Dataset for: DR5-Cbl-b/c-Cbl-TRAF2 complex inhibits TRAIL-induced apoptosis by promoting TRAF2-mediated polyubiquitination of caspase-8 in gastric cancer cells

Ubiquitination of caspase-8 regulates TRAIL sensitivity in cancer cell, and the preligand assembly complex plays a role in caspase-8 polyubiquitination. However, whether such a complex exists in gastric cancer cells and its role in TRAIL-triggered apoptosis is unclear. In the present study, DR5, Cbl-b/c-Cbl, and TRAF2 formed a complex in TRAIL-resistant gastric cancer cells, and Cbl-b and c-Cbl were the critical adaptors linking DR5 and TRAF2. Treatment with TRAIL induced caspase-8 translocation into the DR5-Cbl-b/c-Cbl-TRAF2 complex to interact with TRAF2, which then mediated the K48-linked polyubiquitination of caspase-8. The proteasome inhibitor bortezomib markedly enriched the p43/41 products of caspase-8 activated by TRAIL, indicating proteasomal degradation of caspase-8. Moreover, TRAF2 knockdown prevented the polyubiquitination of caspase-8, and thus increased TRAIL sensitivity. In addition, the inhibition of Cbl-b or c-Cbl expression and overexpression of miR-141 targeting Cbl-b and c-Cbl partially reversed TRAIL resistance by inhibiting the interaction of TRAF2 and caspase-8 and the subsequent polyubiquitination of caspase-8. These results indicate that the DR5-Cbl-b/c-Cbl-TRAF2 complex inhibited TRAIL-induced apoptosis by promoting TRAF2-mediated polyubiquitination of caspase-8 in gastric cancer cells.

半胱天冬酶-8（caspase-8）的泛素化调控肿瘤细胞对肿瘤坏死因子相关凋亡诱导配体（TRAIL）的敏感性，而配体前组装复合物（preligand assembly complex）参与半胱天冬酶-8的多泛素化过程。然而，此类复合物是否存在于胃癌细胞中，以及其在TRAIL诱导的细胞凋亡中发挥的功能尚不清楚。本研究中，研究人员在耐TRAIL的胃癌细胞中发现，死亡受体5（DR5）、Cbl-b/c-Cbl以及肿瘤坏死因子受体相关因子2（TRAF2）可形成复合物，且Cbl-b与c-Cbl是连接DR5与TRAF2的关键适配蛋白。经TRAIL处理后，半胱天冬酶-8易位至DR5-Cbl-b/c-Cbl-TRAF2复合物中并与TRAF2结合，后者随后介导半胱天冬酶-8的K48位连接型多泛素化。蛋白酶体抑制剂硼替佐米（bortezomib）可显著富集TRAIL激活产生的半胱天冬酶-8 p43/41裂解产物，提示半胱天冬酶-8经蛋白酶体途径降解。此外，敲低TRAF2可阻断半胱天冬酶-8的多泛素化，进而提升细胞对TRAIL的敏感性。另外，抑制Cbl-b或c-Cbl的表达，以及过表达靶向Cbl-b和c-Cbl的微小RNA-141（miR-141），可通过阻断TRAF2与半胱天冬酶-8的相互作用及其后续的半胱天冬酶-8多泛素化过程，部分逆转细胞对TRAIL的耐药性。上述结果表明，在胃癌细胞中，DR5-Cbl-b/c-Cbl-TRAF2复合物可通过促进TRAF2介导的半胱天冬酶-8多泛素化，抑制TRAIL诱导的细胞凋亡。