Identification of an N-methyl-D-aspartate receptor in isolated nervous system mitochondria.
NMDA ionotropic glutamate receptors gate the cytoplasmic influx of calcium, which may, depending on the intensity of the stimulus, subserve either normal synaptic communication or cell death. We demonstrate that when isolated mitochondria are exposed to calcium and NMDA agonists, there is a significant increase in mitochondrial calcium levels. The agonist/antagonist response studies on purified mitochondria suggest the presence of a receptor on mitochondria with features similar to plasma membrane NMDA receptors. Immunogold electron microscopy of hippocampal tissue sections revealed extensive localization of NR2a subunit immunoreactivity on mitochondria. Transient transfection of neuronal GT1-7 cells with an NR1-NR2a NMDA receptor subunit cassette specifically targeting mitochondria resulted in a significant increase in mitochondrial calcium and neuroprotection against glutamate-induced cell death. Mitochondria prepared from GT1-7 cells in which the NR1 subunit of NMDA receptors was silenced demonstrated a decrease in calcium uptake. Our findings are the first to demonstrate that mitochondria express a calcium transport protein that shares characteristics with the NMDA receptor and may play a neuroprotective role.
Neurology Service, Hunter Holmes McGuire Veterans Hospital, Richmond, Virginia 23249.
Amit S
AS
Korde
Neurology Service, Hunter Holmes McGuire Veterans Hospital, Richmond, Virginia 23249; Department of Neurology, Virginia Commonwealth University, Richmond, Virginia 23298. Electronic address: william.maragos@va.gov.
William F
WF
Maragos
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006624:Hippocampus / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D002118:Calcium; D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; D016194:Receptors, N-Methyl-D-Aspartate; C409466:NR1 NMDA receptor