Phospho-eIF4E stimulation regulates coronavirus entry by selective expression of cell membrane-residential factors.

The eukaryotic translation initiation factor eIF4E can regulate cellular translation via phosphorylation on serine 209. In a recent study, by two rounds of TMT relative quantitative proteomics, we found that phosphorylated eIF4E (p-eIF4E) favors the translation of selected mRNAs, and the encoded proteins are mainly involved in ECM-receptor, focal adhesion, and PI3K-Akt signaling. The current paper is focused on the relationship between p-eIF4E and the downstream host cell proteins, and their presumed effect on efficient entry of PEDV. We found that the depletion of membrane-residential factor TSPAN3, CD63, and ITGB2 significantly inhibited viral invasion of PEDV, and reduced the entry of pseudotyped particles PEDV-pp, SARS-CoV-pp, and SARS-CoV-2-pp. The specific antibodies of TSPAN3, CD63, and ITGB2 blocked the adsorption of PEDV into host cells. Moreover, we detected that eIF4E phosphorylation was increased at 1 h after PEDV infection, in accordance with the expression of TSPAN3, CD63, and ITGB2. Similar trends appeared in the intestines of piglets in the early stage of PEDV challenge. Compared with Vero cells, S209A-Vero cells in which eIF4E cannot be phosphorylated showed a decrease of invading PEDV virions. MNK kinase inhibitor blocked PEDV invasion, as well as reduced the accumulation of TSPAN3, CD63, and ITGB2. Further study showed that the ERK-MNK pathway was responsible for the regulation of PEDV-induced early phosphorylation of eIF4E. This paper demonstrates for the first time the connections among p-eIF4E stimulation and membrane-residential host factors. Our findings also enrich the understanding of the biological function of phosphorylated eIF4E during the viral life cycle.IMPORTANCEThe eukaryotic translation initiation factor eIF4E can regulate cellular translation via phosphorylation. In our previous study, several host factors susceptible to a high level of p-eIF4E were found to be conducive to viral infection by coronavirus PEDV. The current paper is focused on cell membrane-residential factors, which are involved in signal pathways that are sensitive to phosphorylated eIF4E. We found that the ERK-MNK pathway was activated, which resulted in the stimulation of phosphorylation of eIF4E in early PEDV infection. Phospho-eIF4E promoted the viral invasion of PEDV by upregulating the expression of host factors TSPAN3, CD63, and ITGB2 at the translation level rather than at the transcription level. Moreover, TSPAN3, CD63, or ITGB2 facilitates the efficient entry of coronavirus SARS-CoV, SARS-CoV-2, and HCoV-OC43. Our findings broaden our insights into the dynamic phosphorylation of eIF4E during the viral life cycle, and provide further evidence that phosphorylated eIF4E regulates selective translation of host mRNA.

Proteomic screening identifies RPLp2 as a specific regulator for the translation of coronavirus.

Viral mRNA of coronavirus translates in an eIF4E-dependent manner, and the phosphorylation of eIF4E can modulate this process, but the role of p-eIF4E in coronavirus infection is not yet entirely evident. p-eIF4E favors the translation of selected mRNAs, specifically the mRNAs that encode proteins associated with cell proliferation, inflammation, the extracellular matrix, and tumor formation and metastasis. In the present work, two rounds of TMT relative quantitative proteomics were used to screen 77 cellular factors that are upregulated upon infection by coronavirus PEDV and are potentially susceptible to a high level of p-eIF4E. PEDV infection increased the translation level of ribosomal protein lateral stalk subunit RPLp2 (but not subunit RPLp0/1) in a p-eIF4E-dependent manner. The bicistronic dual-reporter assay and polysome profile showed that RPLp2 is essential for translating the viral mRNA of PEDV. RNA binding protein and immunoprecipitation assay showed that RPLp2 interacted with PEDV 5'UTR via association with eIF4E. Moreover, the cap pull-down assay showed that the viral nucleocapsid protein is recruited in m7GTP-precipitated complexes with the assistance of RPLp2. The heterogeneous ribosomes, which are different in composition, regulate the selective translation of specific mRNAs. Our study proves that viral mRNA and protein utilize translation factors and heterogeneous ribosomes for preferential translation initiation. This previously uncharacterized process may be involved in the selective translation of coronavirus.

