Muscovy duck reovirus p10.8 protein induces ER stress and apoptosis through the Bip/IRE1/XBP1 pathway

Duck Tembusu virus NS3 protein induces apoptosis by activating the PERK/PKR pathway and mitochondrial pathway

IMPORTANCE

Duck Tembusu virus (DTMUV) is an emerging pathogenic flavivirus that replicates well in mosquito, bird, and mammalian cells. An in vivo study revealed that BALB/c mice and Kunming mice were susceptible to DTMUV after intracerebral inoculation. Moreover, there are no reports about DTMUV-related human disease, but antibodies against DTMUV and viral RNA were detected in the serum samples of duck industry workers. This information implies that DTMUV has expanded its host range and poses a threat to mammalian health. Thus, understanding the pathogenic mechanism of DTMUV is crucial for identifying potential antiviral targets. In this study, we discovered that NS3 can induce the mitochondria-mediated apoptotic pathway through the PERK/PKR pathway; it can also interact with voltage-dependent anion channel 2 to induce apoptosis. Our findings provide a theoretical basis for understanding the pathogenic mechanism of DTMUV infection and identifying potential antiviral targets and may also serve as a reference for exploring the pathogenesis of other flaviviruses.

Fowl adenovirus serotype 4 52/55k protein triggers PKR degradation by ubiquitin-proteasome system to evade effective innate immunity

The pro- and inflammatory cytokines fail to effectively inhibit FAdV-4, which has always puzzled us. In the current study, the data determined that the mRNA levels of interferons were significantly enhanced in the livers and LMH cells from 24 h to 72 h post FAdV-4 infection. But the viral load of FAdV-4 was still significantly increased, which meant that FAdV-4 evaded innate immune response. We additionally revealed that the protein levels not mRNA levels of PKR were degraded in host cell at 48 h post FAdV-4 infection. Moreover, the results of over expression and silent expression of PKR revealed that PKR could inhibit FAdV-4 proliferation. These results indicated that FAdV-4 degraded the protein levels of PKR to evade innate immune response. We also found that the protein degradation levels of PKR induced by FAdV-4 were recovery in LHM cells after treatment with proteasome inhibitor MG132, and ubiquitin-specific proteases inhibitor DUB-IN-1. Furthermore, our current data presented that FAdV-4 52/55 K protein directly interacted with PKR and degraded it determined by Co-immunoprecipitation and immunofluorescence. We also determined that 52/55 K protein triggered PKR degradation, and the degradation of PKR could be recovery in LHM cells after treatment with MG132, or DUB-IN-1, respectively. Finally, our data demonstrated that 52/55 K protein was a ubiquitylase that could directly degrade PKR protein in host cells via the ubiquitin-proteasome pathway. Therefore, the current study firstly revealed that FAdV-4 52/55 K protein played the key role in triggering PKR degradation by ubiquitin-proteasome system pathway to escape from innate immunity response.

Endoplasmic Reticulum Stress of Gut Enterocyte and Intestinal Diseases

The endoplasmic reticulum, a vast reticular membranous network from the nuclear envelope to the plasma membrane responsible for the synthesis, maturation, and trafficking of a wide range of proteins, is considerably sensitive to changes in its luminal homeostasis. The loss of ER luminal homeostasis leads to abnormalities referred to as endoplasmic reticulum (ER) stress. Thus, the cell activates an adaptive response known as the unfolded protein response (UPR), a mechanism to stabilize ER homeostasis under severe environmental conditions. ER stress has recently been postulated as a disease research breakthrough due to its significant role in multiple vital cellular functions. This has caused numerous reports that ER stress-induced cell dysfunction has been implicated as an essential contributor to the occurrence and development of many diseases, resulting in them targeting the relief of ER stress. This review aims to outline the multiple molecular mechanisms of ER stress that can elucidate ER as an expansive, membrane-enclosed organelle playing a crucial role in numerous cellular functions with evident changes of several cells encountering ER stress. Alongside, we mainly focused on the therapeutic potential of ER stress inhibition in gastrointestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer. To conclude, we reviewed advanced research and highlighted future treatment strategies of ER stress-associated conditions.

Viral Proteins as Emerging Cancer Therapeutics

Simple Summary

This review is focused on enlisting viral proteins from different host sources, irrespective of their origin, that may act as future cancer curatives. Unlike the viral proteins that are responsible for tumor progression, these newly emerged viral proteins function as tumor suppressors. Their ability to regulate various cell signaling mechanisms specifically in cancer cells makes them interesting candidates to explore their use in cancer therapy. The discussion about such viral components may provide new insights into cancer treatment in the absence of any adverse effects to normal cells. The study also highlights avian viral proteins as a substitute to human oncolytic viruses for their ability to evade pre-existing immunity.

Abstract

Viruses are obligatory intracellular parasites that originated millions of years ago. Viral elements cover almost half of the human genome sequence and have evolved as genetic blueprints in humans. They have existed as endosymbionts as they are largely dependent on host cell metabolism. Viral proteins are known to regulate different mechanisms in the host cells by hijacking cellular metabolism to benefit viral replication. Amicable viral proteins, on the other hand, from several viruses can participate in mediating growth retardation of cancer cells based on genetic abnormalities while sparing normal cells. These proteins exert discreet yet converging pathways to regulate events like cell cycle and apoptosis in human cancer cells. This property of viral proteins could be harnessed for their use in cancer therapy. In this review, we discuss viral proteins from different sources as potential anticancer therapeutics.

Cecal Microbiota Modulates Fat Deposition in Muscovy Ducks

Ducks with the same genetic background vary greatly in their adiposity phenotypes. The gut microbiota plays an essential role in host physiological development and metabolism including fat deposition. However, the association of the gut microbiota with the lipogenic phenotype of ducks remains unknown. In this study, we investigated the cecal microbiota of adult Muscovy ducks and the correlation of the cecal microbiota with fat phenotypes. A total of 200 Muscovy ducks were selected from a population of 5,000 Muscovy ducks to record their abdominal fat weight and collect their cecal contents after being slaughtered and defeathered. The cecal contents were subjective to DNA isolation and 16S rRNA gene sequencing. The results were sorted according to the percentage of abdominal fat and the top 20% (n = 40) and the bottom 20% (n = 40) were set as the high and low groups, respectively. Our results indicated that in the cecum of Muscovy ducks, Bacteroidetes, Firmicutes, and Fusobacteria were the predominant phyla while Bacteroides, Oscillospiraceae_uncultured, Parabacteroides, and Bacteroidales_norank were the top 4 dominant genera. Abdominal fat weight (18.57~138.10 g) and percentage of abdominal fat (1.02~27.12%) were significantly correlated (R² = 0.92, P < 0.001). Although the lipogenic phenotypes of ducks had a significant difference (P < 0.05), the α-diversities of the high and low groups were not significantly different (P > 0.05). Nevertheless, after random forest analysis, we identified two genera, Treponema and Ruminococcus_torques_group, that were significantly associated with fat deposition in Muscovy ducks. In addition, the abundances of Treponema and Ruminococcus_torques_group gave a significantly negative and positive association with abdominal fat weight, respectively (P < 0.05). Ducks with a low level of Treponema exhibited a tendency toward a high percentage of abdominal fat (P < 0.01), while the percentage of abdominal fat in ducks with high Ruminococcus_torques_group abundance tended to be higher than that in ducks with low Ruminococcus_torques_group abundance (P < 0.01). These findings could provide the basic data on the cecal microbiota in Muscovy ducks as well as a theoretical foundation to limit the fat deposition by modulating the gut microbiota in the duck industry.

Avian reovirus infection activate the cellular unfold protein response and induced apoptosis via ATF6-dependent mechanism

Avian reovirus (ARV) infection induced apoptosis in vitro and vivo; nevertheless, the intracellular molecular mechanisms have not been sufficiently revealed. In the previous studies, there have been shown that cellular apoptosis caused by ARV were related with GRP78/IRE1/XBP1 pathway. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6) are core molecules in unfold protein response (UPR) and play critical role in ER stress related apoptosis, as well as downstream regulation factors, as Caspase-12 and C/EBP homologous protein (CHOP). In this study, we investigated with a focus on the contribution of UPR related signal pathways in the mechanism of ARV mediated apoptosis. Our results showed that the key molecules of UPR pathways proteins, ATF6, PERK and IRE1 as well as Caspase-12 and cleaved-Caspase-3 expression significant increased both in transcript and protein level in ARV infected cultured Vero cells. In the same time, the ARV induces apoptosis was observed by flow cytometric analysis. Further study revealed that when inhibit the UPR effect by 4PBA pretreated or knockdown of ATF6 by lentivirus mediated shRNA abolished the activation effect of UPR, Caspase-12, cleaved-Caspase-3 activation, as well as the apoptosis induction by ARV infection. The present study provides mechanistic insights into that UPR particular ATF6 played critical roles and works upstream of caspase in the process of cellular apoptosis induced by ARV infection.

Fowl Adenovirus Serotype 4 Influences Arginine Metabolism to Benefit Replication

Hydropericardium syndrome (HPS) is caused by fowl adenovirus serotype 4 (FAdV-4). HPS has caused outbreaks in Chinese populations of broiler chickens since 2015. However, little is known about the molecular mechanisms underlying HPS. In this study, we used transcriptomic analysis to screen differentially expressed genes (DEGs) in the livers of FAdV-4-infected and noninfected chicks. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the gene network associated with the arginine metabolism pathway was enriched in livers infected by FAdV-4; 10 genes were downregulated and 8 genes were upregulated in these livers when compared to noninfected livers. The DEGs identified in livers were reanalyzed by real-time fluorescence quantitative PCR (qPCR); results indicated that the mRNA levels of the DEGs concurred with the data derived from KEGG analysis. Next, we used qPCR to detect the DEGs of the arginine metabolism pathway in a hepatocellular carcinoma cell line (LMH) after infection with FAdV-4 for 24 hr; this also indicated that the mRNA levels of the DEGs concurred with that seen in the liver. We also used si-RNA oligonucleotides to knock down the mRNA levels of iNOS in LMH cells infected with FAdV-4 and found that the viral load of FAdV-4 was increased. Further investigation revealed that the addition of 240 µg/ml of arginine into the culture medium of LMH cells infected with FAdV-4 for 24 hr led to a significant increase in the mRNA levels of iNOS but a significant reduction in the viral load of FAdV-4. Therefore, our data indicated that when broiler chickens become infected with FAdV-4, the arginine metabolic pathway in the liver becomes dysfunctional and the iNOS mRNA level decreases. This will add benefit to the replication of FAdV-4 but can be inhibited by the addition of an appropriate amount of arginine.

Transcriptome Analysis Reveals New Insight of Fowl Adenovirus Serotype 4 Infection

Since 2015, Fowl adenovirus serotype 4 (FAdV-4) infection has caused serious economic losses to the poultry industry worldwide. We isolated and identified the FAdV-4 strain NP, from infected chickens on a layer farm, using chicken embryo allantoic cavity inoculation, electron microscopy, viral genome sequencing, and regression analysis. To explore the pathogenesis of FAdV-4 infection, we conducted transcriptome sequencing analysis of the liver in chickens infected with FAdV-4, using the Illumina® HiSeq 2000 system. Two days after infection with the FAdV-4 NP strain, 13,576 differentially expressed genes (DEGs) were screened in the liver, among which, 7,480 were up-regulated and 6,096 were down-regulated. Gene ontology (GO) analysis indicated that these genes were involved in 52 biological functions. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that those DEGs were involved in 33 pathways. We then focused on the KEGG pathway of phagosome and found that mRNA levels of the 25 DEGs in that pathway were up-regulated, and seven DEGs were down-regulated. Real-time quantitative polymerase chain reaction (qPCR) confirmed the accuracy and reliability of these findings. Moreover, 24 h after LMH cells were infected with FAdV-4, the mRNA levels of F-actin, Rab7, TUBA, and DVnein were significantly increased. These four genes were all subsequently silenced by RNA interference, and viral replication of FAdV-4 was then significantly down-regulated. These findings demonstrate the isolation and identification of the FAdV-4 NP strain, and the DEGs in KEGG pathway of phagosome were utilized by FAdV-4 to benefit its infection.

Cdc20 and molecular chaperone CCT2 and CCT5 are required for the Muscovy duck reovirus p10.8-induced cell cycle arrest and apoptosis

This study demonstrates that the Muscovy duck reovirus (MDRV) p10.8 protein is one of many viral non-structural proteins that induces both cell cycle arrest and apoptosis. The p10.8 but not σC is a nuclear targeting protein that shuttles between the nucleus and the cytoplasm. Our results reveal that p10.8-induced apoptosis in cultured cells occurs by the nucleoporin Tpr/p53-dependent and Fas/caspase 8-mediated pathways. Furthermore, a compelling finding from this study is that the p10.8 and σC proteins of MDRV facilitate CDK2 and CDK4 degradation via the ubiquitin-proteasome pathway. We found that depletion of Cdc20 reversed the p10.8- and σC- mediated CDK4 degradation and p10.8-induced apoptosis, suggesting that Cdc20 plays a critical role in modulating p10.8-mediated cell cycle and apoptosis. Furthermore, we found that depletion of chaperonin-containing tailless complex polypeptide 1 (CCT) 2 and CCT5 reduced the level of Cdc20 and reversed the p10.8- and σC-mediated CDK4 degradation and p10.8-induced apoptosis, indicating that molecular chaperone CCT2 and CCT5 are required for stabilization of Ccd20 for mediating both cell cycle arrest and apoptosis. This study provides mechanistic insights into how p10.8 induces both cell cycle arrest and apoptosis.

The Mechanism of Bufalin-Induced Apoptosis of K562/A02

Background

In clinical practice, many patients become multidrug resistant during chemotherapy, resulting in reduced or no healing effect. Therefore, the present study focused on bufalin, which is extracted from a traditional Chinese medicine named Chan Su (Venenum bufonis). We assessed the effect of bufalin in reversing K562/A02 cell drug resistance and inducing apoptosis, and explored the possible mechanism by which bufalin induces K562/A02 cell apoptosis.

Material/Methods

We used flow cytometry to evaluate intracellular ADM concentration, and RT-PCR and Western blot analysis were used to assess the effect of nuclear factor erythroid-2-related factor 2 (Nrf2) bufalin-related resistance gene expression. We used MTT and flow cytometry to detect apoptosis, and RT-PCR and Western blot were used to detect endoplasmic reticulum stress and apoptosis gene action.

Results

We found that bufalin can increase the concentration of Adriamycin (ADM) in K562/A02 cells by inhibiting the expression of Nrf2 and related drug resistance factors. The results showed that bufalin induced apoptosis of K562/A02 cells by the IRE1α/TRAF2/JNK/caspase-12 pathway.

Conclusions

These results suggest bufalin can reverse drug resistance in K562/A02 cells and that it induces apoptosis of K562/A02 cells by the IRE1α/TRAF2/JNK/caspase-12 pathway.