Two distinct intracytoplasmic regions of the T-cell adhesion molecule CD28 participate in phosphatidylinositol 3-kinase association.
Through the interaction with its ligands, CD80/B7-1 and CD86/B7-2 or B70, the human CD28 molecule plays a major functional role as a costimulator of T cells along with the CD3-TcR complex. We and others have previously reported that phosphatidylinositol 3-kinase inducibly associates with CD28. This association is mediated by the SH2 domains of the p85 adaptor subunit interacting with a cytoplasmic YMNM consensus motif present in CD28 at position 173-176. Disruption of this binding site by site-directed mutagenesis abolishes CD28-induced activation events in a murine T-cell hybridoma transfected with human CD28 gene. Here we show that the last 10 residues of the intracytoplasmic domain of CD28 (residues 193-202) are required for its costimulatory function. These residues are involved in interleukin-2 secretion, p85 binding, and CD28-associated phosphatidylinositol 3-kinase activity. In contrast, the CD28/CD8O interaction is unaffected by this deletion, as is the induction of other second messengers such as the rise in intracellular calcium and tyrosine phosphorylation of CD28-specific substrates. Furthermore, we also demonstrate that, within these residues, the tyrosine at position 200 is involved in p85 binding, probably together with the short proline-rich motif present between residues 190 and 194 (PYAPP).
Pagès
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INSERM Unit 119, Marseille, France.
Ragueneau
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Klasen
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Battifora
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Couez
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Sweet
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Truneh
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Ward
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Olive
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D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018106:CD28 Antigens / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000032:analysis / Q000096:biosynthesis*; D007700:Kinetics; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D017354:Point Mutation; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D015290:Second Messenger Systems; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D014162:Transfection; D014443:Tyrosine; D018909:src Homology Domains
D018106:CD28 Antigens; D007376:Interleukin-2; D008024:Ligands; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011994:Recombinant Proteins; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor)