NMDA-evoked consumption and recovery of mitochondrially targeted aequorin suggests increased Ca2+ uptake by a subset of mitochondria in hippocampal neurons.
Activation of NMDA receptors produces large increases in cytosolic Ca(2+) that are taken up into mitochondria. We used recombinant aequorin targeted to mitochondria to report changes in matrix Ca(2+) in rat hippocampal neurons in culture. Upon binding Ca(2+), aequorin emits a photon in a one-shot reaction that consumes the indicator. Here we show that stimulation with NMDA produced a mitochondrial Ca(2+) response that rapidly inactivated. However, following a 30-min recovery period the response was restored, suggesting the presence of a pool of indicator that was not exposed to high Ca(2+) during the initial stimulus. We speculate that aequorin distant from the Ca(2+) source was protected from microdomains of high Ca(2+) near the plasmalemma and that this aequorin moved, either by movement of individual mitochondria or via the mitochondrial tubular network, to replenish consumed indicator during the recovery time. A large Ca(2+) increase in a subset of mitochondria could produce local changes in energy metabolism, regional Ca(2+) buffering, and foci that initiate neurotoxic processes.
Baron
Kyle T
KT
Department of Pharmacology, University of Minnesota Medical School, 6-120 Jackson Hall, 321 Church St. SE, Minneapolis, MN 55455-0217, USA.
Wang
Guang Jian
GJ
Padua
Rodolfo A
RA
Campbell
Colin
C
Thayer
Stanley A
SA
D000331:Aequorin / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004622:Embryo, Mammalian; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D007211:Indoles / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D008163:Luminescent Measurements; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010875:Pipecolic Acids / Q000494:pharmacology; D051381:Rats
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D007476:Ionophores; D010875:Pipecolic Acids; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; C053672:selfotel; D000331:Aequorin; D016202:N-Methylaspartate; C048960:indo-1; D002118:Calcium