Cutting Edge: The Common γ-Chain Is an Indispensable Subunit of the IL-21 Receptor Complex

Abstract

The common γ-chain (γ_c) is an indispensable subunit of the functional receptor complexes for IL-4, IL-7, IL-9, and IL-15 as well as IL-2. Here we show that the γ_c is also shared with the IL-21R complex. Although IL-21 binds to the IL-21R expressed on γ_c-deficient ED40515⁻ cells, IL-21 is unable to transduce any intracytoplasmic signals. However, in EDγ-16 cells, a γ_c-transfected ED40515⁻ cell line, IL-21 binds to the IL-21R and can activate Janus kinase (JAK)1, JAK3, STAT1, and STAT3. The chemical cross-linking study reveals the direct binding of IL-21 to the γ_c. These data clearly demonstrate that the γ_c is an indispensable subunit of the functional IL-21R complex.