The Structural Architecture of an Infectious Mammalian Prion Using Electron Cryomicroscopy

PLoS Pathog. 2016 Sep 8;12(9):e1005835. doi: 10.1371/journal.ppat.1005835. eCollection 2016 Sep.

Abstract

The structure of the infectious prion protein (PrPSc), which is responsible for Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy, has escaped all attempts at elucidation due to its insolubility and propensity to aggregate. PrPSc replicates by converting the non-infectious, cellular prion protein (PrPC) into the misfolded, infectious conformer through an unknown mechanism. PrPSc and its N-terminally truncated variant, PrP 27-30, aggregate into amorphous aggregates, 2D crystals, and amyloid fibrils. The structure of these infectious conformers is essential to understanding prion replication and the development of structure-based therapeutic interventions. Here we used the repetitive organization inherent to GPI-anchorless PrP 27-30 amyloid fibrils to analyze their structure via electron cryomicroscopy. Fourier-transform analyses of averaged fibril segments indicate a repeating unit of 19.1 Å. 3D reconstructions of these fibrils revealed two distinct protofilaments, and, together with a molecular volume of 18,990 Å3, predicted the height of each PrP 27-30 molecule as ~17.7 Å. Together, the data indicate a four-rung β-solenoid structure as a key feature for the architecture of infectious mammalian prions. Furthermore, they allow to formulate a molecular mechanism for the replication of prions. Knowledge of the prion structure will provide important insights into the self-propagation mechanisms of protein misfolding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid / genetics
  • Amyloid / ultrastructure*
  • Animals
  • Cattle
  • Creutzfeldt-Jakob Syndrome / genetics
  • Creutzfeldt-Jakob Syndrome / metabolism
  • Creutzfeldt-Jakob Syndrome / pathology
  • Cryoelectron Microscopy
  • Encephalopathy, Bovine Spongiform / genetics
  • Encephalopathy, Bovine Spongiform / metabolism
  • Encephalopathy, Bovine Spongiform / pathology
  • Humans
  • PrPC Proteins / genetics
  • PrPC Proteins / ultrastructure*
  • PrPSc Proteins / genetics
  • PrPSc Proteins / ultrastructure*

Substances

  • Amyloid
  • PrPC Proteins
  • PrPSc Proteins

Associated data

  • figshare/10.6084/m9.figshare.c.3292481

Grant support

This project has been supported by grants from the Alberta Prion Research Institute / Alberta Innovates Bio Solutions (201100010; 201100011; 201300012; 201300024), the Alberta Livestock & Meat Agency (2012A001R), the Canada Foundation for Innovation (NIF 21633 and IOF 21633 awards to D. Westaway), the European Commission grant FP7 222887 "Priority", a Spanish Ministry of Education grant (BFU2006-04588/BMC), and Spanish Ministry of Economy and Competitiveness grants (BFU2013-48436-C2-1-P & TIN2012-37483-C03-02). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.