Bryological and Lichenological Section/ABLS
Bennett, James P. , Johnson, C. J. , Biro, S. M. , Duque-Velasquez, C. , Bessen, R. A. , Rocke, T. E. .
Pathogenic Prion Protein is Degraded by a Serine Protease in Certain Lichens.
Background: Lichens are unusual, symbiotic organisms formed from a fungus and partner algae or cyanobacteria. The geographic distribution of lichens is extraordinarily wide and many species thrive in extreme environments such as arctic tundra, desert rock, pure sand or toxic slag heaps. Few biological systems have been identified that degrade the pathogenic form of the prion protein (PrPTSE) and the remarkable biology of lichens and their need to capture and conserve nutrients in harsh conditions suggests that lichens may be capable of unique metabolic activities. Objectives: We tested the hypothesis that lichens have the potential to degrade PrPTSE. Methods: We used extracts from three lichens, as well as freshly-collected live lichens, to assess PrPTSE degradation as measured by immunoblotting or protein misfolding cyclic amplification. Results: We found that extracts of the three lichen species caused approximately a 100-fold loss of prion protein immunoreactivity in samples containing PrPTSE from hamsters or white-tailed deer. Intact lichens exposed to infected brain homogenate reduced PrPTSE levels approximately 70% following 24h incubation. Some common lichen chemicals were excluded from being the active substance(s) and treatments to interfere with redox reactions or metalloenzymes were not effective at blocking degradation. Two protease inhibitor cocktails, however, were each partially effective at preventing lichen extract-induced PrPTSE degradation. Screening a panel of individual, specific protease inhibitors revealed that a serine protease of lichens is the likely agent that degrades prion protein. Discussion: While animal bioassay experiments to determine the effect of lichen extracts on infectious titer are ongoing, these data suggest that lichens could promote prion degradation in the environment and may have utility for prion inactivation in medical or biotechnological settings. Additionally, the role of lichens in prion environmental biology should be investigated.
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1 - University of Wisconsin, Institute for Environmental Studies, 445 Henry Mall, Madison, Wisconsin, 53706, USA
Presentation Type: Poster:Posters for Sections
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM