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J. Exp. Med.,
Volume 187, Number 8, April 20, 1998 1261-1271
By




From the * Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, F-94801
Villejuif, France; the Early in programmed cell death (apoptosis), mitochondrial membrane permeability increases.
This is at least in part due to opening of the permeability transition (PT) pore, a multiprotein complex built up at the contact site between the inner and the outer mitochondrial membranes. The PT pore has been previously implicated in clinically relevant massive cell death induced by toxins, anoxia, reactive oxygen species, and calcium overload. Here we show that PT
pore complexes reconstituted in liposomes exhibit a functional behavior comparable with that
of the natural PT pore present in intact mitochondria. The PT pore complex is regulated by
thiol-reactive agents, calcium, cyclophilin D ligands (cyclosporin A and a nonimmunosuppressive cyclosporin A derivative), ligands of the adenine nucleotide translocator, apoptosis-related endoproteases (caspases), and Bcl-2-like proteins. Although calcium, prooxidants, and several
recombinant caspases (caspases 1, 2, 3, 4, and 6) enhance the permeability of PT pore-containing liposomes, recombinant Bcl-2 or Bcl-XL augment the resistance of the reconstituted PT
pore complex to pore opening. Mutated Bcl-2 proteins that have lost their cytoprotective potential also lose their PT modulatory capacity. In conclusion, the PT pore complex may constitute a crossroad of apoptosis regulation by caspases and members of the Bcl-2 family.
Faculty of Biology, University of Konstanz, D-78434 Konstanz, Germany;
the § Centre National de la Recherche Scientifique, Université de Paris 11, F-91405 Orsay, France;
and
The Burnham Institute, La Jolla, California 92037
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