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Silva JL, Vieira TCRG, Gomes MPB, Rangel LP, Scapin SMN, Cordeiro Y. Experimental approaches to the interaction of the prion protein with nucleic acids and glycosaminoglycans: Modulators of the pathogenic conversion. Methods 2010; 53:306-17. [PMID: 21145399 DOI: 10.1016/j.ymeth.2010.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 12/02/2010] [Indexed: 11/17/2022] Open
Abstract
The concept that transmissible spongiform encephalopathies (TSEs) are caused only by proteins has changed the traditional paradigm that disease transmission is due solely to an agent that carries genetic information. The central hypothesis for prion diseases proposes that the conversion of a cellular prion protein (PrP(C)) into a misfolded, β-sheet-rich isoform (PrP(Sc)) accounts for the development of (TSE). There is substantial evidence that the infectious material consists chiefly of a protein, PrP(Sc), with no genomic coding material, unlike a virus particle, which has both. However, prions seem to have other partners that chaperone their activities in converting the PrP(C) into the disease-causing isoform. Nucleic acids (NAs) and glycosaminoglycans (GAGs) are the most probable accomplices of prion conversion. Here, we review the recent experimental approaches that have been employed to characterize the interaction of prion proteins with nucleic acids and glycosaminoglycans. A PrP recognizes many nucleic acids and GAGs with high affinities, and this seems to be related to a pathophysiological role for this interaction. A PrP binds nucleic acids and GAGs with structural selectivity, and some PrP:NA complexes can become proteinase K-resistant, undergoing amyloid oligomerization and conversion to a β-sheet-rich structure. These results are consistent with the hypothesis that endogenous polyanions (such as NAs and GAGs) may accelerate the rate of prion disease progression by acting as scaffolds or lattices that mediate the interaction between PrP(C) and PrP(Sc) molecules. In addition to a still-possible hypothesis that nucleic acids and GAGs, especially those from the host, may modulate the conversion, the recent structural characterization of the complexes has raised the possibility of developing new diagnostic and therapeutic strategies.
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Affiliation(s)
- Jerson L Silva
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, Brazil.
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Nicoll AJ, Trevitt CR, Tattum MH, Risse E, Quarterman E, Ibarra AA, Wright C, Jackson GS, Sessions RB, Farrow M, Waltho JP, Clarke AR, Collinge J. Pharmacological chaperone for the structured domain of human prion protein. Proc Natl Acad Sci U S A 2010; 107:17610-5. [PMID: 20876144 PMCID: PMC2955083 DOI: 10.1073/pnas.1009062107] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In prion diseases, the misfolded protein aggregates are derived from cellular prion protein (PrP(C)). Numerous ligands have been reported to bind to human PrP(C) (huPrP), but none to the structured region with the affinity required for a pharmacological chaperone. Using equilibrium dialysis, we screened molecules previously suggested to interact with PrP to discriminate between those which did not interact with PrP, behaved as nonspecific polyionic aggregates or formed a genuine interaction. Those that bind could potentially act as pharmacological chaperones. Here we report that a cationic tetrapyrrole [Fe(III)-TMPyP], which displays potent antiprion activity, binds to the structured region of huPrP. Using a battery of biophysical techniques, we demonstrate that Fe(III)-TMPyP forms a 11 complex via the structured C terminus of huPrP with a K(d) of 4.5 ± 2 μM, which is in the range of its IC(50) for curing prion-infected cells of 1.6 ± 0.4 μM and the concentration required to inhibit protein-misfolding cyclic amplification. Therefore, this molecule tests the hypothesis that stabilization of huPrP(C), as a principle, could be used in the treatment of human prion disease. The identification of a binding site with a defined 3D structure opens up the possibility of designing small molecules that stabilize huPrP and prevent its conversion into the disease-associated form.
