title: Inhibition of phosphatidylinositol 3-kinase activity by association with 14-3-3 proteins in T cells.
abstract: Proteins of the 14-3-3 family can associate with, and/or modulate the activity of, several protooncogene and oncogene products and, thus, are implicated in regulation of signaling pathways. We report that 14-3-3 is associated with another important transducing enzyme, phosphatidylinositol 3-kinase (PI3-K). A recombinant 14-3-3 fusion protein bound several tyrosine-phosphorylated proteins from antigen receptor-stimulated T lymphocytes. PI3-K was identified by immunoblotting and enzymatic assays as one of the 14-3-3-binding proteins in resting or activated cells. Moreover, endogenous 14-3-3 and PI3-K were coimmunoprecipitated from intact T cells. Far-Western blots of gel-purified, immunoprecipitated PI3-K with a recombinant 14-3-3 fusion protein revealed direct binding of 14-3-3 to the catalytic subunit (p110) of PI3-K. Finally, anti-phosphotyrosine immunoprecipitates from activated, 14-3-3-overexpressing cells contained lower PI3-K enzymatic activity than similar immunoprecipitates from control cells. These findings suggest that association of 14-3-3 with PI3-K in hematopoietic (and possibly other) cells regulates the enzymatic activity of PI3-K during receptor-initiated signal transduction.
mesh_terms: D048948:14-3-3 Proteins; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000378:metabolism; D005982:Glutathione Transferase / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D015458:Leukemia, T-Cell; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015183:Restriction Mapping; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014446:Tyrosine 3-Monooxygenase
chemical_list: D048948:14-3-3 Proteins; D017931:DNA Primers; D004791:Enzyme Inhibitors; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D014446:Tyrosine 3-Monooxygenase; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor)