Effect of disrupting cell contact on the nuclear accumulation of beta-catenin and subsequent apoptosis of rat ovarian surface epithelial cells in vitro.

The present studies were designed to determine how disrupting cell contact induces rat ovarian surface epithelial cells (i.e., ROSE-179 cells) to undergo apoptosis. In the first series of studies, the effect of depleting serum and calcium on the levels of the adhesion proteins N-cadherin and beta-catenin was examined. These studies revealed that the depletion of serum and calcium results in the degradation of N-cadherin but not beta-catenin. However, the localization of beta-catenin changed from principally the plasma membrane to the nucleus. The nuclear localization of beta-catenin was demonstrated by Western blot and confocal microscopy. A second series of studies demonstrated that cells that lost contact in response to the depletion of serum and calcium showed enhanced beta-catenin-dependent transcription. Finally, forced expression of a stable form of beta-catenin resulted in an increase in beta-catenin within the cytoplasm of transfected ROSE-179 cells. When these beta-catenin transfected ROSE-179 cells were deprived of serum and calcium, beta-catenin accumulated within the nucleus and accelerated the rate at which these cells became apoptotic. These data indicate that in viable cells, beta-catenin is part of the adhesion complex that maintains cell contact. If calcium-dependent cell contacts are broken, beta-catenin accumulates within the nucleus, where it promotes transcription and ultimately the apoptotic death of ROSE-179 cells.