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Updated: Sep 5, 2026
Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
Published on: March 5, 2018
Caspase-2 (Nedd-2) processing and death of trophic factor-deprived PC12 cells and sympathetic neurons occur
1Department of Pathology, Taub Center for Alzheimer's Disease Research and Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Abstract:
We have previously shown that caspase-2 (Nedd-2) is required for apoptosis induced by withdrawal of trophic support from PC12 cells and sympathetic neurons. Here, we examine the relationship of caspase-2 processing and cell death to induction of caspase-3 (CPP32)-like activity in PC12 cells. Caspase-2 processing, at a site tentatively identified as D333, led to the formation of an N-terminal 37 kDa product. This processing correlated temporally with induction of caspase-3-like activity. Agents previously shown to inhibit caspase-3-like activation, such as bcl-2 and the Cdk inhibitor flavopiridol, also acted upstream of caspase-2 processing. The general caspase inhibitors BAF and zVAD-FMK inhibited N-terminal caspase-2 processing. In contrast, the more selective caspase inhibitor DEVD-FMK inhibited the induction of caspase-3-like activity but did not affect caspase-2 processing or significantly suppress death in PC12 cells or sympathetic neurons. This indicates that caspase-3-like activity is not required for either caspase-2 processing or apoptosis in this paradigm. An antisense oligonucleotide to caspase-2 inhibited cell death but did not affect caspase-3-like activity, indicating that caspase-2 is not upstream of this activity and that activation of caspase-3-like caspases is not sufficient for death. Thus, in our paradigm, caspase-2 processing and caspase-3-like activity are induced independently of each other. Moreover, although death requires caspase-2, caspase-3-like activity is neither necessary nor sufficient for death.
Insights
Caspase-2 processing is required for apoptosis induction in PC12 cells and neurons. Caspase-3-like activity is not necessary for caspase-2 processing or cell death, indicating independent pathways.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Caspase-2 (Nedd-2) is essential for apoptosis following trophic support withdrawal in PC12 cells and neurons.
- The precise role of caspase-2 processing in relation to other caspase activities during apoptosis remains unclear.
Purpose of the Study:
- To investigate the relationship between caspase-2 processing and the induction of caspase-3 (CPP32)-like activity in PC12 cells.
- To determine if caspase-3-like activity is required for caspase-2 processing or for cell death in this apoptotic model.
Main Methods:
- Analysis of caspase-2 processing and its correlation with caspase-3-like activity.
- Utilizing caspase inhibitors (BAF, zVAD-FMK, DEVD-FMK), bcl-2, flavopiridol, and antisense oligonucleotides to probe caspase pathways.
- Assessing cell death in PC12 cells and sympathetic neurons under various inhibitory conditions.
Main Results:
- Caspase-2 processing at D333 generated a 37 kDa N-terminal product, temporally correlating with caspase-3-like activity induction.
- Inhibitors of caspase-3-like activity (bcl-2, flavopiridol) acted upstream of caspase-2 processing.
- Selective caspase-3 inhibition (DEVD-FMK) blocked caspase-3-like activity but not caspase-2 processing or cell death, while caspase-2 inhibition blocked cell death but not caspase-3-like activity.
Conclusions:
- Caspase-2 processing and caspase-3-like activity are induced independently during apoptosis in this model.
- Caspase-2 is required for cell death, but caspase-3-like activity is neither necessary nor sufficient for apoptosis induction.
- These findings elucidate distinct roles for caspase-2 and caspase-3 in trophic deprivation-induced apoptosis.
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