Expression and characterization of interleukin-13 receptor 2 chain (IL-13R2)

Matsumoto, Fumiko; Tamada, Taro; Honjo, Eijiro*; Ota, Shoichiro*; Izuhara, Kenji*; Kuroki, Ryota

The allergic disease has dramatically increased in recent years. Interleukin-13 (IL-13) is a key cytokine critical to the development of T-cell-mediated humoral immune responses which are associated with allergy and asthma. IL-13 possesses two types of receptor: the heterodimer, composed of IL-13R1 and IL-4R, transducing the IL-13 signals; and the IL-13R2, acting as a nonsignaling "decoy" receptor. Although the extracellular region of IL-13R1 and IL-13R2 are composed of a common structure of the class 1 cytokine receptor superfamily and they have similar amino acid sequence, the affinity of IL-13R2 with IL-13 is more than ten-fold higher than that of IL-13R1. In order to investigate the reason for this higher ligand affinity to IL-13R2, extra cellular region of IL-13R2 was expressed by silkworm-baculovirus expression system after fusing the DNA cording the extracellular region of human IL-13R2 with the Fc derived from mouse IgG2a. The expressed fusion protein IL-13R2-Fc was purified by a protein G column, and the affinity to IL-13 was confirmed by gel filtration followed by light scattering analysis. After Fc region was removed by thrombin digestion, the resulting extra cellular region of IL-13R2 receptor was confirmed to retain strong affinity to IL-13 with 1:1 ratio.