Multi-functional protein which regulates not only caspases and apoptosis, but also modulates inflammatory signaling and immunity, mitogenic kinase signaling and cell proliferation, as well as cell invasion and metastasis. Acts as an E3 ubiquitin- protein ligase regulating NF-kappa-B signaling and regulates both canonical and non-canonical NF-kappa-B signaling by acting in opposite directions: acts as a positive regulator of the canonical pathway and suppresses constitutive activation of non-canonical NF-kappa-B signaling. The target proteins for its E3 ubiquitin- protein ligase activity include: RIPK1, RIPK2, RIPK3, RIPK4, CASP3, CASP7, CASP8, TRAF1, and BCL10. Acts as an important regulator of innate immune signaling via regulation of Toll-like receptors (TLRs), Nodlike receptors (NLRs) and RIG-I like receptors (RLRs), collectively referred to as pattern recognition receptors (PRRs). Protects cells from spontaneous formation of the ripoptosome, a large multi-protein complex that has the capability to kill cancer cells in a caspase-dependent and caspase- independent manner. Suppresses ripoptosome formation by ubiquitinating RIPK1 and CASP8. Interacts with DIABLO/SMAC and with PRSS25; these interactions inhibit apoptotic suppressor activity. The BIR motifs region interacts with TNF receptor associated factors 1 and 2 (TRAF1 and TRAF2) to form an heteromeric complex, which is then recruited to the tumor necrosis factor receptor 2 (TNFR2). Interacts with RIP1, RIP2, RIP3, RIP4 and USP19. Highly expressed in fetal lung, and kidney. In the adult, expression is mainly seen in lymphoid tissues, including spleen, thymus and peripheral blood lymphocytes. USP19 regulates the stability of BIRC3/c-IAP2 by preventing its ubiquitination. Belongs to the IAP family. Note: This description may include information from UniProtKB.