X-linked Inhibitor of Apoptosis Protein and Its E3 Ligase Activity Promote Transforming Growth Factor-β-mediated Nuclear Factor-κB Activation during Breast Cancer Progression
X-linked Inhibitor of Apoptosis Protein and Its E3 Ligase Activity Promote Transforming Growth Factor-β-mediated Nuclear Factor-κB Activation during Breast Cancer Progression
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DOI：
10.1074/jbc.m109.018374
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发表时间：
2009-08-07
影响因子：
4.8
通讯作者：
Schiemann, William P.
中科院分区：
文献类型：
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作者：
Neil, Jason R.;Tian, Maozhen;Schiemann, William P.
使乳腺肿瘤发生将转化生长因子- β (tgf - β)从肿瘤抑制因子转化为肿瘤启动因子的确切事件序列仍不完全清楚。我们在这里表明，x -连锁凋亡蛋白抑制剂（xIAP）对于tgf - β刺激转移性4T1乳腺癌细胞中核因子κ B （nf - κ B）的能力至关重要。事实上，tgf - β抑制正常乳腺上皮细胞中NF-kappa B的活性，而那些经过改造过表达xIAP的乳腺上皮细胞在tgf - β刺激下表现出NF-kappa B的活化。此外，上调的xIAP表达还增强了Smad2/3和NF-kappa b的基础转录活性和tgf - β刺激的转录活性。机制上，xIAP (i)与tgf - β i型受体物理相互作用，（ii）介导tgf - β活化激酶1 （TAK1）的泛素化。（iii）促进tak1结合蛋白1 （TAB1）和I kappa B激酶β之间形成复合物，使tgf - β激活p65/Re1A，并诱导转移前基因（即环氧化酶-2和纤溶酶原激活物抑制剂-1）和生存前基因（即生存素）的表达。我们进一步观察到，抑制xIAP的E3泛素连接酶功能或表达突变的泛素蛋白（即K63R-ubiquitin）能够阻断xIAP-和tgf - β介导的NF-kappa b的激活。功能上，xIAP缺乏显著降低了NMuMG细胞中tgf - β与Smad2/3的偶联，并抑制了它们响应tgf - β的间充质标志物的表达。更重要的是，缺乏xIAP也会破坏TAB1的形成。I kappa B激酶β复合物在4T1乳腺癌细胞中，从而降低NF-kappa B的激活、促生存/转移基因的表达、通过合成基底膜的入侵以及在软琼脂中的生长。总的来说，我们的研究结果确定了xIAP在乳腺癌细胞中介导tgf - β致癌信号传导中的新作用。
The precise sequence of events that enable mammary tumorigenesis to convert transforming growth factor-beta (TGF-beta) from a tumor suppressor to a tumor promoter remains incompletely understood. We show here that X-linked inhibitor of apoptosis protein (xIAP) is essential for the ability of TGF-beta to stimulate nuclear factor-kappa B (NF-kappa B) in metastatic 4T1 breast cancer cells. Indeed whereas TGF-beta suppressed NF-kappa B activity in normal mammary epithelial cells, those engineered to overexpress xIAP demonstrated activation of NF-kappa B when stimulated with TGF-beta. Additionally up-regulated xIAP expression also potentiated the basal and TGF-beta-stimulated transcriptional activities of Smad2/3 and NF-kappa B. Mechanistically xIAP (i) interacted physically with the TGF-beta type I receptor, (ii) mediated the ubiquitination of TGF-beta-activated kinase 1 (TAK1), and (iii) facilitated the formation of complexes between TAK1-binding protein 1 (TAB1) and I kappa B kinase beta that enabled TGF-beta to activate p65/Re1A and to induce the expression of prometastatic (i.e. cyclooxygenase-2 and plasminogen activator inhibitor-1) and prosurvival (i.e. survivin) genes. We further observed that inhibiting the E3 ubiquitin ligase function of xIAP or expressing a mutant ubiquitin protein (i.e. K63R-ubiquitin) was capable of blocking xIAP- and TGF-beta-mediated activation of NF-kappa B. Functionally xIAP deficiency dramatically reduced the coupling of TGF-beta to Smad2/3 in NMuMG cells as well as inhibited their expression of mesenchymal markers in response to TGF-beta. More importantly, xIAP deficiency also abrogated the formation of TAB1.I kappa B kinase beta complexes in 4T1 breast cancer cells, thereby diminishing their activation of NF-kappa B, their expression of prosurvival/metastatic genes, their invasion through synthetic basement membranes, and their growth in soft agar. Collectively our findings have defined a novel role for xIAP in mediating oncogenic signaling by TGF-beta in breast cancer cells.