Spongiform encephalopathy in transgenic mice expressing a point mutation in the β2-α2 loop of the prion protein.
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ABSTRACT:
SUBMITTER: Sigurdson CJ
PROVIDER: S-EPMC3205959 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The bovine-porcine species barrier to bovine spongiform encephalopathy (BSE) infection was explored by generating transgenic mouse lines expressing the porcine prion protein (PrP) gene. All of the porcine transgenic (poTg) mice showed clinical signs of BSE after intracerebral inoculation with a high-titer BSE inoculum. The protease-resistant PrP (PrP(res)) was detected in 14% (3 of 22) of the BSE-infected poTg mice by immunohistochemical or immunoblot analysis. Despite being able to infect 42% (5 of 12) of control mice, a low-dose BSE inoculum failed to penetrate the species barrier in our poTg mouse model. The findings of these infectivity studies suggest that there is a strong species barrier between cows and pigs. However, after second-passage infection of poTg mice using brain homogenates of BSE-inoculated mice scoring negative for the incoming prion protein as inoculum, it was possible to detect the presence of the infectious agent. Thus, porcine-adapted BSE inocula were efficient at infecting poTg mice, giving rise to an incubation period substantially reduced from 300 to 177 d after inoculation and to the presence of PrP(res) in 100% (21 of 21) of the mice. We were therefore able to conclude that initial exposure to the bovine prion may lead to subclinical infection such that brain homogenates from poTg mice classified as uninfected on the basis of the absence of PrP(res) are infectious when used to reinoculate poTg mice. Collectively, our findings suggest that these poTg mice could be used as a sensitive bioassay model for prion detection in pigs.
| S-EPMC6729370 | biostudies-literature
Project description:Chronic wasting disease (CWD) is a transmissible, fatal prion disease of cervids and is largely confined to North America. The origin of CWD continues to pose a conundrum: does the disease arise spontaneously or result from some other naturally occurring reservoir? To address whether prions from sheep might be able to cause disease in cervids, we inoculated mice expressing the elk prion protein (PrP) transgene [Tg(ElkPrP) mice] with two scrapie prion isolates. The SSBP/1 scrapie isolate transmitted disease to Tg(ElkPrP) mice with a median incubation time of 270 days, but a second isolate failed to produce neurological dysfunction in these mice. Although prions from cattle with bovine spongiform encephalopathy (BSE) did not transmit to the Tg(ElkPrP) mice, they did transmit after being passaged through sheep. In Tg(ElkPrP) mice, the sheep-passaged BSE prions exhibited an incubation time of approximately 300 days. SSBP/1 prions produced abundant deposits of the disease-causing PrP isoform, denoted PrP(Sc), in the cerebellum and pons of Tg(ElkPrP) mice, whereas PrP(Sc) accumulation in Tg mice inoculated with sheep-passaged BSE prions was confined to the deep cerebellar nuclei, habenula and the brainstem. The susceptibility of 'cervidized' mice to 'ovinized' prions raises the question about why CWD has not been reported in other parts of the world where cervids and scrapie-infected sheep coexist.
| S-EPMC2804060 | biostudies-literature
Project description:In humans, insert mutations within the repetitive octapeptide region of the prion protein gene (Prnp) are often associated with familial spongiform encephalopathies. In this study, transgenic mice expressing bovine PrP (boTg mice) bearing an additional octapeptide insertion to the wild type (seven octapeptide repeats instead of six) showed an altered course of bovine spongiform encephalopathy (BSE) infection, reflected as reduced incubation times when compared with boTg mice expressing similar levels of the wild-type six-octapeptide protein. In both boTg mouse lines (bo6ORTg and bo7ORTg), incubation times were affected drastically depending on transgene expression levels and the inoculum used. In accordance with the lack of an interspecies barrier to BSE infection, we detected the typical signs of CNS spongiform degeneration by histopathological analysis and the presence of the bovine prion PrP(res) by Western blot or immunohistochemical analyses. When 7OR-PrP(res) was propagated in bo7ORTg mice, a similar earlier onset of clinical signs was observed compared with bo6ORTg mice. Proteins PrP(C) and PrP(res) containing seven octapeptides (7OR-PrP(C) and 7OR-PrP(res)) showed similar protease sensitivity and insolubility in nondenaturing detergents to homologous 6OR-PrP(C) and 6OR-PrP(res). In addition, bo7ORTg mice showed a higher sensitivity than bo6ORTg mice for detecting prion infection in specimens previously diagnosed as negative by conventional biochemical techniques. In the absence of clinical signs of disease, 7OR-PrP(res) could be detected as early as 120 d after inoculation by immunohistochemical and Western blot analyses. These findings may help us improve the current mouse bioassays and understand the role of the octapeptide repeat region in susceptibility to disease.
