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Introduction: Gerstmann-Sträussler-Scheinker disease (GSS) is an autosomal-dominant inherited prion disease most often associated with the human prion protein gene (PRNP)-P102L mutation. Although patients manifest considerable phenotypic heterogeneity, the involvement of the nigrostriatal system has not been well-studied., Methods: We performed dopamine transporter single-photon emission computed tomography (DAT-SPECT) using 123 I-ioflupane to investigate the nigrostriatal system function in nine patients with the PRNP-P102L mutation. We also examined the pathological findings in another patient whose predominant feature was ataxia and who died 5 years after disease onset., Results: Striatum uptake of 123 I-ioflupane indicated by specific binding ratio (SBR) values was significantly reduced in two patients. The DAT-SPECT examination was performed 6 months after disease onset in one of these patients who manifested rapidly developing cognitive decline mimicking Creutzfeldt-Jakob disease. DAT-SPECT was also performed 9 years after disease onset in another patient who manifested the conventional features of GSS involving ataxia and dementia in the initial phase but showed akinetic mutism at the examination time. Another patient examined 2 years after disease onset who predominantly manifested ataxia showed marginally abnormal SBR values. An autopsy case showed moderate neuronal loss in the substantia nigra, and the degree of neuronal loss was similar in most other parts of the brain., Conclusion: Nigrostriatal system involvement may occur in patients with GSS associated with the PRNP-P102L mutation, even though parkinsonism is not the predominant feature., Competing Interests: Declaration of competing interest The authors declare that they have no financial and personal relationships with other people or organizations that could inappropriately influence (bias) their work., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Many neurodegenerative diseases feature misfolded proteins that propagate via templated conversion of natively folded molecules. However, crucial questions about how such prion-like conversion occurs and what drives it remain unsolved, partly because technical challenges have prevented direct observation of conversion for any protein. We observed prion-like conversion in single molecules of superoxide dismutase-1 (SOD1), whose misfolding is linked to amyotrophic lateral sclerosis. Tethering pathogenic misfolded SOD1 mutants to wild-type molecules held in optical tweezers, we found that the mutants vastly increased misfolding of the wild-type molecule, inducing multiple misfolded isoforms. Crucially, the pattern of misfolding was the same in the mutant and converted wild-type domains and varied when the misfolded mutant was changed, reflecting the templating effect expected for prion-like conversion. Ensemble measurements showed decreased enzymatic activity in tethered heterodimers as conversion progressed, mirroring the single-molecule results. Antibodies sensitive to disease-specific epitopes bound to the converted protein, implying that conversion produced disease-relevant misfolded conformers., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Prion diseases are a family of infectious amyloid diseases affecting human and animals. Prion propagation in transmissible spongiform encephalopathies is associated with the unfolding and conversion of normal cellular prion protein into its pathogenic scrapie form. Understanding the fundamentals of prion protein aggregation caused by mutations is crucial to unravel the pathology of prion diseases. To help understand the contributions of individual residues to the stability of the human prion protein, we have carried out free energy simulations based on atomistic molecular dynamics trajectories. We focus on Met → Ala mutations at positions 205, 206 and 213, which are mostly buried residues located on helix 3 of the protein. The simulations predicted that all three mutations destabilize the prion protein. Changes in unfolding free energy upon mutation, ∆∆G, are 3.10 ± 0.79, 2.00 ± 0.26 and 3.06 ± 0.66 kcal/mol for M205A, M206A and M213A, respectively, in excellent agreement with the corresponding experimental values of 3.09 ± 0.28, 1.50 ± 0.34 and 3.12 ± 0.27 kcal/mol [T. Hart et al. (2009) PNAS 106, 5651-5656]. Component analysis indicates that the major contributions to the loss of protein stability arise from van der Waals interactions for the M205A and M206A mutations, and from van der Waals and covalent energy terms for M213A. Interestingly, while free energy contributions from a majority of residues neighboring the mutation sites tend to stabilize the wild type, there are a few residues stabilizing the mutant side chains. Our results show that this approach to free energy calculation can be very useful for understanding the detailed mechanism of human prion protein stability., (Copyright © 2021. Published by Elsevier B.V.)

Prions are self-perpetuating, alternative protein conformations associated with neurological diseases and normal cellular functions. Saccharomyces cerevisiae contains many endogenous prions, providing a powerful system to study prionization. Previously, we demonstrated that Swi1, a component of the SWI/SNF chromatin-remodeling complex, can form the prion [ SWI + ]. A small region, Swi1 1-38 , with a unique amino acid composition of low complexity, acts as a prion domain and supports [ SWI + ] propagation. Here, we further examine Swi1 1-38 through site-directed mutagenesis. We found that mutations of the two phenylalanine residues or the threonine tract inhibit Swi1 1-38 aggregation. In addition, mutating both phenylalanines can abolish de novo prion formation by Swi1 1-38 , whereas mutating only one phenylalanine does not. Replacement of half of or the entire eight-threonine tract with alanines has the same effect, possibly disrupting a core region of Swi1 1-38 aggregates. We also show that Swi1 1-38 and its prion-fold-maintaining mutants form high-molecular-weight, SDS-resistant aggregates, whereas the double-phenylalanine mutants eliminate these protein species. These results indicate the necessity of the large hydrophobic residues and threonine tract in Swi1 1-38 in prionogenesis, possibly acting as important aggregable regions. Our findings thus highlight the importance of specific amino acid residues in the Swi1 prion domain in prion formation and maintenance.

The yeast prion [URE3] propagates as a misfolded amyloid form of the Ure2 protein. Propagation of amyloid-based yeast prions requires protein quality control (PQC) factors, and altering PQC abundance or activity can cure cells of prions. Yeast antiprion systems composed of PQC factors act at normal abundance to restrict establishment of the majority of prion variants that arise de novo While these systems are well described, how they or other PQC factors interact with prion proteins remains unclear. To gain insight into such interactions, we identified mutations outside the Ure2 prion-determining region that destabilize [URE3]. Despite residing in the functional domain, 16 of 17 mutants retained Ure2 activity. Four characterized mutations caused rapid loss of [URE3] yet allowed [URE3] to propagate under prion-selecting conditions. Two sensitized [URE3] to Btn2, Cur1, and Hsp42, but in different ways. Two others reduced amyloid formation in vitro Of these, one impaired prion replication and the other apparently impaired transmission. Thus, widely dispersed sites outside a prion's amyloid-forming region can contribute to prion character, and altering such sites can disrupt prion propagation by altering interactions with PQC factors.

