animals. Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. We show for the first time the presence of prion infectivity in white fat and brown fat tissues of mice with prion disease. Our results suggest that fat tissues of domestic or wild animals infected with prions may pose an unappreciated hazard for spread of infection to humans or domestic animals. The presence of prion infectivity in fat suggests that additional consideration may be required to eliminate from the food chain any fat from ruminants suspected of exposure to or infection with prions. Thus, this finding has implications for public health, food safety, and prion disease prevention strategies.
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Affiliation(s)
- Brent Race
- Laboratory of Persistent Virus Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Kimberly Meade-White
- Laboratory of Persistent Virus Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Michael B. A. Oldstone
- Department of Immunology and Microbial Science, The Scripps Research Institute, LaJolla, California, United States of America
| | - Richard Race
- Laboratory of Persistent Virus Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Bruce Chesebro
- Laboratory of Persistent Virus Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
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357
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Christensen HM, Harris DA. A deleted prion protein that is neurotoxic in vivo is localized normally in cultured cells. J Neurochem 2008; 108:44-56. [PMID: 19046329 DOI: 10.1111/j.1471-4159.2008.05719.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The prion protein (PrP) possesses sequence-specific domains that endow the molecule with neuroprotective and neurotoxic activities, and that may contribute to the pathogenesis of prion diseases. To further define critical neurotoxic determinants within PrP, we previously generated Tg(DeltaCR) mice that express a form of PrP harboring a deletion of 21 amino acids within the central domain of the protein [Li et al., EMBO J. 26 (2007), 548]. These animals exhibit a neonatal lethal phenotype that is dose-dependently rescued by co-expression of wild-type PrP. In this study, we examined the localization and cell biological properties of the PrP(DeltaCR) protein in cultured cells to further understand the mechanism of PrP(DeltaCR) neurotoxicity. We found that the distribution of PrP(DeltaCR) was identical to that of wild-type PrP in multiple cell lines of both neuronal and non-neuronal origin, and that co-expression of the two proteins did not alter the localization of either one. Both proteins were found in lipid rafts, and both were localized to the apical surface in polarized epithelial cells. Taken together, our results suggest that PrP(DeltaCR) toxicity is not a result of mislocalization or aggregation of the protein, and more likely stems from altered binding interactions leading to the activation of deleterious signaling pathways.
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Affiliation(s)
- Heather M Christensen
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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358
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Cobb NJ, Apetri AC, Surewicz WK. Prion protein amyloid formation under native-like conditions involves refolding of the C-terminal alpha-helical domain. J Biol Chem 2008; 283:34704-11. [PMID: 18930924 DOI: 10.1074/jbc.m806701200] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Transmissible spongiform encephalopathies are associated with conformational conversion of the cellular prion protein, PrP(C), into a proteinase K-resistant, amyloid-like aggregate, PrP(Sc). Although the structure of PrP(Sc) remains enigmatic, recent studies have afforded increasingly detailed characterization of recombinant PrP amyloid. However, all previous studies were performed using amyloid fibrils formed in the presence of denaturing agents that significantly alter the folding state(s) of the precursor monomer. Here we report that PrP amyloid can also be generated under physiologically relevant conditions, where the monomeric protein is natively folded. Remarkably, site-directed spin labeling studies reveal that these fibrils possess a beta-core structure nearly indistinguishable from that of amyloid grown under denaturing conditions, where the C-terminal alpha-helical domain of the PrP monomer undergoes major refolding to a parallel and in-register beta-structure upon conversion. The structural similarity of fibrils formed under drastically different conditions strongly suggests that the common beta-sheet architecture within the approximately 160-220 core region represents a distinct global minimum in the PrP conversion free energy landscape. We also show that the N-terminal region of fibrillar PrP displays conformational plasticity, undergoing a reversible structural transition with an apparent pK(a) of approximately 5.3. The C-terminal region, on the other hand, retains its beta-structure over the pH range 1-11, whereas more alkaline buffer conditions denature the fibrils into constituent PrP monomers. This profile of pH-dependent stability is reminiscent of the behavior of brain-derived PrP(Sc), suggesting a substantial degree of structural similarity within the beta-core region of these PrP aggregates.
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Affiliation(s)
- Nathan J Cobb
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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359
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Becker C, Liu X, Olschewski D, Castelli R, Seidel R, Seeberger P. Semisynthesis of a Glycosylphosphatidylinositol-Anchored Prion Protein. Angew Chem Int Ed Engl 2008; 47:8215-9. [DOI: 10.1002/anie.200802161] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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360
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Becker C, Liu X, Olschewski D, Castelli R, Seidel R, Seeberger P. Semisynthese eines Glycosylphosphatidylinositol-verankerten Prionproteins. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200802161] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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361
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Gilch S, Krammer C, Schätzl HM. Targeting prion proteins in neurodegenerative disease. Expert Opin Biol Ther 2008; 8:923-40. [PMID: 18549323 DOI: 10.1517/14712598.8.7.923] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Spongiform neurodegeneration is the pathological hallmark of individuals suffering from prion disease. These disorders, whose manifestation is sporadic, familial or acquired by infection, are caused by accumulation of the aberrantly folded isoform of the cellular prion protein (PrP(c)), termed PrP(Sc). Although usually rare, prion disorders are inevitably fatal and transferrable by infection. OBJECTIVE Pathology is restricted to the central nervous system and premortem diagnosis is usually not possible. Yet, promising approaches towards developing therapeutic regimens have been made recently. METHODS The biology of prion proteins and current models of neurotoxicity are discussed and prophylactic and therapeutic concepts are introduced. RESULTS/CONCLUSIONS Although various promising drug candidates with antiprion activity have been identified, this proof-of-concept cannot be transferred into translational medicine yet.
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Affiliation(s)
- Sabine Gilch
- Technische Universität München, Institute of Virology, Prion Research Group, Trogerstreet 30, 81675 Munich, Germany
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362
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Notari S, Strammiello R, Capellari S, Giese A, Cescatti M, Grassi J, Ghetti B, Langeveld JPM, Zou WQ, Gambetti P, Kretzschmar HA, Parchi P. Characterization of truncated forms of abnormal prion protein in Creutzfeldt-Jakob disease. J Biol Chem 2008; 283:30557-65. [PMID: 18753138 DOI: 10.1074/jbc.m801877200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In prion disease, the abnormal conformer of the cellular prion protein, PrP(Sc), deposits in fibrillar protein aggregates in brain and other organs. Limited exposure of PrP(Sc) to proteolytic digestion in vitro generates a core fragment of 19-21 kDa, named PrP27-30, which is also found in vivo. Recent evidence indicates that abnormal truncated fragments other than PrP27-30 may form in prion disease either in vivo or in vitro. We characterized a novel protease-resistant PrP fragment migrating 2-3 kDa faster than PrP27-30 in Creutzfeldt-Jakob disease (CJD) brains. The fragment has a size of about 18.5 kDa when associated with PrP27-30 type 1 (21 kDa) and of 17 kDa when associated with type 2 (19 kDa). Molecular mass and epitope mapping showed that the two fragments share the primary N-terminal sequence with PrP27-30 types 1 and 2, respectively, but lack a few amino acids at the very end of C terminus together with the glycosylphosphatidylinositol anchor. The amounts of the 18.5- or 17-kDa fragments and the previously described 13-kDa PrP(Sc) C-terminal fragment relatively to the PrP27-30 signal significantly differed among CJD subtypes. Furthermore, protease digestion of PrP(Sc) or PrP27-30 in partially denaturing conditions generated an additional truncated fragment of about 16 kDa only in typical sporadic CJD (i.e. MM1). These results show that the physicochemical heterogeneity of PrP(Sc) in CJD extends to abnormal truncated forms of the protein. The findings support the notion of distinct structural "conformers" of PrP(Sc) and indicate that the characterization of truncated PrP(Sc) forms may further improve molecular typing in CJD.
