Publications by authors named "Valerie Sim"

36 Publications

TREM2 expression in the brain and biological fluids in prion diseases.

Acta Neuropathol 2021 Apr 21. Epub 2021 Apr 21.

Network Center for Biomedical Research in Neurodegenerative Diseases (CIBERNED), L'Hospitalet de Llobregat, Spain.

Triggering receptor expressed on myeloid cells 2 (TREM2) is an innate immune cell surface receptor that regulates microglial function and is involved in the pathophysiology of several neurodegenerative diseases. Its soluble form (sTREM2) results from shedding of the TREM2 ectodomain. The role of TREM2 in prion diseases, a group of rapidly progressive dementias remains to be elucidated. In the present study, we analysed the expression of TREM2 and its main sheddase ADAM10 in the brain of sporadic Creutzfeldt-Jakob disease (sCJD) patients and evaluated the role of CSF and plasma sTREM2 as a potential diagnostic marker of prion disease. Our data indicate that, compared to controls, TREM2 is increased in sCJD patient brains at the mRNA and protein levels in a regional and subtype dependent fashion, and expressed in a subpopulation of microglia. In contrast, ADAM10 is increased at the protein, but not the mRNA level, with a restricted neuronal expression. Elevated CSF sTREM2 is found in sCJD, genetic CJD with mutations E200K and V210I in the prion protein gene (PRNP), and iatrogenic CJD, as compared to healthy controls (HC) (AUC = 0.78-0.90) and neurological controls (AUC = 0.73-0.85), while CSF sTREM2 is unchanged in fatal familial insomnia. sTREM2 in the CSF of cases with Alzheimer's disease, and multiple sclerosis was not significantly altered in our series. CSF sTREM2 concentrations in sCJD are PRNP codon 129 and subtype-related, correlate with CSF 14-3-3 positivity, total-tau and YKL-40, and increase with disease progression. In plasma, sTREM2 is increased in sCJD compared with HC (AUC = 0.80), displaying positive correlations with plasma total-tau, neurofilament light, and YKL-40. We conclude that comparative study of TREM2 in brain and biological fluids of prion diseases reveals TREM2 to be altered in human prion diseases with a potential value in target engagement, patient stratification, and disease monitoring.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00401-021-02296-1DOI Listing
April 2021

Oral administration of repurposed drug targeting Cyp46A1 increases survival times of prion infected mice.

Acta Neuropathol Commun 2021 04 1;9(1):58. Epub 2021 Apr 1.

Calgary Prion Research Unit, Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada.

Prion diseases are fatal, infectious, and incurable neurodegenerative disorders caused by misfolding of the cellular prion protein (PrP) into the infectious isoform (PrP). In humans, there are sporadic, genetic and infectious etiologies, with sporadic Creutzfeldt-Jakob disease (sCJD) being the most common form. Currently, no treatment is available for prion diseases. Cellular cholesterol is known to impact prion conversion, which in turn results in an accumulation of cholesterol in prion-infected neurons. The major elimination of brain cholesterol is achieved by the brain specific enzyme, cholesterol 24-hydroxylase (CYP46A1). Cyp46A1 converts cholesterol into 24(S)-hydroxycholesterol, a membrane-permeable molecule that exits the brain. We have demonstrated for the first time that Cyp46A1 levels are reduced in the brains of prion-infected mice at advanced disease stage, in prion-infected neuronal cells and in post-mortem brains of sCJD patients. We have employed the Cyp46A1 activator efavirenz (EFV) for treatment of prion-infected neuronal cells and mice. EFV is an FDA approved anti-HIV medication effectively crossing the blood brain barrier and has been used for decades to chronically treat HIV patients. EFV significantly mitigated PrP propagation in prion-infected cells while preserving physiological PrP and lipid raft integrity. Notably, oral administration of EFV treatment chronically at very low dosage starting weeks to months after intracerebral prion inoculation of mice significantly prolonged the lifespan of animals. In summary, our results suggest that Cyp46A1 as a novel therapeutic target and that its activation through repurposing the anti-retroviral medication EFV might be valuable treatment approach for prion diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s40478-021-01162-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8017635PMC
April 2021

From Cell Culture to Organoids-Model Systems for Investigating Prion Strain Characteristics.

Biomolecules 2021 01 14;11(1). Epub 2021 Jan 14.

Department of Medicine, University of Alberta, Edmonton, AB T6G 2B7, Canada.

Prion diseases are the hallmark protein folding neurodegenerative disease. Their transmissible nature has allowed for the development of many different cellular models of disease where prion propagation and sometimes pathology can be induced. This review examines the range of simple cell cultures to more complex neurospheres, organoid, and organotypic slice cultures that have been used to study prion disease pathogenesis and to test therapeutics. We highlight the advantages and disadvantages of each system, giving special consideration to the importance of strains when choosing a model and when interpreting results, as not all systems propagate all strains, and in some cases, the technique used, or treatment applied, can alter the very strain properties being studied.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/biom11010106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830147PMC
January 2021

Exposure Risk of Chronic Wasting Disease in Humans.

Viruses 2020 12 17;12(12). Epub 2020 Dec 17.

Centre for Prions and Protein Folding Diseases, Edmonton, AB T6G 2R3, Canada.

