Role Of Macromolecular Crowding In Prion Protein Structure Conversion And Oligomerization

Prions are unprecedented infectious pathogens that cause a group of invariably fatal neurodegenerative diseases. Prion diseases include Kuru, Gerstmann-Str□ussler-Scheinker disease (GSS), fatal familial insomnia (FFI), Creutzfeldt-Jakob disease (CJD), and variant Creutzfeldt-Jakob disease (vCJD) in human; bovine spongiform encephalopathy (BSE) in cattle; scrapie in sheep. Prion diseases may cause the genetic, infectious, or sporadic disorders, and all of these diseases involve the modified prion protein (PrP). Prions are transmissible particles that composed of the modified protein (PrPSc), and prions are devoid of nucleic acid. The conversion of normal PrP (PrPc) into PrPSc is through a posttranslational process during which it acquires highβ-sheet content. Although a common feature of the prion disease is the accumulation of amyloid fibrils, it is widely accepted that the soluble oligomers ofβ-PrP are neurotoxic and that they have more pathologically significant. To unravel the molecular mechanism under the conversion process, it is critical to identify the factors that can promote the conversion from PrC to theβ-oligomers.The concentration of macromolecules in the cytoplasm is estimated to be in the range of 80-400g/L, and all the macromolecules collectively occupy-10-40%of total fluid volume. Such a condition is referred as macromolecular crowding. The same as the other proteins, the reaction of the prion protein is also in the macromolecular crowding. But we don't know how such condition could affect the prion protein. By recording circular dichroism spectra and performing a size-exclusion HPLC assay, we found that the conformation of the recombinant human prion protein (rPrPc) was converted from a-helical conformation intoβ-sheet oligomers under the macromolecular crowding condition. The solubleβ-oligomers of rPrP were resistant to proteinase K digestion and could bind to the dyes ThT and ANS. Furthermore, by the MTS assay, we showed that the soluble P-oligomers were neurotoxic. These results suggest that macromolecular crowding, which has not been considered before, is a key intracellular factor in the formation of soluble neurotoxic P-oligomers in prion diseases.Our research suggests that macromolecular crowding, which has not been considered before, is a key intracellular factor in the formation of soluble neurotoxic P-oligomers in prion diseases. These results also could advance our understanding about the pathogenesis of other PCD diseases such as Parkinson's diseases, Alzheimer's, Huntington's diseases and other diseases that resulted from accumulation of misfolding protein.