Interleukin-4 (IL-4) induces protein tyrosine phosphorylation of the IL-4 receptor and association of phosphatidylinositol 3-kinase to the IL-4 receptor in a mouse T cell line, HT2

To study the signal transduction mechanism of interleukin-4 (IL-4), we have examined the effects of IL-4 on protein tyrosine phosphorylation in a mouse IL-2-dependent T cell line, HT2. Mouse IL-4 induces HT2 proliferation in a dose-dependent manner. Western blotting analyses using anti-phosphotyrosine antibody showed that IL-4 induces tyrosine phosphorylation of four proteins (140, 110, 100, and 92 kDa) in a dose-dependent manner. Protein tyrosine phosphorylation was detected within 1 min and reached a plateau approximately at 10 min after IL-4 stimulation. Immunoprecipitation using anti-IL-4 receptor antibody revealed that the 140-kDa tyrosine-phosphorylated protein is the IL-4 receptor (IL-4R) itself. Furthermore, we demonstrate that phosphatidylinositol 3-kinase (PI 3-kinase) activity in immunoprecipitates with anti-IL-4R antibody increases after IL-4 stimulation. These data indicate that IL-4 induces activation of tyrosine kinase and also induces association between IL-4R and PI 3-kinase.