DEMONSTRATION OF A CROSS-TALK BETWEEN IL-2 AND IL-5 IN PHOSPHORYLATION OF IL-2 AND IL-5 RECEPTOR-BETA CHAINS

We have examined phosphorylation mediated by cross-talk between growth signal pathways induced by IL-2 and IL-5. To analyze the phosphorylat ion process in the same cells, we established two sublines, T88-M beta 1, which is a subline of a murine IL-5-dependent cell line, T88-M, by introduction of the human IL-2 receptor beta chain (IL-2R beta), and secondly CTLL-5R alpha beta, which is a subline of a murine IL-2-depen dent cell line, CTLL-2, by introduction of the murine IL-5 receptor a chain (IL-5R alpha) and IL-5 receptor beta chain (IL-5R beta, beta c) genes, Both T88-M beta 1 and CTLL-5R alpha beta expressed high-affinit y receptors for IL-2 and IL-5, and proliferated in response to both fa ctors, Tyrosine phosphorylation of IL-2R beta was induced by stimulati on of T88-M beta 1 with not only IL-2 but also IL-5. Anti-IL-SRP-direc ted immune complexes from T88-M beta 1 stimulated with IL-5 as well as with IL-2 contained an activated tyrosine kinase, However, stimulatio n with IL-5 but not IL-2 induced the tyrosine phosphorylation of IL-5R beta, beta c, suggesting that IL-2 does not activate a tyrosine kinas e which efficiently catalyzes the IL-5R beta molecule in response to I L-5, On the other hand, the detection of JAK1 and the other common set of phosphotyrosine-containing proteins after stimulation with either IL-5 or IL-2 suggests the existence of the same tyrosine phosphorylati on pathways.