• Vedrana Tadić, Ayse Malci, Nadine Goldhammer, Beatrice Stubendorff, Saikata Sengupta, Tino Prell, Silke Keiner, Jingyu Liu, Madlen Guenther, Christiane Frahm, Otto W Witte, and Julian Grosskreutz.
• Hans Berger Department of Neurology, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany. Electronic address: vedrana.tadic@med.uni-jena.de.
• Neuroscience. 2017 Sep 17; 359: 105118105-118.

AbstractAberrations in intracellular calcium (Ca2+) have been well established within amyotrophic lateral sclerosis (ALS), a severe motor neuron disease. Intracellular Ca2+ concentration is controlled in part through the endoplasmic reticulum (ER) mitochondria Ca2+ cycle (ERMCC). The ER supplies Ca2+ to the mitochondria at close contacts between the two organelles, i.e. the mitochondria-associated ER membranes (MAMs). The Sigma 1 receptor (Sig1R) is enriched at MAMs, where it acts as an inter-organelle signaling modulator. However, its impact on intracellular Ca2+ at the cellular level remains to be thoroughly investigated. Here, we used cultured embryonic mice spinal neurons to investigate the influence of Sig1R activation on intracellular Ca2+ homeostasis in the presence of G93AhSOD1 (G93A), an established ALS-causing mutation. Sig1R expression was increased in G93A motor neurons relative to non-transgenic (nontg) controls. Furthermore, we demonstrated significantly reduced bradykinin-sensitive intracellular Ca2+ stores in G93A spinal neurons, which were normalized by the Sig1R agonist SA4503. Moreover, SA4503 accelerated cytosolic Ca2+ clearance following a) AMPAR activation by kainate and b) IP3R-mediated ER Ca2+ release following bradykinin stimulation in both genotypes. PRE-084 (another Sig1R agonist) did not exert any significant effects on cytosolic Ca2+. Both Sig1R expression and functionality were altered by the G93A mutation, indicating the centrality of Sig1R in ALS pathology. Here, we showed that intracellular Ca2+ shuttling can be manipulated by Sig1R activation, thus demonstrating the value of using the pharmacological manipulation of Sig1R to understand Ca2+ homeostasis.Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

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