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Abrin triggers cell death by inactivating a thiol-specific antioxidant protein
1Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei 10081, Taiwan, Republic of China.
The Journal of Biological Chemistry
|April 4, 2001
Summary
Abrin A-chain (ABRA) binding inhibits antioxidant protein-1 (AOP-1), increasing reactive oxygen species (ROS) and triggering programmed cell death. This reveals a novel mechanism for ABRA-induced apoptosis.
Area of Science:
- Cell Biology
- Biochemistry
- Toxicology
Background:
- Abrin A-chain (ABRA) is known to inhibit protein synthesis and induce apoptosis.
- The precise molecular mechanisms underlying ABRA-induced cell death remain largely unknown.
Purpose of the Study:
- To elucidate the molecular mechanism of ABRA-induced apoptosis.
- To identify proteins that interact with ABRA and mediate its cytotoxic effects.
Main Methods:
- Yeast two-hybrid screening using an ABRA mutant.
- Glutathione S-transferase (GST) pull-down assays for interaction confirmation.
- Confocal immunofluorescence microscopy for protein colocalization.
- Measurement of reactive oxygen species (ROS) levels.
- Assessment of apoptosis markers like cytochrome c release and caspase activation.
Main Results:
- Antioxidant protein-1 (AOP-1) was identified as an ABRA-interacting protein.
- ABRA binding was shown to inhibit AOP-1's antioxidant activity, leading to increased intracellular ROS.
- ROS scavengers delayed ABRA-induced apoptosis, confirming ROS as key mediators.
- Ectopic expression of AOP-1 protected cells from ABRA-induced apoptosis by preventing cytochrome c release.
Conclusions:
- ABRA promotes apoptosis by binding to and inhibiting the mitochondrial antioxidant protein AOP-1.
- This inhibition leads to elevated ROS levels and subsequent cytochrome c release, activating the caspase cascade.
- The findings reveal a novel pathway for ABRA-mediated cytotoxicity involving oxidative stress.