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  • Title: Siva-1 negatively regulates NF-kappaB activity: effect on T-cell receptor-mediated activation-induced cell death (AICD).
    Author: Gudi R, Barkinge J, Hawkins S, Chu F, Manicassamy S, Sun Z, Duke-Cohan JS, Prasad KV.
    Journal: Oncogene; 2006 Jun 08; 25(24):3458-62. PubMed ID: 16491128.
    Abstract:
    Ligation of TCRs on stimulated T cells leads to activation-induced cell death (AICD) resulting in the downregulation of immune responses, a process essential for T-cell homeostasis. In this study, using transformed T-cell lines such as Jurkat and Do11.10 as cellular models of TCR-mediated AICD, we have demonstrated that the proapoptotic protein Siva-1 is required for TCR-induced apoptosis. Knockdown of Siva-1 rendered T cells specifically resistant to anti-CD3 but not Fas-induced apoptosis. Further, we observed that in Siva-1 knockout Jurkat cells, TCR-mediated activation of the canonical and non-canonical limbs of the NF-kappaB pathway are significantly enhanced as reflected by elevated nuclear levels of p65 and RelB, respectively. In addition, loss of endogenous Siva-1 also resulted in the enhanced expression of NF-kappaB- responsive anti-apoptotic genes such as Bcl-xL and c-FLIP. Interestingly, the c-FLIP(short) was detected only in TCR-ligated Siva-1 knockdown Jurkat cells. These results demonstrate a significant role for endogenous Siva-1, through its inhibitory effect on NF-kappaB activity, in TCR-mediated AICD with implications in peripheral tolerance, T-cell homeostasis and cancer.
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