STRICA, a novel Drosophila melanogaster caspase with an unusual serine/threonine-rich prodomain, interacts with DIAP1 and DIAP2.

The recently published genome sequence of Drosophila melanogaster predicts seven caspases in the fly. Five of these caspases have been previously characterised. Here, we describe the Drosophila caspase, STRICA. STRICA is a caspase with a long amino-terminal prodomain that lacks any caspase recruitment domain or death effector domain. Instead, the prodomain of STRICA consists of unique serine/threonine stretches. Low levels of strica expression were detected in embryos, larvae, pupae and adult animals. STRICA is a cytoplasmic protein that, upon overexpression, caused apoptosis in cultured Drosophila SL2 cells that was partially suppressed by DIAP1. Interestingly, unlike other fly caspases, STRICA showed physical association with DIAP2, in cotransfection experiments. These results suggest that STRICA may have a unique cellular function.