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Enterovirus 71 induces anti-viral stress granule-like structures in RD cells.

ABSTRACT: Stress granules (SGs) are dynamic cytoplasmic granules formed in response to a variety of stresses, including viral infection. Several viruses can modulate the formation of SG with different effects, but the relationship between SG formation and EV71 infection is poorly understood. In this study, we report that EV71 inhibits canonical SGs formation in infected cells and induces the formation of novel RNA granules that were distinguished from canonical SGs in composition and morphology, which we termed 'SG like structures'. Our results also demonstrated that EV71 triggered formation of SG-like structures is dependent on PKR and eIF2? phosphorylation and requires ongoing cellular mRNA synthesis. Finally, we found that SG-like structures are antiviral RNA granules that promote cellular apoptosis and suppress EV71 propagation. Taken together, our findings explain the formation mechanism of SG-like structures induced by EV71 and shed light on virus-host interaction and molecular mechanism underlying EV71 pathogenesis.

SUBMITTER: Zhu Y

PROVIDER: S-EPMC7124267 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Enterovirus 71 induces anti-viral stress granule-like structures in RD cells.

Zhu Yuanmei Y Wang Bei B Huang He H Zhao Zhendong Z

Biochemical and biophysical research communications 20160520 4

Stress granules (SGs) are dynamic cytoplasmic granules formed in response to a variety of stresses, including viral infection. Several viruses can modulate the formation of SG with different effects, but the relationship between SG formation and EV71 infection is poorly understood. In this study, we report that EV71 inhibits canonical SGs formation in infected cells and induces the formation of novel RNA granules that were distinguished from canonical SGs in composition and morphology, which we ...[more]

PMID: 27216457

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Project description:AimTo characterise the viral kinetics of enterovirus 71 (EV71).MethodsIn this study, human rhabdomyosarcoma (RD) cells were infected with EV71 at different multiplicity of infection (MOI). After infection, the cytopathic effect (CPE) was monitored and recorded using a phase contrast microscope associated with a CCD camera at different time points post viral infection (0, 6, 12, 24 h post infection). Cell growth and viability were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in both EV71 infected and mock infected cells at each time point. EV71 replication kinetics in RD cells was determined by measuring the total intracellular viral RNA with real-time reverse-transcription polymerase chain reaction (qRT-PCR). Also, the intracellular and extracellular virion RNA was isolated and quantified at different time points to analyze the viral package and secretion. The expression of viral protein was determined by analyze the levels of viral structure protein VP1 with Western blotting.ResultsEV71 infection induced a significant CPE as early as 6 h post infection (p.i.) in both RD cells infected with high ratio of virus (MOI 10) and low ratio of virus (MOI 1). In EV71 infected cells, the cell growth was inhibited and the number of viable cells was rapidly decreased in the later phase of infection. EV71 virions were uncoated immediately after entry. The intracellular viral RNA began to increase at as early as 3 h p.i. and the exponential increase was found between 3 h to 6 h p.i. in both infected groups. For viral structure protein synthesis, results from western-blot showed that intracellular viral protein VP1 could not be detected until 6 h p.i. in the cells infected at either MOI 1 or MOI 10; and reached the peak at 9 h p.i. in the cells infected with EV71 at both MOI 1 and MOI 10. Simultaneously, the viral package and secretion were also actively processed as the virus underwent rapid replication. The viral package kinetics was comparable for both MOI 1 and MOI 10 infected groups. It was observed that at 3 h p.i, the intracellular virions obviously decreased, thereafter, the intracellular virions began to increase and enter into the exponential phase until 12 h p.i. The total amounts of intracellular virons were decreased from 12 to 24 h p.i. Consistent with this result, the increase of virus secretion occurred during 6 to 12 h p.i.ConclusionThe viral kinetics of EV71 were established by analyzing viral replication, package and secretion in RD cells.

