title: Mitochondrial Ca(2+) Processing by a Unit of Mitochondrial Ca(2+) Uniporter and Na(+)/Ca(2+) Exchanger Supports the Neuronal Ca(2+) Influx via Activated Glutamate Receptors.
abstract: The current study demonstrates that in hippocampal neurons mitochondrial Ca(2+) processing supports Ca(2+) influx via ionotropic glutamate (Glu) receptors. We define mitochondrial Ca(2+) processing as Ca(2+) uptake via mitochondrial Ca(2+) uniporter (MCU) combined with subsequent Ca(2+) release via mitochondrial Na(+)/Ca(2+) exchanger (NCX). Our tool is to measure the Ca(2+) influx rate in primary hippocampal co-cultures, i.e. neurons and astrocytes, by fluorescent digital microscopy, using a Fura-2-quenching method where we add small amounts of Mn(2+) in the superfusion medium. Thus, Ca(2+) influx is measured with Mn(2+) in the bath. Ru360 as inhibitor of mitochondrial Ca(2+) uptake through MCU strongly reduces the rate of Ca(2+) influx in Glu-stimulated primary hippocampal neurons. Similarly, the Ca(2+) influx rate in Glu-stimulated neurons declines after suppression of potential-dependent MCU, when we depolarize mitochondria with rotenone. With inhibition of Ca(2+) release from mitochondria via NCX using CGP-37157 the Ca(2+) influx via N-methyl-D-aspartate (NMDA)- and kainate-sensitive receptors is slowed down. Working jointly as mitochondrial Ca(2+) processing unit, MCU and NCX, apparently sustain the Ca(2+) throughput of activated Glu-sensitive receptors. Our results revise the role frequently attributed to mitochondria in neuronal Ca(2+) homeostasis, where mitochondria function mainly as Ca(2+) buffer, and prevent excessively high cytosolic Ca(2+) concentration increase during neuronal activity. The mechanism to control Ca(2+) influx in neurons, as discovered in this study, highlights mitochondrial Ca(2+) processing as a promising pharmacological target. We discuss this pathway in relation to the endoplasmic reticulum-related mechanisms of Ca(2+) processing.
authors: Medizinische Fakultät, Institut für Neurobiochemie (Institut für Inflammation und Neurodegeneration), Otto-von-Guericke-Universität Magdeburg, Leipziger Straße 44, 39120, Magdeburg, Germany.
authors: Mikhail
authors: M
authors: Strokin
authors: Medizinische Fakultät, Institut für Neurobiochemie (Institut für Inflammation und Neurodegeneration), Otto-von-Guericke-Universität Magdeburg, Leipziger Straße 44, 39120, Magdeburg, Germany. georg.reiser@med.ovgu.de.
authors: Georg
authors: G
authors: Reiser
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D018920:Coculture Techniques; D005260:Female; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D017470:Receptors, Glutamate; D019831:Sodium-Calcium Exchanger; C034703:mitochondrial calcium uniporter; D002118:Calcium
keywords: Capacitative Ca2+ influx; Glutamate receptor-mediated Ca2+ entry; Mitochondrial Ca2+ processing