Interleukin-1 (IL-1) Induces the Lys63-Linked Polyubiquitination of IL-1 Receptor-Associated Kinase 1 To Facilitate NEMO Binding and the Activation of IκBα Kinase

Abstract

Interleukin 1 (IL-1) has been reported to stimulate the polyubiquitination and disappearance of IL-1 receptor-associated kinase 1 (IRAK1) within minutes. It has been thought that the polyubiquitin chains attached to IRAK1 are linked via Lys48 of ubiquitin, leading to its destruction by the proteasome and explaining the rapid IL-1-induced disappearance of IRAK1. In this paper, we demonstrate that IL-1 stimulates the formation of K63-pUb-IRAK1 and not K48-pUb-IRAK1 and that the IL-1-induced disappearance of IRAK1 is not blocked by inhibition of the proteasome. We also show that IL-1 triggers the interaction of K63-pUb-IRAK1 with NEMO, a regulatory subunit of the IκBα kinase (IKK) complex, but not with the NEMO[D311N] mutant that cannot bind K63-pUb chains. Moreover, unlike wild-type NEMO, the NEMO[D311N] mutant was unable to restore IL-1-stimulated NF-κB-dependent gene transcription to NEMO-deficient cells. Our data suggest a model in which the recruitment of the NEMO-IKK complex to K63-pUb-IRAK1 and the recruitment of the TAK1 complex to TRAF6 facilitate the TAK1-catalyzed activation of IKK by the TRAF6-IRAK1 complex.

ACKNOWLEDGMENTS

We thank David Lane (University of Dundee, Scotland) for providing vectors for the expression of tagged ubiquitin and ubiquitin mutant forms, Shizuo Akira (Osaka University, Japan) for TAK1^−/− cells, Manolis Pasparakis (University of Cologne, Germany) for NEMO^−/− cells, and Tak Mak (University of Toronto, Canada) for TRAF6^−/− cells.

Mark Windheim acknowledges a postdoctoral position from the EU Research Training Framework 5 Programme. This work was supported by the UK Medical Research Council, The European Union Framework 5 program, AstraZeneca, Boehringer Ingelheim, GlaxoSmithKline, Merck and Co., Merck KGaA, and Pfizer.