RESUMO
Signal transduction by the IL-36 receptor (IL-36R) is linked to several human diseases. However, the structure and function of the IL-36R is not well understood. A molecular model of the IL-36R complex was generated and a cell-based reporter assay was established to assess the signal transduction of recombinant subunits of the IL-36R. Mutational analyses and functional assays have identified residues of the receptor subunit IL-1Rrp2 needed for cytokine recognition, stable protein expression, disulfide bond formation and glycosylation that are critical for signal transduction. We also observed that, overexpression of ectodomain (ECD) of Il-1Rrp2 or IL-1RAcP exhibited dominant-negative effect on IL-36R signaling. The presence of IL-36 cytokine significantly increased the interaction of IL-1Rrp2 ECD with the co-receptor IL-1RAcP. Finally, we found that single nucleotide polymorphism A471T in the Toll-interleukin 1 receptor domain (TIR) of the IL-1Rrp2 that is present in â¼2% of the human population, down-regulated IL-36R signaling by a decrease of interaction with IL-1RAcP.
Assuntos
Proteína Acessória do Receptor de Interleucina-1 , Subunidade alfa de Receptor de Interleucina-18 , Polimorfismo Genético , Células HEK293 , Humanos , Proteína Acessória do Receptor de Interleucina-1/química , Proteína Acessória do Receptor de Interleucina-1/genética , Proteína Acessória do Receptor de Interleucina-1/metabolismo , Subunidade alfa de Receptor de Interleucina-18/química , Subunidade alfa de Receptor de Interleucina-18/genética , Subunidade alfa de Receptor de Interleucina-18/metabolismo , Domínios Proteicos , Transdução de Sinais , Relação Estrutura-AtividadeRESUMO
Interleukin 18 (IL-18), a member of the IL-1 family of cytokines, is an important regulator of innate and acquired immune responses. It signals through its ligand-binding primary receptor IL-18Rα and accessory receptor IL-18Rß. Here we report the crystal structure of IL-18 with the ectodomain of IL-18Rα, which reveals the structural basis for their specific recognition. It confirms that surface charge complementarity determines the ligand-binding specificity of primary receptors in the IL-1 receptor family. We suggest that IL-18 signaling complex adopts an architecture similar to other agonistic cytokines and propose a general ligand-receptor assembly and activation model for the IL-1 family.