Specific binding of normal prion protein to the scrapie form via a localized domain initiates its conversion to the protease-resistant state.
In the transmissible spongiform encephalopathies, normal prion protein (PrP-sen) is converted to a protease-resistant isoform, PrP-res, by an apparent self-propagating activity of the latter. Here we describe new, more physiological cell-free systems for analyzing the initial binding and subsequent conversion reactions between PrP-sen and PrP-res. These systems allowed the use of antibodies to map the sites of interaction between PrP-sen and PrP-res. Binding of antibodies (alpha219-232) to hamster PrP-sen residues 219-232 inhibited the binding of PrP-sen to PrP-res and the subsequent generation of PK-resistant PrP. However, antibodies to several other parts of PrP-sen did not inhibit. The alpha219-232 epitope itself was not required for PrP-res binding; thus, inhibition by alpha219-232 was likely due to steric blocking of a binding site that is close to, but does not include the epitope in the folded PrP-sen structure. The selectivity of the binding reaction was tested by incubating PrP-res with cell lysates or culture supernatants. Only PrP-sen was observed to bind PrP-res. This highly selective binding to PrP-res and the localized nature of the binding site on PrP-sen support the idea that PrP-sen serves as a critical ligand and/or receptor for PrP-res in the course of PrP-res propagation and pathogenesis in vivo.
Horiuchi
M
M
Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, NIH, 903 S 4th Street, Hamilton, MT 59840, USA.
Caughey
B
B
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001665:Binding Sites; D001921:Brain; D002268:Carboxypeptidases / Q000378:metabolism; D006224:Cricetinae; D019286:Endopeptidase K / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism*; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D006031:Glycosylation; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D051379:Mice; D008958:Models, Molecular; D008970:Molecular Weight; D011189:Potassium Chloride / Q000494:pharmacology; D018621:PrPC Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018620:PrPSc Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017384:Sequence Deletion; D012965:Sodium Chloride / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000939:Epitopes; D007140:Immunoglobulin Fab Fragments; D018621:PrPC Proteins; D018620:PrPSc Proteins; D020033:Protein Isoforms; D012965:Sodium Chloride; D011189:Potassium Chloride; D002268:Carboxypeptidases; D010450:Endopeptidases; D019286:Endopeptidase K