Efficient inhibition of infectious prions multiplication and release by targeting the exosomal pathway

Abstract

Exosomes are secreted membrane vesicles of endosomal origin present in biological fluids. Exosomes may serve as shuttles for amyloidogenic proteins, notably infectious prions, and may participate in their spreading in vivo. To explore the significance of the exosome pathway on prion infectivity and release, we investigated the role of the endosomal sorting complex required for transport (ESCRT) machinery and the need for ceramide, both involved in exosome biogenesis. Silencing of HRS-ESCRT-0 subunit drastically impairs the formation of cellular infectious prion due to an altered trafficking of cholesterol. Depletion of Tsg101-ESCRT-I subunit or impairment of the production of ceramide significantly strongly decreases infectious prion release. Together, our data reveal that ESCRT-dependent and -independent pathways can concomitantly regulate the exosomal secretion of infectious prion, showing that both pathways operate for the exosomal trafficking of a particular cargo. These data open up a new avenue to regulate prion release and propagation.

Stimulating the Release of Exosomes Increases the Intercellular Transfer of Prions

“…Processed forms of the specific neurodegenerative disease-associated proteins have been identified in exosomes, leading to the suggestion that exosomes could facilitate their intercellular spread. An example is the role of exosomes in transmission of infectious prions arising from misfolding of the prion protein (10,11,16).…”

Exosomes and the Prion Protein: More than One Truth

“…Further studies focusing on release of PrP Sc from cells not only provided evidence that PrP Sc associates with exosomes but also showed that release of PrP Sc and prion infectivity could be attenuated by interfering with exosome biogenesis through inhibition of the endosomal sorting complex required for transport (ESCRT; Alais et al, 2008; Vilette et al, 2015). In line with this study, further research showed that pharmacological stimulation of exosome release by treatment with the ionophore Monensin increased release of infectious exosomes.…”

Prions on the run: How extracellular vesicles serve as delivery vehicles for self-templating protein aggregates

“…Exosomal sorting is not restricted to PrP Sc , as PrP C is a normal constituent of intraluminal bodies in MVBs, 47,54 and is found in exosomal preparations of immortalized cell lines and primary cells of diverse origins 42,48,55-60 . Exosomes and microvesicles isolated from body fluids are also decorated with PrP C , suggesting that PrP C is a normal constituent of EVs 61,62 .…”

“…Both ceramide dependent and Tsg101-ESCRT mediated pathways contribute to exosomal prion secretion in 2 cellular TSE models 42,52 . While ESCRT Tsg101 subunit silencing directly affected exosome and PrP Sc secretion, a compound inhibiting the ceramide-dependent exosome pathway only marginally affected exosome secretion but led to selective exclusion of PrP Sc and infectivity from exosomes derived from a neuroglial cell line 42 . This is in contrast to a study using a murine hypothalamic cell line where chemical impairment of the ceramide-dependent pathway reduced exosomes and exosome-associated PrP C and PrP Sc 52 .…”