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Epigenetic dominance of prion conformers.

Saijo E, Kang HE, Bian J, Bowling KG, Browning S, Kim S, Hunter N, Telling GC - PLoS Pathog. (2013)

Bottom Line: Moreover, the resulting OvPrP-A136 prion acquired the characteristics of the U conformer.These results, substantiated by in vitro analyses, indicated that co-expression of OvPrP-V136 altered the conversion potential of OvPrP-A136 from the S to the otherwise unfavorable U conformer.This epigenetic mechanism thus expands the range of selectable conformations that can be adopted by PrP, and therefore the variety of options for strain propagation.

View Article: PubMed Central - PubMed

Affiliation: Prion Research Center (PRC) and Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America ; Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, Kentucky, United States of America.

ABSTRACT
Although they share certain biological properties with nucleic acid based infectious agents, prions, the causative agents of invariably fatal, transmissible neurodegenerative disorders such as bovine spongiform encephalopathy, sheep scrapie, and human Creutzfeldt Jakob disease, propagate by conformational templating of host encoded proteins. Once thought to be unique to these diseases, this mechanism is now recognized as a ubiquitous means of information transfer in biological systems, including other protein misfolding disorders such as those causing Alzheimer's and Parkinson's diseases. To address the poorly understood mechanism by which host prion protein (PrP) primary structures interact with distinct prion conformations to influence pathogenesis, we produced transgenic (Tg) mice expressing different sheep scrapie susceptibility alleles, varying only at a single amino acid at PrP residue 136. Tg mice expressing ovine PrP with alanine (A) at (OvPrP-A136) infected with SSBP/1 scrapie prions propagated a relatively stable (S) prion conformation, which accumulated as punctate aggregates in the brain, and produced prolonged incubation times. In contrast, Tg mice expressing OvPrP with valine (V) at 136 (OvPrP-V136) infected with the same prions developed disease rapidly, and the converted prion was comprised of an unstable (U), diffusely distributed conformer. Infected Tg mice co-expressing both alleles manifested properties consistent with the U conformer, suggesting a dominant effect resulting from exclusive conversion of OvPrP-V136 but not OvPrP-A136. Surprisingly, however, studies with monoclonal antibody (mAb) PRC5, which discriminates OvPrP-A136 from OvPrP-V136, revealed substantial conversion of OvPrP-A136. Moreover, the resulting OvPrP-A136 prion acquired the characteristics of the U conformer. These results, substantiated by in vitro analyses, indicated that co-expression of OvPrP-V136 altered the conversion potential of OvPrP-A136 from the S to the otherwise unfavorable U conformer. This epigenetic mechanism thus expands the range of selectable conformations that can be adopted by PrP, and therefore the variety of options for strain propagation.

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Characterization of transgenic mice expressing OvPrP-A136 and OvPrP-V136. A.Levels of transgene-expressed OvPrP in the CNS were estimated by semi-quantitative western blotting using mAb 6H4. Amounts of total protein loaded (µg) in each sample are shown. Prnp0/0, mice in which the PrP gene is disrupted; FVB, wild type mice. Estimates of expression levels, shown as a percentage (%) of that in FVB mice, are based on densitometric analysis of signals from diluted samples. B. Survival curves of mice following inoculation with sheep SSBP/1 scrapie prions. Percent (%) affected mice refers to numbers of mice within an inoculated cohort manifesting progressive clinical signs associated with prion disease. C. Western blot analysis of PK-treated brain extracts of diseased Tg(OvPrP-A136)3533+/− mice. SSBP/1 and CH1641 refer to mice inoculated with the respective prions. I and R refer to sheep SSBP/1 or CH1641 inocula, and brain extracts from recipient mice respectively.
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ppat-1003692-g001: Characterization of transgenic mice expressing OvPrP-A136 and OvPrP-V136. A.Levels of transgene-expressed OvPrP in the CNS were estimated by semi-quantitative western blotting using mAb 6H4. Amounts of total protein loaded (µg) in each sample are shown. Prnp0/0, mice in which the PrP gene is disrupted; FVB, wild type mice. Estimates of expression levels, shown as a percentage (%) of that in FVB mice, are based on densitometric analysis of signals from diluted samples. B. Survival curves of mice following inoculation with sheep SSBP/1 scrapie prions. Percent (%) affected mice refers to numbers of mice within an inoculated cohort manifesting progressive clinical signs associated with prion disease. C. Western blot analysis of PK-treated brain extracts of diseased Tg(OvPrP-A136)3533+/− mice. SSBP/1 and CH1641 refer to mice inoculated with the respective prions. I and R refer to sheep SSBP/1 or CH1641 inocula, and brain extracts from recipient mice respectively.

Mentions: We created Tg mice expressing OvPrP encoding either A or V at residue 136. Using semi-quantitative Western and immuno dot blotting we ascertained that levels of expression in the CNS of Tg(OvPrP-A136)3533+/− and Tg(OvPrP-V136)4166+/− mice were close to that of PrP expressed in the CNS of wild type mice (Fig. 1A).


Epigenetic dominance of prion conformers.

