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Smolders S, Van Broeckhoven C. Genetic perspective on the synergistic connection between vesicular transport, lysosomal and mitochondrial pathways associated with Parkinson's disease pathogenesis. Acta Neuropathol Commun 2020; 8:63. [PMID: 32375870 PMCID: PMC7201634 DOI: 10.1186/s40478-020-00935-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 04/21/2020] [Indexed: 12/13/2022] Open
Abstract
Parkinson's disease (PD) and atypical parkinsonian syndromes (APS) are symptomatically characterized by parkinsonism, with the latter presenting additionally a distinctive range of atypical features. Although the majority of patients with PD and APS appear to be sporadic, genetic causes of several rare monogenic disease variants were identified. The knowledge acquired from these genetic factors indicated that defects in vesicular transport pathways, endo-lysosomal dysfunction, impaired autophagy-lysosomal protein and organelle degradation pathways, α-synuclein aggregation and mitochondrial dysfunction play key roles in PD pathogenesis. Moreover, membrane dynamics are increasingly recognized as a key player in the disease pathogenesis due lipid homeostasis alterations, associated with lysosomal dysfunction, caused by mutations in several PD and APS genes. The importance of lysosomal dysfunction and lipid homeostasis is strengthened by both genetic discoveries and clinical epidemiology of the association between parkinsonism and lysosomal storage disorders (LSDs), caused by the disruption of lysosomal biogenesis or function. A synergistic coordination between vesicular trafficking, lysosomal and mitochondria defects exist whereby mutations in PD and APS genes encoding proteins primarily involved one PD pathway are frequently associated with defects in other PD pathways as a secondary effect. Moreover, accumulating clinical and genetic observations suggest more complex inheritance patters of familial PD exist, including oligogenic and polygenic inheritance of genes in the same or interconnected PD pathways, further strengthening their synergistic connection.Here, we provide a comprehensive overview of PD and APS genes with functions in vesicular transport, lysosomal and mitochondrial pathways, and highlight functional and genetic evidence of the synergistic connection between these PD associated pathways.
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Affiliation(s)
- Stefanie Smolders
- Neurodegenerative Brain Diseases Group, VIB Center for Molecular Neurology, University of Antwerp - CDE, Universiteitsplein 1, 2610, Antwerpen, Belgium
- Biomedical Sciences, University of Antwerp, Antwerpen, Belgium
| | - Christine Van Broeckhoven
- Neurodegenerative Brain Diseases Group, VIB Center for Molecular Neurology, University of Antwerp - CDE, Universiteitsplein 1, 2610, Antwerpen, Belgium.
- Biomedical Sciences, University of Antwerp, Antwerpen, Belgium.
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Abstract
Cells are complex machines with tremendous potential for applications in medicine and biotechnology. Although much effort has been devoted to engineering the metabolic, genetic, and signaling pathways of cells, methods for systematically engineering the physical structure of cells are less developed. Here we consider how coarse-grained models for cellular geometry at the organelle level can be used to build computer-aided design (CAD) tools for cellular structure.
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Affiliation(s)
- Simone Bianco
- Center for Cellular Construction, San Francisco, CA, United States of America. IBM Almaden Research Center, San Jose, CA, United States of America
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Öztürk Z, O’Kane CJ, Pérez-Moreno JJ. Axonal Endoplasmic Reticulum Dynamics and Its Roles in Neurodegeneration. Front Neurosci 2020; 14:48. [PMID: 32116502 PMCID: PMC7025499 DOI: 10.3389/fnins.2020.00048] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/13/2020] [Indexed: 12/13/2022] Open
Abstract
The physical continuity of axons over long cellular distances poses challenges for their maintenance. One organelle that faces this challenge is endoplasmic reticulum (ER); unlike other intracellular organelles, this forms a physically continuous network throughout the cell, with a single membrane and a single lumen. In axons, ER is mainly smooth, forming a tubular network with occasional sheets or cisternae and low amounts of rough ER. It has many potential roles: lipid biosynthesis, glucose homeostasis, a Ca2+ store, protein export, and contacting and regulating other organelles. This tubular network structure is determined by ER-shaping proteins, mutations in some of which are causative for neurodegenerative disorders such as hereditary spastic paraplegia (HSP). While axonal ER shares many features with the tubular ER network in other contexts, these features must be adapted to the long and narrow dimensions of axons. ER appears to be physically continuous throughout axons, over distances that are enormous on a subcellular scale. It is therefore a potential channel for long-distance or regional communication within neurons, independent of action potentials or physical transport of cargos, but involving its physiological roles such as Ca2+ or organelle homeostasis. Despite its apparent stability, axonal ER is highly dynamic, showing features like anterograde and retrograde transport, potentially reflecting continuous fusion and breakage of the network. Here we discuss the transport processes that must contribute to this dynamic behavior of ER. We also discuss the model that these processes underpin a homeostatic process that ensures both enough ER to maintain continuity of the network and repair breaks in it, but not too much ER that might disrupt local cellular physiology. Finally, we discuss how failure of ER organization in axons could lead to axon degenerative diseases, and how a requirement for ER continuity could make distal axons most susceptible to degeneration in conditions that disrupt ER continuity.
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Affiliation(s)
| | - Cahir J. O’Kane
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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Martínez J, Marmisolle I, Tarallo D, Quijano C. Mitochondrial Bioenergetics and Dynamics in Secretion Processes. Front Endocrinol (Lausanne) 2020; 11:319. [PMID: 32528413 PMCID: PMC7256191 DOI: 10.3389/fendo.2020.00319] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 04/27/2020] [Indexed: 12/12/2022] Open
Abstract
Secretion is an energy consuming process that plays a relevant role in cell communication and adaptation to the environment. Among others, endocrine cells producing hormones, immune cells producing cytokines or antibodies, neurons releasing neurotransmitters at synapsis, and more recently acknowledged, senescent cells synthesizing and secreting multiple cytokines, growth factors and proteases, require energy to successfully accomplish the different stages of the secretion process. Calcium ions (Ca2+) act as second messengers regulating secretion in many of these cases. In this setting, mitochondria appear as key players providing ATP by oxidative phosphorylation, buffering Ca2+ concentrations and acting as structural platforms. These tasks also require the concerted actions of the mitochondrial dynamics machinery. These proteins mediate mitochondrial fusion and fission, and are also required for transport and tethering of mitochondria to cellular organelles where the different steps of the secretion process take place. Herein we present a brief overview of mitochondrial energy metabolism, mitochondrial dynamics, and the different steps of the secretion processes, along with evidence of the interaction between these pathways. We also analyze the role of mitochondria in secretion by different cell types in physiological and pathological settings.
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55
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Nguyen TMT, Kim J, Doan TT, Lee MW, Lee M. APEX Proximity Labeling as a Versatile Tool for Biological Research. Biochemistry 2019; 59:260-269. [PMID: 31718172 DOI: 10.1021/acs.biochem.9b00791] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Most proteins are specifically localized in membrane-encapsulated organelles or non-membrane-bound compartments. The subcellular localization of proteins facilitates their functions and integration into functional networks; therefore, protein localization is tightly regulated in diverse biological contexts. However, protein localization has been mainly analyzed through immunohistochemistry or the fractionation of subcellular compartments, each of which has major drawbacks. Immunohistochemistry can examine only a handful of proteins at a time, and fractionation inevitably relies on the lysis of cells, which disrupts native cellular conditions. Recently, an engineered ascorbate peroxidase (APEX)-based proximity labeling technique combined with mass spectrometry was developed, which allows for temporally and spatially resolved proteomic mapping. In the presence of H2O2, engineered APEX oxidizes biotin-phenols into biotin-phenoxyl radicals, and these short-lived radicals biotinylate electron-rich amino acids within a radius of several nanometers. Biotinylated proteins are subsequently enriched by streptavidin and identified by mass spectrometry. This permits the sensitive and efficient labeling of proximal proteins around locally expressed APEX. Through the targeted expression of APEX in the subcellular region of interest, proteomic profiling of submitochondrial spaces, the outer mitochondrial membrane, the endoplasmic reticulum (ER)-mitochondrial contact, and the ER membrane has been performed. Furthermore, this method has been modified to define interaction networks in the vicinity of target proteins and has also been applied to analyze the spatial transcriptome. In this Perspective, we provide an outline of this newly developed technique and discuss its potential applications to address diverse biological questions.
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Affiliation(s)
- Thanh My Thi Nguyen
- Soonchunhyang Institute of Medi-bio Science , Soonchunhyang University , Cheonan-si , Chungcheongnam-do 31151 , Republic of Korea
| | - Junhyung Kim
- Soonchunhyang Institute of Medi-bio Science , Soonchunhyang University , Cheonan-si , Chungcheongnam-do 31151 , Republic of Korea
| | - Thi Tram Doan
- Soonchunhyang Institute of Medi-bio Science , Soonchunhyang University , Cheonan-si , Chungcheongnam-do 31151 , Republic of Korea
| | - Min-Woo Lee
- Soonchunhyang Institute of Medi-bio Science , Soonchunhyang University , Cheonan-si , Chungcheongnam-do 31151 , Republic of Korea
| | - Mihye Lee
- Soonchunhyang Institute of Medi-bio Science , Soonchunhyang University , Cheonan-si , Chungcheongnam-do 31151 , Republic of Korea
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Abstract
In the body, extracellular stimuli produce inositol 1,4,5-trisphosphate (IP3), an intracellular chemical signal that binds to the IP3 receptor (IP3R) to release calcium ions (Ca2+) from the endoplasmic reticulum. In the past 40 years, the wide-ranging functions mediated by IP3R and its genetic defects causing a variety of disorders have been unveiled. Recent cryo-electron microscopy and X-ray crystallography have resolved IP3R structures and begun to integrate with concurrent functional studies, which can explicate IP3-dependent opening of Ca2+-conducting gates placed ∼90 Å away from IP3-binding sites and its regulation by Ca2+. This review highlights recent research progress on the IP3R structure and function. We also propose how protein plasticity within IP3R, which involves allosteric gating and assembly transformations accompanied by rapid and chronic structural changes, would enable it to regulate diverse functions at cellular microdomains in pathophysiological states.
