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Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions.

ABSTRACT: Prions are unconventional infectious agents that cause transmissible spongiform encephalopathy (TSE) diseases, or prion diseases. The biochemical nature of the prion infectious agent remains unclear. Previously, using a protein misfolding cyclic amplification (PMCA) reaction, infectivity and disease-associated protease-resistant prion protein (PrPres) were both generated under cell-free conditions, which supported a nonviral hypothesis for the agent. However, these studies lacked comparative quantitation of both infectivity titers and PrPres, which is important both for biological comparison with in vivo-derived infectivity and for excluding contamination to explain the results. Here during four to eight rounds of PMCA, end-point dilution titrations detected a >320-fold increase in infectivity versus that in controls. These results provide strong support for the hypothesis that the agent of prion infectivity is not a virus. PMCA-generated samples caused the same clinical disease and neuropathology with the same rapid incubation period as the input brain-derived scrapie samples, providing no evidence for generation of a new strain in PMCA. However, the ratio of the infectivity titer to the amount of PrPres (specific infectivity) was much lower in PMCA versus brain-derived samples, suggesting the possibility that a substantial portion of PrPres generated in PMCA might be noninfectious.

SUBMITTER: Klingeborn M

PROVIDER: S-EPMC3228482 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions.

Klingeborn Mikael M Race Brent B Meade-White Kimberly D KD Chesebro Bruce B

Proceedings of the National Academy of Sciences of the United States of America 20111107 48

Prions are unconventional infectious agents that cause transmissible spongiform encephalopathy (TSE) diseases, or prion diseases. The biochemical nature of the prion infectious agent remains unclear. Previously, using a protein misfolding cyclic amplification (PMCA) reaction, infectivity and disease-associated protease-resistant prion protein (PrPres) were both generated under cell-free conditions, which supported a nonviral hypothesis for the agent. However, these studies lacked comparative qua ...[more]

PMID: 22065744

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Project description:Although misfolding of normal prion protein (PrPC) into abnormal conformers (PrPSc) is critical for prion disease pathogenesis our current understanding of the underlying molecular pathophysiology is rudimentary. Exploiting an electrophysiology paradigm, herein we report that at least modestly proteinase K (PK)-resistant PrPSc (PrPres) species are acutely synaptotoxic. Brief exposure to ex vivo PrPSc from two mouse-adapted prion strains (M1000 and MU02) prepared as crude brain homogenates (cM1000 and cMU02) and cell lysates from chronically M1000-infected RK13 cells (MoRK13-Inf) caused significant impairment of hippocampal CA1 region long-term potentiation (LTP), with the LTP disruption approximating that reported during the evolution of murine prion disease. Proof of PrPSc (especially PrPres) species as the synaptotoxic agent was demonstrated by: significant rescue of LTP following selective immuno-depletion of total PrP from cM1000 (dM1000); modestly PK-treated cM1000 (PK+M1000) retaining full synaptotoxicity; and restoration of the LTP impairment when employing reconstituted, PK-eluted, immuno-precipitated M1000 preparations (PK+IP-M1000). Additional detailed electrophysiological analyses exemplified by impairment of post-tetanic potentiation (PTP) suggest possible heightened pre-synaptic vulnerability to the acute synaptotoxicity. This dysfunction correlated with cumulative insufficiency of replenishment of the readily releasable pool (RRP) of vesicles during repeated high-frequency stimulation utilised for induction of LTP. Broadly comparable results with LTP and PTP impairment were obtained utilizing hippocampal slices from PrPC knockout (PrPo/o) mice, with cM1000 serial dilution assessments revealing similar sensitivity of PrPo/o and wild type (WT) slices. Size fractionation chromatography demonstrated that synaptotoxic PrP correlated with PK-resistant species >100kDa, consistent with multimeric PrPSc, with levels of these species >6 ng/ml appearing sufficient to induce synaptic dysfunction. Biochemical analyses of hippocampal slices manifesting acute synaptotoxicity demonstrated reduced levels of multiple key synaptic proteins, albeit with noteworthy differences in PrPo/o slices, while such changes were absent in hippocampi demonstrating rescued LTP through treatment with dM1000. Our findings offer important new mechanistic insights into the synaptic impairment underlying prion disease, enhancing prospects for development of targeted effective therapies.

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Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions.

Publications

Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions.

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