The molecular mechanism of apoptosis upon caspase-8 activation: Quantitative experimental validation of a mathematical model

► A monitoring system with high sensitivity FRET-based biosensors has been developed. ► The established system enabled us to detect the most minute dynamics of caspase activation in single cells. ► The kinetics, dynamics, and selectivity in apoptotic signaling pathways with activation of caspase-8 were redefined. ► The actual number of pro-apoptotic molecules required for extrinsic apoptotic signal transduction was evaluated. ► A mathematical model predicted the minimal concentration of caspase-8 required to act as an initiator.