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Affiliation(s)
| | - Clare R. Trevitt
- Medical Research Council Prion Unit, University College of London Institute of Neurology, Queen Square, London WCN1 3BG, United Kingdom
| | - M. Howard Tattum
- Medical Research Council Prion Unit, University College of London Institute of Neurology, Queen Square, London WCN1 3BG, United Kingdom
| | | | | | - Amaurys Avila Ibarra
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom; and
| | | | - Graham S. Jackson
- Medical Research Council Prion Unit, University College of London Institute of Neurology, Queen Square, London WCN1 3BG, United Kingdom
| | - Richard B. Sessions
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom; and
| | | | - Jonathan P. Waltho
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Anthony R. Clarke
- Medical Research Council Prion Unit, University College of London Institute of Neurology, Queen Square, London WCN1 3BG, United Kingdom
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom; and
| | - John Collinge
- Department of Neurodegenerative Disease and
- Medical Research Council Prion Unit, University College of London Institute of Neurology, Queen Square, London WCN1 3BG, United Kingdom
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Brazier MW, Volitakis I, Kvasnicka M, White AR, Underwood JR, Green JE, Han S, Hill AF, Masters CL, Collins SJ. Manganese chelation therapy extends survival in a mouse model of M1000 prion disease. J Neurochem 2010; 114:440-51. [PMID: 20456001 DOI: 10.1111/j.1471-4159.2010.06771.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous in vitro and in vivo investigations have suggested manganese (Mn(2+)) may play a role in pathogenesis through facilitating refolding of the normal cellular form of the prion protein into protease resistant, pathogenic isoforms (PrP(Sc)), as well as the subsequent promotion of higher order aggregation of these abnormal conformers. To further explore the role of Mn(2+) in pathogenesis, we undertook a number of studies, including an assessment of the disease modifying effects of chelation therapy in a well-characterized mouse model of prion disease. The di-sodium, calcium derivative of the chelator, cyclohexanediaminetetraacetic acid (Na(2)CaCDTA), was administered intraperitoneally to mice inoculated intra-cerebrally with either high or low-dose inocula, with treatment beginning early (shortly after inoculation) or late (at the usual mid-survival point of untreated mice). Analyses by inductively coupled plasma-mass spectrometry demonstrated brain Mn(2+) levels were selectively reduced by up to 50% in treated mice compared with untreated controls, with copper, iron, zinc and cobalt levels unchanged. In mice administered high-dose inocula, none of the treatment groups displayed an increase in survival although western blot analyses of early intensively treated mice showed reduced brain PrP(Sc) levels; mice infected using low-dose inocula however, showed a significant prolongation of survival (p = 0.002). Although our findings support a role for Mn(2+) in prion disease, further studies are required to more precisely delineate the extent of pathogenic involvement.
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Affiliation(s)
- Marcus W Brazier
- Department of Pathology, The University of Melbourne, Melbourne, Victoria, Australia
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Cecarini V, Bonfili L, Cuccioloni M, Mozzicafreddo M, Angeletti M, Eleuteri AM. The relationship between the 20S proteasomes and prion-mediated neurodegenerations: potential therapeutic opportunities. Apoptosis 2010; 15:1322-35. [DOI: 10.1007/s10495-010-0480-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Silva JL, Vieira TCRG, Gomes MPB, Bom APA, Lima LMTR, Freitas MS, Ishimaru D, Cordeiro Y, Foguel D. Ligand binding and hydration in protein misfolding: insights from studies of prion and p53 tumor suppressor proteins. Acc Chem Res 2010; 43:271-9. [PMID: 19817406 PMCID: PMC2825094 DOI: 10.1021/ar900179t] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Protein misfolding has been implicated in a large number of diseases termed protein- folding disorders (PFDs), which include Alzheimer's disease, Parkinson's disease, transmissible spongiform encephalopathies, familial amyloid polyneuropathy, Huntington's disease, and type II diabetes. In these diseases, large quantities of incorrectly folded proteins undergo aggregation, destroying brain cells and other tissues. The interplay between ligand binding and hydration is an important component of the formation of misfolded protein species. Hydration drives various biological processes, including protein folding, ligand binding, macromolecular assembly, enzyme kinetics, and signal transduction. The changes in hydration and packing, both when proteins fold correctly or when folding goes wrong, leading to PFDs, are examined through several biochemical, biophysical, and structural approaches. Although in many cases the binding of a ligand such as a nucleic acid helps to prevent misfolding and aggregation, there are several examples in which ligands induce misfolding and assembly into amyloids. This occurs simply because the formation of structured aggregates (such as protofibrillar and fibrillar amyloids) involves decreases in hydration, formation of a hydrogen-bond network in the secondary structure, and burying of nonpolar amino acid residues, processes that also occur in the normal folding landscape. In this Account, we describe the present knowledge of the folding and misfolding of different proteins, with a detailed emphasis on mammalian prion protein (PrP) and tumoral suppressor protein p53; we also explore how ligand binding and hydration together influence the fate of the proteins. Anfinsen's paradigm that the structure of a protein is determined by its amino acid sequence is to some extent contradicted by the observation that there are two isoforms of the prion protein with the same sequence: the cellular and the misfolded isoform. The cellular isoform of PrP has a disordered N-terminal domain and a highly flexible, not-well-packed C-terminal domain, which might account for its significant hydration. When PrP binds to biological molecules, such as glycosaminoglycans and nucleic acids, the disordered segments appear to fold and become less hydrated. Formation of the PrP-nucleic acid complex seems to accelerate the conversion of the cellular form of the protein into the disease-causing isoform. For p53, binding to some ligands, including nucleic acids, would prevent misfolding of the protein. Recently, several groups have begun to analyze the folding-misfolding of the individual domains of p53, but several questions remain unanswered. We discuss the implications of these findings for understanding the productive and incorrect folding pathways of these proteins in normal physiological states and in human disease, such as prion disorders and cancer. These studies are shown to lay the groundwork for the development of new drugs.
