# Oligosaccharyltransferase (OST) complex inhibition effectively treats rodent and human prions

## TL;DR

Blocking the OST complex reduces prion protein levels and prevents prion spread in both rodent and human models.

## Contribution

OST inhibition is a novel therapeutic strategy effective against multiple prion strains, including human prions.

## Key findings

- OST inhibition reduced cell surface PrPC by 50% in various cell types.
- OST inhibition prevented PrPSc amplification in PMCA reactions.
- OST inhibition was effective against human sCJD prions in cerebral organoids.

## Abstract

Prion diseases are invariably fatal neurodegenerative diseases that occur when the prion protein misfolds into a pathogenic form. There are currently no clinical treatments or cures for prion disease. Current challenges in the development of prion therapeutics include prion strain specificity, which can cause the emergence of drug-resistant prions, and lack of efficacy in treating human prions despite promising results in rodent models. Here we identify a novel therapeutic target for prion disease: the oligosaccharyltransferase (OST) complex. The OST complex is responsible for transferring the mature glycan to the acceptor polypeptide during N-glycosylation. We found that inhibiting OST effectively treats rodent prions in various dividing and non-dividing cell types. Importantly, we also demonstrate efficacy in treating human sCJD prions in non-dividing cerebral organoids. Inhibition of OST results in a 50% reduction in cell surface expression of the prion protein, PrPC. In addition, lysates of cells treated with the OST inhibitor NGI-1 were unable to amplify PrPSc seeds in Protein Misfolding Cyclic Amplification (PMCA) reactions. In summary, our results identify OST as a novel therapeutic target that regulates both the abundance of cell surface PrPC as well as its ability to convert into multiple strains of PrPSc, including human prions, in various in vitro systems.

Prion diseases, such as Creutzfeldt–Jakob disease, are fatal brain disorders caused when a normal protein (PrPC) misfolds into a harmful form that spreads through the brain. There are no effective treatments, and drug development has been hampered by “strain” differences in prions that can lead to resistance and by therapies that work in rodents but not in humans.

This study identifies a new treatment target: the oligosaccharyltransferase (OST) complex, a cellular machine that adds sugar groups to proteins. Blocking OST with a small molecule (NGI-1) limited prion growth in multiple types of rodent cells, including non-dividing cells, and—critically—also worked against human sporadic CJD prions in laboratory-grown human brain organoids. OST inhibition cut the amount of normal prion protein on cell surfaces in half, reducing the raw material available to convert into the disease-causing form. In addition, extracts from NGI-1–treated cells could no longer drive prion formation in a sensitive lab amplification test.

These results suggest that targeting OST may offer a new strategy that works across different prion strains, including human ones.