Prion Strain Mutation Determined by Prion Protein Conformational Compatibility and Primary Structure

Abstract

Prions are infectious proteins composed of the abnormal disease-causing isoform PrPSc, which induces conformational conversion of the host-encoded normal cellular prion protein PrPC to additional PrPSc. The mechanism underlying prion strain mutation in the absence of nucleic acids remains unresolved. Additionally, the frequency of strains causing chronic wasting disease (CWD), a burgeoning prion epidemic of cervids, is unknown. Using susceptible transgenic mice, we identified two prevalent CWD strains with divergent biological properties but composed of PrPSc with indistinguishable biochemical characteristics. Although CWD transmissions indicated stable, independent strain propagation by elk PrPC, strain coexistence in the brains of deer and transgenic mice demonstrated unstable strain propagation by deer PrPC. The primary structures of deer and elk prion proteins differ at residue 226, which, in concert with PrPSc conformational compatibility, determines prion strain mutation in these cervids.

Characterization of Conformation-dependent Prion Protein Epitopes

“…Immunoblot probing with mAb 6H4 confirmed transgene expression in all cases. Consistent with this epitope location, PRC1 detected full-length elk PrP, C2, and PrP (27)(28)(29)(30) but failed to react with C1 following PNGase F-mediated removal of N-linked glycans; in contrast, mAb 6H4 detected full-length mouse and elk PrP, and both endogenously cleaved fragments (Fig. 3D).…”

“…Of the 25 clones from Rec Mo/ CerPrP-68 immunized mice, 14 had reproducibly strong reactivity against Rec Mo/CerPrP-68 by ELISA and Western blotting. Ultimately, four mAbs, originally coded as 9E9, 5C6, 7H11, and 9H9 (28,29), hereafter referred to as PRC (Prion Research Center) 1, 5, 7, and 9, respectively, were selected for further characterization. Hybridomas were cloned two additional times.…”

“…To address this, we infected RK13 cells stably expressing wild type and mutated versions of mouse or elk PrP with the respective species of prions, and we monitored the ability of mutated PrP to be converted to mouse or elk PrP (27)(28)(29)(30). The effects of mutations of various epitope components depended on whether they were expressed in the context of mouse or elk PrP.…”

“…In both PrP C and PrP Sc , asparagine-linked oligosaccharides are attached at residues 180 and 196, and a disulfide bond is formed between cysteine residues 178 and 213. In most examples of prion disease, in vitro treatment of PrP Sc with proteinase K (PK) results in cleavage of ϳ66 amino-terminal amino acids and persistence of a protease-resistant core referred to as PrP (27)(28)(29)(30). Endoproteolytic cleavage of PrP Sc following residue 88 results in a similar 21-kDa carboxyl-terminal fragment, referred to as C2, orig-* This work was supported, in whole or in part, by National Institutes of Health inally observed in the brains of patients with Creutzfeldt-Jakob disease (4), and is subsequently shown to be calpain-dependent (5).…”

Post-aggregation Oxidation of Mutant Huntingtin Controls the Interactions between Aggregates

“…Although exact roles of post-aggregation modifications in disease pathomechanisms remain to be established, insoluble aggregates are not considered to be inert products of protein misfolding but are able to change its morphologies and structures by post-aggregation modifications. Increasing evidence has recently supported the idea that different structures/morphologies of protein aggregates are related to distinct phenotypes (43,50,51); therefore, a possible outcome of post-aggregation modifications may be to modulate disease phenotypes/symptoms even after the onset of disease.…”