Esterase D enhances type I interferon signal transduction to suppress foot-and-mouth disease virus replication

Activating Esterase D by PFD5 exerts antiviral effect through inhibiting glutathionization of LAMP1 during Senecavirus A infection

Seneca virus A (SVA) is a newly discovered small nucleic acid virus, which can cause swine blister disease (PVD). Currently, there is no drug or vaccine. Studies have shown that SVA relies on the endolysosomal pathway to accomplish intracellular transport and release, and can disrupt lysosomal homeostasis, but its specific mechanism has not been revealed. At present, there is limited research on vaccines and antiviral drugs for it. Esterase D (ESD), a serine hydrolase, is active against many substrates and plays a role in inhibiting viral replication. However, the specific mechanism of the thioesterase activity of ESD in the signaling pathway is unknown. In this study, we synthesized and screened a novel small-molecule ESD activator, FPD5 (4-chloro-2-(5-phenyl-1-(pyridin-2-yl)-4,5-dihydro- 1h -pyrazol-3-yl)phenyl), capable of inhibiting the replication of SVA. To explore the mechanism of action of this process, we demonstrated the direct interaction between ESD and lysosomal membrane protein-1 (LAMP1) by CO-IP; Western blot revealed that FPD5 could activate ESD and exert a protective effect on LAMP1 and lysosomes. The deglutathionization function of ESD was verified by protein glutathione immunoblotting and detection reagents, and the affected cysteine residues were found by point mutation technique. The results showed that FPD5 activated ESD to exert thioesterase activity, reduced glutathionylation cysteine 375 in the LAMP1 and decreased SVA production. This study provides a theoretical basis for the development of small molecule drugs against SVA, and also suggests that the activation of the thioesterase activity of ESD is a new direction for future antiviral drug development.

miR-361 and miR-34a suppress foot-and-mouth disease virus proliferation by activating immune response signaling in PK-15 cells

Foot-and-mouth disease (FMD) severely impacts cloven-hoofed live-stock production, leading to serious economic losses and international restriction on the trade of animals and animal products worldwide. MiRNAs serve key roles in viral immunity and regulation. However, the knowledge about miRNAs regulation in FMDV infection is still limited. In this study, we found that FMDV infection caused rapid cytopathic in PK-15 cell. To investigate the miRNAs' function in FMDV infection, we performed knockdown of endogenous Dgcr8 using its specific siRNA and found that interference of Dgcr8 inhibited cellular miRNA expression and increased FMDV production, including viral capsid proteins expression, viral genome copies and virus titer, suggesting that miRNAs play an important role in FMDV infection. To obtain a full perspective on miRNA expression profiling after FMDV infection, we performed miRNA sequencing and found that FMDV infection caused inhibition of miRNA expression in PK-15 cells. Together with the target prediction result, miR-34a and miR-361 were screened for further study. Function study showed that no matter plasmid or mimics-mediated overexpression of miR-34a and miR-361 both suppressed FMDV replication, while inhibition of endogenous miR-34a and miR-361 expression using specific inhibitors significantly increased FMDV replication. Further study showed that miR-34a and miR-361 stimulated IFN-β promoter activity and activated interferon-stimulated response element (ISRE). In addition, ELISA test found that miR-361 and miR-34a increased secretion level of IFN-β and IFN-γ, which may contribute to repression of FMDV replication. This study preliminary revealed that miR-361 and miR-34a inhibited FMDV proliferation via stimulating immune response.

FoxJ1 inhibits African swine fever virus replication and viral S273R protein decreases the expression of FoxJ1 to impair its antiviral effect

