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Alpha-sarcin catalytic activity is not required for cytotoxicity
Spencer C Alford1, Joel D Pearson, Amanda Carette
1Centre for Biomedical Research, University of Victoria, PO Box 3020 Station CSC Victoria, British Columbia, V8W 3N5, Canada. alford@ualberta.ca
BMC Biochemistry
|April 7, 2009
Summary
Alpha-sarcin toxin from Aspergillus giganteus can kill cells independently of inhibiting protein synthesis. Catalytically inactive mutants retain cytotoxicity, suggesting a novel cell death pathway beyond rRNA cleavage.
Area of Science:
- Molecular Biology
- Cell Biology
- Toxicology
Background:
- Alpha-sarcin is a cytotoxic ribonuclease from Aspergillus giganteus.
- It inhibits protein synthesis by cleaving ribosomal RNA (rRNA).
- The role of protein synthesis inhibition in alpha-sarcin-induced cell death is debated.
Purpose of the Study:
- To investigate alpha-sarcin cytotoxicity and protein synthesis inhibition via direct cytoplasmic expression.
- To determine if catalytically inactive alpha-sarcin mutants are toxic.
- To explore the mechanism of alpha-sarcin-induced cell death.
Main Methods:
- Expression of wildtype and mutant alpha-sarcin in cell cytoplasm.
- Assay of protein synthesis inhibition.
- Cytotoxicity assays.
- JNK activation analysis.
- Subcellular localization studies using RPS6 as a ribosomal marker.
Main Results:
- Mutant alpha-sarcin, unable to inhibit protein synthesis, remained cytotoxic.
- Mutants were catalytically inactive, confirmed by lack of JNK activation.
- Both wildtype and mutant alpha-sarcin localized to the nucleus and cytoplasm, co-localizing with RPS6.
Conclusions:
- Protein synthesis inhibition is not strictly required for alpha-sarcin-induced cell death.
- Alpha-sarcin can induce cell death through a mechanism independent of rRNA cleavage and JNK activation.
- A novel, unappreciated cell death pathway mediated by alpha-sarcin is suggested.
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