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EBV latent membrane protein 1 activates Akt, NFkappaB, and Stat3 in B cell lymphomas.

ABSTRACT: Latent membrane protein 1 (LMP1) is the major oncoprotein of Epstein-Barr virus (EBV). In transgenic mice, LMP1 promotes increased lymphoma development by 12 mo of age. This study reveals that lymphoma develops in B-1a lymphocytes, a population that is associated with transformation in older mice. The lymphoma cells have deregulated cell cycle markers, and inhibitors of Akt, NFkappaB, and Stat3 block the enhanced viability of LMP1 transgenic lymphocytes and lymphoma cells in vitro. Lymphoma cells are independent of IL4/Stat6 signaling for survival and proliferation, but have constitutively activated Stat3 signaling. These same targets are also deregulated in wild-type B-1a lymphomas that arise spontaneously through age predisposition. These results suggest that Akt, NFkappaB, and Stat3 pathways may serve as effective targets in the treatment of EBV-associated B cell lymphomas.

SUBMITTER: Shair KH

PROVIDER: S-EPMC2065877 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Src kinase and Syk activation initiate PI3K signaling by a chimeric latent membrane protein 1 in Epstein-Barr virus (EBV)+ B cell lymphomas.

Project description:The B lymphotrophic ?-herpesvirus EBV is associated with a variety of lymphoid- and epithelial-derived malignancies, including B cell lymphomas in immunocompromised and immunosuppressed individuals. The primary oncogene of EBV, latent membrane protein 1 (LMP1), activates the PI3K/Akt pathway to induce the autocrine growth factor, IL-10, in EBV-infected B cells, but the mechanisms underlying PI3K activation remain incompletely understood. Using small molecule inhibition and siRNA strategies in human B cell lines expressing a chimeric, signaling-inducible LMP1 protein, nerve growth factor receptor (NGFR)-LMP1, we show that NGFR-LMP1 utilizes Syk to activate PI3K/Akt signaling and induce IL-10 production. NGFR-LMP1 signaling induces phosphorylation of BLNK, a marker of Syk activation. Whereas Src kinases are often required for Syk activation, we show here that PI3K/Akt activation and autocrine IL-10 production by NGFR-LMP1 involves the Src family kinase Fyn. Finally, we demonstrate that NGFR-LMP1 induces phosphorylation of c-Cbl in a Syk- and Fyn-dependent fashion. Our results indicate that the EBV protein LMP1, which lacks the canonical ITAM required for Syk activation, can nevertheless activate Syk, and the Src kinase Fyn, resulting in downstream c-Cbl and PI3K/Akt activation. Fyn, Syk, and PI3K/Akt antagonists thus may present potential new therapeutic strategies that target the oncogene LMP1 for treatment of EBV+ B cell lymphomas.

| S-EPMC3411813 | biostudies-literature

EBV Latent membrane protein1 modifies EV content

Project description:Extracellular vesicles (EV) mediate intercellular communication events and alterations in normal vesicle content contribute to function and disease initiation or progression. The ability to package a variety of cargo and transmit molecular information between cells renders EVs important mediators of cell to cell crosstalk. Latent membrane protein 1 (LMP1) is a chief viral oncoprotein expressed in most Epstein-Barr virus (EBV)-associated cancers and is released from cells at high levels in EVs. LMP1 containing EVs have been demonstrated to promote cell growth, migration, differentiation, and regulate immune cell function. Despite these significant changes in recipient cells induced by LMP1 modified EVs, the mechanism how this viral oncogene modulates the recipient cells towards these phenotypes is not well understood. We hypothesize that LMP1 alters EV content and following uptake of the LMP1-modified EVs by the recipient cells results in the activation of cell signaling pathways and increased gene expression which modulates the biological properties of recipient cell towards a new phenotype. Our results show that LMP1 expression alters the EV protein and microRNA content packaged into EVs.

2020-11-03 | PXD021914 | Pride

Phosphorylated ezrin is associated with EBV latent membrane protein 1 in nasopharyngeal carcinoma and induces cell migration.

