scholarly journals Epstein-Barr virus latent membrane protein 2A exploits Notch1 to alter B-cell identity in vivo

Blood ◽  
2009 ◽  
Vol 113 (1) ◽  
pp. 108-116 ◽  
Author(s):  
Leah J. Anderson ◽  
Richard Longnecker
Keyword(s):  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Cell Development ◽  
B Cell Development ◽  
Latent Membrane Protein ◽  
Cell Identity ◽  
Barr Virus ◽  
Epstein Barr

Abstract Expression of latent membrane protein 2 (LMP2A) during B-cell development leads to global alterations in gene transcription similar to those seen in Hodgkin Reed-Sternberg cells of Hodgkin lymphoma (HL). Along with the consistent detection of LMP2A in Epstein-Barr virus–associated HL, this implicates a role for LMP2A in the pathogenesis of HL. We have shown that LMP2A constitutively activates the Notch1 pathway to autoregulate the LMP2A promoter. To determine whether constitutive activation of the Notch pathway is important for LMP2A-mediated alterations in B-cell development in vivo, TgE-LMP2A–transgenic mice were intercrossed with mice expressing loxP-flanked Notch1 genes and Cre recombinase. B cells from TgE Notch1lox/lox-CD19+/Cre mice have an increase in immunoglobulin M and CD43 and a decrease in CD5 expression in the bone marrow compared with TgE Notch1lox/lox mice, indicating the LMP2A signal for developmental aberrations is impaired in the absence of Notch1. Real-time reverse-transcribed polymerase chain reaction analysis reveals that LMP2A requires the Notch1 pathway to alter levels of B cell–specific transcription factors, E2A and EBF. Interestingly, Notch1 appears to be important for LMP2A-mediated survival in low interleukin-7. We propose that LMP2A and the Notch1 pathway may cooperate to induce the alterations in B-cell identity seen in Hodgkin Reed-Sternberg cells.

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2A Preferentially Signals through the Src Family Kinase Lyn

2008 ◽  
Vol 82 (17) ◽  
pp. 8520-8528 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Sh2 Domain ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 2A ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) is a viral protein expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor signal transduction and provides survival and developmental signals to B cells in vivo. Although Lyn has been shown to be important in mediating LMP2A signaling, it is still unclear if Lyn is used preferentially or if LMP2A associates promiscuously with other Src family kinase (SFK) members. To investigate the role of various SFKs in LMP2A signaling, we crossed LMP2A transgenic mice (TgE) with Lyn−/−, Fyn−/−, or Blk−/− mice. TgE Lyn−/− mice had a larger immunoglobulin M (IgM)-positive B-cell population than TgE mice, suggesting that the absence of Lyn prevents LMP2A from delivering survival and developmental signals to the B cells. Both TgE Fyn−/− and TgE Blk−/− mice have an IgM-negative population of splenic B cells, similar to the TgE mice. LMP2A was also transiently transfected into the human EBV-negative B-cell line BJAB to determine which SFK members associate with LMP2A. Lyn was detected in LMP2A immunoprecipitates, whereas Fyn was not. Both Lyn and Fyn were able to bind to an LMP2A mutant which contained a sequence shown previously to bind tightly to the SH2 domain of multiple SFK members. From these results, we conclude that LMP2A preferentially associates with and signals through Lyn compared to its association with other SFKs. This preferential association is due in part to the SH2 domain of Lyn associating with LMP2A.

scholarly journals Epstein-Barr Virus Latent Membrane Protein 2B (LMP2B) Modulates LMP2A Activity

2006 ◽  
Vol 81 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Mark Rovedo ◽  
Richard Longnecker
Keyword(s):  
Signal Transduction ◽  
B Cells ◽  
Membrane Protein ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Cross Linking ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Latent membrane protein 2A (LMP2A) and LMP2B are viral proteins expressed during Epstein-Barr virus (EBV) latency in EBV-infected B cells both in cell culture and in vivo. LMP2A has important roles in modulating B-cell receptor (BCR) signal transduction by associating with the cellular tyrosine kinases Lyn and Syk via specific phosphotyrosine motifs found within the LMP2A N-terminal tail domain. LMP2A has been shown to alter normal BCR signal transduction in B cells by reducing levels of Lyn and by blocking tyrosine phosphorylation and calcium mobilization following BCR cross-linking. Although little is currently known about the function of LMP2B in B cells, the similarity in structure between LMP2A and LMP2B suggests that they may localize to the same cellular compartments. To investigate the function of LMP2B, B-cell lines expressing LMP2A, LMP2B, LMP2A/LMP2B, and the relevant vector controls were analyzed. As was previously shown, cells expressing LMP2A had a dramatic block in normal BCR signal transduction as measured by calcium mobilization and tyrosine phosphorylation. There was no effect on BCR signal transduction in cells expressing LMP2B. Interestingly, when LMP2B was expressed in conjunction with LMP2A, there was a restoration of normal BCR signal transduction upon BCR cross-linking. The expression of LMP2B did not alter the cellular localization of LMP2A but did bind to and prevent the phosphorylation of LMP2A. A restoration of Lyn levels, but not a change in LMP2A levels, was also observed in cells coexpressing LMP2B with LMP2A. From these results, we conclude that LMP2B modulates LMP2A activity.

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