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Affiliation(s)
- Kozo Hamada
- Laboratory of Cell Calcium Signaling, Shanghai Institute for Advanced Immunochemical Studies (SIAIS), ShanghaiTech University, Shanghai, 201210, China; ,
| | - Katsuhiko Mikoshiba
- Laboratory of Cell Calcium Signaling, Shanghai Institute for Advanced Immunochemical Studies (SIAIS), ShanghaiTech University, Shanghai, 201210, China; ,
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Naito T, Ercan B, Krshnan L, Triebl A, Koh DHZ, Wei FY, Tomizawa K, Torta FT, Wenk MR, Saheki Y. Movement of accessible plasma membrane cholesterol by the GRAMD1 lipid transfer protein complex. eLife 2019; 8:51401. [PMID: 31724953 PMCID: PMC6905856 DOI: 10.7554/elife.51401] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 11/13/2019] [Indexed: 12/18/2022] Open
Abstract
Cholesterol is a major structural component of the plasma membrane (PM). The majority of PM cholesterol forms complexes with other PM lipids, making it inaccessible for intracellular transport. Transition of PM cholesterol between accessible and inaccessible pools maintains cellular homeostasis, but how cells monitor the accessibility of PM cholesterol remains unclear. We show that endoplasmic reticulum (ER)-anchored lipid transfer proteins, the GRAMD1s, sense and transport accessible PM cholesterol to the ER. GRAMD1s bind to one another and populate ER-PM contacts by sensing a transient expansion of the accessible pool of PM cholesterol via their GRAM domains. They then facilitate the transport of this cholesterol via their StART-like domains. Cells that lack all three GRAMD1s exhibit striking expansion of the accessible pool of PM cholesterol as a result of less efficient PM to ER transport of accessible cholesterol. Thus, GRAMD1s facilitate the movement of accessible PM cholesterol to the ER in order to counteract an acute increase of PM cholesterol, thereby activating non-vesicular cholesterol transport. The human body contains trillions of cells. At the outer edge of each cell is the plasma membrane, which protects the cell from the external environment. This membrane is mostly made of fatty molecules known as lipids and about half of these lipids are specifically cholesterol. Human cells can either take up cholesterol that were obtained via the diet or produce it within a compartment of the cell called the endoplasmic reticulum. Cells need to monitor the cholesterol levels in both the endoplasmic reticulum and the plasma membrane in order to regulate the uptake or production of this lipid. For example, if there is too much of cholesterol in the plasma membrane, then the cell transports some to the endoplasmic reticulum to tell it to shut down cholesterol production. However, how these different areas of the cell communicate with each other, and transport cholesterol, has remained unclear. Naito et al. set out to look for key regulators of cholesterol transport and identified a group of endoplasmic reticulum proteins called GRAMD1 proteins. Cholesterol in the plasma membrane is either accessible or inaccessible, meaning it either can or cannot be moved back into the cell. The GRAMD1 proteins sense accessible cholesterol, and experiments with human cells grown in the laboratory showed that, specifically, the GRAMD1 proteins work together in a complex to sense accessible cholesterol at or near the plasma membrane. One particular part of the protein senses when the amount of accessible cholesterol reaches a certain level at the plasma membrane; when this threshold is reached, the complex flips a switch to start the transport of cholesterol to the endoplasmic reticulum and tell it to shut down cholesterol production. This coupling of sensing and transporting lipids by one protein complex also helps maintain the right ratio of accessible and inaccessible cholesterol in the plasma membrane to prevent cells from activating unwanted cell-signaling events. Getting rid of the GRAMD1 proteins in cells, or removing sensing part of these proteins, leads to inefficient transport of cholesterol. A better understanding of how GRAMD1 proteins sense the accessibility of cholesterol could potentially help identify new approaches to control cholesterol transport inside cells. This may in turn eventually lead to new treatments that counteract the defects in cholesterol metabolism seen in some forms of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease.
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Affiliation(s)
- Tomoki Naito
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Bilge Ercan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Logesvaran Krshnan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Alexander Triebl
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Fan-Yan Wei
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazuhito Tomizawa
- Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Federico Tesio Torta
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, Japan
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58
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Mitochondrial interaction with the endosomal compartment in endocytosis and mitochondrial transfer. Mitochondrion 2019; 49:284-288. [DOI: 10.1016/j.mito.2019.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 05/09/2019] [Accepted: 05/13/2019] [Indexed: 12/16/2022]
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59
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Jirsová D, Füssy Z, Richtová J, Gruber A, Oborník M. Morphology, Ultrastructure, and Mitochondrial Genome of the Marine Non-Photosynthetic Bicosoecid Cafileria marina Gen. et sp. nov. Microorganisms 2019; 7:microorganisms7080240. [PMID: 31387253 PMCID: PMC6723347 DOI: 10.3390/microorganisms7080240] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 07/25/2019] [Accepted: 08/01/2019] [Indexed: 12/16/2022] Open
Abstract
In this paper, we describe a novel bacteriophagous biflagellate, Cafileria marina with two smooth flagellae, isolated from material collected from a rock surface in the Kvernesfjorden (Norway). This flagellate was characterized by scanning and transmission electron microscopy, fluorescence, and light microscopy. The sequence of the small subunit ribosomal RNA gene (18S) was used as a molecular marker for determining the phylogenetic position of this organism. Apart from the nuclear ribosomal gene, the whole mitochondrial genome was sequenced, assembled, and annotated. Morphological observations show that the newly described flagellate shares key ultrastructural characters with representatives of the family Bicosoecida (Heterokonta). Intriguingly, mitochondria of C. marina frequently associate with its nucleus through an electron-dense disc at the boundary of the two compartments. The function of this association remains unclear. Phylogenetic analyses corroborate the morphological data and place C. marina with other sequence data of representatives from the family Bicosoecida. We describe C. marina as a new species from a new genus in this family.
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Affiliation(s)
- Dagmar Jirsová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic
| | - Zoltán Füssy
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic
| | - Jitka Richtová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic
| | - Ansgar Gruber
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic
| | - Miroslav Oborník
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Branišovská 31, 370 05 České Budějovice, Czech Republic.
- Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic.
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60
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Zhang X, Gibhardt CS, Will T, Stanisz H, Körbel C, Mitkovski M, Stejerean I, Cappello S, Pacheu‐Grau D, Dudek J, Tahbaz N, Mina L, Simmen T, Laschke MW, Menger MD, Schön MP, Helms V, Niemeyer BA, Rehling P, Vultur A, Bogeski I. Redox signals at the ER-mitochondria interface control melanoma progression. EMBO J 2019; 38:e100871. [PMID: 31304984 PMCID: PMC6669928 DOI: 10.15252/embj.2018100871] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 05/21/2019] [Accepted: 05/23/2019] [Indexed: 12/20/2022] Open
Abstract
Reactive oxygen species (ROS) are emerging as important regulators of cancer growth and metastatic spread. However, how cells integrate redox signals to affect cancer progression is not fully understood. Mitochondria are cellular redox hubs, which are highly regulated by interactions with neighboring organelles. Here, we investigated how ROS at the endoplasmic reticulum (ER)-mitochondria interface are generated and translated to affect melanoma outcome. We show that TMX1 and TMX3 oxidoreductases, which promote ER-mitochondria communication, are upregulated in melanoma cells and patient samples. TMX knockdown altered mitochondrial organization, enhanced bioenergetics, and elevated mitochondrial- and NOX4-derived ROS. The TMX-knockdown-induced oxidative stress suppressed melanoma proliferation, migration, and xenograft tumor growth by inhibiting NFAT1. Furthermore, we identified NFAT1-positive and NFAT1-negative melanoma subgroups, wherein NFAT1 expression correlates with melanoma stage and metastatic potential. Integrative bioinformatics revealed that genes coding for mitochondrial- and redox-related proteins are under NFAT1 control and indicated that TMX1, TMX3, and NFAT1 are associated with poor disease outcome. Our study unravels a novel redox-controlled ER-mitochondria-NFAT1 signaling loop that regulates melanoma pathobiology and provides biomarkers indicative of aggressive disease.
