Quaternary Structure Changes for PrP Sc Predate PrP C Downregulation and Neuronal Death During Progression of Experiment
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Quaternary Structure Changes for PrPSc Predate PrPC Downregulation and Neuronal Death During Progression of Experimental Scrapie Disease Ghazaleh Eskandari-Sedighi 1,2 & Leonardo M. Cortez 2,3 & Jing Yang 2 & Nathalie Daude 2 & Klinton Shmeit 2 & Valerie Sim 2,3 & David Westaway 1,2 Received: 28 March 2020 / Accepted: 1 September 2020 # The Author(s) 2020
Abstract Prion diseases are fatal neurodegenerative diseases in mammals with the unique characteristics of misfolding and aggregation of the cellular prion protein (PrPC) to the scrapie prion (PrPSc). Although neuroinflammation and neuronal loss feature within the disease process, the details of PrPC/PrPSc 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 PrPC and PrPSc 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 PrPC levels at pre-clinical stages of the disease and demonstrate that these decreases become significant before neuronal loss. We also identified the earliest PrPSc 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 PrPSc 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. Keywords Prion disease . RML . Neuronal loss . PrPC downregulation . PrP assemblies . Asymmetric flow field-flow fractionation
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12035-020-02112-z) contains supplementary material, which is available to authorized users. * David Westaway [email protected] 1
Department of Biochemistry, University of Alberta, Edmonton, AB, Canada
2
Centre for Prions and Protein Folding Diseases, University of Alberta, 204 Brain and Aging Research Building, Edmonton, AB T6G 2M8, Canada
3
Department of Medicine, Division of Neurology, University of Alberta, Edmonton, AB, Canada
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