Unpublished draft

FAS (CD95)

FAS (CD95) is a death receptor: a cell-surface member of the tumor necrosis factor receptor family whose engagement by its ligand launches the extrinsic apoptosis pathway.

Function

FAS spans the membrane once and carries an intracellular death domain. When FAS ligand (FASL) on a cytotoxic T cell clusters three or more FAS molecules on a target cell, the clustered death domains recruit FADD and procaspase-8 into the death-inducing signaling complex (DISC). Procaspase-8 dimerizes and activates, then cleaves downstream executioner caspases (caspase-3); in type I cells this suffices to kill, and in type II cells the signal must be amplified through the