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Affiliation(s)
- Xin Zhang
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
- BiophysicsCIPMMSaarland UniversityHomburgGermany
| | - Christine S Gibhardt
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Thorsten Will
- Center for BioinformaticsSaarland UniversitySaarbrückenGermany
| | - Hedwig Stanisz
- Department of Dermatology, Venereology and AllergologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Christina Körbel
- Institute for Clinical and Experimental SurgerySaarland UniversityHomburgGermany
| | - Miso Mitkovski
- Light Microscopy FacilityMax Planck Institute for Experimental MedicineGöttingenGermany
| | - Ioana Stejerean
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Sabrina Cappello
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - David Pacheu‐Grau
- Department of Cellular BiochemistryUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Jan Dudek
- Department of Cellular BiochemistryUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Nasser Tahbaz
- Department of Cell BiologyUniversity of AlbertaEdmontonABCanada
| | - Lucas Mina
- Department of Cell BiologyUniversity of AlbertaEdmontonABCanada
| | - Thomas Simmen
- Department of Cell BiologyUniversity of AlbertaEdmontonABCanada
| | - Matthias W Laschke
- Institute for Clinical and Experimental SurgerySaarland UniversityHomburgGermany
| | - Michael D Menger
- Institute for Clinical and Experimental SurgerySaarland UniversityHomburgGermany
| | - Michael P Schön
- Department of Dermatology, Venereology and AllergologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Volkhard Helms
- Center for BioinformaticsSaarland UniversitySaarbrückenGermany
| | | | - Peter Rehling
- Department of Cellular BiochemistryUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
- Max Planck Institute for Biophysical ChemistryGöttingenGermany
| | - Adina Vultur
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
| | - Ivan Bogeski
- Molecular PhysiologyInstitute of Cardiovascular PhysiologyUniversity Medical CenterGeorg‐August‐UniversityGöttingenGermany
- BiophysicsCIPMMSaarland UniversityHomburgGermany
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61
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Organelle crosstalk in the kidney. Kidney Int 2019; 95:1318-1325. [DOI: 10.1016/j.kint.2018.11.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 11/07/2018] [Accepted: 11/12/2018] [Indexed: 01/24/2023]
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62
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del Castillo U, Gnazzo MM, Turpin CGS, Nguyen KCQ, Semaya E, Lam Y, de Cruz MA, Bembenek JN, Hall DH, Riggs B, Gelfand VI, Skop AR. Conserved role for Ataxin-2 in mediating endoplasmic reticulum dynamics. Traffic 2019; 20:436-447. [PMID: 30989774 PMCID: PMC6553494 DOI: 10.1111/tra.12647] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 04/04/2019] [Accepted: 04/05/2019] [Indexed: 12/17/2022]
Abstract
Ataxin-2, a conserved RNA-binding protein, is implicated in the late-onset neurodegenerative disease Spinocerebellar ataxia type-2 (SCA2). SCA2 is characterized by shrunken dendritic arbors and torpedo-like axons within the Purkinje neurons of the cerebellum. Torpedo-like axons have been described to contain displaced endoplasmic reticulum (ER) in the periphery of the cell; however, the role of Ataxin-2 in mediating ER function in SCA2 is unclear. We utilized the Caenorhabditis elegans and Drosophila homologs of Ataxin-2 (ATX-2 and DAtx2, respectively) to determine the role of Ataxin-2 in ER function and dynamics in embryos and neurons. Loss of ATX-2 and DAtx2 resulted in collapse of the ER in dividing embryonic cells and germline, and ultrastructure analysis revealed unique spherical stacks of ER in mature oocytes and fragmented and truncated ER tubules in the embryo. ATX-2 and DAtx2 reside in puncta adjacent to the ER in both C. elegans and Drosophila embryos. Lastly, depletion of DAtx2 in cultured Drosophila neurons recapitulated the shrunken dendritic arbor phenotype of SCA2. ER morphology and dynamics were severely disrupted in these neurons. Taken together, we provide evidence that Ataxin-2 plays an evolutionary conserved role in ER dynamics and morphology in C. elegans and Drosophila embryos during development and in fly neurons, suggesting a possible SCA2 disease mechanism.
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Affiliation(s)
- Urko del Castillo
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Ave, Chicago, IL 60611
| | - Megan M. Gnazzo
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Christopher G. Sorensen Turpin
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee-Knoxville, Knoxville, Tennessee 37996
| | - Ken C. Q. Nguyen
- Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx New York, NY 10461
| | - Emily Semaya
- Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx New York, NY 10461
| | - Yuwan Lam
- Department of Biology, San Francisco State University, San Francisco, CA 94132
| | - Matthew A. de Cruz
- Department of Biology, San Francisco State University, San Francisco, CA 94132
| | - Joshua N. Bembenek
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee-Knoxville, Knoxville, Tennessee 37996
| | - David H. Hall
- Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx New York, NY 10461
| | - Blake Riggs
- Department of Biology, San Francisco State University, San Francisco, CA 94132
| | - Vladimir I. Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 E Chicago Ave, Chicago, IL 60611
| | - Ahna R. Skop
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
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Xie B, Nguyen PM, Idevall-Hagren O. Feedback regulation of insulin secretion by extended synaptotagmin-1. FASEB J 2018; 33:4716-4728. [PMID: 30589572 DOI: 10.1096/fj.201801878r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Endoplasmic reticulum (ER)-plasma membrane (PM) contacts are dynamic structures with important roles in the regulation of calcium (Ca2+) and lipid homeostasis. The extended synaptotagmins (E-Syts) are ER-localized lipid transport proteins that interact with PM phosphatidylinositol 4,5-bisphosphate in a Ca2+-dependent manner. E-Syts bidirectionally transfer glycerolipids, including diacylglycerol (DAG), between the 2 juxtaposed membranes, but the biologic significance of this transport is still unclear. Using insulin-secreting cells and live-cell imaging, we now show that Ca2+-triggered exocytosis of insulin granules is followed, in sequence, by PM DAG formation and E-Syt1 recruitment. E-Syt1 counteracted the depolarization-induced DAG formation through a mechanism that required both voltage-dependent Ca2+ influx and Ca2+ release from the ER. E-Syt1 knockdown resulted in prolonged accumulation of DAG in the PM, resulting in increased glucose-stimulated insulin secretion. We conclude that Ca2+-triggered exocytosis is temporally coupled to Ca2+-triggered E-Syt1 PM recruitment and removal of DAG to negatively regulate the same process.-Xie, B., Nguyen, P. M., Idevall-Hagren, O. Feedback regulation of insulin secretion by extended synaptotagmin-1.
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Affiliation(s)
- Beichen Xie
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Phuoc My Nguyen
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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Martins VM, Fernandes TR, Lopes D, Afonso CB, Domingues MRM, Côrte-Real M, Sousa MJ. Contacts in Death: The Role of the ER-Mitochondria Axis in Acetic Acid-Induced Apoptosis in Yeast. J Mol Biol 2018; 431:273-288. [PMID: 30414966 DOI: 10.1016/j.jmb.2018.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 10/12/2018] [Accepted: 11/05/2018] [Indexed: 02/08/2023]
Abstract
Endoplasmic reticulum-mitochondria contact sites have been a subject of increasing scientific interest since the discovery that these structures are disrupted in several pathologies. Due to the emerging data that correlate endoplasmic reticulum-mitochondria contact sites function with known events of the apoptotic program, we aimed to dissect this interplay using our well-established model of acetic acid-induced apoptosis in Saccharomyces cerevisiae. Until recently, the only known tethering complex between ER and mitochondria in this organism was the ER-mitochondria encounter structure (ERMES). Following our results from a screening designed to identify genes whose deletion rendered cells with an altered sensitivity to acetic acid, we hypothesized that the ERMES complex could be involved in cell death mediated by this stressor. Herein we demonstrate that single ablation of the ERMES components Mdm10p, Mdm12p and Mdm34p increases the resistance of S. cerevisiae to acetic acid-induced apoptosis, which is associated with a prominent delay in the appearance of several apoptotic markers. Moreover, abrogation of Mdm10p or Mdm34p abolished cytochrome c release from mitochondria. Since these two proteins are embedded in the mitochondrial outer membrane, we propose that the ERMES complex plays a part in cytochrome c release, a key event of the apoptotic cascade. In all, these findings will aid in targeted therapies for diseases where apoptosis is disrupted, as well as assist in the development of acetic acid-resistant strains for industrial processes.
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Affiliation(s)
- Vítor M Martins
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
| | - Tânia R Fernandes
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Diana Lopes
- Mass Spectrometry Centre, Department of Chemistry & QOPNA, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal; Department of Chemistry & CESAM & ECOMARE, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
| | - Catarina B Afonso
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Maria R M Domingues
- Mass Spectrometry Centre, Department of Chemistry & QOPNA, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal; Department of Chemistry & CESAM & ECOMARE, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
| | - Manuela Côrte-Real
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Maria J Sousa
- Centre of Molecular and Environmental Biology, Department of Biology, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
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65
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Li Q, Zhou T, Wu F, Li N, Wang R, Zhao Q, Ma YM, Zhang JQ, Ma BL. Subcellular drug distribution: mechanisms and roles in drug efficacy, toxicity, resistance, and targeted delivery. Drug Metab Rev 2018; 50:430-447. [PMID: 30270675 DOI: 10.1080/03602532.2018.1512614] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
After administration, drug molecules usually enter target cells to access their intracellular targets. In eukaryotic cells, these targets are often located in organelles, including the nucleus, endoplasmic reticulum, mitochondria, lysosomes, Golgi apparatus, and peroxisomes. Each organelle type possesses unique biological features. For example, mitochondria possess a negative transmembrane potential, while lysosomes have an intraluminal delta pH. Other properties are common to several organelle types, such as the presence of ATP-binding cassette (ABC) or solute carrier-type (SLC) transporters that sequester or pump out xenobiotic drugs. Studies on subcellular drug distribution are critical to understand the efficacy and toxicity of drugs along with the body's resistance to them and to potentially offer hints for targeted subcellular drug delivery. This review summarizes the results of studies from 1990 to 2017 that examined the subcellular distribution of small molecular drugs. We hope this review will aid in the understanding of drug distribution within cells.