Several RNA-binding proteins undergo reversible liquid-liquid phase transitions, which, in pathological conditions, might evolve into transitions to solid-state phases, giving rise to amyloid structures. Amyloidogenic and prion-like proteins, such as the tumor suppressor protein p53 and the mammalian prion protein (PrP), bind RNAs specifically or nonspecifically, resulting in changes in their propensity to undergo aggregation. Mutant p53 aggregation seems to play a crucial role in cancer through loss of function, negative dominance and gain of function. PrP conversion modulated by RNA results in highly toxic aggregates. Here, we review data on the modulatory action of RNAs on the aggregation of both proteins., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The dynamic nature of the tau protein under physiological conditions is likely to be critical for it to perform its diverse functions inside a cell. Under some conditions, this intrinsically disordered protein assembles into pathogenic aggregates that are self-perpetuating, toxic and infectious in nature. The role of liquid-liquid phase separation in the initiation of the aggregation reaction remains to be delineated. Depending on the nature of the aggregate, its structure, and its localization, neurodegenerative disorders with diverse clinical features are manifested. The prion-like mechanism by which these aggregates propagate and spread across the brain is not well understood. Various factors (PTMs, mutations) have been strongly associated with the pathological aggregates of tau. However, little is known about how these factors modulate the pathological properties linked to aggregation. This review describes the current progress towards understanding the mechanism of propagation of tau aggregates., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Genetic screens using Saccharomyces cerevisiae have identified an array of Hsp40 (Ydj1p) J-domain mutants that are impaired in the ability to cure the yeast [URE3] prion through disrupting functional interactions with Hsp70. However, biochemical analysis of some of these Hsp40 J-domain mutants has so far failed to provide major insight into the specific functional changes in Hsp40-Hsp70 interactions. To explore the detailed structural and dynamic properties of the Hsp40 J-domain, 20 ns molecular dynamic simulations of 4 mutants (D9A, D36A, A30T, and F45S) and wild-type J-domain were performed, followed by Hsp70 docking simulations. Results demonstrated that although the Hsp70 interaction mechanism of the mutants may vary, the major structural change was targeted to the critical HPD motif of the J-domain. Our computational analysis fits well with previous yeast genetics studies regarding highlighting the importance of J-domain function in prion propagation. During the molecular dynamics simulations several important residues were identified and predicted to play an essential role in J-domain structure. Among these residues, Y26 and F45 were confirmed, using both in silico and in vivo methods, as being critical for Ydj1p function.

Among genetically determined neurodegenerative diseases, the dominantly inherited prion protein cerebral amyloidoses are characterized by deposition of amyloid in cerebral parenchyma or blood vessels. Among them, Gerstmann-Sträussler-Scheinker disease has been the first to be described. Their clinical, neuropathologic, and molecular phenotypes are distinct from those observed in Creutzfeldt-Jakob disease (CJD) and related spongiform encephalopathies. It is not understood why specific mutations in the prion protein gene (PRNP) cause cerebral amyloidosis and others cause CJD. A significant neurobiologic event in these amyloidoses is the frequent coexistence of prion amyloid with tau neurofibrillary pathology, a phenomenon suggesting that similar pathogenetic mechanisms may be shared among different diseases in the sequence of events occurring in the cascade from amyloid formation to tau aggregation. This chapter describes the clinical, neuropathologic, and biochemical phenotypes associated with each of the PRNP mutations causing an inherited cerebral amyloidosis and emphasizes the variability of phenotypes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Genetic Creutzfeldt-Jakob disease (CJD) is associated with mutations in the human PrP gene (PRNP) on chromosome 20p12-pter. Pathogenic mutations have been identified in 10-15% of all CJD patients, who often have a family history of autosomal-dominant pattern of inheritance and variable penetrance. However, the use of genetic tests implemented by surveillance networks all over the world increasingly identifies unexpectedly PRNP mutations in persons apparently presenting with a sporadic form of CJD. A high phenotypic variability was reported in genetic prion diseases, which partly overlap with the features of sporadic CJD. Here we review recent advances on the epidemiologic, clinical, and neuropathologic features of cases that phenotypically resemble CJD linked to point and insert mutations of the PRNP gene. Multidisciplinary studies are still required to understand the phenotypic spectrum, penetrance, and significance of PRNP mutations., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Studies of the ovine prion-related protein (testis-specific) gene (PRNT), including studies of genetic diversity, have highlighted its potential relationship to scrapie infection and economically important ovine traits. PRNT was previously reported to be highly polymorphic in Portuguese sheep. To characterize genetic polymorphisms in this gene in Asian sheep, a direct sequencing method was used to detect polymorphic loci in PRNT in 285 individual sheep from four Chinese and one Mongolian breeds. Seven SNP variants in PRNT were identified, including three novel variants (g.93G>A, g.162G>T, and g.190A>G) and four previously reported variants (g.17 C>T, g.112G>C, g.129C>T, and g.144A>G). In the five breeds that we analyzed, the mutation frequencies of g.190A>G in Lanzhou Fat-tail sheep (LFTS) and g.129C>T in the other four varieties were high (F>0.5). Moreover, thirteen different haplotypes that had a comparable distribution in the tested breeds were also identified; 'C-G-G-C-A-G-A' occurred at the highest frequency in the five sheep breeds. Additionally, we previously explored the significance of relationships between polymorphisms in PRNP or PRND and ovine growth performance. Here, we also performed correlation analysis in all tested loci. These loci polymorphisms were significantly associated with ten different growth traits (P<0.05), except for g.93G>A. Meanwhile, in contrast to a previous study, there was no significant association between the seven SNP loci analyzed and our previously reported sheep PRND or PRNP insertion/deletion mutations. Our findings may provide new insights into polymorphic variation in ovine PRNT, which may contribute to genetic improvements in economic traits that are important for sheep breeding.

