Figure 1

The permeability transition pore (PTP) function. During apoptosis, many signals can converge on the mitochondrion to regulate the mitochondrial membrane permeability. In response to calcium (Ca²⁺), atractyloside, adenine nucleotide depletion, chemotherapeutics and pro-oxidant agents, the membrane permeabilization can result from the opening of PTP as a large unspecific channel and leads to the release of proapoptotic factors into the cytosol. In contrast, many agents (CsA, bongkrekic acid, Mg²⁺, high ADP/ATP) or conditions (pH<7) promote the closure of the PTP and prevent apoptosis. When available, PDB structure models for PTP members have been inserted.