CAMSAP3 orients the apical-to-basal polarity of microtubule arrays in epithelial cells
CAMSAP3 orients the apical-to-basal polarity of microtubule arrays in epithelial cells
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DOI：
10.1073/pnas.1520638113
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发表时间：
2016-01-12
影响因子：
11.1
通讯作者：
Takeichi, Masatoshi
中科院分区：
文献类型：
--
作者：
Toya, Mika;Kobayashi, Saeko;Takeichi, Masatoshi
极化上皮细胞表现出沿细胞顶端基底轴定向的特征性微管阵列。这些微管的负端面向顶部，正端面向基侧。然而，这种上皮特异性微管组装的机制仍未解决。在这里，使用小鼠肠细胞和人 Caco-2 细胞，我们发现微管负端结合蛋白 CAMSAP3（钙调蛋白调节血影蛋白相关蛋白 3）在定向上皮细胞中微管的顶端到基底极性方面发挥着关键作用。在这些细胞中，CAMSAP3 在顶皮质积聚，并将纵向微管拴在这些部位。 Camsap3 突变或缺失导致这些微管的方向随机；与此同时，细胞核和高尔基体的定型定位也受到干扰。相反，质膜的完整性几乎没有受到影响，尽管其结构稳定性有所下降。进一步的分析表明，CAMSAP3 的 CC1 结构域对其顶端定位至关重要，并且 CAMSAP3 的强制错误定位会扰乱上皮结构。这些发现表明，顶端定位的 CAMSAP3 决定了成熟哺乳动物上皮细胞中微管的正确方向，进而决定了细胞器的正确方向。
Polarized epithelial cells exhibit a characteristic array of microtubules that are oriented along the apicobasal axis of the cells. The minus-ends of these microtubules face apically, and the plus-ends face toward the basal side. The mechanisms underlying this epithelial-specific microtubule assembly remain unresolved, however. Here, using mouse intestinal cells and human Caco-2 cells, we show that the microtubule minus-end binding protein CAMSAP3 (calmodulin-regulated-spectrin-associated protein 3) plays a pivotal role in orienting the apical-to-basal polarity of microtubules in epithelial cells. In these cells, CAMSAP3 accumulated at the apical cortices, and tethered the longitudinal microtubules to these sites. Camsap3 mutation or depletion resulted in a random orientation of these microtubules; concomitantly, the stereotypic positioning of the nucleus and Golgi apparatus was perturbed. In contrast, the integrity of the plasma membrane was hardly affected, although its structural stability was decreased. Further analysis revealed that the CC1 domain of CAMSAP3 is crucial for its apical localization, and that forced mislocalization of CAMSAP3 disturbs the epithelial architecture. These findings demonstrate that apically localized CAMSAP3 determines the proper orientation of microtubules, and in turn that of organelles, in mature mammalian epithelial cells.