Selective and sensitive monitoring of caspase-1 activity by a novel bioluminescent activity-based probe

The role of Caspase-1 in inflammation has been studied intensely over recent years. However, the research of Caspase-1 has remained difficult mainly due to the lack of sensitive and selective tools to monitor not only its abundance but also its activity. Here we present a bioluminescent activity-based probe (ABP) for Caspase-1, developed by the Reverse Design concept, where chemically optimized Protease Inhibitors are turned into selective substrate ABPs. The probe exhibits excellent selectivity for Caspase-1 and ∼1000-fold increase in sensitivity compared to available fluorogenic peptidic Caspase-1 substrates. Moreover, we have been able to monitor and quantify specific Caspase-1 activity directly in cell lysates. The activity correlated well with processing of prointerleukin-1β and prointerleukin-18 in phorbol 12-myristate 13-acetate (PMA)-stimulated cells. A detectable Caspase-1 activity was present also in nonstimulated cells, consistent with processing of constitutively expressed prointerleukin-18.