Saijo E, Kang HE, Bian J, Bowling KG, Browning S, Kim S, Hunter N, Telling GC - PLoS Pathog. (2013)

Characterization of transgenic mice expressing OvPrP-A136 and OvPrP-V136. A.Levels of transgene-expressed OvPrP in the CNS were estimated by semi-quantitative western blotting using mAb 6H4. Amounts of total protein loaded (µg) in each sample are shown. Prnp0/0, mice in which the PrP gene is disrupted; FVB, wild type mice. Estimates of expression levels, shown as a percentage (%) of that in FVB mice, are based on densitometric analysis of signals from diluted samples. B. Survival curves of mice following inoculation with sheep SSBP/1 scrapie prions. Percent (%) affected mice refers to numbers of mice within an inoculated cohort manifesting progressive clinical signs associated with prion disease. C. Western blot analysis of PK-treated brain extracts of diseased Tg(OvPrP-A136)3533+/− mice. SSBP/1 and CH1641 refer to mice inoculated with the respective prions. I and R refer to sheep SSBP/1 or CH1641 inocula, and brain extracts from recipient mice respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3814339&req=5

ppat-1003692-g001: Characterization of transgenic mice expressing OvPrP-A136 and OvPrP-V136. A.Levels of transgene-expressed OvPrP in the CNS were estimated by semi-quantitative western blotting using mAb 6H4. Amounts of total protein loaded (µg) in each sample are shown. Prnp0/0, mice in which the PrP gene is disrupted; FVB, wild type mice. Estimates of expression levels, shown as a percentage (%) of that in FVB mice, are based on densitometric analysis of signals from diluted samples. B. Survival curves of mice following inoculation with sheep SSBP/1 scrapie prions. Percent (%) affected mice refers to numbers of mice within an inoculated cohort manifesting progressive clinical signs associated with prion disease. C. Western blot analysis of PK-treated brain extracts of diseased Tg(OvPrP-A136)3533+/− mice. SSBP/1 and CH1641 refer to mice inoculated with the respective prions. I and R refer to sheep SSBP/1 or CH1641 inocula, and brain extracts from recipient mice respectively.
Mentions: We created Tg mice expressing OvPrP encoding either A or V at residue 136. Using semi-quantitative Western and immuno dot blotting we ascertained that levels of expression in the CNS of Tg(OvPrP-A136)3533+/− and Tg(OvPrP-V136)4166+/− mice were close to that of PrP expressed in the CNS of wild type mice (Fig. 1A).

Bottom Line: Moreover, the resulting OvPrP-A136 prion acquired the characteristics of the U conformer.These results, substantiated by in vitro analyses, indicated that co-expression of OvPrP-V136 altered the conversion potential of OvPrP-A136 from the S to the otherwise unfavorable U conformer.This epigenetic mechanism thus expands the range of selectable conformations that can be adopted by PrP, and therefore the variety of options for strain propagation.

View Article: PubMed Central - PubMed

Affiliation: Prion Research Center (PRC) and Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, United States of America ; Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, Kentucky, United States of America.

ABSTRACT
Although they share certain biological properties with nucleic acid based infectious agents, prions, the causative agents of invariably fatal, transmissible neurodegenerative disorders such as bovine spongiform encephalopathy, sheep scrapie, and human Creutzfeldt Jakob disease, propagate by conformational templating of host encoded proteins. Once thought to be unique to these diseases, this mechanism is now recognized as a ubiquitous means of information transfer in biological systems, including other protein misfolding disorders such as those causing Alzheimer's and Parkinson's diseases. To address the poorly understood mechanism by which host prion protein (PrP) primary structures interact with distinct prion conformations to influence pathogenesis, we produced transgenic (Tg) mice expressing different sheep scrapie susceptibility alleles, varying only at a single amino acid at PrP residue 136. Tg mice expressing ovine PrP with alanine (A) at (OvPrP-A136) infected with SSBP/1 scrapie prions propagated a relatively stable (S) prion conformation, which accumulated as punctate aggregates in the brain, and produced prolonged incubation times. In contrast, Tg mice expressing OvPrP with valine (V) at 136 (OvPrP-V136) infected with the same prions developed disease rapidly, and the converted prion was comprised of an unstable (U), diffusely distributed conformer. Infected Tg mice co-expressing both alleles manifested properties consistent with the U conformer, suggesting a dominant effect resulting from exclusive conversion of OvPrP-V136 but not OvPrP-A136. Surprisingly, however, studies with monoclonal antibody (mAb) PRC5, which discriminates OvPrP-A136 from OvPrP-V136, revealed substantial conversion of OvPrP-A136. Moreover, the resulting OvPrP-A136 prion acquired the characteristics of the U conformer. These results, substantiated by in vitro analyses, indicated that co-expression of OvPrP-V136 altered the conversion potential of OvPrP-A136 from the S to the otherwise unfavorable U conformer. This epigenetic mechanism thus expands the range of selectable conformations that can be adopted by PrP, and therefore the variety of options for strain propagation.

Show MeSH
Related in: MedlinePlus