State Key Laboratory of Biocontrol, Key Laboratory of Gene Engineering of Ministry of Education, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China.
J Immunol. 2013 Apr 15;190(8):4027-36. doi: 10.4049/jimmunol.1202742. Epub 2013 Mar 20.
TNFR-associated factor (TRAF)6 is an essential ubiquitin E3 ligase in immune responses, but its function in adaptive immunity is not well understood. In this study, we show that TRAF6 is recruited to the peripheral ring of the T cell immunological synapse in Jurkat T cells or human primary CD4(+) T cells conjugated with staphylococcal enterotoxin E-pulsed B cells. This recruitment depends on TRAF6 interacting with linker for activation of T cells (LAT) via its TRAF domain. Although LAT was indispensable for TCR/CD28-induced TRAF6 ubiquitination and its ligase activity, RNA interference-induced TRAF6 knockdown in T cells decreased TCR/CD28-induced LAT ubiquitination, tyrosine phosphorylation, and association with tyrosine kinase ZAP70. Overexpression of TRAF6 or its catalytically inactive form C70A promoted and decreased, respectively, LAT tyrosine phosphorylation upon stimulation. Moreover, LAT was ubiquitinated at Lys(88) by TRAF6 via K63-linked chain. In addition, TRAF6 was required for and synergized with LAT to promote the TCR/CD28-induced activation of NFAT. These results reveal a novel function and mechanism of TRAF6 action in the TCR-LAT signaling pathway distinct from its role in TCR-induced NF-κB activation, indicating that LAT also plays an adapter role in TCR/CD28-induced activation of TRAF6.
肿瘤坏死因子受体相关因子（TRAF）6 是免疫反应中一种必需的泛素 E3 连接酶，但它在适应性免疫中的功能尚不清楚。在这项研究中，我们表明 TRAF6 被招募到 Jurkat T 细胞或与人原发性 CD4(+) T 细胞与被葡萄球菌肠毒素 E 脉冲化的 B 细胞连接的 T 细胞免疫突触的外周环。这种募集依赖于 TRAF6 通过其 TRAF 结构域与 T 细胞激活连接物（LAT）相互作用。尽管 LAT 对于 TCR/CD28 诱导的 TRAF6 泛素化及其连接酶活性是必不可少的，但 T 细胞中的 RNA 干扰诱导的 TRAF6 敲低降低了 TCR/CD28 诱导的 LAT 泛素化、酪氨酸磷酸化以及与酪氨酸激酶 ZAP70 的关联。TRAF6 的过表达或其催化失活形式 C70A 分别促进和降低刺激时的 LAT 酪氨酸磷酸化。此外，TRAF6 通过 K63 连接链在 Lys(88)上将 LAT 泛素化。此外，TRAF6 需要并与 LAT 协同促进 TCR/CD28 诱导的 NFAT 激活。这些结果揭示了 TRAF6 在 TCR-LAT 信号通路中的作用的一个新功能和机制，与它在 TCR 诱导的 NF-κB 激活中的作用不同，表明 LAT 也在 TCR/CD28 诱导的 TRAF6 激活中发挥衔接器作用。