African swine fever (ASF) is a highly pathogenic swine infectious disease that affects domestic pigs and wild boar, which is caused by the African swine fever virus (ASFV). ASF has caused huge economic losses to the pig industry and seriously threatens global food security and livestock health. To date, there is no safe and effective commercial vaccine against ASF. Unveiling the underlying mechanisms of ASFV-host interplay is critical for developing effective vaccines and drugs against ASFV. In the present study, RNA-sequencing, RT-qPCR and Western blotting analysis revealed that the transcriptional and protein levels of the host factor FoxJ1 were significantly down-regulated in primary porcine alveolar macrophages (PAMs) infected by ASFV. RT-qPCR analysis showed that overexpression of FoxJ1 upregulated the transcription of type I interferon and interferon stimulating genes (ISGs) induced by poly(dA:dT). FoxJ1 revealed a function to positively regulate innate immune response, therefore, suppressing the replication of ASFV. In addition, Western blotting analysis indicated that FoxJ1 degraded ASFV MGF505-2R and E165R proteins through autophagy pathway. Meanwhile, RT-qPCR and Western blotting analysis showed that ASFV S273R inhibited the expression of FoxJ1. Altogether, we determined that FoxJ1 plays an antiviral role against ASFV replication, and ASFV protein impairs FoxJ1-mediated antiviral effect by degradation of FoxJ1. Our findings provide new insights into the antiviral function of FoxJ1, which might help design antiviral drugs or vaccines against ASFV infection.

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FoxJ1 inhibits ASFV replication by degrading ASFV MGF505-2R and E165R proteins via autophagy.

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FoxJ1 enhances type I IFN response, showing an essential antiviral role.

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ASFV S273R protein inhibits FoxJ1 expression to impair its antiviral effect.

Activation of Esterase D by FPD5 Inhibits Growth of A549 Lung Cancer Cells via JAB1/p53 Pathway

Esterase D (ESD) is widely distributed in mammals, and it plays an important role in drug metabolism, detoxification, and biomarkers and is closely related to the development of tumors. In our previous work, we found that a chemical small-molecule fluorescent pyrazoline derivative, FPD5, an ESD activator, could inhibit tumor growth by activating ESD, but its molecular mechanism is still unclear. Here, by using RNA interference (RNAi), andco-immunoprecipitation techniques, we found that ESD suppressed the nucleus exportation of p53 through reducing the interaction between p53 and JAB1. The protein level of p53 in the nucleus was upregulated and the downstream targets of p53 were found by Human Gene Expression Array. p53 inhibited the expression of CDCA8 and CDC20. Lastly, the cell cycle of A549 cells was arrested at the G0/G1 phase. Together, our data suggest that ESD inhibited the cancer cell growth by arresting the cell cycle of A549 cells via the JAB1/p53 signaling pathway. Our findings provide a new insight into how to inhibit the growth of lung cancer with the activation of ESD by FPD5.

Development of an esterase fluorescent probe based on naphthalimide-benzothiazole conjugation and its applications for qualitative detection of esterase in orlistat-treated biosamples

Esterase is a large hydrolysis family, and widely distributed in many kinds of cells. It is responsible for multiple physiological and pathological functions including metabolism, gene expression. While abnormality of esterase is associated with many pathological activities in obesity, Wolman's disease, and cancer. Thereby, it is essential to design an effective tool for esterase in situ detection in biological systems. Herein, a novel fluorescent probe Y-1 for monitoring esterase in living cells was rationally designed. Probe Y-1 was synthesized by the conjugation between an acetylation of 4-hydroxy naphthalimide and benzothiazole group. Benzothiazole moiety is a typical Excited-state intramolecular proton transfer (ESIPT) controller. Acetate group was selected as the responsive site and ESIPT initiator. As the acetate group could block the ESIPT effect, the probe emits no fluorescence under the excitation of 455 nm. When binding with esterase, Y-1 shows distinct fluorescence with the peak at 560 nm with short time when ESIPT is on. Y-1 displays high sensitivity (LOD is 0.216 × 10^-3 U/mL), fast response (within 5 min), high selectivity and photostability towards esterase. Furthermore, the %RSD (relative standard deviation) of within-day and day-to-day precision was no more than 13.0% and the accuracy ranged from -6.5 to -12.3%. Kinetics performance of Y-1 indicates that esterase has high affinity and hydrolysis to Y-1. For biological applications, our probe is a time-dependent visualizing esterase in living HepG2 and CoLo205 cells within 15 min. After the treatment of orlistat (1 and 5 μM) for inhibiting the activity of esterase, the bright fluorescence has also been detected using our probe. Furthermore, it has been successful in monitoring the esterase in zebrafish, the data were consistent with cellular phenomena. Therefore, all these findings indicate that the robust probe Y-1 is a useful qualitative tool for detecting esterase in biological systems.

