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Malt1-dependent RelB cleavage promotes canonical NF-kappaB activation in lymphocytes and lymphoma cell lines.

ABSTRACT: The protease activity of the paracaspase Malt1 contributes to antigen receptor-mediated lymphocyte activation and lymphomagenesis. Malt1 activity is required for optimal NF-?B activation, but little is known about the responsible substrate(s). Here we report that Malt1 cleaved the NF-?B family member RelB after Arg-85. RelB cleavage induced its proteasomal degradation and specifically controlled DNA binding of RelA- or c-Rel-containing NF-?B complexes. Overexpression of RelB inhibited expression of canonical NF-?B target genes and led to impaired survival of diffuse large B-cell lymphoma cell lines characterized by constitutive Malt1 activity. These findings identify a central role for Malt1-dependent RelB cleavage in canonical NF-?B activation and thereby provide a rationale for the targeting of Malt1 in immunomodulation and cancer treatment.

SUBMITTER: Hailfinger S

PROVIDER: S-EPMC3167514 | biostudies-other | 2011 Aug

REPOSITORIES: biostudies-other

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Malt1-dependent RelB cleavage promotes canonical NF-kappaB activation in lymphocytes and lymphoma cell lines.

Hailfinger Stephan S Nogai Hendrik H Pelzer Christiane C Jaworski Maike M Cabalzar Katrin K Charton Jean-Enno JE Guzzardi Montserrat M Décaillet Chantal C Grau Michael M Dörken Bernd B Lenz Peter P Lenz Georg G Thome Margot M

Proceedings of the National Academy of Sciences of the United States of America 20110822 35

The protease activity of the paracaspase Malt1 contributes to antigen receptor-mediated lymphocyte activation and lymphomagenesis. Malt1 activity is required for optimal NF-κB activation, but little is known about the responsible substrate(s). Here we report that Malt1 cleaved the NF-κB family member RelB after Arg-85. RelB cleavage induced its proteasomal degradation and specifically controlled DNA binding of RelA- or c-Rel-containing NF-κB complexes. Overexpression of RelB inhibited expression ...[more]

PMID: 21873235

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Project description:The ability of the transcription factor NF-kappaB to upregulate anti-apoptotic proteins has been linked to the chemoresistance of solid tumors to standard chemotherapy. In contrast, recent studies have proposed that, in response to doxorubicin, NF-kappaB can be pro-apoptotic through repression of anti-apoptotic target genes. However, there is little evidence analyzing the outcome of NF-kappaB inhibition on the cytotoxicity of doxorubicin in studies describing pro-apoptotic NF-kappaB activity. In this study, we further characterize the activation of NF-kappaB in response to doxorubicin and evaluate its role in chemotherapy-induced cell death in sarcoma cells where NF-kappaB is reported to be pro-apoptotic. Doxorubicin treatment in U2OS cells induced canonical NF-kappaB activity as evidenced by increased nuclear accumulation of phosphorylated p65 at serine 536 and increased DNA-binding activity. Co-treatment with a small molecule IKKbeta inhibitor, Compound A, abrogated this response. RT-PCR evaluation of anti-apoptotic gene expression revealed that doxorubicin-induced transcription of cIAP2 was inhibited by Compound A, while doxorubicin-induced repression of other anti-apoptotic genes was unaffected by Compound A or siRNA to p65. Furthermore, the combination of doxorubicin and canonical NF-kappaB inhibition with Compound A or siRNA to p65 resulted in decreased cell viability measured by trypan blue staining and MTS assay and increased apoptosis measured by cleaved poly (ADP-ribose) polymerase and cleaved caspase 3 when compared to doxorubicin alone. Our results demonstrate that doxorubicin-induced canonical NF-kappaB activity associated with phosphorylated p65 is anti-apoptotic in its function and that doxorubicin-induced repression of anti-apoptotic genes occurs independent of p65. Therefore, combination therapies incorporating NF-kappaB inhibitors together with standard chemotherapies remains a viable method to improve the clinical outcomes in patients with advanced stage malignancies.

Dataset Information

Malt1-dependent RelB cleavage promotes canonical NF-kappaB activation in lymphocytes and lymphoma cell lines.

Publications

Malt1-dependent RelB cleavage promotes canonical NF-kappaB activation in lymphocytes and lymphoma cell lines.

Similar Datasets

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