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Epstein-Barr virus LMP2A imposes sensitivity to apoptosis.

Swanson-Mungerson M, Bultema R, Longnecker R - J. Gen. Virol. (2010)

Bottom Line: LMP2A allows BCR signal transduction and induces constitutive activation of NF-kappaB to increase Bcl-2 levels that afford LMP2A-mediated protection from apoptosis in the absence or presence of antigen.In contrast, low levels of NF-kappaB inhibitor only affected Bcl-2 and Bcl-xL levels and increased apoptosis in LMP2A-negative B-cells after BCR cross-linking.These data suggest that LMP2A uniquely makes resting B-cells sensitive to NF-kappaB inhibition and apoptosis and suggest that NF-kappaB may be a novel target to eradicate latently EBV-infected B-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60516, USA. mswans@midwestern.edu

ABSTRACT
In cell lines, the Epstein-Barr virus (EBV)-encoded protein latent membrane protein 2A (LMP2A) protects B-cells from apoptosis by blocking B-cell receptor (BCR) signalling. However, EBV-infected B-cells in vivo are extremely different from cell lines. This study used a murine transgenic model in which B-cells express LMP2A and a BCR specific for hen egg lysozyme to determine whether LMP2A protects resting and antigen-activated B-cells from apoptosis. LMP2A allows BCR signal transduction and induces constitutive activation of NF-kappaB to increase Bcl-2 levels that afford LMP2A-mediated protection from apoptosis in the absence or presence of antigen. In contrast, low levels of NF-kappaB inhibitor only affected Bcl-2 and Bcl-xL levels and increased apoptosis in LMP2A-negative B-cells after BCR cross-linking. These data suggest that LMP2A uniquely makes resting B-cells sensitive to NF-kappaB inhibition and apoptosis and suggest that NF-kappaB may be a novel target to eradicate latently EBV-infected B-cells.

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NF-κB inhibition affects levels of Bcl family members and apoptosis in both LMP2A/HEL-Tg and HEL-Tg B-cells after antigen exposure. (a, b) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated as described above (Fig. 2a, b) and in the presence of HEL (1 μg ml−1). The data represent the fold increase in the percentage of Bcl-expressing B-cells compared with resting, non-antigen-exposed HEL-Tg B-cells and are a combination of three or four mice. *Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed HEL-Tg B-cells. **Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed LMP2A/HEL-Tg B-cells. (c) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated for 18 h as described above for Fig. 2(c) using 1 μg HEL ml−1. The B-cells were analysed as described above for Fig. 2(c). The data are representative of three or four mice with similar results.
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f3: NF-κB inhibition affects levels of Bcl family members and apoptosis in both LMP2A/HEL-Tg and HEL-Tg B-cells after antigen exposure. (a, b) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated as described above (Fig. 2a, b) and in the presence of HEL (1 μg ml−1). The data represent the fold increase in the percentage of Bcl-expressing B-cells compared with resting, non-antigen-exposed HEL-Tg B-cells and are a combination of three or four mice. *Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed HEL-Tg B-cells. **Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed LMP2A/HEL-Tg B-cells. (c) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated for 18 h as described above for Fig. 2(c) using 1 μg HEL ml−1. The B-cells were analysed as described above for Fig. 2(c). The data are representative of three or four mice with similar results.

Mentions: Stimulation through the BCR is known to increase NF-κB activation with subsequent activation of Bcl-2 and Bcl-xL to promote cell survival (Gugasyan et al., 2000). HEL-Tg B-cells exposed to antigen show significantly increased Bcl-2 and Bcl-xL levels, which is reversed by the addition of the NF-κB inhibitor (Figs 3a, b). Since these B-cells now express higher levels of Bcl family members, we determined whether exposure of HEL-Tg B-cells to antigen now made the survival of these cells NF-κB-dependent. Antigen-exposed HEL-Tg B-cells demonstrate an increase in apoptosis when exposed to an NF-κB inhibitor [Ag: 78 % versus Ag+Bay: 90 %; Fig. 3c(i), (ii)], suggesting that, in contrast to resting B-cells, antigen-activated B-cells are dependent on NF-κB signalling for survival.


Epstein-Barr virus LMP2A imposes sensitivity to apoptosis.

