Sphingosine-1-phosphate is a missing cofactor for the E3 ubiquitin ligase TRAF2.
Sphingosine-1-phosphate is a missing cofactor for the E3 ubiquitin ligase TRAF2.
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肿瘤坏死因子受体相关因子2(TRAF2)是肿瘤坏死因子κB信号通路中的关键成分。遗传证据表明，TRAF2是受体相互作用蛋白1(RIP1)多泛素化所必需的，受体相互作用蛋白1随后作为IκB激酶(IKK)募集和刺激的平台，导致转录因子NF-κB的激活。TRAF2与鞘氨醇激酶1(SphK1)结合，SphK1是细胞内产生促生存脂质介体鞘氨醇-1-磷酸(S1P)的同工酶之一。在这里，我们证明了SphK1和S1P的产生是赖氨酸63连接的RIP1的多泛素化、IKK和IκBα的磷酸化以及IκBα的降解所必需的，从而导致NF-κB的激活。令人惊讶的是，这些反应是由细胞内的S1P独立于其细胞表面G蛋白偶联受体介导的。S1P与TRAF2的N-末端环区特异性结合，刺激其E3连接酶活性。在泛素结合酶(E2)UbcH13或UbcH5a存在下，S1P，而不是二氢S1P，显著增加了重组TRAF2催化的Lys 63-，但不是Lys 48连接的RIP1的多泛素化。我们的数据显示，TRAF2是S1P的一个新的细胞内靶点，而S1P是TRAF2 E3泛素连接酶活性缺失的辅助因子，这表明了一种调控Lys 63连接的多泛素化的新范式。这些结果还强调了SphK1及其产物S1P在肿瘤坏死因子-α信号转导中的关键作用，以及在炎症、抗凋亡和免疫过程中重要的典型的NF-κB激活途径。
TNF receptor-associated factor 2 (TRAF2) is a key component in NF-κB signaling triggered by TNF–α. Genetic evidence indicates that TRAF2 is necessary for polyubiquitination of receptor interacting protein 1 (RIP1) that then serves as a platform for recruitment and stimulation of IκB kinase (IKK) leading to activation of the transcription factor NF-κB. Although TRAF2 is a RING domain ubiquitin ligase, direct evidence that TRAF2 catalyzes the ubiquitination of RIP1 is lacking. TRAF2 binds to sphingosine kinase 1 (SphK1), one of the isoenzymes that generates the pro-survival lipid mediator sphingosine-1-phosphate (S1P) inside cells. Here we show that SphK1 and production of S1P is necessary for Lys 63-linked polyubiquitination of RIP1, phosphorylation of IKK and IκBα, and IκBα degradation, leading to NF-κB activation. Surprisingly, these responses were mediated by intracellular S1P independently of its cell surface G protein-coupled receptors. S1P specifically binds to TRAF2 at the N-terminal RING domain and stimulates its E3 ligase activity. S1P, but not dihydro-S1P, dramatically increased recombinant TRAF2-catalyzed Lys 63- but not Lys 48-linked polyubiquitination of RIP1 in vitro in the presence of the ubiquitin conjugating enzymes (E2) UbcH13 or UbcH5a. Our data reveal that TRAF2 is a novel intracellular target of S1P, and that S1P is the missing co-factor for TRAF2 E3 ubiquitin ligase activity, suggesting a new paradigm for regulation of Lys 63-linked polyubiquitination. These results also highlight the key role of SphK1 and its product S1P in TNF-α signaling and the canonical NF-κB activation pathway important in inflammatory, anti-apoptotic, and immune processes.
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DOI：
10.1126/science.1176709
发表时间：
2009-09-04
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Hait NC;Allegood J;Maceyka M;Strub GM;Harikumar KB;Singh SK;Luo C;Marmorstein R;Kordula T;Milstien S;Spiegel S
通讯作者：
Spiegel S
影响因子：
16
作者：
Ea, CK;Deng, L;Chen, ZJJ
通讯作者：
Chen, ZJJ
影响因子：
16
作者：
Bertrand, Mathieu J. M.;Milutinovic, Snezana;Barker, Philip A.
通讯作者：
Barker, Philip A.
影响因子：
4.8
作者：
Xia, P;Wang, LJ;Vadas, MA
通讯作者：
Vadas, MA
影响因子：
4.8
作者：
Varfolomeev, Eugene;Goncharov, Tatiana;Vucic, Domagoj
通讯作者：
Vucic, Domagoj