Project description:Tumor metastasis is a complex phenomenon that is the culmination of effects of numerous cellular factors. We have shown that the Epstein-Barr virus (EBV) oncoprotein, latent membrane protein 1 (LMP1), is capable of inducing a wide range of such factors in cell culture, expression of which is also elevated in the LMP1-expressing tumor, nasopharyngeal carcinoma (NPC), a highly invasive neoplasm. Recently, the membrane crosslinker protein, ezrin, has been implicated in tumor cell metastasis and malignant progression. In this study, we evaluated the possible role of LMP1 and ezrin in the pathophysiology of NPC. We show that C-terminal phosphorylation of ezrin is increased by the expression of LMP1 in nasopharyngeal (NP) cells through a protein kinase C (PKC) pathway. LMP1 enhances the organization of a ternary complex of CD44, ezrin and F-actin, which is a prerequisite for ezrin phosphorylation. In NPC tissues, the expression of phosphoezrin and LMP1 is directly correlated. Silencing of endogenously expressed ezrin suppresses LMP1-induced cell motility and invasiveness. Moreover, the inhibition of ezrin phosphorylation by PKC inhibitor suppresses migration and invasion of NP cells. These data show that the phosphorylation of ezrin and its recruitment to the cell membrane linked to F-actin and CD44 is a process required for LMP1-stimulated cell motility and invasion of NP cells.

| S-EPMC3422673 | biostudies-literature

Human serum antibodies against EBV latent membrane protein 1 cross-react with ?-synuclein.

Project description:ObjectivesTo identify the epitope on ?-synuclein (?-syn) to which antibodies against the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) bind and to determine whether antibodies targeting this mimicry domain are present in human sera.MethodsReactivity of the ?-syn-cross-reacting anti-LMP1 monoclonal antibody CS1-4 to a synthetic peptide containing the putative mimicry domain was compared to those in which this domain was mutated and to murine and rat ?-syn (which differ from human ?-syn at this site) in Western blots. Using ELISA, sera from EBV+ (n = 4) and EBV- (n = 12) donors as well as those with infectious mononucleosis (IM; n = 120), and Hodgkin disease (HD; n = 33) were interrogated for antibody reactivity to synthetic peptides corresponding to regions of ?-syn and LMP1 containing the mimicry domain.ResultsCS1-4 showed strong reactivity to wild-type human ?-syn, but not to the mutant peptides or rodent ?-syn. Control EBV- and EBV+ sera showed no reactivity to ?-syn or LMP1 peptides. However, a significant proportion of IM and HD sera contained immunoglobulin M (IgM) (59% and 70%, in IM and HD, respectively), immunoglobulin G (IgG) (40% and 48%), and immunoglobulin A (IgA) (28% and 36%) antibodies to both peptides, as well as a significant correlation in the titers of IgM (? = 0.606 and 0.664, for IM and HD, respectively), IgG (0.526 and 0.836), and IgA (0.569 and 0.728) antibodies targeting LMP1 and ?-syn peptides.ConclusionsAnti-EBV-LMP1 antibodies cross-reacting with a defined epitope in ?-syn are present in human patients. These findings may have implications for the pathogenesis of synucleinopathies.

| S-EPMC4864620 | biostudies-literature

Latent Membrane Protein LMP2A Impairs Recognition of EBV-Infected Cells by CD8+ T Cells.

Project description:The common pathogen Epstein-Barr virus (EBV) transforms normal human B cells and can cause cancer. Latent membrane protein 2A (LMP2A) of EBV supports activation and proliferation of infected B cells and is expressed in many types of EBV-associated cancer. It is not clear how latent EBV infection and cancer escape elimination by host immunity, and it is unknown whether LMP2A can influence the interaction of EBV-infected cells with the immune system. We infected primary B cells with EBV deleted for LMP2A, and established lymphoblastoid cell lines (LCLs). We found that CD8+ T cell clones showed higher reactivity against LMP2A-deficient LCLs compared to LCLs infected with complete EBV. We identified several potential mediators of this immunomodulatory effect. In the absence of LMP2A, expression of some EBV latent antigens was elevated, and cell surface expression of MHC class I was marginally increased. LMP2A-deficient LCLs produced lower amounts of IL-10, although this did not directly affect CD8+ T cell recognition. Deletion of LMP2A led to several changes in the cell surface immunophenotype of LCLs. Specifically, the agonistic NKG2D ligands MICA and ULBP4 were increased. Blocking experiments showed that NKG2D activation contributed to LCL recognition by CD8+ T cell clones. Our results demonstrate that LMP2A reduces the reactivity of CD8+ T cells against EBV-infected cells, and we identify several relevant mechanisms.

| S-EPMC4465838 | biostudies-literature

Current Progress in EBV-Associated B-Cell Lymphomas.