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Affiliation(s)
- Qiao Li
- a Department of Pharmacology , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Ting Zhou
- a Department of Pharmacology , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Fei Wu
- b Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Na Li
- c Department of Chinese materia medica , School of Pharmacy , Shanghai , China
| | - Rui Wang
- b Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Qing Zhao
- a Department of Pharmacology , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Yue-Ming Ma
- a Department of Pharmacology , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Ji-Quan Zhang
- b Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education , Shanghai University of Traditional Chinese Medicine , Shanghai , China
| | - Bing-Liang Ma
- a Department of Pharmacology , Shanghai University of Traditional Chinese Medicine , Shanghai , China
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66
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Systematic mapping of contact sites reveals tethers and a function for the peroxisome-mitochondria contact. Nat Commun 2018; 9:1761. [PMID: 29720625 PMCID: PMC5932058 DOI: 10.1038/s41467-018-03957-8] [Citation(s) in RCA: 194] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 03/22/2018] [Indexed: 12/15/2022] Open
Abstract
The understanding that organelles are not floating in the cytosol, but rather held in an organized yet dynamic interplay through membrane contact sites, is altering the way we grasp cell biological phenomena. However, we still have not identified the entire repertoire of contact sites, their tethering molecules and functions. To systematically characterize contact sites and their tethering molecules here we employ a proximity detection method based on split fluorophores and discover four potential new yeast contact sites. We then focus on a little-studied yet highly disease-relevant contact, the Peroxisome-Mitochondria (PerMit) proximity, and uncover and characterize two tether proteins: Fzo1 and Pex34. We genetically expand the PerMit contact site and demonstrate a physiological function in β-oxidation of fatty acids. Our work showcases how systematic analysis of contact site machinery and functions can deepen our understanding of these structures in health and disease.
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67
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Zhao YG, Liu N, Miao G, Chen Y, Zhao H, Zhang H. The ER Contact Proteins VAPA/B Interact with Multiple Autophagy Proteins to Modulate Autophagosome Biogenesis. Curr Biol 2018; 28:1234-1245.e4. [PMID: 29628370 DOI: 10.1016/j.cub.2018.03.002] [Citation(s) in RCA: 121] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 02/09/2018] [Accepted: 03/01/2018] [Indexed: 02/03/2023]
Abstract
The endoplasmic reticulum (ER) is the site of biogenesis of the isolation membrane (IM, autophagosome precursor) and forms extensive contacts with IMs during their expansion into double-membrane autophagosomes. Little is known about the molecular mechanism underlying the formation and/or maintenance of the ER/IM contact. The integral ER proteins VAPA and VAPB (VAPs) participate in establishing ER contacts with multiple membranes by interacting with different tethers. Here, we demonstrate that VAPs also modulate ER/IM contact formation. Depletion of VAPs impairs progression of IMs into autophagosomes. Upon autophagy induction, VAPs are recruited to autophagosome formation sites on the ER, a process mediated by their interactions with FIP200 and PI(3)P. VAPs directly interact with FIP200 and ULK1 through their conserved FFAT motifs and stabilize the ULK1/FIP200 complex at the autophagosome formation sites on the ER. The formation of ULK1 puncta is significantly reduced by VAPA/B depletion. VAPs also interact with WIPI2 and enhance the formation of the WIPI2/FIP200 ER/IM tethering complex. Depletion of VMP1, which increases the ER/IM contact, greatly elevates the interaction of VAPs with these autophagy proteins. The VAPB P56S mutation, which is associated with amyotrophic lateral sclerosis, reduces the ULK1/FIP200 interaction and impairs autophagy at an early step, similar to the effect seen in VAPA/B-depleted cells. Our study reveals that VAPs directly interact with multiple ATG proteins, thereby contributing to ER/IM contact formation for autophagosome biogenesis.
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Affiliation(s)
- Yan G Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Nan Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Guangyan Miao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Yong Chen
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Hongyu Zhao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049, China.
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68
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Chomphoo S, Pakkarato S, Sawatpanich T, Sakagami H, Kondo H, Hipkaeo W. Localization of EFA6 (exchange factor for ARF6) isoform D in steroidogenic testicular Leydig cells of adult mice. Acta Histochem 2018; 120:263-268. [PMID: 29496264 DOI: 10.1016/j.acthis.2018.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 02/03/2018] [Accepted: 02/21/2018] [Indexed: 11/19/2022]
Abstract
EFA6 (exchange factor for ARF6) activates Arf6 (ADP ribosylation factor 6) by exchanging ADP to ATP and the resulting activated form of Arf6 is involved in the membrane trafficking and actin remodeling of cells. Our previous study has shown the selective expression/localization of EFA6D in steroidogenic adrenocortical cells in situ of adult mice. In view of the previous finding, the present study was undertaken to examine its localization in mouse Leydig cells representing another steroidogenic cell species in order to further support the possible involvement of the EFA6/Arf6 cascade via membrane trafficking in the regulation of steroidogenesis and/or secretion. A distinct band for EFA6D with the same size as that of the brain was detected in the testis of adult mice. In immuno-light microscopy, immunoreactivity for EFA6D was seen throughout the cytoplasm in most Leydig cells without any distinct accumulation along the plasmalemma. Lack of immunoreactivity for EFA6D was seen in the seminiferous tubular epithelium. In immuno-electron microscopy, the immune-labeling was seen in sporadic/focal patterns on plasma membranes and some vesicles and vacuoles subjacent to the plasma membranes. More constant and rather predominant is the labeling on numerous mitochondria. No immuno-labeling was seen in lipid droplets. The present study suggests that EFA6D is somehow involved in regulation of the synthesis and/or secretion of testosterone through the membrane-traffic by activation of Arf6. In addition, EFA6D is suggested to play in mitochondria some yet unidentified roles rather independent of Arf6-activation, which remains to be elucidated.
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Affiliation(s)
- Surang Chomphoo
- Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Sawetree Pakkarato
- Department of Social Sciences, Faculty of Sciences and Liberal Arts, Rajamangala University of Technology Isan, Sura Narai Rd, Nai-muang, Muang, Nakhon Ratchasima 30000, Thailand
| | - Tarinee Sawatpanich
- Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Hiroyuki Sakagami
- Department of Anatomy, School of Medicine, Kitasato University, Tokyo, Japan
| | - Hisatake Kondo
- Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand
| | - Wiphawi Hipkaeo
- Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
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69
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Non-vesicular lipid trafficking at the endoplasmic reticulum–mitochondria interface. Biochem Soc Trans 2018; 46:437-452. [DOI: 10.1042/bst20160185] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 02/20/2018] [Accepted: 02/22/2018] [Indexed: 12/14/2022]
Abstract
Mitochondria are highly dynamic organelles involved in various cellular processes such as energy production, regulation of calcium homeostasis, lipid trafficking, and apoptosis. To fulfill all these functions and preserve their morphology and dynamic behavior, mitochondria need to maintain a defined protein and lipid composition in both their membranes. The maintenance of mitochondrial membrane identity requires a selective and regulated transport of specific lipids from/to the endoplasmic reticulum (ER) and across the mitochondria outer and inner membranes. Since they are not integrated in the classical vesicular trafficking routes, mitochondria exchange lipids with the ER at sites of close apposition called membrane contact sites. Deregulation of such transport activities results in several pathologies including cancer and neurodegenerative disorders. However, we are just starting to understand the function of ER–mitochondria contact sites in lipid transport, what are the proteins involved and how they are regulated. In this review, we summarize recent insights into lipid transport pathways at the ER–mitochondria interface and discuss the implication of recently identified lipid transfer proteins in these processes.
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70
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Todkar K, Ilamathi HS, Germain M. Mitochondria and Lysosomes: Discovering Bonds. Front Cell Dev Biol 2017; 5:106. [PMID: 29270406 PMCID: PMC5725469 DOI: 10.3389/fcell.2017.00106] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 11/22/2017] [Indexed: 01/30/2023] Open
Abstract
In the last decade, the traditional view of lysosomes has been challenged by the recognition that lysosomes are not only degradative organelles, but also metabolic sensors that play a key role in the regulation of metabolism and cell growth. Similarly, mitochondria are now seen as crucial metabolic hubs dictating cell fate decisions, not just ATP-producing machines. Importantly, these functions are generally performed as a coordinate response of distinct organelles that are physically and functionally connected. While the association between mitochondria and the endoplasmic reticulum is well known, a similar interaction between mitochondria and lysosomes is now emerging. This interaction could be required to shuttle amino acids, lipids and ions such as Ca2+ between the two organelles, thereby modulating their metabolic functions. In addition, a tethering complex linking the two organelles has recently been described in yeast, although the mammalian counterpart has yet to be identified. Here, we discuss the implications of these recent findings.
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Affiliation(s)
- Kiran Todkar
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada.,Centre de Recherche Biomed, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
| | - Hema S Ilamathi
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada.,Centre de Recherche Biomed, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
| | - Marc Germain
- Groupe de Recherche en Signalisation Cellulaire and Département de Biologie Médicale, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada.,Centre de Recherche Biomed, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada
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71
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Hoffmann PC, Kukulski W. Perspective on architecture and assembly of membrane contact sites. Biol Cell 2017; 109:400-408. [PMID: 28960356 DOI: 10.1111/boc.201700031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 09/21/2017] [Accepted: 09/21/2017] [Indexed: 01/25/2023]
Abstract
Membrane contact sites (MCS) are platforms of physical contact between different organelles. They are formed through interactions involving lipids and proteins, and function in processes such as calcium and lipid exchange, metabolism and organelle biogenesis. In this article, we discuss emerging questions regarding the architecture, organisation and assembly of MCS, such as: What is the contribution of different components to the interaction between organelles? How is the specific composition of different types of membrane contacts sites established and maintained? How are proteins and lipids spatially organised at MCS and how does that influence their function? How dynamic are MCS on the molecular and ultrastructural level? We highlight current state of research and point out experimental approaches that promise to contribute to a spatiomechanistic understanding of MCS functions.
