Institute of Molecular Biology and Pathology, CNR, c/o Sapienza University of Rome, Via degli Apuli 4, 00185, Rome, Italy.
J Cell Sci. 2011 Jan 1;124(Pt 1):113-22. doi: 10.1242/jcs.075457. Epub 2010 Dec 8.
The Aurora-A kinase has well-established roles in spindle assembly and function and is frequently overexpressed in tumours. Its abundance is cell cycle regulated, with a peak in G2 and M phases, followed by regulated proteolysis at the end of mitosis. The microtubule-binding protein TPX2 plays a major role in regulating the activity and localisation of Aurora-A in mitotic cells. Here, we report a novel regulatory role of TPX2 and show that it protects Aurora-A from degradation both in interphase and in mitosis in human cells. Specifically, Aurora-A levels decrease in G2 and prometaphase cells silenced for TPX2, whereas degradation of Aurora-A is impaired in telophase cells overexpressing the Aurora-A-binding region of TPX2. The decrease in Aurora-A in TPX2-silenced prometaphases requires proteasome activity and the Cdh1 activator of the APC/C ubiquitin ligase. Reintroducing either full-length TPX2, or the Aurora-A-binding region of TPX2, but not a truncated TPX2 mutant lacking the Aurora-A-interaction domain, restores Aurora-A levels in TPX2-silenced prometaphases. The control by TPX2 of Aurora-A stability is independent of its ability to activate Aurora-A and to localise it to the spindle. These results highlight a novel regulatory level impinging on Aurora-A and provide further evidence for the central role of TPX2 in regulation of Aurora-A.
极光激酶在纺锤体组装和功能中具有明确的作用，并且在肿瘤中经常过度表达。其丰度受细胞周期调控，在 G2 和 M 期达到高峰，随后在有丝分裂末期被调控性蛋白水解。微管结合蛋白 TPX2 在调节有丝分裂细胞中极光激酶的活性和定位方面起着重要作用。在这里，我们报告了 TPX2 的一个新的调节作用，并表明它在人类细胞的间期和有丝分裂中保护极光激酶免受降解。具体来说，TPX2 沉默的 G2 和前中期细胞中极光激酶的水平降低，而过度表达 TPX2 的极光激酶结合区的晚期细胞中极光激酶的降解受损。TPX2 沉默的前中期细胞中极光激酶的减少需要蛋白酶体活性和 APC/C 泛素连接酶的 Cdh1 激活剂。全长 TPX2 或 TPX2 的极光激酶结合区的重新引入，但缺乏与极光激酶相互作用的结构域的截断 TPX2 突变体，恢复了 TPX2 沉默的前中期细胞中的极光激酶水平。TPX2 对极光激酶稳定性的控制与其激活极光激酶和将其定位到纺锤体的能力无关。这些结果突出了影响极光激酶的新的调节水平，并为 TPX2 在调节极光激酶方面的核心作用提供了进一步的证据。
