Ubiquitin binding modulates IAP antagonist-stimulated proteasomal degradation of c-IAP1 and c-IAP2
Ubiquitin binding modulates IAP antagonist-stimulated proteasomal degradation of c-IAP1 and c-IAP2
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DOI：
10.1042/bj20081885
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发表时间：
2009-01-01
影响因子：
4.1
通讯作者：
Vucic, Domagoj
中科院分区：
文献类型：
--
作者：
Blankenship, John W.;Varfolomeev, Eugene;Vucic, Domagoj
称为 TAP（凋亡抑制剂）蛋白的抗凋亡调节因子家族与多种细胞伙伴相互作用，并抑制多种刺激诱导的细胞凋亡。c-IAP（细胞 IAP）1 和 2 被募集至 TNFR 1（肿瘤坏死因子受体 1）相关信号复合物，在其中介导受体诱导的 NF-κ B（核因子） kappa B) 激活。此外，通过其 E3 泛素连接酶活性，c-IAP1 和 c-IAP2 促进 NIK（NF-kappa B 诱导激酶）的蛋白酶体降解并调节非经典 NF-kappa B 通路。在本文中，我们描述了 IAP 的一种新型泛素结合域。 IAP 的 UBA（泛素相关）结构域分别位于 c-IAP1 和 c-IAP2 或 XIAP（X 连锁 TAP）的 BIR（杆状病毒 IAP 重复）结构域和 CARD（半胱天冬酶激活和募集结构域）或 RING（非常有趣的新基因）结构域之间。 c-IAP1 UBA 结构域以低微摩尔亲和力结合单泛素以及 Lys(48) 和 Lys(63) 连接的多泛素链（通过表面等离子体共振或等温滴定量热法测定）。 c-IAP1 UBA 结构域-泛素相互作用的 NMR 分析表明，该 UBA 结构域结合泛素 Ile(44) 周围的经典疏水斑块。 UBA 结构域高度同意的 MGF (Met-Gly-Phe) 结合环中关键氨基酸残基的突变完全消除了泛素结合。 UBA 结构域中的这些突变不会明显影响 c-IAP1 的泛素连接酶活性或 c-IAP1 和 c-IAP2 在 TNFR1 信号传导复合物中的参与。用 IAP 拮抗剂处理细胞会导致 c-IAP1 和 c-IAP2 的蛋白酶体降解。 UBA 结构域的缺失或突变会减少这种降解，可能是通过减少 c-IAP 与蛋白酶体的相互作用来实现的。这些结果表明泛素结合可能是自动泛素化的c-IAP1和c-IAP2快速周转的重要机制。
A family of anti-apoptotic regulators known as TAP (inhibitor of apoptosis) proteins interact with multiple cellular partners and inhibit apoptosis induced by a variety Of stimuli.. c-IAP (Cellular IAP) 1 and 2 are recruited to TNFR 1 (tumour necrosis factor receptor 1)-associated signalling complexes, where they mediate receptor-induced NF-kappa B (nuclear factor kappa B) activation. Additionally, through their E3 ubiquitin ligase activities, c-IAP1 and c-IAP2 promote proteasomal degradation of NIK (NF-kappa B-inducing kinase) and regulate the non-canonical NF-kappa B pathway. In the present paper, we describe a novel ubiquitin-binding domain of IAPs. The UBA (ubiquitin-associated) domain of IAPs is located between the BIR (baculovirus IAP repeat) domains and the CARD (caspase activation and recruitment domain) or the RING (really interesting new gene) domain of c-IAP1 and c-IAP2 or XIAP (X-linked TAP) respectively. The c-IAP1 UBA domain binds mono-ubiquitin and Lys(48) and Lys(63)-linked polyubiquitin chains with low-micromolar affinities as determined by surface plasmon resonance or isothermal titration calorimetry. NMR analysis of the c-IAP1 UBA domain-ubiquitin interaction reveals that this UBA domain binds the classical hydrophobic patch surrounding Ile(44) of ubiquitin. Mutations of critical amino acid residues in the highly consented MGF (Met-Gly-Phe) binding loop of the UBA domain completely abrogate ubiquitin binding. These Mutations in the UBA domain do not overtly affect the ubiquitin ligase activity of c-IAP1 or the participation of c-IAP1 and c-IAP2 in the TNFR1 signalling complex. Treatment of cells with IAP antagonists leads to proteasomal degradation of c-IAP1 and c-IAP2. Deletion or mutation of the UBA domain decreases this degradation, probably by diminishing the interaction of the c-IAPs with the proteasome. These results suggest that ubiquitin binding may be an important mechanism for rapid turnover Of auto-ubiquitinated c-IAP1 and c-IAP2.