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  • Title: Identification of optineurin as an interleukin-1 receptor-associated kinase 1-binding protein and its role in regulation of MyD88-dependent signaling.
    Author: Tanishima M, Takashima S, Honda A, Yasuda D, Tanikawa T, Ishii S, MaruYama T.
    Journal: J Biol Chem; 2017 Oct 20; 292(42):17250-17257. PubMed ID: 28882891.
    Abstract:
    Upon stimulation of toll-like receptors with various microbial ligands, induction of a variety of inflammatory genes is elicited by activation of a myeloid differentiation primary-response protein 88 (MyD88)-dependent signaling pathway. Interleukin-1 (IL-1) receptor-associated kinase 1 (IRAK1) plays an essential role in this pathway by activating nuclear factor κB (NF-κB) and mitogen-activated kinases (MAPKs). Here, we identified optineurin (OPTN) as an IRAK1-binding protein by yeast two-hybrid screening using IRAK1 as bait. A C-terminal fragment of OPTN harboring a ubiquitin-binding domain was co-immunoprecipitated with IRAK1. In reporter analyses, overexpression of OPTN inhibited IL-1β-, IRAK1-, and LPS-induced NF-κB activation. Consistently, OPTN deficiency resulted in increased NF-κB activation in response to IL-1β/LPS stimulation. To address the mechanisms underlying the inhibitory effect of OPTN on NF-κB signaling, we focused on tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), which is an adaptor protein of IRAK1 and upon polyubiquitination plays a crucial role during NF-κB activation. Overexpression of OPTN prevented TRAF6 polyubiquitination. Furthermore, OPTN H486R mutant, which is unable to recruit the deubiquitinase CYLD, failed to inhibit IRAK1-induced NF-κB activation. These results suggest that the IRAK1-binding protein OPTN negatively regulates IL-1β/LPS-induced NF-κB activation by preventing polyubiquitination of TRAF6.
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