Investigating the Heat Shock Protein 110 as a Modifier Of Prion Infection In Vitro and In Vivo
Date
2021-11-22
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Abstract
Prion diseases are fatal transmissible neurodegenerative disorders affecting humans and wild or domesticated animals. Molecularly, they are caused by a misfolding of the cellular prion protein (PrPC) into a highly pathogenic isoform (PrPSc). Over time, PrPSc aggregates into fibrils which are fragmented to recruit and convert further PrPC. Even though this process is essential to the replication of PrPSc, the molecular players involved remain unknown. Based on reports showing that the molecular chaperone Hsp110 forms part of a mammalian disaggregation machinery, we hypothesize that Hsp110 is critical for the fragmentation of PrPSc in prion propagation. To test this, Hsp110 levels were manipulated in prion-infected cultured cells: Transient knock-down was found to reduce PrPSc levels in neuronal and non-neuronal cells, while transient overexpression increased PrPSc in a dose-dependent manner in neuronal cells. Knockout of Hsp110 by CRISPR/Cas9 reduced the susceptibility of neuronal cells to prion infection. Overall, the effects of Hsp110 manipulation in cultured cells are consistent with an involvement of Hsp110 in prion propagation. Next, mice overexpressing Hsp110 (TgApg-1 mice) were inoculated with the 22L and Me7 prion strains. Compared to WT mice, TgApg-1 mice showed significantly prolonged survival after Me7- but not 22L-inoculation. To test whether this prolongation of survival occurred due to altered PrPSc propagation, the biochemical features of PrPSc were examined in terminally-diseased animals. No difference was found between PrPSc of WT or TgApg-1 mice, suggesting that Hsp110 overexpression may have been protective independently of PrPSc. Finally, the effect of compounds broadly inducing the expression of heat shock proteins was examined. WT FVB mice inoculated with RML or Me7 prions were treated with either celastrol, geranylgeranylacetone or vehicle. No difference in survival time was found between the groups, despite evidence of heat-shock response induction in drug-treated animals. These results suggest that broad heat-shock induction is not protective in prion infection. Overall, our in vitro studies are consistent with a role of Hsp110 in PrPSc fragmentation, but our in vivo work is inconclusive in this regard. We, therefore, propose further research aimed at exploring prion fragmentation and the role of Hsp110 in prion infection.
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Keywords
Prion disease, Neurodegeneration, Chaperones, Heat shock proteins, Protein misfolding
Citation
Marrero Winkens, C. (2021). Investigating the Heat Shock Protein 110 as a modifier of prion infection in vitro and in vivo (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.