Abstract
The CARD domain protein BCL10 and paracaspase MALT1 are essential for the activation of IkappaB kinase (IKK) and NF-kappaB in response to T cell receptor (TCR) stimulation. Here we present evidence that TRAF6 ubiquitin ligase and TAK1 protein kinase mediate IKK activation by BCL10 and MALT1. RNAi-mediated silencing of MALT1, TAK1, TRAF6, and TRAF2 suppressed TCR-dependent IKK activation and interleukin-2 production in T cells. Furthermore, we have reconstituted the pathway from BCL10 to IKK activation in vitro with purified proteins of MALT1, TRAF6, TAK1, and ubiquitination enzymes including Ubc13/Uev1A. We find that a small fraction of BCL10 and MALT1 proteins form high molecular weight oligomers. Strikingly, only these oligomeric forms of BCL10 and MALT1 can activate IKK in vitro. The MALT1 oligomers bind to TRAF6, induce TRAF6 oligomerization, and activate the ligase activity of TRAF6 to polyubiquitinate NEMO. These results reveal an oligomerization --> ubiquitination --> phosphorylation cascade that culminates in NF-kappaB activation in T lymphocytes.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing*
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B-Cell CLL-Lymphoma 10 Protein
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Carrier Proteins / metabolism*
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Caspases
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HeLa Cells
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Humans
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I-kappa B Kinase
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Immunity, Innate / physiology
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Interleukin-2 / metabolism
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Lymphoma, B-Cell, Marginal Zone*
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MAP Kinase Kinase Kinases / metabolism*
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Macromolecular Substances
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Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein
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NF-kappa B / metabolism
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Neoplasm Proteins*
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Phosphorylation
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Protein Binding / physiology
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Protein Serine-Threonine Kinases / metabolism*
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Proteins / metabolism*
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RNA Interference / physiology
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Signal Transduction / physiology
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T-Lymphocytes / enzymology*
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T-Lymphocytes / immunology
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TNF Receptor-Associated Factor 2
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TNF Receptor-Associated Factor 6
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Transcription Factors / metabolism
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Ubiquitin / metabolism
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Ubiquitin-Conjugating Enzymes / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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B-Cell CLL-Lymphoma 10 Protein
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BCL10 protein, human
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Carrier Proteins
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Interleukin-2
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Macromolecular Substances
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NF-kappa B
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Neoplasm Proteins
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Proteins
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TNF Receptor-Associated Factor 2
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TNF Receptor-Associated Factor 6
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Transcription Factors
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Ubiquitin
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UBE2V1 protein, human
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Ubiquitin-Conjugating Enzymes
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Protein Serine-Threonine Kinases
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CHUK protein, human
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I-kappa B Kinase
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IKBKB protein, human
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IKBKE protein, human
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MAP Kinase Kinase Kinases
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MAP kinase kinase kinase 7
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Caspases
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MALT1 protein, human
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Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein