301
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Chaudhari N, Talwar P, Parimisetty A, Lefebvre d'Hellencourt C, Ravanan P. A molecular web: endoplasmic reticulum stress, inflammation, and oxidative stress. Front Cell Neurosci 2014; 8:213. [PMID: 25120434 PMCID: PMC4114208 DOI: 10.3389/fncel.2014.00213] [Citation(s) in RCA: 424] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Accepted: 07/15/2014] [Indexed: 12/13/2022] Open
Abstract
Execution of fundamental cellular functions demands regulated protein folding homeostasis. Endoplasmic reticulum (ER) is an active organelle existing to implement this function by folding and modifying secretory and membrane proteins. Loss of protein folding homeostasis is central to various diseases and budding evidences suggest ER stress as being a major contributor in the development or pathology of a diseased state besides other cellular stresses. The trigger for diseases may be diverse but, inflammation and/or ER stress may be basic mechanisms increasing the severity or complicating the condition of the disease. Chronic ER stress and activation of the unfolded-protein response (UPR) through endogenous or exogenous insults may result in impaired calcium and redox homeostasis, oxidative stress via protein overload thereby also influencing vital mitochondrial functions. Calcium released from the ER augments the production of mitochondrial Reactive Oxygen Species (ROS). Toxic accumulation of ROS within ER and mitochondria disturbs fundamental organelle functions. Sustained ER stress is known to potentially elicit inflammatory responses via UPR pathways. Additionally, ROS generated through inflammation or mitochondrial dysfunction could accelerate ER malfunction. Dysfunctional UPR pathways have been associated with a wide range of diseases including several neurodegenerative diseases, stroke, metabolic disorders, cancer, inflammatory disease, diabetes mellitus, cardiovascular disease, and others. In this review, we have discussed the UPR signaling pathways, and networking between ER stress-induced inflammatory pathways, oxidative stress, and mitochondrial signaling events, which further induce or exacerbate ER stress.
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Affiliation(s)
- Namrata Chaudhari
- Apoptosis and Cell Death Research Lab, School of Biosciences and Technology, Vellore Institute of Technology University , Vellore , India
| | - Priti Talwar
- Apoptosis and Cell Death Research Lab, School of Biosciences and Technology, Vellore Institute of Technology University , Vellore , India
| | - Avinash Parimisetty
- Groupe d'Etude sur l'Inflammation Chronique et l'Obésité, EA 41516, Plateforme CYROI, Université de La Réunion , Saint Denis de La Réunion , France
| | - Christian Lefebvre d'Hellencourt
- Groupe d'Etude sur l'Inflammation Chronique et l'Obésité, EA 41516, Plateforme CYROI, Université de La Réunion , Saint Denis de La Réunion , France
| | - Palaniyandi Ravanan
- Apoptosis and Cell Death Research Lab, School of Biosciences and Technology, Vellore Institute of Technology University , Vellore , India
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302
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Hurlock AK, Roston RL, Wang K, Benning C. Lipid trafficking in plant cells. Traffic 2014; 15:915-32. [PMID: 24931800 DOI: 10.1111/tra.12187] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 06/12/2014] [Accepted: 06/12/2014] [Indexed: 12/29/2022]
Abstract
Plant cells contain unique organelles such as chloroplasts with an extensive photosynthetic membrane. In addition, specialized epidermal cells produce an extracellular cuticle composed primarily of lipids, and storage cells accumulate large amounts of storage lipids. As lipid assembly is associated only with discrete membranes or organelles, there is a need for extensive lipid trafficking within plant cells, more so in specialized cells and sometimes also in response to changing environmental conditions such as phosphate deprivation. Because of the complexity of plant lipid metabolism and the inherent recalcitrance of membrane lipid transporters, the mechanisms of lipid transport within plant cells are not yet fully understood. Recently, several new proteins have been implicated in different aspects of plant lipid trafficking. While these proteins provide only first insights into limited aspects of lipid transport phenomena in plant cells, they represent exciting opportunities for further studies.
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Affiliation(s)
- Anna K Hurlock
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA; Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
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303
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Lee GH, Lee HY, Li B, Kim HR, Chae HJ. Bax inhibitor-1-mediated inhibition of mitochondrial Ca2+ intake regulates mitochondrial permeability transition pore opening and cell death. Sci Rep 2014; 4:5194. [PMID: 24899098 PMCID: PMC4046133 DOI: 10.1038/srep05194] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 05/20/2014] [Indexed: 12/13/2022] Open
Abstract
A recently studied endoplasmic reticulum (ER) stress regulator, Bax inhibitor-1 (BI-1) plays a regulatory role in mitochondrial Ca2+ levels. In this study, we identified ER-resident and mitochondria-associated ER membrane (MAM)-resident populations of BI-1. ER stress increased mitochondrial Ca2+ to a lesser extent in BI-1–overexpressing cells (HT1080/BI-1) than in control cells, most likely as a result of impaired mitochondrial Ca2+ intake ability and lower basal levels of intra-ER Ca2+. Moreover, opening of the Ca2+-induced mitochondrial permeability transition pore (PTP) and cytochrome c release were regulated by BI-1. In HT1080/BI-1, the basal mitochondrial membrane potential was low and also resistant to Ca2+ compared with control cells. The activity of the mitochondrial membrane potential-dependent mitochondrial Ca2+ intake pore, the Ca2+ uniporter, was reduced in the presence of BI-1. This study also showed that instead of Ca2+, other cations including K+ enter the mitochondria of HT1080/BI-1 through mitochondrial Ca2+-dependent ion channels, providing a possible mechanism by which mitochondrial Ca2+ intake is reduced, leading to cell protection. We propose a model in which BI-1–mediated sequential regulation of the mitochondrial Ca2+ uniporter and Ca2+-dependent K+ channel opening inhibits mitochondrial Ca2+ intake, thereby inhibiting PTP function and leading to cell protection.
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Affiliation(s)
- Geum-Hwa Lee
- Department of Pharmacology and Cardiovascular Research Institute, Medical School, Chonbuk National University, Jeonju, 561-181, Republic of Korea
| | - Hwa-Young Lee
- Department of Pharmacology and Cardiovascular Research Institute, Medical School, Chonbuk National University, Jeonju, 561-181, Republic of Korea
| | - Bo Li
- Department of Pharmacology and Cardiovascular Research Institute, Medical School, Chonbuk National University, Jeonju, 561-181, Republic of Korea
| | - Hyung-Ryong Kim
- Department of Dental Pharmacology and Wonkwang Dental Research Institute, School of Dentistry, Wonkwang University, Iksan, 570-749, Republic of Korea
| | - Han-Jung Chae
- Department of Pharmacology and Cardiovascular Research Institute, Medical School, Chonbuk National University, Jeonju, 561-181, Republic of Korea
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304
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Paul P, Simm S, Mirus O, Scharf KD, Fragkostefanakis S, Schleiff E. The complexity of vesicle transport factors in plants examined by orthology search. PLoS One 2014; 9:e97745. [PMID: 24844592 PMCID: PMC4028247 DOI: 10.1371/journal.pone.0097745] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 04/24/2014] [Indexed: 11/18/2022] Open
Abstract
Vesicle transport is a central process to ensure protein and lipid distribution in eukaryotic cells. The current knowledge on the molecular components and mechanisms of this process is majorly based on studies in Saccharomyces cerevisiae and Arabidopsis thaliana, which revealed 240 different proteinaceous factors either experimentally proven or predicted to be involved in vesicle transport. In here, we performed an orthologue search using two different algorithms to identify the components of the secretory pathway in yeast and 14 plant genomes by using the 'core-set' of 240 factors as bait. We identified 4021 orthologues and (co-)orthologues in the discussed plant species accounting for components of COP-II, COP-I, Clathrin Coated Vesicles, Retromers and ESCRTs, Rab GTPases, Tethering factors and SNAREs. In plants, we observed a significantly higher number of (co-)orthologues than yeast, while only 8 tethering factors from yeast seem to be absent in the analyzed plant genomes. To link the identified (co-)orthologues to vesicle transport, the domain architecture of the proteins from yeast, genetic model plant A. thaliana and agriculturally relevant crop Solanum lycopersicum has been inspected. For the orthologous groups containing (co-)orthologues from yeast, A. thaliana and S. lycopersicum, we observed the same domain architecture for 79% (416/527) of the (co-)orthologues, which documents a very high conservation of this process. Further, publically available tissue-specific expression profiles for a subset of (co-)orthologues found in A. thaliana and S. lycopersicum suggest that some (co-)orthologues are involved in tissue-specific functions. Inspection of localization of the (co-)orthologues based on available proteome data or localization predictions lead to the assignment of plastid- as well as mitochondrial localized (co-)orthologues of vesicle transport factors and the relevance of this is discussed.
