Csordas G, Renken C, Varnai P, Walter L, Weaver D, Buttle K et al.. Structural and functional features and significance of the physical linkage between ER and mitochondria. J Cell Biol 174: 915-921

Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
The Journal of Cell Biology (Impact Factor: 9.83). 10/2006; 174(7):915-21. DOI: 10.1083/jcb.200604016
Source: PubMed


The role of mitochondria in cell metabolism and survival is controlled by calcium signals that are commonly transmitted at the close associations between mitochondria and endoplasmic reticulum (ER). However, the physical linkage of the ER-mitochondria interface and its relevance for cell function remains elusive. We show by electron tomography that ER and mitochondria are adjoined by tethers that are approximately 10 nm at the smooth ER and approximately 25 nm at the rough ER. Limited proteolysis separates ER from mitochondria, whereas expression of a short "synthetic linker" (<5 nm) leads to tightening of the associations. Although normal connections are necessary and sufficient for proper propagation of ER-derived calcium signals to the mitochondria, tightened connections, synthetic or naturally observed under apoptosis-inducing conditions, make mitochondria prone to Ca2+ overloading and ensuing permeability transition. These results reveal an unexpected dependence of cell function and survival on the maintenance of proper spacing between the ER and mitochondria.

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    • "Finally, to demonstrate the importance of the ER–mitochondria contacts in modulating cellular responses, several strategies have been devised to alter the nature of ER–mitochondrial interactions. To artificially tighten organelle physical association, a synthetic linker targeted simultaneously to the OMM and the ER has been used both in vitro [14] "
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    ABSTRACT: Eukaryotic cells contain a variety of subcellular organelles, each of which performs unique tasks. Thus follows that in order to coordinate these different intracellular functions, a highly dynamic system of communication must exist between the various compartments. Direct endoplasmic reticulum (ER)-mitochondria communication is facilitated by the physical interaction of their membranes in dedicated structural domains known as mitochondria-associated membranes (MAM), which facilitate calcium (Ca(2+)) and lipid transfer between organelles and also act as platforms for signaling. Numerous studies have demonstrated the importance of MAM in ensuring correct function of both organelles, and recently MAM have been implicated in the genesis of various human diseases. Here, we review the salient structural features of interorganellar communication via MAM and discuss the most common experimental techniques employed to assess functionality of these domains. Finally, we will highlight the contribution of MAM to variety cellular functions and consider the potential role of MAM in the genesis of metabolic diseases. In doing so, the importance for cell functions of maintaining appropriate communication between ER and mitochondria will be emphasized. Copyright © 2015. Published by Elsevier B.V.
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    • "As SIGMAR1 dysfunction has been previously connected to MAM disturbances (Hayashi and Su, 2007), we quantified the level of MAMs in motor neuron cultures. As the distance between ER and mitochondria at MAMs is $10–20 nm (Csordas et al., 2006), we used an in situ proximity ligation assay (De Vos et al., 2012; Hedskog et al., 2013). Cultured motor neurons were probed with anti-ITPR3 (ER side) and anti-VDAC1 (mitochondrial side) primary antibodies followed by hybridization with secondary antibodies coupled to different oligonucleotides that hybridize together if the distance between two antibody-coupled oligonucleotides (and hence the targeted proteins) is 540 nm. "
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    ABSTRACT: Mutations in Sigma 1 receptor (SIGMAR1) have been previously identified in patients with amyotrophic lateral sclerosis and disruption of Sigmar1 in mouse leads to locomotor deficits. However, cellular mechanisms underlying motor phenotypes in human and mouse with disturbed SIGMAR1 function have not been described so far. Here we used a combination of in vivo and in vitro approaches to investigate the role of SIGMAR1 in motor neuron biology. Characterization of Sigmar1(-/-) mice revealed that affected animals display locomotor deficits associated with muscle weakness, axonal degeneration and motor neuron loss. Using primary motor neuron cultures, we observed that pharmacological or genetic inactivation of SIGMAR1 led to motor neuron axonal degeneration followed by cell death. Disruption of SIGMAR1 function in motor neurons disturbed endoplasmic reticulum-mitochondria contacts, affected intracellular calcium signalling and was accompanied by activation of endoplasmic reticulum stress and defects in mitochondrial dynamics and transport. These defects were not observed in cultured sensory neurons, highlighting the exacerbated sensitivity of motor neurons to SIGMAR1 function. Interestingly, the inhibition of mitochondrial fission was sufficient to induce mitochondria axonal transport defects as well as axonal degeneration similar to the changes observed after SIGMAR1 inactivation or loss. Intracellular calcium scavenging and endoplasmic reticulum stress inhibition were able to restore mitochondrial function and consequently prevent motor neuron degeneration. These results uncover the cellular mechanisms underlying motor neuron degeneration mediated by loss of SIGMAR1 function and provide therapeutically relevant insight into motor neuronal diseases. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email:
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    • "The mitochondrial network is also comprised of interconnected tubules but is essential for cellular respiration, Ca 2+ homeostatis, and the regulation of apoptosis (Youle and van der Bliek, 2012). While the two networks serve distinct functions, the ER and mitochondria are biophysically and biochemically associated via proteinaceous tethers and lipid microdomains that are implicated in cellular signaling (Csordá s et al., 2006; de Brito and Scorrano, 2008; Hoppins and Nunnari, 2012). "
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