Esterase D stabilizes FKBP25 to suppress mTORC1

Background

Esterase D (ESD) is a nonspecific esterase that detoxifies formaldehyde. Many reports have stated that ESD activity is associated with a variety of physiological and pathological processes. However, the detailed signaling pathway of ESD remains poorly understood.

Methods

Considering the advantages of the small chemical molecule, our recent work demonstrated that 4-chloro-2-(5-phenyl-1-(pyridin-2-yl)-4,5-dihydro-1H-pyrazol-3-yl) phenol (FPD5) activates ESD, and will be a good tool for studying ESD further. Firstly, we determined the interaction between ESD and FK506 binding protein 25 (FKBP25) by yeast two-hybrid assay and co-immunoprecipitation (CO-IP) and analyzed the phosphorylation levels of mTORC1, P70S6K and 4EBP1 by western blot. Furthermore, we used the sulforhodamine B (SRB) and chick chorioallantoic membrane (CAM) assay to analyze cell viability in vitro and in vivo after treatment with ESD activator FPD5.

Results

We screened FKBP25 as a candidate protein to interact with ESD by yeast two-hybrid assay. Then we verified the interaction between ESD and endogenous FKBP25 or ectopically expressed GFP-FKBP25 by CO-IP. Moreover, the N-terminus (1–90 aa) domain of FKBP25 served as the crucial element for their interaction. More importantly, ESD reduced the K48-linked poly-ubiquitin chains of FKBP25 and thus stabilized cytoplasmic FKBP25. ESD also promoted FKBP25 to bind more mTORC1, suppressing the activity of mTORC1. In addition, ESD suppressed tumor cell growth in vitro and in vivo through autophagy.

Conclusions

These findings provide novel evidence for elucidating the molecular mechanism of ESD and ubiquitination of FKBP25 to regulate autophagy and cancer cell growth. The ESD/FKBP25/mTORC1 signaling pathway is involved in inhibiting tumor cell growth via regulating autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-021-00297-2.

Virus-Host Interactions in Foot-and-Mouth Disease Virus Infection

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals, which has been regarded as a persistent challenge for the livestock industry in many countries. Foot-and-mouth disease virus (FMDV) is the etiological agent of FMD that can spread rapidly by direct and indirect transmission. FMDV is internalized into host cell by the interaction between FMDV capsid proteins and cellular receptors. When the virus invades into the cells, the host antiviral system is quickly activated to suppress the replication of the virus and remove the virus. To retain fitness and host adaptation, various viruses have evolved multiple elegant strategies to manipulate host machine and circumvent the host antiviral responses. Therefore, identification of virus-host interactions is critical for understanding the host defense against virus infections and the pathogenesis of the viral infectious diseases. This review elaborates on the virus-host interactions during FMDV infection to summarize the pathogenic mechanisms of FMD, and we hope it can provide insights for designing effective vaccines or drugs to prevent and control the spread of FMD and other diseases caused by picornaviruses.

Innate immune evasion by picornaviruses

The family Picornaviridae comprises a large number of viruses that cause disease in broad spectrum of hosts, which have posed serious public health concerns worldwide and led to significant economic burden. A comprehensive understanding of the virus-host interactions during picornavirus infections will help to prevent and cure these diseases. Upon picornavirus infection, host pathogen recognition receptors (PRRs) sense viral RNA to activate host innate immune responses. The activated PRRs initiate signal transduction through a series of adaptor proteins, which leads to activation of several kinases and transcription factors, and contributes to the consequent expression of interferons (IFNs), IFN-inducible antiviral genes, as well as various inflammatory cytokines and chemokines. In contrast, to maintain viral replication and spread, picornaviruses have evolved several elegant strategies to block innate immune signaling and hinder host antiviral response. In this review, we will summarize the recent progress of how the members of family Picornaviridae counteract host immune response through evasion of PRRs detection, blocking activation of adaptor molecules and kinases, disrupting transcription factors, as well as counteraction of antiviral restriction factors. Such knowledge of immune evasion will help us better understand the pathogenesis of picornaviruses, and provide insights into developing antiviral strategies and improvement of vaccines.

