REGULATION OF SRC-FAMILY PROTEIN TYROSINE KINASES BY INTERLEUKINS, IL-2, AND IL-3

Unlike many other growth factor receptors, the known subunits of the receptors for the Interleukins IL-2 and IL-3 lack intrinsic tyrosine kinase activity, and yet increases in the phosphorylation of proteins on tyrosines is a rapid event in hematolymphoid cells following stimulation with these lymphokines. Here we show that IL-2 and IL-3 regulate the activity of specific members of the SRC-family or non-receptor protein tyrosine kinases (PTKs). In IL-2-dependent T-cell lines, IL-2 induced rapid and transient increases in the activity of the p56-LCK kinase without influencing the activities of other SRC-like PTKs (p59-FYN, p62-YES) in these T-lymphocytes. In contrast to IL-2's effects on p56-LCK in T-cells, studies of an IL-2-responsive cell line of the B-cell lineage that lacks p56-LCK revealed that IL-2 specifically regulates the activity of the p53/56-LYN kinase. Thus, some flexibility exists in the ability or various SRC-like PTKs to functionally couple to IL-2 signalling pathways. In several IL-3-dependent myeloid-committed leukemic cell lines, IL-3 was found to specifically regulate the activity of the p53/56-LYN kinase without affecting the activities of other SRC-like PTKs (p59/64-HCK, p59-FYN, p62-YES) in these hematopoietic cells. This finding that p53/56-LYN can be regulated by both IL-2 in B-lineage cells and IL-3 in myeloid-committed cells demonstrates that the same SRC-family PTK can participate in signal transduction events mediated via two independent receptor systems. Taken together, our findings imply that the specific combinations of lymphokine receptors and SRC-like PTKs available for coupling with those receptors are coordinately controlled during the differentiation or hematopoietic cells.