title: Dissociation of recombinant prion protein fibrils into short protofilaments: implications for the endocytic pathway and involvement of the N-terminal domain.
abstract: Fibril dissociation is necessary for efficient conversion of normal prion protein to its misfolded state and continued propagation into amyloid. Recent studies have revealed that conversion occurs along the endocytic pathway. To improve our understanding of the dissociation process, we have investigated the effect of low pH on the stability of recombinant prion fibrils. We show that under conditions that mimic the endocytic environment, amyloid fibrils made from full-length prion protein dissociate both laterally and axially to form protofilaments. Approximately 5% of the protofilaments are short enough to be considered soluble and contain ~100-300 monomers per structure; these also retain the biophysical characteristics of the filaments. We propose that protonation of His residues and charge repulsion in the N-terminal domain trigger fibril dissociation. Our data suggest that lysosomes and late endosomes are competent milieus for propagating the misfolded state not only by destabilizing the normal prion protein but also by accelerating the dissociation of fibrils into smaller structures that may act as seeds.
authors.affiliation: Center for Biomolecular Structure and Dynamics and Division of Biological Sciences, 204 CHCB, The University of Montana, Missoula, Montana 59812, United States.
authors.forename: Xu
authors.initials: X
authors.lastname: Qi
authors.forename: Roger A
authors.initials: RA
authors.lastname: Moore
authors.forename: Michele A
authors.initials: MA
authors.lastname: McGuirl
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002942:Circular Dichroism; D006224:Cricetinae; D004705:Endocytosis; D006863:Hydrogen-Ion Concentration; D008647:Mesocricetus; D011328:Prions / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000682:Amyloid; D011328:Prions; D011994:Recombinant Proteins