Reconstitution of functional interleukin 2 receptor complexes on fibroblastoid cells: Involvement of the cytoplasmic domain of the γ chain in two distinct signaling pathways

We have previously shown that the interleukin 2 (IL-2) receptor γ chain is a member of the cytokine receptor superfamily and is indispensable for the formation of receptor complexes with high and intermediate affinities for IL-2. The present study demonstrates that the αβγ heterotrimer and βγ heterodimer complexes of IL-2 receptor reconstituted on murine fibroblast L929 cells can transduce IL-2-mediated signals for activation of tyrosine kinase and for induction of c-myc, c-fos, and c-jun expression. A mutant of the γ chain lacking the C-terminal 68 amino acids in its cytoplasmic region showed a loss of such signal-transducing ability when incorporated into the IL-2 receptor complexes but brought no effect on IL-2 binding and IL-2 internalization. Another mutant, with a C-terminal deletion of 30 amino acids, retained the ability to activate a tyrosine kinase and to induce c-myc expression but lost the ability to induce c-fos and c-jun expression. These results suggest that at least two distinct signals, one for c-myc induction, which parallels tyrosine kinase activation, and the other for c-fos and c-jun induction, can be transduced from the IL-2 receptor complexes reconstituted on fibroblastoid cells.