Physiological effects of gamma irradiation in the honeybee, Apis mellifera

Terrestrial ecosystems are exposed to various kinds of pollutants, including radionuclides. The honeybee, Apis mellifera, is commonly used in ecotoxicology as a model species for evaluating the effects of pollutants. In the present study, honeybees were irradiated right after birth for 14 days with gamma rays at dose rates ranging between 4.38 × 10^-3 and 588 mGy/d. Biological tissues (head, intestine and abdomen) were sampled at D3, D10 and D14. Ten different physiological markers involved in nervous (acetylcholinesterase (AChE)), antioxidative (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)), immune system (phenoloxidase (PO)) and metabolism (carboxylesterases (CaEs) and alkaline phosphatase (ALP)) were measured. Univariate analyses were conducted to determine whether each individual biomarker response was positively or negatively correlated with the dose rate. Then, multivariate analyses were applied to investigate the relationships between all the biomarker responses. Although no mortality occurred during the experiment, several biomarkers varied significantly in relation to the dose rate. Globally, the biomarkers of antioxidant and immune systems decreased as the dose rate increased. Reversible effects on the indicator of the neural system were found. Concerning indicators of metabolism (carboxylesterases), variations occurred but no clear pattern was found. Taken altogether, these results help better understand the effects of ionizing radiation on bees by identifying relevant physiological markers of effects. These results could improve the assessment of the environmental risk due to ionizing radiation in terrestrial ecosystems.

Enhanced Replication of Mouse Adenovirus Type 1 following Virus-Induced Degradation of Protein Kinase R (PKR)

The first line of defense in cells during viral infection is the innate immune system, which is activated by different viral products. PKR is a part of this innate immune system and is induced by interferon and activated by dsRNA produced by DNA and RNA viruses. PKR is such an important part of the antiviral response that many viral families have gene products to counteract its activation or the resulting effects of its activity. Although a few RNA viruses degrade PKR, this method of counteracting PKR has not been reported for any DNA viruses. MAV-1 does not encode virus-associated RNAs, a human adenoviral defense against PKR activation. Instead, MAV-1 degrades PKR, and it is the first DNA virus reported to do so. The innate immune evasion by PKR degradation is a previously unidentified way for a DNA virus to circumvent the host antiviral response.

Protein kinase R (PKR) plays a major role in activating host immunity during infection by sensing double-stranded RNA (dsRNA) produced by viruses. Once activated by dsRNA, PKR phosphorylates the translation factor eukaryotic initiation factor 2α (eIF2α), halting cellular translation. Many viruses have methods of inhibiting PKR activation or its downstream effects, circumventing protein synthesis shutdown. These include sequestering dsRNA or producing proteins that bind to and inhibit PKR activation. Here we describe our finding that in multiple cell types, PKR was depleted during mouse adenovirus type 1 (MAV-1) infection. MAV-1 did not appear to be targeting PKR at the transcriptional or translational level, because total PKR mRNA levels and levels of PKR mRNA bound to polysomes were unchanged or increased during MAV-1 infection. However, inhibiting the proteasome reduced the PKR depletion seen in MAV-1-infected cells, whereas inhibiting the lysosome had no effect. This suggests that proteasomal degradation alone is responsible for PKR degradation during MAV-1 infection. Time course experiments indicated that the degradation occurs early after infection. Infecting cells with UV-inactivated virus prevented PKR degradation, whereas inhibiting viral DNA replication did not. Together, these results suggest that an early viral gene is responsible. Degradation of PKR is a rare mechanism to oppose PKR activity, and it has been described in only six RNA viruses. To our knowledge, this is the first example of a DNA virus counteracting PKR by degrading it.

RIG-I is responsible for activation of type I interferon pathway in Seneca Valley virus-infected porcine cells to suppress viral replication

Background

Retinoic acid-inducible gene I (RIG-I) is a key cytosolic receptor of the innate immune system. Seneca valley virus (SVV) is a newly emerging RNA virus that infects pigs causing significant economic losses in pig industry. RIG-I plays different roles during different viruses infections. The role of RIG-I in SVV-infected cells remains unknown. Understanding of the role of RIG-I during SVV infection will help to clarify the infection process of SVV in the infected cells.

