Selective disruption of cadherin/catenin complexes by oxidative stress in precision-cut mouse liver slices.

Abstract

Previous work has shown that chemically induced oxidative stress disrupts the protein interactions of the E-cadherin/beta-catenin/alpha-catenin complex in precision-cut mouse liver slices (Parrish et al., 1999, Toxicol. Sci. 51, 80-86). Although these data suggest a role for oxidative stress in disruption of hepatic cadherin/catenin complexes, multiple complexes are co-expressed in the liver. Both E- and N- cadherin are co-expressed in hepatocytes, as well as beta-catenin and gamma-catenin; thus four distinct complexes mediate cell-cell adhesion in the liver: E-cadherin/beta-catenin/alpha-catenin, E-cadherin/gamma-catenin/alpha-catenin, N-cadherin/beta-catenin/alpha-catenin, and N-cadherin/gamma-catenin/alpha-catenin. Taking advantage of the retention of normal organ architecture and cellular heterogeneity offered by precision-cut mouse liver slices, the current study was designed to examine the impact of chemically induced oxidative stress on cadherin/catenin complexes. Precision-cut mouse liver slices were challenged with diamide (25-250 microM; 6 h) or tert-butylhydroperoxide (5-50 microM; 6 h). A polyclonal antibody against beta- or gamma-catenin was used to immunoprecipitate proteins prior to Western-blot analysis with monoclonal antibodies to E- or N-cadherin. Although a decrease in E-cadherin:beta-catenin co-immunoprecipitation was seen, interactions between beta-catenin and N-cadherin were not disrupted by chemical challenge. In addition, no effect on protein interactions of gamma-catenin with either cadherin was observed. Indirect immunofluorescence was used to co-localize catenins and cadherins following chemical challenge. Consistent with the biochemical observations, a heterogeneous reduction in co-localization of E-cadherin and beta-catenin was seen in precision-cut liver slices, but not other cadherin/catenin complexes. Taken together, these data suggest that oxidative stress selectively disrupts E-cadherin/beta-catenin complexes in the liver. This response is dictated, in part, by the protein composition of the cell-adhesion complex.