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Affiliation(s)
- Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK
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72
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Crystal structures of Mmm1 and Mdm12-Mmm1 reveal mechanistic insight into phospholipid trafficking at ER-mitochondria contact sites. Proc Natl Acad Sci U S A 2017; 114:E9502-E9511. [PMID: 29078410 DOI: 10.1073/pnas.1715592114] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The endoplasmic reticulum (ER)-mitochondria encounter structure (ERMES) comprises mitochondrial distribution and morphology 12 (Mdm12), maintenance of mitochondrial morphology 1 (Mmm1), Mdm34, and Mdm10 and mediates physical membrane contact sites and nonvesicular lipid trafficking between the ER and mitochondria in yeast. Herein, we report two crystal structures of the synaptotagmin-like mitochondrial lipid-binding protein (SMP) domain of Mmm1 and the Mdm12-Mmm1 complex at 2.8 Å and 3.8 Å resolution, respectively. Mmm1 adopts a dimeric SMP structure augmented with two extra structural elements at the N and C termini that are involved in tight self-association and phospholipid coordination. Mmm1 binds two phospholipids inside the hydrophobic cavity, and the phosphate ion of the distal phospholipid is specifically recognized through extensive H-bonds. A positively charged concave surface on the SMP domain not only mediates ER membrane docking but also results in preferential binding to glycerophospholipids such as phosphatidylcholine (PC), phosphatidic acid (PA), phosphatidylglycerol (PG), and phosphatidylserine (PS), some of which are substrates for lipid-modifying enzymes in mitochondria. The Mdm12-Mmm1 structure reveals two Mdm12s binding to the SMP domains of the Mmm1 dimer in a pairwise head-to-tail manner. Direct association of Mmm1 and Mdm12 generates a 210-Å-long continuous hydrophobic tunnel that facilitates phospholipid transport. The Mdm12-Mmm1 complex binds all glycerophospholipids except for phosphatidylethanolamine (PE) in vitro.
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73
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The Role of Mitochondria in the Activation/Maintenance of SOCE: Membrane Contact Sites as Signaling Hubs Sustaining Store-Operated Ca2+ Entry. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:277-296. [DOI: 10.1007/978-3-319-57732-6_15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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74
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Demetriadou A, Drousiotou A, Petrou PP. The “sweet” side of ER-mitochondria contact sites. Commun Integr Biol 2017. [PMCID: PMC5595418 DOI: 10.1080/19420889.2017.1329787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The regions at which the ER and mitochondria come into close proximity, known as ER-mitochondria contact sites provide essential platforms for the exchange of molecules between the two organelles and the coordination of various fundamental cellular processes. In addition to the well-established role of ER-mitochondria interfaces in calcium and lipid crosstalk, emerging evidence supports that a proper communication between ER and mitochondria is critical for the regulation of mitochondrial morphology and the initiation of autophagy. Within this context, our recent data indicate that glycogen is targeted to ER-mitochondria contacts through the Stbd1 protein, a proposed autophagy receptor for glycogen. Glycogen-bound Stbd1 influences ER-mitochondria tethering and the morphology of the mitochondrial network. We here suggest possible roles of glycogen recruitment to ER-mitochondria contact sites. Stbd1-mediated targeting of glycogen to ER-mitochondria junctions could represent a mechanism through which glycogen is sequestered into autophagosomes for lysosomal degradation, a process described as glycogen autophagy or glycophagy. Additionally, we discuss a possible mechanism which links the observed effects of Stbd1 on mitochondrial morphology with the previously reported impact of nutrient availability on mitochondrial dynamics. In this model we propose that glycogen-bound Stbd1 signals nutrient status to ER-mitochondria junctions resulting in adaptations in the morphology of the mitochondrial network.
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Affiliation(s)
- Anthi Demetriadou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- The Cyprus School of Molecular Medicine, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Anthi Drousiotou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- The Cyprus School of Molecular Medicine, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
| | - Petros P. Petrou
- Department of Biochemical Genetics, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
- The Cyprus School of Molecular Medicine, The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus
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75
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Gottschling DE, Nyström T. The Upsides and Downsides of Organelle Interconnectivity. Cell 2017; 169:24-34. [PMID: 28340346 DOI: 10.1016/j.cell.2017.02.030] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/13/2017] [Accepted: 02/21/2017] [Indexed: 12/31/2022]
Abstract
Interconnectivity and feedback control are hallmarks of biological systems. This includes communication between organelles, which allows them to function and adapt to changing cellular environments. While the specific mechanisms for all communications remain opaque, unraveling the wiring of organelle networks is critical to understand how biological systems are built and why they might collapse, as occurs in aging. A comprehensive understanding of all the routes involved in inter-organelle communication is still lacking, but important themes are beginning to emerge, primarily in budding yeast. These routes are reviewed here in the context of sub-system proteostasis and complex adaptive systems theory.
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Affiliation(s)
| | - Thomas Nyström
- Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden.
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76
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Contacts between the endoplasmic reticulum and other membranes in neurons. Proc Natl Acad Sci U S A 2017; 114:E4859-E4867. [PMID: 28559323 DOI: 10.1073/pnas.1701078114] [Citation(s) in RCA: 303] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Close appositions between the membrane of the endoplasmic reticulum (ER) and other intracellular membranes have important functions in cell physiology. These include lipid homeostasis, regulation of Ca2+ dynamics, and control of organelle biogenesis and dynamics. Although these membrane contacts have previously been observed in neurons, their distribution and abundance have not been systematically analyzed. Here, we have used focused ion beam-scanning electron microscopy to generate 3D reconstructions of intracellular organelles and their membrane appositions involving the ER (distance ≤30 nm) in different neuronal compartments. ER-plasma membrane (PM) contacts were particularly abundant in cell bodies, with large, flat ER cisternae apposed to the PM, sometimes with a notably narrow lumen (thin ER). Smaller ER-PM contacts occurred throughout dendrites, axons, and in axon terminals. ER contacts with mitochondria were abundant in all compartments, with the ER often forming a network that embraced mitochondria. Small focal contacts were also observed with tubulovesicular structures, likely to be endosomes, and with sparse multivesicular bodies and lysosomes found in our reconstructions. Our study provides an anatomical reference for interpreting information about interorganelle communication in neurons emerging from functional and biochemical studies.
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77
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Nascimbeni AC, Giordano F, Dupont N, Grasso D, Vaccaro MI, Codogno P, Morel E. ER-plasma membrane contact sites contribute to autophagosome biogenesis by regulation of local PI3P synthesis. EMBO J 2017; 36:2018-2033. [PMID: 28550152 DOI: 10.15252/embj.201797006] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 04/27/2017] [Accepted: 04/28/2017] [Indexed: 12/21/2022] Open
Abstract
The double-membrane-bound autophagosome is formed by the closure of a structure called the phagophore, origin of which is still unclear. The endoplasmic reticulum (ER) is clearly implicated in autophagosome biogenesis due to the presence of the omegasome subdomain positive for DFCP1, a phosphatidyl-inositol-3-phosphate (PI3P) binding protein. Contribution of other membrane sources, like the plasma membrane (PM), is still difficult to integrate in a global picture. Here we show that ER-plasma membrane contact sites are mobilized for autophagosome biogenesis, by direct implication of the tethering extended synaptotagmins (E-Syts) proteins. Imaging data revealed that early autophagic markers are recruited to E-Syt-containing domains during autophagy and that inhibition of E-Syts expression leads to a reduction in autophagosome biogenesis. Furthermore, we demonstrate that E-Syts are essential for autophagy-associated PI3P synthesis at the cortical ER membrane via the recruitment of VMP1, the stabilizing ER partner of the PI3KC3 complex. These results highlight the contribution of ER-plasma membrane tethers to autophagosome biogenesis regulation and support the importance of membrane contact sites in autophagy.
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Affiliation(s)
- Anna Chiara Nascimbeni
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Paris, France
| | - Francesca Giordano
- Institut Jacques Monod, CNRS UMR 7592, Paris, France.,Université Paris Diderot-Sorbonne Paris Cité, Paris, France
| | - Nicolas Dupont
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Paris, France
| | - Daniel Grasso
- Department of Pathophysiology, Institute of Biochemistry and Molecular Medicine, National Council for Scientific and Technological Research, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
| | - Maria I Vaccaro
- Department of Pathophysiology, Institute of Biochemistry and Molecular Medicine, National Council for Scientific and Technological Research, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina
| | - Patrice Codogno
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Paris, France.,Université Paris Descartes-Sorbonne Paris Cité, Paris, France
| | - Etienne Morel
- Institut Necker-Enfants Malades (INEM), INSERM U1151-CNRS UMR 8253, Paris, France .,Université Paris Descartes-Sorbonne Paris Cité, Paris, France
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78
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Mechanistic insight into the nucleus-vacuole junction based on the Vac8p-Nvj1p crystal structure. Proc Natl Acad Sci U S A 2017; 114:E4539-E4548. [PMID: 28533415 DOI: 10.1073/pnas.1701030114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Formation of the nucleus-vacuole junction (NVJ) is mediated by direct interaction between the vacuolar protein Vac8p and the outer nuclear endoplasmic reticulum membrane protein Nvj1p. Herein we report the crystal structure of Vac8p bound to Nvj1p at 2.4-Å resolution. Vac8p comprises a flexibly connected N-terminal H1 helix followed by 12 armadillo repeats (ARMs) that form a right-handed superhelical structure. The extended 80-Å-long loop of Nvj1p specifically binds the highly conserved inner groove formed from ARM1-12 of Vac8p. Disruption of the Nvj1p-Vac8p interaction results in the loss of tight NVJs, which impairs piecemeal microautophagy of the nucleus in Saccharomyces cerevisiae Vac8p cationic triad (Arg276, Arg317, and Arg359) motifs interacting with Nvj1p are also critical to the recognition of Atg13p, a key component of the cytoplasm-to-vacuole targeting (CVT) pathway, indicating competitive binding to Vac8p. Indeed, mutation of the cationic triad abolishes CVT of Ape1p in vivo. Combined with biochemical data, the crystal structure reveals a Vac8p homodimer formed from ARM1, and this self-association, likely regulated by the flexible H1 helix and the C terminus of Nvj1p, is critical for Vac8p cellular functions.
