Dynamics of E-cadherin and gamma-catenin complexes during dedifferentiation of polarized MDCK cells

Background. E-cadherin mediated cell-cell adhesion and hepatocyte growth fa ctor (HGF) are important for renal epithelial morphogenesis. We previously showed that HGF dedifferentiates previously well polarized Madin-Darby cani ne kidney (MDCK) cell monolayers grown on filters. The regulation of E-cadh erin during epithelial dedifferentiation is not known. We hypothesized that E-cadherin mediated cell-cell adhesion is modulated during HGF induced ded ifferentiation of MDCK cell monolayers. Methods. We analyzed E-cadherin/gamma-catenin interaction and distribution during epithelial dedifferentiation in vitro using a model of polarized MDC K cell monolayers treated with HGF. Results. Surface immunoprecipitation experiments showed that HGF increased the amount of cell surface E-cadherin associated with gamma-catenin. Bioche mical and morphological examination of the TX-100 solubility of junctional E-cadherin and gamma-catenin in control and HGF treated cells showed an inc rease in solubility of only E-cadherin during loss of cell polarity. Metabo lic labeling of control and HGF treated cells showed that HGF stimulated th e synthetic rate of E-cadherin and gamma-catenin molecules. Inulin flux acr oss MDCK cell monolayers increases with HGF treatment. Conclusion. These data provide evidence for both the dissociation of E-cadh erin molecules from the actin cytoskeleton and an increase in the total num ber of E-cadherin/gamma-catenin complexes on the cell surface during HGF-in duced dedifferentiation of polarized renal epithelium. These data support t he hypothesis that E-cadherin function is inhibited by a mechanism of detac hment from the actin based cytoskeleton during HGF induced dedifferentiatio n of polarized renal epithelia.