Structures and Activities of Prions and Prion Proteins

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

Accumulation of fibrillar protein aggregates is a hallmark of many diseases. While numerous proteins form fibrils by prion-like seeded polymerization in vitro, only some are transmissible and pathogenic in vivo. To probe the structural features that confer transmissibility to prion protein (PrP) fibrils, we have analyzed synthetic PrP amyloids with or without the human prion disease-associated P102L mutation. The formation of infectious prions from PrP molecules in vitro has required cofactors and/or unphysiological denaturing conditions. We demonstrated that, under physiologically compatible conditions without cofactors, the P102L mutation in recombinant hamster PrP promoted prion formation when seeded by minute amounts of scrapie prions in vitro. Surprisingly, combination of the P102L mutation with charge-neutralizing substitutions of four nearby lysines promoted spontaneous prion formation. When inoculated into hamsters, both of these types of synthetic prions initiated substantial accumulation of prion seeding activity and protease-resistant PrP without TSE clinical signs or notable glial activation. Our results suggest that PrPs centrally located proline and lysine residues act as conformational switches in the in vitro formation of transmissible PrP amyloids. The fact that prions and other pathogenic protein aggregates such as amyloids are composed predominantly of tough, tightly packed proteins makes them unusually resistant to conventional microbial disinfection procedures. Infectious prions can persist indefinitely in, or on, a variety of materials such as tissues, fluids, tools, instruments, and environmental surfaces, making it important to identify decontaminants that are effective without being dangerous or damaging. We have shown that hypochlorous acid, a disinfectant that is produced naturally by certain cells within the body, has strong anti-prion and anti-amyloid activity. We found that a non-irritating and broadly applicable hypochlorous acid preparation can disinfect prions in tissue homogenates and on stainless steel wires serving as surrogates for surgical instruments. In other collaborative studies, we have applied our prion RT-QuIC assay to help other groups obtain evidence that: 1) the distribution of misfolded prion protein seeding activity alone does not predict regions of neurodegeneration; 2) smaller, soluble prions are more neuroinvasive than larger particles; 3) small conformational differences between synthetic PrP amyloids confer larger differences in their pathogenicity upon inoculation into rodents and 4) novel strain properties can distinguish human sporadic prion diseases sharing prion protein genotype and prion type.