Protease-resistant prions selectively decrease Shadoo protein.

Joel C Watts,Stanley B Prusiner,Holger Wille,Abby Oehler,Stephen J Dearmond,Sumita Bhardwaj,Kurt Giles,Jan Stöhr,Neil Andrew Mabbott

doi:10.1371/journal.ppat.1002382

Joel C Watts, Stanley B Prusiner + Show 7 more

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https://doi.org/10.1371/journal.ppat.1002382

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Abstract

The central event in prion diseases is the conformational conversion of the cellular prion protein (PrPC) into PrPSc, a partially protease-resistant and infectious conformer. However, the mechanism by which PrPSc causes neuronal dysfunction remains poorly understood. Levels of Shadoo (Sho), a protein that resembles the flexibly disordered N-terminal domain of PrPC, were found to be reduced in the brains of mice infected with the RML strain of prions [1], implying that Sho levels may reflect the presence of PrPSc in the brain. To test this hypothesis, we examined levels of Sho during prion infection using a variety of experimental systems. Sho protein levels were decreased in the brains of mice, hamsters, voles, and sheep infected with different natural and experimental prion strains. Furthermore, Sho levels were decreased in the brains of prion-infected, transgenic mice overexpressing Sho and in infected neuroblastoma cells. Time-course experiments revealed that Sho levels were inversely proportional to levels of protease-resistant PrPSc. Membrane anchoring and the N-terminal domain of PrP both influenced the inverse relationship between Sho and PrPSc. Although increased Sho levels had no discernible effect on prion replication in mice, we conclude that Sho is the first non-PrP marker specific for prion disease. Additional studies using this paradigm may provide insight into the cellular pathways and systems subverted by PrPSc during prion disease.

Highlights

Prion diseases, such as Creutzfeldt-Jakob disease (CJD) in humans, bovine spongiform encephalopathy (BSE), and chronic wasting disease (CWD) in cervids, are invariably fatal neurodegenerative disorders caused by the accumulation of misprocessed prion protein (PrPSc) in the brain
Shadoo levels in the brain are a specific indicator of prion disease status, and it may be possible to exploit this observation for diagnostic purposes
We show that Shadoo itself is unlikely to influence prion disease, using Shadoo as a tool to probe the biology of prions may be a useful strategy for deciphering how prions damage the brain

Summary

Introduction

Prion diseases, such as Creutzfeldt-Jakob disease (CJD) in humans, bovine spongiform encephalopathy (BSE), and chronic wasting disease (CWD) in cervids, are invariably fatal neurodegenerative disorders caused by the accumulation of misprocessed prion protein (PrPSc) in the brain. Despite a clear involvement in pathogenesis, the mechanism by which PrPSc causes neuronal dysfunction during prion disease remains obscure. PrPC is known to interact with or reside in close spatial proximity to numerous other proteins in the cell membrane [6,7,8], none of these identified proteins has been shown to be associated with prion disease pathogenesis or prion replication. The mammalian prion protein family consists of three members: PrPC; Doppel (Dpl), a testes-specific protein involved in the proper functioning of the male reproductive system [9,10]; and Shadoo (Sho), a recently identified neuronal paralog of PrPC encoded by the Sprn gene [1,11]. The similarity between PrP and Sho is striking within the alanine/

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