Effects of physiological and synthetic IAP antagonism on c-IAP-dependent signaling.

Cellular inhibitor of apoptosis proteins 1 and 2 (c-IAP1/2) have central roles in signal transduction mediated by numerous receptors that participate in inflammatory and immune responses. In certain pathways, such as activation of NF-κB, their degradation is a major regulatory event and is physiologically induced by activation of receptors. In addition, a number of synthetic compounds have been developed that also target the c-IAPs and induce their degradation. However, the extent of a synthetic IAP antagonist's ability to mirror the transcriptional program by a physiological signal remains unclear. Here we take a systems approach to compare the transcriptional programs triggered by activation of CD30, a well-characterized receptor previously shown to induce the degradation of the c-IAPs, to SM-164, a synthetic IAP antagonist that specifically triggers c-IAP degradation. Employing a technique that allows the specific analysis of newly transcribed RNA, we have generated comparative transcriptome profiles for CD30 activation and SM-164 treatment. Analysis of these profiles revealed that the genes regulated by each stimulus were not completely shared, indicating novel functions of IAP antagonists and consequences of c-IAP1/2 degradation. The data identified a role for c-IAP1/2 in the regulation of the ribosome and protein synthesis, which was subsequently confirmed by biological assays. These findings expand our knowledge of the roles of c-IAP1/2 in signaling and provide insight into the mechanism of synthetic IAP antagonists, furthering our understanding of their therapeutic potential.