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Affiliation(s)
- Puneet Paul
- Department of Biosciences Molecular Cell Biology of Plants
| | - Stefan Simm
- Department of Biosciences Molecular Cell Biology of Plants
| | - Oliver Mirus
- Department of Biosciences Molecular Cell Biology of Plants
| | | | | | - Enrico Schleiff
- Department of Biosciences Molecular Cell Biology of Plants
- Cluster of Excellence Frankfurt
- Center of Membrane Proteomics; Goethe University Frankfurt, Frankfurt/Main, Germany
- * E-mail:
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305
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Sørensen DM, Holen HW, Holemans T, Vangheluwe P, Palmgren MG. Towards defining the substrate of orphan P5A-ATPases. Biochim Biophys Acta Gen Subj 2014; 1850:524-35. [PMID: 24836520 DOI: 10.1016/j.bbagen.2014.05.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 11/16/2022]
Abstract
BACKGROUND P-type ATPases are ubiquitous ion and lipid pumps found in cellular membranes. P5A-ATPases constitute a poorly characterized subfamily of P-type ATPases present in all eukaryotic organisms but for which a transported substrate remains to be identified. SCOPE OF REVIEW This review aims to discuss the available evidence which could lead to identification of possible substrates of P5A-ATPases. MAJOR CONCLUSIONS The complex phenotypes resulting from the loss of P5A-ATPases in model organisms can be explained by a role of the P5A-ATPase in the endoplasmic reticulum (ER), where loss of function leads to broad and unspecific phenotypes related to the impairment of basic ER functions such as protein folding and processing. Genetic interactions in Saccharomyces cerevisiae point to a role of the endogenous P5A-ATPase Spf1p in separation of charges in the ER, in sterol metabolism, and in insertion of tail-anchored proteins in the ER membrane. A role for P5A-ATPases in vesicle formation would explain why sterol transport and distribution are affected in knock out cells, which in turn has a negative impact on the spontaneous insertion of tail-anchored proteins. It would also explain why secretory proteins destined for the Golgi and the cell wall have difficulties in reaching their final destination. Cations and phospholipids could both be transported substrates of P5A-ATPases and as each carry charges, transport of either might explain why a charge difference arises across the ER membrane. GENERAL SIGNIFICANCE Identification of the substrate of P5A-ATPases would throw light on an important general process in the ER that is still not fully understood. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
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Affiliation(s)
- Danny Mollerup Sørensen
- Centre for Membrane Pumps in Cells and Disease-PUMPkin, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Henrik Waldal Holen
- Centre for Membrane Pumps in Cells and Disease-PUMPkin, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Tine Holemans
- Department of Cellular and Molecular Medicine, ON1 Campus Gasthuisberg, Katholieke Universiteit Leuven, Herestraat 49, Box 802, B3000 Leuven, Belgium
| | - Peter Vangheluwe
- Department of Cellular and Molecular Medicine, ON1 Campus Gasthuisberg, Katholieke Universiteit Leuven, Herestraat 49, Box 802, B3000 Leuven, Belgium
| | - Michael G Palmgren
- Centre for Membrane Pumps in Cells and Disease-PUMPkin, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
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306
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De Bock M, Decrock E, Wang N, Bol M, Vinken M, Bultynck G, Leybaert L. The dual face of connexin-based astroglial Ca(2+) communication: a key player in brain physiology and a prime target in pathology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2211-32. [PMID: 24768716 DOI: 10.1016/j.bbamcr.2014.04.016] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/21/2022]
Abstract
For decades, studies have been focusing on the neuronal abnormalities that accompany neurodegenerative disorders. Yet, glial cells are emerging as important players in numerous neurological diseases. Astrocytes, the main type of glia in the central nervous system , form extensive networks that physically and functionally connect neuronal synapses with cerebral blood vessels. Normal brain functioning strictly depends on highly specialized cellular cross-talk between these different partners to which Ca(2+), as a signaling ion, largely contributes. Altered intracellular Ca(2+) levels are associated with neurodegenerative disorders and play a crucial role in the glial responses to injury. Intracellular Ca(2+) increases in single astrocytes can be propagated toward neighboring cells as intercellular Ca(2+) waves, thereby recruiting a larger group of cells. Intercellular Ca(2+) wave propagation depends on two, parallel, connexin (Cx) channel-based mechanisms: i) the diffusion of inositol 1,4,5-trisphosphate through gap junction channels that directly connect the cytoplasm of neighboring cells, and ii) the release of paracrine messengers such as glutamate and ATP through hemichannels ('half of a gap junction channel'). This review gives an overview of the current knowledge on Cx-mediated Ca(2+) communication among astrocytes as well as between astrocytes and other brain cell types in physiology and pathology, with a focus on the processes of neurodegeneration and reactive gliosis. Research on Cx-mediated astroglial Ca(2+) communication may ultimately shed light on the development of targeted therapies for neurodegenerative disorders in which astrocytes participate. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium.
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, B-1090 Brussels, Belgium
| | - Geert Bultynck
- Department of Cellular and Molecular Medicine, Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N-I bus 802, B-3000 Leuven, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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307
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Proteomic survey reveals altered energetic patterns and metabolic failure prior to retinal degeneration. J Neurosci 2014; 34:2797-812. [PMID: 24553922 DOI: 10.1523/jneurosci.2982-13.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Inherited mutations that lead to misfolding of the visual pigment rhodopsin (Rho) are a prominent cause of photoreceptor neuron (PN) degeneration and blindness. How Rho proteotoxic stress progressively impairs PN viability remains unknown. To identify the pathways that mediate Rho toxicity in PNs, we performed a comprehensive proteomic profiling of retinas from Drosophila transgenics expressing Rh1(P37H), the equivalent of mammalian Rho(P23H), the most common Rho mutation linked to blindness in humans. Profiling of young Rh1(P37H) retinas revealed a coordinated upregulation of energy-producing pathways and attenuation of energy-consuming pathways involving target of rapamycin (TOR) signaling, which was reversed in older retinas at the onset of PN degeneration. We probed the relevance of these metabolic changes to PN survival by using a combination of pharmacological and genetic approaches. Chronic suppression of TOR signaling, using the inhibitor rapamycin, strongly mitigated PN degeneration, indicating that TOR signaling activation by chronic Rh1(P37H) proteotoxic stress is deleterious for PNs. Genetic inactivation of the endoplasmic reticulum stress-induced JNK/TRAF1 axis as well as the APAF-1/caspase-9 axis, activated by damaged mitochondria, dramatically suppressed Rh1(P37H)-induced PN degeneration, identifying the mitochondria as novel mediators of Rh1(P37H) toxicity. We thus propose that chronic Rh1(P37H) proteotoxic stress distorts the energetic profile of PNs leading to metabolic imbalance, mitochondrial failure, and PN degeneration and therapies normalizing metabolic function might be used to alleviate Rh1(P37H) toxicity in the retina. Our study offers a glimpse into the intricate higher order interactions that underlie PN dysfunction and provides a useful resource for identifying other molecular networks that mediate Rho toxicity in PNs.
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308
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Marchi S, Giorgi C, Oparka M, Duszynski J, Wieckowski MR, Pinton P. Oncogenic and oncosuppressive signal transduction at mitochondria-associated endoplasmic reticulum membranes. Mol Cell Oncol 2014; 1:e956469. [PMID: 27308328 PMCID: PMC4905193 DOI: 10.4161/23723548.2014.956469] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2014] [Revised: 07/14/2014] [Accepted: 07/17/2014] [Indexed: 12/22/2022]
Abstract
The different mechanisms employed by proto-oncogenes and tumor suppressors to regulate cell death pathways are strictly linked to their localization. In addition to the canonical control of apoptosis at a transcriptional/nuclear level, intracellular zones are emerging as pivotal sites for the activities of several proapoptotic and antiapoptotic factors. Here, we review the function of the endoplasmic reticulum-mitochondria interface as a primary platform for decoding danger signals as well as a structural accommodation for several regulator or effector proteins.
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Affiliation(s)
- Saverio Marchi
- Department of Morphology; Surgery and Experimental Medicine; Section of Pathology; Oncology and Experimental Biology and LTTA Center; University of Ferrara; Ferrara, Italy
| | - Carlotta Giorgi
- Department of Morphology; Surgery and Experimental Medicine; Section of Pathology; Oncology and Experimental Biology and LTTA Center; University of Ferrara; Ferrara, Italy
| | - Monika Oparka
- Department of Biochemistry; Nencki Institute of Experimental Biology; Warsaw, Poland
| | - Jerzy Duszynski
- Department of Biochemistry; Nencki Institute of Experimental Biology; Warsaw, Poland
| | - Mariusz R Wieckowski
- Department of Biochemistry; Nencki Institute of Experimental Biology; Warsaw, Poland
| | - Paolo Pinton
- Department of Morphology; Surgery and Experimental Medicine; Section of Pathology; Oncology and Experimental Biology and LTTA Center; University of Ferrara; Ferrara, Italy
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309
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Zheng Y, Cretoiu D, Yan G, Cretoiu SM, Popescu LM, Wang X. Comparative proteomic analysis of human lung telocytes with fibroblasts. J Cell Mol Med 2014; 18:568-89. [PMID: 24674459 PMCID: PMC4000110 DOI: 10.1111/jcmm.12290] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/24/2014] [Indexed: 12/22/2022] Open
Abstract
Telocytes (TCs) were recently described as interstitial cells with very long prolongations named telopodes (Tps; http://www.telocytes.com). Establishing the TC proteome is a priority to show that TCs are a distinct type of cells. Therefore, we examined the molecular aspects of lung TCs by comparison with fibroblasts (FBs). Proteins extracted from primary cultures of these cells were analysed by automated 2-dimensional nano-electrospray ionization liquid chromatography tandem mass spectrometry (2D Nano-ESI LC-MS/MS). Differentially expressed proteins were screened by two-sample t-test (P < 0.05) and fold change (>2), based on the bioinformatics analysis. We identified hundreds of proteins up- or down-regulated, respectively, in TCs as compared with FBs. TC proteins with known identities are localized in the cytoskeleton (87%) and plasma membrane (13%), while FB up-regulated proteins are in the cytoskeleton (75%) and destined to extracellular matrix (25%). These identified proteins were classified into different categories based on their molecular functions and biological processes. While the proteins identified in TCs are mainly involved in catalytic activity (43%) and as structural molecular activity (25%), the proteins in FBs are involved in catalytic activity (24%) and in structural molecular activity, particularly synthesis of collagen and other extracellular matrix components (25%). Anyway, our data show that TCs are completely different from FBs. In conclusion, we report here the first extensive identification of proteins from TCs using a quantitative proteomics approach. Protein expression profile shows many up-regulated proteins e.g. myosin-14, periplakin, suggesting that TCs might play specific roles in mechanical sensing and mechanochemical conversion task, tissue homoeostasis and remodelling/renewal. Furthermore, up-regulated proteins matching those found in extracellular vesicles emphasize TCs roles in intercellular signalling and stem cell niche modulation. The novel proteins identified in TCs will be an important resource for further proteomic research and it will possibly allow biomarker identification for TCs. It also creates the premises for understanding the pathogenesis of some lung diseases involving TCs.
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Affiliation(s)
- Yonghua Zheng
- Department of Respirology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
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310
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Hellman B, Grapengiesser E. Glucose-induced inhibition of insulin secretion. Acta Physiol (Oxf) 2014; 210:479-88. [PMID: 24354538 DOI: 10.1111/apha.12217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/04/2013] [Accepted: 12/16/2013] [Indexed: 12/14/2022]
Abstract
Increase in glucose is known to elevate the concentration of cytoplasmic Ca(2+) ([Ca(2+) ]i ) in pancreatic β-cells and stimulate insulin secretion. However, rise of glucose can also lower [Ca(2+) ]i and inhibit insulin release. In the present review, we examine the mechanisms for this inhibition and highlight its importance for the healthy β-cell and the development of diabetes. It is possible to distinguish between 60 and 90 s of prompt inhibition and the late inhibition seen after the first-phase peak of insulin release. The introductory inhibition is characteristic of the healthy β-cell and mediated by sequestration of [Ca(2+) ]i in the endoplasmic reticulum. This inhibition is easily seen in studies of isolated islets but too brief to be detected in a conventional intravenous glucose tolerance test. Coupled to simultaneous rise of glucagon, the introductory suppression of insulin release is the starting point for the antiphase relation between the subsequent insulin and glucagon pulses. Another effect of the initial suppression is to increase the pool of readily releasable granules responsible for the first-phase release of insulin. The presence of late inhibition of insulin release is an indicator of β-cell dysfunction. Patients with type 2 diabetes often respond to intravenous bolus injection of glucose with 5-10 min of late suppression of circulating insulin.
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Affiliation(s)
- B. Hellman
- Department of Medical Cell Biology; University of Uppsala; Uppsala Sweden
| | - E. Grapengiesser
- Department of Medical Cell Biology; University of Uppsala; Uppsala Sweden
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311
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Escobar-Henriques M, Langer T. Dynamic survey of mitochondria by ubiquitin. EMBO Rep 2014; 15:231-43. [PMID: 24569520 PMCID: PMC3989689 DOI: 10.1002/embr.201338225] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 01/16/2014] [Accepted: 01/20/2014] [Indexed: 12/27/2022] Open
Abstract
Ubiquitin is a post-translational modifier with proteolytic and non-proteolytic roles in many biological processes. At mitochondria, it performs regulatory homeostatic functions and contributes to mitochondrial quality control. Ubiquitin is essential for mitochondrial fusion, regulates mitochondria-ER contacts, and participates in maternal mtDNA inheritance. Under stress, mitochondrial dysfunction induces ubiquitin-dependent responses that involve mitochondrial proteome remodeling and culminate in organelle removal by mitophagy. In addition, many ubiquitin-dependent mechanisms have been shown to regulate innate immune responses and xenophagy. Here, we review the emerging roles of ubiquitin at mitochondria.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Institute for Genetics, Centre for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of CologneCologne, Germany
| | - Thomas Langer
- Institute for Genetics, Centre for Molecular Medicine (CMMC), Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of CologneCologne, Germany
- Max-Planck-Institute for the Biology of AgingCologne, Germany
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312
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Abstract
Target of rapamycin (TOR) forms two conserved, structurally distinct kinase complexes termed TOR complex 1 (TORC1) and TORC2. Each complex phosphorylates a different set of substrates to regulate cell growth. In mammals, mTOR is stimulated by nutrients and growth factors and inhibited by stress to ensure that cells grow only during favorable conditions. Studies in different organisms have reported localization of TOR to several distinct subcellular compartments. Notably, the finding that mTORC1 is localized to the lysosome has significantly enhanced our understanding of mTORC1 regulation. Subcellular localization may be a general principle used by TOR to enact precise spatial and temporal control of cell growth.
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Affiliation(s)
- Charles Betz
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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313
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No evidence for a local renin-angiotensin system in liver mitochondria. Sci Rep 2014; 3:2467. [PMID: 23959064 PMCID: PMC3747509 DOI: 10.1038/srep02467] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/22/2013] [Indexed: 01/01/2023] Open
Abstract
The circulating, endocrine renin-angiotensin system (RAS) is important to circulatory homeostasis, while ubiquitous tissue and cellular RAS play diverse roles, including metabolic regulation. Indeed, inhibition of RAS is associated with improved cellular oxidative capacity. Recently it has been suggested that an intra-mitochondrial RAS directly impacts on metabolism. Here we sought to rigorously explore this hypothesis. Radiolabelled ligand-binding and unbiased proteomic approaches were applied to purified mitochondrial sub-fractions from rat liver, and the impact of AngII on mitochondrial function assessed. Whilst high-affinity AngII binding sites were found in the mitochondria-associated membrane (MAM) fraction, no RAS components could be detected in purified mitochondria. Moreover, AngII had no effect on the function of isolated mitochondria at physiologically relevant concentrations. We thus found no evidence of endogenous mitochondrial AngII production, and conclude that the effects of AngII on cellular energy metabolism are not mediated through its direct binding to mitochondrial targets.
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314
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Abstract
Fission and fusion of mitochondrial tubules are the main processes determining mitochondrial shape and size in cells. As more evidence is found for the involvement of mitochondrial morphology in human pathology, it is important to elucidate the mechanisms of mitochondrial fission and fusion. Mitochondrial morphology is highly sensitive to changing environmental conditions, indicating the involvement of cellular signaling pathways. In addition, the well-established structural connection between the endoplasmic reticulum (ER) and mitochondria has recently been found to play a role in mitochondrial fission. This minireview describes the latest advancements in understanding the regulatory mechanisms controlling mitochondrial morphology, as well as the ER-mediated structural maintenance of mitochondria, with a specific emphasis on mitochondrial fission.
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Affiliation(s)
- Hakjoo Lee
- Department of Physiology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912,
USA
| | - Yisang Yoon
- Department of Physiology, Medical College of Georgia, Georgia Regents University, Augusta, GA 30912,
USA
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315
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Kamp DW, Liu G, Cheresh P, Kim SJ, Mueller A, Lam AP, Trejo H, Williams D, Tulasiram S, Baker M, Ridge K, Chandel NS, Beri R. Asbestos-induced alveolar epithelial cell apoptosis. The role of endoplasmic reticulum stress response. Am J Respir Cell Mol Biol 2014; 49:892-901. [PMID: 23885834 DOI: 10.1165/rcmb.2013-0053oc] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Asbestos exposure results in pulmonary fibrosis (asbestosis) and malignancies (bronchogenic lung cancer and mesothelioma) by mechanisms that are not fully understood. Alveolar epithelial cell (AEC) apoptosis is important in the development of pulmonary fibrosis after exposure to an array of toxins, including asbestos. An endoplasmic reticulum (ER) stress response and mitochondria-regulated (intrinsic) apoptosis occur in AECs of patients with idiopathic pulmonary fibrosis, a disease with similarities to asbestosis. Asbestos induces AEC intrinsic apoptosis, but the role of the ER is unclear. The objective of this study was to determine whether asbestos causes an AEC ER stress response that promotes apoptosis. Using human A549 and rat primary isolated alveolar type II cells, amosite asbestos fibers increased AEC mRNA and protein expression of ER stress proteins involved in the unfolded protein response, such as inositol-requiring kinase (IRE) 1 and X-box-binding protein-1, as well as ER Ca²(2+) release ,as assessed by a FURA-2 assay. Eukarion-134, a superoxide dismutase/catalase mimetic, as well as overexpression of Bcl-XL in A549 cells each attenuate asbestos-induced AEC ER stress (IRE-1 and X-box-binding protein-1 protein expression; ER Ca²(2+) release) and apoptosis. Thapsigargin, a known ER stress inducer, augments AEC apoptosis, and eukarion-134 or Bcl-XL overexpression are protective. Finally, 4-phenylbutyric acid, a chemical chaperone that attenuates ER stress, blocks asbestos- and thapsigargin-induced AEC IRE-1 protein expression, but does not reduce ER Ca²(2+) release or apoptosis. These results show that asbestos triggers an AEC ER stress response and subsequent intrinsic apoptosis that is mediated in part by ER Ca²(2+) release.
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Affiliation(s)
- David W Kamp
- 1 Department of Medicine, Division of Pulmonary & Critical Care Medicine, Jesse Brown Veterans Affairs Medical Center and Northwestern University Feinberg School of Medicine, Chicago, Illinois; and
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317
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Hughes BG, Fan X, Cho WJ, Schulz R. MMP-2 is localized to the mitochondria-associated membrane of the heart. Am J Physiol Heart Circ Physiol 2013; 306:H764-70. [PMID: 24375642 DOI: 10.1152/ajpheart.00909.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Matrix metalloproteinase-2 (MMP-2) has been extensively studied in the context of extracellular matrix remodeling but is also localized within cells and can be activated by prooxidants to proteolyze specific intercellular targets. Although there are reports of MMP-2 in mitochondria, a critical source of cellular oxidative stress, these studies did not take into account the presence within their preparations of the mitochondria-associated membrane (MAM), a subdomain of the endoplasmic reticulum (ER). We hypothesized that MMP-2 is situated in the MAM and therefore investigated its subcellular distribution between mitochondria and the MAM. Immunogold electron microscopy revealed MMP-2 localized in mitochondria of heart sections from mice. In contrast, immunofluorescence analysis of an MMP-2:HaloTag fusion protein expressed in HL-1 cardiomyocytes showed an ER-like distribution, with greater colocalization with an ER marker (protein disulfide isomerase) relative to the mitochondrial marker, MitoTracker red. Although MMP-2 protein and enzymatic activity were present in crude mitochondrial fractions, once these were separated into purified mitochondria and MAM, MMP-2 was principally associated with the latter. Thus, although mitochondria may contain minimal levels of MMP-2, the majority of MMP-2 previously identified as "mitochondrial" is in fact associated with the MAM. We also found that calreticulin, an ER- and MAM-resident Ca(2+) handling protein and chaperone, could be proteolyzed by MMP-2 in vitro. MAM-localized MMP-2 could therefore potentially impact mitochondrial function by affecting ER-mitochondrial Ca(2+) signaling via its proteolysis of calreticulin.
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Affiliation(s)
- Bryan G Hughes
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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318
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MAM (mitochondria-associated membranes) in mammalian cells: lipids and beyond. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:595-609. [PMID: 24316057 DOI: 10.1016/j.bbalip.2013.11.014] [Citation(s) in RCA: 446] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 11/21/2013] [Accepted: 11/27/2013] [Indexed: 12/15/2022]
Abstract
One mechanism by which communication between the endoplasmic reticulum (ER) and mitochondria is achieved is by close juxtaposition between these organelles via mitochondria-associated membranes (MAM). The MAM consist of a region of the ER that is enriched in several lipid biosynthetic enzyme activities and becomes reversibly tethered to mitochondria. Specific proteins are localized, sometimes transiently, in the MAM. Several of these proteins have been implicated in tethering the MAM to mitochondria. In mammalian cells, formation of these contact sites between MAM and mitochondria appears to be required for key cellular events including the transport of calcium from the ER to mitochondria, the import of phosphatidylserine into mitochondria from the ER for decarboxylation to phosphatidylethanolamine, the formation of autophagosomes, regulation of the morphology, dynamics and functions of mitochondria, and cell survival. This review focuses on the functions proposed for MAM in mediating these events in mammalian cells. In light of the apparent involvement of MAM in multiple fundamental cellular processes, recent studies indicate that impaired contact between MAM and mitochondria might underlie the pathology of several human neurodegenerative diseases, including Alzheimer's disease. Moreover, MAM has been implicated in modulating glucose homeostasis and insulin resistance, as well as in some viral infections.
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319
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Nicolson GL, Ash ME. Lipid Replacement Therapy: a natural medicine approach to replacing damaged lipids in cellular membranes and organelles and restoring function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1657-79. [PMID: 24269541 DOI: 10.1016/j.bbamem.2013.11.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 10/30/2013] [Accepted: 11/09/2013] [Indexed: 12/14/2022]
Abstract
Lipid Replacement Therapy, the use of functional oral supplements containing cell membrane phospholipids and antioxidants, has been used to replace damaged, usually oxidized, membrane glycerophospholipids that accumulate during aging and in various clinical conditions in order to restore cellular function. This approach differs from other dietary and intravenous phospholipid interventions in the composition of phospholipids and their defense against oxidation during storage, ingestion, digestion and uptake as well as the use of protective molecules that noncovalently complex with phospholipid micelles and prevent their enzymatic and bile disruption. Once the phospholipids have been taken in by transport processes, they are protected by several natural mechanisms involving lipid receptors, transport and carrier molecules and circulating cells and lipoproteins until their delivery to tissues and cells where they can again be transferred to intracellular membranes by specific and nonspecific transport systems. Once delivered to membrane sites, they naturally replace and stimulate removal of damaged membrane lipids. Various chronic clinical conditions are characterized by membrane damage, mainly oxidative but also enzymatic, resulting in loss of cellular function. This is readily apparent in mitochondrial inner membranes where oxidative damage to phospholipids like cardiolipin and other molecules results in loss of trans-membrane potential, electron transport function and generation of high-energy molecules. Recent clinical trials have shown the benefits of Lipid Replacement Therapy in restoring mitochondrial function and reducing fatigue in aged subjects and patients with a variety of clinical diagnoses that are characterized by loss of mitochondrial function and include fatigue as a major symptom. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Affiliation(s)
- Garth L Nicolson
- Department of Molecular Pathology, The Institute for Molecular Medicine, Huntington Beach, CA 92649, USA.
| | - Michael E Ash
- Clinical Education, Newton Abbot, Devon TQ12 4SG, UK
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320
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Marchi S, Patergnani S, Pinton P. The endoplasmic reticulum-mitochondria connection: one touch, multiple functions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:461-9. [PMID: 24211533 DOI: 10.1016/j.bbabio.2013.10.015] [Citation(s) in RCA: 356] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 10/29/2013] [Accepted: 10/31/2013] [Indexed: 12/14/2022]
Abstract
The endoplasmic reticulum (ER) and mitochondria are tubular organelles with a characteristic "network structure" that facilitates the formation of interorganellar connections. The ER and mitochondria join together at multiple contact sites to form specific domains, termed mitochondria-ER associated membranes (MAMs), with distinct biochemical properties and a characteristic set of proteins. The functions of these two organelles are coordinated and executed at the ER-mitochondria interface, which provides a platform for the regulation of different processes. The roles played by the ER-mitochondria interface range from the coordination of calcium transfer to the regulation of mitochondrial fission and inflammasome formation as well as the provision of membranes for autophagy. The novel and unconventional processes that occur at the ER-mitochondria interface demonstrate its multifunctional and intrinsically dynamic nature. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components.
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Affiliation(s)
- Saverio Marchi
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Interdisciplinary Center for the Study of Inflammation (ICSI), Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
| | - Simone Patergnani
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Interdisciplinary Center for the Study of Inflammation (ICSI), Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy
| | - Paolo Pinton
- Department of Morphology, Surgery and Experimental Medicine, Section of Pathology, Oncology and Experimental Biology, Interdisciplinary Center for the Study of Inflammation (ICSI), Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, 44121 Ferrara, Italy.
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321
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Liu ZW, Zhu HT, Chen KL, Dong X, Wei J, Qiu C, Xue JH. Protein kinase RNA-like endoplasmic reticulum kinase (PERK) signaling pathway plays a major role in reactive oxygen species (ROS)-mediated endoplasmic reticulum stress-induced apoptosis in diabetic cardiomyopathy. Cardiovasc Diabetol 2013; 12:158. [PMID: 24180212 PMCID: PMC4176998 DOI: 10.1186/1475-2840-12-158] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 10/29/2013] [Indexed: 12/12/2022] Open
Abstract
Background Endoplasmic reticulum (ER) stress is considered one of the mechanisms contributing to reactive oxygen species (ROS)- mediated cell apoptosis. In diabetic cardiomyopathy (DCM), cell apoptosis is generally accepted as the etiological factor and closely related to cardiac ROS generation. ER stress is proposed the link between ROS and cell apoptosis; however, the signaling pathways and their roles in participating ER stress- induced apoptosis in DCM are still unclear. Methods In this study, we investigated the signaling transductions in ROS- dependent ER stress- induced cardiomocyte apoptosis in animal model of DCM. Moreover, in order to clarify the roles of IRE1 (inositol - requiring enzyme-1), PERK (protein kinase RNA (PKR)- like ER kinase) and ATF6 (activating transcription factor-6) in conducting apoptotic signal in ROS- dependent ER stress- induced cardiomocyte apoptosis, we further investigated apoptosis in high- glucose incubated cardiomyocytes with IRE1, ATF6 and PERK- knocked down respectively. Results we demonstrated that the ER stress sensors, referred as PERK, IRE1 and ATF6, were activated in ROS- mediated ER stress- induced cell apoptosis in rat model of DCM which was characterized by cardiac pump and electrical dysfunctions. The deletion of PERK in myocytes exhibited stronger protective effect against apoptosis induced by high- glucose incubation than deletion of ATF6 or IRE in the same myocytes. By subcellular fractionation, rather than ATF6 and IRE1, in primary cardiomyocytes, PERK was found a component of MAMs (mitochondria-associated endoplasmic reticulum membranes) which was the functional and physical contact site between ER and mitochondria. Conclusions ROS- stimulated activation of PERK signaling pathway takes the major responsibility rather than IRE1 or ATF6 signaling pathways in ROS- medicated ER stress- induced myocyte apoptosis in DCM.
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Affiliation(s)
| | | | | | | | | | | | - Jia-Hong Xue
- Department of Cardiology, Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an, Shaanxi, China.
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322
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Chan SN, Tang BL. Location and membrane sources for autophagosome formation - from ER-mitochondria contact sites to Golgi-endosome-derived carriers. Mol Membr Biol 2013; 30:394-402. [PMID: 24175710 DOI: 10.3109/09687688.2013.850178] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent advances have revealed much about the signaling events and molecular components associated with autophagy. Although it is clear that there are multiple points of intersection and connection between autophagy and known vesicular membrane transport processes between membrane compartments, autophagy is modulated by a distinct set of molecular components, and the autophagosome has a unique membrane composition. A key question that has yet to be resolved with regards to autophagosome formation is its membrane source. Various evidences have indicated that membranes from the endoplasmic reticulum (ER), mitochondria, Golgi, endosomes and the plasma membrane could all potentially act as a source of autophagosomal membrane in non-specialized macroautophagy. Recent investigations have generated advances in terms of the mitochondria's involvement in starvation-induced autophagy, and refined localization of autophagosome formation to ER-mitochondria contact sites. On the other hand, data accumulates on the delivery of membrane sources to the pre-autophagosome structure by Atg9-containing mobile carriers, which likely originated from the Golgi-endosome system. The answer to the question on the origin of membrane materials for autophagosome biogenesis awaits further reconciliation of these different findings.
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Affiliation(s)
- Shu Ning Chan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University Health System, NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore , Medical Drive , Singapore
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323
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p32 protein levels are integral to mitochondrial and endoplasmic reticulum morphology, cell metabolism and survival. Biochem J 2013; 453:381-91. [PMID: 23692256 PMCID: PMC3727215 DOI: 10.1042/bj20121829] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
p32 [also known as HABP1 (hyaluronan-binding protein 1), gC1qR (receptor for globular head domains complement 1q) or C1qbp (complement 1q-binding protein)] has been shown previously to have both mitochondrial and non-mitochondrial localization and functions. In the present study, we show for the first time that endogenous p32 protein is a mitochondrial protein in HeLa cells under control and stress conditions. In defining the impact of altering p32 levels in these cells, we demonstrate that the overexpression of p32 increased mitochondrial fibrils. Conversely, siRNA-mediated p32 knockdown enhanced mitochondrial fragmentation accompanied by a loss of detectable levels of the mitochondrial fusion mediator proteins Mfn (mitofusin) 1 and Mfn2. More detailed ultrastructure analysis by transmission electron microscopy revealed aberrant mitochondrial structures with less and/or fragmented cristae and reduced mitochondrial matrix density as well as more punctate ER (endoplasmic reticulum) with noticeable dissociation of their ribosomes. The analysis of mitochondrial bioenergetics showed significantly reduced capacities in basal respiration and oxidative ATP turnover following p32 depletion. Furthermore, siRNA-mediated p32 knockdown resulted in differential stress-dependent effects on cell death, with enhanced cell death observed in the presence of hyperosmotic stress or cisplatin treatment, but decreased cell death in the presence of arsenite. Taken together, our studies highlight the critical contributions of the p32 protein to the morphology of mitochondria and ER under normal cellular conditions, as well as important roles of the p32 protein in cellular metabolism and various stress responses.
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324
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Horvath SE, Daum G. Lipids of mitochondria. Prog Lipid Res 2013; 52:590-614. [PMID: 24007978 DOI: 10.1016/j.plipres.2013.07.002] [Citation(s) in RCA: 606] [Impact Index Per Article: 55.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 07/31/2013] [Indexed: 01/06/2023]
Abstract
A unique organelle for studying membrane biochemistry is the mitochondrion whose functionality depends on a coordinated supply of proteins and lipids. Mitochondria are capable of synthesizing several lipids autonomously such as phosphatidylglycerol, cardiolipin and in part phosphatidylethanolamine, phosphatidic acid and CDP-diacylglycerol. Other mitochondrial membrane lipids such as phosphatidylcholine, phosphatidylserine, phosphatidylinositol, sterols and sphingolipids have to be imported. The mitochondrial lipid composition, the biosynthesis and the import of mitochondrial lipids as well as the regulation of these processes will be main issues of this review article. Furthermore, interactions of lipids and mitochondrial proteins which are highly important for various mitochondrial processes will be discussed. Malfunction or loss of enzymes involved in mitochondrial phospholipid biosynthesis lead to dysfunction of cell respiration, affect the assembly and stability of the mitochondrial protein import machinery and cause abnormal mitochondrial morphology or even lethality. Molecular aspects of these processes as well as diseases related to defects in the formation of mitochondrial membranes will be described.
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Affiliation(s)
- Susanne E Horvath
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria
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325
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Wideman JG, Lackey SWK, Srayko MA, Norton KA, Nargang FE. Analysis of mutations in Neurospora crassa ERMES components reveals specific functions related to β-barrel protein assembly and maintenance of mitochondrial morphology. PLoS One 2013; 8:e71837. [PMID: 23940790 PMCID: PMC3733929 DOI: 10.1371/journal.pone.0071837] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 07/03/2013] [Indexed: 11/22/2022] Open
Abstract
The endoplasmic reticulum mitochondria encounter structure (ERMES) tethers the er to mitochondria and contains four structural components: Mmm1, Mdm12, Mdm10, and Mmm2 (Mdm34). The Gem1 protein may play a role in regulating ERMES function. Saccharomyces cerevisiae and Neurospora crassa strains lacking any of Mmm1, Mdm12, or Mdm10 are known to show a variety of phenotypic defects including altered mitochondrial morphology and defects in the assembly of β-barrel proteins into the mitochondrial outer membrane. Here we examine ERMES complex components in N. crassa and show that Mmm1 is an ER membrane protein containing a Cys residue near its N-terminus that is conserved in the class Sordariomycetes. The residue occurs in the ER-lumen domain of the protein and is involved in the formation of disulphide bonds that give rise to Mmm1 dimers. Dimer formation is required for efficient assembly of Tom40 into the TOM complex. However, no effects are seen on porin assembly or mitochondrial morphology. This demonstrates a specificity of function and suggests a direct role for Mmm1 in Tom40 assembly. Mutation of a highly conserved region in the cytosolic domain of Mmm1 results in moderate defects in Tom40 and porin assembly, as well as a slight morphological phenotype. Previous reports have not examined the role of Mmm2 with respect to mitochondrial protein import and assembly. Here we show that absence of Mmm2 affects assembly of β-barrel proteins and that lack of any ERMES structural component results in defects in Tom22 assembly. Loss of N. crassa Gem1 has no effect on the assembly of these proteins but does affect mitochondrial morphology.
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Affiliation(s)
- Jeremy G. Wideman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - Martin A. Srayko
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Kacie A. Norton
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Frank E. Nargang
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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326
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Interorganellar membrane microdomains: dynamic platforms in the control of calcium signaling and apoptosis. Cells 2013; 2:574-90. [PMID: 24709798 PMCID: PMC3972666 DOI: 10.3390/cells2030574] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 07/23/2013] [Accepted: 07/26/2013] [Indexed: 11/16/2022] Open
Abstract
The dynamic interplay among intracellular organelles occurs at specific membrane tethering sites, where two organellar membranes come in close apposition but do not fuse. Such membrane microdomains allow for rapid and efficient interorganelle communication that contributes to the maintenance of cell physiology. Pathological conditions that interfere with the proper composition, number, and physical vicinity of the apposing membranes initiate a cascade of events resulting in cell death. Membrane contact sites have now been identified that tether the extensive network of the endoplasmic reticulum (ER) membranes with the mitochondria, the plasma membrane (PM), the Golgi and the endosomes/lysosomes. Thus far, the most extensively studied are the MAMs, or mitochondria associated ER membranes, and the ER-PM junctions that share functional properties and crosstalk to one another. Specific molecular components that define these microdomains have been shown to promote the interaction in trans between these intracellular compartments and the transfer or exchange of Ca2+ ions, lipids, and metabolic signaling molecules that determine the fate of the cell.
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327
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Szabadkai G, Rizzuto R. Kαλóς και Aγαθóς: how mitochondrial beauty translates into biological virtue. Curr Opin Cell Biol 2013; 25:477-82. [DOI: 10.1016/j.ceb.2013.03.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 03/28/2013] [Indexed: 11/27/2022]
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328
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Betz C, Stracka D, Prescianotto-Baschong C, Frieden M, Demaurex N, Hall MN. Feature Article: mTOR complex 2-Akt signaling at mitochondria-associated endoplasmic reticulum membranes (MAM) regulates mitochondrial physiology. Proc Natl Acad Sci U S A 2013; 110:12526-34. [PMID: 23852728 PMCID: PMC3732980 DOI: 10.1073/pnas.1302455110] [Citation(s) in RCA: 413] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The target of rapamycin (TOR) is a highly conserved protein kinase and a central controller of growth. Mammalian TOR complex 2 (mTORC2) regulates AGC kinase family members and is implicated in various disorders, including cancer and diabetes. Here we report that mTORC2 is localized to the endoplasmic reticulum (ER) subcompartment termed mitochondria-associated ER membrane (MAM). mTORC2 localization to MAM was growth factor-stimulated, and mTORC2 at MAM interacted with the IP3 receptor (IP3R)-Grp75-voltage-dependent anion-selective channel 1 ER-mitochondrial tethering complex. mTORC2 deficiency disrupted MAM, causing mitochondrial defects including increases in mitochondrial membrane potential, ATP production, and calcium uptake. mTORC2 controlled MAM integrity and mitochondrial function via Akt mediated phosphorylation of the MAM associated proteins IP3R, Hexokinase 2, and phosphofurin acidic cluster sorting protein 2. Thus, mTORC2 is at the core of a MAM signaling hub that controls growth and metabolism.
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Affiliation(s)
- Charles Betz
- Growth and Development, Biozentrum, University of Basel, CH-4056 Basel, Switzerland; and
| | - Daniele Stracka
- Growth and Development, Biozentrum, University of Basel, CH-4056 Basel, Switzerland; and
| | | | - Maud Frieden
- Department of Cell Physiology and Metabolism, University of Geneva, 1211 Geneva 4, Switzerland
| | - Nicolas Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, 1211 Geneva 4, Switzerland
| | - Michael N. Hall
- Growth and Development, Biozentrum, University of Basel, CH-4056 Basel, Switzerland; and
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329
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Crottès D, Guizouarn H, Martin P, Borgese F, Soriani O. The sigma-1 receptor: a regulator of cancer cell electrical plasticity? Front Physiol 2013; 4:175. [PMID: 23882221 PMCID: PMC3712323 DOI: 10.3389/fphys.2013.00175] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 06/21/2013] [Indexed: 12/18/2022] Open
Abstract
Originally mistaken as an opioid receptor, the sigma-1 receptor (Sig1R) is a ubiquitous membrane protein that has been involved in many cellular processes. While the precise function of Sig1R has long remained mysterious, recent studies have shed light on its role and the molecular mechanisms triggered. Sig1R is in fact a stress-activated chaperone mainly associated with the ER-mitochondria interface that can regulate cell survival through the control of calcium homeostasis. Sig1R functionally regulates ion channels belonging to various molecular families and it has thus been involved in neuronal plasticity and central nervous system diseases. Interestingly, Sig1R is frequently expressed in tumors but its function in cancer has not been yet clarified. In this review, we discuss the current understanding of Sig1R. We suggest herein that Sig1R shapes cancer cell electrical signature upon environmental conditions. Thus, Sig1R may be used as a novel therapeutic target to specifically abrogate pro-invasive functions of ion channels in cancer tissue.
