Epigenetics and Signaling Pathways in Glaucoma

Figure 2

Extrinsic and intrinsic pathways of apoptosis. In the extrinsic pathway, Fas ligand or TGF- binds to its receptor, which is bound by FADD. This activates Caspase 8, which activates the effector Caspases 3, 6, and 7. These caspases all lead to apoptosis. Caspase 8 also activates Bid, a protein that turns on BAX and Bak. The intrinsic pathway also triggers these same proteins by working through BH3-only proteins. BAX and Bak increase the permeability of the mitochondrial membrane, releasing Cytochrome C. This protein activates Caspase 9, which activates the same effector caspases, causing apoptosis. Bcl-2 inhibits this pathway by blocking the activation of BAX and Bak, while IAPs inhibit Caspases 3, 6, 7, and 9.