title: ROS-triggered caspase 2 activation and feedback amplification loop in beta-carotene-induced apoptosis.
abstract: Reactive oxygen species (ROS) and caspases 8, 9, and 3 are reported to be crucial players in apoptosis induced by various stimuli. Recently, caspase 2 has been implicated in stress-induced apoptosis but the exact mechanism remains unclear. In this study, we report that ROS generation led to activation of caspase 2 during beta-carotene-induced apoptosis in the human leukemic T cell line Molt 4. The apoptosis progressed by simultaneous activation of caspases 8 and 9, and a cross talk between these initiator caspases was mediated by the proapoptotic protein Bid. Inhibition of caspases 2, 8, 9, and 3 independently suppressed the caspase cascade. The kinetics and function of caspase 2 were similar to those of caspase 3, suggesting its role as an effector caspase. Interestingly, beta-carotene-induced apoptosis was caspase 2 dependent but caspase 3 independent. The study also revealed cleavage of the antiapoptotic protein BclXL as an important event during apoptosis, which was regulated by ROS. The mechanistic studies identify a functional link between ROS and the caspase cascade involving caspase 2 and cleavage of BclXL. The interdependence of caspases 8, 9, 2, and 3 in the cascade provides evidence for the presence of an extensive feedback amplification loop in beta-carotene-induced apoptosis in Molt 4 cells.
authors.affiliation: National Centre for Cell Science, Ganeshkhind, Pune 411 007, India.
authors.forename: Vandna
authors.initials: V
authors.lastname: Prasad
authors.forename: Anmol
authors.initials: A
authors.lastname: Chandele
authors.forename: Jayashree C
authors.initials: JC
authors.lastname: Jagtap
authors.forename: P
authors.initials: P
authors.lastname: Sudheer Kumar
authors.forename: Padma
authors.initials: P
authors.lastname: Shastry
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053143:Caspase 2 / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D019207:beta Carotene / Q000494:pharmacology*
chemical_list: D053222:Fas Ligand Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D019207:beta Carotene; D053143:Caspase 2; D053148:Caspase 3