Interactive sites in the MyD88 Toll/interleukin (IL) 1 receptor domain responsible for coupling to the IL1beta signaling pathway.

Li C, Zienkiewicz J, Hawiger J
J Biol Chem. 2005 280 (28): 26152-9

PMID: 15849357 · DOI:10.1074/jbc.M503262200

Myeloid differentiation factor MyD88 is the essential adaptor protein that integrates and transduces intracellular signals generated by multiple Toll-like receptors including receptor complex for interleukin (IL) 1beta, a key inflammatory cytokine. IL1beta receptor complex interacts with MyD88 via the Toll/IL1 receptor (TIR) domain. Here we report structure-function studies that help define the MyD88 TIR domain binding sites involved in IL1beta-induced protein-protein interactions. The MyD88 TIR domain, employed as a dominant negative inhibitor of IL1beta signaling to screen MyD88 TIR mutants, lost its suppressing activity upon truncation of its Box 3. Accordingly, mutations of Box 3 residues 285-286 reversed the dominant negative effect of the MyD88 TIR domain on IL1beta-induced and NFkappaB-dependent reporter gene activity and IL6 production. Moreover, mutations of residues 171 in helix alphaA, 195-197 in Box 2, and 275 in betaE-strand had similar functional effects. Strikingly, only mutations of residues 195-197 eliminated the TIR-TIR interaction of MyD88 and IL1 receptor accessory protein (IL1RAcP), whereas substitution of neighboring canonical Pro200 by His was without effect. Mutations in Box 2 and 3 prevented homotypic MyD88 oligomerization via TIR domain. Based on this structure-function analysis, a three-dimensional docking model of TIR-TIR interaction between MyD88 and IL1RAcP was developed.

MeSH Terms (38)

Adaptor Proteins, Signal Transducing Amino Acid Sequence Antigens, Differentiation Binding Sites Blotting, Western Cell Line DNA Dose-Response Relationship, Drug Fluorescent Antibody Technique, Indirect Genes, Dominant Genes, Reporter Histidine Humans Immunoprecipitation Interleukin-1 Interleukin-6 Ligands Luciferases Membrane Glycoproteins Models, Molecular Molecular Sequence Data Mutagenesis Mutagenesis, Site-Directed Mutation Myeloid Differentiation Factor 88 NF-kappa B Plasmids Proline Protein Conformation Protein Structure, Tertiary Receptors, Cell Surface Receptors, Immunologic Receptors, Interleukin-1 Sequence Homology, Amino Acid Signal Transduction Structure-Activity Relationship Toll-Like Receptors Transfection

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