TRAIL-induced apoptosis proceeding from caspase-3-dependent and -independent pathways in distinct HeLa cells

• Published in: Biochemical and biophysical research communications 2006-08, Vol.346 (4), p.1136-1141
• Main Authors: Lin, Juqiang, Zhang, Zhihong, Zeng, Shaoqun, Zhou, Shixia, Liu, Bi-Feng, Liu, Qian, Yang, Jie, Luo, Qingming
• Format: Article
• Language: English
• Subjects: Apoptosis - physiology; Apoptosis Regulatory Proteins - physiology; Capillary electrophoresis (CE); Caspase; Caspase 3; Caspases - metabolism; Fluorescence resonance energy transfer (FRET); HeLa Cells; Humans; Membrane Glycoproteins - physiology; TNF-Related Apoptosis-Inducing Ligand; Tumor Cells, Cultured; Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL); Tumor Necrosis Factor-alpha - physiology
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2006.05.209

The apoptotic pathway in higher eukaryotes remains controversial with respect to the necessity of activation of caspase-3 in TRAIL (tumor necrosis factor-related apoptosis-inducing ligand)-treated cells. In this study, a fluorescence resonance energy transfer (FRET) probe was developed to image the activation of caspase-3 and the related apoptotic pathway in TRAIL-treated cells in real time. Both kinds of apoptotic pathways were observed simultaneously in the same experiment proceeding from activation and non-activation of caspase-3. The total apoptotic rate was 56.08%, the apoptotic rates for activation and non-activation of caspase-3 pathways were 21.5% and 34.58%, respectively, which were examined later for Hoechst 33258 staining and morphological characteristics. The apoptotic rate due to the activation of caspase-3 pathways in TRAIL-treated cells has been independently measured to be around 25.11% by capillary electrophoresis (CE) analysis, which confirmed the apoptotic rate due to activation of caspase-3 pathways as found by FRET analysis. This result also suggests that rest apoptosis is preceded by caspase-3-independent pathways, as CE has the ability to quantitatively detect caspase-dependent apoptosis. The observation of the coexistence of caspase-3-dependent and caspase-3-independent apoptotic pathways in the TRAIL-treated cells was unusual in comparison with the previous reports.