Figure 1.

Caspase-mediated cleavage of β-catenin promotes changes in cell adhesion and cell shape (a) Drosophila; (b) mammals. Adherens junctions are composed of adhesion complexes of E-cadherin (gray bars), β-catenin (Armadillo (Arm); green ovals) and α-catenin (α-cat; blue circles), which link to the actin cytoskeleton. When apoptosis is induced, DrICE in Drosophila or its homolog caspase-3 in mammals are activated in the apoptotic cell (dark gray). DrICE cleaves Armadillo near the amino terminus (ArmΔN), whereas mammalian capsase-3 cleaves β-catenin near both the amino and carboxyl termini. In Drosophila, an early stage of apoptosis has been described in which the cleaved form of Armadillo remains at the membrane linked to α-catenin, whereas E-cadherin is removed from the membrane by an unknown mechanism. In mammals, nothing is known so far about an intermediate step in adherens junction degradation in response to induction of apoptosis. At a later stage of apoptosis, all adherens junction components are removed from the membrane and the actin cytoskeleton retracts. Meanwhile, neighboring cells form new adherens junctions with each other and close the gap created by the retraction of the dying cell.