| S-EPMC6730430 | biostudies-literature
Project description:Prions cause neurodegenerative diseases for which no cure exists. Despite decades of research activities the function of the prion protein (PrP) in mammalians is not known. Moreover, little is known on the molecular mechanisms of the self-assembly of the PrP from its monomeric state (cellular PrP, PrP(C)) to the multimeric state. The latter state includes the toxic species (scrapie PrP, PrP(Sc)) knowledge of which would facilitate the development of drugs against prion diseases. Here we analyze the role of a tyrosine residue (Y169) which is strictly conserved in mammalian PrPs. Nuclear magnetic resonance (NMR) spectroscopy studies of many mammalian PrP(C) proteins have provided evidence of a conformational equilibrium between a 3(10)-helical turn and a type I β turn conformation in the β2-α2 loop (residues 165-175). In vitro cell-free experiments of the seeded conversion of PrP(C) indicate that non-aromatic residues at position 169 reduce the formation of proteinase K-resistant PrP. Recent molecular dynamics (MD) simulations of monomeric PrP and several single-point mutants show that Y169 stabilizes the 3(10)-helical turn conformation more than single-point mutants at position 169 or residues in contact with it. In the 3(10)-helical turn conformation the hydrophobic and aggregation-prone segment 169-YSNQNNF-175 is buried and thus not-available for self-assembly. From the combined analysis of simulation and experimental results it emerges that Y169 is an aggregation gatekeeper with a twofold role. Mutations related to 3 human prion diseases are interpreted on the basis of the gatekeeper role in the monomeric state. Another potential role of the Y169 side chain is the stabilization of the ordered aggregates, i.e., reduction of frangibility of filamentous protofibrils and fibrils, which is likely to reduce the generation of toxic species.
| S-EPMC4964861 | biostudies-literature
Project description:BackgroundMutations in the cellular prion protein associated to familial prion disorders severely increase the likelihood of its misfolding into pathogenic conformers. Despite their postulation as incompatible elements with the native fold, these mutations rarely modify the native state structure. However they variably have impact on the thermodynamic stability and metabolism of PrP(C) and on the properties of PrP(Sc) aggregates. To investigate whether the pathogenic mutations affect the dynamic properties of the HuPrP(125-229) α-fold and find possible common patterns of effects that could help in prophylaxis we performed a dynamic diagnosis of ten point substitutions.Methodology/principal findingsUsing all-atom molecular dynamics simulations and novel analytical tools we have explored the effect of D178N, V180I, T183A, T188K, E196K, F198S, E200K, R208H, V210I and E211Q mutations on the dynamics of HuPrP(125-228) α-fold. We have found that while preserving the native state, all mutations produce dynamic changes which perturb the coordination of the α2-α3 hairpin to the rest of the molecule and cause the reorganization of the patches for intermolecular recognition, as the disappearance of those for conversion inhibitors and the emergence of an interaction site at the β2-α2 loop region.Conclusions/significanceOur results suggest that pathogenic mutations share a common pattern of dynamical alterations that converge to the conversion of the β2-α2 loop into an interacting region that can be used as target for interference treatments in genetic diseases.
| S-EPMC3084259 | biostudies-literature
Project description:The β2-α2 loop of PrP(C) is a key modulator of disease-associated prion protein misfolding. Amino acids that differentiate mouse (Ser169, Asn173) and deer (Asn169, Thr173) PrP(C) appear to confer dramatically different structural properties in this region and it has been suggested that amino acid sequences associated with structural rigidity of the loop also confer susceptibility to prion disease. Using mouse recombinant PrP, we show that mutating residue 173 from Asn to Thr alters protein stability and misfolding only subtly, whilst changing Ser to Asn at codon 169 causes instability in the protein, promotes oligomer formation and dramatically potentiates fibril formation. The doubly mutated protein exhibits more complex folding and misfolding behaviour than either single mutant, suggestive of differential effects of the β2-α2 loop sequence on both protein stability and on specific misfolding pathways. Molecular dynamics simulation of protein structure suggests a key role for the solvent accessibility of Tyr168 in promoting molecular interactions that may lead to prion protein misfolding. Thus, we conclude that 'rigidity' in the β2-α2 loop region of the normal conformer of PrP has less effect on misfolding than other sequence-related effects in this region.
