Related Experiment Video
Updated: Sep 20, 2026
Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
Published on: March 5, 2018
Crystal structure of caspase-2, apical initiator of the intrinsic apoptotic pathway
Andreas Schweizer1, Christophe Briand, Markus G Grutter
1Department of Biochemistry, University of Zurich, 8057-Zurich, Switzerland.
Abstract:
The cell death protease caspase-2 has recently been recognized as the most apical caspase in the apoptotic cascade ignited during cell stress signaling. Cytotoxic stress, such as that caused by cancer therapies, leads to activation of caspase-2, which acts as a direct effector of the mitochondrion-dependent apoptotic pathway resulting in programmed cell death. Here we report the x-ray structure of caspase-2 in complex with the inhibitor acetyl-Leu-Asp-Glu-Ser-Asp-aldehyde at 1.65-A resolution. Compared with other caspases, significant structural differences prevail in the active site region and the dimer interface. The structure reveals the hydrophobic properties of the S5 specificity pocket, which is unique to caspase-2, and provides the details of the inhibitor-protein interactions in subsites S1-S4. These features form the basis of caspase-2 specificity and allow the design of caspase-2-directed ligands for medical and analytical use. Another unique feature of caspase-2 is a disulfide bridge at the dimer interface, which covalently links the two monomers. Consistent with this finding, caspase-2 exists as a (p19/p12)2 dimer in solution, even in the absence of substrates or inhibitors. The intersubunit disulfide bridge stabilizes the dimeric form of caspase-2, whereas all other long prodomain caspases exist as monomers in solution, and dimer formation is driven by ligand binding. Therefore, the central disulfide bridge appears to represent a novel way of dimer stabilization in caspases.
Insights
The caspase-2 protease structure reveals unique features, including a hydrophobic S5 pocket and a stabilizing disulfide bridge, enabling targeted drug design for apoptosis.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Caspase-2 is an apical caspase in the apoptotic cascade, activated by cytotoxic stress.
- It directly influences the mitochondrion-dependent apoptotic pathway, leading to programmed cell death.
- Understanding caspase-2 structure is crucial for developing targeted therapies.
Purpose of the Study:
- To determine the x-ray structure of caspase-2 in complex with an inhibitor.
- To elucidate the structural basis of caspase-2 specificity.
- To investigate the unique dimerization mechanism of caspase-2.
Main Methods:
- X-ray crystallography was used to obtain the structure of caspase-2 bound to acetyl-Leu-Asp-Glu-Ser-Asp-aldehyde at 1.65-A resolution.
- Comparative structural analysis with other caspases was performed.
- Biochemical assays were used to study caspase-2 dimerization in solution.
Main Results:
- The structure revealed significant differences in the active site and dimer interface compared to other caspases.
- A unique hydrophobic S5 specificity pocket was identified, contributing to caspase-2 specificity.
- A disulfide bridge at the dimer interface was observed, covalently linking monomers and stabilizing the dimer in solution.
Conclusions:
- The unique structural features of caspase-2, including the S5 pocket and disulfide bridge, dictate its specificity and dimerization.
- These findings provide a basis for designing specific caspase-2 inhibitors for therapeutic and analytical applications.
- The disulfide bridge represents a novel mechanism for dimer stabilization in caspases.
Related Concept Videos
01:24Caspases
01:31The Intrinsic Apoptotic Pathway
01:17The Extrinsic Apoptotic Pathway
01:30Apoptosis
01:22Cellular Injury V: Apoptosis and Autophagy
01:17Phagocytosis of Apoptotic Cells
Normal cells contain receptors that prevent them from being recognized by phagocytes.