An Antagonistic Mutant of Interleukin‐4 Fails to Recruit γc into the Receptor Complex: Characterization by Specific Crosslinking

Abstract

The receptor for interleukin‐4 (IL‐4) appears to be a heterodimer of the IL‐4‐binding protein IL‐Rα and the γc chain. Mutations of IL‐4 have previously identified a region of IL‐4 essential for signaling, which was suggested to bind γc. Here it is shown by crosslinking of radiolabeled ligand and precipitation with specific antibodies that mutations in the IL‐4 signaling site prevent association of γc, but not binding to IL‐4Rα. This demonstrates that an intact signaling site of IL‐4 is required to recruit γc into the receptor complex, while specific mutants are antagonists because they fail to achieve this. Copyright © 1995, Wiley Blackwell. All rights reserved