SH2-dependent Association of Phosphatidylinositol 3′-Kinase 85-kDa Regulatory Subunit with the Interleukin-2 Receptor β Chain

Interleukin-2 (IL-2) signaling results in tyrosine phosphorylation of the 75-kDa IL-2 receptor (IL-2R) β chain and the activation of phosphatidylinositol 3′-kinase (PI3-K). Herein, we demonstrate that the 85-kDa (p85) regulatory subunit of PI3-K physically associates with the tyrosine-phosphorylated IL-2R β chain. A fusion protein containing both the amino- and the carboxyl-terminal src homology 2 domains of p85 precipitates an 80-kDa tyrosine-phosphorylated protein (pp80) from the lysates of IL-2-stimulated, but not unstimulated, human T lymphoblasts. Preclearing studies and immunoblotting with an antiserum to the IL-2R β chain demonstrates that pp80 represents a portion of the IL-2R β chain pool. A tyrosine-phosphorylated oligopeptide corresponding to tyrosine 392 of the IL-2R β chain partially inhibits binding of the IL-2R β chain by p85 fusion protein, raising the possibility that this residue plays a role in the interaction of PI3-K with the receptor.