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1.
The prion protein (PrP) is implicated in the Transmissible Spongiform Encephalopathies (TSEs), which comprise a group of fatal neurodegenerative diseases affecting humans and other mammals. Conversion of cellular PrP (PrP C) into the scrapie form (PrP Sc) is the hallmark of TSEs. Once formed, PrP Sc aggregates and catalyzes PrP C misfolding into new PrP Sc molecules. Although many compounds have been shown to inhibit the conversion process, so far there is no effective therapy for TSEs. Besides, most of the previously evaluated compounds failed in vivo due to poor pharmacokinetic profiles. In this work we propose a combined in vitro/ in silico approach to screen for active anti-prion compounds presenting acceptable drugability and pharmacokinetic parameters. A diverse panel of aromatic compounds was screened in neuroblastoma cells persistently infected with PrP Sc (ScN2a) for their ability to inhibit PK-resistant PrP (PrP Res) accumulation. From ∼200 compounds, 47 were effective in decreasing the accumulation of PrP Res in ScN2a cells. Pharmacokinetic and physicochemical properties were predicted in silico, allowing us to obtain estimates of relative blood brain barrier permeation and mutagenicity. MTT reduction assays showed that most of the active compounds were non cytotoxic. Compounds that cleared PrP Res from ScN2a cells, were non-toxic in the MTT assay, and presented a good pharmacokinetic profile were investigated for their ability to inhibit aggregation of an amyloidogenic PrP peptide fragment (PrP 109–149). Molecular docking results provided structural models and binding affinities for the interaction between PrP and the most promising compounds. In summary, using this combined in vitro/ in silico approach we have identified new small organic anti-scrapie compounds that decrease the accumulation of PrP Res in ScN2a cells, inhibit the aggregation of a PrP peptide, and possess pharmacokinetic characteristics that support their drugability. These compounds are attractive candidates for prion disease therapy. 相似文献
2.
Prion diseases are characterized by the accumulation of a pathological form of prion protein (PrP Sc), which behaves as an infectious agent. Here we developed an in vitro co-culture system to analyze the PrP Sc transmission from ScN2a cell, which persistently retains PrP Sc, to naïve N2a cell. In this cell-to-cell transmission system, PrP Sc transmitted to recipient N2a cell was able to be detected within 5-7 days. Further characterization showed that higher cell density greatly facilitated the transmission of PrP Sc. This improved in vitro transmission method may become a useful tool for unveiling the molecular mechanism of PrP Sc transmission. 相似文献
3.
Prion diseases are neurodegenerative disorders caused by the accumulation of abnormal prion protein (PrP Sc) in the central nervous system. With the aim of elucidating the mechanism underlying the accumulation and degradation of PrP Sc, we investigated the role of autophagy in its degradation, using cultured cells stably infected with distinct prion strains. The effects of pharmacological compounds that inhibit or stimulate the cellular signal transduction pathways that mediate autophagy during PrP Sc degradation were evaluated. The accumulation of PrP Sc in cells persistently infected with the prion strain Fukuoka-1 (FK), derived from a patient with Gerstmann–Sträussler–Scheinker syndrome, was significantly increased in cultures treated with the macroautophagy inhibitor 3-methyladenine (3MA) but substantially reduced in those treated with the macroautophagy inducer rapamycin. The decrease in FK-derived PrP Sc levels was mediated, at least in part, by the phosphatidylinositol 3-kinase/MEK signalling pathway. By contrast, neither rapamycin nor 3MA had any apparently effect on PrP Sc from either the 22L or the Chandler strain, indicating that the degradation of PrP Sc in host cells might be strain-dependent. 相似文献
4.
mAbs T1 and T2 were established by immunizing PrP gene ablated mice with recombinant MoPrP of residues 121–231. Both mAbs were cross‐reactive with PrP from hamster, sheep, cattle and deer. A linear epitope of mAb T1 was identified at residues 137–143 of MoPrP and buried in PrP C expressed on the cell surface. mAb T1 showed no inhibitory effect on accumulation of PrP Sc in cultured scrapie‐infected neuroblastoma (ScN2a) cells. In contrast, mAb T2 recognized a discontinuous epitope ranged on, or structured by, residues 132–217 and this epitope was exposed on the cell surface PrP C. mAb T2 showed an excellent inhibitory effect on PrP Sc accumulation in vitro at a 50% inhibitory concentration of 0.02 μg/ml (0.14 nM). The scFv form of mAb T2 (scFv T2) was secreted in neuroblastoma (N2a58) cell cultures by transfection through eukaryotic secretion vector. Coculturing of ScN2a cells with scFv T2‐producing N2a58 cells induced a clear inhibitory effect on PrP Sc accumulation, suggesting that scFv T2 could potentially be an immunotherapeutic tool for prion diseases by inhibition of PrP Sc accumulation. 相似文献
5.
