Browsing by Author "Cherry, Pearl"

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    Investigations on the role of rab7 in prion infection
    (2022-06) Cherry, Pearl; Gilch, Sabine; Kar, Satyabrata; Braun, Janice; Haigh, Cathryn; Tsutsui, Shigeki
    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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    Oral administration of repurposed drug targeting Cyp46A1 increases survival times of prion infected mice
    (2021-04-01) Ali, Tahir; Hannaoui, Samia; Nemani, Satish; Tahir, Waqas; Zemlyankina, Irina; Cherry, Pearl; Shim, Su Y; Sim, Valerie; Schaetzl, Hermann M; Gilch, Sabine
    Abstract Prion diseases are fatal, infectious, and incurable neurodegenerative disorders caused by misfolding of the cellular prion protein (PrPC) into the infectious isoform (PrPSc). 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 PrPSc propagation in prion-infected cells while preserving physiological PrPC 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.