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79
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Mitochondria-organelle contact sites: the plot thickens. Biochem Soc Trans 2017; 45:477-488. [PMID: 28408488 DOI: 10.1042/bst20160130] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 02/07/2017] [Accepted: 02/13/2017] [Indexed: 01/30/2023]
Abstract
Membrane contact sites (MCSs) are areas of close apposition between the membranes of two different organelles that enable non-vesicular transfer of ions and lipids. Recent studies reveal that mitochondria maintain contact sites with organelles other than the endoplasmic reticulum such as the vacuole, plasma membrane and peroxisomes. This review focuses on novel findings achieved mainly in yeast regarding tethers, function and regulation of mitochondria-organelle contact sites. The emerging network of MCSs linking virtually all cellular organelles is highly dynamic and integrated with cellular metabolism.
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80
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Eisenberg-Bord M, Schuldiner M. Mitochatting - If only we could be a fly on the cell wall. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1469-1480. [PMID: 28433686 DOI: 10.1016/j.bbamcr.2017.04.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/07/2017] [Revised: 04/12/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022]
Abstract
Mitochondria, cellular metabolic hubs, perform many essential processes and are required for the production of metabolites such as ATP, iron-sulfur clusters, heme, amino acids and nucleotides. To fulfill their multiple roles, mitochondria must communicate with all other organelles to exchange small molecules, ions and lipids. Since mitochondria are largely excluded from vesicular trafficking routes, they heavily rely on membrane contact sites. Contact sites are areas of close proximity between organelles that allow efficient transfer of molecules, saving the need for slow and untargeted diffusion through the cytosol. More globally, multiple metabolic pathways require coordination between mitochondria and additional organelles and mitochondrial activity affects all other cellular entities and vice versa. Therefore, uncovering the different means of mitochondrial communication will allow us a better understanding of mitochondria and may illuminate disease processes that occur in the absence of proper cross-talk. In this review we focus on how mitochondria interact with all other organelles and emphasize how this communication is essential for mitochondrial and cellular homeostasis. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Michal Eisenberg-Bord
- Department of Molecular Genetics, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, 7610001 Rehovot, Israel.
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81
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Chen CL, Perrimon N. Proximity-dependent labeling methods for proteomic profiling in living cells. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2017; 6. [PMID: 28387482 DOI: 10.1002/wdev.272] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 02/03/2017] [Accepted: 02/10/2017] [Indexed: 02/05/2023]
Abstract
Characterizing the proteome composition of organelles and subcellular regions of living cells can facilitate the understanding of cellular organization as well as protein interactome networks. Proximity labeling-based methods coupled with mass spectrometry (MS) offer a high-throughput approach for systematic analysis of spatially restricted proteomes. Proximity labeling utilizes enzymes that generate reactive radicals to covalently tag neighboring proteins with biotin. The biotinylated endogenous proteins can then be isolated for further analysis by MS. To analyze protein-protein interactions or identify components that localize to discrete subcellular compartments, spatial expression is achieved by fusing the enzyme to specific proteins or signal peptides that target to particular subcellular regions. Although these technologies have only been introduced recently, they have already provided deep insights into a wide range of biological processes. Here, we describe and compare current methods of proximity labeling as well as their applications. As each method has its own unique features, the goal of this review is to describe how different proximity labeling methods can be used to answer different biological questions. WIREs Dev Biol 2017, 6:e272. doi: 10.1002/wdev.272 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Chiao-Lin Chen
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, MA, USA.,Howard Hughes Medical Institute, Boston, MA, USA
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82
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Luo J, Jiang L, Yang H, Song BL. Routes and mechanisms of post-endosomal cholesterol trafficking: A story that never ends. Traffic 2017; 18:209-217. [DOI: 10.1111/tra.12471] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 12/22/2022]
Affiliation(s)
- Jie Luo
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences; Wuhan University; Wuhan China
| | - Luyi Jiang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences; Wuhan University; Wuhan China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney Australia
| | - Bao-Liang Song
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences; Wuhan University; Wuhan China
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83
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Deciphering the molecular architecture of membrane contact sites by cryo-electron tomography. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1507-1512. [PMID: 28330771 DOI: 10.1016/j.bbamcr.2017.03.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/13/2017] [Accepted: 03/17/2017] [Indexed: 01/16/2023]
Abstract
At membrane contact sites (MCS) two cellular membranes form tight appositions that play critical roles in fundamental phenomena such as lipid metabolism or Ca2+ homeostasis. The interest for these structures has surged in recent years, bringing about the characterization of a plethora of MCS-resident molecules. How those molecules are structurally organized at MCS remains enigmatic, limiting our understanding of MCS function. Whereas such molecular detail is obscured by conventional electron microscopy sample preparation, cryo-electron tomography (cryo-ET) allows high resolution imaging of cellular landscapes in close-to-native conditions. Here we briefly review the fundamentals of cryo-ET and how recent developments in this technique are beginning to unveil the molecular architecture of MCS. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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84
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Mitochondrial behaviour throughout the lytic cycle of Toxoplasma gondii. Sci Rep 2017; 7:42746. [PMID: 28202940 PMCID: PMC5311943 DOI: 10.1038/srep42746] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/12/2017] [Indexed: 01/11/2023] Open
Abstract
Mitochondria distribution in cells controls cellular physiology in health and disease. Here we describe the mitochondrial morphology and positioning found in the different stages of the lytic cycle of the eukaryotic single-cell parasite Toxoplasma gondii. The lytic cycle, driven by the tachyzoite life stage, is responsible for acute toxoplasmosis. It is known that whilst inside a host cell the tachyzoite maintains its single mitochondrion at its periphery. We found that upon parasite transition from the host cell to the extracellular matrix, mitochondrion morphology radically changes, resulting in a reduction in peripheral proximity. This change is reversible upon return to the host, indicating that an active mechanism maintains the peripheral positioning found in the intracellular stages. Comparison between the two states by electron microscopy identified regions of coupling between the mitochondrion outer membrane and the parasite pellicle, whose features suggest the presence of membrane contact sites, and whose abundance changes during the transition between intra- and extra-cellular states. These novel observations pave the way for future research to identify molecular mechanisms involved in mitochondrial distribution in Toxoplasma and the consequences of these mitochondrion changes on parasite physiology.
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85
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Herrera-Cruz MS, Simmen T. Of yeast, mice and men: MAMs come in two flavors. Biol Direct 2017; 12:3. [PMID: 28122638 PMCID: PMC5267431 DOI: 10.1186/s13062-017-0174-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 01/18/2017] [Indexed: 12/15/2022] Open
Abstract
The past decade has seen dramatic progress in our understanding of membrane contact sites (MCS). Important examples of these are endoplasmic reticulum (ER)-mitochondria contact sites. ER-mitochondria contacts have originally been discovered in mammalian tissue, where they have been designated as mitochondria-associated membranes (MAMs). It is also in this model system, where the first critical MAM proteins have been identified, including MAM tethering regulators such as phospho-furin acidic cluster sorting protein 2 (PACS-2) and mitofusin-2. However, the past decade has seen the discovery of the MAM also in the powerful yeast model system Saccharomyces cerevisiae. This has led to the discovery of novel MAM tethers such as the yeast ER-mitochondria encounter structure (ERMES), absent in the mammalian system, but whose regulators Gem1 and Lam6 are conserved. While MAMs, sometimes referred to as mitochondria-ER contacts (MERCs), regulate lipid metabolism, Ca2+ signaling, bioenergetics, inflammation, autophagy and apoptosis, not all of these functions exist in both systems or operate differently. This biological difference has led to puzzling discrepancies on findings obtained in yeast or mammalian cells at the moment. Our review aims to shed some light onto mechanistic differences between yeast and mammalian MAM and their underlying causes. Reviewers: This article was reviewed by Paola Pizzo (nominated by Luca Pellegrini), Maya Schuldiner and György Szabadkai (nominated by Luca Pellegrini).
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Affiliation(s)
- Maria Sol Herrera-Cruz
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, T6G2H7, Canada
| | - Thomas Simmen
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, T6G2H7, Canada.
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86
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Ba Q, Yang G. Intracellular organelle networks: Understanding their organization and communication through systems-level modeling and analysis. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/s11515-016-1436-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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87
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Kannan M, Lahiri S, Liu LK, Choudhary V, Prinz WA. Phosphatidylserine synthesis at membrane contact sites promotes its transport out of the ER. J Lipid Res 2017; 58:553-562. [PMID: 28119445 DOI: 10.1194/jlr.m072959] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Revised: 12/24/2016] [Indexed: 11/20/2022] Open
Abstract
Close contacts between organelles, often called membrane contact sites (MCSs), are regions where lipids are exchanged between organelles. Here, we identify a novel mechanism by which cells promote phospholipid exchange at MCSs. Previous studies have shown that phosphatidylserine (PS) synthase activity is highly enriched in portions of the endoplasmic reticulum (ER) in contact with mitochondria. The objective of this study was to determine whether this enrichment promotes PS transport out of the ER. We found that PS transport to mitochondria was more efficient when PS synthase was fused to a protein in the ER at ER-mitochondria contacts than when it was fused to a protein in all portions of the ER. Inefficient PS transport to mitochondria was corrected by increasing tethering between these organelles. PS transport to endosomes was similarly enhanced by PS production in regions of the ER in contact with endosomes. Together, these findings indicate that PS production at MCSs promotes PS transport out of the ER and suggest that phospholipid production at MCSs may be a general mechanism of channeling lipids to specific cellular compartments.
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Affiliation(s)
- Muthukumar Kannan
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Sujoy Lahiri
- Department of Pharmacology, School of Medicine, University of Virginia, Charlottesville, VA 22908
| | - Li-Ka Liu
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Vineet Choudhary
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
| | - William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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88
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Endoplasmic Reticulum - Plasma Membrane Crosstalk Mediated by the Extended Synaptotagmins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 997:83-93. [PMID: 28815523 DOI: 10.1007/978-981-10-4567-7_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The endoplasmic reticulum (ER) possesses multiplicity of functions including protein synthesis, membrane lipid biogenesis, and Ca2+ storage and has broad localization throughout the cell. While the ER and most other membranous organelles are highly interconnected via vesicular traffic that relies on membrane budding and fusion reactions, the ER forms direct contacts with virtually all other membranous organelles, including the plasma membrane (PM), without membrane fusion. Growing evidence suggests that these contacts play major roles in cellular physiology, including the regulation of Ca2+ homeostasis and signaling and control of cellular lipid homeostasis. Extended synaptotagmins (E-Syts) are evolutionarily conserved family of ER-anchored proteins that tether the ER to the PM in PM PI(4,5)P2-dependent and cytosolic Ca2+-regulated manner. In addition, E-Syts possess a cytosolically exposed lipid-harboring module that confers the ability to transfer/exchange glycerolipids between the ER and the PM at E-Syts-mediated ER-PM contacts. In this chapter, the functions of ER-PM contacts and their role in non-vesicular lipid transport with special emphasis on the crosstalk between the two bilayers mediated by E-Syts will be discussed.
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89
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Henne WM. Discovery and Roles of ER-Endolysosomal Contact Sites in Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 997:135-147. [PMID: 28815527 DOI: 10.1007/978-981-10-4567-7_10] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Inter-organelle membrane contact sites (MCSs) serve as unique microenvironments for the sensing and exchange of cellular metabolites and lipids. Though poorly defined, ER-endolysosomal contact sites are quickly becoming recognized as centers for inter-organelle lipid exchange and metabolic decision-making. Here, we review the discovery and current state of knowledge of ER-endolysosomal MCSs with particular focus on the molecular players that establish and/or utilize these contact sites in metabolism. We also discuss associations of ER-endolysosomal MCS-associated proteins in human disease, as well as the therapeutic promise these contact sites hold in modulating cellular physiology.
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Affiliation(s)
- William Mike Henne
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, 75013, USA.
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90
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Supramolecular architecture of endoplasmic reticulum-plasma membrane contact sites. Biochem Soc Trans 2016; 44:534-40. [PMID: 27068966 DOI: 10.1042/bst20150279] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 11/17/2022]
Abstract
The endoplasmic reticulum (ER) forms membrane contact sites (MCS) with most other cellular organelles and the plasma membrane (PM). These ER-PM MCS, where the membranes of the ER and PM are closely apposed, were discovered in the early days of electron microscopy (EM), but only recently are we starting to understand their functional and structural diversity. ER-PM MCS are nowadays known to mediate excitation-contraction coupling (ECC) in striated muscle cells and to play crucial roles in Ca(2+)and lipid homoeostasis in all metazoan cells. A common feature across ER-PM MCS specialized in different functions is the preponderance of cooperative phenomena that result in the formation of large supramolecular assemblies. Therefore, characterizing the supramolecular architecture of ER-PM MCS is critical to understand their mechanisms of function. Cryo-electron tomography (cryo-ET) is a powerful EM technique uniquely positioned to address this issue, as it allows 3D imaging of fully hydrated, unstained cellular structures at molecular resolution. In this review I summarize our current structural knowledge on the molecular organization of ER-PM MCS and its functional implications, with special emphasis on the emerging contributions of cryo-ET.
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91
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Abstract
Membrane contact sites (MCSs) are subcellular regions where the membranes of distinct organelles come into close apposition. These specialized areas of the cell, which are involved in inter-organelle metabolite exchange, are scaffolded by specific complexes. STARD3 [StAR (steroidogenic acute regulatory protein)-related lipid transfer domain-3] and its close paralogue STARD3NL (STARD3 N-terminal like) are involved in the formation of contacts between late-endosomes and the endoplasmic reticulum (ER). The lipid transfer protein (LTP) STARD3 and STARD3NL, which are both anchored on the limiting membrane of late endosomes (LEs), interact with ER-anchored VAP [VAMP (vesicle-associated membrane protein)-associated protein] (VAP-A and VAP-B) proteins. This direct interaction allows ER-endosome contact formation. STARD3 or STARD3NL-mediated ER-endosome contacts, which affect endosome dynamics, are believed to be involved in cholesterol transport.
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92
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Abstract
Cellular membranes communicate extensively via contact sites that form between two membranes. Such sites allow exchange of specific ions, lipids or proteins between two compartments without content mixing, thereby preserving organellar architecture during the transfer process. Even though the molecular compositions of membrane contact sites are diverse, it is striking that several of these sites, including contact sites between the endoplasmic reticulum (ER) and endosomes, Golgi and the plasma membrane (PM), and contact sites between lysosomes and peroxisomes, contain phosphorylated derivatives of phosphatidylinositol known as phosphoinositides. In this mini-review we discuss the involvement and functions of phosphoinositides in membrane contact sites.
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93
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Jeong H, Park J, Lee C. Crystal structure of Mdm12 reveals the architecture and dynamic organization of the ERMES complex. EMBO Rep 2016; 17:1857-1871. [PMID: 27821511 PMCID: PMC5283602 DOI: 10.15252/embr.201642706] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 09/23/2016] [Accepted: 09/30/2016] [Indexed: 01/07/2023] Open
Abstract
The endoplasmic reticulum-mitochondria encounter structure (ERMES) is a protein complex that plays a tethering role in physically connecting ER and mitochondria membranes. The ERMES complex is composed of Mdm12, Mmm1, and Mdm34, which have a SMP domain in common, and Mdm10. Here, we report the crystal structure of S. cerevisiae Mdm12. The Mdm12 forms a dimeric SMP structure through domain swapping of the β1-strand comprising residues 1-7. Biochemical experiments reveal a phospholipid-binding site located along a hydrophobic channel of the Mdm12 structure and that Mdm12 might have a binding preference for glycerophospholipids harboring a positively charged head group. Strikingly, both full-length Mdm12 and Mdm12 truncated to exclude the disordered region (residues 74-114) display the same organization in the asymmetric unit, although they crystallize as a tetramer and hexamer, respectively. Taken together, these studies provide a novel understanding of the overall organization of SMP domains in the ERMES complex, indicating that Mdm12 interacts with Mdm34 through head-to-head contact, and with Mmm1 through tail-to-tail contact of SMP domains.
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Affiliation(s)
- Hanbin Jeong
- Department of Biological SciencesSchool of Life SciencesUlsan National Institute of Science and TechnologyUlsanKorea,Cell Logistics Research CenterGwangju Institute of Science and TechnologyGwangjuKorea
| | - Jumi Park
- Department of Biological SciencesSchool of Life SciencesUlsan National Institute of Science and TechnologyUlsanKorea,Cell Logistics Research CenterGwangju Institute of Science and TechnologyGwangjuKorea
| | - Changwook Lee
- Department of Biological SciencesSchool of Life SciencesUlsan National Institute of Science and TechnologyUlsanKorea,Cell Logistics Research CenterGwangju Institute of Science and TechnologyGwangjuKorea,Center for Genome IntegrityInstitute for Basic Science (IBS)UlsanKorea
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94
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Liu J, Postupalenko V, Lörcher S, Wu D, Chami M, Meier W, Palivan CG. DNA-Mediated Self-Organization of Polymeric Nanocompartments Leads to Interconnected Artificial Organelles. NANO LETTERS 2016; 16:7128-7136. [PMID: 27726407 DOI: 10.1021/acs.nanolett.6b03430] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Self-organization of nanocomponents was mainly focused on solid nanoparticles, quantum dots, or liposomes to generate complex architectures with specific properties, but intrinsically limited or not developed enough, to mimic sophisticated structures with biological functions in cells. Here, we present a biomimetic strategy to self-organize synthetic nanocompartments (polymersomes) into clusters with controlled properties and topology by exploiting DNA hybridization to interconnect polymersomes. Molecular and external factors affecting the self-organization served to design clusters mimicking the connection of natural organelles: fine-tune of the distance between tethered polymersomes, different topologies, no fusion of clustered polymersomes, and no aggregation. Unexpected, extended DNA bridges that result from migration of the DNA strands inside the thick polymer membrane (about 12 nm) represent a key stability and control factor, not yet exploited for other synthetic nano-object networks. The replacement of the empty polymersomes with artificial organelles, already reported for single polymersome architecture, will provide an excellent platform for the development of artificial systems mimicking natural organelles or cells and represents a fundamental step in the engineering of molecular factories.
