Bauer A, Lickert H, Kemler R, Stappert J
Department of Molecular Embryology, Max-Planck Institute of Immunobiology, Stübeweg 51, D-79108 Freiburg, Germany.
J Biol Chem. 1998 Oct 23;273(43):28314-21. doi: 10.1074/jbc.273.43.28314.
One of the hallmarks of polarized epithelial cells undergoing mitosis is their rounded morphology. This phenotype correlates with a reduced cell-substratum adhesion, apparently caused by a modulation of integrin function. However, it is still unclear whether the cadherin-mediated cell-cell adhesion is affected as well. To address this question, the cadherin complex was analyzed in different cell cycle stages of Madin-Darby canine kidney cells. By immunofluorescence, mitotic Madin-Darby canine kidney cells showed an increased staining of E-cadherin and the catenins (alpha-catenin, beta-catenin, plakoglobin, p120(ctn)) in the cytosol, suggesting a reorganization of the cadherin-catenin complex during mitosis. Biochemical analysis revealed that the overall amount of these components, as well as the proportion of the complex associated with the actin cytoskeleton, remained unchanged in mitotic cells. However, we found evidence for an internalization of E-cadherin during mitosis. In addition, the cadherin-catenin complex was analyzed for mitosis-specific changes in phosphorylation. We report a decrease in the tyrosine phosphorylation of beta-catenin, plakoglobin, and p120(ctn) during mitosis. Moreover, we observed a mitosis-specific Ser/Thr-phosphorylation of p120(ctn), as detected by the MPM-2 antibody. Hence, the cadherin/catenin complex is a target for different posttranslational modifications during mitosis, which may also have a profound impact on cadherin-mediated cell-cell adhesion.
正在进行有丝分裂的极化上皮细胞的一个特征是其圆形形态。这种表型与细胞-基质黏附力降低相关，这显然是由整合素功能的调节引起的。然而，尚不清楚钙黏蛋白介导的细胞-细胞黏附是否也受到影响。为了解决这个问题，我们在犬肾细胞（Madin-Darby canine kidney cells，简称MDCK细胞）的不同细胞周期阶段分析了钙黏蛋白复合体。通过免疫荧光检测，有丝分裂期的MDCK细胞在细胞质中E-钙黏蛋白和连环蛋白（α-连环蛋白、β-连环蛋白、桥粒斑蛋白、p120连环蛋白）的染色增加，这表明在有丝分裂期间钙黏蛋白-连环蛋白复合体发生了重组。生化分析表明，这些组分的总量以及与肌动蛋白细胞骨架相关的复合体比例在有丝分裂细胞中保持不变。然而，我们发现有证据表明E-钙黏蛋白在有丝分裂期间发生了内化。此外，我们分析了钙黏蛋白-连环蛋白复合体在有丝分裂过程中磷酸化的特异性变化。我们报告在有丝分裂期间β-连环蛋白、桥粒斑蛋白和p120连环蛋白的酪氨酸磷酸化减少。此外，我们观察到p120连环蛋白存在有丝分裂特异性的丝氨酸/苏氨酸磷酸化，这是通过MPM-2抗体检测到的。因此，钙黏蛋白/连环蛋白复合体是有丝分裂期间不同翻译后修饰的靶点，这也可能对钙黏蛋白介导的细胞-细胞黏附产生深远影响。
