Calcium-induced cytochrome c release from CNS mitochondria is associated with the permeability transition and rupture of the outer membrane.
The mechanisms of Ca2+-induced release of Cytochrome c (Cyt c) from rat brain mitochondria were examined quantitatively using a capture ELISA. In 75 or 125 mm KCl-based media 1.4 micromol Ca2+/mg protein caused depolarization and mitochondrial swelling. However, this resulted in partial Cyt c release only in 75 mm KCl. The release was inhibited by Ru360, an inhibitor of the Ca2+ uniporter, and by cyclosporin A plus ADP, a combination of mitochondrial permeability transition inhibitors. Transmission electron microscopy (TEM) revealed that Ca2+-induced swelling caused rupture of the outer membrane only in 75 mm KCl. Koenig's polyanion, an inhibitor of mitochondrial porin (VDAC), enhanced swelling and amplified Cyt c release. Dextran T70 that is known to enhance mitochondrial contact site formation did not prevent Cyt c release. Exposure of cultured cortical neurons to 500 microM glutamate for 5 min caused Cyt c release into the cytosol 30 min after glutamate removal. MK-801 or CsA inhibited this release. Thus, the release of Cyt c from CNS mitochondria induced by Ca2+ in vitro as well as in situ involved the mPT and appeared to require the rupture of the outer membrane.
Brustovetsky
Nickolay
N
Department of Neuroscience, University of Minnesota, Minneapolis 55455, USA.
Brustovetsky
Tatiana
T
Jemmerson
Ronald
R
Dubinsky
Janet M
JM
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001253:Astrocytes / Q000166:cytology; D002118:Calcium / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003574:Cytochrome c Group / Q000378:metabolism*; D018698:Glutamic Acid / Q000633:toxicity; D008928:Mitochondria / Q000378:metabolism*; D008933:Mitochondrial Swelling / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009498:Neurotoxins / Q000633:toxicity; D051381:Rats
D003574:Cytochrome c Group; D009498:Neurotoxins; D018698:Glutamic Acid; D002118:Calcium