American Society for Microbiology, Molecular and Cellular Biology, 21(25), p. 9543-9553, 2005
DOI: 10.1128/mcb.25.21.9543-9553.2005
American Society of Hematology, Blood, 11(104), p. 2657-2657, 2004
DOI: 10.1182/blood.v104.11.2657.2657
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Abstract CTLA-4 and PD-1 are receptors that negatively regulate T cell activation. Ligation of both CTLA-4 and PD-1 blocked CD3/CD28 mediated upregulation of glucose metabolism and Akt activity, but each accomplished this regulation using separate mechanisms. CTLA-4 mediated inhibition of Akt phosphorylation is sensitive to okadaic acid, providing direct evidence that PP2A plays a prominent role in mediating CTLA-4 suppression of T cell activation. In contrast, PD-1 signaling inhibits Akt phosphorylation by preventing CD28 mediated activation of phosphatidylinositol 3-kinase (PI3K). The ability of PD-1 to suppress PI3K/Atk activation was dependent upon the ITSM located in its cytoplasmic tail. Lastly, PD-1 ligation is more effective in suppressing CD3/28 induced changes in the T cell transcriptional profile, suggesting that differential regulation of PI3K activation by PD-1 and CTLA-4 ligation results in distinct cellular phenotypes. Together, these data suggest that CTLA-4 and PD-1 inhibit T cell activation through distinct and potentially synergistic mechanisms.