is a type of cell-death. In contrast to
is a process initiated by the cell itself.
takes place as part of cell-internal processes and hence does not harm surrounding cells. It is a two-phase process, divided into the initiation- and the effector phase. The initiation phase can further be divided into the extrinsic pathway (type 1 apoptosis) and the intrinsic pathway (type 2 apoptosis). The extrinsic pathway takes place via the trimerisation of a receptor of the
), denominated the death receptor. Subsequently, the trimers bind adaptor-molecules that are bound via a domain that is called the death-domain. By recruitment of the proteins
the caspase cascade is triggered via
, ultimately leading to a feedback that causes activation of further
The intrinsic pathway apparently occurs due to release of from the mitochondria into the cytoplasm. Severe DNA damage, for instance, can trigger this pathway via the tumor suppressor . The protein stimulates expression of pro-apoptotic factors like the protein family.
The effector phase eventually leads to cell death. One of the molecular effects leading to cell death is that and are degraded.