Destabilizing polymorphism in cervid prion protein hydrophobic core determines prion conformation and conversion efficiency

Abstract

Prion diseases are infectious neurodegenerative disorders of humans and animals caused by misfolded forms of the cellular prion protein PrPC. Prions cause disease by converting PrPC into aggregation-prone PrPSc. Chronic wasting disease (CWD) is the most contagious prion disease with substantial lateral transmission, affecting free-ranging and farmed cervids. Although the PrP primary structure is highly conserved among cervids, the disease phenotype can be modulated by species-specific polymorphisms in the prion protein gene. How the resulting amino-acid substitutions impact PrPC and PrPSc structure and propagation is poorly understood. We investigated the effects of the cervid 116A>G substitution, located in the most conserved PrP domain, on PrPC structure and conversion and on 116AG-prion conformation and infectivity. Molecular dynamics simulations revealed structural de-stabilization of 116G-PrP, which enhanced its in vitro conversion efficiency when used as recombinant PrP substrate in real-time quaking-induced conversion (RT-QuIC). We demonstrate that 116AG-prions are conformationally less stable, show lower activity as a seed in RT-QuIC and exhibit reduced infectivity in vitro and in vivo. Infectivity of 116AG-prions was significantly enhanced upon secondary passage in mice, yet conformational features were retained. These findings indicate that structurally de-stabilized PrPC is readily convertible by cervid prions of different genetic background and results in a prion conformation adaptable to cervid wild-type PrP. Conformation is an important criterion when assessing transmission barrier, and conformational variants can target a different host range. Therefore, a thorough analysis of CWD isolates and re-assessment of species-barriers is important in order to fully exclude a zoonotic potential of CWD.

Cellulose ether treatment in vivo generates chronic wasting disease prions with reduced protease resistance and delayed disease progression

“…; Hannaoui et al . ). In fact, a group of tgElk mice treated with CEs and inoculated with different CWD isolates showed a significant survival prolongation of up to + 32% (Table ).…”

“…; Hannaoui et al . ) that could more easily cross the transmission barrier in addition to conflicting data in nonhuman primates (Race et al . ; Barria et al .…”

“…); the MD and WTD‐116AG (Hannaoui et al . ) isolates were from wild animals at the terminal stage of disease generously provided by Dr Trent Bollinger (University of Saskatchewan, Saskatoon, Saskatchewan, Canada).…”

“…We used three different CWD isolates from CWD-infected elk, MD, and WTD. The CWDelk isolate containing strain CWD2 was a pool of 3 CWD-elk (132MM) animals experimentally challenged by oral inoculation (Angers et al 2010), kindly provided by Dr Stefanie Czub, Canadian Food Inspection Agency (Basu et al 2012); the MD and WTD-116AG (Hannaoui et al 2017a) isolates were from wild animals at the terminal stage of disease generously provided by Dr Trent Bollinger (University of Saskatchewan, Saskatoon, Saskatchewan, Canada).…”

“…Real-time QuIC was performed as described previously (John et al 2013;Hannaoui et al 2017a). Briefly, reactions were set up in assay buffer containing 20 mM sodium phosphate (pH 6.9; cat#342483; Sigma-Aldrich), 300 mM NaCl (cat#S3014; Sigma-Aldrich), 1 mM EDTA (cat# E4884; Sigma-Aldrich), 10 lM Thioflavin T (cat# T3516; Sigma-Aldrich) and 0.1 mg/mL mouse recombinant PrP (mo-rPrP) substrate.…”