Fas signalling

 Fas is an important cell surface receptor protein that induces apoptosis upon binding to the Fas ligand (FasL). This ligand is predominantly expressed in Cytotoxic T-cells and T-Helper Cells.

FasL is a trimeric molecule whereas Fas is a monomer, as a consequence the binding of FasL results in the trimerisation of Fas, which the binds death domain-containing adaptor proteins. The adaptor protein recruits and activates Caspase 8, which in turn cleaves caspase 3. Activated Caspase 3 then cleaves I-CAD ( the inhibitor of CAD). The final product, CAD (a DNase), is then released into the nucleus of the cell in order to cleave DNA.