Regulation of phosphoinositide kinases in T cells. Evidence that phosphatidylinositol 3-kinase is not a substrate for T cell antigen receptor-regulated tyrosine kinases.
A phosphoinositide kinase that can phosphorylate phosphatidylinositol (PtdIns) is present in 4G10 monoclonal antibody (mAb) phosphotyrosine immunoprecipitates isolated from T cells activated via the T cell antigen receptor (TCR).CD3 complex. This PtdIns kinase is not the PtdIns 3-kinase that associates with activated protein tyrosine kinases in fibroblasts, since Western blotting and immunoprecipitation experiments with antibodies specific for the p85 alpha subunit of the PtdIns 3-kinase indicate that this polypeptide is not immunoprecipitated by the 4G10 mAb from TCR.CD3-activated Jurkat cells. Moreover, immunoprecipitated PtdIns 3-kinase isolated from T cells with p85 antibodies is inhibited when PtdIns is presented in Nonidet P-40, whereas the PtdIns kinase activity present in 4G10 mAb phosphotyrosine immunoprecipitates is enhanced in the presence of Nonidet P-40. In vitro kinase assays of PtdIns 3-kinase immunoprecipitated with p85 antibodies from T cells indicate that it associates with a serine kinase that can phosphorylate a p85 polypeptide. However, no protein tyrosine kinase activity capable of tyrosine phosphorylating p85 in vitro associates with p85 alpha immunoprecipitates in quiescent or TCR.CD3-activated T cells. These data suggest that the TCR.CD3 complex does not regulate PtdIns 3-kinase activity by a mechanism that involves protein tyrosine kinases.
Ward
S G
SG
Lymphocyte Activation Laboratory, Imperial Cancer Research Fund, Lincoln's Inn Fields, London, United Kingdom.
Reif
K
K
Ley
S
S
Fry
M J
MJ
Waterfield
M D
MD
Cantrell
D A
DA
D000241:Adenosine / Q000494:pharmacology; D000596:Amino Acids / Q000032:analysis; D000906:Antibodies; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D017252:CD3 Complex / Q000378:metabolism*; D002460:Cell Line; D003902:Detergents / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D017830:Octoxynol; D019869:Phosphatidylinositol 3-Kinases; D010770:Phosphotransferases / Q000378:metabolism*; D019000:Phosphotyrosine; D011092:Polyethylene Glycols / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D000241:Adenosine; D000596:Amino Acids; D000906:Antibodies; D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D003902:Detergents; D046911:Macromolecular Substances; D017830:Octoxynol; D019869:Phosphatidylinositol 3-Kinases; D010770:Phosphotransferases; D019000:Phosphotyrosine; D011092:Polyethylene Glycols; D011505:Protein-Tyrosine Kinases; D011948:Receptors, Antigen, T-Cell; D014443:Tyrosine; C010615:Nonidet P-40