A restricted cytoplasmic region of IL-2 receptor β chain is essential for growth signal transduction but not for ligand binding and internalization

Abstract

The functional, high affinity form of interleukin-2 receptor (IL-2R) is composed of two receptor components, the IL-2Rα (p55) and IL-2Rβ (p70–75) chains. Unlike the IL-2Rα chain, the IL-2Rβ chain contains a large cytoplasmic domain that shows no obvious tyrosine kinase motif. In the present study, we report the establishment of a system in which the cDNA-directed human IL-2Rβ allows growth signal transduction in a mouse pro-B cell line. This system enabled us to identify a unique region within the cytoplasmic domain of the human IL-2Rβ chain essential for ligand-mediated signal transduction. We also demonstrate that certain cytoplasmic deletion mutants in the IL-2Rβ chain, although deficient in signal transduction, can still form high affinity IL-2R in conjunction with endogenous mouse IL-2Rα chain; the mutants are still able to internalize the ligand as well.