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Affiliation(s)
- Silvio Notari
- Dipartimento di Scienze Neurologiche, Università di Bologna, 40123 Bologna, Italy
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363
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Christensen HM, Harris DA. Prion protein lacks robust cytoprotective activity in cultured cells. Mol Neurodegener 2008; 3:11. [PMID: 18718018 PMCID: PMC2546390 DOI: 10.1186/1750-1326-3-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 08/21/2008] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The physiological function of the cellular prion protein (PrPC) remains unknown. However, PrPC has been reported to possess a cytoprotective activity that prevents death of neurons and other cells after a toxic stimulus. To explore this effect further, we attempted to reproduce several of the assays in which a protective activity of PrP had been previously demonstrated in mammalian cells. RESULTS In the first set of experiments, we found that PrP over-expression had a minimal effect on the death of MCF-7 breast carcinoma cells treated with TNF-alpha and Prn-p0/0 immortalized hippocampal neurons (HpL3-4 cells) subjected to serum deprivation. In the second set of assays, we observed only a small difference in viability between cerebellar granule neurons cultured from PrP-null and control mice in response to activation of endogenous or exogenous Bax. CONCLUSION Taken together, our results suggest either that cytoprotection is not a physiologically relevant activity of PrPC, or that PrPC-dependent protective pathways operative in vivo are not adequately modeled by these cell culture systems. We suggest that cell systems capable of mimicking the neurotoxic effects produced in transgenic mice by N-terminally deleted forms of PrP or Doppel may represent more useful tools for analyzing the cytoprotective function of PrPC.
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Affiliation(s)
- Heather M Christensen
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St, Louis, MO 63110, USA.
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364
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Rambold AS, Miesbauer M, Olschewski D, Seidel R, Riemer C, Smale L, Brumm L, Levy M, Gazit E, Oesterhelt D, Baier M, Becker CFW, Engelhard M, Winklhofer KF, Tatzelt J. Green tea extracts interfere with the stress-protective activity of PrP and the formation of PrP. J Neurochem 2008; 107:218-29. [PMID: 18691383 DOI: 10.1111/j.1471-4159.2008.05611.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A hallmark in prion diseases is the conformational transition of the cellular prion protein (PrP(C)) into a pathogenic conformation, designated scrapie prion protein (PrP(Sc)), which is the essential constituent of infectious prions. Here, we show that epigallocatechin gallate (EGCG) and gallocatechin gallate, the main polyphenols in green tea, induce the transition of mature PrP(C) into a detergent-insoluble conformation distinct from PrP(Sc). The PrP conformer induced by EGCG was rapidly internalized from the plasma membrane and degraded in lysosomal compartments. Isothermal titration calorimetry studies revealed that EGCG directly interacts with PrP leading to the destabilizing of the native conformation and the formation of random coil structures. This activity was dependent on the gallate side chain and the three hydroxyl groups of the trihydroxyphenyl side chain. In scrapie-infected cells EGCG treatment was beneficial; formation of PrP(Sc) ceased. However, in uninfected cells EGCG interfered with the stress-protective activity of PrP(C). As a consequence, EGCG-treated cells showed enhanced vulnerability to stress conditions. Our study emphasizes the important role of PrP(C) to protect cells from stress and indicate efficient intracellular pathways to degrade non-native conformations of PrP(C).
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Affiliation(s)
- Angelika S Rambold
- Department of Biochemistry, Neurobiochemistry, Ludwig-Maximilians-Universität München, München, Germany
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365
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Canello T, Engelstein R, Moshel O, Xanthopoulos K, Juanes ME, Langeveld J, Sklaviadis T, Gasset M, Gabizon R. Methionine sulfoxides on PrPSc: a prion-specific covalent signature. Biochemistry 2008; 47:8866-73. [PMID: 18680312 DOI: 10.1021/bi800801f] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Prion diseases are fatal neurodegenerative disorders believed to be transmitted by PrP (Sc), an aberrant form of the membrane protein PrP (C). In the absence of an established form-specific covalent difference, the infectious properties of PrP (Sc) were uniquely ascribed to the self-perpetuation properties of its aberrant fold. Previous sequencing of the PrP chain isolated from PrP(27-30) showed the oxidation of some methionine residues; however, at that time, these findings were ascribed to experimental limitations. Using the unique recognition properties of alphaPrP mAb IPC2, protein chemistry, and state of the art mass spectrometry, we now show that while a large fraction of the methionine residues in brain PrP (Sc) are present as methionine sulfoxides this modification could not be found on brain PrP (C) as well as on its recombinant models. In particular, the pattern of oxidation of M213 with respect to the glycosylation at N181 of PrP (Sc) differs both within and between species, adding another diversity factor to the structure of PrP (Sc) molecules. Our results pave the way for the production of prion-specific reagents in the form of antibodies against oxidized PrP chains which can serve in the development of both diagnostic and therapeutic strategies. In addition, we hypothesize that the accumulation of PrP (Sc) and thereafter the pathogenesis of prion disease may result from the poor degradation of oxidized aberrantly folded PrP.
