Mitochondrial apoptosis inducing factor (AIF) on activation can translocate to the nucleus and induce cell death via
caspase-independent pathway in cisplatin-induced apoptosis. Yet the precise signal transduction pathway(s) which
regulates AIF-induced apoptotic pathway still remains poorly understood. In this study, we investigated the molecular
mechanism of AIF release and redistribution in cisplatin-induced apoptosis in living ASTC-a-1 cells, as assessed by
real-time anlysis. Herein, We report that during cisplatin-induced apoptosis, calpain activation, as measured in intact
cells by a fluorescent substrates, is an early event, taking place well before AIF release and caspase-3 activation.
Confocal imaging of the cells transfected with AIF-GFP demonstrated that AIF release occurred about 9 h after cisplatin
treatment. The event proceeded progressively over time, coinciding with a nuclear translocation and lasting for more
than 2 hours. AIF release and redistribution were effectively inhibited in samples co-treated with calpeptin and
PD150606, two selective calpain inhibitors. Therefore, our results clearly show the kinetics of AIF release and
redistribution in cisplatin-induced apoptosis in living ASTC-a-1 cells, and calpain played a crucial role in these events.