Transamidase site-targeted agents alter the conformation of the transglutaminase cancer stem cell survival protein to reduce GTP binding activity and cancer stem cell survival.
Transamidase site-targeted agents alter the conformation of the transglutaminase cancer stem cell survival protein to reduce GTP binding activity and cancer stem cell survival.
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DOI：
10.1038/onc.2016.452
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发表时间：
2017-05-25
期刊：
影响因子：
8
通讯作者：
Eckert RL
中科院分区：
文献类型：
--
作者：
Kerr C;Szmacinski H;Fisher ML;Nance B;Lakowicz JR;Akbar A;Keillor JW;Lok Wong T;Godoy-Ruiz R;Toth EA;Weber DJ;Eckert RL
2 型转谷氨酰胺酶 (TG2) 是一种重要的癌症干细胞存活蛋白，以开放和闭合构象存在。主要的细胞内形式是闭合构象，充当 GTP 结合 GTP 酶，是癌症干细胞存活所必需的。然而，TG2 以有限的速率转变为开放构象，暴露出参与蛋白质-蛋白质交联的转酰胺酶催化位点。这些活性是相互排斥的，因为闭合构象具有 GTP 结合/GTP 酶活性，而开放构象具有转酰胺酶活性。我们最近表明，TG2 依赖性癌症干细胞侵袭、迁移和肿瘤形成需要 GTP 结合，而不是转酰胺酶活性。然而，令我们惊讶的是转酰胺酶位点特异性抑制剂会降低癌症干细胞的存活率。我们现在证明化合物 NC9、VA4 和 VA5 仅在 TG2 转酰胺酶位点发生反应，可抑制转酰胺酶和 GTP 结合活性。转酰胺酶活性被转酰胺酶位点上的抑制剂直接结合所抑制，并且 GTP 结合被阻断，因为转酰胺酶位点上的抑制剂相互作用将蛋白质锁定在延伸/开放构象中，从而破坏/失活 GTP 结合/GTP 酶位点。这些发现表明，转酰胺酶位点特异性抑制剂可以通过驱动构象变化来破坏 TG2 GTP 结合，从而减少 TG2 依赖性信号传导，从而抑制 GTP 结合/信号传导，并且针对该位点设计的药物可能是有效的抗癌药物。
Type 2 transglutaminase (TG2) is an important cancer stem cell survival protein that exists in open and closed conformations. The major intracellular form is the closed conformation that functions as a GTP-binding GTPase and is required for cancer stem cell survival. However, at a finite rate, TG2 transitions to an open conformation that exposes the transamidase catalytic site involved in protein-protein crosslinking. The activities are mutually exclusive, as the closed conformation has GTP binding/GTPase activity, and the open conformation transamidase activity. We recently showed that GTP binding, but not transamidase activity, is required for TG2-dependent cancer stem cell invasion, migration and tumor formation. However, we were surprised that transamidase site-specific inhibitors reduce cancer stem cell survival. We now show that compounds NC9, VA4 and VA5, which react exclusively at the TG2 transamidase site, inhibit both transamidase and GTP-binding activities. Transamidase activity is inhibited by direct inhibitor binding at the transamidase site, and GTP binding is blocked because inhibitor interaction at the transamidase site locks the protein in the extended/open conformation to disorganize/inactivate the GTP binding/GTPase site. These findings suggest that transamidase site-specific inhibitors can inhibit GTP binding/signaling by driving a conformation change that disorganizes the TG2 GTP binding to reduce TG2-dependent signaling, and that drugs designed to target this site may be potent anti-cancer agents.