Epstein-Barr Virus (EBV) Latent Membrane Protein 2A Regulates B-Cell Receptor-Induced Apoptosis and EBV Reactivation through Tyrosine Phosphorylation

ABSTRACT Epstein-Barr virus (EBV) is a human herpesvirus that establishes a lifelong latent infection of B cells. Within the immune system, apoptosis is a central mechanism in normal lymphocyte homeostasis both during early lymphocyte development and in response to antigenic stimuli. In this study, we found that latent membrane protein 2A (LMP2A) inhibited B-cell receptor (BCR)-induced apoptosis in Burkitt's lymphoma cell lines. Genistein, a specific inhibitor of tyrosine-specific protein kinases, blocked BCR-induced apoptosis and EBV reactivation in the cells. These findings indicate that LMP2A blocks BCR-induced cell apoptosis and EBV reactivation through the inhibition of activation of tyrosine kinases by BCR cross-linking.

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Epstein-Barr virus latent membrane protein 2A is a B-cell receptor mimic and essential for B-cell survival

Blood ◽

10.1182/blood-2007-05-090142 ◽

2007 ◽

Vol 110 (10) ◽

pp. 3715-3721 ◽

Cited By ~ 134

Author(s):

Christoph Mancao ◽

Wolfgang Hammerschmidt

Keyword(s):

B Cells ◽

Membrane Protein ◽

B Cell ◽

Epstein Barr Virus ◽

Cell Receptor ◽

Latent Membrane Protein ◽

B Cell Receptor ◽

Latent Membrane Protein 2A ◽

Barr Virus ◽

Epstein Barr

AbstractMany cells latently infected with Epstein-Barr virus (EBV), including certain virus-associated tumors, express latent membrane protein 2A (LMP2A), suggesting an important role for this protein in viral latency and oncogenesis. LMP2A mimics B-cell receptor signaling but can also act as a decoy receptor blocking B-cell receptor (BCR) activation. Studies of peripheral B cells have not resolved this apparent contradiction because LMP2A seems to be dispensable for EBV-induced transformation of these B cells in vitro. We show here that LMP2A is essential for growth transformation of germinal center B cells, which do not express the genuine BCR because of deleterious somatic hypermutations in their immunoglobulin genes. BCR-positive (BCR+) and BCR-negative (BCR−) B cells are readily transformed with a recombinant EBV encoding a conditional, floxed LMP2A allele, but the survival and continued proliferation of both BCR+ and BCR− B cells is strictly dependent on LMP2A. These findings indicate that LMP2A has potent, distinct antiapoptotic and/or transforming characteristics and point to its role as an indispensable BCR mimic in certain B cells from which human B-cell tumors such as Hodgkin lymphoma originate.

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Roles of the ITAM and PY Motifs of Epstein-Barr Virus Latent Membrane Protein 2A in the Inhibition of Epithelial Cell Differentiation and Activation of β-Catenin Signaling

Journal of Virology ◽

10.1128/jvi.79.4.2375-2382.2005 ◽

2005 ◽

Vol 79 (4) ◽

pp. 2375-2382 ◽

Cited By ~ 68

Author(s):

Jennifer A. Morrison ◽

Nancy Raab-Traub

Keyword(s):

Membrane Protein ◽

Epstein Barr Virus ◽

Nuclear Translocation ◽

Cell Receptor ◽

Latent Membrane Protein ◽

Latent Membrane Protein 2A ◽

Barr Virus ◽

Cellular Processes ◽

Epstein Barr ◽

Virus Latent Membrane Protein

ABSTRACT Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) is important for maintenance of latency in infected B lymphocytes. Through its immunoreceptor tyrosine-based activation motif (ITAM) and PY motifs, LMP2A is able to block B-cell receptor (BCR) signaling, bind BCR-associated kinases, and manipulate the turnover of itself and these kinases via a PY-mediated interaction with the Nedd4 family of ubiquitin ligases. In epithelial cells, LMP2A has been shown to activate the phosphatidylinositol 3′-OH kinase/Akt and β-catenin signaling pathways. In the present study, the biological consequences of LMP2A expression in the normal human foreskin keratinocyte (HFK) cell line were investigated and the importance of the ITAM and PY motifs for LMP2A signaling effects in HFK cells was ascertained. The ITAM was essential for the activation of Akt by LMP2A in HFK cells, while both the ITAM and PY motifs contributed to LMP2A-mediated accumulation and nuclear translocation of the oncoprotein β-catenin. LMP2A inhibited induction of differentiation in an assay conducted with semisolid methylcellulose medium, and the PY motifs were critical for this inhibition. LMP2A is expressed in the EBV-associated epithelial malignancies nasopharyngeal carcinoma and gastric carcinoma, and these data indicate that LMP2A affects cellular processes that likely contribute to carcinogenesis.

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