Direct interaction of DNMT inhibitors to PrP suppresses pathogenic process of prion

The conversion of the normal cellular prion protein (PrP) to the misfolded pathogenic scrapie prion protein (PrP) is the biochemical hallmark of prion replication. So far, various chemical compounds that inhibit this conformational conversion have been identified. Here, we report the novel anti-prion activity of SGI-1027 and its meta/meta analogue (M/M), previously known only as potent inhibitors of DNA methyltransferases (DNMTs). These compounds effectively decreased the level of PrP in cultured cells with permanent prion infection, without affecting PrP at the transcriptional or translational levels. Furthermore, SGI-1027 prevented effective prion infection of the cells. In a PrP aggregation assay, both SGI-1027 and M/M blocked the formation of misfolded PrP aggregates, implying that binding of these compounds hinders the PrP conversion process. A series of binding and docking analyses demonstrated that both SGI-1027 and M/M directly interacted with the C-terminal globular domain of PrP, but only SGI-1027 bound to a specific region of PrP with high affinity, which correlates with its potent anti-prion efficacy. Therefore, we report SGI-1027 and related compounds as a novel class of potential anti-prion agents that preferentially function through direct interaction with PrP.

Cellular prion protein-mediated hippocampal neuron axon elongation impairment involved in cognitive impairment induced by sleep deprivation / 中华神经科杂志

Objective To investigate the effect of rapid eye movement (REM) sleep deprivation on spatial memory and hippocampal cellular prion protein (PrPC) expression and to explore the underlying mechanism of cognitive impairment induced by sleep deprivation.Methods Adult Sprague-Dawley rats were sorted by weight,randomly divided into three groups:the cage control (CC) group,the tank control (TC) group,and the sleep deprivation (SD) group.Rats were deprived of REM sleep for 72 h using the modified multiple platform method.The Morris water maze task was used to assess hippocampal-dependent spatial memory.After sleep deprivation,the rats were sacrificed and their brain tissue was analyzed for PrPC protein expression via Western blotting.Hippocampal neuron axon elongation was examined as well after lentivector-mediated RNA interference (RNAi) of PrPC in primary cultured rat hippocampal neurons.Results REM sleep deprivation for 72 h resulted in spatial memory impairment.The number of times of rats passing through the platform was decreased significantly in the SD group (3.17 ±0.95) compared with the CC (7.17 ±0.95) and TC (6.50 ±0.62) groups (Z =2.026 6,Z =2.026 6,P ＜0.05),the mean value of proximity to the platform (mm) was greater for rats of the SD group (711.74 ± 33.99) compared to those of theCC (592.32±31.31) andTC (580.86±11.36) groups (Z=-2.001 6,Z=-2.4820,P ＜ 0.05).REM sleep deprivation for 72 h resulted in reduced PrPC level in the hippocampus (0.33 ± 0.10) compared with the CC (1.01 ±0.33) and TC (0.96 ±0.27) groups (Z=2.152 9,Z=2.152 9,P ＜ 0.05).In primary cultured hippocampal neurons,axon elongation(μm) was inhibited 7 days in infected neurons (326.28 ± 12.53) compared with normal (555.00 ±30.43) or negative control (558.70 ±23.10) cells (Z =4.768 4,Z =4.877 0,P ＜ 0.05).Conclusion These findings suggest that PrPC-mediated hippocampal neuron axon elongation inhibition is probably involved in spatial memory impairment induced by sleep deprivation in rats.

O papel da proteína prion celular na regulação da resposta à insulina / The role of cellular prion protein in the regulation of insulin signaling

A proteína Príon Celular ou PrPc, é uma molécula de superfície celular responsável por desencadear várias cascatas de transdução de sinal e mediar muitos processos fisiológicos como proteção contra apoptose, indução da proliferação, adesão celular entre outros. Devido à sua grande gama de efeitos, hoje se acredita que PrPc seja um organizador de plataformas lipídicas, ou lipid rafts, na membrana celular. O receptor de insulina é uma proteína transmembrana também presente em plataformas lipídicas e, interessantemente, a ausência de componentes destas plataformas, como caveolinas, por exemplo, leva a uma deficiência na resposta a insulina. Desta maneira, acreditávamos que a ausência de PrPc poderia levar a uma desregulação das plataformas lipídicas e a uma sinalização ineficiente do receptor de insulina. De fato, pudemos observar a influência de PrPc no controle da glicemia sérica, através de experimentos com camundongos que fizeram ingestão de rações com conteúdo controlado de gordura. Foi possível verificar que camundongos deficientes para PrPc não possuem controle adequado da glicemia, de peso e dos níveis de insulina. Estes resultados foram confirmados em duas cepas diferentes de camundongos deficientes para PrPc. Por outro lado, camundongos que superexpressam PrPc apresentam controle adequado de glicemia por mais tempo que camundongos do tipo-selvagem quando alimentados com dietas de alta porcentagem de gordura, sugerindo que a superexpressão de PrPc promoveria uma resistência ao diabetes tipo II, com maior sensibilidade a insulina. As análises histológicas também mostraram que os animais deficientes para PrPc apresentam esteatose hepática mais acentuada do que os animais do tipo selvagem, assim como hipertrofia dos adipócitos, o que é característico de obesidade. Porém ao longo dos nossos estudos com fibroblastos derivados de camundongos deficientes para PrPc, do tipo selvagem e que superexpressam PrPc, pudemos verificar...

