Ligand binding promotes prion protein aggregation - Role of the octapeptide repeats

Department of Pathology, Case Western Reserve University, Cleveland, OH 44106-7288, USA.
FEBS Journal (Impact Factor: 4). 12/2008; 275(22):5564-75. DOI: 10.1111/j.1742-4658.2008.06680.x
Source: PubMed


Aggregation of the normal cellular prion protein, PrP, is important in the pathogenesis of prion disease. PrP binds glycosaminoglycan (GAG) and divalent cations, such as Cu(2+) and Zn(2+). Here, we report our findings that GAG and Cu(2+) promote the aggregation of recombinant human PrP (rPrP). The normal cellular prion protein has five octapeptide repeats. In the presence of either GAG or Cu(2+), mutant rPrPs with eight or ten octapeptide repeats are more aggregation prone, exhibit faster kinetics and form larger aggregates than wild-type PrP. When the GAG-binding motif, KKRPK, is deleted the effect of GAG but not that of Cu(2+) is abolished. By contrast, when the Cu(2+)-binding motif, the octapeptide-repeat region, is deleted, neither GAG nor Cu(2+) is able to promote aggregation. Therefore, the octapeptide-repeat region is critical in the aggregation of rPrP, irrespective of the promoting ligand. Furthermore, aggregation of rPrP in the presence of GAG is blocked with anti-PrP mAbs, whereas none of the tested anti-PrP mAbs block Cu(2+)-promoted aggregation. However, a mAb that is specific for an epitope at the N-terminus enhances aggregation in the presence of either GAG or Cu(2+). Therefore, although binding of either GAG or Cu(2+) promotes the aggregation of rPrP, their aggregation processes are different, suggesting multiple pathways of rPrP aggregation.

Download full-text


Available from: Robert B Petersen
  • Source
    • "Indeed, Cu was found to induce expression of cellular PrP in primary cell cultures, upregulating the expression of this protein both at the cell surface as well as within intracellular compartments [116]. Cu promotes the aggregation of human PrP [117]. These findings stimulated the investigations on metal ion alteration in PrD human brains. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Metallothioneins (MT) are a family of proteins actively involved in metal detoxification and storage as well as in prevention of free-radical damage. Changes in the levels of MT have been described in a number of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, prion protein disease, Binswanger type of subcortical vascular dementia, and amyotrophic lateral sclerosis. This suggests that MT functions might be more complex and vast than what was initially thought. In this review, we summarize the current knowledge on the potential involvement of MT in the mentioned neurodegenerative diseases while also discussing the emerging evidence proposing MT modulation as a feasible therapeutic approach. Enhancing repair mechanisms after neurological damage and/or protection against oxidative stress through a proper modulation of this family of protein might indeed represent an important avenue to cope neurodegeneration.
    Full-text · Article · Feb 2014 · Journal of Alzheimer's disease: JAD
  • Source
    • "the sulfated GAGs (mainly heparan sulfate (HS) and chondroitin sulfate (CS)) are stabilizing molecules for the PrP C conformation [8] as their negative charges interact with positively charged residues of the prion protein [9] [10] [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The conversion of the endogenous cellular prion protein to an abnormally folded isoform is a hallmark of transmissible spongiform encephalopathies. It occurs when a misfolded prion protein contacts the cellular PrP. Among the molecular partners suggested to be involved in the misfolding process, the glycosaminoglycans seem to be good candidates. The present study was aimed to examine a possible link between PrP conversion efficiency and transcript level of Chst8 gene that encodes the carbohydrate N-acetylgalactosamine 4-O-sulfotransferase 8. Mov cells expressing ovine PrP were transfected with shRNA directed against Chst8 transcripts. Resulting clones were characterized for their Chst8 and Prnp transcript levels, and for their content in sulfated glycosaminoglycans, more particularly sulfated chondroitins. Unexpectedly, the decreased amount of Chst8 transcript induced an increase of the chondroitin sulfate percentage among total GAGs, with an increased amount of 4-O-sulfation of GalNAc residues. Upon to infection by a sheep prion, a slight amount of PrP(Sc) was observed, which rapidly disappeared upon subpassaging. Together, these findings indicate that the Chst8 transcript level affects the glycosaminoglycan environment of the cellular prion protein, and as a consequence its ability for conversion into PrP(Sc).
    Full-text · Article · Oct 2011 · Biochemical and Biophysical Research Communications
  • Source
    • "ion per repeat (Viles et al. 2008; Guerrieri et al. 2009), but there is still no generally accepted role for the binding of copper to PrP (Davies and Brown 2008). The repeat region modulates prion replication and pathogenicity (Flechsig et al. 2000), is involved in the protective effect against oxidative stress (Mitteregger et al. 2007; Malaise et al. 2008), and in PrP aggregation upon copper binding (Yu et al. 2008). Mammals homozygous for four or seven repeats also occur (van Rheede et al. 2003; Kim et al. 2008; Rongyan et al. 2008; Martin et al. 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The N-terminal region of the mammalian prion protein (PrP) contains an ‘octapeptide’ repeat which is involved in copper binding. This eight- or nine-residue peptide is repeated four to seven times, depending on the species, and polymorphisms in repeat number do occur. Alleles with three repeats are very rare in humans and goats, and deduced PrP sequences with two repeats have only been reported in two lemur species and in the red squirrel, Sciurus vulgaris. We here describe that the red squirrel two-repeat PrP sequence actually represents a retroposed pseudogene, and that an additional and older processed pseudogene with three repeats also occurs in this species as well as in ground squirrels. We argue that repeat numbers may tend to contract rather than expand in prion retropseudogenes, and that functional prion genes with two repeats may not be viable. Electronic supplementary material The online version of this article (doi:10.1007/s00239-010-9390-7) contains supplementary material, which is available to authorized users.
    Preview · Article · Sep 2010 · Journal of Molecular Evolution
Show more