The Src-family kinase, Fyn, regulates the activation of phosphatidylinositol 3-kinase in an interleukin 2-responsive T cell line.
The proliferation of antigen-activated T cells is mediated by the T cell-derived growth factor, interleukin 2 (IL-2). The biochemical signaling cascades initiating IL-2-induced growth are dependent upon protein tyrosine kinase (PTK) activity. One IL-2-regulated PTK implicated in this cascade is the Src-family kinase, Fyn. Previous studies have described a physical association between Fyn and a potential downstream substrate, phosphatidylinositol 3-kinase (PI3-kinase) as well as the IL-2-dependent activation of PI3-kinase in T cells; however, the role of Fyn in IL-2-induced PI3-kinase activation remains unclear. In this report, we demonstrate that IL-2 stimulation triggers tyrosine phosphorylation of the p85 subunit of PI3-kinase in the murine T cell line, CTLL-2. Lysates prepared from growth factor-deprived and IL-2-stimulated T cells reconstituted both the binding of CTLL-2 cell-derived Fyn to and the IL-2-inducible tyrosine phosphorylation of exogenously added recombinant p85. Furthermore, overexpression of wild-type Fyn in these cells enhanced both the basal and IL-2-mediated activation of PI3-kinase. Additional studies of the Fyn-PI3-kinase interaction demonstrated that the Src homology 3 (SH3) domain of Fyn constitutes a direct binding site for the p85 subunit of PI3-kinase. These results support the notion that Fyn may be directly involved in the activation of the downstream signaling enzyme, PI3-kinase, in IL-2-stimulated T cells.
Karnitz
L M
LM
Department of Immunology, Mayo Clinic, Rochester, Minnesota 55905.
Sutor
S L
SL
Abraham
R T
RT
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D004789:Enzyme Activation; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000378:metabolism; D007376:Interleukin-2 / Q000494:pharmacology*; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D019000:Phosphotyrosine; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D017931:DNA Primers; D007376:Interleukin-2; D046911:Macromolecular Substances; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn