Tripartite motif 8 (TRIM8) modulates TNFα- and IL-1β–triggered NF-κB activation by targeting TAK1 for K63-linked polyubiquitination

Abstract

The tripartite motif (TRIM)-containing proteins are a family of proteins that have been known to be involved in divergent biological processes, including important roles in immune responses through regulating various signaling pathways. In this study, we identified a member of the TRIM family, TRIM8, as a positive regulator of tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β)-triggered NF-κB activation. Overexpression of TRIM8 activated NF-κB and potentiated TNFα-and IL-1β-induced activation of NF-κB, whereas knockdown of TRIM8 had opposite effects. Coimmunoprecipitations indicated that TRIM8 interacted with TGFβ activated kinase 1 (TAK1), a serine/threonine kinase essential for TNFα-and IL-β-induced NF-κB activation. Furthermore, we found that TRIM8 mediated K63-linked polyubiquitination of TAK1 triggered by TNFα and IL-1β. Our findings demonstrate that TRIM8 serves as a critical regulator of TNFα-and IL-1β-induced NF-κB activation by mediating K63-linked polyubiquitination of TAK1.T he transcription factor NF-κB plays a pivotal role in many cellular events such as cell proliferation, inhibition of apoptosis, and innate immunity. NF-κB activation requires the signal-induced phosphorylation and degradation of IκB proteins (1). The kinase that phosphorylates IκB, termed IκB kinase (IKK) complex, consists of the catalytic subunits IKKα, IKKβ, and the regulatory subunit NEMO/IKKγ. The IKK complex is activated by a large variety of stimuli, including the proinflammatory cytokines tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) (2).Binding of TNFα to its receptor TNF-RI results in recruitment of the adaptor protein TRADD. TRADD further recruits TRAF2, TRAF5, and RIP1 to the receptor complex. TRAF2 mediates polyubiquitination of RIP1, mainly in a K63-linked manner. Ubiquitinated RIP further recruits TAB2 and TAK1 and mediates activation of the latter. The activated RIP1-TAK1-TAB2 complex subsequently activates the IKK complex, leading to phosphorylation of IκBα and activation of NF-κB (3). Similarly, binding of IL-1β to its receptor IL-1R leads to the recruitment of adaptor proteins and kinases, including MyD88, IRAK1, and IRAK4. IRAK4 phospholylates and activates IRAK1, which in turn recruits TRAF6. IRAK1 and TRAF6 form a complex that is released from the receptor. TRAF6 possesses an E3 ubiquitin ligase activity that mediates its K63-linked autopolyubiquitination. Ubiquitinated TRAF6 further recruits the TAK1-TAB2-TAB3 complex, resulting in the activation of TAK1. Activated TAK1 eventually phosphorylates and activates IKK, leading to activation of NF-κB (3, 4).TAK1 is a member of the MAPK kinase kinase family that was originally found to function in the transforming growth factor β (TGFβ)-mediated MAPK activation (5). TAK1 has been demonstrated to be essential in TNFα-and IL-1β-mediated activation of NF-κB and JNK (6, 7). In all of these pathways, activation of TAK1 is an important event that transmits the upstream signal from the receptor complex to the downstream signaling molecules (3, 4, 6, 7).S...

TRIM59 interacts with ECSIT and negatively regulates NF-κB and IRF-3/7-mediated signal pathways

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TRIM-mediated precision autophagy targets cytoplasmic regulators of innate immunity

“…Additional upstream mechanisms may be controlled by TRIMs detected in our screen, as in the case of TRIM8, which is known to be inducible by IFN-γ (Toniato et al, 2002). TRIM8 activates TAK1 (Li et al, 2011), which is proposed to occur through K63 polyubiquitination. TAK1, in turn, activates AMPK-dependent autophagy (Kanayama et al, 2004;Herrero-Martín et al, 2009;Criollo et al, 2011) by phosphorylating AMPK (Xie et al, 2006).…”

The Dual-specificity Phosphatase DUSP14 Negatively Regulates Tumor Necrosis Factor- and Interleukin-1-induced Nuclear Factor-κB Activation by Dephosphorylating the Protein Kinase TAK1

“…Constructs-NF-B-and IFN-␤ promoter-luciferase reporter plasmids and mammalian expression plasmids for HAtagged TAK1, TAB1-TAB3, IKK␣/␤/␥, TRAF2, and TRAF6 were described previously (21). Mammalian expression plasmid for FLAG-tagged DUSP14 was constructed by standard molecular biology techniques.…”