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

E-cadherin mediated cell-cell adhesion and hepatocyte growth factor (HGF) are important for renal epithelial morphogenesis. We previously showed that HGF dedifferentiates previously well polarized Madin-Darby canine kidney (MDCK) cell monolayers grown on filters. The regulation of E-cadherin during epithelial dedifferentiation is not known. We hypothesized that E-cadherin mediated cell-cell adhesion is modulated during HGF induced dedifferentiation of MDCK cell monolayers.

We analyzed E-cadherin/gamma-catenin interaction and distribution during epithelial dedifferentiation in vitro using a model of polarized MDCK cell monolayers treated with HGF.

Surface immunoprecipitation experiments showed that HGF increased the amount of cell surface E-cadherin associated with gamma-catenin. Biochemical and morphological examination of the TX-100 solubility of junctional E-cadherin and gamma-catenin in control and HGF treated cells showed an increase in solubility of only E-cadherin during loss of cell polarity. Metabolic labeling of control and HGF treated cells showed that HGF stimulated the synthetic rate of E-cadherin and gamma-catenin molecules. Inulin flux across MDCK cell monolayers increases with HGF treatment.

These data provide evidence for both the dissociation of E-cadherin molecules from the actin cytoskeleton and an increase in the total number of E-cadherin/gamma-catenin complexes on the cell surface during HGF-induced dedifferentiation of polarized renal epithelium. These data support the hypothesis that E-cadherin function is inhibited by a mechanism of detachment from the actin based cytoskeleton during HGF induced dedifferentiation of polarized renal epithelia.