In the interleukin-2 (IL-2) system, intracellular signal transduction is triggered by the β chain of the IL-2 receptor (IL-2Rβ); however, the responsible signaling mechanism remains unidentified. Evidence for the formation of a stable complex of IL-2Rβ and the lymphocyte-specific protein tyrosine kinase p56 lck is presented. Specific association sites were identified in the tyrosine kinase catalytic domain of p56 lck and in the cytoplasmic domain of IL-2Rβ. As a result of interaction, IL-2Rβ became phosphorylated in vitro by p56 lck . Treatment of T lymphocytes with IL-2 promotes p56 lck kinase activity. These data suggest the participation of p56 lck as a critical signaling molecule downstream of IL-2R via a novel interaction.

Interaction of the IL-2 Receptor with thesrc-Family Kinase p56lck: Identification of Novel Intermolecular Association