The majority of human prion diseases are sporadic, but acquired disease can occur, as seen with variant Creutzfeldt-Jakob disease (vCJD) following consumption of bovine spongiform encephalopathy (BSE). With increasing rates of cervid chronic wasting disease (CWD), there is concern that a new form of human prion disease may arise. Currently, there is no evidence of transmission of CWD to humans, suggesting the presence of a strong species barrier; however, in vitro and in vivo studies on the zoonotic potential of CWD have yielded mixed results. The emergence of different CWD strains is also concerning, as different strains can have different abilities to cross species barriers. Given that venison consumption is common in areas where CWD rates are on the rise, increased rates of human exposure are inevitable. If CWD was to infect humans, it is unclear how it would present clinically; in vCJD, it was strain-typing of vCJD prions that proved the causal link to BSE. Therefore, the best way to screen for CWD in humans is to have thorough strain-typing of harvested cervids and human CJD cases so that we will be in a position to detect atypical strains or strain shifts within the human CJD population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/v12121454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7766630PMC
December 2020

Creutzfeldt-Jakob Disease with a Five-Year Clinical Course, Multicentric Cerebellar Prion Plaques and Prior History of Biopsy-Proven Primary Angiitis of the Central Nervous System: A Case for Iatrogenic Exposure?

Viruses 2020 12 8;12(12). Epub 2020 Dec 8.

Department of Medicine, University of Alberta, Edmonton, AB T6G 2R3, Canada.

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive neurodegenerative disease that can arise spontaneously, genetically, or be acquired through iatrogenic exposure. Most patients die within a year of symptom onset. It is rare, affecting 1-2 per million per year, and the majority of cases are sporadic. Primary angiitis of the central nervous system (PACNS) is also rare, affecting 2.4 per million per year. We present a case of an unusually long clinical course of CJD, almost five years, which began with symptoms of apraxia. The patient had biopsy-proven PACNS 16 years prior to clinical presentation, and the site of biopsy was the left parietal lobe. Autopsy revealed multicentric prion plaques in the cerebellum, in the setting of normal genetic testing. The presence of plaques in the cerebellum, and prior neurosurgery, raises the possibility of iatrogenic exposure. We present the details of this case, including pathology from the original biopsy and final autopsy, as well as a review of relevant cases in the literature.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/v12121411DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7763133PMC
December 2020

Quaternary Structure Changes for PrP Predate PrP Downregulation and Neuronal Death During Progression of Experimental Scrapie Disease.

Mol Neurobiol 2021 Jan 21;58(1):375-390. Epub 2020 Sep 21.

Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.

Prion diseases are fatal neurodegenerative diseases in mammals with the unique characteristics of misfolding and aggregation of the cellular prion protein (PrP) to the scrapie prion (PrP). Although neuroinflammation and neuronal loss feature within the disease process, the details of PrP/PrP molecular transition to generate different aggregated species, and the correlation between each species and sequence of cellular events in disease pathogenesis are not fully understood. In this study, using mice inoculated with the RML isolate of mouse-adapted scrapie as a model, we applied asymmetric flow field-flow fractionation to monitor PrP and PrP particle sizes and we also measured seeding activity and resistance to proteases. For cellular analysis in brain tissue, we measured inflammatory markers and synaptic damage, and used the isotropic fractionator to measure neuronal loss; these techniques were applied at different timepoints in a cross-sectional study of disease progression. Our analyses align with previous reports defining significant decreases in PrP levels at pre-clinical stages of the disease and demonstrate that these decreases become significant before neuronal loss. We also identified the earliest PrP assemblies at a timepoint equivalent to 40% elapsed time for the disease incubation period; we propose that these assemblies, mostly composed of proteinase K (PK)-sensitive species, play an important role in triggering disease pathogenesis. Lastly, we show that the PK-resistant assemblies of PrP that appear at timepoints close to the terminal stage have similar biophysical characteristics, and hence that preparative use of PK-digestion selects for this specific subpopulation. In sum, our data argue that qualitative, as well as quantitative, changes in PrP conformers occur at the midpoint of subclinical phase; these changes affect quaternary structure and may occur at the threshold where adaptive responses become inadequate to deal with pathogenic processes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12035-020-02112-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695655PMC
January 2021

POSCAbilities: The Application of the Prion Organotypic Slice Culture Assay to Neurodegenerative Disease Research.

Biomolecules 2020 07 20;10(7). Epub 2020 Jul 20.

Centre for Prions and Protein Folding Diseases, University of Alberta, 204 Brain and Aging Research Building, 8710-112 St, Edmonton, AB T6G 2M8, Canada.

Prion diseases are fatal, transmissible neurodegenerative disorders whose pathogenesis is driven by the misfolding, self-templating and cell-to-cell spread of the prion protein. Other neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease, share some of these prion-like features, with different aggregation-prone proteins. Consequently, researchers have begun to apply prion-specific techniques, like the prion organotypic slice culture assay (POSCA), to these disorders. In this review we explore the ways in which the prion phenomenon has been used in organotypic cultures to study neurodegenerative diseases from the perspective of protein aggregation and spreading, strain propagation, the role of glia in pathogenesis, and efficacy of drug treatments. We also present an overview of the advantages and disadvantages of this culture system compared to in vivo and in vitro models and provide suggestions for new directions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/biom10071079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407827PMC
July 2020

A novel mechanism of phenotypic heterogeneity in Creutzfeldt-Jakob disease.

Acta Neuropathol Commun 2020 06 19;8(1):85. Epub 2020 Jun 19.

Department of Pathology, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.

One of remarkable features of sporadic Creutzfeldt-Jakob disease (sCJD) is the great phenotypic variability. Understanding the molecular basis of this variability has important implications for the development of therapeutic approaches. It is well established that, in many cases, phenotypic heterogeneity of sCJD is under control of two determinants: the genotype at the methionine (M)/valine (V) polymorphic codon 129 of the human prion protein gene and the type, 1 or 2, of the pathogenic and disease-related form of the prion protein, PrP. However, this scenario fails to explain the existence of distinct heterozygous sCJDMV2 subtypes, where heterogeneity occurs without any variation of the 129 allotype and PrP type. One of these subtypes, denoted sCJDMV2C, associated with PrP type 2, is characterized by widespread spongiform degeneration of the cerebral cortex (C). The second variant, denoted sCJDMV2K, features prominent deposition of PrP amyloid forming kuru type (K) plaques. Here we used a mass spectrometry based approach to test the hypothesis that phenotypic variability within the sCJDMV2 subtype is at least partly determined by the abundance of 129 M and 129 V polymorphic forms of proteinase K-resistant PrP (resPrP). Consistent with this hypothesis, our data demonstrated a strong correlation of the MV2C and MV2K phenotypes with the relative populations of protease-resistant forms of the pathogenic prion proteins, resPrP-129 M and resPrP-129 V, where resPrP-129 M dominated in the sCJDMV2C variant and resPrP-129 V in the sCJDMV2K variant. This finding suggests an important, previously unrecognized mechanism for phenotypic determination in human prion diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s40478-020-00966-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304206PMC
June 2020

Effectiveness of multimedia interventions in the provision of patient education on anticoagulation therapy: A review.

