Description
The biological activity of IL-13 is regulated via the IL-13R type I and type II. The type I receptor is a heterodimer of the IL-4R α chain (IL-4Rα) and IL-13Rα1, and ligand-receptor interactions induce phosphorylation of the IL- 4Rα and subsequent activation of the signal transducers and activators of transcription (STAT) -6 signaling pathway. This pathway appears to be the primary pathway for IL-13- induced signaling in nonhematopoietic cells. The type II receptor is composed of IL-13Rα1 and IL-13Rα2. IL-13Rα2 binds IL-13 with high affinity and is proposed to act as a decoy receptor that limits the activity of IL-13. Consistent with this, mice deficient in IL-13Rα2 demonstrate exaggerated IL- 13-induced pathologies. IL- 13Rα2 possesses a short cytoplasmic tail and is without signal motifs; however, there have been a number of reports to suggest IL-13 signals through this chain, possibly via a STAT6- independent, AP-1-dependent manner to induce activation of the Tgfβ1 promoter via the IL-13 type II receptor