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Affiliation(s)
- Tamar Canello
- Department of Neurology, The Agnes Ginges Center for Human Neurogenetics, Hadassah University Hospital, 91120 Jerusalem, Israel
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366
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Schubert T, Bärmann M, Rusp M, Gränzer W, Tanaka M. Diffusion of glycosylphosphatidylinositol (GPI)-anchored bovine prion protein (PrPc) in supported lipid membranes studied by single-molecule and complementary ensemble methods. J Memb Sci 2008. [DOI: 10.1016/j.memsci.2007.10.058] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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367
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Scrapie-induced defects in learning and memory of transgenic mice expressing anchorless prion protein are associated with alterations in the gamma aminobutyric acid-ergic pathway. J Virol 2008; 82:9890-9. [PMID: 18667494 DOI: 10.1128/jvi.00486-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
After infection with RML murine scrapie agent, transgenic (tg) mice expressing prion protein (PrP) without its glycophosphatidylinositol (GPI) membrane anchor (GPI(-/-) PrP tg mice) continue to make abundant amounts of the abnormally folded disease-associated PrPres but have a normal life span. In contrast, all age-, sex-, and genetically matched mice with a GPI-anchored PrP become moribund and die due to a chronic progressive neurodegenerative disease by 160 days after RML scrapie agent infection. We report here that infected GPI(-/-) PrP tg mice, although free from progressive neurodegenerative disease of the cerebellum and extrapyramidal and pyramidal systems, nevertheless suffer defects in learning and memory, long-term potentiation, and neuronal excitability. Such dysfunction increases over time and is associated with an increase in gamma aminobutyric acid (GABA) inhibition but not loss of excitatory glutamate/N-methyl-d-aspartic acid. Enhanced deposition of abnormally folded infectious PrP (PrPsc or PrPres) in the central nervous system (CNS) localizes with GABAA receptors. This occurs with minimal evidence of CNS spongiosis or apoptosis of neurons. The use of monoclonal antibodies reveals an association of PrPres with GABAA receptors. Thus, the clinical defects of learning and memory loss in vivo in GPI(-/-) PrP tg mice infected with scrapie agent may likely involve the GABAergic pathway.
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368
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Mouillet-Richard S, Nishida N, Pradines E, Laude H, Schneider B, Féraudet C, Grassi J, Launay JM, Lehmann S, Kellermann O. Prions impair bioaminergic functions through serotonin- or catecholamine-derived neurotoxins in neuronal cells. J Biol Chem 2008; 283:23782-90. [PMID: 18617522 DOI: 10.1074/jbc.m802433200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The conversion of the cellular prion protein, PrP(C), to an abnormal isoform, PrP(Sc), is a central event leading to neurodegeneration in prion diseases. Deciphering the molecular and cellular changes imparted by PrP(Sc) accumulation remains an arduous task due to the small number of cell lines supporting prion replication. Here we introduce the 1C11 cell line as a new in vitro model to investigate prion pathogenesis. This cell line is a committed neuroectodermal progenitor able to differentiate into fully functional serotonergic or catecholaminergic neurons. 1C11 cells, which naturally express PrP(C) from the undifferentiated state, can be chronically infected with various prion strains. Prion infection does not promote any noticeable phenotypic change in the progenitor cells nor prevent the onset of the serotonergic and catecholaminergic differentiation programs. Pathogenic prions, however, deviate the overall neurotransmitter-metabolism in both pathways by decreasing bioamine synthesis, storage, and transport, and enhancing catabolism. Noteworthy, oxidized derivatives of both serotonin and catecholamines are selectively detected in the differentiated progenies of infected cells and contribute to irreversible impairment in bioamine synthesis. Finally, the level of PrP(Sc) accumulation, that of infectivity, and the extent of all prion-induced changes in infected cells appear to be correlated. The report of such specific effects of infection on neuronal functions provides a foundation for dissecting the events underlying loss of neuronal homeostasis in prion diseases.
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Affiliation(s)
- Sophie Mouillet-Richard
- Différenciation Cellulaire et prions, CNRS FRE 2937, Institut Pasteur, INSERM U747, 7 rue Guy Môquet, Villejuif, France.
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369
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Affiliation(s)
- Adriano Aguzzi
- Institute of Neuropathology, University of Zurich, CH-8091 Zurich, Switzerland,
| | - Frank Baumann
- Institute of Neuropathology, University of Zurich, CH-8091 Zurich, Switzerland,
| | - Juliane Bremer
- Institute of Neuropathology, University of Zurich, CH-8091 Zurich, Switzerland,
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370
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Deriziotis P, Tabrizi SJ. Prions and the proteasome. Biochim Biophys Acta Mol Basis Dis 2008; 1782:713-22. [PMID: 18644436 DOI: 10.1016/j.bbadis.2008.06.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 06/23/2008] [Accepted: 06/24/2008] [Indexed: 10/21/2022]
Abstract
Prion diseases are fatal neurodegenerative disorders that include Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in animals. They are unique in terms of their biology because they are caused by the conformational re-arrangement of a normal host-encoded prion protein, PrPC, to an abnormal infectious isoform, PrPSc. Currently the precise mechanism behind prion-mediated neurodegeneration remains unclear. It is hypothesised than an unknown toxic gain of function of PrPSc, or an intermediate oligomeric form, underlies neuronal death. Increasing evidence suggests a role for the ubiquitin proteasome system (UPS) in prion disease. Both wild-type PrPC and disease-associated PrP isoforms accumulate in cells after proteasome inhibition leading to increased cell death, and abnormal beta-sheet-rich PrP isoforms have been shown to inhibit the catalytic activity of the proteasome. Here we review potential interactions between prions and the proteasome outlining how the UPS may be implicated in prion-mediated neurodegeneration.
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Affiliation(s)
- Pelagia Deriziotis
- Department of Neurodegenerative Disease, Institute of Neurology, University College London, London, WC1N 3BG, UK
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371
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Linden R, Martins VR, Prado MAM, Cammarota M, Izquierdo I, Brentani RR. Physiology of the prion protein. Physiol Rev 2008; 88:673-728. [PMID: 18391177 DOI: 10.1152/physrev.00007.2007] [Citation(s) in RCA: 435] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Prion diseases are transmissible spongiform encephalopathies (TSEs), attributed to conformational conversion of the cellular prion protein (PrP(C)) into an abnormal conformer that accumulates in the brain. Understanding the pathogenesis of TSEs requires the identification of functional properties of PrP(C). Here we examine the physiological functions of PrP(C) at the systemic, cellular, and molecular level. Current data show that both the expression and the engagement of PrP(C) with a variety of ligands modulate the following: 1) functions of the nervous and immune systems, including memory and inflammatory reactions; 2) cell proliferation, differentiation, and sensitivity to programmed cell death both in the nervous and immune systems, as well as in various cell lines; 3) the activity of numerous signal transduction pathways, including cAMP/protein kinase A, mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt pathways, as well as soluble non-receptor tyrosine kinases; and 4) trafficking of PrP(C) both laterally among distinct plasma membrane domains, and along endocytic pathways, on top of continuous, rapid recycling. A unified view of these functional properties indicates that the prion protein is a dynamic cell surface platform for the assembly of signaling modules, based on which selective interactions with many ligands and transmembrane signaling pathways translate into wide-range consequences upon both physiology and behavior.
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Affiliation(s)
- Rafael Linden
- Instituto de Biofísica da Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
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372
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Herrmann J, Soares SM, Lerman LO, Lerman A. Potential role of the ubiquitin-proteasome system in atherosclerosis: aspects of a protein quality disease. J Am Coll Cardiol 2008; 51:2003-10. [PMID: 18498952 DOI: 10.1016/j.jacc.2008.02.047] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/28/2008] [Accepted: 02/12/2008] [Indexed: 11/28/2022]
Abstract
Misfolded or damaged proteins are recognized intracellularly by protein quality mechanisms. These include chaperones and the ubiquitin-proteasome system, which aim at restoration of protein function and protein removal, respectively. A number of studies have outlined the functional significance of the ubiquitin-proteasome system for the heart and, as of recently, for the vascular system. This review summarizes these recent findings with a focus on atherosclerosis. In particular, this paper reflects on the viewpoint of atherosclerosis as a protein quality disease.