Patient Educ Couns 2020 10 21;103(10):2009-2017. Epub 2020 May 21.

Faculty of Pharmacy and Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia. Electronic address:

Objective: A literature review was conducted to identify available evidence on the use of multimedia patient educational interventions on anticoagulation therapy.

Methods: A literature search was conducted on 9/4/2020 via six research databases. Publications that evaluated the effects of these interventions on anticoagulation therapy were included.

Results: The review included ten original research studies (five randomized controlled trials, four observational studies and a pre- and post-interventional study), a systematic review and meta-analysis, three systematic reviews, a scoping review, and a literature review. Multimedia interventions significantly improved knowledge after education, but no significant differences found when compared to traditional methods. There was insufficient evidence to conclude whether knowledge retained over time. Patients were equally satisfied with both methods. Multimedia interventions significantly reduced healthcare professional's time required for education. Heterogeneity in intervention, methodology and results limited comparison and combination of findings across studies.

Conclusion: Multimedia patient educational interventions on anticoagulation therapy have similar outcomes to traditional methods in knowledge improvement and satisfaction, but they save health personnel time.

Practice Implications: There is lack of evidence to support the effectiveness of multimedia interventions in educating patients on anticoagulation therapy. Larger randomized studies evaluating their benefits in health outcomes and clinical practice are warranted.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.pec.2020.05.003DOI Listing
October 2020

Native nanodiscs formed by styrene maleic acid copolymer derivatives help recover infectious prion multimers bound to brain-derived lipids.

J Biol Chem 2020 06 1;295(25):8460-8469. Epub 2020 May 1.

Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada

Prions are lipidated proteins that interact with endogenous lipids and metal ions. They also assemble into multimers and propagate into the infectious scrapie form known as PrP The high-resolution structure of the infectious PrP state remains unknown, and its analysis largely relies on detergent-based preparations devoid of endogenous ligands. Here we designed polymers that allow isolation of endogenous membrane:protein assemblies in native nanodiscs without exposure to conventional detergents that destabilize protein structures and induce fibrillization. A set of styrene-maleic acid (SMA) polymers including a methylamine derivative facilitated gentle release of the infectious complexes for resolution of multimers, and a thiol-containing version promoted crystallization. Polymer extraction from brain homogenates from Syrian hamsters infected with Hyper prions and WT mice infected with Rocky Mountain Laboratories prions yielded infectious prion nanoparticles including oligomers and microfilaments bound to lipid vesicles. Lipid analysis revealed the brain phospholipids that associate with prion protofilaments, as well as those that are specifically enriched in prion assemblies captured by the methylamine-modified copolymer. A comparison of the infectivity of PrP attached to SMA lipid particles in mice and hamsters indicated that these amphipathic polymers offer a valuable tool for high-yield production of intact, detergent-free prions that retain activity. This native prion isolation method provides an avenue for producing relevant prion:lipid targets and potentially other proteins that form multimeric assemblies and fibrils on membranes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.RA119.012348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307199PMC
June 2020

Mycobacterium chimaera Encephalitis Following Cardiac Surgery: A New Syndrome.

Clin Infect Dis 2020 02;70(4):692-695

Division of Infectious Diseases, University of Alberta, Edmonton, Canada.

We report the cases of 3 patients with fatal, disseminated Mycobacterium chimaera infections following cardiac surgeries. Progressive neurocognitive decline and death were explained by active granulomatous encephalitis, with widespread involvement of other organs. This syndrome is clinically elusive and, thus, may have caused deaths in prior reported series.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/cid/ciz497DOI Listing
February 2020

14-3-3 and enolase abundances in the CSF of Prion diseased rats.

Prion 2018 12;12(3-4):253-260. Epub 2018 Sep 12.

a Department of Agricultural, Food and Nutritional Sciences, Centre for Prions and Protein Folding Diseases , University of Alberta , Edmonton , Canada.

Creutzfeldt-Jakob disease (CJD) is characterized by an extended asymptomatic preclinical phase followed by rapid neurodegeneration. There are no effective treatments. CJD diagnosis is initially suspected based upon the clinical presentation of the disease and the exclusion of other etiologies. Neurologic symptoms are assessed in combination with results from cerebrospinal fluid (CSF) biomarker abundances, electroencephalography (EEG), magnetic resonance imaging (MRI), and in some countries, real-time quaking-induced conversion (RT-QuIC). Inconsistencies in sensitivities and specificities of prion disease biomarker abundance in CSF have been described, which can affect diagnostic certainty, but the utility of biomarkers for prognosis has not been fully explored. The clinical presentation of CJD is variable, and factors such as prion protein polymorphic variants, prion strain, and other genetic or environmental contributions may affect the disease progression, confounding the appearance or abundance of biomarkers in the CSF. These same factors may also affect the appearance or abundance of biomarkers, further confounding diagnosis. In this study, we controlled for many of these variables through the analysis of serial samples of CSF from prion-infected and control rats. Prion disease in laboratory rodents follows a defined disease course as the infection route and time, prion strain, genotype, and environmental conditions are all controlled. We measured the relative abundance of 14-3-3 and neuron-specific enolase (NSE) in CSF during the course of prion infection in rats. Even when disease-related, environmental and genetic variables were controlled, CSF 14-3-3 and NSE abundances were variable. Our study emphasizes the considerable diagnostic and prognostic limitations of these prion biomarkers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/19336896.2018.1513317DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6277185PMC
February 2019

High Dose and Delayed Treatment with Bile Acids Ineffective in RML Prion-Infected Mice.