The cellular prion protein or PrPc is a cell surface molecule responsible for triggering various signal transduction cascades and mediate many physiological processes such as protection against apoptosis, inducing proliferation, cell adhesion, among others. Due to its wide range of effects, it is believed that PrPc is a lipid raft organizer in the cell membrane. The insulin receptor is a transmembrane protein also present in lipid rafts. Interestingly, the absence of lipid rafts’s components as caveolins, for example, leads to a deficiency in insulin response. Thus, we believed that the absence of PrPc could lead to a dysregulation of lipid rafts and inefficient insulin receptor signaling. In fact, we observed the influence of PrPc in the control of serum glucose, through experiments with mice that ingested diets with controlled fat content. We found that mice deficient for PrPc do not have adequate control of blood glucose, weight gain and insulin levels. These results were confirmed in two different strains of PrPc knockout mice. On the other hand, mice overexpressing PrPc exhibit adequate control of blood glucose longer than wild-type mice when fed with high fat chow, suggesting that overexpression of PrPc promote resistance to Type II diabetes, with greater insulin sensitivity. The histological analysis also showed that PrPc deficient mice exhibit more pronounced hepatic steatosis than wild-type animals, as well as adipocyte hypertrophy, which is characteristic of obesity. However, throughout our studies with fibroblasts derived from mice deficient for PrPc, wild-type and overexpressing PrPc, we could not prove our initial hypothesis of change in insulin receptor activity. However, we observed that mice deficient for PrPc have lesser amounts of PPAR-y, a transcription factor involved in adipocyte differentiation that has influence on glucose regulation. Additionally, by flow cytometry, we found that the translocation of the glucose transporter Glut4...

The Soluble Form of the Cellular Prion Protein Enhances Phagocytic Activity and Cytokine Production by Human Monocytes Via Activation of ERK and NF-kappaB

The PrP(C) is expressed in many types of immune cells including monocytes and macrophages, however, its function in immune regulation remains to be elucidated. In the present study, we examined a role for PrP(C) in regulation of monocyte function. Specifically, the effect of a soluble form of PrP(C) was studied in human monocytes. A recombinant fusion protein of soluble human PrP(C) fused with the Fc portion of human IgG1 (designated as soluble PrP(C)-Fc) bound to the cell surface of monocytes, induced differentiation to macrophage-like cells, and enhanced adherence and phagocytic activity. In addition, soluble PrP(C)-Fc stimulated monocytes to produce pro-inflammatory cytokines such as TNF-alpha, IL-1beta, and IL-6. Both ERK and NF-kappaB signaling pathways were activated in soluble PrP(C)-treated monocytes, and inhibitors of either pathway abrogated monocyte adherence and cytokine production. Taken together, we conclude that soluble PrP(C)-Fc enhanced adherence, phagocytosis, and cytokine production of monocytes via activation of the ERK and NF-kappaB signaling pathways.

Cytotoxic effects of differentiated PC12 cell infected by prion protein 106-126 peptide / 中国医师杂志

Objective To investigate the cytotoxic effects of differentiated PC12 cells afterinfected by prion protein 106-126 peptide.Methods The PC12 cells were infected by prion protein 106-126peptide after differentiated by nerve growthfactor(NGF).Cell viability andthe morphological changes were observed.The energy metabolize and apoptosis was detected.Results Afterinfected by this peptide,cell viability decreasedfrom(98.1±1.9)% to (69.2±4.7)%,and apoptosis peak Was observed byflow cytometry.Aboutthe process of the cytotoxic effects,afterthe cells affected by PrP106-126,oxidative stress presented and existed continually,and then the intracellular free calcium concentrate increased from (185.74±12.93)nmol/L to (493.00±58.71)nmol/L subsequently,the activity of Ca2+ ATPase decreased from 54.92±4.05 to 34.92±4.86,the mitochondrial membrane potential decreasedto 65%,and also the energy metabolize disorder,the cells presented apoptosisinthe end.The changed Bcl-2/Bax system involvedinthe apoptosis.Conclusions Prion protein106-126 peptide caninduce apoptosisin differentiated PC12 cells and presented cellulartoxicity definitely.It might be a perfect model to study the cellular toxicity of prion protein.Continual oxidative stress could causetheintracellularfree calcium concentrate and disturb the energy metabolize,and the apoptosis might be the end-result.The oxidative stress of might play a startup and important role.

