Caspases Cleave the Amino-Terminal Calpain Inhibitory Unit of Calpastatin during Apoptosis in Human Jurkat T Cells

摘要: We have previously reported the activation of procalpain mu (precursor for low-calcium-requiring calpain) in apoptotic cells using a cleavage-site-directed antibody specific to active calpain [Kikuchi, H. and Imajoh-Ohmi, S. (1995) Cell Death Differ. 2, 195-199]. In this study, calpastatin, endogenous inhibitor protein calpain, was cleaved 90-kDa polypeptide during apoptosis human Jurkat T cells. The limited proteolysis calpastatin preceded autolytic procalpain. Inhibitors caspases rescued from simultaneously inhibited cleavage calpastatin. full-length recombinant also by caspase-3 or caspase-7 at Asp-233 into same size fragment. Cys-241 targeted these vitro but not Caspase-digested lost its amino-terminal inhibitory unit, three moles per mole. Our findings suggest that trigger decontrol activity suppression degrading