Baculoviral IAP repeat-containing protein 2 (cIAP1) (BIRC2)

Baculoviral IAP repeat-containing protein 2 (BIRC2), more commonly known as Cellular inhibitor of apoptosis protein 1 (cIAP1), is a critical E3 ubiquitin ligase that regulates cell death and inflammatory signaling pathways [UniProt P98170]. It functions by ubiquitinating key signaling components like RIPK1 and NIK, thereby promoting cell survival through the activation of NF-kappaB and preventing the assembly of pro-apoptotic complexes [PubMed: 24048733]. In many human cancers, cIAP1 is overexpressed or its gene is amplified, providing a survival advantage to tumor cells and contributing to chemoresistance [PubMed: 21629213]. To exploit this, researchers developed Smac mimetics (IAP antagonists) which bind to cIAP1 and induce its rapid degradation, effectively priming tumor cells for apoptosis, particularly in the presence of TNF-alpha [DrugBank DB12004]. Several of these agents, such as Xevinapant, have demonstrated clinical potential in combination with chemotherapy or radiation, particularly in head and neck squamous cell carcinomas [NIH: NCT02022722]. However, the therapeutic use of IAP antagonists requires careful monitoring for side effects like cytokine release syndrome, which results from the systemic induction of pro-inflammatory cytokines.

Other names

Cellular inhibitor of apoptosis protein 1cIAP1HIAP-2MIHBRNF48API1Baculoviral IAP repeat-containing protein 3 (cIAP2)BIRC3cIAP2

IAP antagonists or Smac mimetics bind to the Baculoviral IAP Repeat (BIR) domains (specifically BIR2 and BIR3) of cIAP1 and cIAP2. This binding mimics the endogenous inhibitor Smac/DIABLO, triggering the auto-ubiquitination and rapid proteasomal degradation of the cIAP proteins [PubMed: 28246545]. The loss of cIAPs leads to the stabilization of NF-kappaB inducing kinase (NIK), activation of the non-canonical NF-kappaB pathway, and the sensitization of cells to Tumor Necrosis Factor (TNF)-mediated apoptosis [PubMed: 25421155].