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Affiliation(s)
- Jerson L. Silva
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | - Tuane C. R. G. Vieira
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | - Mariana P. B. Gomes
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | - Ana Paula Ano Bom
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | | | - Monica S. Freitas
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | - Daniella Ishimaru
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
| | | | - Debora Foguel
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem
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56
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Bell NM, Micklefield J. Chemical modification of oligonucleotides for therapeutic, bioanalytical and other applications. Chembiochem 2010; 10:2691-703. [PMID: 19739190 DOI: 10.1002/cbic.200900341] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Neil M Bell
- School of Chemistry, The University of Manchester, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester M1 7DN, UK
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Zon G. Automated synthesis of phosphorus–sulfur analogs of nucleic acids—25 years on: potential therapeutic agents and proven utility in biotechnology. NEW J CHEM 2010. [DOI: 10.1039/b9nj00577c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Glypican-1 mediates both prion protein lipid raft association and disease isoform formation. PLoS Pathog 2009; 5:e1000666. [PMID: 19936054 PMCID: PMC2773931 DOI: 10.1371/journal.ppat.1000666] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 10/26/2009] [Indexed: 11/28/2022] Open
Abstract
In prion diseases, the cellular form of the prion protein, PrPC, undergoes a conformational conversion to the infectious isoform, PrPSc. PrPC associates with lipid rafts through its glycosyl-phosphatidylinositol (GPI) anchor and a region in its N-terminal domain which also binds to heparan sulfate proteoglycans (HSPGs). We show that heparin displaces PrPC from rafts and promotes its endocytosis, suggesting that heparin competes with an endogenous raft-resident HSPG for binding to PrPC. We then utilised a transmembrane-anchored form of PrP (PrP-TM), which is targeted to rafts solely by its N-terminal domain, to show that both heparin and phosphatidylinositol-specific phospholipase C can inhibit its association with detergent-resistant rafts, implying that a GPI-anchored HSPG targets PrPC to rafts. Depletion of the major neuronal GPI-anchored HSPG, glypican-1, significantly reduced the raft association of PrP-TM and displaced PrPC from rafts, promoting its endocytosis. Glypican-1 and PrPC colocalised on the cell surface and both PrPC and PrPSc co-immunoprecipitated with glypican-1. Critically, treatment of scrapie-infected N2a cells with glypican-1 siRNA significantly reduced PrPSc formation. In contrast, depletion of glypican-1 did not alter the inhibitory effect of PrPC on the β-secretase cleavage of the Alzheimer's amyloid precursor protein. These data indicate that glypican-1 is a novel cellular cofactor for prion conversion and we propose that it acts as a scaffold facilitating the interaction of PrPC and PrPSc in lipid rafts. The prion diseases are unique in that their infectious nature is not dependent on nucleic acid but is instead attributed to a misfolded protein, the prion protein. This misfolded prion protein is capable of inducing the misfolding of the normal form of the prion protein that is present on the surface of neurons and other cells in the body. However, the site in the cell at which this misfolding occurs and whether other proteins are involved remains controversial. We have addressed these questions by investigating how the normal form of the prion protein is targeted to specialised domains on the plasma membrane termed cholesterol-rich lipid rafts. We show that targeting is due, in part, to a particular heparin sulfate proteoglycan called glypican-1. Significantly, reducing the levels of glypican-1 in an infected cell line reduced the accumulation of misfolded prion protein. We propose that glypican-1 acts as a scaffold facilitating the favourable interaction of the misfolded, infectious form of the prion protein with the normal cellular form within cholesterol-rich lipid rafts. Our results indicate that glypican-1 is intimately involved in the misfolding of the prion protein, the critical event in the pathogenesis of prion diseases such as Creutzfeldt-Jakob disease in humans.