Prions adopt alternative, self-replicating protein conformations and thereby determine novel phenotypes that are often irreversible. Nevertheless, dominant-negative prion mutants can revert phenotypes associated with some conformations. These observations suggest that, while intervention is possible, distinct inhibitors must be developed to overcome the conformational plasticity of prions. To understand the basis of this specificity, we determined the impact of the G58D mutant of the Sup35 prion on three of its conformational variants, which form amyloids in S. cerevisiae. G58D had been previously proposed to have unique effects on these variants, but our studies suggest a common mechanism. All variants, including those reported to be resistant, are inhibited by G58D but at distinct doses. G58D lowers the kinetic stability of the associated amyloid, enhancing its fragmentation by molecular chaperones, promoting Sup35 resolubilization, and leading to amyloid clearance particularly in daughter cells. Reducing the availability or activity of the chaperone Hsp104, even transiently, reverses curing. Thus, the specificity of inhibition is determined by the sensitivity of variants to the mutant dosage rather than mode of action, challenging the view that a unique inhibitor must be developed to combat each variant.

Gerstmann-Sträussler-Scheinker is a genetic prion disease and the most common mutation is p.Pro102Leu. We report clinical, molecular and neuropathological data of seven individuals, belonging to two unrelated Brazilian kindreds, carrying the p.Pro102Leu. Marked differences among patients were observed regarding age at onset, disease duration and clinical presentation. In the first kindred, two patients had rapidly progressive dementia and three exhibited predominantly ataxic phenotypes with variable ages of onset and disease duration. In this family, age at disease onset in the mother and daughter differed by 39 years. In the second kindred, different phenotypes were also reported and earlier ages of onset were associated with 129 heterozygosis. No differences were associated with apoE genotype. In these kindreds, the codon 129 polymorphism could not explain the clinical variability and 129 heterozygosis was associated with earlier disease onset. Neuropathological examination in two patients confirmed the presence of typical plaques and PrPsc immunopositivity.

The use of diffusion MRI improved the accuracy of diagnosis in Creutzfeldt-Jakob disease (CJD) and expanded our knowledge of the changes occurring in the brain during the disease. The aim of this study was to test whether in patients with E200K familial CJD (fCJD) the clinical severity correlates with the disease burden as reflected by the extent of cortical involvement in DWI MRI. Consecutive fCJD patients were examined by a neurologist who performed several tests including the CJD neurological scale (CJD-NS), MiniMental status examination (MMSE), Frontal Assessment Battery (FAB), NIH Stroke Scale (NIHSS), and the expanded disability status scale (EDSS). A simultaneously acquired MRI was analyzed by measuring the extent of cortical involvement in the DWI axial sequence. Correlations were tested for using Pearson test. Fifty-two fCJD patients (35 males, mean age 59.4 ± 5.7 years) were recruited to the study. Significant negative correlation was found between the extent of cortical involvement and the cognitive performance of the patients as reflected by their MMSE and FAB scores. In addition, a significant positive correlation was found between the MRI and the clinical disease severity scales CJD-NS and EDSS. The correlation between clinical scales of severity and cognitive dysfunction and the disease burden confirms the reliability of the CJD-NS scale. Further studies are warranted to examine whether MRI may serve not only for diagnosis but also as a biomarker for follow-up of disease progression and the efficacy of potential treatments.

Objective: Mutations in the gene encoding the prion protein (PrP) are responsible for approximately 10 to 15% of cases of prion disease in humans, including Creutzfeldt-Jakob disease (CJD). Here, we report on the discovery of a previously unreported C-terminal PrP mutation (A224V) in a CJD patient exhibiting a disease similar to the rare VV1 subtype of sporadic (s) CJD and investigate the role of this mutation in prion replication and transmission., Methods: We generated transgenic (Tg) mice expressing human PrP with the V129 polymorphism and A224V mutation, denoted Tg(HuPrP,V129,A224V) mice, and inoculated them with different subtypes of sCJD prions., Results: Transmission of sCJD VV2 or MV2 prions was accelerated in Tg(HuPrP,V129,A224V) mice, compared to Tg(HuPrP,V129) mice, with incubation periods of ∼110 and ∼210 days, respectively. In contrast, sCJD MM1 prions resulted in longer incubation periods in Tg(HuPrP,V129,A224V) mice, compared to Tg(HuPrP,V129) mice (∼320 vs. ∼210 days). Prion strain fidelity was maintained in Tg(HuPrP,V129,A224V) mice inoculated with sCJD VV2 or MM1 prions, despite the altered replication kinetics., Interpretation: Our results suggest that A224V is a risk factor for prion disease and modulates the transmission behavior of CJD prions in a strain-specific manner, arguing that residues near the C-terminus of PrP are important for controlling the kinetics of prion replication., (© 2015 American Neurological Association.)

To explore clinical, histopathological and genetic features of a case with fatal familial insomnia (FFI) and review the related literatures. A middle-aged woman who complained of "insomnia for 9 months and psychosis for 3 months" was suspicious of FFI. The clinical features of the patient were analyzed, and the dead patient was examined by autopsy and the brain tissues were obtained for histopathological studies, and the blood samples from the patient and some of her familial members were collected for the sequencing of prion protein gene (PRNP). The main clinical features included intractable insomnia, psychiatric symptoms and abnormal night sleep behavior, unsteady gait, difficulty swallowing, sudden death, and positive family history. The pathological studies showed neuronal loss and gliosis of multiple brain tissues in the proband, predominated with thalamus; and analysis of PRNP revealed gene D178N mutation, and linkage with 129 methionine (Met) allele in the proband and a relative. FFI patients may manifest as sudden death, and may have prominent psychiatric symptoms; the corresponding gene mutation could occur in the asymptomatic carriers; the data of autopsy and brain tissue pathology is helpful for further understanding of this disease.