Project description:Epstein-Barr virus (EBV) was the first human tumor virus discovered more than 50 years ago. EBV-associated lymphomagenesis is still a significant viral-associated disease as it involves a diverse range of pathologies, especially B-cell lymphomas. Recent development of high-throughput next-generation sequencing technologies and in vivo mouse models have significantly promoted our understanding of the fundamental molecular mechanisms which drive these cancers and allowed for the development of therapeutic intervention strategies. This review will highlight the current advances in EBV-associated B-cell lymphomas, focusing on transcriptional regulation, chromosome aberrations, in vivo studies of EBV-mediated lymphomagenesis, as well as the treatment strategies to target viral-associated lymphomas.

| S-EPMC6053051 | biostudies-literature

PRA1 promotes the intracellular trafficking and NF-kappaB signaling of EBV latent membrane protein 1.

Project description:Latent membrane protein 1 (LMP1), which is an Epstein-Barr virus (EBV)-encoded oncoprotein, induces nuclear factor-kappa B (NF-kappaB) signaling by mimicking the tumor necrosis factor receptor (TNFR). LMP1 signals primarily from intracellular compartments in a ligand-independent manner. Here, we identify a new LMP1-interacting molecule, prenylated Rab acceptor 1 (PRA1), which interacts with LMP1 for the first time through LMP1's transmembrane domain, and show that PRA1 is involved in intracellular LMP1 trafficking and LMP1-induced NF-kappaB activity. Immunofluorescence and biochemical analyses revealed that LMP1 physically interacted with PRA1 at the Golgi apparatus, and the colocalization of LMP1 and PRA1 to the Golgi was sensitive to nocodazole and brefeldin A. Coexpression of a PRA1 export mutant or knockdown of PRA1 led to redistribution of LMP1 and its associated signaling molecules to the endoplasmic reticulum and subsequent impairment of LMP1-induced NF-kappaB activation, but had no effect on CD40- and TNFR1-mediated signaling or the functional integrity of the Golgi apparatus. These novel findings provide important new insights into LMP1, and identify an unexpected new role for PRA1 in cellular signaling.

| S-EPMC1560356 | biostudies-literature

Expression data from EBV-encoded latent membrane protein 2A (LMP2A) positive and negative nasopharyngeal carcinoma (NPC) cell lines

Project description:Latent infection with Epstein-Barr virus (EBV) is recognised as a factor in the pathogenesis of nasopharyngeal carcinoma (NPC). We found that EBV encoded Latent membrane protein 2A (LMP2A) enhances lipid accumulation significantly in NPC cells. We used microarrays to identify differential genes regulated by LMP2A in NPC cell lines.

2018-08-21 | GSE118807 | GEO

Epstein-Barr Virus (EBV)-positive B-cell strain, 28-2: Low v. High latent membrane protein 1 (LMP1)-mRFP expression

Project description:Expression of mRNAs in an EBV-positive B-cell strain, 28-2. 28-2 are infected with a derivative of the B-958 strain of EBV, which expresses eGFP constitutively and LMP1 fused to mRFP from its native promoter. Single cells were sorted by flow cytometry for their levels of LMP1-mRFP (5% expressing the lowest levels of LMP1-mRFP or 5% expressing the highest levels of LMP1-mRFP) Two-condition experiment: Low v. High LMP1-mRFP expression. Biological replicates: 3 Low LMP1-mRFP, 3 High LMP1-mRFP. Samples were normalized to the expression of mRNAs in a pool of unsorted 28-2 cells.

2012-02-01 | E-GEOD-33673 | biostudies-arrayexpress

The EBV latent membrane protein 1 (LMP1) induces cellular microRNA-146a, a modulator of lymphocyte signaling pathways

Project description:This SuperSeries is composed of the following subset Series: GSE10057: The Epstein-Barr Virus latent membrane protein 1 (LMP1) induces cellular microRNA146a GSE10105: Alteration of microRNA gene expression by EBV encoded LMP1 oncogene Keywords: SuperSeries Refer to individual Series

2008-01-08 | E-GEOD-10107 | biostudies-arrayexpress

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