Project description:We have previously shown that Heparin (Hep) significantly inhibited Enterovirus 71 (EV71) infection and binding in both Vero and a human neural cell line, SK-N-SH, in vitro. Therefore, in this study we intended to gain insight into the cellular and molecular mechanisms of action of Hep against clinical EV71 infection in SK-N-SH cells. Instead of stating a long list of gene functions and pathways, we tried to select for EV71-induced genes that were exclusively affected by antiviral activity of Hep through a multi-level comparison and characterization. Overall, our microarray analysis may suggest that Hep might exert its anti-EV71 activity in SK-N-SH cells, at least in part, through the following mechanisms: i. Reduction of the down-regulation effect of EV71 on TOX that would lead to an increased population of effective, mature T-cells and NK-cells; ii. Reduction of the up-regulation effect of EV71 on GIP, that in turn, would reduce recruiting different GPCRs, leading to a reduced viral infection in host cells; iii. Partially neutralization of the EV71-mediated apoptosis through expression of CARP2 that acts as an anti-apoptosis ubiquitin protein ligase (E3). EV71 is a neurovirological virus that can sometimes cause severe and fatal CNS complications in infected patients. Since still there is no approved drug for prophylaxis of EV71-casued disease, discovering a molecular drug target(s) for EV71 infection would be crucial. This was the first study to report direct assessment of mechanisms of action of antivirals against EV71 infection. SK-N-SH cells were infected with a clinical EV71 isolate followed by treatment with 125 µg/mL of Hep. At 72 hours post infection, antiviral activity and cytotoxicity of Hep at 125 µg/mL in 12-well plates were carried out at the same time as RNA extraction. This way, we could ensure that we would assess transcript profiles of the host cells under the same condition and time as assessment of antiviral activity and cytotoxicity for the same replicates. Changes in expression profiles of the host cells were comparatively assessed under four conditions: cell control (neither infection nor treatment, designated CC), treated only with Hep (compound control, designated Cyto), EV71-infected cells treated with Hep (treatment, designated H), and infected with EV71 without treatment with Hep (virus control, designated V). All experiments were applied in triplicate, and totally twelve GeneChip® Human Gene 1.0 ST arrays were purchased from Affymetrix and processed. Then, the following five contrasts were made: Hep vs. CC; VC vs. CC; Cyto vs CC; Hep vs. VC; and Hep vs. Cyto. For each contrast, only samples from the two target groups were included. The statistical parameters of ANOVAs, p values, multiple test corrections, and fold changes were calculated within each contrast. Then, a multi-level selection and analysis procedure was employed in order to attribute changes in the gene transcription level to antiviral activity of Hep.

Project description:We have previously shown that Heparin (Hep) significantly inhibited Enterovirus 71 (EV71) infection and binding in both Vero and a human neural cell line, SK-N-SH, in vitro. Therefore, in this study we intended to gain insight into the cellular and molecular mechanisms of action of Hep against clinical EV71 infection in neural cells. Instead of stating a long list of gene functions and pathways, we tried to select for EV71-induced genes that were exclusively affected by antiviral activity of Hep through a multi-level comparison and characterization. Overall, the findings of this study suggest several molecular targets by which Hep might exert its antiviral activity against clinical EV71 infection in neural cells. Mostly, Hep appeared to modulate induction effect of EV71 on several genes in a way that may benefit the host cell and inhibit the viral infection. The most important genes where expression patterns were significantly changed by Hep include genes related to; (i) cell growth, (ii) DNA repair and replication, (iii) cytoplasmic microfilaments and related apoptosis, (iv) regulation of energy metabolism and mitochondrion-related apoptosis, (v) cytoplasmic viral transport, (vi) transmembrane proteins and the related signaling pathways, (vii) phosphoribosyltransferase, (viii) transcription factors, (ix) G protein-coupled receptors and G protein-coupled receptors-interacting proteins, (x) remodeling actin filament assembly, (xi) chemokin receptors, and (xii) immunosuppression. In addition, Hep sometimes appeared to be harmful for cells, like the case in that Hep likely suppresses regulation of Metallothionein 1E. Furthermore, it should not be ignored that the Hep-caused affects seen in this microarray analysis may partially be attributed to a significant inhibitory effect of Hep on EV71 entry into the cells. In conclusion, we propose that our microarray findings may suggest new directions for further studies on molecular targets of anti-EV71 activity of Hep. EV71 is a neurovirological virus that can cause severe and fatal CNS complications in infected patients. There is no approved drug for prophylaxis of EV71-casued disease and discovering a molecular drug target(s) for EV71 infection would be beneficial. The microarray analysis reported here was a large-scale microarray pilot study and thus further confirmatory experiments such as real time RT PCR and Western blotting would be warranted in order to confirm the mode of action of Hep implied here.

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Enterovirus 71 induces anti-viral stress granule-like structures in RD cells.

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Enterovirus 71 induces anti-viral stress granule-like structures in RD cells.

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