Binding of phosphatidylinositol-3-OH kinase to CD28 is required for T-cell signalling

Nature. 1994 May 26;369(6478):327-9. doi: 10.1038/369327a0.


The engagement of CD28 with its ligand B7.1/CD80 results in potent costimulation of T-cell activation initiated through the CD3/T-cell receptor complex. The biochemical basis of CD28 costimulatory function is poorly understood. The signalling pathways used by CD28 are unlike those used by the CD3/T-cell receptor in that they are resistant to cyclosporin A and independent of changes in cyclic AMP concentrations. These differences suggest that each pathway provides unique biochemical information which is required for T-cell activation. We report here that CD28 becomes tyrosine-phosphorylated following interaction with B7.1/CD80, which induces formation of a complex with phosphatidylinositol-3-OH kinase, mediated by the SH2 domains of the p85 subunit of the kinase. Phosphatidylinositol-3-OH kinase is a heterodimer of this 85K regulatory subunit and a 110K catalytic subunit, and is a common substrate for most receptor tyrosine kinases and some cytokine receptors, binding through its SH2 domain to phosphotyrosine in the motif Tyr-X-X-Met in the CD28 sequence, which is highly conserved between human, mouse and rat and lies in the intracellular domain. We show that CD28 mutants that have their kinase-binding site deleted or the tyrosine at position 173 substituted by phenylalanine do not associate with the kinase after CD28 stimulation and cannot stimulate production of interleukin-2. Our results suggest that phosphatidylinositol-3-OH kinase is critical for signalling by CD28.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD28 Antigens / metabolism*
  • CD28 Antigens / physiology
  • Humans
  • Hybridomas
  • Immunoblotting
  • L Cells
  • Mice
  • Mutation
  • Phosphatidylinositol 3-Kinases
  • Phosphorylation
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Precipitin Tests
  • Protein Binding
  • Recombinant Fusion Proteins
  • Signal Transduction / immunology*
  • T-Lymphocytes / physiology*
  • Transfection


  • CD28 Antigens
  • Recombinant Fusion Proteins
  • Phosphotransferases (Alcohol Group Acceptor)