IAPs: what's in a name?

Abstract

Originally described in insect viruses, cellular proteins with Baculoviral IAP repeat (BIR) motifs have been thought to function primarily as inhibitors of apoptosis. The subsequent finding that a subset of IAPs that contain a RING domain have ubiquitin protein ligase (E3) activity implied the presence of other functions. It is now known that IAPs are involved in mitotic chromosome segregation, cellular morphogenesis, copper homeostasis, and intracellular signaling. Here, we review the current understanding of the roles of IAPs in apoptotic and nonapoptotic processes and explore the notion that the latter represents the primary physiologic activities of IAPs.

Fig. 1. Schematic representation of the human and Drosophila IAP family of proteins

The number of residues in each IAP is shown, as well as the functional motifs that they contain. The BIRC nomenclature equivalents are provided. ILP2, ML-IAP, and Deterin are shown in this figure but not discussed in the review because little information about their function is available. NCBI GenBank (http://www.ncbi.nlm.nih.gov/Genbank) accession numbers are survivin: O15392; ILP2 : Q96P09; ML-IAP : Q96CA5; XIAP : P98710; c-IAP1 : Q13490; c-IAP2 : Q13489; NAIP : Q13075; Bruce : Q9NR09; Deterin : NM_142351; DIAP1 : Q24306; DIAP2 : Q24307: DBruce : NP_649995. CARD, caspase-associated recruitment domain; UBC, ubiquitin-conjugation; NOD, nucleotide-binding oligomerization domain; LRR, leucine-rich repeats.