Figure 1.

Schematic overview of the pcFluc-DEVD system. The reporter gene is composed of an engineered firefly luciferase, of which the N- and C-terminals are linked with DEVD, a substrate sequence of caspase-3. Upon caspase-3 activation during apoptosis, the DEVD sequence is cleaved and the cyclized luciferase recovers its activity. This biosensor can be used for imaging apoptosis induced by various therapeutic interventions to monitor effects of cytotoxic compounds or novel pharmacological chemicals, as most cells activate caspase-3 during apoptosis. The cleavage site of this system can also be modified to “report” on the kinetics of a variety of proteolytic processes in vitro and in vivo by using bioluminescence imaging.