Abrin belongs to the type II family of ribosome-inactivating proteins comprising a galactose-binding B chain coupled with a toxic A chain through a single disulphide linkage. Apart from its RNA-N-glycosidase activity, another role that has been recently ascribed to abrin was the induction of apoptosis. Studies were undertaken to determine the kinetics of these two activities. In the present study, we report that the signal for apoptosis is triggered at a time point later than the inhibition of protein synthesis. This apoptotic pathway induced by abrin is caspase 3-dependent but caspase 8-independent and involves mitochondrial membrane potential damage and reactive oxygen species production. Overexpression of B-cell lymphocytic-leukaemia proto-oncogene 2 was found to block this apoptotic pathway.
- DNA fragmentation
- mitochondrial membrane potential
- protein synthesis inhibition
- reactive oxygen species
Abbreviations used: Ac-DEVD-AMC, N-acetyl-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin; Ac-DEVD-CHO, N-acetyl-Asp-Glu-Val-Asp-CHO (aldehyde); AcOr, Acridine Orange; Bcl-2, B-cell lymphocytic-leukaemia proto-oncogene 2; DCFH-DA, 2´,7´-dichloro dihydro fluorescein diacetate; EtBr, ethidium bromide; FasL, Fas ligand; FBS, foetal bovine serum; JC-1, 5,5´,6,6´-tetrachloro-1,1´,3,3´-tetraethylbenzimidazolyl carbocyanine iodide; ML, mistletoe lectin; MMP, mitochondrial membrane potential; PARP, poly(ADP-ribose) polymerase; PI, propidium iodide; RIP, ribosome-inactivating protein; ROS, reactive oxygen species.
- The Biochemical Society, London ©2004