MODIFICATION OF THE E-CADHERIN-CATENIN COMPLEX IN MITOTIC MADIN-DARBYCANINE KIDNEY EPITHELIAL-CELLS

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 integri n 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 th e catenins (alpha-catenin, beta-catenin, plakoglobin, p120(ctn)) in th e 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 associa ted 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 m itosis-specific changes in phosphorylation. We report a decrease in th e tyrosine phosphorylation of beta-catenin, plakoglobin, and p120(ctn) during mitosis. Moreover, we observed a mitosis-specific Ser/Thr-phos phorylation of p120(ctn), as detected by the MPM-2 antibody. Hence, th e cadherin/catenin complex is a target for different posttranslational modifications during mitosis, which may also have a profound impact o n cadherin-mediated cell-cell adhesion.