DrlCE is an essential caspase required for apoptotic activity in Drosophila cells

Caspases are involved in the execution of cell death in all multicellular organisms so far studied,including the nematode worm, fruit fly and vertebrates, While Caenorhabditis elegans has snag a single identified for all developmental programmed cell deaths, most varying specificities, The fruit Drosophila melanogaster is genetically tractable, less complex than vertebrates and possesses two known caspases, DCP-I and drICE. The fly may therefore provide a good model system for examining the hierarchy and relative roles of individual caspases ire the execution of apoptosis. We have examined the role off drICE in in vitro apoptosis of the D.melanogaster cell line S2. We show that cytoplasmic lysates made from S2 cells undergoing apoptosis induced by either reaper (rpr) expression as cycloheximide treatment contain a caspase activity with DEVD specificity which can cleave p35, Iamin DmO, drICE and DCP-1 in vitro, and which can trigger chromatin condensation in isolated nuclei, Using antibodies specific to drICE, we show that immunodepletion of drICE from these lysates is sufficient to remove most measurable in vitro apoptotic activity, and that readdition of exogenous drICE to such immunodepleted IJ sates restores apoptotic activity, We conclude that, at least in S2 cells, drICE can be the sale caspase effector of apoptosis.