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Affiliation(s)
- David Crottès
- Université de Nice, UMR 7277 Nice, France ; Institut de Biologie de Valrose, CNRS UMR 7277, INSERM U1091, Université de Nice Nice, France
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330
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Lynes EM, Raturi A, Shenkman M, Ortiz Sandoval C, Yap MC, Wu J, Janowicz A, Myhill N, Benson MD, Campbell RE, Berthiaume LG, Lederkremer GZ, Simmen T. Palmitoylation is the switch that assigns calnexin to quality control or ER Ca2+ signaling. J Cell Sci 2013; 126:3893-903. [PMID: 23843619 DOI: 10.1242/jcs.125856] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The palmitoylation of calnexin serves to enrich calnexin on the mitochondria-associated membrane (MAM). Given a lack of information on the significance of this finding, we have investigated how this endoplasmic reticulum (ER)-internal sorting signal affects the functions of calnexin. Our results demonstrate that palmitoylated calnexin interacts with sarcoendoplasmic reticulum (SR) Ca(2+) transport ATPase (SERCA) 2b and that this interaction determines ER Ca(2+) content and the regulation of ER-mitochondria Ca(2+) crosstalk. In contrast, non-palmitoylated calnexin interacts with the oxidoreductase ERp57 and performs its well-known function in quality control. Interestingly, our results also show that calnexin palmitoylation is an ER-stress-dependent mechanism. Following a short-term ER stress, calnexin quickly becomes less palmitoylated, which shifts its function from the regulation of Ca(2+) signaling towards chaperoning and quality control of known substrates. These changes also correlate with a preferential distribution of calnexin to the MAM under resting conditions, or the rough ER and ER quality control compartment (ERQC) following ER stress. Our results have therefore identified the switch that assigns calnexin either to Ca(2+) signaling or to protein chaperoning.
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Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
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331
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Hoffmann M. Enhanced uncoupling of the mitochondrial respiratory chain as a potential source for amyotrophic lateral sclerosis. Front Neurol 2013; 4:86. [PMID: 23840192 PMCID: PMC3699730 DOI: 10.3389/fneur.2013.00086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 06/19/2013] [Indexed: 12/11/2022] Open
Affiliation(s)
- Michael Hoffmann
- Department of General Pediatrics, University Children's Hospital, Heinrich Heine University Dusseldorf, Germany
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332
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Wideman JG, Gawryluk RM, Gray MW, Dacks JB. The Ancient and Widespread Nature of the ER–Mitochondria Encounter Structure. Mol Biol Evol 2013; 30:2044-9. [DOI: 10.1093/molbev/mst120] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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333
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Abstract
In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. This article provides an overview of key aspects of mitochondrial biology in endothelial cells, including subcellular location, biogenesis, dynamics, autophagy, reactive oxygen species production and signaling, calcium homeostasis, regulated cell death, and heme biosynthesis. In each section, we introduce key concepts and then review studies showing the importance of that mechanism to endothelial control of vasomotor tone, angiogenesis, and/or inflammatory activation. We particularly highlight the small number of clinical and translational studies that have investigated each mechanism in human subjects. Finally, we review interventions that target different aspects of mitochondrial function and their effects on endothelial function. The ultimate goal of such research is the identification of new approaches for therapy. The reviewed studies make it clear that mitochondria are important in endothelial physiology and pathophysiology. A great deal of work will be needed, however, before mitochondria-directed therapies are available for the prevention and treatment of cardiovascular disease.
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Affiliation(s)
- Matthew A Kluge
- Evans Department of Medicine, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA
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334
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Crosstalk between Endoplasmic Reticulum Stress and Protein Misfolding in Neurodegenerative Diseases. ACTA ACUST UNITED AC 2013. [DOI: 10.1155/2013/256404] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Under physiological conditions, the endoplasmic reticulum (ER) is a central subcellular compartment for protein quality control in the secretory pathway that prevents protein misfolding and aggregation. Instrumental in protein quality control in the ER is the unfolded protein response (UPR), which is activated upon ER stress to reestablish homeostasis through a sophisticated transcriptionally and translationally regulated signaling network. However, this response can lead to apoptosis if the stress cannot be alleviated. The presence of abnormal protein aggregates containing specific misfolded proteins is recognized as the basis of numerous human conformational disorders, including neurodegenerative diseases. Here, I will highlight the overwhelming evidence that the presence of specific aberrant proteins in Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), prion diseases, and Amyotrophic Lateral Sclerosis (ALS) is intimately associated with perturbations in the ER protein quality control machinery that become incompetent to restore protein homeostasis and shift adaptive programs toward the induction of apoptotic signaling to eliminate irreversibly damaged neurons. Increasing our understanding about the deadly crosstalk between ER dysfunction and protein misfolding in these neurodegenerative diseases may stimulate the development of novel therapeutic strategies able to support neuronal survival and ameliorate disease progression.
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335
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Hepatitis C virus-induced mitochondrial dysfunctions. Viruses 2013; 5:954-80. [PMID: 23518579 PMCID: PMC3705306 DOI: 10.3390/v5030954] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 03/15/2013] [Accepted: 03/20/2013] [Indexed: 12/15/2022] Open
Abstract
Chronic hepatitis C is characterized by metabolic disorders and a microenvironment in the liver dominated by oxidative stress, inflammation and regeneration processes that lead in the long term to hepatocellular carcinoma. Many lines of evidence suggest that mitochondrial dysfunctions, including modification of metabolic fluxes, generation and elimination of oxidative stress, Ca2+ signaling and apoptosis, play a central role in these processes. However, how these dysfunctions are induced by the virus and whether they play a role in disease progression and neoplastic transformation remains to be determined. Most in vitro studies performed so far have shown that several of the hepatitis C virus (HCV) proteins localize to mitochondria, but the consequences of these interactions on mitochondrial functions remain contradictory, probably due to the use of artificial expression and replication systems. In vivo studies are hampered by the fact that innate and adaptive immune responses will overlay mitochondrial dysfunctions induced directly in the hepatocyte by HCV. Thus, the molecular aspects underlying HCV-induced mitochondrial dysfunctions and their roles in viral replication and the associated pathology need yet to be confirmed in the context of productively replicating virus and physiologically relevant in vitro and in vivo model systems.
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336
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Annunziata I, Patterson A, d'Azzo A. Mitochondria-associated ER membranes (MAMs) and glycosphingolipid enriched microdomains (GEMs): isolation from mouse brain. J Vis Exp 2013:e50215. [PMID: 23486347 DOI: 10.3791/50215] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Intracellular organelles are highly dynamic structures with varying shape and composition, which are subjected to cell-specific intrinsic and extrinsic cues. Their membranes are often juxtaposed at defined contact sites, which become hubs for the exchange of signaling molecules and membrane components(1,2,3,4). The inter-organellar membrane microdomains that are formed between the endoplasmic reticulum (ER) and the mitochondria at the opening of the IP3-sensitive Ca(2+) channel are known as the mitochondria associated-ER membranes or MAMs(4,5,6). The protein/lipid composition and biochemical properties of these membrane contact sites have been extensively studied particularly in relation to their role in regulating intracellular Ca(2+) (4,5,6). The ER serves as the primary store of intracellular Ca(2+), and in this capacity regulates a myriad of cellular processes downstream of Ca(2+) signaling, including post-translational protein folding and protein maturation (7). Mitochondria, on the other hand, maintain Ca(2+) homeostasis, by buffering cytosolic Ca(2+) concentration thereby preventing the initiation of apoptotic pathways downstream of Ca(2+) unbalance(4,8). The dynamic nature of the MAMs makes them ideal sites to dissect basic cellular mechanisms, including Ca(2+) signaling and regulation of mitochondrial Ca(2+) concentration, lipid biosynthesis and transport, energy metabolism and cell survival (4,9,10,11,12). Several protocols have been described for the purification of these microdomains from liver tissue and cultured cells(13,14). Taking previously published methods into account, we have adapted a protocol for the isolation of mitochondria and MAMs from the adult mouse brain. To this procedure we have added an extra purification step, namely a Triton X100 extraction, which enables the isolation of the glycosphingolipid enriched microdomain (GEM) fraction of the MAMs. These GEM preparations share several protein components with caveolae and lipid rafts, derived from the plasma membrane or other intracellular membranes, and are proposed to function as gathering points for the clustering of receptor proteins and for protein-protein interactions(4,15).
