Aggregation of prion protein with insertion mutations is proportional to the number of inserts.
Mutation in the prion gene, PRNP, accounts for approx. 10-15% of human prion diseases. However, little is known about the mechanisms by which a mutant prion protein (PrP) causes disease. We compared the biochemical properties of a wild-type human prion protein, rPrP(C) (recombinant wild-type PrP), which has five octapeptide-repeats, with two recombinant human prion proteins with insertion mutations, one with three more octapeptide repeats, rPrP(8OR), and the other with five more octapeptide repeats, rPrP(10OR). We found that the insertion mutant proteins are more prone to aggregate, and the degree and kinetics of aggregation are proportional to the number of inserts. The octapeptide-repeat and alpha-helix 1 regions are important in aggregate formation, because aggregation is inhibited with monoclonal antibodies that are specific for epitopes in these regions. We also showed that a small amount of mutant protein could enhance the formation of mixed aggregates that are composed of mutant protein and wild-type rPrP(C). Accordingly, rPrP(10OR) is also more efficient in promoting the aggregation of rPrP(C) than rPrP(8OR). These findings provide a biochemical explanation for the clinical observations that the severity of the disease in patients with insertion mutations is proportional to the number of inserts, and thus have implications for the pathogenesis of inherited human prion disease.
Yu
Shuiliang
S
Department of Pathology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44120, USA.
Yin
Shaoman
S
Li
Chaoyang
C
Wong
Poki
P
Chang
Binggong
B
Xiao
Fan
F
Kang
Shin-Chung
SC
Yan
Huimin
H
Xiao
Gengfu
G
Tien
Po
P
Sy
Man-Sun
MS
D000911:Antibodies, Monoclonal / Q000276:immunology; D006801:Humans; D016254:Mutagenesis, Insertional / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D011328:Prions / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D000911:Antibodies, Monoclonal; D011328:Prions; D011994:Recombinant Proteins