Specific cleavage of γ catenin by caspases during apoptosis

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Abstract
Caspase‐mediated proteolysis of cytoskeletal proteins during apoptosis appears to be commonplace. Enlarging on previous studies we have shown here that γ catenin, like β catenin, was degraded during cisplatin‐induced apoptosis, initially giving a major product of 75 kDa. This truncated protein could be co‐immunoprecipitated with α catenin. Addition of caspase inhibitors to cells in the presence of cisplatin appreciably reduced the proteolysis of γ catenin as well as the level of apoptosis. Only limited degradation of α catenin was observed even at very late times when over 90% of cells in the culture were apoptotic. Immunohistochemical staining showed that during apoptosis there was a relocation of α, β and γ catenin from the periphery of the cell to the cytoplasm, at the same time as other morphological changes commonly associated with apoptosis occurred. Interestingly, the changes in localisation of the catenins preceded proteolysis by several hours. In the presence of cisplatin and caspase inhibitor no change in distribution of catenins was observed, suggesting that re‐localisation requires caspase activity but not necessarily directed against β and γ catenins.