Required for activation of NF-kappaB transcription factors in the immune deficiency (Imd) signaling cascade which is essential for innate immune responses upon infection by Gram-negative bacteria (PubMed:16894030, PubMed:17068333). Promotes cytoplasmic cleavage of Rel and its translocation to the nucleus where it drives expression of antimicrobial peptides (PubMed:17068333, PubMed:24374974). Binds, polyubiquitinates and activates Dredd which is required for Rel-mediated induction of antimicrobial peptides (PubMed:22549468). Anti-apoptotic protein which binds, ubiquitinates and inactivates the effector caspase Drice (PubMed:18166655). Suppresses rpr and hid-dependent cell death in the eye (PubMed:8548811). However, has also been shown to have little, if any, role in the regulation of the canonical caspase-dependent apoptosis pathway (PubMed:17068333). Plays a role in regulating the expression of ion channels (PubMed:24374974). Interacts with the caspase Strica (PubMed:11550090). Interacts (via BIR2 domain) with rpr and grim (PubMed:18166655). Interacts (via the BIR2 and BIR3 domains) with hid (PubMed:18166655). Interacts (via BIR3 domain) with Drice (PubMed:18166655). Interacts with Dredd; likely to bind Dredd simultaneously with Fadd to form a trimeric complex (PubMed:22549468). Expressed in both principal and stellar cells of the Malphigian tubules. Expressed in Malpighian tubules from the 3rd instar larval stage and expression continues in pupae and adults with highest levels in adults (at protein level). Constitutively expressed (PubMed:17068333). Up-regulated by bacterial lipopolysaccharides (LPS) in Malpighian tubules but not in salivary glands (PubMed:24374974). Caspase-dependent cleavage is required for suppression of Drice-mediated cell death. Normal development and viability (PubMed:16894030, PubMed:17068333). Acute sensitivity to infection by Gram-negative bacteria with failure to induce expression of antibacterial peptide genes and inability to mount a proper innate immune response (PubMed:16894030, PubMed:17068333, PubMed:24374974). Loss of cleavage and nuclear translocation of Rel (PubMed:17068333, PubMed:24374974). Increased activity of the effector caspase Drice and increased apoptosis following x-ray irradiation (PubMed:18166655). Reduced ion channel expression in Malpighian tubules (PubMed:24374974). Belongs to the IAP family.