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A Caenorhabditis elegans Model System for Amylopathy Study
Published on: May 17, 2013
Caenorhabditis elegans CED-4 stimulates CED-3 processing and CED-3-induced apoptosis
1Department of Entomology, University of Georgia, Athens, Georgia 30602, USA.
Background:
Programmed cell death or apoptosis is a key feature of normal development, tissue homeostasis and disease progression in metazoans. Genetic studies in the nematode C. elegans have identified three key genes involved in apoptosis, ced-3, ced-4 and ced-9. Expression of ced-3 and ced-4 is required for the induction of cell death, whereas expression of ced-9 is necessary to inhibit cell death. The precise mechanism by which these genes influence the life or death decision of a cell is not known. In this study, we have expressed the genes in an insect cell line to explore their role in the apoptotic pathway.
Results:
Co-expression of ced-4 with ced-3 in insect cells stimulated both the induction and the level of CED-3-mediated apoptosis. Stimulation of CED-3-dependent apoptosis by CED-4 was accompanied by accelerated processing of CED-3, which was dependent on the presence of a wild-type CED-3 prodomain and a conserved lysine residue within a putative ATP/GTP-binding motif of CED-4. Co-expression of ced-9 with ced-4 and ced-3 inhibited the ability of CED-4 to stimulate CED-3 processing and CED-3-dependent apoptosis. Although a temperature-sensitive CED-9 mutant was unable to block CED-4 activity and failed to associate with CED-4, a deletion mutant of CED-9 lacking the carboxy-terminal hydrophobic domain could associate with CED-4 and block CED-4 activity.
Conclusions:
Our results establish a role for CED-4 in the processing of CED-3 and the stimulation of CED-3-induced apoptosis. Furthermore, we show that CED-9 achieves its anti-apoptotic effect by associating with CED-4 and blocking the ability of CED-4 to process CED-3.
Insights
The C. elegans genes CED-4 and CED-3 induce apoptosis, while CED-9 inhibits it. CED-4 processes CED-3 to promote cell death, and CED-9 blocks this by binding to CED-4.
Area of Science:
- Cellular biology
- Molecular genetics
- Developmental biology
Background:
- Apoptosis, or programmed cell death, is crucial for development and homeostasis.
- Key genes in C. elegans apoptosis are ced-3 (induces death), ced-4 (induces death), and ced-9 (inhibits death).
- The precise molecular mechanisms of these apoptosis regulators remain unclear.
Purpose of the Study:
- To investigate the roles of C. elegans apoptosis genes ced-3, ced-4, and ced-9.
- To elucidate the mechanism of CED-4-mediated apoptosis induction.
- To determine how CED-9 inhibits apoptosis.
Main Methods:
- Expression of C. elegans genes (ced-3, ced-4, ced-9) in an insect cell line.
- Analysis of CED-3 processing and apoptosis induction.
- Investigation of protein interactions between CED-4 and CED-9 mutants.
Main Results:
- Co-expression of CED-4 with CED-3 stimulated CED-3 processing and apoptosis.
- CED-4's pro-apoptotic activity required a functional CED-3 prodomain and a specific motif in CED-4.
- CED-9 inhibited CED-4's ability to process CED-3 and induce apoptosis.
- A CED-9 mutant lacking its hydrophobic domain associated with CED-4 and blocked its activity.
Conclusions:
- CED-4 plays a critical role in processing CED-3 to induce apoptosis.
- CED-9 inhibits apoptosis by interacting with CED-4 and preventing CED-3 processing.
- These findings clarify the molecular interactions governing apoptosis in C. elegans.
