Heterogeneity of truncated fragments distinct from PrP27-30 correlates with clinico-pathological subtypes of Creutzfeldt-Jakob disease

Heterogeneity of truncated fragments distinct from PrP27-30 correlates with clinico-pathological subtypes of Creutzfeldt-Jakob disease S Notari1, S Capellari1, A Giese2, J Grassi3, B Ghetti4, P Gambetti5, HA Kretzschmar2, P Parchi1 1 Dipartimento di Scienze Neurologiche, Università di Bologna, Italy; 2 Institut fuer Neuropatologie, LMU Muenchen, Germany; 3 Service de Pharmacologie et d´Immunologie, CEA/Saclay, France; 4 Institute of Pathology, Indiana University, Indianapolis, IN, USA; 5 Institute of Pathology, CWRU, Cleveland, OH, USA It is increasingly recognized that there are additional TSE associated PrPSc fragments beside fulllength PrPSc and its N-terminally truncated, protease-resistant core PrP27-30. For example, two novel C-terminal fragments (CTF) of PrPSc with a relative molecular mass of about 12 and 13 kDa, were recently described in sporadic CJD (sCJD). To better characterize these as well as novel putative PrP abnormal fragments, we analysed PrPSc extracted from the frontal cortex by means of western blotting and a panel of antibodies against various PrP epitopes. We studied 50 CJD cases, representing all disease subtypes described to date. Selectively enriched samples showed the presence of previously undescribed PrPSc fragments. PrP27-30 type 1 samples showed an associated 18,5 kDa band, whereas the type 2 samples displayed a 17 kDa band. Analyses of molecular mass combined with epitope mapping suggested that the 2 fragments share the primary N- terminal sequence with types 1 and 2 respectively but lack a few amino acids at the very end of C-terminus together with the GPI anchor. The amount of the 18,5 or 17 fragments significantly differed among CJD subtypes. Similarly, we disclosed previously unreported difference in the amount of 12/13 kDa CTF fragments among CJD subtypes. These included the lack of both fragments in vCJD and of the 13 kDa peptide in sCJDVV2. Finally, we found that in sCJDMM1, in contrast to other CJD subtypes, protease digestion of PrPSc in partially denaturing conditions generates a significant amount of an additional truncated fragment of about 16 kDa. These results show that the physico-chemical heterogeneity of CJD associated PrP27-30 extends to abnormal truncated form of the protein. Furthermore, our finding support the notion of the existence of distinct “structural conformers” of PrPSc and indicate that the characterization of truncated PrPSc forms may further improve molecular typing in CJD. Supported by EU contract QLK3-CT-2001-02345.