T cell activation-dependent association between the p85 subunit of the phosphatidylinositol 3-kinase and Grb2/phospholipase C-γ1-binding phosphotyrosyl protein pp36/38

T. Fukazawa, K. A. Reedquist, G. Panchamoorthy, S. Soltoff, T. Trub, B. Druker, L. Cantley, S. E. Shoelson, H. Band

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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 ζ 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-γ1 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 p85α cDNA into Jurkat cells followed by antihemagglutinin 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.

Original languageEnglish (US)
Pages (from-to)20177-20182
Number of pages6
JournalJournal of Biological Chemistry
Issue number34
StatePublished - Jan 1 1995


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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