An Optimized Activity-Based Probe for the Study of Caspase-6 Activation

Cancer Biology Program, Stanford School of Medicine, 300 Pasteur Drive, Stanford, CA 94305-5324, USA.
Chemistry & biology (Impact Factor: 6.65). 03/2012; 19(3):340-52. DOI: 10.1016/j.chembiol.2011.12.021
Source: PubMed


Although significant efforts have been made to understand the mechanisms of caspase activation during apoptosis, many questions remain regarding how and when executioner caspases get activated. We describe the design and synthesis of an activity-based probe that labels caspase-3/-6/-7, allowing direct monitoring of all executioner caspases simultaneously. This probe has enhanced in vivo properties and reduced cross-reactivity compared to our previously reported probe, AB50. Using this probe, we find that caspase-6 undergoes a conformational change and can bind substrates even in the absence of cleavage of the proenzyme. We also demonstrate that caspase-6 activation does not require active caspase-3/-7, suggesting that it may autoactivate or be cleaved by other proteases. Together, our results suggest that caspase-6 activation proceeds through a unique mechanism that may be important for its diverse biological functions.

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Available from: Laura E Edgington-Mitchell
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    • "Once dimerized, the caspase is able to cleave target substrates (Boatright et al. 2003). Executioner caspases (e.g., caspase-3, -6, -7) exist as inactive dimers that are activated upon proteolytic cleavage of both monomers at loops containing specific cleavage sites (Berger et al. 2006a; Denault et al. 2006; Edgington et al. 2012). Cleavage of these loops results in structural changes that serve to form the active sites, allowing the executioner caspases to cleave downstream substrates (Chai et al. 2001; Riedl et al. 2001). "
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    • "Effector caspases are activated by initiator caspases (e.g., caspase-2, 8, and 9), and then induce apoptotic cell death. Although the initiator and effector caspase cascade is well known, interactions among effector caspases are disputed [26]. "
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