Proc Natl Acad Sci U S A. 2008 Mar 18;105(11):4133-8. Epub 2008 Mar 10.

Confinement of caspase-12 proteolytic activity to autoprocessing.External

Roy, S., Sharom, J. R., Houde, C., Loisel, T. P., Vaillancourt, J. P., Shao, W., Saleh, M., Nicholson, D. W.,
--- - Department of Cardiovascular Diseases, Apoptosis Research Group, Merck Research Laboratories, 126 East Lincoln Avenue, Rahway, NJ 07065-0900, USA.
Caspase-12 is a dominant-negative regulator of caspase-1 (IL-1beta-converting enzyme) and an attenuator of cytokine responsiveness to septic infections. This molecular role for caspase-12 appears to be akin to the role of cFLIP in regulating caspase-8 in the extrinsic cell death pathway; however, unlike cFLIP/Usurpin, we demonstrate here that caspase-12 is catalytically competent. To examine these catalytic properties, rat caspase-12 was cloned, and the recombinant enzyme was used to examine the cleavage of macromolecular and synthetic fluorogenic substrates. Although caspase-12 could mediate autoproteolytic maturation of its own proenzyme, in both cis and trans, it was not able to cleave any other polypeptide substrate, including other caspase proenzymes, apoptotic substrates, cytokine precursors, or proteins in the endoplasmic reticulum that normally undergo caspase-mediated proteolysis. The dearth of potential substrates for caspase-12 also was confirmed by whole-cell diagonal-gel analysis. Autolytic cleavage within the caspase-12 proenzyme was mapped to a single site at the large-small subunit junction, ATAD(319), and this motif was recognized by caspase-12 when incorporated into synthetic fluorogenic substrates. The specific activity of caspase-12 with these substates was several orders of magnitude lower than caspases-1 and -3, highlighting its relative catalytic paucity. In intact cells, caspase-12 autoproteolysis occurred in the inhibitory complex containing caspase-1. We propose that the proteolytic activity of caspase-12 is confined to its own proenzyme and that autocleavage within the caspase-1 complex may be a means for temporal limitation of the inhibitory effects of caspase-12 on proinflammatory cytokine maturation.
PMID: 18332441External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
CARD Caspase1 Link Caspase12 Co-immunoprecipitation HEK293 Not specified Not specified Rat Full length 18332441
(Link: click this icon to show interactions only between the two corresponding DDs)
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
Functional Role
Family DD1 DD2 Method Death-related Death-unrelated Reference
CARD Caspase1 Link Caspase12 Caspase cleaved assay Caspase12 activation 18332441
(Link: click this icon to show interactions only between the two corresponding DDs)