The intrinsic pathway is initiated within the cell in response to stress signals such as DNA damage, oxidative stress, or deprivation of survival factors. It is tightly regulated by the Bcl-2 family proteins, which includes both pro-apoptotic and anti-apoptotic members. Key events in this pathway involve the permeabilization of the mitochondrial outer membrane, leading to the release of cytochrome c into the cytosol. This release triggers the formation of the apoptosome, a complex that activates initiator caspase-9, which in turn activates effector caspases like caspase-3, leading to cell death.
