Yang Shuo, Liu Xuan, Yin Yanqing, Fukuda Michiko N, Zhou Jiawei
Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai, China.
FASEB J. 2008 Jun;22(6):1960-72. doi: 10.1096/fj.07-081463. Epub 2008 Jan 24.
Tastin was previously characterized as an accessory protein for cell adhesion that participates in early embryo implantation. Here, we report that tastin is also required for spindle assembly during mitosis. Tastin protein levels peaked in the G(2)/M phase and abruptly declined after cell division. Microscopy showed that tastin is primarily localized on the microtubules, centrosomes, and the mitotic spindle during the cell cycle. Tastin interacted with the dynein intermediate chain, p150(Glued), and gamma-tubulin in addition to Tctex-1 (the light chain of dynein). Overexpression of tastin led to monopolar spindle formation, whereas loss of tastin expression caused profound mitotic block and preferentially induced multipolar spindles. These multipolar spindles were generated through a loss of cohesion in mitotic centrosomes; specifically, tastin depletion caused the fragmentation of pericentrosomal material and the splitting of the centrioles at the spindle poles. Tastin depletion induced centrosome abnormalities exclusively during mitosis and required both microtubule integrity and Eg5 activity. However, tastin depletion did not disrupt the organization of spindle poles, as revealed by localization of nuclear mitotic apparatus protein (NuMA) and the p150(Glued) component of dynactin. These data indicate that the major function of tastin during mitosis is to maintain the structural and dynamic features of centrosomes, thereby contributing to spindle bipolarity.
Tastin先前被表征为参与早期胚胎着床的细胞粘附辅助蛋白。在此，我们报告Tastin在有丝分裂期间的纺锤体组装中也是必需的。Tastin蛋白水平在G(2)/M期达到峰值，并在细胞分裂后急剧下降。显微镜检查显示，Tastin在细胞周期中主要定位于微管、中心体和有丝分裂纺锤体上。除了Tctex-1（动力蛋白轻链）外，Tastin还与动力蛋白中间链、p150(Glued)和γ-微管蛋白相互作用。Tastin的过表达导致单极纺锤体形成，而Tastin表达缺失则导致严重的有丝分裂阻滞并优先诱导多极纺锤体。这些多极纺锤体是通过有丝分裂中心体凝聚力丧失产生的；具体而言，Tastin缺失导致中心体周围物质碎片化和纺锤体极处中心粒分裂。Tastin缺失仅在有丝分裂期间诱导中心体异常，并且需要微管完整性和Eg5活性。然而，如核有丝分裂装置蛋白（NuMA）和动力蛋白激活蛋白的p150(Glued)成分的定位所示，Tastin缺失并未破坏纺锤体极的组织。这些数据表明，Tastin在有丝分裂期间的主要功能是维持中心体的结构和动态特征，从而有助于纺锤体双极性。
