title: Prion protein (PrP) synthetic peptides induce cellular PrP to acquire properties of the scrapie isoform.
abstract: Conversion of the cellular isoform of prion protein (PrPC) into the scrapie isoform (PrPSc) involves an increase in the beta-sheet content, diminished solubility, and resistance to proteolytic digestion. Transgenetic studies argue that PrPC and PrPSc form a complex during PrPSc formation; thus, synthetic PrP peptides, which mimic the conformational pluralism of PrP, were mixed with PrPC to determine whether its properties were altered. Peptides encompassing two alpha-helical domains of PrP when mixed with PrPC produced a complex that displayed many properties of PrPSc. The PrPC-peptide complex formed fibrous aggregates and up to 65% of complexed PrPC sedimented at 100,000 x g for 1 h, whereas PrPC alone did not. These complexes were resistant to proteolytic digestion and displayed a high beta-sheet content. Unexpectedly, the peptide in a beta-sheet conformation did not form the complex, whereas the random coil did. Addition of 2% Sarkosyl disrupted the complex and rendered PrPC sensitive to protease digestion. While the pathogenic A117V mutation increased the efficacy of complex formation, anti-PrP monoclonal antibody prevented interaction between PrPC and peptides. Our findings in concert with transgenetic investigations argue that PrPC interacts with PrPSc through a domain that contains the first two putative alpha-helices. Whether PrPC-peptide complexes possess prion infectivity as determined by bioassays remains to be established.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D019286:Endopeptidase K; D008647:Mesocricetus; D051379:Mice; D010446:Peptide Fragments / Q000737:chemistry; D011328:Prions / Q000737:chemistry*; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012608:Scrapie / Q000503:physiopathology*; D012697:Serine Endopeptidases / Q000378:metabolism; D012995:Solubility; D013045:Species Specificity; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D011328:Prions; D012697:Serine Endopeptidases; D019286:Endopeptidase K