CLONING OF THE HUMAN IL-13R-ALPHA-1 CHAIN AND RECONSTITUTION WITH THEIL-4R-ALPHA OF A FUNCTIONAL IL-4 IL-13 RECEPTOR COMPLEX/

The human homologue of the recently cloned murine IL-13 binding protei n (IL-13R alpha 1) was cloned from a cDNA library derived from the car cinoma cell line CAKI-1, The cloned cDNA encodes a 427 amino acid prot ein with tao consensus patterns characteristic of the hematopoietic cy tokine receptor family and a short cytoplasmic tail, The human protein is 74% identical to the murine IL-13R alpha 1, and 27% identical to t he human IL-13R alpha 2. CHO cells expressing recombinant hIL-13R alph a 1 specifically bind IL-13 (K-d approximate to 4 nM) but not IL-4. Co expression of the cloned cDNA with that of IL-4R alpha resulted in a r eceptor complex that displayed high affinity for IL-13 (K-d approximat e to 30 pM), and that allowed cross-competition of IL-13 and IL-4. Ele ctrophoretic mobility shift assay showed that IL-13 and IL-4 were able to activate Stat6 in cells expressing both IL-4R alpha and IL-13R alp ha 1, while no activation was observed in cells expressing either one or the other alone.