Florey Department of Neuroscience and Mental Health - Research Publications

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Author: Masters, Colin × Author: COLEMAN, BRADLEY ×

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    Conservation of a Glycine-rich Region in the Prion Protein Is Required for Uptake of Prion Infectivity
    Harrison, CF ; Lawson, VA ; Coleman, BM ; Kim, Y-S ; Masters, CL ; Cappai, R ; Barnham, KJ ; Hill, AF (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2010-06-25)
    Prion diseases are associated with the misfolding of the endogenously expressed prion protein (designated PrP(C)) into an abnormal isoform (PrP(Sc)) that has infectious properties. The hydrophobic domain of PrP(C) is highly conserved and contains a series of glycine residues that show perfect conservation among all species, strongly suggesting it has functional and evolutionary significance. These glycine residues appear to form repeats of the GXXXG protein-protein interaction motif (two glycines separated by any three residues); the retention of these residues is significant and presumably relates to the functionality of PrP(C). Mutagenesis studies demonstrate that minor alterations to this highly conserved region of PrP(C) drastically affect the ability of cells to uptake and replicate prion infection in both cell and animal bioassay. The localization and processing of mutant PrP(C) are not affected, although in vitro and in vivo studies demonstrate that this region is not essential for interaction with PrP(Sc), suggesting these residues provide conformational flexibility. These data suggest that this region of PrP(C) is critical in the misfolding process and could serve as a novel, species-independent target for prion disease therapeutics.
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    Pathogenic Mutations within the Hydrophobic Domain of the Prion Protein Lead to the Formation of Protease-Sensitive Prion Species with Increased Lethality
    Coleman, BM ; HARRISON, C ; GUO, B ; Masters, CL ; Barnham, KJ ; Lawson, VA ; Hill, AF ( 2014)
    Prion diseases are a group of fatal and incurable neurodegenerative diseases affecting both humans and animals. The principal mechanism of these diseases involves the misfolding the host-encoded cellular prion protein, PrPC, into the disease-associated isoform, PrPSc. Familial forms of human prion disease include those associated with the mutations G114V and A117V, which lie in the hydrophobic domain of PrP. Here we have studied the murine homologues (G113V and A116V) of these mutations using cell-based and animal models of prion infection. Under normal circumstances, the mutant forms of PrPC share similar processing, cellular localization, and physicochemical properties with wild-type mouse PrP (MoPrP). However, upon exposure of susceptible cell lines expressing these mutants to infectious prions, very low levels of protease-resistant aggregated PrPSc are formed. Subsequent mouse bioassay revealed high levels of infectivity present in these cells. Thus, these mutations appear to limit the formation of aggregated PrPSc, giving rise to the accumulation of a relatively soluble, protease sensitive, prion species that is highly neurotoxic. Given that these mutations lie next to the glycine-rich region of PrP that can abrogate prion infection, these findings provide further support for small, protease-sensitive prion species having a significant role in the progression of prion disease and that the hydrophobic domain is an important determinant of PrP conversion.IMPORTANCEPrion diseases are transmissible neurodegenerative diseases associated with an infectious agent called a prion. Prions are comprised of an abnormally folded form of the prion protein (PrP) that is normally resistant to enzymes called proteases. In humans, prion disease can occur in individuals who inherited mutations in the prion protein gene. Here we have studied the effects of two of these mutations and show that they influence the properties of the prions that can be formed. We show that the mutants make highly infectious prions that are more sensitive to protease treatment. This study highlights a certain region of the prion protein as being involved in this effect and demonstrates that prions are not always resistant to protease treatment.