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Affiliation(s)
- Joerg Herrmann
- Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
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373
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Stress-protective signalling of prion protein is corrupted by scrapie prions. EMBO J 2008; 27:1974-84. [PMID: 18566584 DOI: 10.1038/emboj.2008.122] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 05/30/2008] [Indexed: 01/11/2023] Open
Abstract
Studies in transgenic mice revealed that neurodegeneration induced by scrapie prion (PrP(Sc)) propagation is dependent on neuronal expression of the cellular prion protein PrP(C). On the other hand, there is evidence that PrP(C) itself has a stress-protective activity. Here, we show that the toxic activity of PrP(Sc) and the protective activity of PrP(C) are interconnected. With a novel co-cultivation assay, we demonstrate that PrP(Sc) can induce apoptotic signalling in PrP(C)-expressing cells. However, cells expressing PrP mutants with an impaired stress-protective activity were resistant to PrP(Sc)-induced toxicity. We also show that the internal hydrophobic domain promotes dimer formation of PrP and that dimerization of PrP is linked to its stress-protective activity. PrP mutants defective in dimer formation did not confer enhanced stress tolerance. Moreover, in chronically scrapie-infected neuroblastoma cells the amount of PrP(C) dimers inversely correlated with the amount of PrP(Sc) and the resistance of the cells to various stress conditions. Our results provide new insight into the mechanism of PrP(C)-mediated neuroprotection and indicate that pathological PrP conformers abuse PrP(C)-dependent pathways for apoptotic signalling.
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374
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Paulick MG, Bertozzi CR. The glycosylphosphatidylinositol anchor: a complex membrane-anchoring structure for proteins. Biochemistry 2008; 47:6991-7000. [PMID: 18557633 PMCID: PMC2663890 DOI: 10.1021/bi8006324] [Citation(s) in RCA: 399] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Positioned at the C-terminus of many eukaryotic proteins, the glycosylphosphatidylinositol (GPI) anchor is a posttranslational modification that anchors the modified protein in the outer leaflet of the cell membrane. The GPI anchor is a complex structure comprising a phosphoethanolamine linker, glycan core, and phospholipid tail. GPI-anchored proteins are structurally and functionally diverse and play vital roles in numerous biological processes. While several GPI-anchored proteins have been characterized, the biological functions of the GPI anchor have yet to be elucidated at a molecular level. This review discusses the structural diversity of the GPI anchor and its putative cellular functions, including involvement in lipid raft partitioning, signal transduction, targeting to the apical membrane, and prion disease pathogenesis. We specifically highlight studies in which chemically synthesized GPI anchors and analogues have been employed to study the roles of this unique posttranslational modification.
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Affiliation(s)
- Margot G Paulick
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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375
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Noinville S, Chich JF, Rezaei H. Misfolding of the prion protein: linking biophysical and biological approaches. Vet Res 2008; 39:48. [PMID: 18533092 DOI: 10.1051/vetres:2008025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Accepted: 06/03/2008] [Indexed: 01/19/2023] Open
Abstract
Prion diseases are a group of neurodegenerative diseases that can arise spontaneously, be inherited, or acquired by infection in mammals. The propensity of the prion protein to adopt different structures is a clue to its pathological and perhaps biological role too. While the normal monomeric PrP is well characterized, the misfolded conformations responsible for neurodegeneration remain elusive despite progress in this field. Both structural dynamics and physico-chemical approaches are thus fundamental for a better knowledge of the molecular basis of this pathology. Indeed, multiple misfolding pathways combined with extensive posttranslational modifications of PrP and probable interaction(s) with cofactors call for a combination of approaches. In this review, we outline the current physico-chemical knowledge explaining the conformational diversities of PrP in relation with postulated or putative cellular partners such as proteic or non-proteic ligands.
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Affiliation(s)
- Sylvie Noinville
- Institut National de la Recherche Agronomique, Virologie et Immunologie Moléculaires, F-78352 Jouy-en-Josas, France
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376
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Chen G, Ye Z, Yu X, Zou J, Mali P, Brodsky RA, Cheng L. Trophoblast differentiation defect in human embryonic stem cells lacking PIG-A and GPI-anchored cell-surface proteins. Cell Stem Cell 2008; 2:345-55. [PMID: 18397754 DOI: 10.1016/j.stem.2008.02.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Revised: 12/16/2007] [Accepted: 02/08/2008] [Indexed: 01/10/2023]
Abstract
Pluripotent human embryonic stem (hES) cells can differentiate into various cell types derived from the three embryonic germ layers and extraembryonic tissues such as trophoblasts. The mechanisms governing lineage choices of hES cells are largely unknown. Here, we report that we established two independent hES cell clones lacking a group of cell surface molecules, glycosyl-phosphatidyl-inositol-anchored proteins (GPI-APs). The GPI-AP deficiency in these two hES clones is due to the deficiency in the gene expression of PIG-A (phosphatidyl-inositol-glycan class A), which is required for the first step of GPI synthesis. GPI-AP-deficient hES cells were capable of forming embryoid bodies and initiating cell differentiation into the three embryonic germ layers. However, GPI-AP-deficient hES cells failed to form trophoblasts after differentiation induction by embryoid body formation or by adding exogenous BMP4. The defect in trophoblast formation was due to the lack of GPI-anchored BMP coreceptors, resulting in the impairment of full BMP4 signaling activation in the GPI-AP-deficient hES cells. These data reveal that GPI-AP-enhanced full activation of BMP signaling is required for human trophoblast formation.
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Affiliation(s)
- Guibin Chen
- Stem Cell Program, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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377
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Wiggins RC. Prion stability and infectivity in the environment. Neurochem Res 2008; 34:158-68. [PMID: 18483857 DOI: 10.1007/s11064-008-9741-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Accepted: 05/02/2008] [Indexed: 02/07/2023]
Abstract
The biology of normal prion protein and the property of infectivity observed in abnormal folding conformations remain thinly characterized. However, enough is known to understand that prion proteins stretch traditional views of proteins in biological systems. Numerous investigators are resolving details of the novel mechanism of infectivity, which appears to feature a protein-only, homologous replication of misfolded isoforms. Many other features of prion biology are equally extraordinary. This review focuses on the status of infectious prions in various natural and man-made environments. The picture that emerges is that prion proteins are durable under extreme conditions of environmental exposure that are uncommon in biological phenomena, and this durability offers the potential for environmental reservoirs of persistent infectivity lasting for years. A recurrent theme in prion research is a propensity for these proteins to bind to mineral and metal surfaces, and several investigators have provided evidence that the normal cellular functions of prion protein may include metalloprotein interactions. This structural propensity for binding to mineral and metal ions offers the hypothesis that prion polypeptides are intrinsically predisposed to non-physiological folding conformations that would account for their environmental durability and persistent infectivity. Similarly, the avidity of binding and potency of prion infectivity from environmental sources also offers a recent hypothesis that prion polypeptides bound to soil minerals are actually more infectious than studies with purified polypeptides would predict. Since certain of the prion diseases have a history of epidemics in economically important animal species and have the potential to transmit to humans, urgency is attached to understanding the environmental transmission of prion diseases and the development of protocols for their containment and inactivation.