The prion diseases occur following the conversion of the cellular prion protein (PrP C) into disease-related isoforms (PrP Sc). In this study, the role of the glycosylphosphatidylinositol (GPI) anchor attached to PrP C in prion formation was examined using a cell painting technique. PrP Sc formation in two prion-infected neuronal cell lines (ScGT1 and ScN2a cells) and in scrapie-infected primary cortical neurons was increased following the introduction of PrP C. In contrast, PrP C containing a GPI anchor from which the sialic acid had been removed (desialylated PrP C) was not converted to PrP Sc. Furthermore, the presence of desialylated PrP C inhibited the production of PrP Sc within prion-infected cortical neurons and ScGT1 and ScN2a cells. The membrane rafts surrounding desialylated PrP C contained greater amounts of sialylated gangliosides and cholesterol than membrane rafts surrounding PrP C. Desialylated PrP C was less sensitive to cholesterol depletion than PrP C and was not released from cells by treatment with glimepiride. The presence of desialylated PrP C in neurons caused the dissociation of cytoplasmic phospholipase A 2 from PrP-containing membrane rafts and reduced the activation of cytoplasmic phospholipase A 2. These findings show that the sialic acid moiety of the GPI attached to PrP C modifies local membrane microenvironments that are important in PrP-mediated cell signaling and PrP Sc formation. These results suggest that pharmacological modification of GPI glycosylation might constitute a novel therapeutic approach to prion diseases. 相似文献
6.
Prion disease is a neurodegenerative disorder with progressive neurologic symptoms and accelerated cognitive decline. The causative protein of prion disease is the prion protein (PrP), and structural transition of PrP from the normal helix rich form (PrPC) to the abnormal β-sheet rich form (PrPSc) occurs in prion disease. While so far numerous therapeutic agents for prion diseases have been developed, none of them are still useful. A fluorinated alcohol, hexafluoro isopropanol (HFIP), is a precursor to the inhalational anesthetic sevoflurane and its metabolites. HFIP is also known as a robust α-helix inducer and is widely used as a solvent for highly aggregated peptides. Here we show that the α-helix-inducing activity of HFIP caused the conformational transformation of the fibrous structure of PrP into amorphous aggregates in vitro. HFIP added to the ScN2a cell medium, which continuously expresses PrPSc, reduced PrPSc protease resistance after 24-h incubation. It was also clarified that ScN2a cells are more susceptible to HFIP than any of the cells being compared. Based on these findings, HFIP is expected to develop as a therapeutic agent for prion disease. 相似文献
7.
BackgroundA hallmark of the prion diseases is the conversion of the host-encoded cellular prion protein (PrP C) into a disease related, alternatively folded isoform (PrP Sc). The accumulation of PrP Sc within the brain is associated with synapse loss and ultimately neuronal death. Novel therapeutics are desperately required to treat neurodegenerative diseases including the prion diseases. Principal FindingsTreatment with glimepiride, a sulphonylurea approved for the treatment of diabetes mellitus, induced the release of PrP C from the surface of prion-infected neuronal cells. The cell surface is a site where PrP C molecules may be converted to PrP Sc and glimepiride treatment reduced PrP Sc formation in three prion infected neuronal cell lines (ScN2a, SMB and ScGT1 cells). Glimepiride also protected cortical and hippocampal neurones against the toxic effects of the prion-derived peptide PrP82–146. Glimepiride treatment significantly reduce both the amount of PrP82–146 that bound to neurones and PrP82–146 induced activation of cytoplasmic phospholipase A 2 (cPLA 2) and the production of prostaglandin E 2 that is associated with neuronal injury in prion diseases. Our results are consistent with reports that glimepiride activates an endogenous glycosylphosphatidylinositol (GPI)-phospholipase C which reduced PrP C expression at the surface of neuronal cells. The effects of glimepiride were reproduced by treatment of cells with phosphatidylinositol-phospholipase C (PI-PLC) and were reversed by co-incubation with p-chloromercuriphenylsulphonate, an inhibitor of endogenous GPI-PLC. ConclusionsCollectively, these results indicate that glimepiride may be a novel treatment to reduce PrP Sc formation and neuronal damage in prion diseases. 相似文献
8.
