β-TrCP-Mediated IRAK1 Degradation Releases TAK1-TRAF6 from the Membrane to the Cytosol for TAK1-Dependent NF-κB Activation

Interleukin-1 (IL-1) receptor-associated kinase (IRAK1) is phosphorylated, ubiquitinated, and degraded upon IL-1 stimulation. IRAK1 can be ubiquitinated through both K48- and K63-linked polyubiquitin chains upon IL-1 stimulation. While the Pellino proteins have been shown to meditate K63-linked polyubiquitination on IRAK1, the E3 ligase for K48-linked ubiquitination of IRAK1 has not been identified. In this study, we report that the SCF (Skp1-Cullin1-F-box)-beta-TrCP complex functions as the K48-linked ubiquitination E3 ligase for IRAK1. IL-1 stimulation induced the interaction of IRAK1 with Cullin1 and beta-TrCP. Knockdown of beta-TrCP1 and beta-TrCP2 attenuated the K48-linked ubiquitination and degradation of IRAK1. Importantly, beta-TrCP deficiency abolished the translocation TAK1-TRAF6 complex from the membrane to the cytosol, resulting in a diminishment of the IL-1-induced TAK1-dependent pathway. Taken together, these results implicate a positive role of beta-TrCP-mediated IRAK1 degradation in IL-1-induced TAK1 activation.