TRAIL (TNF-Related Apoptosis-Inducing Ligand) is a protein consisting of 281 amino acids. It is also called Apo2L. Five proteins, TRAILR1 (DR4), TRAILR2 (DR5/ TRICK2 or KILLER), TRAILR3 (DcR1/ TRID or LIT), TRAILR4 (DcR2 or TRUNDD), and Opg (Osteoprotegerin), have been identified as TRAIL receptors (Ref.1). Both TRAILR1 and TRAILR2 contain the functional DD (Death Domain), capable of inducing apoptosis. The other three receptors DcR1, DcR2 and Opg serve as "decoy" receptors. These three receptors can bind to TRAIL, but cannot induce apoptosis. DcR1 is a glycosylphosphatidylinositol-anchored cell surface protein, which contains the TRAIL-binding region as well as a region that anchors the receptor to the membrane. But unlike the other receptors, DcR1 lacks an intracellular tail needed to spark the [...]