TRAF2 inhibits TRAIL- and CD95L-induced apoptosis and necroptosis.
TRAF2 inhibits TRAIL- and CD95L-induced apoptosis and necroptosis.
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DOI：
10.1038/cddis.2014.404
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发表时间：
2014-10-09
影响因子：
9
通讯作者：
Giner T
中科院分区：
文献类型：
--
作者：
Karl I;Jossberger-Werner M;Schmidt N;Horn S;Goebeler M;Leverkus M;Wajant H;Giner T
衔接蛋白TNF受体相关因子2（TRAF 2）与死亡受体肿瘤坏死因子受体1（TNFR 1）信号转导的相关性已得到充分证实。然而，TRAF 2通过CD 95和TNF相关的凋亡诱导配体（TRAIL）DR进行信号传导的作用仅知之甚少。在这里，我们观察到TRAF 2的敲低（KD）使角质形成细胞对TRAIL和CD 95 L诱导的凋亡敏感。有趣的是，虽然在对照细胞中，细胞死亡被泛半胱天冬酶抑制剂苄氧基羰基-Val-Ala-Asp（OMe）-氟甲基酮（zVAD-fetamine）完全阻断，但TRAF 2耗尽的角质形成细胞仅部分地从TRAIL和CD 95 L诱导的细胞死亡中被拯救。与该想法一致，zVAD-fastin对TRAIL和CD 95 L处理的TRAF 2耗尽的角质形成细胞的仅有的部分保护作用是由于诱导坏死性凋亡，zVAD-fastin和受体相互作用蛋白1（RIP 1）抑制剂坏死抑素-1的组合治疗完全拯救了这些细胞。为了更好地理解TRAF 2水平对RIP 1和RIP 3依赖性坏死性凋亡和RIP 3非依赖性凋亡的影响，我们在缺乏内源性RIP 3的HeLa细胞和稳定转染RIP 3的HeLa细胞中进行了实验。HeLa细胞，其中坏死性凋亡没有作用，显着敏感的TRAIL诱导的半胱天冬酶依赖性凋亡TRAF 2 KD。然而，在表达RIP 3的HeLa转染子中，TRAF 2的KD也对TRAIL诱导的坏死性凋亡强烈敏感。值得注意的是，用可溶性TWEAK（其耗尽含TRAF 2的蛋白质复合物的胞质池）引发角质形成细胞导致对TRAIL诱导的坏死性凋亡的强烈敏化，但对TRAIL诱导的细胞凋亡仅具有非常有限的作用。坏死性凋亡的TRAIL反应不依赖于内源性产生的TNF和TNFR信号传导，因为通过TNFR 2-Fc或抗TNF α阻断TNF对坏死性凋亡诱导没有影响。总之，我们确定TRAF 2不仅作为DR诱导的细胞凋亡的负调节剂，而且特别是作为TRAIL和CD 95 L诱导的坏死性凋亡的拮抗剂。
The relevance of the adaptor protein TNF receptor-associated factor 2 (TRAF2) for signal transduction of the death receptor tumour necrosis factor receptor1 (TNFR1) is well-established. The role of TRAF2 for signalling by CD95 and the TNF-related apoptosis inducing ligand (TRAIL) DRs, however, is only poorly understood. Here, we observed that knockdown (KD) of TRAF2 sensitised keratinocytes for TRAIL- and CD95L-induced apoptosis. Interestingly, while cell death was fully blocked by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) in control cells, TRAF2-depleted keratinocytes were only partly rescued from TRAIL- and CD95L-induced cell death. In line with the idea the only partially protective effect of zVAD-fmk on TRAIL- and CD95L-treated TRAF2-depleted keratinocytes is due to the induction of necroptosis, combined treatment with zVAD-fmk and the receptor interacting protein 1 (RIP1) inhibitor necrostatin-1 that fully rescued these cells. To better understand the impact of TRAF2 levels on RIP1- and RIP3-dependent necroptosis and RIP3-independent apoptosis, we performed experiments in HeLa cells that lack endogenous RIP3 and HeLa cells stably transfected with RIP3. HeLa cells, in which necroptosis has no role, were markedly sensitised to TRAIL-induced caspase-dependent apoptosis by TRAF2 KD. In RIP3-expressing HeLa transfectants, however, KD of TRAF2 also strongly sensitised for TRAIL-induced necroptosis. Noteworthy, priming of keratinocytes with soluble TWEAK, which depletes the cytosolic pool of TRAF2-containing protein complexes, resulted in strong sensitisation for TRAIL-induced necroptosis but had only a very limited effect on TRAIL-induced apoptosis. The necroptotic TRAIL response was not dependent on endogenously produced TNF and TNFR signalling, since blocking TNF by TNFR2-Fc or anti-TNFα had no effect on necroptosis induction. Taken together, we identified TRAF2 not only as a negative regulator of DR-induced apoptosis but in particular also as an antagonist of TRAIL- and CD95L-induced necroptosis.