Dataset Information

The effect of PrP(Sc) accumulation on inflammatory gene expression within sheep peripheral lymphoid tissue.

ABSTRACT: Accumulation of the misfolded prion protein, PrP(Sc) in the central nervous system (CNS) is strongly linked to progressive neurodegenerative disease. For many transmissible spongiform encephalopathies (TSEs), peripheral lymphoid tissue is an important site of PrP(Sc) amplification but without gross immunological consequence. Susceptible VRQ homozygous New Zealand Cheviot sheep were infected with SSBP/1 scrapie by inoculation in the drainage area of the prescapular lymph nodes. The earliest time that PrP(Sc) was consistently detected by immunohistology in these nodes was D50 post infection. This transcriptomic study of lymph node taken before (D10) and after (D50) the detection of PrP(Sc), aimed to identify the genes and physiological pathways affected by disease progression within the nodes as assessed by PrP(Sc) detection. Affymetrix Ovine Gene arrays identified 75 and 80 genes as differentially-expressed at D10 and D50, respectively, in comparison with control sheep inoculated with uninfected brain homogenate. Approximately 70% of these were repressed at each time point. RT-qPCR analysis of seven genes showed statistically significant correlation with the array data, although the results for IL1RN and TGIF were different between the two technologies. The ingenuity pathway analysis (IPA) and general low level of repression of gene expression in lymphoid tissue, including many inflammatory genes, contrasts with the pro-inflammatory and pro-apoptotic events that occur within the CNS at equivalent stages of disease progression as assessed by PrP(Sc) accumulation.

SUBMITTER: Gossner AG

PROVIDER: S-EPMC4678288 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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The effect of PrP(Sc) accumulation on inflammatory gene expression within sheep peripheral lymphoid tissue.

Gossner Anton G AG Hopkins John J

Veterinary microbiology 20151017 3-4

Accumulation of the misfolded prion protein, PrP(Sc) in the central nervous system (CNS) is strongly linked to progressive neurodegenerative disease. For many transmissible spongiform encephalopathies (TSEs), peripheral lymphoid tissue is an important site of PrP(Sc) amplification but without gross immunological consequence. Susceptible VRQ homozygous New Zealand Cheviot sheep were infected with SSBP/1 scrapie by inoculation in the drainage area of the prescapular lymph nodes. The earliest time ...[more]

PMID: 26507419

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Project description:Neuroinflammation is recognized as one of the obligatory pathogenic features of neurodegenerative diseases including Alzheimer's, Parkinson's or prion diseases. In prion diseases, space and time correlations between deposition of disease-associated, pathogenic form of the prion protein or PrPSc and microglial-mediated neuroinflammation has been established. Yet, it remains unclear whether activation of microglia is triggered directly by a contact with PrPSc, and what molecular features of PrPSc microglia sense and respond to that drive microglia to inflammatory states. The current study asked the questions whether PrPSc can directly trigger activation of microglia and whether the degree of microglia response depends on the nature of terminal carbohydrate groups on the surface of PrPSc particles. PrPSc was purified from brains of mice infected with mouse-adapted prion strain 22L or neuroblastoma N2a cells stably infected with 22L. BV2 microglial cells or primary microglia were cultured in the presence of purified 22L. We found that exposure of BV2 cells or primary microglia to purified PrPSc triggered proinflammatory responses characterized by an increase in the levels of TNFα, IL6, nitric oxide (NO) and expression of inducible Nitric Oxide Synthase (iNOS). Very similar patterns of inflammatory response were induced by PrPSc purified from mouse brains and neuroblastoma cells arguing that microglia response is independent of the source of PrPSc. To test whether the microglial response is mediated by carbohydrate epitopes on PrPSc surface, the levels of sialylation of PrPSc N-linked glycans was altered by treatment of purified PrPSc with neuraminidase. Partial cleavage of sialic acid residues was found to boost the inflammatory response of microglia to PrPSc. Moreover, transient degradation of Iκβα observed upon treatment with partially desialylated PrPSc suggests that canonical NFκB activation pathway is involved in inflammatory response. The current study is the first to demonstrate that PrPSc can directly trigger inflammatory response in microglia. In addition, this work provides direct evidence that the chemical nature of the carbohydrate groups on PrPSc surface is important for microglial activation.

Project description:It is established that prion protein is the sole causative agent in a number of diseases in humans and animals. However, the nature of conformational changes that the normal cellular form, PrP(C), undergoes in its conversion to a self-replicating state is still not fully understood. The ordered C-terminus of PrP(C) proteins has three helices (H1-H3). Here, we use statistical coupling analysis (SCA) to infer covariations at various locations using a family of evolutionarily related sequences and the response of mouse and human PrP(C)s to mechanical force to decipher the initiation sites for the transition from PrP(C) to an aggregation-prone PrP* state. Sequence-based SCA predicts that the clustered residues in nonmammals are localized in the stable core (near H1) of PrP(C), whereas in mammalian PrP(C), they are localized in frustrated helices H2 and H3 where most of the pathogenic mutations are found. Force-extension curves and free energy profiles as a function of extension of mouse and human PrP(C) in the absence of a disulfide (SS) bond between residues Cys179 and Cys214, generated by applying mechanical force to the ends of the molecule, show a sequence of unfolding events starting first with rupture of H2 and H3. This is followed by disruption of structure in two strands. Helix H1, stabilized by three salt bridges, resists substantial force before unfolding. Force extension profiles and the dynamics of rupture of tertiary contacts also show that even in the presence of an SS bond the instabilities in most of H3 and parts of H2 still determine the propensity to form the PrP* state. In mouse PrP(C) with an SS bond, there are ?10 residues that retain their order even at high forces. Both SCA and single-molecule force simulations show that in the conversion from PrP(C) to PrP(SC) major conformational changes occur (at least initially) in H2 and H3, which because of their sequence compositions are frustrated in the helical state. Implications of our findings for the structural model for the scrapie form of PrP(C) are discussed.

Dataset Information

The effect of PrP(Sc) accumulation on inflammatory gene expression within sheep peripheral lymphoid tissue.

Publications

The effect of PrP(Sc) accumulation on inflammatory gene expression within sheep peripheral lymphoid tissue.

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