Suppression of okadaic acid-induced apoptosis by overexpression of calpastatin in human UVr-1 cells

Proteolytic systems have various involvements in apoptotic pathways. To und erstand the role of calpain in apoptosis, calpastatin, a specific inhibitor of calpain, was overexpressed in human UVr-1 fibroblasts by transfection o f its cDNA, The elevated expression of calpastatin resulted in decreased su rvival in the presence of okadaic acid (OA) but in no apparent alteration i n the sensitivity toward other drugs such as 5-fluorouracil, mitomycin C an d methotrexate, After treatment with OA, a typical apoptotic DNA ladder was observed in control vector-transfected cells but not in calpastatin-transf ected cells. This indicates that OA-indnced apoptosis was suppressed by ove rexpression of calpastatin, Further immunoblot analysis showed that the OA- induced hyperphosphorylation of c-Jun was inhibited in calpastatin-transfec ted cells. This might be involved in the resistance to OA-induced cell deat h in calpastatin-overproducing cells. (C) 1999 Federation of European Bioch emical Societies.