Up-Regulation of Mcl-1 and Bak by Coronavirus Infection of Human, Avian and Animal Cells Modulates Apoptosis and Viral Replication

Virus-induced apoptosis and viral mechanisms that regulate this cell death program are key issues in understanding virus-host interactions and viral pathogenesis. Like many other human and animal viruses, coronavirus infection of mammalian cells induces apoptosis. In this study, the global gene expression profiles are first determined in IBV-infected Vero cells at 24 hours post-infection by Affymetrix array, using avian coronavirus infectious bronchitis virus (IBV) as a model system. It reveals an up-regulation at the transcriptional level of both pro-apoptotic Bak and pro-survival myeloid cell leukemia-1 (Mcl-1). These results were further confirmed both in vivo and in vitro, in IBV-infected embryonated chicken eggs, chicken fibroblast cells and mammalian cells at transcriptional and translational levels, respectively. Interestingly, the onset of apoptosis occurred earlier in IBV-infected mammalian cells silenced with short interfering RNA targeting Mcl-1 (siMcl-1), and was delayed in cells silenced with siBak. IBV progeny production and release were increased in infected Mcl-1 knockdown cells compared to similarly infected control cells, while the contrary was observed in infected Bak knockdown cells. Furthermore, IBV infection-induced up-regulation of GADD153 regulated the expression of Mcl-1. Inhibition of the mitogen-activated protein/extracellular signal-regulated kinase (MEK/ERK) and phosphoinositide 3-kinase (PI3K/Akt) signaling pathways by chemical inhibitors and knockdown of GADD153 by siRNA demonstrated the involvement of ER-stress response in regulation of IBV-induced Mcl-1 expression. These results illustrate the sophisticated regulatory strategies evolved by a coronavirus to modulate both virus-induced apoptosis and viral replication during its replication cycle

Studies on the host-virus interactions of coronaviruses

Virus-induced apoptosis and host antiviral innate immunity are key issues in understanding virus-host interactions and viral pathogenesis. Coronavirus infection of mammalian cells induces apoptotic and host innate immune responses. Global gene expression profiles are determined in coronavirus-infected Vero cells by Affymetrix array, using avian coronavirus infectious bronchitis virus (IBV) as a model system, to reveal up-regulation of both pro-apoptotic B cell lymphoma-2 (BCL-2)-antagonist/killer 1 (Bak) and pro-survival myeloid cell leukemia-1 (Mcl-1). Apoptosis occurred earlier in IBV-infected cells silenced with short interfering RNA targeting Mcl-1 (siMcl-1), and was delayed in siBak cells. Up-regulation of RNA helicases from the RIG-I-like receptor (RLR) family, Melanoma differentiation-associated gene 5 (MDA5) and Retinoic-inducible gene I (RIG-I), was also observed in IBV-infected cells, leading to downstream Mitochondrial antiviral signalling (MAVS) adaptor protein activation for interferon induction in response to viral invasion. RIG-I, MDA5 and MAVS also play a part in modulating IBV-induced apoptosis. Bcl-2 family proteins, too, regulates MAVS cleavage during apoptosis, thus further establishing a link between MAVS and intrinsic apoptotic pathway activation in the mitochondria during host innate immunity induction.DOCTOR OF PHILOSOPHY (SBS

Recent Progress in Studies of Arterivirus- and Coronavirus-Host Interactions

Animal coronaviruses, such as infectious bronchitis virus (IBV), and arteriviruses, such as porcine reproductive and respiratory syndrome virus (PRRSV), are able to manifest highly contagious infections in their specific native hosts, thereby arising in critical economic damage to animal industries. This review discusses recent progress in studies of virus-host interactions during animal and human coronavirus and arterivirus infections, with emphasis on IBV-host cell interactions. These interactions may be directly involved in viral replication or lead to the alteration of certain signaling pathways, such as cell stress response and innate immunity, to facilitate viral replication and pathogenesis

Yellow light direct hole-injection structure organic light-emitting device based on bis[2-(4-tert-butylphenyl) benzothiazolato-N,C2'] iridium (acetylicetonate) phosphor

The feasibility of adopting bis[2-(4-tert-butylphenyl) benzothIazolato-N,C-2'] iridium (acetylacetonate) [(t-bt)2Ir(acac)] in the direct hole-injection structure was investigated. Yellow phosphorescent organic light-emitting diodes based on (t-bt)2Ir(acac) with this structure were fabricated. The efficiencies of these diodes reached 27.51 lm/W and 53.33 cd/A at a brightness of 45 891 cd/m2. The realisation of these excellent efficiencies is ascribed to the characteristics of (t-bt)2Ir(acac) and the direct hole-injection structure

Upregulation of CHOP/GADD153 during coronavirus infectious bronchitis virus infection modulates apoptosis by restricting activation of the extracellular signal-regulated kinase pathway

