Lys63-linked polyubiquitination of IRAK-1 is required for interleukin-1 receptor- and Toll-like receptor-mediated NF-κB activation

Stimulation through the interleukin-1 receptor (IL-1R) and some Toll-like receptors (TLRs) induces ubiquitination of TRAF6 and IRAK-1, signaling components required for NF-kappa B and mitogen-activated protein kinase activation. Here we show that although TRAF6 and IRAK-I acquired Lys63 (K63)-linked polyubiquitin chains upon IL-1 stimulation, only ubiquitinated IRAK-1 bound NEMO, the regulatory subunit Of I kappa B kinase (IKK). The sites of IRAK-1 ubiquitination were mapped to Lys134 and Lys][80, and arginine substitution of these residues impaired IL-IR/TLR-mediated IRAK-1 ubiquitination, NEMO binding, and NF-kappa B activation. K63-linked ubiquitination of IRAK-1 required enzymatically active TRAF6, indicating that it is the physiologically relevant E3. Thus, K63-linked polyubiquitination of proximal signaling proteins is a common mechanism used by diverse innate immune receptors for recruiting IKK and activating NF-kappa B.