Simultaneous measurement of the caspase-3 and caspase-9 activities during induced apoptosis by fluorescence cross-correlation spectroscopy

Abstract

Dual color fluorescence cross-correlation spectroscopy (FCCS) provides information about the coincidence of two spectrally well-defined fluorescent molecules in a small detection volume at the single-molecule level. To expand the capability of FCCS measurement, we constructed a chimera that consisted of tandem fused fluorescent proteins with three colors for the simultaneous evaluation of the caspase-3 and caspase-9 activities. Using FCCS, we found the apoptosis-induced caspase-3 and caspase-9 activation to be detectable by decreases in the cross-correlation amplitudes both in vitro and in living cells. Here we report the simultaneous detection of caspase-3 and caspase-9 activation in living cells.