Role of mitochondria in kainate-induced fast Ca2+ transients in cultured spinal motor neurons.
Motor neuron death in amyotrophic lateral sclerosis (ALS) has been linked to selective vulnerability towards AMPA receptor-mediated excitotoxicity. We investigated intracellular mechanisms leading to impairment of motor neuron Ca2+ homeostasis with near physiological AMPA receptor activation. Using fast solution exchange on patch-clamped cultured neurons, kainate (KA) was applied for 2s. This induced a transient increase in the cytosolic Ca2+ concentration ([Ca2+]c) for seconds. Inhibition of the mitochondrial uniporter by RU-360 abolished the decay of the Ca2+ transient and caused immediate [Ca2+]c overload. Repetitive short KA stimulation caused a slowing of the decay of the Ca2+ transient and a gradual increase in peak and baseline [Ca2+]c in motor neurons, but not in other neurons, indicating saturation of the mitochondrial buffer. Furthermore, mitochondrial density was lower in motor neurons and, in a network of neurons with physiological synaptic AMPA receptor input, RU-360 acutely induced an increase in Ca2+ transients. We conclude that motor neurons have an insufficient mitochondrial capacity to buffer large Ca2+ elevations which is partly due to a reduced mitochondrial density per volume compared to non-motor neurons. This may exert deleterious effects in motor neuron disease where mitochondrial function is thought to be compromised.
Grosskreutz
Julian
J
Academic Neurology Unit, University of Sheffield, Medical School, United Kingdom. j.grosskreutz@sheffield.ac.uk
Haastert
Kirsten
K
Dewil
Maarten
M
Van Damme
Philip
P
Callewaert
Geert
G
Robberecht
Wim
W
Dengler
Reinhard
R
Van Den Bosch
Ludo
L
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D007608:Kainic Acid / Q000494:pharmacology*; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000502:physiology*; D008959:Models, Neurological; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D051381:Rats; D018091:Receptors, AMPA / Q000502:physiology*; D017975:Ruthenium Compounds / Q000494:pharmacology
D018091:Receptors, AMPA; C112020:Ru 360; D017975:Ruthenium Compounds; D007608:Kainic Acid; D002118:Calcium