Caspase-1 is not involved in CD95/Fas-induced apoptosis in Jurkat T cells

It is now well established that the caspases, a family of cysteine protease s, play a key role in apoptosis. Although overexpressing each of the caspas es in cells triggered apoptosis, the precise role and contribution of indiv idual caspases are still unclear. Caspase-1, the first caspase discovered, was initially implicated in mammalian apoptosis because of its similarity t o the gene product ced-3 Using whole cells as well as an in vitro system to study apoptosis, the role of caspase-1 in Fas-mediated apoptosis in Jurkat T cells was examined in greater detail. Using various peptide-based caspas e inhibitors, our results showed that N-acetyl-Tyr-Val-Ala-Asp chloromethyl ketone and benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone efficie ntly blocked Fas-mediated apoptosis in Jurkat T cells, whereas N-acetyl-Tyr -Val-Ala-Asp aldehyde, which is more specific for caspase-1, had little eff ect. Cell lysates derived from anti-Fas-stimulated cells, which readily ind uced apoptotic nuclei morphology and DNA fragmentation in isolated thymocyt e nuclei, had no caspase-1 activity using proIL-1 beta as a substrate. Time -course studies showed no caspase-1 activity during the activation of apopt osis in Jurkat cells by agonistic Fas antibodies,]Furthermore, no pro-caspa se-1 protein nor activated form of the protein was detected in normal or ap optotic Jurkat cells. In contrast, both caspase-2 and caspase-3 were readil y detected as proenzymes in control cells and their activated forms were de tected in apoptotic cells, Incubation of recombinant active caspase-1 with control cell lysates did not activate the apoptotic cascade as shown by the lack of detectable apoptotic nuclei promoting activity using isolated nucl ei as substrate. However, under similar conditions proIL-1 beta was readily processed into the mature cytokine, indicating that the recombinant caspas e-1 remained active in the presence of control cell lysates, Taken together our results demonstrate that caspase-1 is not required for the induction o f apoptosis in Jurkat T cells mediated by the Fas antigen. (C) 1999 Academi c Press.