CD28 co-stimulatory regimes differ in their dependence on phosphatidylinositol 3-kinase: common co-signals induced by CD80 and CD86.
CD80 (B7-1) and CD86 (B7-2) ligation of CD28 provide co-stimulatory signals required for optimal lymphokine production in response to TCR zeta-CD3 ligation. CD28 binds to several intracellular proteins including phosphatidylinositol 3-kinase (Pl3-kinase), the tyrosine kinase ITK and the growth factor receptor-bound protein/Son of Sevenless (GRB-2/SOS) complex. Previously, we showed that TCR zeta-CD3 and CD28 co-stimulation required Pl3-kinase binding to the pYMNM motif of the cytoplasmic domain of the co-receptor. In this study, we have investigated whether CD28-associated Pl3-kinase is required for CD80 and CD86 co-stimulation, as well as in co-signaling that involves different primary signals (i.e. TCR zeta-CD3 versus phorbol ester/lonomycin). In the presence of anti-CD3, ligation of CD28 by both CD80 and CD86 was found to induce Pl3-kinase recruitment and IL-2 production. Furthermore, mutations at Y-191 and M-194 within the pYMNM motif blocked the ability of both ligands to induce IL-2. CD80 and CD86 therefore share a common signaling pathway leading to IL-2 production. By contrast, CD28 mediated co-stimulation involving receptor ligation plus phorbol ester/lonomycin induced IL-2 independent of Pl3-kinase binding to CD28. These data indicate that TCR zeta-CD3-dependent CD80 and CD86 co-signaling requires Pl3-kinase binding to the CD28pYMNM motif, while phorbol ester and lonomycin can bypass this requirement in CD28 co-stimulation.
Cefai
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Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Cai
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Hu
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Rudd
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D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D015703:Antigens, CD / Q000494:pharmacology*; D018122:B7-1 Antigen / Q000494:pharmacology*; D051940:B7-2 Antigen; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D016466:CHO Cells; D006224:Cricetinae; D008213:Lymphocyte Activation / Q000187:drug effects; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018106:CD28 Antigens; D008562:Membrane Glycoproteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor)