Mutant cells that do not respond to interleukin-1 (IL-1) reveal a novel role for IL-1 receptor-associated kinase.
Mutagenized human 293 cells containing an interleukin-1 (IL-1)-regulated herpes thymidine kinase gene, selected in IL-1 and gancyclovir, have yielded many independent clones that are unresponsive to IL-1. The four clones analyzed here carry recessive mutations and represent three complementation groups. Mutant A in complementation group I1 lacks IL-1 receptor-associated kinase (IRAK), while the mutants in the other two groups are defective in unknown components that function upstream of IRAK. Expression of exogenous IRAK in I1A cells (I1A-IRAK) restores their responsiveness to IL-1. Neither NFkappaB nor Jun kinase is activated in IL-1-treated I1A cells, but these responses are restored in I1A-IRAK cells, indicating that IRAK is required for both. To address the role of the kinase activity of IRAK in IL-1 signaling, its ATP binding site was mutated (K239A), completely abolishing kinase activity. In transfected I1A cells, IRAK-K239A was still phosphorylated upon IL-1 stimulation and, surprisingly, still complemented all the defects in the mutant cells. Therefore, IRAK must be phosphorylated by a different kinase, and phospho-IRAK must play a role in IL-1-mediated signaling that does not require its kinase activity.
Li
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X
Department of Molecular Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Commane
M
M
Burns
C
C
Vithalani
K
K
Cao
Z
Z
Stark
G R
GR
D002461:Cell Line, Transformed; D005816:Genetic Complementation Test; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism* / Q000494:pharmacology; D053592:Interleukin-1 Receptor-Associated Kinases; D016296:Mutagenesis; D010641:Phenotype; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism* / Q000502:physiology; D017472:Receptors, Interleukin-1 / Q000378:metabolism*; D015398:Signal Transduction; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics
D007375:Interleukin-1; D017472:Receptors, Interleukin-1; D011494:Protein Kinases; D013937:Thymidine Kinase; D053592:Interleukin-1 Receptor-Associated Kinases