Investigations on the role of rab7 in prion infection
Date
2022-06
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Abstract
Prion diseases are fatal and infectious neurodegenerative diseases caused by the misfolding of the cellular prion protein PrPc into its infectious isoform PrPSc, which comprises the main if not the only constituent of prions. In response to prion infection certain cellular impairments such as reduced membrane association of Rab7, compromised lysosomal acidification and elevated cholesterol levels are observed. Here, we found that prion infected primary neurons are marked by an increased expression of active Rab7 (Rab7.GTP) levels during the initial stages of the infection, followed by a loss in its levels as the infection progresses. However, astrocytes in prion infected terminal mice upregulate the active Rab7 expression. The reduced Rab7 activation is linked to its reduced ubiquitination status. In neurons, the loss in active Rab7 leads to a delay in the Rab7 mediated trafficking of LDL to the lysosomes and Golgi, resulting in a defective feedback regulation of cholesterol metabolism. This in turn triggers de novo cholesterol synthesis. Over-expression of a constitutively active mutant of Rab7 in prion infected neuronal cell-lines rescues the delay in LDL trafficking, restores the normal cholesterol levels and reduces prion propagation. Inspired by the differential kinetics of Rab7 activation during prion infection and the cell-type specific differences of Rab7 activation in the prion infected terminal mouse brain, we studied the Rab7 interactome using quantitative proteomics. We identified a loss in the Rab7 interactome associated with ubiquitination in prion infected cells and synaptic signalling in prion infected brains, whereas proteins in the mitochondrial respiratory chain were observed to be lost in both cases. The enriched pathways identified in Rab7 interactome were linked to mRNA transport and degradation to name some. In the prion-infected brain, we identified the cholesterol esterification pathway to be enriched in the Rab7 interactome in the brain. These studies indicate a possible involvement of Rab7 in the above-mentioned pathways and suggest candidate proteins to be evaluated for their potential to ubiquitinate Rab7, as a functional impairment of the Rab7 ubiquitin ligase can cause reduced activation observed in prion infections.
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Keywords
Rab7, cholesterol, prion infection, Rab7 interactome
Citation
Cherry, P. (2022). Investigations on the role of rab7 in prion infection (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.