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Affiliation(s)
- Ida Annunziata
- Department of Genetics, St Jude Children's Research Hospital, USA
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337
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Baba T, Yamamoto A, Tagaya M, Tani K. A lysophospholipid acyltransferase antagonist, CI-976, creates novel membrane tubules marked by intracellular phospholipase A1 KIAA0725p. Mol Cell Biochem 2013; 376:151-61. [PMID: 23378048 DOI: 10.1007/s11010-013-1563-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 01/18/2013] [Indexed: 01/30/2023]
Abstract
CI-976 is a lysophospholipid acyltransferase antagonist that is known to affect secretory and endocytic membrane-trafficking pathways likely by increasing the lysophospholipid content in membranes. Our previous study suggested that lysophospholipids formed through the action of an intracellular phospholipase A(1), KIAA0725p (also known as DDHD2 and iPLA(1)γ), may be important for the association of this enzyme with membranes. In this study, we examined the effect of CI-976 on the membrane association of KIAA0725p. While in HeLa cells KIAA0725p is localized in the Golgi and cytosol, in mouse embryonic fibroblasts (MEFs), it was found to be principally localized in the cytosol with some on post-endoplasmic reticulum compartments including the cis-Golgi. Treatment of MEFs with CI-976 induced the redistribution of KIAA0725p to membrane tubules, which were in vicinity to fragmented mitochondria. These tubules were not decorated with canonical organelle markers including Golgi proteins. A human KIAA0725p mutant, which exhibits decreased membrane-binding ability, was also redistributed to membrane structures upon CI-976 treatment. Our data suggest that the association of KIAA0725p with membranes is regulated by lipid metabolism, and that CI-976 may create unique membrane structures that can be marked by KIAA0725p.
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Affiliation(s)
- Takashi Baba
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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338
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Poston CN, Krishnan SC, Bazemore-Walker CR. In-depth proteomic analysis of mammalian mitochondria-associated membranes (MAM). J Proteomics 2013; 79:219-30. [DOI: 10.1016/j.jprot.2012.12.018] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 12/12/2012] [Accepted: 12/26/2012] [Indexed: 12/25/2022]
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339
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Landau G, Kodali VK, Malhotra JD, Kaufman RJ. Detection of Oxidative Damage in Response to Protein Misfolding in the Endoplasmic Reticulum. Methods Enzymol 2013; 526:231-50. [DOI: 10.1016/b978-0-12-405883-5.00014-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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340
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Abstract
Cell biology and microbiology are some of the oldest areas of scientific inquiry. Despite the depth of knowledge we now have in these respective fields, much remains unclear about how microorganisms interact with host intracellular organelles. Perhaps nowhere is this statement more accurate than in the role of peroxisomes in microbial infections. Peroxisomes were one of the first organelles discovered by Christian De Duve over 50 years ago (de Duve Ann N Y Acad Sci 386:1-4, 1982). These organelles are ubiquitously found in eukaryotic cells, where they serve several well-defined functions in lipid and oxygen homeostasis (Waterham and Wanders Biochim Biophys Acta 1822:1325, 2012). This chapter will discuss the emerging evidence that indicates that in addition to their functions in cellular metabolism, peroxisomes play an important role in viral infections.
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Affiliation(s)
- Charlotte Odendall
- Harvard Medical School and Division of Gastroenterology, Boston Children's Hospital, Boston, MA, 02115, USA
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341
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Bhandary B, Marahatta A, Kim HR, Chae HJ. An involvement of oxidative stress in endoplasmic reticulum stress and its associated diseases. Int J Mol Sci 2012; 14:434-56. [PMID: 23263672 PMCID: PMC3565273 DOI: 10.3390/ijms14010434] [Citation(s) in RCA: 287] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/01/2012] [Accepted: 12/13/2012] [Indexed: 12/17/2022] Open
Abstract
The endoplasmic reticulum (ER) is the major site of calcium storage and protein folding. It has a unique oxidizing-folding environment due to the predominant disulfide bond formation during the process of protein folding. Alterations in the oxidative environment of the ER and also intra-ER Ca2+ cause the production of ER stress-induced reactive oxygen species (ROS). Protein disulfide isomerases, endoplasmic reticulum oxidoreductin-1, reduced glutathione and mitochondrial electron transport chain proteins also play crucial roles in ER stress-induced production of ROS. In this article, we discuss ER stress-associated ROS and related diseases, and the current understanding of the signaling transduction involved in ER stress.
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Affiliation(s)
- Bidur Bhandary
- Department of Pharmacology, School of Medicine, Chonbuk National Univeristy, Jeonju 561-180, South Korea; E-Mails: (B.B.); (A.M.)
| | - Anu Marahatta
- Department of Pharmacology, School of Medicine, Chonbuk National Univeristy, Jeonju 561-180, South Korea; E-Mails: (B.B.); (A.M.)
| | - Hyung-Ryong Kim
- Department of Dental Pharmacology, Dental School, Wonkwang University, Iksan 570-749, South Korea
- Authors to whom correspondence should be addressed; E-Mails: (H.-R.K.); (H.-J.C.); Tel.: +82-63-850-6640 (H.-R.K.); +82-63-270-3092 (H.-J.C.); Fax: +82-63-854-0285 (H.-R.K.); +82-63-275-8799 (H.-J.C.)
| | - Han-Jung Chae
- Department of Pharmacology, School of Medicine, Chonbuk National Univeristy, Jeonju 561-180, South Korea; E-Mails: (B.B.); (A.M.)
- Authors to whom correspondence should be addressed; E-Mails: (H.-R.K.); (H.-J.C.); Tel.: +82-63-850-6640 (H.-R.K.); +82-63-270-3092 (H.-J.C.); Fax: +82-63-854-0285 (H.-R.K.); +82-63-275-8799 (H.-J.C.)
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342
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Alford SC, Ding Y, Simmen T, Campbell RE. Dimerization-dependent green and yellow fluorescent proteins. ACS Synth Biol 2012; 1:569-75. [PMID: 23656278 DOI: 10.1021/sb300050j] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Dimerization-dependent fluorescent proteins (ddFP) are a recently introduced class of genetically encoded reporters that can be used for the detection of protein interactions in live cells. The progenitor of this class of tools was a red fluorescent ddFP (ddRFP) derived from a homodimeric variant of Discosoma red fluorescent protein. Here, we describe the engineering and application of an expanded palette of ddFPs, which includes green (ddGFP) and yellow (ddYFP) variants. These optimized variants offer several advantages relative to ddRFP including increased in vitro contrast and brightness for ddGFP and increased brightness and a lowered pK a for ddYFP. We demonstrate that both variants are useful as biosensors for protease activity in live cells. Using the ddGFP tool, we generated a highly effective indicator of endomembrane proximity that can be used to image the mitochondria-associated membrane (MAM) interface of endoplasmic reticulum (ER) and mitochondria.
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Affiliation(s)
- Spencer C. Alford
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Yidan Ding
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Thomas Simmen
- Department of Cell Biology,
Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
| | - Robert E. Campbell
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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343
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344
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Doroudgar S, Glembotski CC. New concepts of endoplasmic reticulum function in the heart: programmed to conserve. J Mol Cell Cardiol 2012; 55:85-91. [PMID: 23085588 DOI: 10.1016/j.yjmcc.2012.10.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 10/07/2012] [Accepted: 10/11/2012] [Indexed: 11/16/2022]
Abstract
Secreted and membrane proteins play critical roles in myocardial health and disease. Studies in non-myocytes have shown that the peri-nuclear ER is the site for synthesis, folding, and quality control of most secreted and membrane proteins, as well as a nexus of a signal transduction system, called the ER stress response, which informs the cell about the status of ER protein folding. Moreover, the dynamic physical and functional association of the ER with mitochondria is a key site responsible for integrating ER function and mitochondrial metabolism, but is only just beginning to be understood in the myocardium. Although a great deal is known about roles played by the sarcoplasmic reticulum (SR) in contractile calcium handling in the heart, little is known about the relative locations and functions of the peri-nuclear ER and the SR in terms of secreted and membrane protein synthesis and folding. In this review we will explore the current state of knowledge of the location of secreted and membrane protein synthesis, folding, and quality control machinery in cardiac myocytes, as well as our understanding of the functional consequences of ER stress and the unfolded protein response in the heart in terms of protein synthesis, cell growth, and metabolic regulation. This article is part of a Special Issue entitled "Focus on Cardiac Metabolism".
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Affiliation(s)
- Shirin Doroudgar
- San Diego State University Heart Institute and The Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
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