Death Receptor DR5 as a Proviral Factor for Viral Entry and Replication of Coronavirus PEDV.

Porcine epidemic diarrhea virus (PEDV), a member of Coronaviridae, causes high mortality in newborn piglets, and has caused significant economic losses in the pig industry. PEDV infection can induce apoptosis, both caspase-dependent and caspase-independent, but the details of apoptosis remain clarified. This study investigated the effect of death receptor DR5 on PEDV infection and its relationship with PEDV-induced apoptosis. We found that DR5 knockdown reduced viral mRNA and protein levels of PEDV, and the viral titer decreased from 104.5 TCID50 to 103.4 TCID50 at 12 hpi. Overexpression of DR5 significantly increased the viral titer. Further studies showed that DR5 facilitates viral replication by regulating caspase-8-dependent apoptosis, and the knockdown of DR5 significantly reduced PEDV-induced apoptosis. Interestingly, we detected a biphasic upregulation expression of DR5 in both Vero cells and piglets in response to PEDV infection. We found that DR5 also facilitates viral entry of PEDV, especially, incubation with DR5 antibody can reduce the PEDV binding to Vero cells. Our study improves the understanding of the mechanism by which PEDV induces apoptosis and provides new insights into the biological function of DR5 in PEDV infection.

Small-Molecule RAF265 as an Antiviral Therapy Acts against PEDV Infection.

Porcine epidemic diarrhea virus (PEDV), a member of the family Coronaviridae, causes acute diarrhea, vomiting, dehydration, and high mortality in newborn piglets, and has caused significant economic losses in the pig industry. There are currently no specific drugs available to treat PEDV. Viruses depend exclusively on the cellular machinery to ensure an efficient replication cycle. In the present study, we found that small-molecule RAF265, an anticancer drug that has been shown to be a potent inhibitor of RAF, reduced viral loads of PEDV by 4 orders of magnitude in Vero cells, and protected piglets from virus challenge. RAF265 reduced PEDV production by mediating cytoskeleton arrangement and targeting the host cell's translation machinery. Treatment with RAF265 inhibited viral entry of PEDV S-glycoprotein pseudotyped viral vector particle (PEDV-pp), at half maximal effective concentrations (EC50) of 79.1 nM. RAF265 also presented potent inhibitory activity against viral infection by SARS-CoV-2-pp and SARS-CoV-pp. The present work may provide a starting point for further progress toward the development of antiviral strategies effective against coronavirus PEDV.

Regulation of Tripartite Motif-Containing Proteins on Immune Response and Viral Evasion.

Tripartite motif-containing proteins (TRIMs), exhibiting ubiquitin E3 ligase activity, are involved in regulation of not only autophagy and apoptosis but also pyrotosis and antiviral immune responses of host cells. TRIMs play important roles in modulating signaling pathways of antiviral immune responses via type I interferon, NF-κB, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and Nrf2. However, viruses are able to antagonize TRIM activity or evenly utilize TRIMs for viral replication. This communication presents the current understanding of TRIMs exploited by viruses to evade host immune response.

Development of a real-time recombinase-aided amplification (RT-RAA) molecular diagnosis assay for sensitive and rapid detection of Toxoplasma gondii.

Toxoplasma gondii, a protozoan intracellular parasite, is present in a wide range of hosts, including virtually all species of warm-blooded vertebrates. Toxoplasmosis spreads to humans through a variety of pathways, including contaminated food or water, and close contact with various types of domestic animals. It poses a severe threat to human health, and contributes to important economic losses, not only in cost-of-illness but also in surveillance programs. It is thus necessary to develop a rapid point-of-care field diagnostic technology to control or prevent pathogen transmission to economically important livestock animals, domestic animals, and human beings. In this study, we develop a real-time isothermal amplification method capable of detecting the T. gondii genome in swine and feline blood samples. This method can detect toxoplasma genome with a lowest detection limit of 102 copies of per reaction under optimal reaction conditions of 36 °C for 25 min. The assay displayed advantages in sensitivity and specificity in comparison to traditional real-time PCR, and can be performed in a portable instrument.

CUL1 Knockdown Attenuates the Adhesion, Invasion, and Migration of Triple-Negative Breast Cancer Cells via Inhibition of Epithelial-Mesenchymal Transition.