Prions are proteins that have the potential to refold into a novel conformation that templates the conversion of like molecules to the altered infectious form. In the yeast Saccharomyces cerevisiae, trans-generational epigenetic inheritance can be mediated by a number of structurally and functionally diverse prions. Prionogenesis can confer both loss-of-function and gain-of-function properties to the prion protein and this in turn can have a major impact on host phenotype, short-term adaptation and evolution of new traits. Prionogenesis shares a number of properties in common with paramutation and can be considered as a mitotically and meiotically heritable change in protein conformation induced by trans-interactions between homologous proteins., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Yeasts contain various protein-based genetic elements, termed prions, that result from the structural conversion of proteins into self-propagating amyloid forms. Most yeast prion proteins contain glutamine/asparagine (Q/N)-rich prion domains that drive prion activity. Here, we explore two mechanisms by which new prion domains could evolve. First, it has been proposed that mutation and natural selection will tend to result in proteins with aggregation propensities just low enough to function under physiological conditions and thus that a small number of mutations are often sufficient to cause aggregation. We hypothesized that if the ability to form prion aggregates was a sufficiently generic feature of Q/N-rich domains, many nonprion Q/N-rich domains might similarly have aggregation propensities on the edge of prion formation. Indeed, we tested four yeast Q/N-rich domains that had no detectable aggregation activity; in each case, a small number of rationally designed mutations were sufficient to cause the proteins to aggregate and, for two of the domains, to create prion activity. Second, oligopeptide repeats are found in multiple prion proteins, and expansion of these repeats increases prion activity. However, it is unclear whether the effects of repeat expansion are unique to these specific sequences or are a generic result of adding additional aggregation-prone segments into a protein domain. We found that within nonprion Q/N-rich domains, repeating aggregation-prone segments in tandem was sufficient to create prion activity. Duplication of DNA elements is a common source of genetic variation and may provide a simple mechanism to rapidly evolve prion activity.

The fragment 106-126 of prion protein exhibits similar properties to full-length prion. Experiments have shown that the A117V mutation enhances the aggregation of PrP106-126, while the H111S mutation abolishes the assembly. However, the mechanism of the change in the aggregation behavior of PrP106-126 upon the two mutations is not fully understood. In this study, replica exchange molecular dynamics simulations were performed to investigate the conformational ensemble of the WT PrP106-126 and its two mutants A117V and H111S. The obtained results indicate that the three species are all intrinsically disordered but they have distinct morphological differences. The A117V mutant has a higher propensity to form β-hairpin structures than the WT, while the H111S mutant has a higher population of helical structures. Furthermore, the A117V mutation increases the hydrophobic solvent accessible surface areas of PrP106-126 and the H111S mutation reduces the exposure of hydrophobic residues. It can be concluded that the difference in populations of β-hairpin structures and the change of hydrophobic solvent accessible areas may induce the different aggregation behaviors of the A117V and the H111S mutated PrP106-126. Understanding why the two mutations have contrary effects on the aggregation of PrP106-126 is very meaningful for further elucidation of the mechanism underlying aggregation and design of inhibitor against aggregation process.

Familial Creutzfeldt-Jakob disease (fCJD) in Jews of Libyan ancestry is caused by an E200K mutation in the PRNP gene. While carriers are born with this mutation, they usually remain asymptomatic until middle age. Early detection of conversion is crucial for understanding and eventually for the treatment of the disease. The aim of this study was to report longitudinal MRI data in E200K individuals who eventually converted from healthy mutation carriers to clinically symptomatic CJD. As a part of a prospective study, asymptomatic E200K mutation carriers were scanned annually until their conversion to symptomatic disease. Standardized diffusion and anatomical MR sequences were performed before and after clinical conversion in the subjects and those were compared to 15 non-carrier siblings ("healthy controls"). Blinded radiological readings and region of interest analyses were performed. Radiological readings of individual cases failed to detect characteristic changes in the scans taken before the conversion. Region of interest analysis of diffusion changes in pre-symptomatic stage was inconclusive; however, ADC reduction was found in early and late stages of the disease. Computerized volumetric analysis revealed monotonic volume reductions in thalamus, putamen and caudate following conversion, and the lateral ventricles showed dilatation of up to 62 % after clinical conversion. Although the clinical manifestations at disease onset are variable, the diffusion abnormalities and/or volume changes in the thalamus and basal ganglia during conversion may indicate early involvement of the thalamostriatal neuronal circuit.

The mechanism of prion protein (PrP) conversion, the key event in prion diseases, is still not understood. We investigated how perturbations of interactions between the subdomains β1-α1-β2 and α2-α3 affect PrP conversion. In vitro fibrillization and biophysical methods were used to relate mouse PrP conversion kinetics to thermodynamic stability. We show that pathologic mutations H187R and E196K destabilize PrP (by 3.2 and 1.1 kJ/mol, respectively, at pH 7) and accelerate fibrillization. At acidic pH, the major contribution to the destabilization of PrP comes from the protonation of histidine 187 because its replacement by tyrosine led to more stable protein (by 4.2 kJ/mol at pH 4) with slower fibrillization. Furthermore, we show that the introduction of a novel histidine residue into the subdomain interface (F198H) acts as a pH-inducible switch that promotes conversion upon histidine protonation, whereas this effect is not observed when His residue is introduced at the protein surface (Y155H). We observed a strong correlation between the stability of native structure and kinetics of fibrillization of PrP variants. Our results show that pathologic mutations promote subdomain separation and suggest that stabilization of the native structure might be a viable strategy for the development of novel therapeutics for prion diseases., (© FASEB.)

Familial prion protein (PrP) mutants undergo conversion from soluble and protease-sensitive to insoluble and partially protease-resistant proteins. Cyclin-dependent kinase 5 (Cdk5) phosphorylation of wild type PrP (pPrP) at serine 43 induces a conversion of PrP into aggregates and fibrils. Here, we investigated whether familial PrP mutants are predisposed to Cdk5 phosphorylation and whether phosphorylation of familial PrP mutants increases conversion. PrP mutants representing three major familial PrP diseases and different PrP structural domains were studied. We developed a novel in vitro kinase reaction coupled with Thioflavin T binding to amyloid structure assay to monitor phosphorylation-dependent amyloid conversion. Although non-phosphorylated full-length wild type or PrP mutants did not convert into amyloid, Cdk5 phosphorylation rapidly converted these into Thioflavin T-positive structures following first order kinetics. Dephosphorylation partially reversed conversion. Phosphorylation-dependent conversion of PrP from α-helical structures into β-sheet structures was confirmed by circular dichroism. Relative to wild type pPrP, most PrP mutants showed increased rate constants of conversion. In contrast, non-phosphorylated truncated PrP Y145X (where X represents a stop codon) and Q160X mutants converted spontaneously into Thioflavin T-positive fibrils after a lag phase of over 20 h, indicating nucleation-dependent polymerization. Phosphorylation reduced the lag phase by over 50% and thus accelerated the formation of the nucleating event. Consistently, phosphorylated Y145X and phosphorylated Q160X exacerbated conversion in a homologous seeding reaction, whereas WT pPrP could not seed WT PrP. These results demonstrate an influence of both the N terminus and the C terminus of PrP on conversion. We conclude that post-translational modifications of the flexible N terminus of PrP can cause or exacerbate PrP mutant conversion., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

The palindromic region AGAAAAGA (PrP113-120) in prion is highly amyloidogenic and very critical in the structural conversion of cellular prion protein to its pathogenetic form. In this region, there is an important point mutation A117V, which is closely related to the occurrence of Gerstmann-Straussler-Scheinker Syndrome. However, the detailed knowledge about the effects of the A117V mutation on the folding and aggregation of the palindromic sequences is still lacking. To investigate the impacts of A117V mutation on the earliest steps along the PrP113-120 aggregation pathway, replica exchange molecular dynamics simulations of the monomer, 2- and 4-peptide systems of PrP113-120 and its A117V mutant were carried out. The simulations of monomers indicate that both WT and the A117V mutated PrP113-120 are mostly random coils with helical structures transiently populated. Differently, the A117V mutation enhances the intrinsic disorder of PrP113-120. The simulations of 2- and 4-peptide systems of the two species show that the A117V mutation increases the sheet contents and the populations of oligomers, which may be attributed to the enhancement of inter-peptide backbone hydrogen bonding interactions and side chain hydrophobic interactions. Overall, the study provides structural insights into the impacts of the A117V mutation on the folding and assembly of the palindromic sequences, which might be helpful to elucidate the mechanism underlying prion disease and the origin of the Gerstmann-Straussler-Scheinker Syndrome.

Familial fatal insomnia (FFI) is fatal disorder characterized by damage to select thalamic nuclei, together with progressive insomnia and dysautonomia. In subjects carrying the D178N prion protein (PRNP) mutation, distinct phenotypes can be observed, depending on the methionine (Met) /valine (Val) codon 129 polymorphism. We report here a Chinese case of FFI with a D178N/Met129 genotype of the PRNP gene, who exhibited rapidly progressive dementia combined with behavioral disturbances and paroxysmal limb myoclonus. Our patient did not show refractory insomnia early in the disease course, nor demonstrate typical MRI and EEG alterations. There was remarkable family history of similar symptoms.

Creutzfeldt-Jakob disease (CJD) presents with rapidly progressive dementia associated with several symptoms including pyramidal, extrapyramidal, and cerebellar signs. In Japan, patients with PRNP gene mutations comprise 18.3% of CJD cases. In the present study, we report a 74-year-old man with a double mutation in the PRNP gene. He showed dysarthria, gait disturbance, and cognitive impairment. High signal intensity was observed in the bilateral cortex on brain MRI in diffusion-weighted images. There were high total Tau protein and 14-3-3 protein levels in the cerebrospinal fluid. We diagnosed him as having CJD clinically, and analyzed the PRNP gene, which revealed a V180I mutation and a M232R one, i.e., a compound heterozygous status. In our patient, the disease has very slowly progressive (total disease course, 37 months). The V180I and M232R mutations are specific mutations to Japanese CJD patients. For patients with a double PRNP gene mutation, only V180I and M232R have been known. Patients with a double mutation (V180I /M232R) in the PRNP gene might show an atypical disease course with a slow progression.

Here we report a genetically confirmed case of Creutzfeldt-Jakob disease with a prion protein gene codon 180 mutation presenting atypical magnetic resonance imaging findings. The present case exhibited an acute onset and lateralized neurologic signs, and progressive cognitive impairment. No myoclonus or periodic synchronous discharges on electroencephalography were observed. Diffusion-weighted images revealed areas of high signal intensity in the right frontal and temporal cortices at onset that extended to the whole cortex and basal ganglia of the right cerebral hemisphere at 3 months. Although the cerebrospinal fluid (CSF) was initially negative for neuron specific enolase, tau protein, 14-3-3 protein, and abnormal prion protein, the CSF was positive for these brain-derived proteins at 3 months after onset.

