title: T cell activation-dependent association between the p85 subunit of the phosphatidylinositol 3-kinase and Grb2/phospholipase C-gamma 1-binding phosphotyrosyl protein pp36/38.
abstract: Tyrosine phosphorylation of cellular proteins is an early and an essential step in T cell receptor-mediated lymphocyte activation. Tyrosine phosphorylation of transmembrane receptor chains (such as zeta and CD3 chains) and membrane-associated proteins provides docking sites for SH2 domains of adaptor proteins and signaling enzymes, resulting in their recruitment in the vicinity of activated receptors. pp36/38 is a prominent substrate of early tyrosine phosphorylation upon stimulation through the T cell receptor. The tyrosine-phosphorylated form of pp36/38 is membrane-associated and directly interacts with phospholipase C-gamma 1 and Grb2, providing one mechanism to recruit downstream effectors to the cell membrane. Here, we demonstrate that in Jurkat T cells, pp36/38 associates with the p85 subunit of phosphatidylinositol 3-kinase (PI-3-K p85) in an activation-dependent manner. Association of pp36/38 with PI-3-K p85 was confirmed by transfection of a hemagglutinin-tagged p85 alpha cDNA into Jurkat cells followed by anti-hemagglutinin immunoprecipitation. In vitro binding experiments with glutathione S-transferase fusion proteins of PI-3-K p85 demonstrated that the SH2 domains, but not the SH3 domain, mediated binding to pp36/38. This binding was selectively abrogated by phosphopeptides that bind to p85 SH2 domains with high affinity. Filter binding assays demonstrated that association between pp36/38 and PI-3-K p85 SH2 domains was due to direct binding. These results strongly suggest the role of pp36/38 in recruiting PI-3-K to the cell membrane and further support the idea that pp36/38 is a multifunctional docking protein for SH2 domain-containing signaling proteins in T cells.
authors.affiliation: Department of Rheumatology and Immunology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: T
authors.initials: T
authors.lastname: Fukazawa
authors.forename: K A
authors.initials: KA
authors.lastname: Reedquist
authors.forename: G
authors.initials: G
authors.lastname: Panchamoorthy
authors.forename: S
authors.initials: S
authors.lastname: Soltoff
authors.forename: T
authors.initials: T
authors.lastname: Trub
authors.forename: B
authors.initials: B
authors.lastname: Druker
authors.forename: L
authors.initials: L
authors.lastname: Cantley
authors.forename: S E
authors.initials: SE
authors.lastname: Shoelson
authors.forename: H
authors.initials: H
authors.lastname: Band
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D051380:GRB2 Adaptor Protein; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019869:Phosphatidylinositol 3-Kinases; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019000:Phosphotyrosine; D011487:Protein Conformation; D011506:Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D007527:Isoenzymes; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D010738:Type C Phospholipases; D051966:Phospholipase C gamma