Methods

In this study, we generated a RIG-I knockout (KO) porcine kidney PK-15 cell line using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) genome editing tool. The RIG-I gene sequence of RIG-I KO cells were determined by Sanger sequencing method, and the expression of RIG-I protein in the RIG-I KO cells were detected by Western bloting. The activation status of type I interferon pathway in Sendai virus (SeV)- or SVV-infected RIG-I KO cells was investigated by measuring the mRNA expression levels of interferon (IFN)-β and IFN-stimulated genes (ISGs). The replicative state of SVV in the RIG-I KO cells was evaluated by qPCR, Western bloting, TCID₅₀ assay and indirect immunofluorescence assay.

Results

Gene editing of RIG-I in PK-15 cells successfully resulted in the destruction of RIG-I expression. RIG-I KO PK-15 cells had a lower expression of IFN-β and ISGs compared with wildtype (WT) PK-15 cells when stimulated by the model RNA virus SeV. The amounts of viral RNA and viral protein as well as viral yields in SVV-infected RIG-I WT and KO cells were determined and compared, which showed that knockout of RIG-I significantly increased SVV replication and propagation. Meanwhile, the expression of IFN-β and ISGs were considerably decreased in RIG-I KO cells compared with that in RIG-I WT cells during SVV infection.

Conclusion

Altogether, this study indicated that RIG-I showed an antiviral role against SVV and was essential for activation of type I IFN signaling during SVV infection. In addition, this study suggested that the CRISPR/Cas9 system can be used as an effective tool to modify cell lines to increase viral yields during SVV vaccine development.

Early Growth Response Gene-1 Suppresses Foot-and-Mouth Disease Virus Replication by Enhancing Type I Interferon Pathway Signal Transduction

Early growth response gene-1 (EGR1) is a multifunctional transcription factor that is implicated in viral infection. In this study, we observed that foot-and-mouth disease virus (FMDV) infection significantly triggered EGR1 expression. Overexpression of EGR1 suppressed FMDV replication in porcine cells, and knockdown of EGR1 considerably promoted FMDV replication. A previously reported FMDV mutant virus (with two amino acids mutations in SAP domain) that displays a strong type I interferon (IFN) induction activity was used in this study. We found that SAP mutant FMDV infection induced a higher expression of EGR1 than wildtype FMDV infection, and also triggered higher IFN-β and IFN-stimulated genes (ISGs) expression than wildtype FMDV infection. This implied a link between EGR1 and type I IFN signaling. Further study showed that overexpression of EGR1 resulted in Sendai virus (SeV)-induced IFN-stimulated response element (ISRE) and NF-κB promoter activation. In addition, the SeV-induced ISGs expression was impaired in EGR1 knockdown cells. EGR1 upregulation promoted type I IFN signaling activation and suppressed FMDV and Seneca Valley virus replication. Suppression of the transcriptional activity of EGR1 did not affect its antiviral effect against FMDV. This study reveals a new mechanism evolved by EGR1 to enhance type I IFN signaling and suppress FMDV replication.

Foot-and-mouth disease virus induces lysosomal degradation of host protein kinase PKR by 3C proteinase to facilitate virus replication

The interferon-induced double-strand RNA activated protein kinase (PKR) plays important roles in host defense against viral infection. Here we demonstrate the significant antiviral role of PKR against foot-and-mouth disease virus (FMDV) and report that FMDV infection inhibits PKR expression and activation in porcine kidney (PK-15) cells. The viral nonstructural protein 3C proteinase (3Cpro) is identified to be responsible for this inhibition. However, it is independent of the well-known proteinase activity of 3Cpro or 3Cpro-induced shutoff of host protein synthesis. We show that 3Cpro induces PKR degradation by lysosomal pathway and no interaction is determined between 3Cpro and PKR. Together, our results indicate that PKR acts an important antiviral factor during FMDV infection, and FMDV has evolved a strategy to overcome PKR-mediated antiviral role by downregulation of PKR protein.