Abstract 5395: The E3 ligase Itch and deubiquitinase Cyld act together to regulate Tak1 and inflammation

Karmanos Cancer Institute, Department of Oncology, Wayne State University School of Medicine, Detroit, Michigan, USA.
Nature Immunology (Impact Factor: 20). 11/2011; 12(12):1176-83. DOI: 10.1038/ni.2157
Source: PubMed


Chronic inflammation has been strongly associated with tumor progression, but the underlying mechanisms remain elusive. Here we demonstrate that E3 ligase Itch and deubiquitinase Cyld formed a complex via interaction through 'WW-PPXY' motifs. The Itch-Cyld complex sequentially cleaved Lys63-linked ubiquitin chains and catalyzed Lys48-linked ubiquitination on the kinase Tak1 to terminate inflammatory signaling via tumor necrosis factor. Reconstitution of wild-type Cyld but not the mutant Cyld(Y485A), which cannot associate with Itch, blocked sustained Tak1 activation and proinflammatory cytokine production by Cyld(-/-) bone marrow-derived macrophages. Deficiency in Itch or Cyld led to chronic production of tumor-promoting cytokines by tumor-associated macrophages and aggressive growth of lung carcinoma. Thus, we have identified an Itch-Cyld-mediated regulatory mechanism in innate inflammatory cells.

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Available from: Richard A Flavell, Aug 15, 2014
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    • "In some situations, distinct specificity of the DUB and the ligase for different ubiquitin chain linkages allows chain editing and repurposing of the modified substrate (Ahmed et al., 2011). In others, coupling two antagonistic activities may allow a rapid and transient change in substrate abundance in response to upstream signals, which mediate complex assembly or control activity of one of the enzymes (Popov et al., 2007b; Huang et al., 2011). "
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    • "Functionally it is a deubiquitylating enzyme (DUB) which removes mainly K63-linked polyubiquitin chains from several specific substrates, influencing in a negative way the activation status and/or spatial distribution of these target proteins in different signaling pathways. Numerous studies both in vitro and in vivo provided us with new insights in its established function as an important negative regulator of inflammatory responses, by counteracting the aberrant activation of NFκB signaling: Cyld−/− animals spontaneously develop intestinal inflammation and autoimmune symptoms due to the constitutive activation of the TAK1/IKK/IκBα axis [12], [13]; the study of Lim et al. described a CYLD dependent negative NFκB regulation during bacteria induced lung inflammation in mice via deubiquitylation of TRAF6 and TRAF7 [14]; moreover, the same scientific group showed that Cyld knockout mice are protected from Streptococcus pneumonia infection and lethality via a negative crosstalk with p38 MAPK [15]; a synergistic crosstalk between the E3 ligase Itch and CYLD for TAK1 inactivation and termination of tumor necrose factor dependent inflammatory signaling was recently described [16]. "
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    ABSTRACT: In T cells PKCθ mediates the activation of critical signals downstream of TCR/CD28 stimulation. We investigated the molecular mechanisms by which PKCθ regulates NFκB transactivation by examining PKCθ/β single and double knockout mice and observed a redundant involvement of PKCθ and PKCβ in this signaling pathway. Mechanistically, we define a PKCθ-CYLD protein complex and an interaction between the positive PKCθ/β and the negative CYLD signaling pathways that both converge at the level of TAK1/IKK/I-κBα/NFκB and NFAT transactivation. In Jurkat leukemic T cells, CYLD is endoproteolytically processed in the initial minutes of stimulation by the paracaspase MALT1 in a PKC-dependent fashion, which is required for robust IL-2 transcription. However, in primary T cells, CYLD processing occurs with different kinetics and an altered dependence on PKC. The formation of a direct PKCθ/CYLD complex appears to regulate the short-term spatial distribution of CYLD, subsequently affecting NFκB and NFAT repressional activity of CYLD prior to its MALT1-dependent inactivation. Taken together, our study establishes CYLD as a new and critical PKCθ interactor in T cells and reveals that antagonistic PKCθ/β-CYLD crosstalk is crucial for the adjustment of immune thresholds in primary mouse CD3(+) T cells.
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    • "Alternatively, nondegradative ubiquitination could function by stabilizing signaling complexes through one of two mechanisms: (1) by preventing K48 ubiquitination and degradation of signaling intermediates , as has been demonstrated for RIP1 (Harhaj and Dixit 2011), and (2) by physically stabilizing complexes through ''cross-linking'' of UBD-containing proteins. In fact, both A20 and, more recently, CYLD (cylindromatosis protein) (Ahmed et al. 2011) are reported to negatively regulate signaling not merely by removing K63 linkages, but also by facilitating replacement of these linkages with K48 linkages that target signaling components for proteasomal degradation. These data suggest that removal of K63 linkages is not sufficient for signal termination and that DUBs may primarily suppress signaling by targeting active signaling complexes for degradation, rather than by removing K63. "
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