Spatiotemporal differences in activation of caspase-6 in staurosporine treated neuroblastoma cells. Differentiated SH-SY5Y cells expressing the caspase-6 (VEID) sensor molecule treated with 10 μM staurosporine were monitored by FRET time-lapse microscopy. (A) Images at 10 min intervals from a FRET time-lapse experiment. Time points relative to the FRET intensity change of the left cell are indicated at the top. The frame before the initial drop in FRET intensity was chosen as zero time point. The relative FRET intensity is shown in graphs corresponding to the left and right cell, respectively. The different graphs are from cell soma (blue squares); neurite 1 (red dots); neurite 2 (green triangles); neurite 3 (red rhombuses); neurite 4 (green crosses). Note the localized loss of FRET signal in the soma, which appeared earlier than in neurites. (B) Statistical analysis of spatiotemporal differences in FRET intensity of cell bodies (left, blue) and neurites (right, red) from different experiments (n = 8; mean ± S.E.M.). The FRET signals in cell bodies were significantly lower than the FRET signals in neurites at 5 min (p < 0.05), 10 min (p < 0.01) and 15 min (p < 0.05).