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59
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Taubner LM, Bienkiewicz EA, Copié V, Caughey B. Structure of the flexible amino-terminal domain of prion protein bound to a sulfated glycan. J Mol Biol 2009; 395:475-90. [PMID: 19913031 DOI: 10.1016/j.jmb.2009.10.075] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 09/24/2009] [Accepted: 10/28/2009] [Indexed: 11/29/2022]
Abstract
The intrinsically disordered amino-proximal domain of hamster prion protein (PrP) contains four copies of a highly conserved octapeptide sequence, PHGGGWGQ, that is flanked by two polycationic residue clusters. This N-terminal domain mediates the binding of sulfated glycans, which can profoundly influence the conversion of PrP to pathological forms and the progression of prion disease. To investigate the structural consequences of sulfated glycan binding, we performed multidimensional heteronuclear ((1)H, (13)C, (15)N) NMR (nuclear magnetic resonance), circular dichroism (CD), and fluorescence studies on hamster PrP residues 23-106 (PrP 23-106) and fragments thereof when bound to pentosan polysulfate (PPS). While the majority of PrP 23-106 remain disordered upon PPS binding, the octarepeat region adopts a repeating loop-turn structure that we have determined by NMR. The beta-like turns within the repeats are corroborated by CD data demonstrating that these turns are also present, although less pronounced, without PPS. Binding to PPS exposes a hydrophobic surface composed of aligned tryptophan side chains, the spacing and orientation of which are consistent with a self-association or ligand binding site. The unique tryptophan motif was probed by intrinsic tryptophan fluorescence, which displayed enhanced fluorescence of PrP 23-106 when bound to PPS, consistent with the alignment of tryptophan side chains. Chemical-shift mapping identified binding sites on PrP 23-106 for PPS, which include the octarepeat histidine and an N-terminal basic cluster previously linked to sulfated glycan binding. These data may in part explain how sulfated glycans modulate PrP conformational conversions and oligomerizations.
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Affiliation(s)
- Lara M Taubner
- Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.
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60
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Abstract
Transmissible spongiform encephalopathies (TSEs) are inevitably lethal neurodegenerative diseases that affect humans and a large variety of animals. The infectious agent responsible for TSEs is the prion, an abnormally folded and aggregated protein that propagates itself by imposing its conformation onto the cellular prion protein (PrPC) of the host. PrPCis necessary for prion replication and for prion-induced neurodegeneration, yet the proximal causes of neuronal injury and death are still poorly understood. Prion toxicity may arise from the interference with the normal function of PrPC, and therefore, understanding the physiological role of PrPCmay help to clarify the mechanism underlying prion diseases. Here we discuss the evolution of the prion concept and how prion-like mechanisms may apply to other protein aggregation diseases. We describe the clinical and the pathological features of the prion diseases in human and animals, the events occurring during neuroinvasion, and the possible scenarios underlying brain damage. Finally, we discuss potential antiprion therapies and current developments in the realm of prion diagnostics.
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Ishimaru D, Ano Bom APD, Lima LMTR, Quesado PA, Oyama MFC, de Moura Gallo CV, Cordeiro Y, Silva JL. Cognate DNA stabilizes the tumor suppressor p53 and prevents misfolding and aggregation. Biochemistry 2009; 48:6126-35. [PMID: 19505151 DOI: 10.1021/bi9003028] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The tumor suppressor protein p53 is a nuclear protein that serves as an important transcription factor. The region responsible for sequence-specific DNA interaction is located in its core domain (p53C). Although full-length p53 binds to DNA as a tetramer, p53C binds as a monomer since it lacks the oligomerization domain. It has been previously demonstrated that two core domains have a dimerization interface and undergo conformational change when bound to DNA. Here we demonstrate that the interaction with a consensus DNA sequence provides the core domain of p53 with enhanced conformational stability at physiological salt concentrations (0.15 M). This stability could be either increased or abolished at low (0.01 M) or high (0.3 M) salt concentrations, respectively. In addition, interaction with the cognate sequence prevents aggregation of p53C into an amyloid-like structure, whereas binding to a nonconsensus DNA sequence has no effect on p53C stability, even at low ionic strength. Strikingly, sequence-specific DNA binding also resulted in a large stabilization of full-length p53, whereas nonspecific sequence binding led to no stabilization. The effects of cognate DNA could be mimicked by high concentrations of osmolytes such as glycerol, which implies that the stabilization is caused by the exclusion of water. Taken together, our results show an enhancement in protein stability driven by specific DNA recognition. When cognate DNA was added to misfolded protein obtained after a pressurization cycle, the original conformation was mostly recovered. Our results may aid the development of therapeutic approaches to prevent misfolded species of p53.
