Identification of two major sites in the type I interleukin-1 receptor cytoplasmic region responsible for coupling to pro-inflammatory signaling pathways

Type I interleukin-1 receptor is the prototype for a family of proteins, wh ich play a central role in early responses to injury and infection, The sim ilarity of function across the family is reflected in similarity in signali ng: all members tested couple to activation of NF kappa B and stress kinase s. The coupling to these pathways is mediated by a 200-residue intracellula r domain (the Toll/interleukin-l receptor domain), in which sequence conser vation is primarily confined to three short motifs (boxes 1, 2, and 3) loca ted at amino acid residue positions 10 (box 1), 60 (box 2), and 170 (box 3) . We have analyzed the contribution of these motifs to function by alanine scanning mutagenesis of the human interleukin-1 receptor type I. Mutant rec eptors were tested for expression, ligand binding, activation of receptor-a ssociated kinase(s), NF kappa B, stress kinases, and transcription. Mutatio ns in all three motifs led to low cell surface expression. Mutants in box 3 were, however, wild type for signaling, whereas mutants in boxes 1 and 2 w ere defective. We conclude that the conserved motifs box 1 and box 2 mediat e the coupling of molecules in the family to inflammation signaling pathway s.