Anticipation is the phenomenon whereby age of onset in genetic disease decreases in successive generations. Three independent reports have claimed anticipation in Creutzfeldt-Jakob disease (CJD) caused by the c.598G > A mutation in PRNP encoding a p.Glu200Lys (E200K) substitution in the prion protein. If confirmed, this finding would carry clear implications for genetic counseling. We analyzed pedigrees with this mutation from four prion centers worldwide (n = 217 individuals with the mutation) to analyze age of onset and death in affected and censored individuals. We show through simulation that selective ascertainment of individuals whose onset falls within the historical window since the mutation's 1989 discovery is sufficient to create robust false signals both of anticipation and of heritability of age of onset. In our data set, the number of years of anticipation observed depends upon how strictly the data are limited by the ascertainment window. Among individuals whose disease was directly observed at a study center, a 28-year difference between parent and child age of onset is observed (p = 0.002), but including individuals ascertained retrospectively through family history reduces this figure to 7 years (p = 0.005). Applying survival analysis to the most thoroughly ascertained subset of data eliminates the signal of anticipation. Moreover, even non-CJD deaths exhibit 16 years anticipation (p = 0.002), indicating that ascertainment bias can entirely explain observed anticipation. We suggest that reports of anticipation in genetic prion disease are driven entirely by ascertainment bias. Guidelines for future studies claiming statistical evidence for anticipation are suggested., (Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Molecular chaperones constitute a major component of the cellular stress response machinery in neurodegenerative diseases, many of which are characterized by the misfolding and aggregation of endogenous cellular proteins into generic amyloid macrostructures. Heterologous expression of the yeast protein remodelling factor Hsp104 has been proposed as a possible therapeutic approach in such disease conditions. Hsp104 is unique in its ability to act as a protein 'disaggregase' by removing smaller units from amyloid fibrils and has no homologue in metazoa. The effect of Hsp104 is strongly modulated by its expression level. We show that at endogenous levels, the presence of Hsp104 has a deleterious effect on protein aggregation in two different strains of yeast. Overexpression of wild-type and mutant human α-synuclein in a well-validated yeast model of Parkinson's disease and in an isogenic Hsp104-deleted strain resulted in lower oxidative stress and reduced damage to cellular proteins in the latter case. This translated to lower cytotoxicity and increased cell viability. Endocytotic defect caused due to aggregation of α-syuclein was also rescued in cells lacking Hsp104. Our results show that the effect of overexpression of a chaperone on protein misfolding/aggregation cannot be predicted from its function in the host expression platform., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Prion diseases are progressive disorders that affect the central nervous system leading to memory loss, personality changes, ataxia and neurodegeneration. In humans, these disorders include Creutzfeldt-Jakob disease, kuru and Gerstmann-Straüssler-Scheinker (GSS) syndrome, the latter being a dominantly inherited prion disease associated with missense mutations in the gene that codes for the prion protein. The exact mechanism by which mutant prion proteins affect the central nervous system and cause neurological disease is not well understood. We have generated an inducible model of GSS disease in Drosophila melanogaster by temporally expressing a misfolded form of the murine prion protein in cholinergic neurons. Flies accumulating this mutant protein develop motor abnormalities which are associated with electrophysiological defects in cholinergic neurons. We find that, upon blocking the expression of the mutant protein, both behavioral and electrophysiological defects can be reversed. This represents the first case of reversibility reported in a model of genetic prion disease. Additionally, we observe that endogenous mechanisms exist within Drosophila that are capable of clearing the accumulated prion protein., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: In absence of a positive family history, the diagnosis of fatal familial insomnia (FFI) might be difficult because of atypical clinical features and low sensitivity of diagnostic tests. FFI patients usually do not fulfil the established classification criteria for Creutzfeldt-Jakob disease (CJD); therefore, a prion disease is not always suspected., Objective: To propose an update of diagnostic pathway for the identification of patients for the analysis of D178-M129 mutation., Design and Methods: Data on 41 German FFI patients were analysed. Clinical symptoms and signs, MRI, PET, SPECT, polysomnography, EEG and cerebrospinal fluid biomarkers were studied., Results: An algorithm was developed which correctly identified at least 81% of patients with the FFI diagnosis during early disease stages. It is based on the detection of organic sleep disturbances, either verified clinically or by a polysomnography, and a combination of vegetative and focal neurological signs and symptoms. Specificity of the approach was tested on three cohorts of patients (MM1 sporadic CJD patients, non-selected sporadic CJD and other neurodegenerative diseases)., Conclusions: The proposed scheme may help to improve the clinical diagnosis of FFI. As the sensitivity of all diagnostic tests investigated but polysomnography is low in FFI, detailed clinical investigation is of special importance.

Objectives: Genetic Creutzfeldt-Jakob disease (CJD) due to V180I mutation in the prion protein gene (PRNP) is of great interest because of the differences from sporadic CJD and other genetic prion diseases in terms of clinical features, as well as pathological and biochemical findings. However, few systematic observations about the clinical features in patients with this unique mutation have been published. Therefore, the goal of this study was to relate this mutation to other forms of CJD from a clinical perspective., Design: We analysed clinical symptoms, prion protein genetics, biomarkers in cerebrospinal fluid (CSF) and MRI of patients., Participants: 186 Japanese patients with the V180I mutation in PRNP., Results: Our results indicate that the V180I mutation caused CJD at an older age, with a slower progression and a lower possibility of developing myoclonus, cerebellar, pyramidal signs and visual disturbance compared with classical sporadic CJD with methionine homozygosity at codon 129 of PRNP. Cognitive impairment was the major symptom. Diffuse hyperintensity of the cerebral cortex in diffusion-weighted MRI might be helpful for diagnosis. Owing to the low positivity of PrP(Sc) in the CSF, genetic analysis was often required for a differential diagnosis from slowly progressive dementia., Conclusions: We conclude that the V180I mutation in PRNP produces a late-developing and slow-developing, less severe form of CJD, whose lesions are uniquely distributed compared with sporadic and other genetic forms of CJD., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Quinacrine's ability to reduce levels of pathogenic prion protein (PrP(Sc)) in mouse cells infected with experimentally adapted prions led to several unsuccessful clinical studies in patients with prion diseases, a 10-y investment to understand its mechanism of action, and the production of related compounds with expectations of greater efficacy. We show here, in stark contrast to this reported inhibitory effect, that quinacrine enhances deer and elk PrP(Sc) accumulation and promotes propagation of prions causing chronic wasting disease (CWD), a fatal, transmissible, neurodegenerative disorder of cervids of uncertain zoonotic potential. Surprisingly, despite increased prion titers in quinacrine-treated cells, transmission of the resulting prions produced prolonged incubation times and altered PrP(Sc) deposition patterns in the brains of diseased transgenic mice. This unexpected outcome is consistent with quinacrine affecting the intrinsic properties of the CWD prion. Accordingly, quinacrine-treated CWD prions were comprised of an altered PrP(Sc) conformation. Our findings provide convincing evidence for drug-induced conformational mutation of prions without the prerequisite of generating drug-resistant variants of the original strain. More specifically, they show that a drug capable of restraining prions in one species/strain setting, and consequently used to treat human prion diseases, improves replicative ability in another and therefore force reconsideration of current strategies to screen antiprion compounds.

Importance: To describe the first case of preimplantation genetic diagnosis (PGD) and in vitro fertilization (IVF) performed for the prevention of genetic prion disease in the children of a 27-year-old asymptomatic woman with a family history of Gerstmann-Sträussler-Sheinker syndrome (GSS)., Observations: PGD and fertilization cycles resulted in detection of 6 F198S mutation-free embryos. Of these, 2 were selected for embryo transfer to the patient's uterus, yielding a clinical twin pregnancy and birth of healthy but slightly premature offspring with normal development at age 27 months., Conclusion and Relevance: IVF with PGD is a viable option for couples who wish to avoid passing the disease to their offspring. Neurologists should be aware of PGD to be able to better consult at-risk families on their reproductive choices.

