Fig. 9.

Pinocytic loading of B16-F1 cells with SO-M80 cyt c does not activate caspases. (A) Cells were loaded with nothing (control) or native or SO-M80 cyt c (20 µM) via pinocytosis with overnight incubation. After loading, cells were fixed and probed with mAb 1D3 (green), anti-cyt c (6H2.B4, red), and nuclear staining (DAPI) and analyzed by confocal microscopy. Horizontal scale bars indicate 25 µm. (B) Cell viability was measured by trypan blue assay. No differences in cell population were observed between control and cell pinocytically loaded with SO-M80 cyt c. (C) Purified cyt c or SO-M80 cyt c (20 µg) were added to cytosolic extracts of Jurkat cells (2 mg/mL) in the presence of dATP and ATP. Caspase-3 activity was measured using the fluorogenic substrate DEVD-AFC at λex = 400 and λem = 505 nm.