Molecular determinants involved in activation of caspase 7. Issue 4 (2nd March 2011)

• Record Type: Journal Article
• Authors: Boucher, Dave; Blais, Véronique; Drag, Marcin; Denault, Jean-Bernard
• Is Part Of: Bioscience reports. Volume 31:Issue 4(2011)
• Page Start: 283
• Page End: 294
• Publication Date: 2011-03-02
• Subjects: activation mechanism -- apoptosis -- caspase 7 -- interdomain connector -- protease; Molecular biology -- Periodicals; Cytology -- Periodicals; 572.8
• DOI: 10.1042/BSR20100111
• Languages: English
• ISSNs: 0144-8463

Abstract

Abstract : During apoptosis, initiator caspases (8, 9 and 10) activate downstream executioner caspases (3, 6 and 7) by cleaving the IDC (interdomain connector) at two sites. Here, we demonstrate that both activation sites, site 1 and site 2, of caspase 7 are suboptimal for activation by initiator caspases 8 and 9 in cellulo, and in vitro using recombinant proteins and activation kinetics. Indeed, when both sites are replaced with the preferred motifs recognized by either caspase 8 or 9, we found an up to 36-fold improvement in activation. Moreover, cleavage at site 1 is preferred to site 2 because of its location within the IDC, since swapping sites does not lead to a more efficient activation. We also demonstrate the important role of Ile 195 of site 1 involved in maintaining a network of contacts that preserves the proper conformation of the active enzyme. Finally, we show that the length of the IDC plays a crucial role in maintaining the necessity of proteolysis for activation. In fact, although we were unable to generate a caspase 7 that does not require proteolysis for activity, shortening the IDC of the initiator caspase 8 by four residues was sufficient to confer a requirement for proteolysis, a key feature of executioner caspases. Altogether, the results demonstrate the critical role of the primary structure of caspase 7's IDC for its activation and proteolytic activity.