Dissipation of potassium and proton gradients inhibits mitochondrial hyperpolarization and cytochrome c release during neural apoptosis.
Monika Poppe
Claus Reimertz
Heiko Düssmann
Aaron J. Krohn
C Marc Luetjens
Doris Böckelmann
Anna-Liisa Nieminen
Donat Kögel
Jochen HM Prehn
10779/rcsi.10793003.v1
https://repository.rcsi.com/articles/journal_contribution/Dissipation_of_potassium_and_proton_gradients_inhibits_mitochondrial_hyperpolarization_and_cytochrome_c_release_during_neural_apoptosis_/10793003
<p>Exposure of rat hippocampal neurons or human D283 medulloblastoma cells to the apoptosis-inducing kinase inhibitor staurosporine induced rapid cytochrome c release from mitochondria and activation of the executioner caspase-3. Measurements of cellular tetramethylrhodamine ethyl ester fluorescence and subsequent simulation of fluorescence changes based on Nernst calculations of fluorescence in the extracellular, cytoplasmic, and mitochondrial compartments revealed that the release of cytochrome c was preceded by mitochondrial hyperpolarization. Overexpression of the anti-apoptotic protein Bcl-xL, but not pharmacological blockade of outward potassium currents, inhibited staurosporine-induced hyperpolarization and apoptosis. Dissipation of mitochondrial potassium and proton gradients by valinomycin or carbonyl cyanide p-trifluoromethoxy-phenylhydrazone also potently inhibited staurosporine-induced hyperpolarization, cytochrome c release, and caspase activation. This effect was not attributable to changes in cellular ATP levels. Prolonged exposure to valinomycin induced significant matrix swelling, and per se also caused release of cytochrome c from mitochondria. In contrast to staurosporine, however, valinomycin-induced cytochrome c release and cell death were not associated with caspase-3 activation and insensitive to Bcl-xL overexpression. Our data suggest two distinct mechanisms for mitochondrial cytochrome c release: (1) active cytochrome c release associated with early mitochondrial hyperpolarization, leading to neuronal apoptosis, and (2) passive cytochrome c release secondary to mitochondrial depolarization and matrix swelling.</p>
2019-11-22 17:04:15
Animals
Apoptosis
Caspase 3
Caspases
Cells
Cultured
Cytochrome c Group
Enzyme Inhibitors
Fluorescent Dyes
Hippocampus
Immunohistochemistry
Ionophores
Medulloblastoma
Mitochondria
Neurons
Potassium
Proto-Oncogene Proteins c-bcl-2
Protons
Rats
Inbred F344
Staurosporine
Transfection
Valinomycin
bcl-X Protein
Physiology
Medical Physics