Avaliação da expressão de PrPc na interação neurônio-glia, em astrócitos e os mecanismos de secreção de STI1 / Avaliation of PrPc expression in neuron-glia crosstalk, in astrocytes and the mechanisms of STI1 secretion

As funções fisiológicas da proteína prion (PrPc) estão sob ampla investigação e caracterização, especialmente as funções associadas ao desenvolvimento cerebral. Destaca-se que a associação de PrPc com Stress Inducible Protein 1 (STI1), induz neuritogênese e neuroproteção via proteína cinase extracelular reguladora (ERK) e proteína cinase dependente de AMPc (PKA) respectivamente. O presente estudo avaliou como a expressão de PrP cem astrócitos pode modular a interação neurônioglia e o papel de STI1 como um fator autócrino em astrócitos. PrPc modula a interação neurônio-glia, a produção de fatores tróficos solúveis e a organização da laminina secretada na matriz extracelular pelos astrócitos. Desta forma, a expressão de PrP ctanto em astrócitos quanto em neurônios é essencial para a neuritogênese e sobrevivência neuronal. O papel autócrino de STI1 em astrócitos também foi demonstrado. A interação PrPc-STI1 previne a morte celular por ativação da via de PKA, e ativa a diferenciação astrocitária, de uma forma protoplasmática para uma fibrosa pela indução de ERK1/2. De acordo com estes resultados, um menor grau de diferenciação é encontrado em camundongos deficientes para PrPc...

The physiological functions of PrPc are under intense investigation and characterization, particularly those associated with brain development. In neurons, the association of PrPc with its ligand, STI1, induces neuritogenesis and neuroprotection via ERK and PKA signaling pathways, respectively. The present study evaluated whether PrPc expression in astrocytes modulates neuron-glia crosstalk and the autocrine role of STI1 in astrocytes. PrPc modulates neuron-glia interaction, the production and secretion of soluble factors, and the organization of the laminin in the extracellular matrix. PrPc expression in neurons and astrocytes is essential to neuritogenesis and neuronal survival. The autocrine role of STI1 in astrocytes was also demonstrated. The PrPc-STI1 interaction prevents cell death in a PKA-dependent manner, and induces astrocyte differentiation, from a flat to a process-bearing morphology in an ERK1/2 dependent manner. We showed that PrPccnull astrocytes presented a slower rate of astrocyte maturation than wild-type ones, with reduced expression of GFAP and increased vimentin and nestin expression...

Immunohistochemical detection of Prion protein (PrP-Sc) and epidemiological study of BSE in Korea

Though the aetiology of transmissible spongiform encephalopathies (TSEs) remains uncertain, proteinase resistant prion protein (PrP-Sc), a converted form of the normal cellular prion protein (PrP-C), accumulates in the lysosome of cells of the nervous systems of animals with TSEs. In this study, clinical and epidemiological examinations of bovine spongiform encephalopathy (BSE) were conducted in Korea. During the investigated period, none of the cattle exhibited typical clinical signs of BSE, such as behavioral disturbances, high sensitivity, and abnormal locomotion. Immunohistochemical analysis and western immunoblotting were established to detect PrP-Sc in the brain tissue using monoclonal antibody (MAb) F89/160.1.5, produced by immunizing mice with a synthetic peptide which corresponds to bovine PrP residues 146-159, NH2-SRPLIHFGSDYEDRC-COOH. Although some BSE-like spongiform changes were observed in bovine brains randomly collected from Korean slaughterhouses from 1996 to 1999, no PrP-Sc was detected in those brains with the established immunohistochemistry and western immunoblotting assay. Also, no positive reaction was observed in bovine brains infected with rabies. These immunohistochemical and western immunoblotting methods using MAbs, specifically reactive with conserved epitopes on ruminant PrP, can be used for postmortem diagnosis of BSE. Further, the method can be applied to antemortem and the preclinical diagnosis of ovine scrapie by detecting PrP-Sc in lymphoid tissues, such as the tonsils, third eyelid or peripheral lymph nodes.