FIGURE 6.

Loss of binding and signal transduction of IL-13, but not IL-4 in the mutants of Trp-65, Lys-76, Lys-77, Ile-78, and Ala-79 in IL-13Rα1. The wild type or the indicated mutated type of IL-13Rα1 alone (A and B) or the wild type of IL-4Rα and the wild type or the indicated mutated type of IL-13Rα1 (C and D) were transfected into HEK 293T cells. Expression of IL-13Rα1 (A) or IL-4Rα (C) on the surface of HEK 293T cells by flow cytometry using anti-FLAG Ab or anti-CD124 Ab, respectively, is shown. The shaded and open areas represent the expression of the indicated transfectant or mock transfectant, respectively. Binding of ¹²⁵I-labeled IL-13 (B) or IL-4 (D) to HEK 293T cells is depicted. E, the luciferase activities by IL-13 or by IL-4 are shown. The cells were stimulated with 0.01 ng/ml IL-13 or IL-4 for 6 h. The relative luciferase activities of each mutant are calculated from that of the wild type.