Zewnętrzny szlak apoptotyczny

The extrinsic apoptotic pathway is activated through extracellular death signals from immune cells.

These immune cells recognize dangerous cells, such as diseased ones, through homotrimeric ligands that bind to death receptors on the target cell membrane.

The death receptors belong to the tumor necrosis factor or TNF superfamily, which includes TNF receptor 1 and the Fas receptor.

In the Fas signaling pathway, the Fas ligand expressed on the surface of immune  cells binds to Fas receptor on the target cell, causing activation of the receptor death domain.

The activated death domain recruits an adaptor protein, Fas-associated death domain, which then binds to initiator procaspase-8 to form the death-inducing signaling complex or DISC.

Inside DISC, procaspase-8 molecules dimerize and self-cleave to form active caspase-8, which is released into the cytosol.

Caspase-8 activates executioner procaspase-3 to form caspase-3 that cleaves cellular proteins, resulting in apoptosis.