OBJECTIVE: To analyze the relationship between Chemokine IP10 and its receptor CXCR3 during prion infection. METHODS: We investigated the increases in IP10 signals, primarily localized in neurons within the brains of scrapie-infected mice, using western blotting, ELISA, co-immunoprecipitation, immunohistochemistry, immunofluorescence assays, and RT-PCR. RESULTS: Both CXCR3 levels and activation were significantly higher in the brains of scrapie-infected mice and prion-infected SMB-S15 cells. Enhanced CXCR3 expression was predominantly observed in neurons and activated microglia. Morphological colocalization of PrP ^C/PrP ^Sc with IP10/CXCR3 was observed in scrapie-infected mouse brains using immunohistochemistry and immunofluorescence. immunohistochemistry (IHC) analysis of whole brain sections further revealed increased accumulation of IP10/CXCR3 specifically in brain regions with higher levels of PrP ^Sc deposits. Co-immunoprecipitation and biomolecular interaction assays revealed the molecular interactions between PrP and IP10/CXCR3. Notably, a significantly larger amount of IP10 accumulated within prion-infected SMB-S15 cells than in the normal partner cell line, SMB-PS. Importantly, resveratrol treatment effectively suppressed prion replication in SMB-S15 cells, thereby restoring the accumulation and secretion pattern of cellular IP10 similar to that observed in SMB-PS cells. CONCLUSION Our data demonstrate that the activation of IP10/CXCR3 signaling in prion-infected brain tissues coincides with PrP ^Sc deposition. Modulation of IP10/CXCR3 signaling in the brain represents a potential therapeutic target for mitigating the progression of prion diseases.
Animals ; Receptors, CXCR3/metabolism* ; Mice ; Chemokine CXCL10/metabolism* ; Brain/metabolism* ; Scrapie/metabolism* ; Signal Transduction ; PrPSc Proteins/metabolism*

OBJECTIVE: To describe the global profiles of acetylated proteins in the brains of scrapie agents 139A- and ME7-infected mice collected at mid-early, mid-late, and terminal stages. METHODS: The acetylated proteins from the cortex regions of scrapie agent (139A- and ME7)-infected mice collected at mid-early (80 days postinfection, dpi), mid-late (120 dpi), and terminal (180 dpi) stages were extracted, and the global profiles of brain acetylated proteins were assayed with proteomic mass spectrometry. The proteins in the infected mice showing 1.5-fold higher or lower levels than that of age-matched normal controls were considered as differentially expressed acetylated peptides (DEAPs). RESULTS: A total of 118, 42, and 51 DEAPs were found in the brains of 139A-80, 139A-120, and 139A-180 dpi mice, respectively. Meanwhile, 390, 227, and 75 DEAPs were detected in the brains of ME7-80, ME7-120, and ME7-180 dpi mice, respectively. The overwhelming majority of DEAPs in the mid-early stage were down-regulated, and more portions of DEAPs in the mid-late and late stages were up-regulated. Approximately 22.1% (328/1,485) of acetylated peptides mapped to 74 different proteins were mitochondrial associated. Kyoto Encyclopedia of Genes and Genomes pathway analysis identified 39 (80 dpi), 13 (120 dpi), and 10 (180 dpi) significantly changed pathways in 139A-infected mice. Meanwhile, 55, 25, and 18 significantly changed pathways were observed in the 80, 120, and 180 dpi samples of 139A- and ME7-infected mice ( P < 0.05), respectively. Six pathways were commonly involved in all tested samples. Moreover, many steps in the citrate cycle (tricarboxylic acid cycle) were affected, represented by down-regulated acetylation for relevant enzymes in the mid-early stage and up-regulated acetylation in the mid-late and late stages. CONCLUSION Our data here illustrated the changes in the global profiles for brain acetylated proteins during prion infection, showing remarkably inhibited acetylation in the early stage and relatively enhanced acetylation in the late stage.
Animals ; Brain/metabolism* ; Citrates/metabolism* ; Mice ; Peptides/metabolism* ; PrPSc Proteins ; Proteomics ; Scrapie/metabolism* ; Sheep

