FIG. 2.

Roles of mitochondria in apoptosis and necrosis. A critical event in cell death is mitochondrial membrane permeabilization, mediated by two permeability systems, the PTP and the mitochondrial outer MOMP (see text). PTP opening results in loss of the mitochondrial membrane potential (ΔΨm) and, ultimately, ATP depletion and necrosis. MOMP mediates the release into the cytosol of cytochrome c, triggering caspase activation cascade and subsequent apoptotic events. PTP, permeability transition pore; IMM, inner mitochondrial membrane; MOMP, membrane permeability system; OMM, outer mitochondrial membrane.