Related Experiment Videos
The proteolytic procaspase activation network: an in vitro analysis
M Van de Craen1, W Declercq, I Van den brande
1Department of Molecular Biology, University of Gent and Flanders Interuniversity Institute for Biotechnology, Gent, Belgium.
Abstract:
In general, apoptotic stimuli lead to activation of caspases. Once activated, a caspase can induce intracellular signaling pathways involving proteolytic activation of other caspase family members. We report the in vitro processing of eight murine procaspases by their enzymatically active counterparts. Caspase-8 processed all procaspases examined. Caspase-1 and -11 processed the effector caspases procaspase-3 and -7, and to a lesser extent procaspase-6. However, vice versa, none of the caspase-1-like procaspases was activated by the effector caspases. This suggests that the caspase-1 subfamily members either act upstream of the apoptosis effector caspases or else are part of a totally separate activation pathway. Procaspase-2 was maturated by caspase-8 and -3, and to a lesser extent by caspase-7, while the active caspase-2 did not process any of the procaspases examined, except its own precursor. Hence, caspase-2 might not be able to initiate a wide proteolytic signaling cascade. Additionally, cleavage data reveal not only proteolytic amplification between caspase-3 and -8, caspase-6 and -3, and caspase-6 and -7, but also positive feedback loops involving multiple activated caspases. Our results suggest the existence of a hierarchic proteolytic procaspase activation network, which would lead to a dramatic increase in multiple caspase activities once key caspases are activated. The proteolytic procaspase activation network might allow that different apoptotic stimuli result in specific cleavage of substrates responsible for typical processes at the cell membrane, the cytosol, the organelles, and the nucleus, which characterize a cell dying by apoptosis.
Insights
This study reveals a hierarchical network for caspase activation during apoptosis. Caspase-8 broadly activates other caspases, forming a cascade that amplizes cell death signaling.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Apoptotic stimuli trigger caspase activation, initiating intracellular signaling pathways.
- Activated caspases proteolytically activate other caspase family members, amplifying the apoptotic response.
Purpose of the Study:
- To investigate the in vitro processing of eight murine procaspases by their active counterparts.
- To elucidate the hierarchical activation network and proteolytic amplification among caspases.
Main Methods:
- In vitro processing assays using active caspases and their procaspase precursors.
- Analysis of cleavage patterns to determine substrate specificity and activation pathways.
Main Results:
- Caspase-8 demonstrated broad processing activity against all examined procaspases.
- Caspase-1 and -11 specifically activated effector caspases (procaspase-3, -7), suggesting an upstream role or separate pathway.
- Cleavage data revealed proteolytic amplification and positive feedback loops involving multiple caspases, including caspase-2, -3, -6, -7, -8, and -11.
Conclusions:
- A hierarchical proteolytic procaspase activation network exists, leading to amplified caspase activity upon apoptotic stimuli.
- This network allows specific cleavage of substrates, mediating characteristic apoptotic processes across cellular compartments.
- Caspase-2 appears limited in initiating broad proteolytic cascades, unlike other caspases studied.