Cullin-1 (CUL1) is an important factor for tumor growth and a potential therapeutic target for breast cancer therapy, but the molecular mechanism in triple-negative breast cancer (TNBC) is unknown. In the present study, CUL1 shRNA was transfected into BT549 and MDA-MB-231 breast cancer cells. Cell morphology, adhesion, invasion, and migration assays were carried out in the CUL1 knockdown cells. Additionally, protein expression levels of epithelial-mesenchymal transition (EMT)-related factors, Akt phosphorylation at S473 (pAkt), glycogen synthase kinase-3ß phosphorylation at ser9 (pGSK3ß), cytoplasmic and nuclear ß-catenin, and epidermal growth factor receptor phosphorylation at Tyr1068 (pEGFR) were detected by Western blot analysis. CUL1 knockdown significantly suppressed the adhesion, invasion and migration capabilities of the cells, and decreased the expression of Snail1/2, ZEB1/2, Twist1/2, Vimentin, and increased the expression of Cytokeratin 18 (CK18). Moreover, CUL1 knockdown significantly downregulated the phosphorylated levels of Akt, GSK3ß, and EGFR, inhibiting the translocation of ß-catenin from the cytoplasm to the nucleus. The results indicate that CUL1 knockdown prohibited the metastasis behaviors of breast cancer cells through downregulation (dephosphorylation) of the EMT signaling pathways of EGFR and Akt/GSK3ß/ß-catenin in breast cancer. These results strongly suggested that reinforcement of the EMT might be a key for CUL1 to accelerate TNBC metastasis.

An IncX1 plasmid isolated from Salmonella enterica subsp. enterica serovar Pullorum carrying blaTEM-1B, sul2, arsenic resistant operons.

We have identified an IncX1 plasmid named pQJDSal1 from Salmonella enterica subsp. enterica serovar Pullorum (S. Pullorum). The plasmid is 67,685 bp in size and has 72 putative genes. pQJDSal1 harbors a conserved IncX1-type backbone with predicted regions for conjugation, replication and partitioning, as well as a toxin/antitoxin plasmid addiction system. Two regions (A and B) that have not been previously reported in IncX1 plasmids are inserted into the backbone. Region A (10.7 kb), inserted between parA and taxD, consists of a new Tn6168-like transposon containing an arsenic resistant operon arsB2CHR and sulfonamide resistance gene sul2. Region B contains another arsenic resistant operon arsADHR, resistance gene blaTEM-1B and three transposable elements. Conjugation experiments showed that pQJDSal1 could transfer from S. Pullorum to Escherichia coli (E. coli) J53. Statistical analysis of 70 sequenced IncX1 plasmids revealed that IncX1 plasmids harbored various antibiotic resistance genes. The results highlight the importance of IncX1 plasmids in disseminating antibiotic resistance genes.

Tn6450, a Novel Multidrug Resistance Transposon Characterized in a Proteus mirabilis Isolate from Chicken in China.

A novel 65.8-kb multidrug resistance transposon, designated Tn6450, was characterized in a Proteus mirabilis isolate from chicken in China. Tn6450 contains 18 different antimicrobial resistance genes, including cephalosporinase gene blaDHA-1 and fluoroquinolone resistance genes qnrA1 and aac(6')-Ib-cr It carries a class 1/2 hybrid integron composed of intI2 and a 3' conserved segment of the class 1 integron. Tn6450 is derived from Tn7 via acquisition of new mobile elements and resistance genes.

Duodenal-jejunal exclusion improves insulin resistance in type 2 diabetic rats by upregulating the hepatic insulin signaling pathway.

