Lysine 63-linked Polyubiquitination of TAK1 at Lysine 158 Is Required for Tumor Necrosis Factor α- and Interleukin-1β-induced IKK/NF-κB and JNK/AP-1 Activation

Transforming growth factor-beta-activated kinase 1 (TAK1) plays an essential role in the tumor necrosis factor alpha (TNF alpha)- and interleukin-1 beta (IL-1 beta)-induced I kappa B kinase (IKK)/nuclear factor-kappa B (NF-kappa B) and c-Jun N-terminal kinase (JNK)/activator protein 1 (AP-1) activation. Here we report that TNF alpha and IL-1 beta induce Lys(63)-linked TAK1 polyubiquitination at the Lys(158) residue within the kinase domain. Tumor necrosis factor receptor-associated factors 2 and 6 (TRAF2 and -6) act as the ubiquitin E3 ligases to mediate Lys(63)-linked TAK1 polyubiquitination at the Lys(158) residue in vivo and in vitro. Lys(63)-linked TAK1 polyubiquitination at the Lys(158) residue is required for TAK1-mediated IKK complex recruitment. Reconstitution of TAK1-deficient mouse embryo fibroblast cells with TAK1 wild type or a TAK1 mutant containing a K158R mutation revealed the importance of this site in TNF alpha and IL-1 beta-mediated IKK/NF-kappa B and JNK/AP-1 activation as well as IL-6 gene expression. Our findings demonstrate that Lys(63)-linked polyubiquitination of TAK1 at Lys(158) is essential for its own kinase activation and its ability to mediate its downstream signal transduction pathways in response to TNF alpha and IL-1 beta stimulation.