Prion-infected cells have been used for analyzing the effect of compounds on the formation of abnormal isoform of prion protein (PrP Sc). PrP Sc is usually detected using anti-prion protein (PrP) antibodies after the removal of the cellular isoform of prion protein (PrP C) by proteinase K (PK) treatment. However, it is expected that the PK-sensitive PrP Sc (PrP Sc-sen), which possesses higher infectivity and conversion activity than the PK-resistant PrP Sc (PrP Sc-res), is also digested through PK treatment. To overcome this problem, we established a novel cell-based ELISA in which PrP Sc can be directly detected from cells persistently infected with prions using anti-PrP monoclonal antibody (mAb) 132 that recognizes epitope consisting of mouse PrP amino acids 119–127. The novel cell-based ELISA could distinguish prion-infected cells from prion-uninfected cells without cell lysis and PK treatment. MAb 132 could detect both PrP Sc-sen and PrP Sc-res even if all PrP Sc molecules were not detected. The analytical dynamic range for PrP Sc detection was approximately 1 log. The coefficient of variation and signal-to-background ratio were 7%–11% and 2.5–3.3, respectively, demonstrating the reproducibility of this assay. The addition of a cytotoxicity assay immediately before PrP Sc detection did not affect the following PrP Sc detection. Thus, all the procedures including cell culture, cytotoxicity assay, and PrP Sc detection were completed in the same plate. The simplicity and non-requirement for cell lysis or PK treatment are advantages for the high throughput screening of anti-prion compounds. 相似文献
10.
A hallmark of prion diseases is the conversion of the host-encoded prion protein (PrP C where C is cellular) into an alternatively folded, disease-related isoform (PrP Sc, where Sc is scrapie), the accumulation of which is associated with synapse degeneration and ultimately neuronal death. The formation of PrP Sc is dependent upon the presence of PrP C in specific, cholesterol-sensitive membrane microdomains, commonly called lipid rafts. PrP C is targeted to these lipid rafts because it is attached to membranes via a glycosylphosphatidylinositol anchor. Here, we show that treatment of prion-infected neuronal cell lines (ScN2a, ScGT1, or SMB cells) with synthetic glycosylphosphatidylinositol analogues, glucosamine-phosphatidylinositol (glucosamine-PI) or glucosamine 2- O-methyl inositol octadecyl phosphate, reduced the PrP Sc content of these cells in a dose-dependent manner. In addition, ScGT1 cells treated with glucosamine-PI did not transmit infection following intracerebral injection to mice. Treatment with glucosamine-PI increased the cholesterol content of ScGT1 cell membranes and reduced activation of cytoplasmic phospholipase A 2 (PLA 2), consistent with the hypothesis that the composition of cell membranes affects key PLA 2-dependent signaling pathways involved in PrP Sc formation. The effect of glucosamine-PI on PrP Sc formation was also reversed by the addition of platelet-activating factor. Glucosamine-PI caused the displacement of PrP C from lipid rafts and reduced expression of PrP C at the cell surface, putative sites for PrP Sc formation. We propose that treatment with glucosamine-PI modifies local micro-environments that control PrP C expression and activation of PLA 2 and subsequently inhibits PrP Sc formation. 相似文献
11.
Summary 1. Vaccination-induced anti-prion protein antibodies are presently regarded as a promising approach toward treatment of prion
diseases. Here, we investigated the ability of five peptides corresponding to three different regions of the bovine prion
protein (PrP) to elicit antibodies interfering with PrP Sc propagation in prion-infected cells.
2. Rabbits were immunized with free nonconjugated peptides. Obtained immune sera were tested in enzyme-linked immunosorbent
assay (ELISA) and immunoblot for their binding to recombinant PrP and cell-derived pathogenic isoform (PrP Sc) and normal prion protein (PrP c), respectively. Sera positive in all tests were chosen for PrP Sc inhibition studies in cell culture.
3. All peptides induced anti-peptide antibodies, most of them reacting with recombinant PrP. Moreover, addition of the serum
specific to peptide 95–123 led to a transient reduction of PrP Sc levels in persistently prion-infected cells.
4. Thus, anti-PrP antibodies interfering with PrP Sc propagation were induced with a prion protein peptide nonconjugated to a protein carrier. These results point to the potential
application of the nonconjugated peptide 95–123 for the treatment of prion diseases. 相似文献
12.
Limited information is available about conformational differences between the abnormal isoform of prion protein (PrP Sc) and cellular prion protein (PrP C) under native conditions. To clarify conformational differences between these two isoforms, PrP‐deficient mice were immunized with brain homogenates of normal and scrapie‐infected animals. All mice generated anti‐PrP antibodies. Peptide array analysis of these serum samples revealed a distinctive epitope of PrP Sc consisting of QGSPGGN (PrP41–47) at the N‐terminus. This study demonstrated a conformational dissimilarity at the N‐terminus between PrP Sc and PrP C, a finding that may provide novel information about conformational features of PrP Sc. 相似文献
13.
