Apoptosis regulator protein which may function as a crucial link between cell survival and cell death pathways in mammalian cells. Acts as an inhibitor of TNFRSF6 mediated apoptosis. A proteolytic fragment (p43) is likely retained in the death-inducing signaling complex (DISC) thereby blocking further recruitment and processing of caspase-8 at the complex. Full length and shorter isoforms have been shown either to induce apoptosis or to reduce TNFRSF-triggered apoptosis. Lacks enzymatic (caspase) activity (By similarity). TNFRSF6 stimulation triggers recruitment to the death-inducing signaling complex (DISC) formed by TNFRSF6, FADD and CASP8 (By similarity). A proteolytic fragment (p43) stays associated with the DISC (By similarity). Interacts with RIPK1 (By similarity). The caspase domain lacks the active site residues involved in catalysis. Proteolytically processed by CASP8 generating subunit p43 and p12. Belongs to the peptidase C14A family.