| S-EPMC4614821 | biostudies-literature
Project description:AimsThe amino acid sequence of prion protein (PrP) is a key determinant in the transmissibility of prion diseases. While PrP sequence is highly conserved among mammalian species, minor changes in the PrP amino acid sequence may confer alterations in the transmissibility of prion diseases. Classical bovine spongiform encephalopathy (C-BSE) is the only zoonotic prion strain reported to date causing variant Creutzfeldt-Jacob disease (vCJD) in humans, although experimental transmission points to atypical L-BSE and some classical scrapie isolates as also zoonotic. The precise molecular elements in the human PrP sequence that limit the transmissibility of prion strains such as sheep/goat scrapie or cervid chronic wasting disease (CWD) are not well known.MethodsThe transmissibility of a panel of diverse prions from different species was compared in transgenic mice expressing either wild-type human PrPC (MDE-HuTg340) or a mutated human PrPC harbouring Val166 -Gln168 amino acid changes (VDQ-HuTg372) in the β2-α2 loop instead of Met166 -Glu168 wild-type variants.ResultsVDQ-HuTg372 mice were more susceptible to prions than MDE-HuTg340 mice in a strain-dependent manner.ConclusionsMet166 -Glu168 amino acid residues present in wild-type human PrPC are molecular determinants that limit the propagation of most prion strains assayed in the human PrP context.
| S-EPMC8247420 | biostudies-literature
Project description:Two distinct forms of atypical bovine spongiform encephalopathies (H-BSE and L-BSE) can be distinguished from classical (C-) BSE found in cattle based on biochemical signatures of disease-associated prion protein (PrPSc). H-BSE is transmissible to wild-type mice-with infected mice showing a long survival period that is close to their normal lifespan-but not to hamsters. Therefore, rodent-adapted H-BSE with a short survival period would be useful for analyzing H-BSE characteristics. In this study, we investigated the transmissibility of H-BSE to hamster prion protein transgenic (TgHaNSE) mice with long survival periods. Although none of the TgHaNSE mice manifested the disease during their lifespan, PrPSc accumulation was observed in some areas of the brain after the first passage. With subsequent passages, TgHaNSE mice developed the disease with a mean survival period of 220 days. The molecular characteristics of proteinase K-resistant PrPSc (PrPres) in the brain were identical to those observed in first-passage mice. The distribution of immunolabeled PrPSc in the brains of TgHaNSE mice differed between those infected with H-BSE as compared to C-BSE or L-BSE, and the molecular properties of PrPres in TgHaNSE mice infected with H-BSE differed from those of the original isolate. The strain-specific electromobility, glycoform profiles, and proteolytic cleavage sites of H-BSE in TgHaNSE mice were indistinguishable from those of C-BSE, in which the diglycosylated form was predominant. These findings indicate that strain-specific pathogenic characteristics and molecular features of PrPres in the brain are altered during cross-species transmission. Typical H-BSE features were restored after back passage from TgHaNSE to bovinized transgenic mice, indicating that the H-BSE strain was propagated in TgHaNSE mice. This could result from the overexpression of the hamster prion protein.
| S-EPMC4605493 | biostudies-literature
Project description:To date, bovine spongiform encephalopathy (BSE) and its human counterpart, variant Creutzfeldt-Jakob disease, have been associated with a single prion strain. This strain is characterised by a unique and remarkably stable biochemical profile of abnormal protease-resistant prion protein (PrP(res)) isolated from brains of affected animals or humans. However, alternate PrP(res) signatures in cattle have recently been discovered through large-scale screening. To test whether these also represent separate prion strains, we inoculated French cattle isolates characterised by a PrP(res) of higher apparent molecular mass--called H-type--into transgenic mice expressing bovine or ovine PrP. All mice developed neurological symptoms and succumbed to these isolates, showing that these represent a novel strain of infectious prions. Importantly, this agent exhibited strain-specific features clearly distinct from that of BSE agent inoculated to the same mice, which were retained on further passage. Moreover, it also differed from all sheep scrapie isolates passaged so far in ovine PrP-expressing mice. Our findings therefore raise the possibility that either various prion strains may exist in cattle, or that the BSE agent has undergone divergent evolution in some animals.
| S-EPMC1617128 | biostudies-literature
Project description:The H-type of atypical bovine spongiform encephalopathy (H-BSE) was serially passaged in bovinized transgenic (TgBoPrP) mice. At the fourth passage, most challenged mice showed a typical H-BSE phenotype with incubation periods of 223 ± 7.8 days. However, a different phenotype of BSE prion with shorter incubation periods of 109 ± 4 days emerged in a minor subset of the inoculated mice. The latter showed distinct clinical signs, brain pathology, and abnormal prion protein profiles as compared to H-BSE and other known BSE strains in mice. This novel prion was transmitted intracerebrally to cattle, with incubation periods of 14.8 ± 1.5 months, with phenotypes that differed from those of other bovine prion strains. These data suggest that intraspecies transmission of H-BSE in cattle allows the emergence of a novel BSE strain. Therefore, the continuation of feed ban programs may be necessary to exclude the recycling of H-BSE prions, which appear to arise spontaneously, in livestock. Such measures should help to reduce the risks from both novel and known strains of BSE.
| S-EPMC4780101 | biostudies-literature