Antimicrob Agents Chemother 2018 08 27;62(8). Epub 2018 Jul 27.

Centre for Prions & Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada

Prion diseases are a group of neurodegenerative diseases associated with the misfolding of the cellular prion protein (PrP) into the infectious form (PrP). There are currently no treatments for prion disease. Bile acids have the ability to protect hepatocytes from apoptosis and are neuroprotective in animal models of other protein-folding neurodegenerative diseases, including Huntington's, Parkinson's, and Alzheimer's disease. Importantly, bile acids are approved for clinical use in patients with cirrhosis and have recently been shown to be safe and possibly effective in pilot trials of patients with amyotrophic lateral sclerosis (ALS). We previously reported that the bile acid ursodeoxycholic acid (UDCA), given early in disease, prolonged incubation periods in male RML-infected mice. Here, we expand on this result to include tauro-ursodeoxycholic acid (TUDCA) treatment trials and delayed UDCA treatment. We demonstrate that despite a high dose of TUDCA given early in disease, there was no significant difference in incubation periods between treated and untreated cohorts, regardless of sex. In addition, delayed treatment with a high dose of UDCA resulted in a significant shortening of the average survival time for both male and female mice compared to their sex-matched controls, with evidence of increased BiP, a marker of apoptosis, in treated female mice. Our findings suggest that treatment with high-dose TUDCA provides no therapeutic benefit and that delayed treatment with high-dose UDCA is ineffective and could worsen outcomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AAC.00222-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105847PMC
August 2018

Pharmacological chaperone reshapes the energy landscape for folding and aggregation of the prion protein.

Nat Commun 2016 06 27;7:12058. Epub 2016 Jun 27.

Department of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2E1.

The development of small-molecule pharmacological chaperones as therapeutics for protein misfolding diseases has proven challenging, partly because their mechanism of action remains unclear. Here we study Fe-TMPyP, a tetrapyrrole that binds to the prion protein PrP and inhibits misfolding, examining its effects on PrP folding at the single-molecule level with force spectroscopy. Single PrP molecules are unfolded with and without Fe-TMPyP present using optical tweezers. Ligand binding to the native structure increases the unfolding force significantly and alters the transition state for unfolding, making it more brittle and raising the barrier height. Fe-TMPyP also binds the unfolded state, delaying native refolding. Furthermore, Fe-TMPyP binding blocks the formation of a stable misfolded dimer by interfering with intermolecular interactions, acting in a similar manner to some molecular chaperones. The ligand thus promotes native folding by stabilizing the native state while also suppressing interactions driving aggregation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms12058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4931252PMC
June 2016

Dural Reduction Surgery: A Treatment Option for Frontotemporal Brain Sagging Syndrome.

Can J Neurol Sci 2016 Jul 14;43(4):593-5. Epub 2016 Mar 14.

2Department of Medicine,University of Alberta,Edmonton,Alberta,Canada.

Frontotemporal brain sagging syndrome is a dementia associated with hypersomnolence, personality changes, and features of intracranial hypotension on magnetic resonance imaging. The literature is sparse with respect to treatment options; many patients simply worsen. We present a case in which this syndrome responded to lumbar dural reduction surgery. Postoperative magnetic resonance imaging indicated normalization of brain sagging and lumbar intrathecal pressure. Although no evidence of cerebrospinal leak was found, extremely thin dura was noted intraoperatively, suggesting that a thin and incompetent dura could result in this low-pressure syndrome. Clinicians who encounter this syndrome should consider dural reduction surgery as a treatment strategy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1017/cjn.2016.3DOI Listing
July 2016

Toll-like receptor-mediated immune response inhibits prion propagation.

Glia 2016 Jun 16;64(6):937-51. Epub 2016 Feb 16.

Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada.

Prion diseases are progressive neurodegenerative disorders affecting humans and various mammals. The prominent neuropathological change in prion diseases is neuroinflammation characterized by activation of neuroglia surrounding prion deposition. The cause and effect of this cellular response, however, is unclear. We investigated innate immune defenses against prion infection using primary mixed neuronal and glial cultures. Conditional prion propagation occurred in glial cultures depending on their immune status. Preconditioning of the cells with the toll-like receptor (TLR) ligand, lipopolysaccharide, resulted in a reduction in prion propagation, whereas suppression of the immune responses with the synthetic glucocorticoid, dexamethasone, increased prion propagation. In response to recombinant prion fibrils, glial cells up-regulated TLRs (TLR1 and TLR2) expression and secreted cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, granulocyte-macrophage colony-stimulating factor, and interferon-β). Preconditioning of neuronal and glial cultures with recombinant prion fibrils inhibited prion replication and altered microglial and astrocytic populations. Our results provide evidence that, in early stages of prion infection, glial cells respond to prion infection through TLR-mediated innate immunity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/glia.22973DOI Listing
June 2016

Deposition pattern and subcellular distribution of disease-associated prion protein in cerebellar organotypic slice cultures infected with scrapie.

Front Neurosci 2015 4;9:410. Epub 2015 Nov 4.

German Center for Neurodegenerative Diseases Bonn, Germany ; Department of Neurology, Rheinische Friedrich-Wilhelms-University of Bonn Bonn, Germany.

