Identification of essential regions in the cytoplasmic tail of interleukin-1 receptor accessory protein critical for interleukin-1 signaling.
Interleukin (IL)-1 plays an important role in inflammation and regulation of immune responses. The activated IL-1 receptor complex, which consists of the IL-1 receptor type I and the IL-1 receptor accessory protein (IL-1RAcP), generates multiple cellular responses including NF-kappaB activation, IL-2 secretion, and IL-2 promoter activation. Reconstitution experiments in EL4D6/76 cells lacking IL-1RAcP expression and IL-1 responsiveness were used to analyze structure-function relationships of the IL-1RAcP cytoplasmic tail. Mutating a potential tyrosine kinase phosphorylation motif and various conserved amino acid (aa) residues had no effect on IL-1 responsiveness. Truncation analyses revealed that box 3 of the TIR domain was required for NF-kappaB activation, IL-2 production, and c-Jun N-terminal kinase (JNK) activation, whereas IL-2 promoter activation was only partially inhibited. Surprisingly, deletion of aa 527-534 resulted in almost complete loss of all IL-1 responsiveness. Replacement of these aa with alanyl residues did not reconstitute NF-kappaB activation, IL-2 production, or JNK activation but partly restored IL-2 promoter activation. Immunoprecipitation data revealed a strong correlation between MyD88 binding with NF-kappaB activation and IL-2 production but not with IL-2 promoter activation. Taken together, our data indicate that box 3 of IL-1RAcP is critical for IL-1-dependent NF-kappaB activation and stabilization of IL-2 mRNA via JNK, whereas aa 527-534 largely contribute to IL-2 promoter activation.
Radons
Jurgen
J
Klinik und Poliklinik für Innere Medizin I, Universität Regensburg, D-93042 Regensburg, Germany. juergen.radons@klinik.uni-regensburg.de
Gabler
Stefan
S
Wesche
Holger
H
Korherr
Christian
C
Hofmeister
Robert
R
Falk
Werner
W
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism*; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D017353:Gene Deletion; D017930:Genes, Reporter; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism*; D053577:Interleukin-1 Receptor Accessory Protein; D007376:Interleukin-2 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000502:physiology*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013997:Time Factors; D014162:Transfection
C507765:IL1RAP protein, human; C507767:Il1rap protein, mouse; D007375:Interleukin-1; D053577:Interleukin-1 Receptor Accessory Protein; D007376:Interleukin-2; D016328:NF-kappa B; D011506:Proteins; D008156:Luciferases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases