Description
Background: Apoptosis mediated by death factors like FasL and TNF-alpha involves the formation of a death-inducing signaling complex (DISC) to their respective receptors (1). Upon ligand activation to their receptors, Fas and TNF-R1 associate with death domain (DD) containing adaptor proteins FADD (Fas associated death domain) (2,3) and TRADD (TNF-R1 associated death domain) (4). In addition to its carboxy-terminal DD, FADD contains an amino-terminal death effector domain (DED) that binds to DEDs found on caspase-8 which leads to activation of this initiator caspase (5,6). Caspase-8 subsequently activates downstream effector caspases, like caspase-3, resulting in the cleavage of proteins involved in the execution of apoptosis. Unlike FADD, TRADD does not contain a DED (4). Apoptosis driven by TNF-R1 binding to TRADD involves association of TRADD and FADD which then leads to activation of caspase-8 (7)