Unlabelled: Prion diseases are a group of fatal and incurable neurodegenerative diseases affecting both humans and animals. The principal mechanism of these diseases involves the misfolding the host-encoded cellular prion protein, PrP(C), into the disease-associated isoform, PrP(Sc). Familial forms of human prion disease include those associated with the mutations G114V and A117V, which lie in the hydrophobic domain of PrP. Here we have studied the murine homologues (G113V and A116V) of these mutations using cell-based and animal models of prion infection. Under normal circumstances, the mutant forms of PrP(C) share similar processing, cellular localization, and physicochemical properties with wild-type mouse PrP (MoPrP). However, upon exposure of susceptible cell lines expressing these mutants to infectious prions, very low levels of protease-resistant aggregated PrP(Sc) are formed. Subsequent mouse bioassay revealed high levels of infectivity present in these cells. Thus, these mutations appear to limit the formation of aggregated PrP(Sc), giving rise to the accumulation of a relatively soluble, protease sensitive, prion species that is highly neurotoxic. Given that these mutations lie next to the glycine-rich region of PrP that can abrogate prion infection, these findings provide further support for small, protease-sensitive prion species having a significant role in the progression of prion disease and that the hydrophobic domain is an important determinant of PrP conversion., Importance: Prion diseases are transmissible neurodegenerative diseases associated with an infectious agent called a prion. Prions are comprised of an abnormally folded form of the prion protein (PrP) that is normally resistant to enzymes called proteases. In humans, prion disease can occur in individuals who inherited mutations in the prion protein gene. Here we have studied the effects of two of these mutations and show that they influence the properties of the prions that can be formed. We show that the mutants make highly infectious prions that are more sensitive to protease treatment. This study highlights a certain region of the prion protein as being involved in this effect and demonstrates that prions are not always resistant to protease treatment.

Prion diseases are caused by misfolding and aggregation of the prion protein (PrP). Pathogenic mutations such as Y218N and E196K are known to cause Gerstmann-Sträussler-Scheinker syndrome and Creutzfeldt-Jakob disease, respectively. Here we describe molecular dynamics simulations of these mutant proteins to better characterize the detailed conformational effects of these sequence substitutions. Our results indicate that the mutations disrupt the wild-type native PrP(C) structure and cause misfolding. Y218N reduced hydrophobic packing around the X-loop (residues 165-171), and E196K abolished an important wild-type salt bridge. While differences in the mutation site led PrP mutants to misfold along different pathways, we observed multiple traits of misfolding that were common to both mutants. Common traits of misfolding included: 1) detachment of the short helix (HA) from the PrP core; 2) exposure of side chain F198; and 3) formation of a nonnative strand at the N-terminus. The effect of the E196K mutation directly abolished the wild-type salt bridge E196-R156, which further destabilized the F198 hydrophobic pocket and HA. The Y218N mutation propagated its effect by increasing the HB-HC interhelical angle, which in turn disrupted the packing around F198. Furthermore, a nonnative contact formed between E221 and S132 on the S1-HA loop, which offered a direct mechanism for disrupting the hydrophobic packing between the S1-HA loop and HC. While there were common misfolding features shared between Y218N and E196K, the differences in the orientation of HB and HC and the X-loop conformation might provide a structural basis for identifying different prion strains.

The tumor suppressor protein p53 loses its function in more than 50% of human malignant tumors. Recent studies have suggested that mutant p53 can form aggregates that are related to loss-of-function effects, negative dominance and gain-of-function effects and cancers with a worsened prognosis. In recent years, several degenerative diseases have been shown to have prion-like properties similar to mammalian prion proteins (PrPs). However, whereas prion diseases are rare, the incidence of these neurodegenerative pathologies is high. Malignant tumors involving mutated forms of the tumor suppressor p53 protein seem to have similar substrata. The aggregation of the entire p53 protein and three functional domains of p53 into amyloid oligomers and fibrils has been demonstrated. Amyloid aggregates of mutant p53 have been detected in breast cancer and malignant skin tumors. Most p53 mutations related to cancer development are found in the DNA-binding domain (p53C), which has been experimentally shown to form amyloid oligomers and fibrils. Several computation programs have corroborated the predicted propensity of p53C to form aggregates, and some of these programs suggest that p53C is more likely to form aggregates than the globular domain of PrP. Overall, studies imply that mutant p53 exerts a dominant-negative regulatory effect on wild-type (WT) p53 and exerts gain-of-function effects when co-aggregating with other proteins such as p63, p73 and acetyltransferase p300. We review here the prion-like behavior of oncogenic p53 mutants that provides an explanation for their dominant-negative and gain-of-function properties and for the high metastatic potential of cancers bearing p53 mutations. The inhibition of the aggregation of p53 into oligomeric and fibrillar amyloids appears to be a promising target for therapeutic intervention in malignant tumor diseases.

Abstract Here, we reported a Chinese case of Creutzfeldt-Jakob disease (CJD) with a rare mutation in the prion protein gene (PRNP) leading to an exchange of amino acid from valine (V) to isoleucine (I) at codon 180 (V180I). The 72 year-old Chinese women started with gradual memory loss. On admission, she did not present special abnormality during clinical examinations except bradykinesia in her lower extremities. Myoclonic jerks and increased muscle tone were noticed 3 months after the onset. No periodic activity was recorded at electroencephalography (EEG) and 14-3-3 protein was negative in the cerebrospinal fluid (CSF) sample. Brain diffusion weighted images (DWI) demonstrated high signal intensities in bilateral frontal, parietal, temporal and occipital cortices, especially on the left hemisphere, and high signal intensities were also seen in the left caudate nucleus and the putamen. The patient had no family history of similar symptoms. Her general condition was gradually deteriorative, but the patient was still alive when we performed the follow-up 12 months after onset.

We report a Japanese patient with Creutzfeldt-Jakob disease (CJD) with a V203I homozygous mutation of the prion protein gene (PRNP). A 73-year-old woman developed rapidly progressive gait disturbance and cognitive dysfunction. Four months after the onset, she entered a state of an akinetic mutism. Gene analysis revealed a homozygous V203I mutation in the PRNP. Familial CJD with a V203I mutation is rare, and all previously reported cases had a heterozygous mutation showing manifestations similar to those of typical sporadic CJD. Although genetic prion diseases with homozygous PRNP mutations often present with an earlier onset and more rapid clinical course than those with heterozygous mutations, no difference was found in clinical phenotype between our homozygous case and reported heterozygous cases.

