title: Different structural stability and toxicity of PrP(ARR) and PrP(ARQ) sheep prion protein variants.
abstract: The polymorphisms at amino acid residues 136, 154, and 171 in ovine prion protein (PrP) have been associated with different susceptibility to scrapie: animals expressing PrP(ARQ) [PrP(Ala136/Arg154/Gln171)] show vulnerability, whereas those that express PrP(ARR) [PrP(Ala136/Arg154/Arg171)] are resistant to scrapie. The aim of this study was to evaluate the in vitro toxic effects of PrP(ARR) and PrP(ARQ) variants in relation with their structural characteristics. We show that both peptides cause cell death inducing apoptosis but, unexpectedly, the scrapie resistant PrP(ARR) form was more toxic than the scrapie susceptible PrP(ARQ) variant. Moreover, the alpha-helical conformation of PrP(ARR) was less stable than that of PrP(ARQ) and the structural determinants responsible of these different conformational stabilities were characterized by spectroscopic analysis. We observed that PrP toxicity was inversely related to protein structural stability, being the unfolded conformation more toxic than the native one. However, the PrP(ARQ) variant displays a higher propensity to form large aggregates than PrP(ARR). Interestingly, in the presence of small amounts of PrP(ARR), PrP(ARQ) aggregability was reduced to levels similar to that of PrP(ARR). Thus, in contrast to PrP(ARR) toxicity, scrapie transmissibility seems to reside in the more stable conformation of PrP(ARQ) that allows the formation of large amyloid fibrils.
authors.affiliation: Department of Scienze degli Alimenti, Veterinary School, University of Teramo, Teramo, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Paludi
authors.forename: Stefano
authors.initials: S
authors.lastname: Thellung
authors.forename: Katia
authors.initials: K
authors.lastname: Chiovitti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Corsaro
authors.forename: Valentina
authors.initials: V
authors.lastname: Villa
authors.forename: Claudio
authors.initials: C
authors.lastname: Russo
authors.forename: Adriana
authors.initials: A
authors.lastname: Ianieri
authors.forename: Uwe
authors.initials: U
authors.lastname: Bertsch
authors.forename: Hans A
authors.initials: HA
authors.lastname: Kretzschmar
authors.forename: Antonio
authors.initials: A
authors.lastname: Aceto
authors.forename: Tullio
authors.initials: T
authors.lastname: Florio
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000378:metabolism / Q000503:physiopathology; D020022:Genetic Predisposition to Disease; D006801:Humans; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000633:toxicity*; D011328:Prions / Q000737:chemistry* / Q000633:toxicity*; D020033:Protein Isoforms / Q000737:chemistry / Q000633:toxicity; D017433:Protein Structure, Secondary / Q000502:physiology; D012608:Scrapie / Q000378:metabolism* / Q000503:physiopathology; D034561:Sheep, Domestic; D013057:Spectrum Analysis
chemical_list: D000682:Amyloid; D010455:Peptides; D011328:Prions; D020033:Protein Isoforms