title: Ligand binding promotes prion protein aggregation--role of the octapeptide repeats.
abstract: 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.
authors.affiliation: Department of Pathology, Case Western Reserve University, Cleveland, OH 44106-7288, USA.
authors.forename: Shuiliang
authors.initials: S
authors.lastname: Yu
authors.forename: Shaoman
authors.initials: S
authors.lastname: Yin
authors.forename: Nancy
authors.initials: N
authors.lastname: Pham
authors.forename: Poki
authors.initials: P
authors.lastname: Wong
authors.forename: Shin-Chung
authors.initials: SC
authors.lastname: Kang
authors.forename: Robert B
authors.initials: RB
authors.lastname: Petersen
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Li
authors.forename: Man-Sun
authors.initials: MS
authors.lastname: Sy
mesh_terms: D020816:Amino Acid Motifs; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001665:Binding Sites; D002413:Cations, Divalent; D003300:Copper / Q000378:metabolism*; D000939:Epitopes; D006025:Glycosaminoglycans / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008024:Ligands; D009842:Oligopeptides / Q000378:metabolism; D011328:Prions / Q000378:metabolism*; D011485:Protein Binding; D020449:Repetitive Sequences, Amino Acid
chemical_list: D000911:Antibodies, Monoclonal; D002413:Cations, Divalent; D000939:Epitopes; D006025:Glycosaminoglycans; D008024:Ligands; D009842:Oligopeptides; D011328:Prions; D003300:Copper