Spongiform Encephalopathy in Transgenic Mice Expressing a Point Mutation in the β2–α2 Loop of the Prion Protein

Abstract

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases attributed to misfolding of the cellular prion protein, PrPC, into a β-sheet-rich, aggregated isoform, PrPSc. We previously found that expression of mouse PrP with the two amino acid substitutions S170N and N174T, which result in high structural order of the β2–α2 loop in the NMR structure at pH 4.5 and 20 °C, caused transmissible de novo prion disease in transgenic mice. Here we report that expression of mouse PrP with the single-residue substitution D167S, which also results in a structurally well-ordered β2–α2 loop at 20 °C, elicits spontaneous PrP aggregation in vivo. Transgenic mice expressing PrPD167S developed a progressive encephalopathy characterized by abundant PrP plaque formation, spongiform change, and gliosis. These results add to the evidence that the β2–α2 loop has an important role in intermolecular interactions, including that it may be a key determinant of prion protein aggregation.

Prion replication without host adaptation during interspecies transmissions

“…Spontaneous neurodegeneration in Tg mice in which the mouse PrP β2-α2 loop was replaced by that of horse PrP (29) contrasted structural predictions of intrinsic horse PrP C resistance to conformational conversion (27). To address this inconsistency, we created TgEq expressing horse PrP C (EqPrP C ) at levels approximately twofold higher than PrP C in horse brains (Fig.…”

“…Although β2-α2 loop rigidity was thought to potentiate PrP C to PrP Sc conversion (24), subsequent studies revealed that PrP C of species considered resistant to prions, including horses, also contained rigid β2-α2 loops (25)(26)(27). Adding additional complexity, Tg mice expressing mouse PrP C containing rigid β2-α2 loops from elk or horse PrP spontaneously developed prion diseases (28,29). To clarify the effect of the horse PrP β2-α2 loop on prion conversion and to model susceptibility of this at-risk species, we produced Tg mice expressing horse PrP.…”

Structural plasticity of the cellular prion protein and implications in health and disease

“…Despite extensive investigations, the physiological function of PrP C in healthy organisms as well as the mechanistic aspects of its pathophysiological role remain elusive (4-9). Although the PrP Sc form found in diseased tissue has been intensively studied, other approaches underline the importance of PrP C as a potential target for TSE prevention and medical intervention after outbreak of the disease (10-12), with a special focus on rigid-loop cellular prion proteins (RL-PrP C s) (11,(13)(14)(15), which are investigated in this paper.A common PrP C fold for a globular domain formed by the polypeptide segment of residues 125-228 in mouse PrP (mPrP) [see Schätzl et al (16) for the numeration in different species], with three α-helices and a short two-stranded antiparallel β-sheet, has been observed for the cellular prion proteins of all mammalian species studied so far (17-27). For WT PrP of most species, parts of the backbone amide group NMR signals of residues in a loop between a β-strand, β2, and a helix, α2, are not observable in NMR spectra recorded with aqueous solutions at pH 4.5 and 20°C at a 1 H resonance frequency of 500 MHz (or higher) because of line broadening by conformational exchange; therefore, the β2-α2 loop in these PrP C s is poorly defined in NMR structures determined under these conditions.…”

“…This screen revealed a feature in the elk prion protein, where all backbone amide group NMR signals of the β2−α2 loop are observable at 20°C and a 1 H resonance frequency of 750 MHz; the β2−α2 loop is, therefore, well-defined in the NMR structure (23). This observation attracted special interest in the context of the CWD crisis of deer and elk in North America (34-37) and was followed up by structural studies of WT and specifically designed variant prion proteins (24-26, 28, 38), in vivo experiments with transgenic mice (11,13,14,39,40), and in vitro studies of correlations between the β2-α2 loop amino acid sequence and the propensity of PrP C to undergo transitions to PrP . In connection with animal experiments relating to CWD, the term RL-PrP C was introduced for PrP C s forming a structurally well-defined β2−α2 loop in the solution NMR structure at 20°C (39).…”

Current understanding of PrnP Genetics: A tool for Molecular Assisted Selection in Sheep Populations (A review)

“…It was later proven that the concerns were justified, as the first cases of a new form of Creutzfeldt-Jakob disease were diagnosed and confirmed in humans -vCJD - Collinge et al, 1996;Bruce et al, 1997;Scott, 1993) as a result of consumption of BSE-infected meat (Wilesmith et al, 1991). During the BSE epidemic episodes, domestic cats, as well as big cats and exotic ruminants in captivity were exposed to and infected with the BSE agent through the ingestion of MBM obtained from sick animals (Baylis, 2002; Peet and Curran, 1992; Willoughby 1992; Foster et al, 1993;Sigurdson, 2011;Bencsik et al, 2009;Eiden et al, 2010). Amidst this situation, the first measures taken by the EU Commission were banning MBM (94/381 / EC: Commission Decision), banning exports of beef from the UK (96/239 / EC: Commission Decision) and definition of a strategy which could highlight the presence of the infectious agent of BSE in small ruminants.…”