Aurora-A磷酸化SLAN之分子機制與細胞功能分析

Aurora-A是一個致癌性serine/threonine蛋白質激酶，負責調控細胞分裂期的行進。文獻顯示高量或抑制Aurora-A表現能引發cytokinesis的失敗並產生多核細胞，且Aurora-A能磷酸化細胞分裂期中軸線多個未知因子，並控制其細胞內的分佈，顯示此磷酸化及可能是Aurora-A控制cytokinesis的關鍵。為了尋找參與在cytokinesis的Aurora-A下游受質，本論文鎖定一細胞分裂期調控因子SLAN。本實驗先前的研究顯示，SLAN為一具潛力的抑癌蛋白，高量表現時會引發細胞分裂期停滯，有些細胞甚至會跳過cytokinesis進入細胞間期而造成多核細胞。由於Aurora-A會磷酸化SLAN，因此我們便提出假說：Aurora-A是否透過磷酸化SLAN來調控cytokinesis。本論文透過分析以下幾項研究議題來測試以上假說，包括分析Aurora-A磷酸化SLAN的分子機制、確認磷酸化位點、分析此磷酸化對於細胞分裂期或cytokinesis的可能調控效應、以及其相應分子作用機制。本論文指出，Aurora-A磷酸化SLAN需要透過鷹架蛋白14-3-3來將前兩者聚集在一起，且磷酸化位點發生於T573，此磷酸化的SLAN能透過調整RhoA來控制cytokinesis的進行。總之，本論文的研究結果顯示，Aurora-A/SLAN/14-3-3為一新型的cytokinesis調控途徑。

關鍵字

Aurora-A ； SLAN ； 14-3-3 ； Cytokinesis

並列摘要

Aurora-A is an oncogenic serine/threonine kinase upregulated in mitosis. Overexpression or silence of Aurora-A induces cytokinesis failure and thereby production of multiple nuclei, implying the engagement of Aurora-A in the control of cytokinesis. Aurora-A is documented phosphorylating cytoplasmic unidentified factors at spindle midzone, and responsible for the spindle midzone- or metaphase plate- targeting of these factors, indicating that Aurora-A likely controls cytokinesis via phosphorylating and in turn midzone localization of its downstream substrates. To search for these factors, we noticed SLAN, a potential tumor suppressor and mitotic regulator guiding mitosis progression and cytokinesis through unknown mechanisms. The previous study in our laboratory shows that SLAN interacts with Aurora-A, and Aurora-A phosphorylates SLAN in an in vitro kinase. Moreover, overexpression of SLAN induces the formation of multiple nuclei, these observations fueling us to speculate a plausible hypothesis where Aurora-A controls cytokinesis through phosphorylation of SLAN. Hence, the thesis focuses itself on testing this hypothesis by proposing several aims, including identifying the molecular mechanisms by which Aurora-A phosphorylates SLAN, mapping the Aurora-A-catalyzed phosphorylation sites on SLAN, determining the potential regulatory effects of SLAN phosphorylation on cytokinesis, and unraveling how Aurora-A/SLAN cascade regulates cytokinesis. The study based on a series of analyses shows that Aurora-A interacts with and phosphorylates SLAN via the help of the scaffold protein 14-3-3, and Aurora-A phosphorylates SLAN at T573, which greatly stimulates M phase arrest and the formation of multiple nuclei. Further mechanistic analyses reveal the involvement of RhoA as one of the key factors downstream to Aurora-A/SLAN axis during cytokinesis. Taken together, the study demonstrates Aurora-A/SLAN/14-3-3 as a novel regulatory axis controlling cytokinesis.