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Affiliation(s)
- Richard C Wiggins
- National Health and Environmental Effects Research Laboratory, US EPA/Office of Research and Development, MD B305-02, Research Triangle Park, NC 27711, USA.
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378
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Chaperone-dependent amyloid assembly protects cells from prion toxicity. Proc Natl Acad Sci U S A 2008; 105:7206-11. [PMID: 18480252 DOI: 10.1073/pnas.0802593105] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein conformational diseases are associated with the aberrant accumulation of amyloid protein aggregates, but whether amyloid formation is cytotoxic or protective is unclear. To address this issue, we investigated a normally benign amyloid formed by the yeast prion [RNQ(+)]. Surprisingly, modest overexpression of Rnq1 protein was deadly, but only when preexisting Rnq1 was in the [RNQ(+)] prion conformation. Molecular chaperones protect against protein aggregation diseases and are generally believed to do so by solubilizing their substrates. The Hsp40 chaperone, Sis1, suppressed Rnq1 proteotoxicity, but instead of blocking Rnq1 protein aggregation, it stimulated conversion of soluble Rnq1 to [RNQ(+)] amyloid. Furthermore, interference with Sis1-mediated [RNQ(+)] amyloid formation exacerbated Rnq1 toxicity. These and other data establish that even subtle changes in the folding homeostasis of an amyloidogenic protein can create a severe proteotoxic gain-of-function phenotype and that chaperone-mediated amyloid assembly can be cytoprotective. The possible relevance of these findings to other phenomena, including prion-driven neurodegenerative diseases and heterokaryon incompatibility in fungi, is discussed.
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379
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Aguzzi A, Sigurdson C, Heikenwaelder M. Molecular mechanisms of prion pathogenesis. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2008; 3:11-40. [PMID: 18233951 DOI: 10.1146/annurev.pathmechdis.3.121806.154326] [Citation(s) in RCA: 253] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Prion diseases are infectious neurodegenerative diseases occurring in humans and animals with an invariably lethal outcome. One fundamental mechanistic event in prion diseases is the aggregation of aberrantly folded prion protein into large amyloid plaques and fibrous structures associated with neurodegeneration. The cellular prion protein (PrPC) is absolutely required for disease development, and prion knockout mice are not susceptible to prion disease. Prions accumulate not only in the central nervous system but also in lymphoid organs, as shown for new variant and sporadic Creutzfeldt-Jakob patients and for some animals. To date it is largely accepted that prions consist primarily of PrPSc, a misfolded and aggregated beta-sheet-rich isoform of PrPC. However, PrPSc may or may not be completely congruent with the infectious moiety. Here, we discuss the molecular mechanisms leading to neurodegeneration, the role of the immune system in prion pathogenesis, and the existence of prion strains that appear to have different tropisms and biochemical characteristics.
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Affiliation(s)
- Adriano Aguzzi
- Institute of Neuropathology, University Hospital of Zürich, CH-8091 Zürich, Switzerland.
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380
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Kikuchi Y, Kakeya T, Nakajima O, Sakai A, Ikeda K, Yamaguchi N, Yamazaki T, Tanamoto KI, Matsuda H, Sawada JI, Takatori K. Hypoxia induces expression of a GPI-anchorless splice variant of the prion protein. FEBS J 2008; 275:2965-76. [PMID: 18445040 DOI: 10.1111/j.1742-4658.2008.06452.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human prion protein (PrP) is a glycoprotein with a glycosylphosphatidylinositol (GPI) anchor at its C-terminus. Here we report alternative splicing within exon 2 of the PrP gene (PRNP) in the human glioblastoma cell line T98G. The open reading frame of the alternatively spliced mRNA lacked the GPI anchor signal sequence and encoded a 230 amino acid polypeptide. Its product, GPI-anchorless PrP (GPI(-) PrPSV), was unglycosylated and soluble in non-ionic detergent, and was found in the cytosolic fraction. We also detected low levels of alternatively spliced mRNA in human brain and non-neuronal tissues. When long-term passaged T98G cells were placed in a low-oxygen environment, alternatively spliced mRNA expression increased and expression of normally spliced PrP mRNA decreased. These findings imply that oxygen tension regulates GPI(-) PrPSV expression in T98G cells.
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Affiliation(s)
- Yutaka Kikuchi
- Division of Microbiology, National Institute of Health Sciences, Tokyo, Japan.
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381
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Heiseke A, Schöbel S, Lichtenthaler SF, Vorberg I, Groschup MH, Kretzschmar H, Schätzl HM, Nunziante M. The novel sorting nexin SNX33 interferes with cellular PrP formation by modulation of PrP shedding. Traffic 2008; 9:1116-29. [PMID: 18419754 DOI: 10.1111/j.1600-0854.2008.00750.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The cellular prion protein (PrP(c)) is a glycosyl-phosphatidylinositol (GPI)-anchored protein trafficking in the secretory and endocytic pathway and localized mainly at the plasma membrane. Conversion of PrP(c) into its pathogenic isoform PrP(Sc) is associated with pathogenesis and transmission of prion diseases. Intramolecular cleavage in the middle, the extreme C-terminal part or within the GPI anchor and shedding of PrP(c) modulate this conversion process by reducing the substrate for prion formation. These phenomena provide similarities with the processing of amyloid precursor protein in Alzheimer's disease. Sorting nexins are a family of proteins with important functions in protein trafficking. In this study, we investigated the role of the newly described sorting nexin 33 (SNX33) in trafficking and processing of PrP(c). We found that overexpression of SNX33 in neuronal and non-neuronal cell lines resulted in increased shedding of full-length PrP(c) from the plasma membrane and modulated the rate of PrP(c) endocytosis. This was paralleled by reduction of PrP(Sc) formation in persistently and newly infected cells. Using deletion mutants, we demonstrate that production of PrP fragment N1 is not influenced by SNX33. Our data provide new insights into the cellular mechanisms of PrP(c) shedding and show how this can affect cellular PrP(Sc) conversion.
