Cell Signal. 2009 May;21(5):719-26. Epub 2009 Jan 7.

Regulation of IRAK-1 activation by its C-terminal domain.External

Nguyen, T., De Nardo, D., Masendycz, P., Hamilton, J. A., Scholz, G. M.,
--- - Department of Medicine and Cooperative Research Centre for Chronic Inflammatory Diseases, The University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
Macrophages are important mediators of the immune response to infection by virtue of their ability to secrete cytokines that trigger inflammation. Toll-like receptors (TLRs) are largely responsible for meditating the activation of macrophages by pathogens. IRAK-1 is a proximal protein kinase in TLR signalling pathways and hence its activation must be tightly regulated. However, the mechanisms which control the activation of IRAK-1 are poorly understood. IRAK-1 contains a death domain at its N-terminus that mediates its interaction with other death domain containing proteins, a central Ser/Thr kinase domain, and a C-terminal domain that contains binding motifs for TRAF6. We show here that deletion of the death domain or the majority of the C-terminal domain markedly enhanced the capacity of IRAK-1 to activate NF-kappaB in a TLR-independent manner in RAW 264.7 macrophages. Furthermore, the C-terminal truncation mutant spontaneously oligomerised and formed complexes with the negative regulator IRAK-M in the absence of TLR activation. In contrast to the binding of IRAK-M to IRAK-1, the death domain of IRAK-1 was not required for the interaction of IRAK-4 with IRAK-1. On the basis of these results we propose a model in which IRAK-1 is held in a closed, inactive conformation via an intramolecular mechanism involving its C-terminal domain and possibly the death domain. Phosphorylation of IRAK-1 by IRAK-4 in response to TLR activation may then release IRAK-1 from the inhibitory constraint exerted by its C-terminal domain.
PMID: 19166926External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
DD IRAK1 Link IRAK1 Co-immunoprecipitation HEK293 Mouse 1-550 Mouse 1-550 19166926
DD IRAK1 Link IRAK3 Co-immunoprecipitation HEK293 Mouse 1-550 Not specified Not specified 19166926
DD IRAK1 Link IRAK3 Co-immunoprecipitation Mouse RAW 264.7 macrophage Mouse 1-550 Not specified Not specified 19166926
(Link: click this icon to show interactions only between the two corresponding DDs)