Extrinsic and intrinsic pathways to caspase-3 activation. Overview of pathways to caspase-3 activation. Each separate gray region represent the three modules: DISC (death-inducing signaling complex), MAC (mitochondrial apoptosis-induced channel) and apoptosome. Species and their symbols are: FasL (FasL), FasR (FasR), DISC (DISC), procaspase-8 and caspase-8 (Casp8), bifunctional apoptosis inhibitor (BAR), procaspase-3 and caspase-3 (Casp3), XIAP (XIAP), Bid and truncated Bid (Bid), Bax (Bax), tBid - Bax2 complex (tBid - Bax2), Smac (Smac), Apaf-1 (Apaf), cytochrome c (Cytc), apoptosome (Apop), procaspase-9 and caspase-9 (Casp9). Arrows denote chemical conversions or catalyzed reactions while hammerheads represent inhibition.