Sequential activation of three distinct ICE-like activities in Fas-ligated Jurkat cells

ICE family proteases have been implicated as important effecters of the apoptotic pathway, perhaps acting hierarchically in a protease cascade, Using cleavage of endogenous protease substrates as probes, three distinct tiers of ICE-like activity were observed after Pas ligation in Jurkat cells, The earliest cleavage detected (30 min) was of fodrin, and produced a 150 kDa fragment. The second phase of cleavage (50 min) involved PARP, U1-70kDa and DNA-PKcs, all substrates of the CPP32-like proteases, Lamin B cleavage,vas observed during the third cleavage phase (90 min), Distinct inhibition profiles obtained using a panel of peptide-based inhibitors of ICE-like proteases clearly distinguished the three different cleavage phases, These studies provide evidence for a sequence of ICE-like proteolytic activity during apoptosis, The early fodrin cleavage, producing a 150 kDa fragment, identifies an ICE-like activity proximal to CPP32 in Fas-induced Jurkat cell apoptosis.