Fig. 4.

Apoptotic and non-apoptotic caspase signalisation. The extrinsic pathway is regulated by death receptors, leading to the activation of caspase-8 and -10. The intrinsic pathway is usually initiated in a cell-autonomous manner, resulting in expression of BH3-only proteins that inhibit anti-apoptotic proteins such as Bcl-2, permeabilization of the mitochondrial outer membrane, formation of apoptosome, and activation of caspase-9. Both pathways aim to activate caspase-3 (or other executors: caspase-6, -7). The extrinsic and intrinsic pathways are often interconnected (e.g. caspase − 8 (and also − 2) cleaves Bid into tBid, which impacts mitochondria). Caspase-12 contributes to Ca²⁺-dependent apoptosis. Caspase-2 activation occurs in response of both intrinsic and extrinsic stimuli