Structure, Dynamics, and Functionality of Tankyrase Inhibitor-Induced Degradasomes
Structure, Dynamics, and Functionality of Tankyrase Inhibitor-Induced Degradasomes
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DOI：
10.1158/1541-7786.mcr-15-0125
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发表时间：
2015-11-01
影响因子：
5.2
通讯作者：
Stenmark, Harald
中科院分区：
文献类型：
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作者：
Thorvaldsen, Tor Espen;Pedersen, Nina Marie;Stenmark, Harald
端锚聚合酶（TNKS）酶，由于其聚（ADP-核糖）聚合酶活性，已成为实验性癌症治疗的潜在靶标。然而，TNKS抑制的功能后果仍然没有完全解决，因为TNKS的结合混杂。小分子TNKS抑制剂（TNKSi）的标志之一是稳定轴蛋白，轴蛋白在WNT/β-连环蛋白信号通路中起关键作用。本研究集中于TNKSi诱导由信号限制WNT/β-连环蛋白破坏复合物的组分组成的细胞质斑点（降解酶体）的已知能力。使用用GFP-TNKS 1稳定转染的结肠直肠癌细胞系SW 480，证明TNKS特异性抑制剂（G 007-LK）诱导含有磷酸化β-连环蛋白、泛素和β-TrCP的高度动态和移动的降解体。同样，发现G 007-LK在表达降解酶体组分APC的野生型或截短形式的其他结肠直肠癌细胞系中诱导类似的降解酶体。超分辨率和电子显微镜显示，诱导degradasomes在SW 480细胞是无膜结构，包括高电子密度的丝状组装和各种破坏复杂的组件的离散子域。光漂白实验后的荧光恢复进一步证明，β-连环蛋白-mCherry在G 007-LK诱导的降解体中迅速翻转，而GFP-TNKS 1保持稳定。总之，TNKS抑制通过促进功能性活性破坏复合物动态组装成含TNKS的支架，即使在APC截短的存在下，也能减弱WNT/β-连环蛋白信号传导。这项研究表明，β-连环蛋白在WNT破坏复合物的高度动态组装中迅速翻转在结直肠癌细胞中，WNT信号转导在端锚聚合酶抑制后与降解酶体（降解酶体）的结合并提供降解酶体形成与降低的WNT信号转导之间的直接机制联系。Mol Cancer Res; 13（11）; 1487-501. (C)2015年AACR。
Tankyrase (TNKS) enzymes, due to their poly(ADP-ribose) polymerase activity, have emerged as potential targets in experimental cancer therapy. However, the functional consequences of TNKS inhibition remain incompletely resolved because of the binding promiscuity of TNKS. One of the hallmarks of small-molecule TNKS inhibitors (TNKSi) is the stabilization of AXIN, which plays a pivotal role in the WNT/beta-catenin signaling pathway. The present study focused on the known ability of TNKSi to induce cytoplasmic puncta (degradasomes) consisting of components of the signal limiting WNT/beta-catenin destruction complex. Using the colorectal cancer cell line SW480 stably transfected with GFP-TNKS1, it was demonstrated that a TNKS-specific inhibitor (G007-LK) induces highly dynamic and mobile degradasomes that contain phosphorylated beta-catenin, ubiquitin, and beta-TrCP. Likewise, G007-LK was found to induce similar degradasomes in other colorectal cancer cell lines expressing wild-type or truncated versions of the degradasome component APC. Super-resolution and electron microscopy revealed that the induced degradasomes in SW480 cells are membrane-free structures that consist of a filamentous assembly of high electron densities and discrete subdomains of various destruction complex components. Fluorescence recovery after photobleaching experiments further demonstrated that beta-catenin-mCherry was rapidly turned over in the G007-LK-induced degradasomes, whereas GFP-TNKS1 remained stable. In conclusion, TNKS inhibition attenuatesWNT/beta-catenin signaling by promoting dynamic assemblies of functional active destruction complexes into a TNKS-containing scaffold even in the presence of an APC truncation.Implications: This study demonstrates that beta-catenin is rapidly turned over in highly dynamic assemblies of WNT destruction complexes (degradasomes) upon tankyrase inhibition and provides a direct mechanistic link between degradasome formation and reduced WNT signaling in colorectal cancer cells. Mol Cancer Res; 13(11); 1487-501. (C) 2015 AACR.