Cellular inhibitor of apoptosis protein 1 (cIAP1) BIR3 domain (cIAP1 BIR3)

Cellular inhibitor of apoptosis protein 1 (cIAP1) is a key regulator of programmed cell death and innate immune signaling, frequently overexpressed in various malignancies to promote tumor cell survival. The BIR3 (Baculovirus IAP Repeat 3) domain is a critical structural component of cIAP1 that mediates protein-protein interactions, specifically binding to the pro-apoptotic protein Smac/DIABLO and caspases. By sequestering these pro-apoptotic factors, the BIR3 domain prevents the initiation of the apoptotic cascade. In oncology, the BIR3 domain is a primary target for a class of drugs known as Smac mimetics, which displace natural ligands and induce the autoubiquitination and subsequent degradation of cIAP1. This degradation shifts the cellular response to TNF-alpha from a survival-oriented NF-kappaB signal to a pro-apoptotic signal, effectively sensitizing cancer cells to apoptosis-inducing therapies. Consequently, the cIAP1 BIR3 domain serves as a strategic focal point for drug development aimed at overcoming apoptosis resistance in cancer.

Other names

Baculoviral IAP repeat-containing protein 2 BIR3 domainBIRC2 BIR3 domainInhibitor of apoptosis protein 2 BIR3 domainHIAP2 BIR3 domainMIHB BIR3 domainRNF48 BIR3 domain

Smac mimetics bind to the BIR3 domain of cIAP1, mimicking the N-terminal IAP-binding motif (IBM) of the endogenous pro-apoptotic protein Smac/DIABLO. This binding induces a conformational change that triggers the E3 ligase activity of cIAP1, leading to its rapid autoubiquitination and proteasomal degradation. The loss of cIAP1 prevents the ubiquitination of RIPK1, facilitating the formation of pro-apoptotic complexes and sensitizing cells to TNF-alpha-mediated cell death.