GRANZYME-B PERFORIN-MEDIATED APOPTOSIS OF JURKAT CELLS RESULTS IN CLEAVAGE OF POLY(ADP-RIBOSE) POLYMERASE TO THE 89-KDA APOPTOTIC FRAGMENT AND LESS ABUNDANT 64-KDA FRAGMENT

Cytotoxic lymphocytes utilize granule associated serine proteases (gra nzymes) and perforin to induce apoptosis. Although the importance of g ranzyme B has been established by gene ablation experiments, biochemic al events initiated by the granzyme remain enigmatic. We show here tha t exposure of Jurkat cells to granzyme B and perforin results in cleav age of poly(ADP-ribose) polymerase to an apoptotic 89 kDa fragment and to lesser amounts of a 64 kDa fragment. The 64 kDa fragment is produc ed directly by granzyme B while the 89 kDa fragment is presumably gene rated by activated ICE/Ced-3 proteases. Establishing the intracellular function of GrB in the apoptotic response, these results indicate tha t granzyme B enters perforin treated targets activating the ICE/Ced-3 family proteases which then cleave poly(ADP-ribose) polymerase to its apoptotic fragment. Intracellular granzyme B appears to be translocate d to the nucleus where the protease directly cleaves poly(ADP-ribose) polymerase. (C) 1996 Academic Press, Inc.