Mammalian cells remove misfolded proteins using various proteolytic systems, including the ubiquitin (Ub)-proteasome system (UPS), chaperone mediated autophagy (CMA) and macroautophagy. The majority of misfolded proteins are degraded by the UPS, in which Ub-conjugated substrates are deubiquitinated, unfolded and cleaved into small peptides when passing through the narrow chamber of the proteasome. The substrates that expose a specific degradation signal, the KFERQ sequence motif, can be delivered to and degraded in lysosomes via the CMA. Aggregation-prone substrates resistant to both the UPS and the CMA can be degraded by macroautophagy, in which cargoes are segregated into autophagosomes before degradation by lysosomal hydrolases. Although most misfolded and aggregated proteins in the human proteome can be degraded by cellular protein quality control, some native and mutant proteins prone to aggregation into beta-sheet-enriched oligomers are resistant to all known proteolytic pathways and can thus grow into inclusion bodies or extracellular plaques. The accumulation of protease-resistant misfolded and aggregated proteins is a common mechanism underlying protein misfolding disorders, including neurodegenerative diseases such as Huntington's disease (HD), Alzheimer's disease (AD), Parkinson's disease (PD), prion diseases and Amyotrophic Lateral Sclerosis (ALS). In this review, we provide an overview of the proteolytic pathways in neurons, with an emphasis on the UPS, CMA and macroautophagy, and discuss the role of protein quality control in the degradation of pathogenic proteins in neurodegenerative diseases. Additionally, we examine existing putative therapeutic strategies to efficiently remove cytotoxic proteins from degenerating neurons.
Alzheimer Disease/drug therapy/metabolism ; Amyloid beta-Peptides/metabolism ; Amyotrophic Lateral Sclerosis/drug therapy/metabolism ; Animals ; Autophagy/drug effects ; DNA-Binding Proteins/metabolism ; Humans ; Huntington Disease/drug therapy/genetics/metabolism ; Lysosomes/metabolism ; Molecular Targeted Therapy ; Mutation ; Nerve Tissue Proteins/genetics/metabolism ; Neurodegenerative Diseases/drug therapy/*metabolism ; Parkinson Disease/drug therapy/metabolism ; PrPSc Proteins/metabolism ; Prion Diseases/drug therapy/metabolism ; Proteasome Endopeptidase Complex/metabolism ; Proteolysis ; Proteostasis Deficiencies/metabolism ; Superoxide Dismutase/metabolism ; Ubiquitin/metabolism ; alpha-Synuclein/metabolism ; tau Proteins/metabolism

Misfolded isoform of prion protein (PrP), termed scrapie PrP (PrP(Sc)), tends to aggregate into various fibril forms. Previously, we reported various conditions that affect aggregation of recombinant PrP into amyloids. Because amyloidogenesis of PrP is closely associated with transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans, we investigated infectivity of recombinant PrP amyloids generated in vitro. Using cultured cell lines which overexpress cellular PrP of different species, we measured the level of de novo synthesized PrP(Sc) in cells inoculated with recombinant mouse PrP amyloids. While PrP-overexpressing cells were susceptible to mouse-adapted scrapie prions used as the positive control, demonstrating the species barrier effect, infection with amyloids made of truncated recombinant PrP (PrP[89-230]) failed to form and propagate PrP(Sc) even in the cells that express mouse cellular PrP. This suggests that infectivity of PrP amyloids generated in vitro is different from that of natural prions. Recombinant PrP (89-230) amyloids tested in the current study retain no or a minute level, if any, of prion infectivity.
Animals ; Cell Line ; Kidney/*metabolism/*pathology ; Mice ; PrPSc Proteins/*metabolism ; Prion Diseases/*metabolism/*pathology ; Prions/*metabolism ; Rabbits ; Recombinant Proteins/*metabolism ; Up-Regulation

alphaB-crystallin is a member of the sHSP (Small heat shock protein) family, which plays an impor tant role in multiple neurodegeneration diseases. To give insight into the possible alternation and the role of aB-crystallin in prion disease, the alphaB-crystallin levels in the brain tissues of agent 263K-infected hamsters were evaluated. Western blots and IHC revealed that at the terminal stages of the diseases, the levels of alphaB-crystallin were increased up to 3-fold in the brain tissues of scrapie infected 263K hamsters compared with normal controls. Immunofluorescent assays revealed that the up-regulated alphaB-crystallin was mainly observed in astrocytes, but not in neurons. The co-localization between alphaB-crystallin and abnormal deposition of PrPsc in the brain tissues of the scrapie infected hamsters was not observed. The study may provide a foundation for further revealing the potential role of alphaB-crystallin in prion disease.
Animals ; Brain ; metabolism ; pathology ; Cricetinae ; Humans ; PrPSc Proteins ; metabolism ; Prion Diseases ; genetics ; metabolism ; pathology ; Up-Regulation ; alpha-Crystallin B Chain ; genetics ; metabolism

Animals ; PrPSc Proteins ; metabolism ; pathogenicity ; Prion Diseases ; transmission ; Prions ; physiology