Prions are infectious agents that cause the inevitably fatal transmissible spongiform encephalopathy (TSE) in animals and humans 9,18. The prion protein has two distinct isoforms, the non-infectious host-encoded protein (PrP C) and the infectious protein (PrP Sc), an abnormally-folded isoform of PrP C 8.One of the challenges of working with prion agents is the long incubation period prior to the development of clinical signs following host inoculation 13. This traditionally mandated long and expensive animal bioassay studies. Furthermore, the biochemical and biophysical properties of PrP Sc are poorly characterized due to their unusual conformation and aggregation states.PrP Sc can seed the conversion of PrP C to PrP Scin vitro14. PMCA is an in vitro technique that takes advantage of this ability using sonication and incubation cycles to produce large amounts of PrP Sc, at an accelerated rate, from a system containing excess amounts of PrP C and minute amounts of the PrP Sc seed 19. This technique has proven to effectively recapitulate the species and strain specificity of PrP Sc conversion from PrP C, to emulate prion strain interference, and to amplify very low levels of PrP Sc from infected tissues, fluids, and environmental samples 6,7,16,23 .This paper details the PMCA protocol, including recommendations for minimizing contamination, generating consistent results, and quantifying those results. We also discuss several PMCA applications, including generation and characterization of infectious prion strains, prion strain interference, and the detection of prions in the environment. 相似文献
14.
Prion proteins (PrPs) cause prion diseases, such as bovine spongiform encephalopathy. The conversion of a normal cellular form (PrP C) of PrP into an abnormal form (PrP Sc) is thought to be associated with the pathogenesis. An RNA aptamer that tightly binds to and stabilizes PrP C is expected to block this conversion and to thereby prevent prion diseases. Here, we show that an RNA aptamer comprising only 12 residues, r(GGAGGAGGAGGA) (R12), reduces the PrP Sc level in mouse neuronal cells persistently infected with the transmissible spongiform encephalopathy agent. Nuclear magnetic resonance analysis revealed that R12, folded into a unique quadruplex structure, forms a dimer and that each monomer simultaneously binds to two portions of the N-terminal half of PrP C, resulting in tight binding. Electrostatic and stacking interactions contribute to the affinity of each portion. Our results demonstrate the therapeutic potential of an RNA aptamer as to prion diseases. 相似文献
15.
ABSTRACTA major unsolved issue of prion biology is the existence of multiple strains with distinct phenotypes and this strain phenomenon is postulated to be associated with the conformational diversity of the abnormal prion protein (PrP Sc). Real-time quaking-induced conversion (RT-QUIC) assay that uses Escherichia coli-derived recombinant prion protein (rPrP) for the sensitive detection of PrP Sc results in the formation of rPrP-fibrils seeded with various strains. We demonstrated that there are differences in the secondary structures, especially in the β-sheets, and conformational stability between 2 rPrP-fibrils seeded with either Chandler or 22L strains in the first round of RT-QUIC. In particular, the differences in conformational properties of these 2 rPrP-fibrils were common to those of the original PrP Sc. However, the strain specificities of rPrP-fibrils seen in the first round were lost in subsequent rounds. Instead, our findings suggest that nonspecific fibrils became the major species, probable owing to their selective growth advantage in the RT-QUIC. This study shows that at least some strain-specific conformational properties of the original PrP Sc can be transmitted to rPrP-fibrils in vitro, but further conservation appears to require unknown cofactors or environmental conditions or both. 相似文献
16.
We identified the 37kDa/67kDa laminin receptor (LRP/LR) as a cell surface receptor for the cellular prion protein (PrP c) and the infectious prion protein (PrP Sc). Recently, we showed that anti-LRP/LR antibody W3 cured scrapie infected N2a cells. Here, we demonstrate that W3 delivered by passive immunotransfer into C57BL/6 mice reduced the PrP Sc content in the spleen significantly by 66%, demonstrating an impairment of the peripheral PrP Sc propagation. In addition, we observed a 1.8-fold increase in survival of anti-LRP/LR antibody W3 treated mice (mean survival of 31 days) compared to preimmune serum treated control animals (mean survival of 17 days). We conclude that the significant effect of anti-LRP/LR antibody W3 on the reduction of peripheral PrP Sc propagation might be due to the blockage of the prion receptor LRP/LR which is required, as previously shown in vitro, for PrP Sc propagation in vivo.Key Words: 37kDa/67kDa laminin receptor, LRP/LR, prion, PrP, TSE-therapy 相似文献
17.
