Overexpression of quality control proteins reduces prion conversion in prion-infected cells

Simrika Thapa,Basant Abdulrahman,Dalia H Abdelaziz,Li Lu,Manel Ben Aissa,Hermann M Schatzl

doi:10.1074/jbc.ra118.002754

Simrika Thapa, Basant Abdulrahman + Show 4 more

Open Access

https://doi.org/10.1074/jbc.ra118.002754

Copy DOI

Abstract

Prion diseases are fatal infectious neurodegenerative disorders in humans and other animals and are caused by misfolding of the cellular prion protein (PrPC) into the pathological isoform PrPSc. These diseases have the potential to transmit within or between species, including zoonotic transmission to humans. Elucidating the molecular and cellular mechanisms underlying prion propagation and transmission is therefore critical for developing molecular strategies for disease intervention. We have shown previously that impaired quality control mechanisms directly influence prion propagation. In this study, we manipulated cellular quality control pathways in vitro by stably and transiently overexpressing selected quality control folding (ERp57) and cargo (VIP36) proteins and investigated the effects of this overexpression on prion propagation. We found that ERp57 or VIP36 overexpression in persistently prion-infected neuroblastoma cells significantly reduces the amount of PrPSc in immunoblots and prion-seeding activity in the real-time quaking-induced conversion (RT-QuIC) assay. Using different cell lines infected with various prion strains confirmed that this effect is not cell type– or prion strain–specific. Moreover, de novo prion infection revealed that the overexpression significantly reduced newly formed PrPSc in acutely infected cells. ERp57-overexpressing cells significantly overcame endoplasmic reticulum stress, as revealed by expression of lower levels of the stress markers BiP and CHOP, accompanied by a decrease in PrP aggregates. Furthermore, application of ERp57-expressing lentiviruses prolonged the survival of prion-infected mice. Taken together, improved cellular quality control via ERp57 or VIP36 overexpression impairs prion propagation and could be utilized as a potential therapeutic strategy.

Highlights

Prion diseases are fatal infectious neurodegenerative disorders in humans and other animals and are caused by misfolding of the cellular prion protein (PrPC) into the pathological isoform PrPSc
Chronic endoplasmic reticulum (ER) stress in cells has been linked to up-regulation of signaling pathways that lead to apoptosis and result in cell death and neurodegeneration [38, 39]
Our previous work showed that the ER stress–mediated increase in PrP aggregates and in PrPSc can be reversed by transient overexpression of selected quality control molecules such as ERGIC-53 and EDEM3 [24]

Summary

To whom correspondence should be addressed

Prion diseases are transmissible spongiform encephalopathies characterized by distinctive spongiform appearance and loss of neurons in the brain. Transmissible spongiform encephalopathies include Creutzfeldt–Jakob disease in humans, scrapie in sheep, bovine spongiform encephalopathy in cattle, and chronic wasting disease in cervids These diseases are caused by accumulation of the misfolded infectious isoform (PrPSc) of the normal cellular prion protein (PrPC) in the brain and other tissues [1,2,3]. Several reports have suggested that incorrectly folded forms of PrPC and PrPSc accumulate during ER stress in prion disease models [21,22,23,24] It has been shown in in vitro and in vivo models that prion infection resulted in cells undergoing ER stress, which further facilitates the formation of misfolded PrPC and increased prion conversion (22, 24 –26). Manipulation of the protein quality control mechanisms could lead to reduced PrPSc conversion

Results

Discussion

Experimental procedures

Ethics statement