Identification of the protein kinases that activate the E3 ubiquitin ligase Pellino 1 in the innate immune system.
The E3 ubiquitin ligase Pellino 1 can be interconverted between inactive and active forms by a reversible phosphorylation mechanism. In vitro, phosphorylation and activation can be catalysed by either the IRAKs [IL (interleukin)-1-receptor-associated kinases] IRAK1 and IRAK4, or the IKK {IκB [inhibitor of NF-κB (nuclear factor κB)] kinase}-related kinases [IKKϵ and TBK1 (TANK {TRAF [TNF (tumour-necrosis-factor)-receptor-associated factor]-associated NF-κB activator}-binding kinase 1)]. In the present study we establish that IRAK1 is the major protein kinase that mediates the IL-1-stimulated activation of Pellino 1 in MEFs (mouse embryonic fibroblasts) or HEK (human embryonic kidney)-293 cells, whereas the IKK-related kinases activate Pellino 1 in TNFα-stimulated MEFs. The IKK-related kinases are also the major protein kinases that activate Pellino 1 in response to TLR (Toll-like receptor) ligands that signal via the adaptors MyD88 (myeloid differentiation primary response gene 88) and/or TRIF [TIR (Toll/IL-1 receptor) domain-containing adaptor protein inducing interferon β]. The present studies demonstrate that, surprisingly, the ligands that signal via MyD88 do not always employ the same protein kinase to activate Pellino 1. Our results also establish that neither the catalytic activity of IRAK1 nor the activation of Pellino 1 is required for the initial transient activation of NF-κB and MAPKs (mitogen-activated protein kinases) that is triggered by IL-1 or TNFα in MEFs, or by TLR ligands in macrophages. The activation of Pellino 1 provides the first direct readout for IRAK1 catalytic activity in cells.
MRC Protein Phosphorylation Unit and Scottish Institute for Cell Signalling, Sir James Black Centre, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
Eddy T H
ET
Goh
J Simon C
JS
Arthur
Peter C F
PC
Cheung
Shizuo
S
Akira
Rachel
R
Toth
Philip
P
Cohen
D000818:Animals; D005347:Fibroblasts / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D051193:Toll-Like Receptors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D008024:Ligands; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D009687:Nuclear Proteins; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; C485959:PELI1 protein, human; D044767:Ubiquitin-Protein Ligases; D053592:Interleukin-1 Receptor-Associated Kinases; C418046:Peli1 protein, mouse