The (mitochondrial, mt) permeability transition pore (PTP) is an unspecific pore presumed to involve components of both the inner and outer mt membrane which upon opening induces a massive increase of the inner mt membrane permeability for solutes up to 1.5 kDa. It is crucially involved in cell death induction in response to, among other stimuli, radical stress and/or calcium overload and may cause necrosis or apoptosis. It plays an important role in neurodegenerative diseases, cardiac ischemia-reperfusion injury and possibly various other diseases. Previously considered essential molecular constituents such as the voltage-dependent anion channel (VDAC), the adenine nucleotide translocator (ANT) and cyclophilin D (CypD) have all been shown to be important regulators of mtPTP opening, but the molecular entities actually forming the pore are still unknown at present. The opening of the pore can be prevented using cyclosporin A, a compound that binds cyclophilin D avoiding the formation of the pore. In respirometry, mtPTP opening may be observed as a sudden decrease of respiration of isolated mitochondria (Hansson 2010 J Biol Chem).
Regulation: Calcium, mt-Membrane potential