Epstein-Barr virus Latent Membrane Protein 2A (LMP2A)-mediated changes in Fas expression and Fas-dependent apoptosis: Role of Lyn/Syk activation

Pathogenesis and therapeutic implications of EBV-associated epithelial cancers

Epstein-Barr virus (EBV), one of the most common human viruses, has been associated with both lymphoid and epithelial cancers. Undifferentiated nasopharyngeal carcinoma (NPC), EBV associated gastric cancer (EBVaGC) and lymphoepithelioma-like carcinoma (LELC) are amongst the few common epithelial cancers that EBV has been associated with. The pathogenesis of EBV-associated NPC has been well described, however, the same cannot be said for primary pulmonary LELC (PPLELC) owing to the rarity of the cancer. In this review, we outline the pathogenesis of EBV-associated NPC and EBVaGCs and their recent advances. By drawing on similarities between NPC and PPLELC, we then also postulated the pathogenesis of PPLELC. A deeper understanding about the pathogenesis of EBV enables us to postulate the pathogenesis of other EBV associated cancers such as PPLELC.

The impact of Epstein-Barr virus latent membrane protein 2A on the production of B cell activating factor of the tumor necrosis factor family (BAFF), APRIL and their receptors

Introduction

Epstein‐Barr virus (EBV) establishes a lifelong infection in human B cells where the virus consistently expresses Latent Membrane Protein 2A (LMP2A) to promote B cell survival. A prior study indicates that LMP2A may increase the production of the pro‐survival factor, B cell Activating Factor of the tumor necrosis factor family (BAFF), which could also indirectly increase B cell survival. The current study sought to extend these findings and determine if LMP2A increased BAFF production and/or the responsiveness of LMP2A‐expressing cells to this cytokine.

Methods

Four independently derived LMP2A‐negative and ‐positive B cell lymphoma cell lines were analyzed for BAFF and APRIL levels by both ELISA and Western Blot analysis. Additionally, flow cytometric analysis measured any LMP2A‐dependent changes in the receptors for BAFF and APRIL (BAFF‐R, transmembrane activator and calcium‐modulator and cyclophilin ligand interactor [TACI], B cell maturation antigen [BCMA]) in both LMP2A‐negative and ‐positive B cell lymphoma cell lines.

Results

In contrast to previous reports, our data indicate that LMP2A does not increase the expression of BAFF or APRIL by Western blot analysis or ELISA. Additionally, flow cytometric analysis indicates that LMP2A does not influence the expression of the receptors for BAFF and APRIL: TACI, BAFF‐R, and BCMA.

Conclusion

Therefore, these data suggest that while EBV utilizes other latency proteins to regulate BAFF production, EBV does not appear to use LMP2A to enhance BAFF‐or APRIL‐dependent survival to promote EBV latency.

Viral-mediated activation and inhibition of programmed cell death

Viruses are ubiquitous intracellular genetic parasites that heavily rely on the infected cell to complete their replication life cycle. This dependency on the host machinery forces viruses to modulate a variety of cellular processes including cell survival and cell death. Viruses are known to activate and block almost all types of programmed cell death (PCD) known so far. Modulating PCD in infected hosts has a variety of direct and indirect effects on viral pathogenesis and antiviral immunity. The mechanisms leading to apoptosis following virus infection is widely studied, but several modalities of PCD, including necroptosis, pyroptosis, ferroptosis, and paraptosis, are relatively understudied. In this review, we cover the mechanisms by which viruses activate and inhibit PCDs and suggest perspectives on how these affect viral pathogenesis and immunity.

