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Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P206
STRUCTURAL INVESTIGATIONS OF PRION PROTEIN AGGREGA-
TION
Lars Redecke 1 , Marko Silvestric 1 , Joachim Clos 2 , Perter V. Konarev 3 ,
Dimitri S. Svergun 3 , Wolfram Meyer-Klaucke 3 , Dessislava Georgieva 1 ,
Nicolay Genov 4 , Christian Betzel 1
1 Universität Hamburg, Institut für Biochemie und Lebensmittelchemie, Martin-
Luther-King Platz 6, 20146 Hamburg, Germany – 2 Bernhard-Nocht-Institut für
Tropenmedizin, Bernhard-Nocht Str. 74, 20359 Hamburg, Germany – 3 European
Molecular Biology Laboratory, Outstation Hamburg, Notkestr. 85, 22607 Hamburg,
Germany – 4 Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia
1113, Bulgaria
Prion proteins are involved in a group of fatal neurodegenerative diseases including
bovine spongiform encephalopathy (BSE) in cattle and Creutzfeld-Jakob disease (CJD)
in humans. The posttranslational conversion of the prion protein from its normal cellular
isoform (PrPC) into its misfolded infectious state (PrPSc), which accumulates in
the central nervous system, is considered to act as a key event during the course of
disease. However, the physiological functions of the cellular prion protein as well as
the pathogenesis of neuronal cell death in prion diseases remain still enigmatic. Consequently,
the detailed structural investigation of the conversion and aggregation process
is required to elucidate the pathogenesis of prion diseases and to develop promising
therapies. Since increased levels of oxidative stress have been linked to prion diseases,
we investigated the metal-induced oxidation of human PrP (90-231) as well as of mouse
PrP (89-230). A novel in vitro conversion assay based on aerobic incubation of PrP in
the presence of elemental, redox-active metal pellets at pH 5 was established, resulting
in aggregation of highly β-sheeted prion proteins. We show for the first time that
discrete oligomeric species of elongated shape, approx. 25mers, 80mers, and 100mers,
are formed on the pathway of oxidative PrP aggregation, which are well characterized
regarding shape and size using small-angle X-ray scattering (SAXS) techniques.
Considering that small oligomers of highly similar size have recently been reported
to show the highest specific infectivity within TSE-infected brain tissues of hamsters,
the novel oligomers observed in this study are interesting candidates as agent causing
neurodegenerative and/or self-propagating effects. Moreover, extended X-ray absorption
fine structure (EXAFS) measurements revealed that the generated high molecular
mass aggregates coordinate Cu(II) and Zn(II) ions in a specific geometry, which indicates
a structural influence of the metal ions during aggregate formation. Specific
copper binding sites have been observed several fold within the N-terminal part of prion
proteins. However, mammalian and avian prion proteins, which are not able to undergo
the conversion process into an infectious isoform, have a considerably different
N-terminal copper coordination, as it is additionally shown by comparative EXAFS
analysis. These results provide new insights into the prion protein structure-function
relationship and into the conversion process of PrP.