The potassium level in mitochondria is regulated by a K1ATP channel, recently identi®ed, whose opening can be induced by cyclosporin A. In addition, plant mitochondria have an electroneutral H1/K1 exchanger and a putative chloride channel which, acting in concert with the K1ATP channel, can accomplish a K1 cycling. In this work, we present evidence on the modulation of the K1ATP channel of pea stem mitochondria by NO and H2O2, and on its possible involvement in cytochrome c release. Pea stem mitochondria, resuspended in a KCl medium (de-energized mitochondria), underwent a swelling, as a consequence of K1 entry, that was inhibited by ATP. This inhibition was partially restored by GTP and diazoxide (K1 channel openers). In addition, glyburide and 5- hydroxydecanoate (K1ATP channel blockers) induced an inhibition of the GTP-stimulated swelling. Mitochondrial swelling was inhibited by H2O2 (generated by glucose±glucose oxidase), but stimulated by NO (released by potassium nitroprusside). The same results were also obtained in succinate-energized mitochondria. When the succinate-dependent electrical potential had reached a steady-state, the addition of KCl induced a dissipation that was favoured by NO and prevented by the NO scavenger, carboxy-PTIO. Hydrogen peroxide prevented the stimulation by NO of the KCl-induced dissipation of the electrical potential. The aperture of this channel was linked to the partial rupture of the outer membrane, and the latter effect led to a release of cytochrome c, but not of adenylate kinase. These results show that the plant mitochondrial K1 channel resembles that present in mammalian mitochondria. This channel can be modulated by NO and H2O2 and is involved in the release of cytochrome c, occurring during the manifestation of programmed cell death. This conclusion is reinforced by the consideration that there is no clear evidence for the presence of a permeability transition pore in plant mitochondria which can perform this function.

Modulation of K+ATP channel and cytochrome c release in plant mitochondria

CHIANDUSSI, Elisa;PETRUSSA, Elisa;CASOLO, Valentino;MACRI', Francesco Arturo;VIANELLO, Angelo
2001-01-01

Abstract

The potassium level in mitochondria is regulated by a K1ATP channel, recently identi®ed, whose opening can be induced by cyclosporin A. In addition, plant mitochondria have an electroneutral H1/K1 exchanger and a putative chloride channel which, acting in concert with the K1ATP channel, can accomplish a K1 cycling. In this work, we present evidence on the modulation of the K1ATP channel of pea stem mitochondria by NO and H2O2, and on its possible involvement in cytochrome c release. Pea stem mitochondria, resuspended in a KCl medium (de-energized mitochondria), underwent a swelling, as a consequence of K1 entry, that was inhibited by ATP. This inhibition was partially restored by GTP and diazoxide (K1 channel openers). In addition, glyburide and 5- hydroxydecanoate (K1ATP channel blockers) induced an inhibition of the GTP-stimulated swelling. Mitochondrial swelling was inhibited by H2O2 (generated by glucose±glucose oxidase), but stimulated by NO (released by potassium nitroprusside). The same results were also obtained in succinate-energized mitochondria. When the succinate-dependent electrical potential had reached a steady-state, the addition of KCl induced a dissipation that was favoured by NO and prevented by the NO scavenger, carboxy-PTIO. Hydrogen peroxide prevented the stimulation by NO of the KCl-induced dissipation of the electrical potential. The aperture of this channel was linked to the partial rupture of the outer membrane, and the latter effect led to a release of cytochrome c, but not of adenylate kinase. These results show that the plant mitochondrial K1 channel resembles that present in mammalian mitochondria. This channel can be modulated by NO and H2O2 and is involved in the release of cytochrome c, occurring during the manifestation of programmed cell death. This conclusion is reinforced by the consideration that there is no clear evidence for the presence of a permeability transition pore in plant mitochondria which can perform this function.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11390/900141
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