Moss David K, Bellett Gemma, Carter Jane M, Liovic Mirjana, Keynton Jennifer, Prescott Alan R, Lane E Birgitte, Mogensen Mette M
School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.
J Cell Sci. 2007 Sep 1;120(Pt 17):3064-74. doi: 10.1242/jcs.010322. Epub 2007 Aug 14.
Cell-to-cell contact and polarisation of epithelial cells involve a major reorganisation of the microtubules and centrosomal components. The radial microtubule organisation is lost and an apico-basal array develops that is no longer anchored at the centrosome. This involves not only the relocation of microtubules but also of centrosomal anchoring proteins to apical non-centrosomal sites. The relocation of microtubule minus-end-anchoring proteins such as ninein to the apical sites is likely to be essential for the assembly and stabilisation of the apico-basal arrays in polarised epithelial cells. In this study, we establish that ninein is highly dynamic and that, in epithelial cells, it is present not only at the centrosome but also in the cytoplasm as distinct speckles. Live-cell imaging reveals that GFP-ninein speckles are released from the centrosome and move in a microtubule-dependent manner within the cytoplasm and thus establishes that epithelial cells possess the mechanical means for relocation of ninein to non-centrosomal anchoring sites. We also provide evidence for the deployment of ninein speckles to apical anchoring sites during epithelial differentiation in both an in situ tissue and an in vitro culture system. In addition, the findings suggest that the non-centrosomal microtubule anchoring sites associate with adherens junctions in polarised epithelial cells.
细胞间接触和上皮细胞极化涉及微管和中心体成分的重大重组。径向微管组织消失，取而代之的是不再锚定在中心体的顶-基微管阵列。这不仅涉及微管的重新定位，还涉及中心体锚定蛋白向顶端非中心体部位的重新定位。微管负端锚定蛋白（如九蛋白）向顶端部位的重新定位可能对极化上皮细胞中顶-基微管阵列的组装和稳定至关重要。在本研究中，我们证实九蛋白具有高度动态性，并且在上皮细胞中，它不仅存在于中心体，还以离散斑点的形式存在于细胞质中。活细胞成像显示，绿色荧光蛋白标记的九蛋白斑点从中心体释放，并在细胞质中以微管依赖的方式移动，从而证实上皮细胞具备将九蛋白重新定位到非中心体锚定部位的机制。我们还提供了证据，表明在原位组织和体外培养系统中，九蛋白斑点在上皮分化过程中被部署到顶端锚定部位。此外，研究结果表明，非中心体微管锚定部位与极化上皮细胞中的黏着连接相关。