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Affiliation(s)
- Daniella Ishimaru
- Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil
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Lathe R, Harris A. Differential display detects host nucleic acid motifs altered in scrapie-infected brain. J Mol Biol 2009; 392:813-22. [PMID: 19631225 DOI: 10.1016/j.jmb.2009.07.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Revised: 07/08/2009] [Accepted: 07/16/2009] [Indexed: 10/20/2022]
Abstract
The transmissible spongiform encephalopathies (TSEs) including scrapie have been attributed to an infectious protein or prion. Infectivity is allied to conversion of the endogenous nucleic-acid-binding protein PrP to an infectious modified form known as PrP(sc). The protein-only theory does not easily explain the enigmatic properties of the agent including strain variation. It was previously suggested that a short nucleic acid, perhaps host-encoded, might contribute to the pathoetiology of the TSEs. No candidate host molecules that might explain transmission of strain differences have yet been put forward. Differential display is a robust technique for detecting nucleic acid differences between two populations. We applied this technique to total nucleic acid preparations from scrapie-infected and control brain. Independent RNA preparations from eight normal and eight scrapie-infected (strain 263K) hamster brains were randomly amplified and visualized in parallel. Though the nucleic acid patterns were generally identical in scrapie-infected versus control brain, some rare bands were differentially displayed. Molecular species consistently overrepresented (or underrepresented) in all eight infected brain samples versus all eight controls were excised from the display, sequenced, and assembled into contigs. Only seven ros contigs (RNAs over- or underrepresented in scrapie) emerged, representing <4 kb from the transcriptome. All contained highly stable regions of secondary structure. The most abundant scrapie-only ros sequence was homologous to a repetitive transposable element (LINE; long interspersed nuclear element). Other ros sequences identified cellular RNA 7SL, clathrin heavy chain, visinin-like protein-1, and three highly specific subregions of ribosomal RNA (ros1-3). The ribosomal ros sequences accurately corresponded to LINE; retrotransposon insertion sites in ribosomal DNA (p<0.01). These differential motifs implicate specific host RNAs in the pathoetiology of the TSEs.
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Abstract
The transmissible spongiform encephalopathies are rapidly progressive and invariably fatal neurodegenerative diseases for which there are no proven efficacious treatments. Many approaches have been undertaken to find ways to prevent, halt, or reverse these prion diseases, with limited success to date. However, as both our understanding of pathogenesis and our ability to detect early disease increases, so do our potential therapeutic targets and our chances of finding effective drugs. There is increasing pressure to find effective decontaminants for blood supplies, as variant Creutzfeldt Jakob Disease (vCJD) has been shown to be transmissible by blood, and to find non-toxic preventative therapies, with ongoing cases of Bovine Spongiform Encephalopathy (BSE) and the spread of Chronic Wasting Disease (CWD). Within the realm of chemotherapeutic approaches, much research has focussed on blocking the conversion of the normal form of prion protein (PrP(c)) to its abnormal counterpart (PrP(res)). Structurally, these chemotherapeutic agents are often polyanionic or polycyclic and may directly bind PrP(c) or PrP(res), or act by redistributing, sequestering, or down-regulating PrP(c), thus preventing its conversion. There are also some polycationic compounds which proport to enhance the clearance of PrP(res). Other targets include accessory molecules such as the laminin receptor precursor which influences conversion, or cell signalling molecules which may be required for pathogenesis. Of recent interest are the possible neuroprotective effects of some drugs. Importantly, there is evidence that combining compounds may provide synergistic responses. This review provides an update on current testing methods, therapeutic targets, and promising candidates for chemical-based therapy.
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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, Hamilton, MT 59840, USA.
