FIG. 7.

Upon PMA stimulation, β-catenin accumulates at the cell-cell contacts. (A) Western blot analysis of β-catenin distribution. Soluble (s) and membrane (m) fractions of untreated or PMA-treated GH3B6 cells were subjected to SDS-PAGE and Western blotting using an anti-β-catenin antibody. In basal conditions, β-catenin was found in soluble and membrane fractions. PMA treatment induced β-catenin accumulation in the membrane fraction. (B and C) GH3B6 cells transfected with hPKCα-wt–GFP (B, top) or hPKCα-D294G–GFP (C, top) were analyzed for β-catenin localization by immunocytochemistry with an anti- β-catenin antibody (B and C, bottom) in basal conditions (left) and after 1 h of PMA treatment (right). In basal conditions, β-catenin immunoreactivity was found in the cytoplasm and at the plasma membrane, whereas hPKCα-wt–GFP and hPKCα-D294G–GFP were cytoplasmic. PMA stimulation induced the redistribution of β-catenin to cell-cell contacts. Merged image: green, hPKCα-wt–GFP or hPKCα-D294G–GFP; red, β-catenin. (D) Accumulation of β-catenin at the cell-cell contacts induced by PMA treatment depends on the reorganization of F-actin at the cell-cell contacts. Immunostaining of β-catenin of cells treated with cytochalasin D in the absence or in the presence of 100 nM PMA. In the presence of cytochalasin D, β-catenin is no more accumulated at the cell-cell contacts upon PMA stimulation. Bars, 5 μm.