Molecular Interactions between Two LMP2A PY Motifs of EBV and WW Domains of E3 Ubiquitin Ligase AIP4

Interactions involving Epstein–Barr virus (EBV) LMP2A and Nedd4 family E3 ubiquitin–protein ligases promote the ubiquitination of LMP2A-associated proteins, which results in the perturbation of normal B-cell signaling. Here, we solved the solution structure of the WW2 domain of hAIP4 and investigated the binding mode involving the N-terminal domain of LMP2A and the WW2 domain. The WW2 domain presented a conserved WW domain scaffold with a three-stranded anti-parallel β-sheet and bound two PY motifs via different binding mechanisms. Our NMR titration and ITC data demonstrated that the PY motifs of LMP2A can recognize and interact weakly with the XP groove of the WW2 domain (residues located around the third β-strand), and then residues between two PY motifs optimize the binding by interacting with the loop 1 region of the WW2 domain. In particular, the residue Val15 in the hairpin loop region between β1 and β2 of the WW2 domain exhibited unique changes depending on the terminal residues of the PY motif. This result suggested that the hairpin loop is responsible for additional interactions outside the XP groove, and this hypothesis was confirmed in a deuterium exchange experiment. These weak but wide interactions can stabilize the complex formed between the PY and WW domains.

RNA m6 A methylation regulates virus-host interaction and EBNA2 expression during Epstein-Barr virus infection

Introduction

N⁶‐methyladenosine (m⁶A) is the most prevalent modification that occurs in messenger RNA (mRNA), affecting mRNA splicing, translation, and stability. This modification is reversible, and its related biological functions are mediated by “writers,” “erasers,” and “readers.” The field of viral epitranscriptomics and the role of m⁶A modification in virus–host interaction have attracted much attention recently. When Epstein–Barr virus (EBV) infects a human B lymphocyte, it goes through three phases: the pre‐latent phase, latent phase, and lytic phase. Little is known about the viral and cellular m⁶A epitranscriptomes in EBV infection, especially in the pre‐latent phase during de novo infection.

Methods

Methylated RNA immunoprecipitation sequencing (MeRIP‐seq) and MeRIP‐RT‐qPCR were used to determine the m⁶A‐modified transcripts during de novo EBV infection. RIP assay was used to confirm the binding of EBNA2 and m⁶A readers. Quantitative reverse‐transcription polymerase chain reaction (RT‐qPCR) and Western blot analysis were performed to test the effect of m⁶A on the host and viral gene expression.

Results

Here, we provided mechanistic insights by examining the viral and cellular m⁶A epitranscriptomes during de novo EBV infection, which is in the pre‐latent phase. EBV EBNA2 and BHRF1 were highly m⁶A‐modified upon EBV infection. Knockdown of METTL3 (a “writer”) decreased EBNA2 expression levels. The emergent m⁶A modifications induced by EBV infection preferentially distributed in 3ʹ untranslated regions of cellular transcripts, while the lost m⁶A modifications induced by EBV infection preferentially distributed in coding sequence regions of mRNAs. EBV infection could influence the host cellular m⁶A epitranscriptome.

Conclusions

These results reveal the critical role of m⁶A modification in the process of de novo EBV infection.

Antidiabetic Effects of Arginyl-Fructosyl-Glucose, a Nonsaponin Fraction from Ginseng Processing in Streptozotocin-Induced Type 2 Diabetic Mice through Regulating the PI3K/AKT/GSK-3β and Bcl-2/Bax Signaling Pathways

Streptozotocin- (STZ-) induced type 2 diabetes mellitus (T2DM) caused insulin secretion disorder and hyperglycemia, further causing tissue and organ damage. In recent years, studies on ginseng (Panax ginseng C. A. Meyer) and its saponins (Ginsenosides) have proved to possess antidiabetic pharmacological activities, but the mechanism of nonsaponins on STZ-induced T2DM is still unclear. Arginyl-fructosyl-glucose (AFG) is a representative nonsaponin component produced in the processing of red ginseng. The present study was designed to assess the possible healing consequence of AFG on STZ-induced T2DM in mice and also to explore its fundamental molecular contrivances. T2DM-related indexes, fasting blood glucose levels, and body weight, histological changes, biochemical considerations, biomarkers, the mRNA countenance intensities of inflammatory facts, and variations in correlated protein manifestation in adipose tissue and liver tissue were calculated. Consequences specified that AFG usage successfully amends STZ-induced insulin conflict and liver grievance in T2DM. Systematically, AFG action diminished STZ-induced oxidative stress and inflammatory responses in the liver. In addition, we demonstrated that AFG also attenuates apoptosis and insulin secretion disorders in T2DM by adjusting the PI3K/AKT/GSK3β signaling pathway. At the end, these discoveries recommend that AFG averts the development of T2DM through numerous types of machinery and proposes that AFG can also be used in order to treat T2DM in the future.