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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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66
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Gomes MPB, Millen TA, Ferreira PS, e Silva NLC, Vieira TCRG, Almeida MS, Silva JL, Cordeiro Y. Prion protein complexed to N2a cellular RNAs through its N-terminal domain forms aggregates and is toxic to murine neuroblastoma cells. J Biol Chem 2008; 283:19616-25. [PMID: 18456654 PMCID: PMC2443653 DOI: 10.1074/jbc.m802102200] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Conversion of the cellular prion protein (PrPC) into its altered conformation, PrPSc, is believed to be the major cause of prion diseases. Although PrP is the only identified agent for these diseases, there is increasing evidence that other molecules can modulate the conversion. We have found that interaction of PrP with double-stranded DNA leads to a protein with higher β-sheet content and characteristics similar to those of PrPSc. RNA molecules can also interact with PrP and potentially modulate PrPC to PrPSc conversion or even bind differentially to both PrP isoforms. Here, we investigated the interaction of recombinant murine PrP with synthetic RNA sequences and with total RNA extracted from cultured neuroblastoma cells (N2aRNA). We found that PrP interacts with N2aRNA with nanomolar affinity, aggregates upon this interaction, and forms species partially resistant to proteolysis. RNA does not bind to N-terminal deletion mutants of PrP, indicating that the N-terminal region is important for this process. Cell viability assays showed that only the N2aRNA extract induces PrP-RNA aggregates that can alter the homeostasis of cultured cells. Small RNAs bound to PrP give rise to nontoxic small oligomers. Nuclear magnetic resonance measurements of the PrP-RNA complex revealed structural changes in PrP, but most of its native fold is maintained. These results indicate that there is selectivity in the species generated by interaction with different molecules of RNA. The catalytic effect of RNA on the PrPC→PrPSc conversion depends on the RNA sequence, and small RNA molecules may exert a protective effect.
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Affiliation(s)
- Mariana P B Gomes
- Programa de Biologia Estrutural, Centro Nacional de Ressonância Magnética Nuclear Jiri Jonas, Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, 21491-590 Rio de Janeiro, Brazil
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67
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Intriguing nucleic-acid-binding features of mammalian prion protein. Trends Biochem Sci 2008; 33:132-40. [DOI: 10.1016/j.tibs.2007.11.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/14/2007] [Accepted: 11/26/2007] [Indexed: 11/19/2022]
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69
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Lee KS, Raymond LD, Schoen B, Raymond GJ, Kett L, Moore RA, Johnson LM, Taubner L, Speare JO, Onwubiko HA, Baron GS, Caughey WS, Caughey B. Hemin Interactions and Alterations of the Subcellular Localization of Prion Protein. J Biol Chem 2007; 282:36525-33. [DOI: 10.1074/jbc.m705620200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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70
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Vilette D. Cell models of prion infection. Vet Res 2007; 39:10. [PMID: 18073097 DOI: 10.1051/vetres:2007049] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 09/24/2007] [Indexed: 11/14/2022] Open
Abstract
Due to recent renewal of interest and concerns in prion diseases, a number of cell systems permissive to prion multiplication have been generated in the last years. These include established cell lines, neuronal stem cells and primary neuronal cultures. While most of these models are permissive to experimental, mouse-adapted strains of prions, the propagation of natural field isolates from sheep scrapie and chronic wasting disease has been recently achieved. These models have improved our knowledge on the molecular and cellular events controlling the conversion of the PrP(C) protein into abnormal isoforms and on the cell-to-cell spreading of prions. Infected cultured cells will also facilitate investigations on the molecular basis of strain identity and on the mechanisms that lead to neurodegeneration. The ongoing development of new cell models with improved characteristics will certainly be useful for a number of unanswered critical issues in the prion field.
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Affiliation(s)
- Didier Vilette
- Unité Mixte de Recherche 1225, INRA, ENVT, 31000 Toulouse, France.
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71
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Karpuj MV, Giles K, Gelibter-Niv S, Scott MR, Lingappa VR, Szoka FC, Peretz D, Denetclaw W, Prusiner SB. Phosphorothioate oligonucleotides reduce PrP levels and prion infectivity in cultured cells. Mol Med 2007. [PMID: 17592554 DOI: 10.2119/2006-00073.karpuj] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Prions are composed solely of the disease-causing prion protein (PrPSc) that is formed from the cellular isoform PrPC by a posttranslational process. Here we report that short phosphorothioate DNA (PS-DNA) oligonucleotides diminished the levels of both PrPC and PrPSc in prion-infected neuroblastoma (ScN2a) cells. The effect of PS-DNA on PrP levels was independent of the nucleotide sequence. The effective concentration (EC50) of PS-DNA required to achieve half-maximal diminution of PrPSc was approximately 70 nM, whereas the EC50 of PS-DNA for PrPC was more than 50-fold greater. This finding indicated that diminished levels of PrPSc after exposure to PS-DNA are unlikely to be due to decreased PrPC levels. Bioassays in transgenic mice demonstrated a substantial diminution in the prion infectivity after ScN2a cells were exposed to PS-DNAs. Whether PS-DNA will be useful in the treatment of prion disease in people or livestock remains to be established.