Organotypic cerebellar slices represent a suitable model for characterizing and manipulating prion replication in complex cell environments. Organotypic slices recapitulate prion pathology and are amenable to drug testing in the absence of a blood-brain-barrier. So far, the cellular and subcellular distribution of disease-specific prion protein in organotypic slices is unclear. Here we report the simultaneous detection of disease-specific prion protein and central nervous system markers in wild-type mouse cerebellar slices infected with mouse-adapted prion strain 22L. The disease-specific prion protein distribution profile in slices closely resembles that in vivo, demonstrating granular spot like deposition predominately in the molecular and Purkinje cell layers. Double immunostaining identified abnormal prion protein in the neuropil and associated with neurons, astrocytes and microglia, but absence in Purkinje cells. The established protocol for the simultaneous immunohistochemical detection of disease-specific prion protein and cellular markers enables detailed analysis of prion replication and drug efficacy in an ex vivo model of the central nervous system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnins.2015.00410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631830PMC
November 2015

Structure-Based Peptide Design to Modulate Amyloid Beta Aggregation and Reduce Cytotoxicity.

PLoS One 2015 12;10(6):e0129087. Epub 2015 Jun 12.

Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada; Department of Medicine (Neurology), University of Alberta, Edmonton, Alberta, Canada; Neurosciences and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.

The deposition of Aβ peptide in the brain is the key event in Alzheimer disease progression. Therefore, the prevention of Aβ self assembly into disease-associated oligomers is a logical strategy for treatment. π stacking is known to provide structural stability to many amyloids; two phenylalanine residues within the Aβ 14-23 self recognition element are in such an arrangement in many solved structures. Therefore, we targeted this structural stacking by substituting these two phenylalanine residues with their D-enantiomers. The resulting peptides were able to modulate Aβ aggregation in vitro and reduce Aβ cytotoxicity in primary neuronal cultures. Using kinetic analysis of fibril formation, electron microscopy and dynamic light scattering characterization of oligomer size distributions, we demonstrate that, in addition to altering fibril structural characteristics, these peptides can induce the formation of larger amorphous aggregates which are protective against toxic oligomers, possibly because they are able to sequester the toxic oligomers during co-incubation. Alternatively, they may alter the surface structure of the oligomers such that they can no longer interact with cells to induce toxic pathways.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0129087PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4466325PMC
March 2016

Bile Acids Reduce Prion Conversion, Reduce Neuronal Loss, and Prolong Male Survival in Models of Prion Disease.

J Virol 2015 Aug;89(15):7660-72

Unlabelled: Prion diseases are fatal neurodegenerative disorders associated with the conversion of cellular prion protein (PrPC) into its aberrant infectious form (PrPSc). There is no treatment available for these diseases. The bile acids tauroursodeoxycholic acid(TUDCA) and ursodeoxycholic acid (UDCA) have been recently shown to be neuroprotective in other protein misfolding disease models, including Parkinson’s, Huntington’s and Alzheimer’s diseases, and also in humans with amyotrophic lateral sclerosis.Here, we studied the therapeutic efficacy of these compounds in prion disease. We demonstrated that TUDCA and UDCA substantially reduced PrP conversion in cell-free aggregation assays, as well as in chronically and acutely infected cell cultures. This effect was mediated through reduction of PrPSc seeding ability, rather than an effect on PrPC. We also demonstrated the ability of TUDCA and UDCA to reduce neuronal loss in prion-infected cerebellar slice cultures. UDCA treatment reduced astrocytosis and prolonged survival in RML prion-infected mice. Interestingly, these effects were limited to the males, implying a gender-specific difference in drug metabolism. Beyond effects on PrPSc, we found that levels of phosphorylated eIF2 were increased at early time points, with correlated reductions in postsynaptic density protein 95. As demonstrated for other neurodegenerative diseases, we now show that TUDCA and UDCA may have a therapeutic role in prion diseases, with effects on both prion conversion and neuroprotection. Our findings, together with the fact that these natural compounds are orally bioavailable, permeable to the blood-brain barrier, and U.S. Food and Drug Administration-approved for use in humans, make these compounds promising alternatives for the treatment of prion diseases.

Importance: Prion diseases are fatal neurodegenerative diseases that are transmissible to humans and other mammals. There are no disease-modifying therapies available, despite decades of research. Treatment targets have included inhibition of protein accumulation,clearance of toxic aggregates, and prevention of downstream neurodegeneration. No one target may be sufficient; rather, compounds which have a multimodal mechanism, acting on different targets, would be ideal. TUDCA and UDCA are bile acids that may fulfill this dual role. Previous studies have demonstrated their neuroprotective effects in several neurodegenerative disease models, and we now demonstrate that this effect occurs in prion disease, with an added mechanistic target of upstream prion seeding. Importantly, these are natural compounds which are orally bioavailable, permeable to the blood-brain barrier, and U.S.Food and Drug Administration-approved for use in humans with primary biliary cirrhosis. They have recently been proven efficacious in human amyotrophic lateral sclerosis. Therefore, these compounds are promising options for the treatment of prion diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01165-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4505631PMC
August 2015

The therapeutic potential of chemical chaperones in protein folding diseases.

Prion 2014 Mar-Apr;8(2). Epub 2014 May 12.

Department of Medicine - Division of Neurology; Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton, AB Canada.

Several neurodegenerative diseases are caused by defects in protein folding, including Alzheimer, Parkinson, Huntington, and prion diseases. Once a disease-specific protein misfolds, it can then form toxic aggregates which accumulate in the brain, leading to neuronal dysfunction, cell death, and clinical symptoms. Although significant advances have been made toward understanding the mechanisms of protein aggregation, there are no curative treatments for any of these diseases. Since protein misfolding and the accumulation of aggregates are the most upstream events in the pathological cascade, rescuing or stabilizing the native conformations of proteins is an obvious therapeutic strategy. In recent years, small molecules known as chaperones have been shown to be effective in reducing levels of misfolded proteins, thus minimizing the accumulation of aggregates and their downstream pathological consequences. Chaperones are classified as molecular, pharmacological, or chemical. In this mini-review we summarize the modes of action of different chemical chaperones and discuss evidence for their efficacy in the treatment of protein folding diseases in vitro and in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4189890PMC
http://dx.doi.org/10.4161/pri.28938DOI Listing
April 2015

The mechanism of membrane disruption by cytotoxic amyloid oligomers formed by prion protein(106-126) is dependent on bilayer composition.

