Molecules that regulate NFKB activation play critical roles in apoptosis and inflammation. Recently this laboratory described the cloning of the cellular homolog of the equine herpesvirus2 (EHV2) protein E10 and showed that both proteins regulate mammalian apoptosis and NFKB activation. These proteins were found to contain N terminal caspase recruitment domains (CARDs) and novel C terminal domains (CTDs) and were therefore named CLAPs (CARD Like Apoptotic Proteins). The cellular and viral CLAPs induce apoptosis downstream of caspase 8 by activating the Apaf 1 caspase 9 pathway and activate NFKB by acting upstream of the NFKB inducing kinase, NIK, and the IKB kinase, IKKa. Deletion of either the CARD or the CTD domain inhibits both activities. We propose that these domains may facilitate interactions with death effector and NFKB regulatory molecules to engage both pathways. Consequently, we outlined experiments to study the mechanism by which the CLAP proteins engage the apoptotic or the NFKB pathway. In particular, we would like to determine whether CLAP engages caspase 9 directly or activates it through the Apaf 1 pathway via release of cytochrome c from the mitochondria. Experiments are also proposed to study the role of the CARD domain in the TNFR signaling complex, determine other components of the CLAP NFKB activation complex and determine the interactions that lead to activation of the IKK complex. Finally, it is also proposed to study the role of CLAP phosphorylation in apoptosis and NFKB activation and to identify the CLAP kinase. It is anticipated that these studies will contribute to elucidation of the mechanism of NFKB activation and apoptosis induction by CLAPs, and identification of other novel proteins involved in these two pathways. Since there is ample evidence for involvement of this protein in tumor formation and apoptosis, these studies could lay the foundation for new chemotherapeutic approaches for treatment of certain forms of cancer in which this protein is involved, and treatment of other diseases in which apoptosis is involved in the pathologic process.