Transmissible spongiform encephalopathies (TSEs) or prion diseases are characterized by the accumulation of an aggregated isoform of the prion protein (PrP). This pathological isoform, termed PrP Sc, appears to be the primary component of the TSE infectious agent or prion. However, it is not clear to what extent other protein cofactors may be involved in TSE pathogenesis or whether there are PrP Sc‐associated proteins which help to determine TSE strain‐specific disease phenotypes. We enriched PrP Sc from the brains of mice infected with either 22L or Chandler TSE strains and examined the protein content of these samples using nanospray LC‐MS/MS. These samples were compared with “mock” PrP Sc preparations from uninfected brains. PrP was the major component of the infected samples and ferritin was the most abundant impurity. Mock enrichments contained no detectable PrP but did contain a significant amount of ferritin. Of the total proteins identified, 32% were found in both mock and infected samples. The similarities between PrP Sc samples from 22L and Chandler TSE strains suggest that the non‐PrP Sc protein components found in standard enrichment protocols are not strain specific. 相似文献
18.
Prions are infectious proteins that possess multiple self-propagating structures. The information for strains and structural specific barriers appears to be contained exclusively in the folding of the pathological isoform, PrP Sc. Many recent studies determined that de novo prion strains could be generated in vitro from the structural conversion of recombinant (rec) prion protein (PrP) into amyloidal structures. Our aim was to elucidate the conformational diversity of pathological recPrP amyloids and their biological activities, as well as to gain novel insights in characterizing molecular events involved in mammalian prion conversion and propagation. To this end we generated infectious materials that possess different conformational structures. Our methodology for the prion conversion of recPrP required only purified rec full-length mouse (Mo) PrP and common chemicals. Neither infected brain extracts nor amplified PrP Sc were used. Following two different in vitro protocols recMoPrP converted to amyloid fibrils without any seeding factor. Mouse hypothalamic GT1 and neuroblastoma N2a cell lines were infected with these amyloid preparations as fast screening methodology to characterize the infectious materials. Remarkably, a large number of amyloid preparations were able to induce the conformational change of endogenous PrP C to harbor several distinctive proteinase-resistant PrP forms. One such preparation was characterized in vivo habouring a synthetic prion with novel strain specified neuropathological and biochemical properties. 相似文献
19.
Aberrant self-assembly, induced by structural misfolding of the prion proteins, leads to a number of neurodegenerative disorders. In particular, misfolding of the mostly α-helical cellular prion protein (PrP C) into a β-sheet-rich disease-causing isoform (PrP Sc) is the key molecular event in the formation of PrP Sc aggregates. The molecular mechanisms underlying the PrP C-to-PrP Sc conversion and subsequent aggregation remain to be elucidated. However, in persistently prion-infected cell-culture models, it was shown that treatment with monoclonal antibodies against defined regions of the prion protein (PrP) led to the clearing of PrP Sc in cultured cells. To gain more insight into this process, we characterized PrP-antibody complexes in solution using a fast protein liquid chromatography coupled with small-angle x-ray scattering (FPLC-SAXS) procedure. High-quality SAXS data were collected for full-length recombinant mouse PrP [denoted recPrP(23–230)] and N-terminally truncated recPrP(89–230), as well as their complexes with each of two Fab fragments (HuM-P and HuM-R1), which recognize N- and C-terminal epitopes of PrP, respectively. In-line measurements by fast protein liquid chromatography coupled with SAXS minimized data artifacts caused by a non-monodispersed sample, allowing structural analysis of PrP alone and in complex with Fab antibodies. The resulting structural models suggest two mechanisms for how these Fabs may prevent the conversion of PrP C into PrP Sc. 相似文献
20.
Prion diseases are fatal neurodegenerative disorders, which are not curable and no effective treatment exists so far. The major neuropathological change in diseased brains is the conversion of the normal cellular form of the prion protein PrPc C into a disease-associated isoform PrP Sc. PrP Sc accumulates into multimeres and fibrillar aggregates, which leads to the formation of amyloid plaques. Increasing evidence indicates a fundamental role of PrP Sc species and its aggregation in the pathogenesis of prion diseases, which initiates the pathological cascade and leads to neurodegeneration accompanied by spongiform changes. In search of compounds that have the potential to interfere with PrP Sc formation and propagation, we used a cell based assay for the screening of potential aggregation inhibitors. The assay deals with a permanently prion infected cell line that was adapted for a high-throughput screening of a compound library composed of 10,000 compounds (DIVERset 2, ChemBridge). 相似文献
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