Figure 6.

Changes in β-catenin distribution between nuclear and cytosolic compartments after growth factor removal (a–d). Control (a and b) and viable HUVEC (c and d) were stained with anti-β-catenin antibody (^571–781 C) and analyzed by confocal microscopy. In control cells, staining at the bottom level of the cells can be detected in adherens junctions (arrows in a). In contrast, after growth factor removal (c), increased peripheral staining is observed, despite the lack of cell–cell contact (arrows), and an increase in punctate cytosolic staining is observed as well (arrowheads). Images 4 μm above the bottom level (b and d) are shown for the same cells analyzed in panels a and c. In control cells (b), some of the adherens junction staining (arrows) is still visible. In contrast, after growth factor removal (d), perinuclear and nuclear staining is prominent (arrowheads). (e) Cytosolic (cyt) and nuclear (nuc) extracts of HUVEC grown in full growth medium (control) and of pooled HUVEC (apoptotic and viable cells) 5 h after growth factor removal were prepared as described in MATERIALS AND METHODS. The equivalent of 200,000 cells/fraction was separated on 7.5% SDS-PAGE, transferred to Immobilon, and analyzed for the presence of β-catenin with the anti-β-catenin antibody ^571–781 C. Growth factor removal leads to a selective reduction of native β-catenin in the cytosol, while the cleaved apoptotic fragments of β-catenin are found in both the cytosol and the nucleus, except for fragment E, which appears only in the nuclear fraction.