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Affiliation(s)
- Andreas Heiseke
- Institute of Virology, Technical University of Munich, Trogerstr. 30, 81675 Munich, Germany
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382
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Crozet C, Beranger F, Lehmann S. Cellular pathogenesis in prion diseases. Vet Res 2008; 39:44. [DOI: 10.1051/vetres:2008021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Accepted: 04/15/2008] [Indexed: 01/15/2023] Open
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383
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Polymenidou M, Trusheim H, Stallmach L, Moos R, Julius C, Miele G, Lenz-Bauer C, Aguzzi A. Canine MDCK cell lines are refractory to infection with human and mouse prions. Vaccine 2008; 26:2601-14. [PMID: 18423803 DOI: 10.1016/j.vaccine.2008.03.035] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 03/05/2008] [Accepted: 03/11/2008] [Indexed: 11/25/2022]
Abstract
Influenza vaccine production in embryonated eggs is associated with many disadvantages, and production in cell culture systems is a viable alternative. Madin Darby canine kidney (MDCK) cells are permissive for a variety of orthomyxoviruses and have proven particularly suitable for vaccine mass production. However, mammalian cells harboring the Prnp gene can theoretically acquire prion infections. Here, we have attempted to infect MDCK cells and substrains thereof with prions. We found that MDCK cells did not produce any protease-resistant PrP(Sc) upon exposure to brain homogenates derived from humans suffering from Creutzfeldt-Jakob disease (CJD) or from mice infected with Rocky Mountain Laboratory (RML) scrapie prions. Further, transmission of MDCK lysates to N2aPK1 cells did not induce formation of PrP(Sc) in the latter. PrP(C) biogenesis and processing in MDCK cells were similar to those of prion-sensitive N2aPK1 cells. However, steady-state levels of PrP(C) were very low, and PrP(C) did not partition with detergent-resistant membranes upon density gradient analysis. These factors may account for their resistance to infection. Alternatively, prion resistance may be related to the specific sequence of canine Prnp, as suggested by the lack of documented prion diseases in dogs.
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Affiliation(s)
- Magdalini Polymenidou
- Institute of Neuropathology, University Hospital of Zürich, Schmelzbergstrasse 12, Zürich, Switzerland.
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384
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Sim VL, Caughey B. Ultrastructures and strain comparison of under-glycosylated scrapie prion fibrils. Neurobiol Aging 2008; 30:2031-42. [PMID: 18394757 DOI: 10.1016/j.neurobiolaging.2008.02.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Revised: 12/27/2007] [Accepted: 02/22/2008] [Indexed: 01/08/2023]
Abstract
Prions, composed primarily of misfolded, often fibrillar, polymers of prion protein, have poorly understood structures. Heavy surface glycosylation may obscure visualization of their fibrillar cores, so we purified severely under-glycosylated prion protein fibrils from scrapie-infected transgenic mice expressing anchorless prion protein. Using electron and atomic force microscopy, we obtained dimensions and morphological information about prion protein core protofilaments which variably intertwined to form scrapie fibrils. Occasional isolated protofilaments were observed, suggesting that the lateral association of protofilaments is neither essential nor invariant in prion protein polymerization. Strain comparisons suggested basic structural differences; ME7 and 22L fibrils contained thinner protofilaments, 22L fibrils preferred left-handed twists, and 22L fibril periodicities averaged 106nm per half-turn, compared with 64 and 66nm for RML and ME7 fibrils, respectively. The strains displayed overlapping fibril morphologies, providing evidence that prion fibril morphology is influenced, but not dictated, by strain-dependent differences in protofilament structure. These measurements of the amyloid core of scrapie fibrils should aid development of models of prion structure and strain determination.
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Affiliation(s)
- Valerie L Sim
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840, United States.
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385
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Gayrard V, Picard-Hagen N, Viguié C, Jeunesse E, Tabouret G, Rezaei H, Toutain PL. Blood clearance of the prion protein introduced by intravenous route in sheep is influenced by host genetic and physiopathologic factors. Transfusion 2008; 48:609-19. [DOI: 10.1111/j.1537-2995.2007.01628.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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386
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Normal cellular prion protein with a methionine at position 129 has a more exposed helix 1 and is more prone to aggregate. Biochem Biophys Res Commun 2008; 368:875-81. [DOI: 10.1016/j.bbrc.2008.01.172] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Accepted: 01/30/2008] [Indexed: 11/22/2022]
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387
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Gavín R, Ureña J, Rangel A, Pastrana MA, Requena JR, Soriano E, Aguzzi A, Del Río JA. Fibrillar prion peptide PrP(106-126) treatment induces Dab1 phosphorylation and impairs APP processing and Abeta production in cortical neurons. Neurobiol Dis 2008; 30:243-54. [PMID: 18374587 DOI: 10.1016/j.nbd.2008.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 01/30/2008] [Accepted: 02/01/2008] [Indexed: 02/03/2023] Open
Abstract
Alzheimer's disease and prion diseases (e.g., Creutzfeldt-Jakob disease) display profound neural lesions associated with aberrant protein processing and extracellular amyloid deposits. However, the intracellular events in prion diseases and their relation with the processing of the amyloid precursor protein (APP) and beta-amyloid generation are unknown. The adaptor protein Dab1 may regulate intracellular trafficking and secretase-mediated proteolysis in APP processing. However, a putative relationship between prion diseases and Dab1/APP interactions is lacking. Thus, we examined, in inoculated animals, whether Dab1 and APP processing are targets of the intracellular events triggered by extracellular exposure to PrP(106-126) peptide. Our in vitro results indicate that PrP(106-126) peptide induces tyrosine phosphorylation of Dab1 by activated members of the Src family of tyrosine kinases (SFK), which implies further Dab1 degradation. We also corroborate these results in Dab1 protein levels in prion-inoculated hamsters. Finally, we show that fibrillar prion peptides have a dual effect on APP processing and beta-amyloid production. First, they block APP trafficking at the cell membrane, thus decreasing beta-amyloid production. In parallel, they reduce Dab1 levels, which also alter APP processing. Lastly, neuronal cultures from Dab1-deficient mice showed severe impairment of APP processing with reduced sAPP secretion and A beta production after prion peptide incubation. Taken together, these data indicate a link between intracellular events induced by exposure to extracellular fibrillar peptide or PrP(res), and APP processing and implicate Dab1 in this link.
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Affiliation(s)
- Rosalina Gavín
- Cellular and Molecular Basis of Neurodegeneration and Neurorepair, Department of Cell Biology, University of Barcelona, Spain
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388
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Kovacs GG, Budka H. Prion diseases: from protein to cell pathology. THE AMERICAN JOURNAL OF PATHOLOGY 2008; 172:555-65. [PMID: 18245809 DOI: 10.2353/ajpath.2008.070442] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prion diseases or transmissible spongiform encephalopathies are fatal neurodegenerative conditions in humans and animals that originate spontaneously, genetically or by infection. Conformational change of the normal (cellular) form of prion protein (PrP c) to a pathological, disease-associated form (PrP TSE) is considered central to pathogenesis and formation of the infectious agent or prion. Neuronal damage is central to clinical manifestation of prion diseases but poorly understood. In this review, we analyze the major pathogenetic pathways that lead to tissue pathology in different forms of disease. Neuropathogenesis of prion diseases evolves in complex ways on several front lines, most but not all of which exist also in other neurodegenerative as well as infectious diseases. Whereas intracellular accumulation of PrP forms might significantly impair cell function and lead to cytopathology, mere extracellular deposition of PrP TSE is questionable as a direct cytotoxic factor. Tissue damage may result from several parallel, interacting, or subsequent pathways. Future studies should clarify the trigger(s) and sequence of these processes and whether, and which, one is dominating or decisive.
