Permeability transition pore complex

Kroemer G. The mitochondrial permeability transition pore complex as a pharmacological target. An introduction. Curr Med Chem 2003 10(16) 1469-1472. 

Halestrap, A.P., McStay, G. P., and Clarke, S. J., 2002, The permeability transition pore complex another view, Biochimie 84, pp. 153-166... 

Marzo I, Brenner C, Zamzami N, Susin SA, Beutner G, Brdiczka D, Remy R, Xie ZH, Reed JC, Kroemer G (1998), The permeability transition pore complex a target for apoptosis regulation by caspases and bcl-2-related proteins, J. Exp. Med 187 1261-1271. 

A key event in preventing apoptosis is thus the retention of cytochrome c within mitochondria. The permeability transition pore complex is formed between the inner and outer mitochondrial membranes and is reported to control protein release from the intermembrane space. The permeabihty transition pore complex comprises the adenine nucleotide transporter, the voltage-dependent anion channel and possibly other proteins such as the benzodiazepine receptor and cyclophilin D [65]. Thus, cells possess specialised systems and processes for retaining cytochrome c within mitochondria to ensure survival, as well as systems that can rapidly mobilise this molecule when the apoptotic pathway is triggered. 

Fig. 1. Modulation of apoptosis by v-FLIP and v-Bcl-2. v-FLIPs specifically inhibit apoptosis mediated by death receptors. v-lCA specifically targets caspase-8 and inhibits its activation. v-Bcl-2 and vMIA inhibit those apoptotic pathways that are signaled through mitochondrial release of cytochrome c. FADD, Fas-associated death domain FLICE, FADD-like interleukin-converting enzyme CARD, cas-pase-recruiting domain PTPC. permeability transition pore complex FLIP, FLICE-inhibitory protein vie A, viral inhibitor of caspase 8-induced-apoptosis MIA. viral mitochondrial inhibitor of apoptosis Apcif-l, apoptotic protease-activating factor 1...

By definition, the uncoupling effect of certain flavonoids should be independent of their inhibitory effects on mitochondrial respiration or FoFi-ATPase, suggesting an additional mode of action of flavonoids against mitochondrial function. A collapse of the transmembrane potential is likely under conditions in which the permeability barrier created by the mitochondrial inner membrane is compromised (as occurs in the presence of ionophores). Calcium, phosphate, oxidative stress, adenine nucleotide depletion, and membrane depolarization can induce such a nonspecific increase in the permeability of the inner membrane, in an event called the mitochondrial permeability transition (MPT) [30,34]. The MPT can be selectively inhibited by cyclosporin A and is believed to involve the assembly of a multiprotein complex to form a nonspecific pore that spans the inner and outer mitochondrial membranes. The latter assembly is referred to as the permeability transition pore complex (PTPC) (Fig. 1). Its exact composition is unknown, but appears to comprise cyclophilin D, ANT, the voltage-dependent anion channel (porin), and a benzodiazepinebinding site [10,30,34]. 

Chromatin condensation membrane blebbing release of cytochrome c through the permeability transition pore complex activation of caspases Disruption of cytoplasmic membrane and other organelles (e.g., lysosomes, Golgi apparatus) drastic alteration of transmembrane transport processes inhibition of protein synthesis... 

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