IL-2-DEPENDENT INVIVO AND INVITRO TYROSINE PHOSPHORYLATION OF IL-2 RECEPTOR GAMMA CHAIN

We previously reported a molecule, p64, which was tentatively named the gamma-chain, coprecipitable with the beta-chain of human interleukin-2 receptor (IL-2R). The present study demonstrated that the gamma-chain, as well as the beta-chain expressed on IL-2-responsive cells, is phosphorylated on tyrosine residues in an IL-2-dependent manner in vivo and in vitro. The in vivo tyrosine phosphorylation of both chains was similarly induced within 1 min after IL-2 stimulation, and their in vitro tyrosine phosphorylation with the anti-IL-2R-beta antibody-directed immunocomplex was also increased by treatment of cells with IL-2. These results suggest that a tyrosine kinase is associated with the beta-gamma subunit complex, of which activation by IL-2 may result in transduction of intracellular signals.