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Affiliation(s)
- Gabor G Kovacs
- Institute of Neurology, Medical University of Vienna, AKH 4J, Waehringer Guertel 18-20, POB 48, 1097 Vienna, Austria
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389
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Insights into the mechanism of prion propagation. Curr Opin Struct Biol 2008; 18:52-9. [DOI: 10.1016/j.sbi.2007.12.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 12/12/2007] [Accepted: 12/13/2007] [Indexed: 11/23/2022]
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390
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Pavlícek A, Bednárová L, Holada K. Production, purification and oxidative folding of the mouse recombinant prion protein. Folia Microbiol (Praha) 2008; 52:391-7. [PMID: 18062188 DOI: 10.1007/bf02932094] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The method leading to overexpression of the full-length mouse recombinant prion protein (mrPrP 23-231) in the cytoplasm of E. coli as a his-PrP fusion protein and its effective purification using affinity chromatography is described. A typical yield of the method was 8-10 mg his-mrPrP per L of the bacterial culture. The purity of purified protein was > 95 %. The purified his-mrPrP was converted to a soluble form and its folding to alpha-helical and beta-sheet conformations was studied. The properties of differently folded mrPrP were determined by measuring their circular dichroism spectra, partial resistance to cleavage by proteinase K and by centrifugation in sucrose gradient.
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Affiliation(s)
- A Pavlícek
- Institute of Microbiology and Immunology, 1st Faculty of Medicine, Charles University, 128 00 Prague, Czechia
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391
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Gu Y, Singh A, Bose S, Singh N. Pathogenic mutations in the glycosylphosphatidylinositol signal peptide of PrP modulate its topology in neuroblastoma cells. Mol Cell Neurosci 2008; 37:647-56. [PMID: 18325785 DOI: 10.1016/j.mcn.2007.08.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 07/27/2007] [Accepted: 08/06/2007] [Indexed: 10/22/2022] Open
Abstract
Point mutations M232R (PrP(232R)), M232T (PrP(232T)), and P238S (PrP(238S)) in the glycosylphosphatidylinositol signal peptide (GPI-SP) of the prion protein (PrP(C)) segregate with familial Creutzfeldt-Jakob disease (CJD). However, the mechanism by which these mutations induce cytotoxicity is unclear since the GPI-SP is replaced by a GPI anchor within 5 min of PrP synthesis and translocation into the endoplasmic reticulum (ER). To examine if mutations in this region interfere with translocation of nascent PrP into the ER or anchor addition, the metabolism of PrP(232R) and PrP(232T) was investigated in transfected human neuroblastoma cells. In this report, we demonstrate that PrP mutations M232R and M232T do not interfere with GPI anchor addition. Instead, these mutations increase the stability and transport of GPI-SP mediated post-translationally translocated PrP to the plasma membrane, where it is linked to the lipid bilayer in a potentially neurotoxic C-transmembrane ((Ctm)PrP) orientation. Furthermore, we demonstrate that the GPI-SP of PrP functions as an efficient co-translational and inefficient post-translational ER translocation signal when tagged to an unrelated protein, underscoring the functional versatility of this peptide. These data uncover an alternate pathway of ER translocation for nascent PrP, and provide information on the possible mechanism(s) of neurotoxicity by mutations in the GPI-SP.
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Affiliation(s)
- Yaping Gu
- Department of Pathology, Case Western Reserve University, 2103 Cornell Road, Cleveland, Ohio 44106, USA
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392
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Winklhofer KF, Tatzelt J, Haass C. The two faces of protein misfolding: gain- and loss-of-function in neurodegenerative diseases. EMBO J 2008; 27:336-49. [PMID: 18216876 PMCID: PMC2234348 DOI: 10.1038/sj.emboj.7601930] [Citation(s) in RCA: 282] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Accepted: 10/24/2007] [Indexed: 12/15/2022] Open
Abstract
The etiologies of neurodegenerative diseases may be diverse; however, a common pathological denominator is the formation of aberrant protein conformers and the occurrence of pathognomonic proteinaceous deposits. Different approaches coming from neuropathology, genetics, animal modeling and biophysics have established a crucial role of protein misfolding in the pathogenic process. However, there is an ongoing debate about the nature of the harmful proteinaceous species and how toxic conformers selectively damage neuronal populations. Increasing evidence indicates that soluble oligomers are associated with early pathological alterations, and strikingly, oligomeric assemblies of different disease-associated proteins may share common structural features. A major step towards the understanding of mechanisms implicated in neuronal degeneration is the identification of genes, which are responsible for familial variants of neurodegenerative diseases. Studies based on these disease-associated genes illuminated the two faces of protein misfolding in neurodegeneration: a gain of toxic function and a loss of physiological function, which can even occur in combination. Here, we summarize how these two faces of protein misfolding contribute to the pathomechanisms of Alzheimer's disease, frontotemporal lobar degeneration, Parkinson's disease and prion diseases.
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Affiliation(s)
- Konstanze F Winklhofer
- Neurobiochemisty, Department of Biochemistry, Adolf-Butenandt-Institute, Ludwig-Maximilians-University, Munich, Germany
| | - Jörg Tatzelt
- Neurobiochemisty, Department of Biochemistry, Adolf-Butenandt-Institute, Ludwig-Maximilians-University, Munich, Germany
| | - Christian Haass
- Center for Integrated Protein Science Munich and Laboratory for Neurodegenerative Disease Research, Department of Biochemistry, Adolf-Butenandt-Institute, Ludwig-Maximilians-University, Munich, Germany
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393
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Sakudo A, Wu G, Onodera T, Ikuta K. Octapeptide repeat region of prion protein (PrP) is required at an early stage for production of abnormal prion protein in PrP-deficient neuronal cell line. Biochem Biophys Res Commun 2008; 365:164-9. [PMID: 17981146 DOI: 10.1016/j.bbrc.2007.10.158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 10/25/2007] [Indexed: 11/30/2022]
Abstract
An abnormal isoform of prion protein (PrP(Sc)), which is composed of the same amino acids as cellular PrP (PrP(C)) and has proteinase K (PK)-resistance, hypothetically converts PrP(C) into PrP(Sc). To investigate the region important for PrP(Sc) production, we examined the levels of PrP(Sc) in PrP gene-deficient cells (HpL3-4) expressing PrP(C) deleted of various regions including the octapeptide repeat region (OR) or hydrophobic region (HR). After Chandler or Obihiro prion infection, PrP(Sc) was produced in HpL3-4 cells expressing wild-type PrP(C) or PrP(C) deleted of HR at an early stage and further reduced to below the detectable level, whereas cells expressing PrP(C) deleted of OR showed no PrP(Sc) production. The results suggest that OR of PrP(C) is required for the early step of efficient PrP(Sc) production.
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Affiliation(s)
- Akikazu Sakudo
- Department of Virology, Center for Infectious Disease Control, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan.
