Cyclosporin A induces the opening of a potassium-selective channel in higher plant mitochondria.
The immunosuppressive drug, cyclosporin A (CsA), induces the generation of a transmembrane electrical potential difference (deltapsi) in deenergized plant mitochondria incubated in sucrose-based media. Build up of deltapsi is prevented by external monovalent cations in the order K+ > Rb+ = Li+ > Na+, or by the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone, which also collapses the deltapsi generated by CsA. Entry of K+ into mitochondria can be monitored as swelling by incubating the organelles in a medium containing KCl to maintain constant osmolarity. This swelling is inhibited by ATP and stimulated by CsA or valinomycin. In addition, in mitochondria energized by succinate, KCl causes a dissipation of deltapsi, with sigmoidal kinetics, which is favored by CsA. Therefore, plant mitochondria appear to possess a K+ selective, voltage-dependent channel, which is opened by CsA, regulated by the redox state, and inhibited by nucleotides. The hypothetical roles of this new K+ATP channel are discussed in relation to its potential involvement in mitochondrial volume regulation, thermogenesis, apoptosis, and/or prevention of reactive oxygen species formation in plants.
Petrussa
E
E
Department of Biology and Agro-industrial Economics, University of Udine, Italy.
Casolo
V
V
Braidot
E
E
Chiandussi
E
E
Macrì
F
F
Vianello
A
A
D016572:Cyclosporine / Q000494:pharmacology*; D004734:Energy Metabolism; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008933:Mitochondrial Swelling / Q000187:drug effects; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000378:metabolism / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism*
D015221:Potassium Channels; D016572:Cyclosporine; D011188:Potassium