The enigma of Caspase 12!!

Lorraine Cuffe

The only substrate of caspase 12 which have been established so far is itself.  The aim of this study is to discover novel substrates of Caspase 12.  Caspase 12 is a member of the ICE subfamily of caspases.  Other members include Caspase 1, 4, 5 and 11.  Although human caspase 12 is truncated, mouse caspase 12 shares significant sequence homology with human caspase 4. This family has predominantly been associated with the inflammatory response.  However, Caspase 12 has, in addition, been found localized to ER membrane and implicated in ER stress induced apoptosis. This could signify an alternative pathway towards cell death in response to ER stress following prolonged UPR (unfolded protein response) activation. Furthurmore, similarly to many inflammatory proteins, caspase 12 contains a card domain in its pro-domain suggesting the potential for interactions between it and other card containing proteins.

In order to uncover low abundance substrates of caspase 12, a human cDNA library is being screened and subjected to in vitro transcription and translation (TNT) to generate pools of potential substrates in rabbit reticulocytes lysates.  Active caspase 12, generated by expressing truncated (missing the pro-domain) His-tagged caspase-12 is being used to cleave potential substrates in the radiolabelled TNT libraries.  Positive pools will be decoded and sequenced.  Substrates will be verified using caspase 12 knockout cells or by using siRNA technology.

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