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Affiliation(s)
- Marcela V Karpuj
- Institute for Neurodegenerative Diseases and Department of Neurology, University of California, San Francisco, CA 94143-0518, USA
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72
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Karpuj MV, Giles K, Gelibter-Niv S, Scott MR, Lingappa VR, Szoka FC, Peretz D, Denetclaw W, Prusiner SB. Phosphorothioate oligonucleotides reduce PrP levels and prion infectivity in cultured cells. MOLECULAR MEDICINE (CAMBRIDGE, MASS.) 2007; 13:190-8. [PMID: 17592554 PMCID: PMC1892763 DOI: 10.2119/2006–00073.karpuj] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 02/12/2007] [Indexed: 11/06/2022]
Abstract
Prions are composed solely of the disease-causing prion protein (PrPSc) that is formed from the cellular isoform PrPC by a posttranslational process. Here we report that short phosphorothioate DNA (PS-DNA) oligonucleotides diminished the levels of both PrPC and PrPSc in prion-infected neuroblastoma (ScN2a) cells. The effect of PS-DNA on PrP levels was independent of the nucleotide sequence. The effective concentration (EC50) of PS-DNA required to achieve half-maximal diminution of PrPSc was approximately 70 nM, whereas the EC50 of PS-DNA for PrPC was more than 50-fold greater. This finding indicated that diminished levels of PrPSc after exposure to PS-DNA are unlikely to be due to decreased PrPC levels. Bioassays in transgenic mice demonstrated a substantial diminution in the prion infectivity after ScN2a cells were exposed to PS-DNAs. Whether PS-DNA will be useful in the treatment of prion disease in people or livestock remains to be established.
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Affiliation(s)
- Marcela V Karpuj
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA
| | - Kurt Giles
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA
- Department of Neurology, University of California, San Francisco, CA
| | - Sagit Gelibter-Niv
- Institute of Biochemistry, Food Science and Nutrition Food and Environmental Quality Sciences, The Hebrew University Faculty of Agriculture, Rehovot, Israel
| | - Michael R Scott
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA
- Department of Neurology, University of California, San Francisco, CA
| | | | - Francis C Szoka
- Department of Biopharmaceutical Sciences, University of California, San Francisco, CA
| | - David Peretz
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA
- Department of Neurology, University of California, San Francisco, CA
| | - Wilfred Denetclaw
- Department of Biology, San Francisco State University, San Francisco, CA
| | - Stanley B Prusiner
- Institute for Neurodegenerative Diseases, University of California, San Francisco, CA
- Department of Neurology, University of California, San Francisco, CA
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA
- Address correspondence and reprint requests to: Stanley B Prusiner, Institute for Neurodegenerative Diseases, 513 Parnassus Ave, HSE-774, San Francisco, CA 94143-0518. Phone: 415-476-4482; Fax: 415-476-8386; E-mail:
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73
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Kocisko DA, Bertholet N, Moore RA, Caughey B, Vaillant A. Identification of prion inhibitors by a fluorescence-polarization-based competitive binding assay. Anal Biochem 2007; 363:154-6. [PMID: 17276383 DOI: 10.1016/j.ab.2006.11.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Accepted: 11/05/2006] [Indexed: 11/19/2022]
Affiliation(s)
- David A Kocisko
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA
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74
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Spinner DS, Kascsak RB, Lafauci G, Meeker HC, Ye X, Flory MJ, Kim JI, Schuller-Levis GB, Levis WR, Wisniewski T, Carp RI, Kascsak RJ. CpG oligodeoxynucleotide-enhanced humoral immune response and production of antibodies to prion protein PrPSc in mice immunized with 139A scrapie-associated fibrils. J Leukoc Biol 2007; 81:1374-85. [PMID: 17379700 DOI: 10.1189/jlb.1106665] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Prion diseases are characterized by conversion of the cellular prion protein (PrP(C)) to a protease-resistant conformer, the srapie form of PrP (PrP(Sc)). Humoral immune responses to nondenatured forms of PrP(Sc) have never been fully characterized. We investigated whether production of antibodies to PrP(Sc) could occur in PrP null (Prnp(-/-)) mice and further, whether innate immune stimulation with the TLR9 agonist CpG oligodeoxynucleotide (ODN) 1826 could enhance this process. Whether such stimulation could raise