cDNA Cloning and Characterization of the Human Interleukin 13 Receptor α Chain

We have cloned cDNAs corresponding to the human interleukin 13 receptor α chain (IL-13Rα). The protein has 76% homology to murine IL-13Rα, with 95% amino acid identity in the cytoplasmic domain. Only weak IL-13 binding activity was found in cells transfected with only IL-13Rα; however, the combination of both IL-13Rα and IL-4Rα resulted in substantial binding activity, with a Kd of approximately 400 pM, indicating that both chains are essential components of the IL-13 receptor. Whereas IL-13Rα serves as an alternative accessory protein to the common cytokine receptor γ chain (γc) for IL-4 signaling, it could not replace the function of γc in allowing enhanced IL-2 binding activity. Nevertheless, the overall size and length of the cytoplasmic domain of IL-13Rα and γc are similar, and like γc, IL-13Rα is located on chromosome X. We have cloned cDNAs corresponding to the human interleukin 13 receptor α chain (IL-13Rα). The protein has 76% homology to murine IL-13Rα, with 95% amino acid identity in the cytoplasmic domain. Only weak IL-13 binding activity was found in cells transfected with only IL-13Rα; however, the combination of both IL-13Rα and IL-4Rα resulted in substantial binding activity, with a Kd of approximately 400 pM, indicating that both chains are essential components of the IL-13 receptor. Whereas IL-13Rα serves as an alternative accessory protein to the common cytokine receptor γ chain (γc) for IL-4 signaling, it could not replace the function of γc in allowing enhanced IL-2 binding activity. Nevertheless, the overall size and length of the cytoplasmic domain of IL-13Rα and γc are similar, and like γc, IL-13Rα is located on chromosome X.