Figure 2

Adaptor protein complexes, or apoptosomes, that are responsible for the activation of initiator caspases. The activation of caspase-2, caspase-8, and caspase-9 in mammalian cells are mediated by the PIDDosome (a),¹³ the DISC (b),¹⁴ and the apoptosome (c),^{15, 16, 17, 18, 19} respectively. PIDDosome contains at least three components, PIDD, RAIDD, and caspase-2.¹³ DISC is assembled following binding of death ligand to its receptor and contains FADD and caspase-8 (or –10). Apoptosome is composed of seven molecules of Apaf-1 bound to cytochrome c in the presence of ATP/dATP. Activation of Dronc in Drosophila and CED-3 in C. elegans is mediated by the octameric Dark-apoptosome (d) and CED-4 tetramer (e), respectively. Images of the various apoptosomes were adapted from previous publications^{55, 59, 65}