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394
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Olschewski D, Becker CFW. Chemical synthesis and semisynthesis of membrane proteins. MOLECULAR BIOSYSTEMS 2008; 4:733-40. [DOI: 10.1039/b803248c] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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395
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Abstract
Prions represent a new biological paradigm of protein-mediated information transfer. In mammals, prions are the cause of fatal, transmissible neurodegenerative diseases, often referred to as transmissible spongiform encephalopathies. Many unresolved issues remain, including the exact molecular nature of the prion, the detailed mechanism of prion propagation, and the mechanism by which prion diseases can be both genetic and infectious. In addition, we know little about the mechanism by which neurons degenerate during prion diseases. Tied to this, the physiological function of the normal form of the prion protein remains unclear, and it is uncertain whether loss of this function contributes to prion pathogenesis. The factors governing the transmission of prions between species remain unclear, in particular the means by which prion strains and PrP primary structure interact to affect interspecies prion transmission. Despite all these unknowns, dramatic advances in our understanding of prions have occurred because of their transmissibility to experimental animals and the development of transgenic mouse models has done much to further our understanding about various aspects of prion biology. In this chapter, I review recent advances in our understanding of prion biology that derive from this powerful and informative approach.
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Affiliation(s)
- Glenn C Telling
- Department of Microbiology, Immunology and Molecular Genetics, Sanders Brown Center on Aging, University of Kentucky, Lexington, KY, USA
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396
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Griffiths RE, Heesom KJ, Anstee DJ. Normal prion protein trafficking in cultured human erythroblasts. Blood 2007; 110:4518-25. [PMID: 17827389 DOI: 10.1182/blood-2007-04-085183] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Normal prion protein (PrPc), an essential substrate for development of prion disease, is widely distributed in hematopoietic cells. Recent evidence that variant Creutzfeldt-Jakob disease can be transmitted by transfusion of red cell preparations has highlighted the need for a greater understanding of the biology of PrPc in blood and blood-forming tissues. Here, we show that in contrast to another glycosylphosphoinositol-anchored protein CD59, PrPc at the cell surface of cultured human erythroblasts is rapidly internalized through the endosomal pathway, where it colocalizes with the tetraspanin CD63. In the plasma membrane, PrPc colocalizes with the tetraspanin CD81. Cross-linking with anti-PrPc or anti-CD81 causes clustering of PrPc and CD81, suggesting they can share the same microdomain. These data are consistent with a role for tetraspanin-enriched microdomains in trafficking of PrPc. These results, when taken together with recent evidence that exosomes released from cells as a result of endosomal-mediated recycling to the plasma membrane contain prion infectivity, provide a pathway for the propagation of prion diseases.
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Affiliation(s)
- Rebecca E Griffiths
- Bristol Institute for Transfusion Sciences, National Blood Service, Bristol, UK
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397
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Harrison CF, Barnham KJ, Hill AF. Neurotoxic species in prion disease: a role for PrP isoforms? J Neurochem 2007; 103:1709-20. [DOI: 10.1111/j.1471-4159.2007.04936.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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398
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Abstract
Prions are lethal mammalian pathogens composed of aggregated conformational isomers of a host-encoded glycoprotein and which appear to lack nucleic acids. Their unique biology, allied with the public-health risks posed by prion zoonoses such as bovine spongiform encephalopathy, has focused much attention on the molecular basis of prion propagation and the "species barrier" that controls cross-species transmission. Both are intimately linked to understanding how multiple prion "strains" are encoded by a protein-only agent. The underlying mechanisms are clearly of much wider importance, and analogous protein-based inheritance mechanisms are recognized in yeast and fungi. Recent advances suggest that prions themselves are not directly neurotoxic, but rather their propagation involves production of toxic species, which may be uncoupled from infectivity.
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Affiliation(s)
- John Collinge
- MRC Prion Unit, Department of Neurodegenerative Disease, UCL Institute of Neurology, London WC1N 3BG, UK.
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399
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Abstract
The phenotypic effect of prions on host cells is influenced by the physical properties of the prion strain and its level of accumulation. In mammalian cell cultures, prion accumulation is determined by the interplay between de novo prion formation, catabolism, cell division, and horizontal cell-to-cell transmission. Understanding this dynamic enables the analytical modeling of protein-based heritability and infectivity. Here, we quantitatively measured these competing effects in a subline of neuroblastoma (N2a) cells and propose a concordant reaction mechanism to explain the kinetics of prion propagation. Our results show that cell division leads to a predictable reduction in steady-state prion levels but not to complete clearance. Scrapie-infected N2a cells were capable of accumulating different steady-state levels of prions, dictated partly by the rate of cell division. We also show that prions in this subline of N2a cells are transmitted primarily from mother to daughter cells, rather than horizontal cell-to-cell transmission. We quantitatively modeled our kinetic results based on a mechanism that assumes a subpopulation of prions is capable of self-catalysis, and the levels of this subpopulation reach saturation in fully infected cells. Our results suggest that the apparent effectiveness of antiprion compounds in culture may be strongly influenced by the growth phase of the target cells.
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400
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Krammer C, Suhre MH, Kremmer E, Diemer C, Hess S, Schätzl HM, Scheibel T, Vorberg I. Prion protein/protein interactions: fusion with yeast Sup35p-NM modulates cytosolic PrP aggregation in mammalian cells. FASEB J 2007; 22:762-73. [PMID: 17928365 DOI: 10.1096/fj.07-8733com] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In mammalian prion diseases, an abnormally folded, aggregated form of the prion protein (PrP(Sc)) appears to catalyze a conformational switch of its cellular isoform (PrP(C)) to an aggregated state. A similar prion-like phenomenon has been reported for the Saccharomyces cerevisiae translation termination factor Sup35p that can adopt a self-propagating conformation. We have compared aggregation propensities of chimeric proteins derived from the Sup35p prion domain NM and PrP in vitro and in the cytosol of mammalian cells. Sup35p-NM and PrP displayed strikingly different aggregation behaviors when expressed in mammalian cells, with NM remaining soluble and cytosolic PrP spontaneously aggregating due to the globular domain of PrP. When fused to PrP(90-230), Sup35p-M exhibited an inhibitory effect for nucleation but increased aggregate growth, potentially by facilitating recruitment of newly synthesized chimeric proteins into the growing aggregates. This effect, however, could, to some extent, be counteracted by the prion-forming region Sup35p-N, thereby increasing aggregate frequency. Interestingly, a lowered nucleation rate was also observed in the presence of the amino-terminal region of PrP, suggesting that Sup35p-M and PrP(23-90) share some biological function in prion protein assembly. Our results provide new insights into prion protein aggregation behaviors, demonstrating the impact of dynamic interactions between prion domains and suggesting that aggregation of yeast and mammalian prion proteins is strongly influenced by yet unidentified cellular conditions or factors.
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Affiliation(s)
- Carmen Krammer
- Institute of Virology, Technical University of Munich, Trogerstr. 30, 81675 Munich, Germany
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