We herein report a case of Creutzfeldt-Jakob disease (CJD) with a V210I mutation and discuss the pathological findings. The patient's clinical course was quite similar to that of patients with sporadic CJD. Diffusion-weighted magnetic resonance imaging (MRI) disclosed a high signal intensity in the basal ganglia and cerebral cortices. Pathologically, spongiform degeneration of neurons and their processes with reactive astrocytosis was observed. Prion protein immunostaining revealed diffuse positive and plaque-type patterns. Only one Japanese case of CJD with this type of mutation has been reported to date, but without any pathological examination results. Therefore, this report is considered to be highly significant for understanding CJD.

Prions exist as strains, which are thought to reflect PrP(Sc) conformational variants. Prion strains can mutate and it has been proposed that prion mutability depends on an intrinsic heterogeneity of prion populations that would behave as quasispecies. We investigated in vitro prion mutability of 2 strains, by following PrP(Sc) variations of populations serially propagated in PMCA under constant environmental pressure. Each strain was propagated either at low dilution of the seed, i.e., by large population passages, or at limiting dilution, mimicking bottleneck events. In both strains, PrP(Sc) conformational variants were identified only after large population passages, while repeated bottleneck events caused a rapid decline in amplification rates. These findings support the view that mutability is an intrinsic property of prions.

Prion diseases are consistently associated with prion protein (PrP(C)) misfolding rendering a cascade of auto-catalytic self-perpetuation of misfolded PrP in an afflicted individual. The molecular process is intriguingly similar to all known amyloid diseases both local and systemic. The prion disease is also infectious by the transfer of misfolded PrP from one individual to the next. Transmissibility is surprisingly efficient in prion diseases and given the rapid disease progression following initial symptoms the prionoses stand out from other amyloidoses, which all may be transmissible under certain circumstances. The nature of the infectious prion as well as the genotype of the host is important for transmissibility. For hitherto unexplained reasons the majority of Europeans carry a missense mutation on one or both alleles of the PrP gene (PRNP), and hence express a variant of PrP with a substitution for valine (V) instead of methionine (M) in position 129. In fact the 129M/V variant is very common in all populations except for the Japanese. Sporadic Creutzfeldt-Jakob disease is a disease rarely striking people below the age of 60, where homozygosity especially 129MM is a very strong risk factor. Paradoxically, the 129M/V polymorphism suggestive of heterozygote advantage is one of the most clear cut disease associated traits of the human population, yet prion disease is extraordinarily rare. The genetic basis for how this trait spread with such prevalence within human populations is still target to investigations and deserves attention. This short essay represents a somewhat provocative hypothetical notion of a possible ancient significance of this polymorphism.

In man, mutations in different regions of the prion protein (PrP) are associated with infectious neurodegenerative diseases that have remarkably different clinical signs and neuropathological lesions. To explore the roots of this phenomenon, we created a knock-in mouse model carrying the mutation associated with one of these diseases [Creutzfeldt-Jakob disease (CJD)] that was exactly analogous to a previous knock-in model of a different prion disease [fatal familial insomnia (FFI)]. Together with the WT parent, this created an allelic series of three lines, each expressing the same protein with a single amino acid difference, and with all native regulatory elements intact. The previously described FFI mice develop neuronal loss and intense reactive gliosis in the thalamus, as seen in humans with FFI. In contrast, CJD mice had the hallmark features of CJD, spongiosis and proteinase K-resistant PrP aggregates, initially developing in the hippocampus and cerebellum but absent from the thalamus. A molecular transmission barrier protected the mice from any infectious prion agents that might have been present in our mouse facility and allowed us to conclude that the diseases occurred spontaneously. Importantly, both models created agents that caused a transmissible neurodegenerative disease in WT mice. We conclude that single codon differences in a single gene in an otherwise normal genome can cause remarkably different neurodegenerative diseases and are sufficient to create distinct protein-based infectious elements.

Importance: Here we describe the unusual clinical and molecular-neuropathological profile of a case of Gerstmann-Sträussler-Scheinker disease associated with a novel prion protein (PRNP) gene mutation., Observations: This case report from the Australian National Creutzfeldt-Jakob Disease Registry concerns a 61-year-old British-born woman with no history of neurodegenerative disorder in first-degree relatives. Rapidly progressive dementia, altered behavior, and cerebellar ataxia dominated the clinical picture in the period immediately following minor elective surgery, with death 1 month later in an akinetic-mute state. Brain histopathological examination revealed neuronal loss, scant foci of spongiform change, and diffuse multicentric amyloid plaques, selectively immunoreactive for prion protein, within the cerebral and cerebellar cortices and deep gray matter. Tau immune-reactive neurofibrillary tangles and neuritic threads were present in the cerebral cortex. PRNP sequencing demonstrated a valine to glycine mutation at codon 176, with valine homozygosity at polymorphic codon 129. Western-blot analysis of frozen brain tissue displayed a nonclassic protease-resistant prion protein banding pattern, with a prominent approximately 8-kDa protease-resistant fragment., Conclusions and Relevance: Reported is a proband with a novel PRNP mutation associated with neuropathologically confirmed Gerstmann-Sträussler-Scheinker disease displaying a somewhat unusual constellation of clinicopathological features, which overall subserve to further broaden an already diverse phenotypic spectrum.

Purpose of Review: The differential diagnosis of chorea syndromes may be complex and includes various genetic disorders such as Huntington's disease and mimicking disorders called Huntington's disease-like (HDL) phenotypes. To familiarize clinicians with these (in some cases very rare) conditions we will summarize the main characteristics., Recent Findings: HDL disorders are rare and account for about 1% of cases presenting with a Huntington's disease phenotype. They share overlapping clinical features, so making the diagnosis purely on clinical grounds may be challenging, however presence of certain characteristics may be a clue (e.g. prominent orofacial involvement in neuroferritinopathy etc.), Information of ethnic descent will also guide genetic work-up [HDL2 in Black Africans; dentatorubral-pallidoluysian atrophy (DRPLA) in Japanese etc.], Huntington's disease, the classical HDL disorders (except HDL3) and DRPLA are repeat disorders with anticipation effect and age-dependent phenotype in some, but genetic underpinnings may be more complicated in the other chorea syndromes., Summary: With advances in genetics more and more rare diseases are disentangled, allowing molecular diagnoses in a growing number of choreic patients. Hopefully, with better understanding of their pathophysiology we are moving towards mechanistic therapies.