FUNCTIONAL COUPLING OF THE SRC-FAMILY PROTEIN-TYROSINE KINASES P59(FYN) AND P53 56(LYN) WITH THE INTERLEUKIN-2 RECEPTOR - IMPLICATIONS FOR REDUNDANCY AND PLEIOTROPISM IN CYTOKINE SIGNAL TRANSDUCTION

The binding of interleukin 2 (IL-2) to the IL-2 receptor (IL-2R) induc es a rapid increase in tyrosine phosphorylation of cellular proteins. In a previous study, we have shown that p56lck (lck), a src-family pro tein tyrosine kinase (src-PTK), physically and functionally associates with the IL-2R beta chain (IL-2Rbeta). To further investigate a role of src-PTKs in IL-2 signaling, we analyzed a mouse pro-B-cell line, in which lck is not expressed detectably. We observed that in this cell line, IL-2 induces activation of at least two src-PTKs, p59fyn (fyn) a nd p53/56lyn (lyn). Interestingly, stimulation of this cell line with IL-3 also induces activation of src-PTKs. The activation of fyn or lyn seems to be selective for stimulation with IL-2 or IL-3 since stimula tion with IL-6 fails to activate them. Furthermore, we provide evidenc e for the physical association of fyn with IL-2Rbeta. Taken together w ith previous results, our current study suggests that different src-PT Ks, each of which is expressed in a cell-type-specific manner, can par ticipate in the IL-2 signal transduction.