SPHINGOSINE 1-PHOSPHATE INHIBITS ACTIVATION OF CASPASES THAT CLEAVE POLY(ADP-RIBOSE) POLYMERASE AND LAMINS DURING FAS-MEDIATED AND CERAMIDE-MEDIATED APOPTOSIS IN JURKAT T-LYMPHOCYTES

Ceramide, a sphingolipid generated by the hydrolysis of membrane-assoc iated sphingomyelin, appears to play a role as a gauge of apoptosis. A further metabolite of ceramide, sphingosine 1-phosphate (SPP), preven ts ceramide-mediated apoptosis, and it has been suggested that the bal ance between intracellular ceramide and SPP levels may determine the c ell fate (Cuvillier, O., Pirianov, G, Kleuser, B., Vanek, P. G., Coso, O. A., Gut-kind, J. S., and Spiegel, S. (1996) Nature 381, 800-803). Here, we investigated the role of SPP and the protein kinase C activat or, phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), in the c aspase cascade leading to the proteolysis of poly(ADP-ribose) polymera se (PARP) and lamins. In Jurkat T cells, Fas ligation or addition of e xogenous C-2-ceramide induced activations of caspase-3/CPP32 and caspa se-7/Mch3 followed by PARP cleavage, effects that can be blocked eithe r by SPP or TPA. Furthermore, both SPP and TPA inhibit the activation of caspase-6/Mch2 and subsequent lamin B cleavage. Ceramide, in contra st to Fas ligation, did not induce activation of caspase-8/FLICE and n either SPP nor TPA were able to prevent this activation. Thus, SPP, li kely generated via protein kinase C-mediated activation of sphingosine kinase, suppresses the apoptotic pathway downstream of FLICE but upst ream of the executioner caspases, caspase-3, -6, and -7.