J Biol Chem 2014 Apr 19;289(15):10419-10430. Epub 2014 Feb 19.

Molecular Structure and Function Program, The Hospital for Sick Children, Toronto, Ontario M5G 1X8; Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8. Electronic address:

The formation of fibrillar aggregates has long been associated with neurodegenerative disorders such as Alzheimer and Parkinson diseases. Although fibrils are still considered important to the pathology of these disorders, it is now widely understood that smaller amyloid oligomers are the toxic entities along the misfolding pathway. One characteristic shared by the majority of amyloid oligomers is the ability to disrupt membranes, a commonality proposed to be responsible for their toxicity, although the mechanisms linking this to cell death are poorly understood. Here, we describe the physical basis for the cytotoxicity of oligomers formed by the prion protein (PrP)-derived amyloid peptide PrP(106-126). We show that oligomers of this peptide kill several mammalian cells lines, as well as mouse cerebellar organotypic cultures, and we also show that they exhibit antimicrobial activity. Physical perturbation of model membranes mimicking bacterial or mammalian cells was investigated using atomic force microscopy, polarized total internal reflection fluorescence microscopy, and NMR spectroscopy. Disruption of anionic membranes proceeds through a carpet or detergent model as proposed for other antimicrobial peptides. By contrast, when added to zwitterionic membranes containing cholesterol-rich ordered domains, PrP(106-126) oligomers induce a loss of domain separation and decreased membrane disorder. Loss of raft-like domains may lead to activation of apoptotic pathways, resulting in cell death. This work sheds new light on the physical mechanisms of amyloid cytotoxicity and is the first to clearly show membrane type-specific modes of action for a cytotoxic peptide.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M113.515866DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4036164PMC
April 2014

D-amino acid-based peptide inhibitors as early or preventative therapy in Alzheimer disease.

Prion 2014 Jan-Feb;8(1):119-24

Beta amyloid (Aβ) accumulation is recognized as a hallmark of Alzheimer disease (AD) pathology and the aggregation of Aβ peptide is hypothesized to drive pathogenesis. As such, Aβ is a logical target for therapeutic intervention and there have been many studies looking at diverse classes of drugs that target Aβ. Of concern is the recent failure of several clinical trials, highlighting the need for earlier, possibly preventative intervention, and raising the question of what form of Aβ is the best target. The Aβ oligomers are considered to be the toxic species, but many therapies, such as antibody therapies, target monomers, removing them as substrates for aggregation. Peptide inhibitors, in contrast, are able to interfere with the aggregation process itself. Designing peptide inhibitors requires some knowledge of Aβ structure; while there is structural information about the amyloid core of Aβ fibrils, the transient nature of oligomers makes them difficult to characterize. Fortunately, some interaction sites have been identified between monomers and oligomers of Aβ and these, plus known aggregation-prone sequences in Aβ, can serve as a basis for inhibitor design. In this mini-review we focus on D-amino acid based peptide inhibitors and discuss how their non-toxic and stable nature can be beneficial, while they specifically target aggregation-prone sequences within the Aβ peptide. Many peptide inhibitors have been designed using the LVFFA domain within Aβ to disrupt the self-assembly of Aβ peptide. While this may be sufficient to stop aggregation in vitro, other aggregation sites at the C-terminus may promote aggregation independently and the flexible N terminus may be a good target to induce clearance of aggregates. Ultimately, it may be a combination of targets that provides the best therapeutic strategy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4161/pri.28220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7030907PMC
February 2015

Early increase and late decrease of purkinje cell dendritic spine density in prion-infected organotypic mouse cerebellar cultures.

PLoS One 2013 2;8(12):e81776. Epub 2013 Dec 2.

Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Canada.

Prion diseases are infectious neurodegenerative diseases associated with the accumulation of protease-resistant prion protein, neuronal loss, spongiform change and astrogliosis. In the mouse model, the loss of dendritic spines is one of the earliest pathological changes observed in vivo, occurring 4-5 weeks after the first detection of protease-resistant prion protein in the brain. While there are cell culture models of prion infection, most do not recapitulate the neuropathology seen in vivo. Only the recently developed prion organotypic slice culture assay has been reported to undergo neuronal loss and the development of some aspects of prion pathology, namely small vacuolar degeneration and tubulovesicular bodies. Given the rapid replication of prions in this system, with protease-resistant prion protein detectable by 21 days, we investigated whether the dendritic spine loss and altered dendritic morphology seen in prion disease might also develop within the lifetime of this culture system. Indeed, six weeks after first detection of protease-resistant prion protein in tga20 mouse cerebellar slice cultures infected with RML prion strain, we found a statistically significant loss of Purkinje cell dendritic spines and altered dendritic morphology in infected cultures, analogous to that seen in vivo. In addition, we found a transient but statistically significant increase in Purkinje cell dendritic spine density during infection, at the time when protease-resistant prion protein was first detectable in culture. Our findings support the use of this slice culture system as one which recapitulates prion disease pathology and one which may facilitate study of the earliest stages of prion disease pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081776PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3847088PMC
September 2014

Infectious prions accumulate to high levels in non proliferative C2C12 myotubes.

PLoS Pathog 2013 7;9(11):e1003755. Epub 2013 Nov 7.

Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada ; Department of Agriculture, Food and Nutritional Sciences, University of Alberta, Edmonton, Alberta, Canada.