anti-PrP(Sc) antibody levels in wild-type (Prnp(+/+)) mice was also investigated. Prnp(-/-) and Prnp(+/+) mice were immunized with nondenatured 139A scrapie-associated fibrils (SAF), with or without ODN 1826, and were tested for titers of PrP-specific antibodies. In Prnp(-/-) mice, inclusion of ODN 1826 in the immunization regime increased anti-PrP titers more than 13-fold after two immunizations and induced, among others, antibodies to an N-terminal epitope, which were only present in the immune repertoire of mice receiving ODN 1826. mAb 6D11, derived from such a mouse, reacts with the N-terminal epitope QWNK in native and denatured forms of PrP(Sc) and recombinant PrP and exhibits a K(d) in the 10(-)(11) M range. In Prnp(+/+) mice, ODN 1826 increased anti-PrP levels as much as 84% after a single immunization. Thus, ODN 1826 potentiates adaptive immune responses to PrP(Sc) in 139A SAF-immunized mice. These results represent the first characterization of humoral immune responses to nondenatured, infectious PrP(Sc) and suggest methods for optimizing the generation of mAbs to PrP(Sc), many of which could be used for diagnosis and treatment of prion diseases.
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Affiliation(s)
- Daryl S Spinner
- New York State Institute for Basic Research in Development Disabilities, 1050 Forest Hill Rd., Staten Island, NY 10314, USA.
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75
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King DJ, Safar JG, Legname G, Prusiner SB. Thioaptamer interactions with prion proteins: sequence-specific and non-specific binding sites. J Mol Biol 2007; 369:1001-14. [PMID: 17481659 DOI: 10.1016/j.jmb.2007.02.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 02/01/2007] [Accepted: 02/02/2007] [Indexed: 11/19/2022]
Abstract
Binding of nucleic acids to the prion protein (PrP) created a conundrum that required distinguishing between non-specific interactions and biologically important polynucleotides. In the process of developing selective ligands for PrP, we found using a single-stranded DNA thioaptamer library that the binding of thioaptamers to PrP occurs on at least two different sites on the protein. Selection against recombinant (rec) PrP of Syrian hamster (SHa) sequence 90-231 folded into an alpha-helical-rich conformation identified a 12-base consensus sequence within a series of 20 thioaptamers, all of which consist of 40 bases. Each thioaptamer was comprised of both normal and thio-dA modified bases. One thioaptamer designated 97 bound to recSHaPrP with affinity of 0.58(+/-0.1) nM; lower affinities for bovine (Bo), and human (Hu) were found, establishing that binding is dependent on the primary structure of PrP. High affinity binding of thioaptamer 97 to PrP was found to be mediated through the dodecyl sequence GACACAAGCCGA within the consensus region with five critical backbone modifications 5' to each dA residue. A control oligonucleotide with an equivalent number of phosphorothioates to thioaptamer 97 and a scrambled consensus sequence could not distinguish among the three PrP sequences. Control oligonucleotides bearing non-selected sequences bound to PrP at a sequence-independent DNA-binding site. In contrast, the high-affinity binding of thioaptamer 97 to PrP depends on (1) backbone modifications, (2) oligonucleotide sequence, and (3) PrP sequence.
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Affiliation(s)
- David J King
- Institute for Neurodegenerative Diseases, University of California San Francisco, CA 94143-0518, USA
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76
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Abstract
Prions, the infectious agents of transmissible spongiform encephalopathies (TSEs), have defied full characterization for decades. The dogma has been that prions lack nucleic acids and are composed of a pathological, self-inducing form of the host's prion protein (PrP). Recent progress in propagating TSE infectivity in cell-free systems has effectively ruled out the involvement of foreign nucleic acids. However, host-derived nucleic acids or other non-PrP molecules seem to be crucial. Interactions between TSE-associated PrP and its normal counterpart are also pathologically important, so the physiological functions of normal PrP and how they might be corrupted by TSE infections have been the subject of recent research.
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Affiliation(s)
- Byron Caughey
- National Institute of Allergy and Infectious Disease, National Institutes of Health, Rocky Mountain Laboratories, 903 South 4th Street, Hamilton, Montana 59840, USA.
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