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FEBS Lett. 2002 Feb 13;512(1-3):1-7.

Regulated and unregulated mitochondrial permeability transition pores: a new paradigm of pore structure and function?

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Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, CB#7090, 236 Taylor Hall, Chapel Hill, NC 27599-7090, USA.


Cyclosporin A (CsA) inhibits the mitochondrial permeability transition (MPT), but not always. To characterize the CsA-sensitive and -insensitive MPT, rat liver mitochondria were exposed to low and high doses of various MPT inducers. Mitochondrial swelling, cyclophilin D membrane binding and permeability transition (PT) pore diameter were measured. The results indicate two conductance modes for the PT pore: one activated by Ca(2+) and inhibited by CsA and Mg(2+) and the other unregulated. We propose a new model of pore formation and gating in which PT pores form by aggregation of misfolded integral membrane proteins damaged by oxidant and other stresses. Chaperone-like proteins initially block conductance through these misfolded protein clusters; however, increased Ca(2+) opens these regulated PT pores, an effect blocked by CsA. When protein clusters exceed chaperones available to block conductance, unregulated pore opening occurs.

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