Segments in the Amyloid Core that Distinguish Hamster from Mouse Prion Fibrils
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Prion diseases are transmissible fatal neurodegenerative disorders affecting humans and other mammals. The disease transmission can occur between different species but is limited by the sequence homology between host and inoculum. The crucial molecular event in the progression of this disease is prion formation, starting from the conformational conversion of the normal, membrane-anchored prion protein (PrPC) into the misfolded, β-sheet-rich and aggregation-prone isoform (PrPSc), which then self-associates into the infectious amyloid form called prion. Amyloid is the aggregate formed from one-dimensional protein association. As amyloid formation is a key hallmark in prion pathogenesis, studying which segments in prion protein are involved in the amyloid formation can provide molecular details in the cross-species transmission barrier of prion diseases. However, due to the difficulties of studying protein aggregates, very limited knowledge about prion structure or prion formation was disclosed by now. In this study, cross-seeding assay was used to identify the segments involved in the amyloid fibril formation of full-length hamster prion protein, SHaPrP(23–231). Our results showed that the residues in the segments 108–127, 172–194 (helix 2 in PrPC) and 200–227 (helix 3 in PrPC) are in the amyloid core of hamster prion fibrils. The segment 127–143, but not 107–126 (which corresponds to hamster sequence 108–127), was previously reported to be involved in the amyloid core of full-length mouse prion fibrils. Our results indicate that hamster prion protein and mouse prion protein use different segments to form the amyloid core in amyloidogenesis. The sequence-dependent core formation can be used to explain the seeding barrier between mouse and hamster.
KeywordsPrion Amyloid Fibril Hamster Cross-β Seeding
The TEM images were obtained with the assistance of Mr. Tai-Lang Lin from the core facility of the Institute of Cellular and Organismic Biology, Academia Sinica. Mass spectra were acquired from three mass spectrometry facilities in Academia Sinica. Protein identification by ESI-TOF was conducted in the mass spectrometry facility of the Institute of Chemistry. Peptide identification by MALDI-TOF was conducted in the mass spectrometry facility of the Institute of Molecular Biology. The MS/MS study by LTQ Orbitrap was performed in the Academia Sinica Common Mass Spectrometry Facility for proteomics and protein modification analysis located at the Institute of Biological Chemistry, supported by Academia Sinica Core Facility and Innovative Instrument Project (AS-CFII-108-107). This work was funded by the Ministry of Science and Technology (MOST) of Taiwan (MOST 105-2119-M-001-028).
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Conflict of interest
The authors declare no conflict of interest.
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