Autocatalytic self-propagation of misfolded prion protein

doi:10.1073/pnas.0404650101

Autocatalytic self-propagation of misfolded prion protein

^*Center for Neuropathology and Prion Research, Ludwig Maximilians University of Munich, Feodor-Lynen-Strasse 23, 81377 Munich, Germany; and ^‡Robert Koch Institute, Nordufer 20, 13353 Berlin, Germany

Communicated by Manfred Eigen, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany, June 30, 2004 (received for review March 1, 2004)

Abstract

Prions are thought to replicate in an autocatalytic process that converts cellular prion protein (PrP^C) to the disease-associated misfolded PrP isoform (PrP^Sc). Our study scrutinizes this hypothesis by in vitro protein misfolding cyclic amplification (PMCA). In serial transmission PMCA experiments, PrP^Sc was inoculated into healthy hamster brain homogenate containing PrP^C. Misfolded PrP was amplified by rounds of sonication and incubation and reinoculated into fresh brain homogenate every 10 PMCA rounds. The amplification depended on PrP^C substrate and could be inhibited by recombinant hamster PrP. In serial dilution experiments, newly formed misfolded and proteinase K-resistant PrP (PrPres) catalyzed the structural conversion of PrP^C as efficiently as PrP^Sc from brain of scrapie (263K)-infected hamsters, yielding an ≈300-fold total amplification of PrPres after 100 rounds, which confirms an autocatalytic PrP-misfolding cascade as postulated by the prion hypothesis. PrPres formation was not paralleled by replication of biological infectivity, which appears to require factors additional to PrP-misfolding autocatalysis.

Footnotes

↵ † To whom correspondence should be sent at the present address: The Scripps Research Institute, BCC 265, 10550 North Torrey Pines Road, La Jolla, CA 92037. E-mail: jbiesch{at}scripps.edu.
Abbreviations: PMCA, protein misfolding cyclic amplification; PrP, prion protein; Prp^C, cellular PrP; PrP^Sc, scrapie-associated PrP isoform; PrPres, proteinase K-resistant PrP; LD_50i.c., 50% intracerebral lethal dose; rPrP, recombinant PrP; SHa, Syrian hamster.