In human prion diseases, phosphorylated-tau deposition has been described in a rare genetic form, Gerstmann-Straussler-Scheinker disease, but is not considered part of the neuropathological picture of Creutzfeldt-Jakob disease. To investigate the possible changes of tau and phosphorylated tau (Ser396/Ser404) in transmissible spongiform encephalopathies (TSEs), the expressions and transcriptions of above biological factors in the brain tissues of 263K- and 139A-infected hamsters were evaluated by Western blots and Real Time PCR, respectively, followed by quantitative analyses of immunoblot images and relative transcriptional levels compared with normal animals. The contents of total tau increased, but phosphorylated tau at Ser396 and Ser404 decreased, regardless of the types of scrapie agents and clinical incubations. Transcriptions of two tau isoforms were also markedly increased. These findings suggested that dephosphorylation of tau at Ser396/Ser404 was a illness-correlative phenomenon in TSEs. Alterations of tau and phosphorylated tau (Ser396/Ser404) were either intermediate or consequent events in TSE pathogenesis and proposed the potential linkage of these bioactive proteins with the pathogenesis of prion diseases.
Animals ; Blotting, Western ; Brain ; metabolism ; Cricetinae ; Gene Expression Regulation ; physiology ; Phosphorylation ; Polymerase Chain Reaction ; PrPSc Proteins ; pathogenicity ; Prion Diseases ; metabolism ; tau Proteins ; metabolism

In order to establish an amplification system in vitro with which the PrP(Sc) is able to convert PrP(C) into proteinase K-resistant isoform infinitely and whether this system is more efficient than conventional protein misfolding cyclic amplification (PMCA), scrapie strain 263K-infected hamster's brain homogenate and homologous normal brain homogenate were prepared, respectively. A new methodology, namely serial PMCA, was utilized to reveal the continuous propagation ability of PrP(Sc). Totally 8 rounds of serial PMCA were proceeded and each round contained 48 cycles of alternative sonication and incubation. Simultaneously 144 cycles of conventional PMCA was used as a control. The results showed the PrP(Sc) from hamsters' brain tissues of scrapie agent 263K could replicate efficiently and infinitely with serial PMCA compared with finite propagation of PrP(Sc) with conventional PMCA system. The study of PrP(Sc) continuous propagation in brain homogenate with serial PMCA may further provide insight into the unsettled mechanism of prions misfolding and replication and apply to detect trace amount of PrP(Sc).
Animals ; Brain ; metabolism ; Cricetinae ; PrPC Proteins ; chemistry ; PrPSc Proteins ; chemistry ; Protein Folding

To establish a new Western blotting assay for PrP(Sc) detection, we optimized the Western blotting assay with a precipitation procedure of streptomycin sulfate. After digestion with PK, 10% scrapie infected hamster brain homogenates were incubated with 60 mmol/L streptomycin and the precipitated PrP(Sc) was recovered by centrifugation. The enrichment of PrP(Sc) by streptomycin sulfate precipitation was evaluated using Western blotting assay. The results showed streptomycin could bind to PK-treated PrP(Sc), forming high molecular masses, but not influence the glycosylated patterns on SDS-PAGE. Western blot assay revealed that the detective sensitivity of the streptomycin-precipitation PrP(Sc) was remarkably improved. As a sensitive, specific, rapid and flexible protocol for PrP(Sc), the protocol in this study has the potential utility, alone or combined with other techniques, for the detection of low level PrP(Sc) in the specimens from central nerve system, or from peripheral organs or body fluids.
Animals ; Blotting, Western ; methods ; Brain ; metabolism ; pathology ; Brain Chemistry ; Chemical Precipitation ; Cricetinae ; PrPSc Proteins ; chemistry ; isolation & purification ; metabolism ; Prion Diseases ; diagnosis ; metabolism ; Reproducibility of Results ; Sensitivity and Specificity ; Streptomycin ; chemistry

OBJECTIVETo study the possible effect of tetracycline on protease-resistant activity in vitro and infectivity in vivo of a scrapie strain 263K.

METHODSScrapie pathogens were incubated with tetracycline at different concentrations for various periods of time and protease-resistant PrP signals were evaluated with proteinase K-treatment and Western blots. The preparations treated with tetracycline were intracerebrally inoculated into golden hamsters and typical TSE manifestations were noted. PrPSc in brain tissues of the infected animals was detected by PrP specific Western blot assays.

RESULTSProtease-resistant PrP was significantly reduced in or removed from the preparations treated with tetracycline in a dose-dependant manner. Compared with the control group after incubated for 53.75 +/- 0.50 days, the preparations treated with 5 mmol/L and 20 mmol/L tetracycline prolonged the incubation time of 61.5 +/- 1.73 and 59.5 +/- 0.58 days (P < 0.05).

CONCLUSIONTreatment of scrapie pathogen 263K with tetracycline reduces or removes its protease-resistant activity in vitro.

Animals ; Brain ; pathology ; Cricetinae ; Peptide Hydrolases ; metabolism ; PrPSc Proteins ; metabolism ; pathogenicity ; Scrapie ; pathology ; Tetracycline ; pharmacology ; Time Factors