Prion diseases are driven by the strain-specific, template-dependent transconformation of the normal cellular prion protein (PrP(C)) into a disease specific isoform PrP(Sc). Cell culture models of prion infection generally use replicating cells resulting in lower levels of prion accumulation compared to animals. Using non-replicating cells allows the accumulation of higher levels of PrP(Sc) and, thus, greater amounts of infectivity. Here, we infect non-proliferating muscle fiber myotube cultures prepared from differentiated myoblasts. We demonstrate that prion-infected myotubes generate substantial amounts of PrP(Sc) and that the level of infectivity produced in these post-mitotic cells, 10(5.5) L.D.50/mg of total protein, approaches that observed in vivo. Exposure of the myotubes to different mouse-adapted agents demonstrates strain-specific replication of infectious agents. Mouse-derived myotubes could not be infected with hamster prions suggesting that the species barrier effect is intact. We suggest that non-proliferating myotubes will be a valuable model system for generating infectious prions and for screening compounds for anti-prion activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/journal.ppat.1003755DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3820720PMC
June 2014

Implications of prion polymorphisms.

Prion 2013 Jul-Aug;7(4):276-9. Epub 2013 Jun 27.

Centre for Prions and Protein Folding Diseases; University of Alberta; Edmonton, AB Canada.

The sequence of a host's prion protein (PrP) can affect that host's susceptibility to prion disease and is the primary basis for the species barrier to transmission. Yet within many species, polymorphisms of the prion protein gene (Prnp) exist, each of which can further affect susceptibility or influence incubation period, pathology and phenotype. As strains are defined by these features (incubation period, pathology, phenotype), polymorphisms may also lead to the preferential propagation or generation of certain strains. In our recent study of the mouse Prnp(a) and Prnp(b) polymorphisms (which produced the proteins PrP(a) and PrP(b), respectively), we found differences in aggregation tendency, strain adaptability and conformational variability. Comparing our in vitro data with that of in vivo studies, we found that differing incubation periods between Prnp(a) and Prnp(b) mice can primarily be explained on the basis of faster or more efficient aggregation of PrP(a). In addition, and more importantly, we found that the faithful propagation of strains in Prnp(b) mice can be explained by the ability of PrP(b) to adopt a wider range of conformations. This adaptability allows PrP(b) to successfully propagate the structural features of a seed. In contrast, Prnp(a) mice revert PrP(b) strains into PrP(a) -type strains, and overall they have a narrower distribution of incubation periods. This can be explained by PrP(a) having fewer preferred conformations. We propose that Prnp polymorphisms are one route by which certain prion strains may preferentially propagate. This has significant implications for prion disease, chronic wasting disease (CWD) in particular, as it is spreading through North America. Deer which are susceptible to CWD also carry polymorphisms which influence their susceptibility. If these polymorphisms also preferentially allow strain diversification and propagation, this may accelerate the crossing of species barriers and propagation of the disease up the food chain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4161/pri.25566DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3904311PMC
June 2014

Mouse prion protein polymorphism Phe-108/Val-189 affects the kinetics of fibril formation and the response to seeding: evidence for a two-step nucleation polymerization mechanism.

J Biol Chem 2013 Feb 2;288(7):4772-81. Epub 2013 Jan 2.

Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta T6G 2M8, Canada.

Prion diseases are fatal neurodegenerative disorders associated with the polymerization of the cellular form of prion protein (PrP(C)) into an amyloidogenic β-sheet infectious form (PrP(Sc)). The sequence of host PrP is the major determinant of host prion disease susceptibility. In mice, the presence of allele a (Prnp(a), encoding the polymorphism Leu-108/Thr-189) or b (Prnp(b), Phe-108/Val-189) is associated with short or long incubation times, respectively, following infection with PrP(Sc). The molecular bases linking PrP sequence, infection susceptibility, and convertibility of PrP(C) into PrP(Sc) remain unclear. Here we show that recombinant PrP(a) and PrP(b) aggregate and respond to seeding differently in vitro. Our kinetic studies reveal differences during the nucleation phase of the aggregation process, where PrP(b) exhibits a longer lag phase that cannot be completely eliminated by seeding the reaction with preformed fibrils. Additionally, PrP(b) is more prone to propagate features of the seeds, as demonstrated by conformational stability and electron microscopy studies of the formed fibrils. We propose a model of polymerization to explain how the polymorphisms at positions 108 and 189 produce the phenotypes seen in vivo. This model also provides insight into phenomena such as species barrier and prion strain generation, two phenomena also influenced by the primary structure of PrP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M112.414581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3576082PMC
February 2013

Prion disease: chemotherapeutic strategies.

Authors:
Valerie L Sim

Infect Disord Drug Targets 2012 Apr;12(2):144-60

Centre for Prions and Protein Folding Diseases, 204 EEB, University of Alberta, Edmonton, AB, Canada T6G 2M8.

Prion diseases, also known as transmissible spongiform encephalopathies, are invariably fatal neurodegenerative diseases for which there are no efficacious treatments. Thousands of compounds have been screened for anti-prion effect, and yet of those that have effect in vitro, very few show effect in vivo, especially if administered in the later stages of disease. However, with new techniques for early diagnosis being developed, and with further insight into the pathogenesis of early disease, including the role of oligomers and the contribution of accessory molecules and signalling cascades, the chance of finding a therapeutic strategy is increasing. Beyond clinical therapy, there is increasing need to find effective decontaminants for blood supplies, as variant Creutzfeldt Jakob Disease (vCJD) is transmissible by blood. Non-toxic preventative therapies are also needed, with ongoing cases of Bovine Spongiform Encephalopathy (BSE) and the spread of Chronic Wasting Disease (CWD) being a growing concern. A primary target for therapy has been the conversion of the normal form of prion protein (PrPC) to its abnormal counterpart (PrPSc). Many of the chemotherapeutic agents with antiprion effect share structural similarities, often being polyanionic or polycyclic. They may directly bind PrPC or PrPSc, or they may redistribute, sequester, or down-regulate PrPC, thus preventing its conversion. There have also been some novel approaches, including trapping PrPSc in a multimeric form such that it can no longer cause conversion, increasing clearance of PrPSc, targeting accessory molecules which play a role in conversion, targeting pathways which lead to neurodegeneration, and stem cell therapy. It may be that a combination of compounds will be necessary for maximal effect and there is evidence that synergistic responses occur with dual therapy. This updated review focuses primarily on chemicalbased treatments in light of developments in diagnostic technologies, including results from recent clinical trials, and proposes some promising new targets for prion therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2174/187152612800100161DOI Listing
April 2012