Bioinformatic analysis of miRNA–mRNA interaction associated with LMP2A gene in nasopharyngeal carcinoma

Aim: The purpose of the study was to construct miRNA–mRNA network associated with LMP2A in nasopharyngeal carcinoma (NPC). Materials & methods: The dataset GSE53914, GSE12452 and GSE26596 were downloaded from Gene Expression Omnibus and differentially expressed genes (DEGs) identified by GEO2R. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed by ClusterProfiler R package. Protein–protein interaction network and mRNA–miRNA network associated with LMP2A were constructed. Hub genes were identified by Cytoscape. Results: The 135 DEGs associated with LMP2A were identified in NPC. Gene ontology function analysis showed DEGs were significantly enriched in cell–cell adhesion and NF-κB pathway. The hub genes were related to cell cycle. miRNA–mRNA network associated with LMP2A was constructed. Conclusion: The network may provide a way to explore the function of LMP2A in NPC by miRNA.

Epstein-Barr virus LMP2A utilizes Syk and PI3K to activate NF-κB in B-cell lymphomas to increase MIP-1α production

The incidence of Hodgkin's lymphoma (HL) is growing due to an increase in Epstein-Barr virus (EBV)-associated HL in AIDS patients. The HL tumor microenvironment is vital for the survival of the malignant Hodgkin-Reed Sternberg (HRS) cells of HL, which express the EBV protein latent membrane protein 2A (LMP2A). While previous work shows that LMP2A mimics B-cell receptor (BCR) signaling to promote the survival of HRS cells, the ability of LMP2A to establish and maintain the tumor microenvironment through the production of chemokines remains unknown. Since BCR signaling induces the production of the chemokine macrophage inflammatory protein-1α (MIP-1α), and since LMP2A is a BCR mimic, we hypothesized that LMP2A increases MIP-1α levels. A comparison of multiple LMP2A-negative and -positive cell lines demonstrates that LMP2A increases MIP-1α. Additionally, LMP2A-mutant cell lines and pharmacologic inhibitors indicate that LMP2A activates a Syk/PI3K/NF-κB pathway to enhance MIP-1α. Finally, based on the finding that an NF-κB inhibitor decreased MIP-1α RNA/protein in LMP2A-positive cells, we are the first to demonstrate that LMP2A increases the nuclear localization of the NF-κB p65 subunit using DNA-binding assays and confocal microscopy in human B cells. These findings not only have implications for the treatment of HL, but also other LMP2A-expressing B-cell tumors that overexpress NF-κB.

Virus Infection and Death Receptor-Mediated Apoptosis

Virus infection can trigger extrinsic apoptosis. Cell-surface death receptors of the tumor necrosis factor family mediate this process. They either assist persistent viral infection or elicit the elimination of infected cells by the host. Death receptor-mediated apoptosis plays an important role in viral pathogenesis and the host antiviral response. Many viruses have acquired the capability to subvert death receptor-mediated apoptosis and evade the host immune response, mainly by virally encoded gene products that suppress death receptor-mediated apoptosis. In this review, we summarize the current information on virus infection and death receptor-mediated apoptosis, particularly focusing on the viral proteins that modulate death receptor-mediated apoptosis.