TRAIL (also known as Apo-2L) is a member of the tumor necrosis factor (TNF) ligand family that rapidly induces apoptosis in a variety of transformed cell lines. A distinct receptor for TRAIL, TRAIL-R2 (aka Death Receptor 5 (DR5)), by ligand-based affinity purification and subsequent molecular cloning. TRAIL-R2 is widely expressed and the gene encoding TRAIL-R2 is located on human chromosome 8p22-21. TRAIL-R2 engages a caspase-dependent apoptotic pathway but, in contrast to TRAIL-R1, TRAIL-R2 mediates apoptosis via the intracellular adaptor molecule FADD/MORT1.