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Affiliation(s)
- Juan Liu
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
| | - Viktoriia Postupalenko
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
| | - Samuel Lörcher
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
| | - Dalin Wu
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
| | - Mohamed Chami
- BioEM lab, Biozentrum, University of Basel , Mattenstrasse 26, 4058 Basel, Switzerland
| | - Wolfgang Meier
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel , Klingelbergstrasse 80, Basel 4056, Switzerland
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95
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Tong J, Manik MK, Yang H, Im YJ. Structural insights into nonvesicular lipid transport by the oxysterol binding protein homologue family. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:928-939. [DOI: 10.1016/j.bbalip.2016.01.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 12/23/2015] [Accepted: 01/14/2016] [Indexed: 10/22/2022]
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96
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Abstract
PURPOSE OF REVIEW In this article, we summarize the present information related to the export of LDL-derived cholesterol from late endosomes, with a focus on Nieman-Pick disease, type C1 (NPC1) cholesterol delivery toward the endoplasmic reticulum (ER). We review data suggesting that several pathways may operate in parallel, including membrane transport routes and membrane contact sites (MCSs). RECENT FINDINGS There is increasing appreciation that MCSs provide an important mechanism for intermembrane lipid transfer. In late endosome-ER contacts, three protein bridges involving oxysterol binding protein related protein (ORP)1L-vesicle associated membrane protein-associated protein (VAP), steroidogenic acute regulatory protein (StAR)D3-VAP and ORP5-NPC1 proteins have been reported. How much they contribute to the flux of LDL-cholesterol to the ER is currently open. Studies for lipid transfer via MCSs have been most advanced in Saccharomyces cerevisiae. Recently, a new sterol-binding protein family conserved between yeast and man was identified. Its members localize at MCSs and were named lipid transfer protein anchored at membrane contact sites (Lam) proteins. In yeast, sterol transfer between the ER and the yeast lysosome may be facilitated by a Lam protein. SUMMARY Increasing insights into the role of MCSs in directional sterol delivery between membranes propose that they might provide routes for LDL-cholesterol transfer to the ER. Future work should reveal which specific contacts may operate for this, and how they are controlled by cholesterol homeostatic machineries.
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Affiliation(s)
- Simon G Pfisterer
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Finland and Minerva Foundation Institute for Medical Research, Helsinki, Finland
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97
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Kmiecik P, Leonardelli M, Teige M. Novel connections in plant organellar signalling link different stress responses and signalling pathways. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3793-807. [PMID: 27053718 DOI: 10.1093/jxb/erw136] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
To coordinate growth, development and responses to environmental stimuli, plant cells need to communicate the metabolic state between different sub-compartments of the cell. This requires signalling pathways, including protein kinases, secondary messengers such as Ca(2+) ions or reactive oxygen species (ROS) as well as metabolites and plant hormones. The signalling networks involved have been intensively studied over recent decades and have been elaborated more or less in detail. However, it has become evident that these signalling networks are also tightly interconnected and often merge at common targets such as a distinct group of transcription factors, most prominently ABI4, which are amenable to regulation by phosphorylation, potentially also in a Ca(2+)- or ROS-dependent fashion. Moreover, the signalling pathways connect several organelles or subcellular compartments, not only in functional but also in physical terms, linking for example chloroplasts to the nucleus or peroxisomes to chloroplasts thereby enabling physical routes for signalling by metabolite exchange or even protein translocation. Here we briefly discuss these novel findings and try to connect them in order to point out the remaining questions and emerging developments in plant organellar signalling.
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Affiliation(s)
- Przemyslaw Kmiecik
- Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Manuela Leonardelli
- Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Markus Teige
- Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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98
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Abstract
The endoplasmic reticulum is the port of entry for proteins into the secretory pathway and the site of synthesis for several important lipids, including cholesterol, triacylglycerol, and phospholipids. Protein production within the endoplasmic reticulum is tightly regulated by a cohort of resident machinery that coordinates the folding, modification, and deployment of secreted and integral membrane proteins. Proteins failing to attain their native conformation are degraded through the endoplasmic reticulum-associated degradation (ERAD) pathway via a series of tightly coupled steps: substrate recognition, dislocation, and ubiquitin-dependent proteasomal destruction. The same ERAD machinery also controls the flux through various metabolic pathways by coupling the turnover of metabolic enzymes to the levels of key metabolites. We review the current understanding and biological significance of ERAD-mediated regulation of lipid metabolism in mammalian cells.
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Affiliation(s)
- Julian Stevenson
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
| | - Edmond Y Huang
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
| | - James A Olzmann
- Program in Metabolic Biology, Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720;
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99
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Fan J, Li X, Issop L, Culty M, Papadopoulos V. ACBD2/ECI2-Mediated Peroxisome-Mitochondria Interactions in Leydig Cell Steroid Biosynthesis. Mol Endocrinol 2016; 30:763-82. [PMID: 27167610 DOI: 10.1210/me.2016-1008] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Fatty acid metabolism and steroid biosynthesis are 2 major pathways shared by peroxisomes and mitochondria. Both organelles are in close apposition to the endoplasmic reticulum, with which they communicate via interorganelle membrane contact sites to promote cellular signaling and the exchange of ions and lipids. To date, no convincing evidence of the direct contact between peroxisomes and mitochondria was reported in mammalian cells. Hormone-induced, tightly controlled steroid hormone biosynthesis requires interorganelle interactions. Using immunofluorescent staining and live-cell imaging, we found that dibutyryl-cAMP treatment of MA-10 mouse tumor Leydig cells rapidly induces peroxisomes to approach mitochondria and form peroxisome-mitochondrial contact sites/fusion, revealed by the subcellular distribution of the endogenous acyl-coenzyme A-binding domain (ACBD)2/ECI2 isoform A generated by alternative splicing, and further validated using a proximity ligation assay. This event occurs likely via a peroxisome-like structure, which is mediated by peroxisomal and mitochondrial matrix protein import complexes: peroxisomal import receptor peroxisomal biogenesis factor 5 (PEX5), and the mitochondrial import receptor subunit translocase of outer mitochondrial membrane 20 homolog (yeast) protein. Similar results were obtained using the mLTC-1 mouse tumor Leydig cells. Ectopic expression of the ACBD2/ECI2 isoform A in MA-10 cells led to increased basal and hormone-stimulated steroid formation, indicating that ACBD2/ECI2-mediated peroxisomes-mitochondria interactions favor in the exchange of metabolites and/or macromolecules between these 2 organelles in support of steroid biosynthesis. Considering the widespread occurrence of the ACBD2/ECI2 protein, we propose that this protein might serve as a tool to assist in understanding the contact between peroxisomes and mitochondria.
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Affiliation(s)
- Jinjiang Fan
- The Research Institute of the McGill University Health Centre (J.F., X.L., L.I., M.C., V.P.) and Departments of Medicine (J.F., L.I., M.C., V.P.), Biochemistry (X.L., V.P.), and Pharmacology and Therapeutics (M.C., V.P.), McGill University, Montréal, Québec, Canada H4A 3J1
| | - Xinlu Li
- The Research Institute of the McGill University Health Centre (J.F., X.L., L.I., M.C., V.P.) and Departments of Medicine (J.F., L.I., M.C., V.P.), Biochemistry (X.L., V.P.), and Pharmacology and Therapeutics (M.C., V.P.), McGill University, Montréal, Québec, Canada H4A 3J1
| | - Leeyah Issop
- The Research Institute of the McGill University Health Centre (J.F., X.L., L.I., M.C., V.P.) and Departments of Medicine (J.F., L.I., M.C., V.P.), Biochemistry (X.L., V.P.), and Pharmacology and Therapeutics (M.C., V.P.), McGill University, Montréal, Québec, Canada H4A 3J1
| | - Martine Culty
- The Research Institute of the McGill University Health Centre (J.F., X.L., L.I., M.C., V.P.) and Departments of Medicine (J.F., L.I., M.C., V.P.), Biochemistry (X.L., V.P.), and Pharmacology and Therapeutics (M.C., V.P.), McGill University, Montréal, Québec, Canada H4A 3J1
| | - Vassilios Papadopoulos
- The Research Institute of the McGill University Health Centre (J.F., X.L., L.I., M.C., V.P.) and Departments of Medicine (J.F., L.I., M.C., V.P.), Biochemistry (X.L., V.P.), and Pharmacology and Therapeutics (M.C., V.P.), McGill University, Montréal, Québec, Canada H4A 3J1
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100
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Control of plasma membrane lipid homeostasis by the extended synaptotagmins. Nat Cell Biol 2016; 18:504-15. [PMID: 27065097 PMCID: PMC4848133 DOI: 10.1038/ncb3339] [Citation(s) in RCA: 172] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 03/11/2016] [Indexed: 02/08/2023]
Abstract
Acute metabolic changes of plasma membrane (PM) lipids, such as those mediating signaling reactions, are rapidly compensated by homeostatic responses whose molecular basis is poorly understood. Here we show that the Extended-Synaptotagmins (E-Syts), ER proteins which function as PI(4,5)P2 and Ca2+-regulated tethers to the PM, participate in these responses. E-Syts transfer glycerolipids between bilayers in vitro and such transfer requires Ca2+ and their SMP domain, a lipid-harboring module. Genome edited cells lacking E-Syts do not exhibit abnormalities in the major glycerolipids at rest, but display enhanced and sustained accumulation of PM diacylglycerol (DAG) upon PI(4,5)P2 hydrolysis by PLC activation, which can be rescued by expression of E-Syt1, but not by mutant E-Syt1 lacking the SMP domain. The formation of E-Syts-dependent ER-PM tethers in response to stimuli that cleave PI(4,5)P2 and elevate Ca2+ may help reverse accumulation of DAG in the PM by transferring it to the ER for metabolic recycling.
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