OBJECTIVES: Previous studies have shown duodenal-jejunal exclusion (DJE) results in the rapid resolution of type 2 diabetes; however, the underlying mechanism is unknown. This study aimed to measure the hepatic expression of insulin receptor substrate-2 (IRS-2) and glucose transporter-2 (GLUT-2) in type 2 diabetic rats post-DJE, and to investigate their roles in improved hepatic insulin resistance and glucose intolerance. METHODS: Type 2 diabetic Sprague-Dawley (SD) rats were randomly divided into DJE operation (DO) and control (DC) groups. Normal SD rats were also divided into DJE operation and control groups. Fasting plasma glucose and insulin concentrations were measured, and the quantitative insulin sensitivity check index (QUICKI) and Homeostasis Model Assessment Insulin Resistance (HOMA-IR) were calculated. Eight weeks postoperation, the hepatic IRS-2 and GLUT-2 protein and mRNA levels were measured using western blotting and reverse transcription polymerase chain reaction, respectively. RESULTS: The fasting blood glucose in the DO group decreased from a preoperative level of 20.21 ± 2.14 mmol/L to 8.50 ± 2.19 mmol/L (P < 0.05) 8 wk post-DJE. A change in the QUICKI revealed a dramatic increase, and HOMA-IR showed a significant decrease in the DO group (P < 0.05). Additionally, the IRS-2 and GLUT-2 protein and mRNA levels at 8 wk postoperation were significantly increased in the DO group compared with the DC group. CONCLUSIONS: DJE led to upregulated hepatic IRS-2 and GLUT-2 expression in the hepatic insulin signaling pathway and improved insulin sensitivity in type 2 diabetic rats.

Expression of HBx protein in hepatitis B virus-infected intrahepatic cholangiocarcinoma.

BACKGROUND: Hepatitis B virus (HBV) is an etiological factor of intrahepatic cholangiocarcinoma (ICC), but the pathogenic mechanisms remain unclear. This study aimed to investigate the expression and possible role of HBx, an HBV-encoded potentially oncogenic protein, in HBV-infected ICC. METHODS: Tissue samples were obtained from 54 specimens of HBV-infected ICC. Forty-four specimens were of peripheral type and 10 hilar type. Formalin-fixed, paraffin-embedded sections of the specimens were immunohistochemically stained for HBx and p53. RESULTS: HBx expression was found in 70.4% (38/54) of the specimens, and it was more frequently seen in the peripheral type than in the hilar type (79.5% vs 30.0%, P=0.002). All three well-differentiated ICCs expressed HBx, whereas 76.9% (30/39) moderately-differentiated and 41.7% (5/12) poorly-differentiated ICCs had HBx expression (P=0.033). Patients with HBx expression had a significantly higher prevalence of elevated serum alpha-fetoprotein (P=0.033). p53 protein expression was found in 18 of 54 cases (33.3%), and was not correlated with that of HBx. CONCLUSIONS: HBx may contribute to the pathogenesis of ICC, particularly the peripheral type. p53 abnormality may not play a significant role in HBx-mediated oncogenicity during ICC carcinogenesis.

[Association of p53 codon 72 polymorphism with genetic susceptibility to hepatocellular carcinoma in Chinese population].

OBJECTIVE: A functional single nucleotide polymorphism (SNP) at codon 72 of the gene for p53 protein (p53 R72P) has been implicated in a variety of human cancers, but the relationship between this SNP and hepatocellular carcinoma (HCC) remains obscure despite the fact that the critical role of p53 protein in HCC has been documented. This study was conducted to evaluate the link between the polymorphism with HCC stratified by chronic hepatitis B infection status in a Chinese population. METHODS: Four hundred and sixty-nine HCC cases (359 HbsAg-positive, 110 HbsAg-negative) and 567 controls (137 HbsAg-positive, 430 HbsAg-negative) were studied. The p53 genotypes were determined by a PCR based restriction fragment length polymorphism (RFLP) method. RESULTS: Overall, no correlation between HCC and the R72P genotypes was found when comparing all cases to controls or when comparing the HbsAg-positive HCC subgroup to controls. However, in HbsAg-negative subjects, the 72P allele was significantly associated with the presence of HCC (P=0.01) and had a higher risk (OR=1.69, 95% CI: 1.25-2.27) of HCC as compared to the 72R allele. By comparison to R/R homozygotes, the R/P heterozygotes and P/P homozygotes had a 1.73-fold (95% CI: 0.96-3.11) and a 3.29-fold (95% CI: 1.58-6.86) increased risk for HCC, respectively. The subjects with the 72P allele and a family history of HCC and those with the 72P allele and male gender also yielded an 11.14-fold (95% CI: 1.62-76.67) and a 9.39 fold (95% CI: 3.08-28.62) increased risk of HCC, respectively. CONCLUSION: The P allele of the p53 R72P polymorphism has an increased risk for HCC in HbsAg-negative subjects, and exerts a synergistic influence on the risk for HCC when combined with HCC family history and the male gender.