Swanson-Mungerson M, Bultema R, Longnecker R - J. Gen. Virol. (2010)

NF-κB inhibition affects levels of Bcl family members and apoptosis in both LMP2A/HEL-Tg and HEL-Tg B-cells after antigen exposure. (a, b) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated as described above (Fig. 2a, b) and in the presence of HEL (1 μg ml−1). The data represent the fold increase in the percentage of Bcl-expressing B-cells compared with resting, non-antigen-exposed HEL-Tg B-cells and are a combination of three or four mice. *Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed HEL-Tg B-cells. **Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed LMP2A/HEL-Tg B-cells. (c) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated for 18 h as described above for Fig. 2(c) using 1 μg HEL ml−1. The B-cells were analysed as described above for Fig. 2(c). The data are representative of three or four mice with similar results.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3066549&req=5

f3: NF-κB inhibition affects levels of Bcl family members and apoptosis in both LMP2A/HEL-Tg and HEL-Tg B-cells after antigen exposure. (a, b) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated as described above (Fig. 2a, b) and in the presence of HEL (1 μg ml−1). The data represent the fold increase in the percentage of Bcl-expressing B-cells compared with resting, non-antigen-exposed HEL-Tg B-cells and are a combination of three or four mice. *Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed HEL-Tg B-cells. **Indicating P<0.05 by unpaired Student's t-test when compared with DMSO-exposed LMP2A/HEL-Tg B-cells. (c) HEL-Tg and LMP2A/HEL-Tg B-cells were incubated for 18 h as described above for Fig. 2(c) using 1 μg HEL ml−1. The B-cells were analysed as described above for Fig. 2(c). The data are representative of three or four mice with similar results.
Mentions: Stimulation through the BCR is known to increase NF-κB activation with subsequent activation of Bcl-2 and Bcl-xL to promote cell survival (Gugasyan et al., 2000). HEL-Tg B-cells exposed to antigen show significantly increased Bcl-2 and Bcl-xL levels, which is reversed by the addition of the NF-κB inhibitor (Figs 3a, b). Since these B-cells now express higher levels of Bcl family members, we determined whether exposure of HEL-Tg B-cells to antigen now made the survival of these cells NF-κB-dependent. Antigen-exposed HEL-Tg B-cells demonstrate an increase in apoptosis when exposed to an NF-κB inhibitor [Ag: 78 % versus Ag+Bay: 90 %; Fig. 3c(i), (ii)], suggesting that, in contrast to resting B-cells, antigen-activated B-cells are dependent on NF-κB signalling for survival.

Bottom Line: LMP2A allows BCR signal transduction and induces constitutive activation of NF-kappaB to increase Bcl-2 levels that afford LMP2A-mediated protection from apoptosis in the absence or presence of antigen.In contrast, low levels of NF-kappaB inhibitor only affected Bcl-2 and Bcl-xL levels and increased apoptosis in LMP2A-negative B-cells after BCR cross-linking.These data suggest that LMP2A uniquely makes resting B-cells sensitive to NF-kappaB inhibition and apoptosis and suggest that NF-kappaB may be a novel target to eradicate latently EBV-infected B-cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Chicago College of Osteopathic Medicine, Midwestern University, Downers Grove, IL 60516, USA. mswans@midwestern.edu

ABSTRACT
In cell lines, the Epstein-Barr virus (EBV)-encoded protein latent membrane protein 2A (LMP2A) protects B-cells from apoptosis by blocking B-cell receptor (BCR) signalling. However, EBV-infected B-cells in vivo are extremely different from cell lines. This study used a murine transgenic model in which B-cells express LMP2A and a BCR specific for hen egg lysozyme to determine whether LMP2A protects resting and antigen-activated B-cells from apoptosis. LMP2A allows BCR signal transduction and induces constitutive activation of NF-kappaB to increase Bcl-2 levels that afford LMP2A-mediated protection from apoptosis in the absence or presence of antigen. In contrast, low levels of NF-kappaB inhibitor only affected Bcl-2 and Bcl-xL levels and increased apoptosis in LMP2A-negative B-cells after BCR cross-linking. These data suggest that LMP2A uniquely makes resting B-cells sensitive to NF-kappaB inhibition and apoptosis and suggest that NF-kappaB may be a novel target to eradicate latently EBV-infected B-cells.

Show MeSH
Related in: MedlinePlus