Characterization of heparin-induced glyceraldehyde-3-phosphate dehydrogenase early amyloid-like oligomers and their implication in α-synuclein aggregation.

J Biol Chem 2012 Jan 1;287(4):2398-409. Epub 2011 Dec 1.

Instituto Superior de Investigaciones Biológicas, CCT-Tucumán, Tucumán T4000ILI, Argentina.

Lewy bodies and Lewy neurites, neuropathological hallmarks of several neurological diseases, are mainly made of filamentous assemblies of α-synuclein. However, other macromolecules including Tau, ubiquitin, glyceraldehyde-3-phosphate dehydrogenase, and glycosaminoglycans are routinely found associated with these amyloid deposits. Glyceraldehyde-3-phosphate dehydrogenase is a glycolytic enzyme that can form fibrillar aggregates in the presence of acidic membranes, but its role in Parkinson disease is still unknown. In this work, the ability of heparin to trigger the amyloid aggregation of this protein at physiological conditions of pH and temperature is demonstrated by infrared and fluorescence spectroscopy, dynamic light scattering, small angle x-ray scattering, circular dichroism, and fluorescence microscopy. Aggregation proceeds through the formation of short rod-like oligomers, which elongates in one dimension. Heparan sulfate was also capable of inducing glyceraldehyde-3-phosphate dehydrogenase aggregation, but chondroitin sulfates A, B, and C together with dextran sulfate had a negligible effect. Aided with molecular docking simulations, a putative binding site on the protein is proposed providing a rational explanation for the structural specificity of heparin and heparan sulfate. Finally, it is demonstrated that in vitro the early oligomers present in the glyceraldehyde-3-phosphate dehydrogenase fibrillation pathway promote α-synuclein aggregation. Taking into account the toxicity of α-synuclein prefibrillar species, the heparin-induced glyceraldehyde-3-phosphate dehydrogenase early oligomers might come in useful as a novel therapeutic strategy in Parkinson disease and other synucleinopathies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M111.303503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3268401PMC
January 2012

Recent advances in prion chemotherapeutics.

Infect Disord Drug Targets 2009 Feb;9(1):81-91

Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA.

The transmissible spongiform encephalopathies are rapidly progressive and invariably fatal neurodegenerative diseases for which there are no proven efficacious treatments. Many approaches have been undertaken to find ways to prevent, halt, or reverse these prion diseases, with limited success to date. However, as both our understanding of pathogenesis and our ability to detect early disease increases, so do our potential therapeutic targets and our chances of finding effective drugs. There is increasing pressure to find effective decontaminants for blood supplies, as variant Creutzfeldt Jakob Disease (vCJD) has been shown to be transmissible by blood, and to find non-toxic preventative therapies, with ongoing cases of Bovine Spongiform Encephalopathy (BSE) and the spread of Chronic Wasting Disease (CWD). Within the realm of chemotherapeutic approaches, much research has focussed on blocking the conversion of the normal form of prion protein (PrP(c)) to its abnormal counterpart (PrP(res)). Structurally, these chemotherapeutic agents are often polyanionic or polycyclic and may directly bind PrP(c) or PrP(res), or act by redistributing, sequestering, or down-regulating PrP(c), thus preventing its conversion. There are also some polycationic compounds which proport to enhance the clearance of PrP(res). Other targets include accessory molecules such as the laminin receptor precursor which influences conversion, or cell signalling molecules which may be required for pathogenesis. Of recent interest are the possible neuroprotective effects of some drugs. Importantly, there is evidence that combining compounds may provide synergistic responses. This review provides an update on current testing methods, therapeutic targets, and promising candidates for chemical-based therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3347484PMC
http://dx.doi.org/10.2174/1871526510909010081DOI Listing
February 2009

Ultrastructures and strain comparison of under-glycosylated scrapie prion fibrils.

Neurobiol Aging 2009 Dec 3;30(12):2031-42. Epub 2008 Apr 3.

Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840, United States.

Prions, composed primarily of misfolded, often fibrillar, polymers of prion protein, have poorly understood structures. Heavy surface glycosylation may obscure visualization of their fibrillar cores, so we purified severely under-glycosylated prion protein fibrils from scrapie-infected transgenic mice expressing anchorless prion protein. Using electron and atomic force microscopy, we obtained dimensions and morphological information about prion protein core protofilaments which variably intertwined to form scrapie fibrils. Occasional isolated protofilaments were observed, suggesting that the lateral association of protofilaments is neither essential nor invariant in prion protein polymerization. Strain comparisons suggested basic structural differences; ME7 and 22L fibrils contained thinner protofilaments, 22L fibrils preferred left-handed twists, and 22L fibril periodicities averaged 106nm per half-turn, compared with 64 and 66nm for RML and ME7 fibrils, respectively. The strains displayed overlapping fibril morphologies, providing evidence that prion fibril morphology is influenced, but not dictated, by strain-dependent differences in protofilament structure. These measurements of the amyloid core of scrapie fibrils should aid development of models of prion structure and strain determination.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neurobiolaging.2008.02.016DOI Listing
December 2009