Receptor-mediated caspase activation at the DISC.
Upon ligation by its cognate ligand, the trimeric death receptor recruits adaptor molecules via its cytoplasmic death domains (DD). Besides possessing DDs, the adaptors additionally contain death effector domains (DED) which recruit procaspase-8 to the receptor complex which now is called the death-inducing signalling complex (DISC). Procaspase-8 is activated by autoproteolytic cleavage and forms the active caspase-8 which is a heterotetramer of two small and two large subunits. The initiatior caspase-8 cleaves and thereby activates effector caspases for the execution of apoptosis.