Induction of the unfolded protein response (UPR) is an adaptive cellular response to endoplasmic reticulum (ER) stress that allows a cell to reestablish ER homeostasis. However, under severe and persistent ER stress, prolonged UPR may activate unique pathways that lead to cell death. In this study, we investigated the activation of the protein kinase R-like ER kinase (PERK) pathway of UPR in cells infected with the coronavirus infectious bronchitis virus (IBV) and its relationship with IBV-induced apoptosis. The results showed moderate induction of PERK phosphorylation in IBV-infected cells. Meanwhile, activating transcription factor 4 (ATF4) was upregulated at the protein level in the infected cells, resulting in the induction in trans of the transcription factor ATF3 and the proapoptotic growth arrest and DNA damage-inducible protein GADD153. Knockdown of PERK by small interfering RNA (siRNA) suppressed the activation of GADD153 and the IBV-induced apoptosis. Interestingly, knockdown of protein kinase R (PKR) by siRNA and inhibition of the PKR kinase activity by 2-aminopurine (2-AP) also reduced the IBV-induced upregulation of GADD153 and apoptosis induction. In GADD153-knockdown cells, IBV-induced apoptosis was suppressed and virus replication inhibited, revealing a key role of GADD153 in IBV-induced cell death and virus replication. Analysis of the pathways downstream of GADD153 revealed much more activation of the extracellular signal-related kinase (ERK) pathway in GADD153-knockdown cells during IBV infection, indicating that GADD153 may modulate apoptosis through suppression of the pathway. This study provides solid evidence that induction of GADD153 by PERK and PKR plays an important regulatory role in the apoptotic process triggered by IBV infection

High-Performance Recyclable and Malleable Epoxy Resin with Vanillin-Based Hyperbranched Epoxy Resin Containing Dual Dynamic Bonds

Dynamic covalent polymer networks represent new opportunities in the design of sustainable epoxy resins due to their excellent malleability and reprocessability; however, the adaptable network is usually accompanied by low glass transition temperature, poor creep resistance, and mechanical brittleness. Herein, we demonstrate a vanillin-based hyperbranched epoxy resin (VEHBP) containing disulfide and imine dynamic covalent bonds for recyclable and malleable epoxy resin with high glass transition temperature (Tg), significantly improved creep resistance, and mechanical properties. The dynamic covalent epoxy resin containing 5%VEHBP exhibited a high glass transition temperature of 175 °C and a creep temperature of 130 °C and a 34.1, 19.7, and 173.3% increase in tensile strength, storage modulus, and tensile toughness respectively, compared with the neat resin. Meanwhile, the hyperbranched topological structure of VEHBP complemented by dual dynamic bonds endowed these materials with excellent self-healing ability, reprocessability, and degradability, which represents an important step toward the design and fabrication of high-performance epoxy covalent adaptable networks

Effects of cavitation erosion-induced surface damage on the corrosion behaviour of TA31 Ti alloy

This study used electrochemical noise technology to analyse the effects of surface damage induced by cavitation erosion (CE) on the pitting and passivation behaviours of TA31 Ti alloy. According to the results, TA31 Ti alloy exhibited high corrosion resistance in NaCl solutions. However, the residual tensile stress layer generated during grinding and polishing reduced its passivation ability. Subsequently, the residual tensile stress layer was eliminated after CE for 1 h, improving the passivation ability of the material. Thereafter, pitting corrosion was initiated on the material surface. Increasing the CE time from 1 h to 2 h gradually decreased the passivation ability of the alloy. A large number of CE holes promoted the transition from pitting initiation to metastable pitting growth. which gradually dominated the surface of TA31 Ti alloy. The damage mechanism of uniform thinning increased the passivation ability and stability of the alloy with the increase in CE time from 2 h to 6 h. Therefore, the surface of TA31 Ti alloy was dominated by the initiation of pitting corrosion

Analysis of the expression of BCL2-related proteins in IBV-infected Vero cells, chicken fibroblast DF1 cells and chicken embryos.

<p>(A) Vero cells were infected with IBV, harvested at 0, 8, 16 and 24 hours post-infection, and lysates prepared. Western blot analysis was performed with the indicated specific antibodies, and probed with anti-actin as a loading control. (B) Chicken fibroblast DF1 cells were either infected with IBV, harvested at 8 and 16 hours post-infection and RNA extracted. RT-PCR analysis was carried out using specific primers for the indicated genes, with GAPDH as a loading control. (C) 10-day-old chicken embryos were inoculated with either mock virus (M) or IBV (1000 plaque-forming units per egg) in a 37°C incubator for 48 hours. Total RNA was extracted from homogenized tissues and used for RT-PCR using specific primers as above (B).</p

Regulation of Mcl-1 expression by MEK-1, PI3K and GADD153.

<p>(A) Induction of Mcl-1 in IBV-infected cells in the presence or absence of either 20 mM of MEK-1 inhibitor U0126 or 40 mM of PI3K inhibitor LY294002. Vero, and H1299 cells were incubated with normal medium (DMSO-), LY294002 in DMSO, U0129 in DMSO and DMSO only (DMSO+) for 1 hour, and then infected with IBV at a multiplicity of infection of approximately 2 in the presence or absence of the inhibitors. Cells were harvested at 16 hours post-infection, and total RNA extracted. The relative amounts of Mcl-1 transcripts were determined by quantitative RT-PCR and normalized against GAPDH. The relative fold of Mcl-1 induction in IBV-infected cells was determined by comparing with mock-infected cells. (B) Induction of Mcl-1 in IBV-infected cells by the pro-apoptotic transcription factor GADD153. H1299 cells were transfected with either siGADD153 or a non-targeting control for 72 hours and subsequently infected with IBV. Cells were harvested at 16, 18 and 20 hours post infection for western blot analysis using specific antibodies against the indicated proteins, with anti-actin as a loading control. M, mock infection.</p

Affymetrix array analysis of the expression of BCL2-related genes in IBV-infected Vero cells at 24 hours post-infection.

<p>Affymetrix array analysis of the expression of BCL2-related genes in IBV-infected Vero cells at 24 hours post-infection.</p