Cleavage of the C-terminal cytoplasmic domain of occludin during apoptosis generates a fragment that can no longer associate with the cytoplasmic adapter proteins ZO-1, -2 and -3 and, as a consequence, with the actin cytoskeleton (Bojarski et al., 2003). Cleavage of ZO-1 and ZO-2 further disrupts tight junction structure and function. Notably, claudins, which are associated with ZO-1, ZO-2 and ZO-3, completely lose their linkage to the actin cytoskeleton and other ZO-1-, ZO-2-, ZO-3-interacting proteins (Bojarski et al., 2003). Inhibition of caspase-3 prevents cleavage of ZO-2, implicating caspase-3 as the responsible endopeptidase (Bojarski et al. 2004).