The E3 Ubiquitin Ligase Mind Bomb-2 (MIB2) Protein Controls B-cell CLL/Lymphoma 10 (BCL10)-dependent NF-κB Activation

Cinthia C Stempin,Liying Chi,Juan P Giraldo-Vela,Anthony A High,Hans Häcker,Vanessa Redecke

doi:10.1074/jbc.m111.263384

Cinthia C Stempin, Liying Chi + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m111.263384

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Abstract

B-cell CLL/lymphoma 10 (BCL10) is crucial for the activation of NF-κB in numerous immune receptor signaling pathways, including the T-cell receptor (TCR) and B-cell receptor signaling pathways. However, the molecular mechanisms that lead to signal transduction from BCL10 to downstream NF-κB effector kinases, such as TAK1 and components of the IKK complex, are not entirely understood. Here we used a proteomic approach and identified the E3 ligase MIB2 as a novel component of the activated BCL10 complex. In vitro translation and pulldown assays suggest direct interaction between BCL10 and MIB2. Overexpression experiments show that MIB2 controls BCL10-mediated activation of NF-κB by promoting autoubiquitination and ubiquitination of IKKγ/NEMO, as well as recruitment and activation of TAK1. Knockdown of MIB2 inhibited BCL10-dependent NF-κB activation. Together, our results identify MIB2 as a novel component of the activated BCL10 signaling complex and a missing link in the BCL10-dependent NF-κB signaling pathway.

Highlights

B-cell CLL/lymphoma 10 (BCL10) is an essential molecule for the activation of the transcription factor NF-␬B in numerous immune receptor signaling pathways
The molecular mechanism of NF-␬B activation has been investigated in more detail in the Toll-like receptor (TLR)/ IL-1R signaling pathway, where TNF receptor-associated factor 6 (TRAF6)-mediated polyubiquitination was shown to control recruitment and activation of transforming growth factor-␤-activated kinase 1 (TAK1) via the ubiquitinbinding TAB proteins, followed by TAK1-mediated phosphorylation of IKK␤ (24)
BCL10 was fused to the subunit B of E. coli DNA gyrase (GyrB; Fig. 1A), which can inducibly be dimerized by adding the bivalent antibiotic coumermycin (CM), thereby mimicking receptor stimulation (Fig. 1B)

Summary

Background

BCL10 is an essential molecule for the activation of the transcription factor NF-␬B in numerous immune receptor signaling pathways. Results: Identification of the E3 ubiquitin ligase MIB2 as part of the activated BCL10 complex controlling NF-␬B activity. E.g. TCR cross-linking, leads to recruitment of BCL10-MALT1 to the upstream CARD containing adaptor protein CARD-containing MAGUK protein 1 (CARMA1), resulting in the formation of a trimolecular signaling complex consisting of CARMA1, BCL10, and MALT1, referred to as the CBM complex Oligomerization of these proteins eventually results in the formation of nondegradative polyubiquitin chains and activation of downstream kinases, such as transforming growth factor-␤-activated kinase 1 (TAK1) and the TAK1-substrate I␬B-kinase ␤ (IKK␤) (19 –21). The molecular mechanism of NF-␬B activation has been investigated in more detail in the Toll-like receptor (TLR)/ IL-1R signaling pathway, where TNF receptor-associated factor 6 (TRAF6)-mediated polyubiquitination was shown to control recruitment and activation of TAK1 via the ubiquitinbinding TAB proteins, followed by TAK1-mediated phosphorylation of IKK␤ (24). Our findings identify MIB2 as a missing link between the BCL10 complex and the NF-␬B activation pathway

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DISCUSSION