With increasing eukaryotic evolution, the components of
the cell-intrinsic machinery have become organized around
mitochondria, which act as a hub for the apoptotic machinery.
Ultimately, almost all survival and death signaling pathways
in postmitotic neurons are funneled through the mitochondria
where they are integrated largely by the Bcl-2 proteins.
Mitochondrial intermediates including cytochrome c
regulate the downstream components of the cell death machinery
(Wang, 2001). Specificity is achieved through the
expression and activation of essential cell death proteins in
a stimulus-, time-, and cell-specific manner.