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Enrich C, Lu A, Tebar F, Rentero C, Grewal T. Annexins Bridging the Gap: Novel Roles in Membrane Contact Site Formation. Front Cell Dev Biol 2022; 9:797949. [PMID: 35071237 PMCID: PMC8770259 DOI: 10.3389/fcell.2021.797949] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/16/2021] [Indexed: 01/16/2023] Open
Abstract
Membrane contact sites (MCS) are specialized small areas of close apposition between two different organelles that have led researchers to reconsider the dogma of intercellular communication via vesicular trafficking. The latter is now being challenged by the discovery of lipid and ion transfer across MCS connecting adjacent organelles. These findings gave rise to a new concept that implicates cell compartments not to function as individual and isolated entities, but as a dynamic and regulated ensemble facilitating the trafficking of lipids, including cholesterol, and ions. Hence, MCS are now envisaged as metabolic platforms, crucial for cellular homeostasis. In this context, well-known as well as novel proteins were ascribed functions such as tethers, transporters, and scaffolds in MCS, or transient MCS companions with yet unknown functions. Intriguingly, we and others uncovered metabolic alterations in cell-based disease models that perturbed MCS size and numbers between coupled organelles such as endolysosomes, the endoplasmic reticulum, mitochondria, or lipid droplets. On the other hand, overexpression or deficiency of certain proteins in this narrow 10-30 nm membrane contact zone can enable MCS formation to either rescue compromised MCS function, or in certain disease settings trigger undesired metabolite transport. In this "Mini Review" we summarize recent findings regarding a subset of annexins and discuss their multiple roles to regulate MCS dynamics and functioning. Their contribution to novel pathways related to MCS biology will provide new insights relevant for a number of human diseases and offer opportunities to design innovative treatments in the future.
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Affiliation(s)
- Carlos Enrich
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Albert Lu
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Francesc Tebar
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Carles Rentero
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Thomas Grewal
- School of Pharmacy, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
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Sun HY, Chen TY, Tan YC, Wang CH, Young KC. Sterol O-acyltransferase 2 chaperoned by apolipoprotein J facilitates hepatic lipid accumulation following viral and nutrient stresses. Commun Biol 2021; 4:564. [PMID: 33980978 PMCID: PMC8115332 DOI: 10.1038/s42003-021-02093-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 04/06/2021] [Indexed: 11/08/2022] Open
Abstract
The risks of non-alcoholic fatty liver disease (NAFLD) include obese and non-obese stresses such as chronic hepatitis C virus (HCV) infection, but the regulatory determinants remain obscure. Apolipoprotein J (ApoJ) served as an ER-Golgi contact-site chaperone near lipid droplet (LD), facilitating HCV virion production. We hypothesized an interplay between hepatic ApoJ, cholesterol esterification and lipid deposit in response to NAFLD inducers. Exposures of HCV or free-fatty acids exhibited excess LDs along with increased ApoJ expression, whereas ApoJ silencing alleviated hepatic lipid accumulation. Both stresses could concomitantly disperse Golgi, induce closer ApoJ and sterol O-acyltransferase 2 (SOAT2) contacts via the N-terminal intrinsically disordered regions, and increase cholesteryl-ester. Furthermore, serum ApoJ correlated positively with cholesterol and low-density lipoprotein levels in normal glycaemic HCV patients, NAFLD patients and in mice with steatosis. Taken together, hepatic ApoJ might activate SOAT2 to supply cholesteryl-ester for lipid loads, thus providing a therapeutic target of stress-induced steatosis.
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Affiliation(s)
- Hung-Yu Sun
- Department of Biomedical Engineering, College of Biology, Hunan University, Changsha, China
- Institute of Pathogen Biology and Immunology of College of Biology, Hunan Provincial Key Laboratory of Medical Virology, Hunan University, Changsha, China
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Tzu-Ying Chen
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Ching Tan
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chun-Hsiang Wang
- Division of Gastroenterology, Tainan Municipal Hospital, Tainan, Taiwan
| | - Kung-Chia Young
- Department of Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
- Institute of Basic Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
- Center of Infectious Disease and Signaling Research, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
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Kohler V, Büttner S. Remodelling of Nucleus-Vacuole Junctions During Metabolic and Proteostatic Stress. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211016608. [PMID: 34124572 PMCID: PMC7610967 DOI: 10.1177/25152564211016608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/21/2021] [Accepted: 04/21/2021] [Indexed: 12/18/2022]
Abstract
Cellular adaptation to stress and metabolic cues requires a coordinated response of different intracellular compartments, separated by semipermeable membranes. One way to facilitate interorganellar communication is via membrane contact sites, physical bridges between opposing organellar membranes formed by an array of tethering machineries. These contact sites are highly dynamic and establish an interconnected organellar network able to quickly respond to external and internal stress by changing size, abundance and molecular architecture. Here, we discuss recent work on nucleus-vacuole junctions, connecting yeast vacuoles with the nucleus. Appearing as small, single foci in mitotic cells, these contacts expand into one enlarged patch upon nutrient exhaustion and entry into quiescence or can be shaped into multiple large foci essential to sustain viability upon proteostatic stress at the nuclear envelope. We highlight the remarkable plasticity and rapid remodelling of these contact sites upon metabolic or proteostatic stress and their emerging importance for cellular fitness.
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Affiliation(s)
- Verena Kohler
- Department of Molecular Biosciences, The Wenner‐Gren Institute, Stockholm University, Stockholm, Sweden
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner‐Gren Institute, Stockholm University, Stockholm, Sweden
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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Klemm RW. Getting in Touch Is an Important Step: Control of Metabolism at Organelle Contact Sites. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:2515256421993708. [PMID: 37366381 PMCID: PMC10243586 DOI: 10.1177/2515256421993708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 01/19/2021] [Accepted: 01/19/2021] [Indexed: 06/28/2023]
Abstract
Metabolic pathways are often spread over several organelles and need to be functionally integrated by controlled organelle communication. Physical organelle contact-sites have emerged as critical hubs in the regulation of cellular metabolism, but the molecular understanding of mechanisms that mediate formation or regulation of organelle interfaces was until recently relatively limited. Mitochondria are central organelles in anabolic and catabolic pathways and therefore interact with a number of other cellular compartments including the endoplasmic reticulum (ER) and lipid droplets (LDs). An interesting set of recent work has shed new light on the molecular basis forming these contact sites. This brief overview describes the discovery of unanticipated functions of contact sites between the ER, mitochondria and LDs in de novo synthesis of storage lipids of brown and white adipocytes. Interestingly, the factors involved in mediating the interaction between these organelles are subject to unexpected modes of regulation through newly uncovered Phospho-FFAT motifs. These results suggest dynamic regulation of contact sites between organelles and indicate that spatial organization of organelles within the cell contributes to the control of metabolism.
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Affiliation(s)
- Robin W. Klemm
- Department of Physiology,
Anatomy and Genetics, University of Oxford, UK
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Lundquist PK, Shivaiah KK, Espinoza-Corral R. Lipid droplets throughout the evolutionary tree. Prog Lipid Res 2020; 78:101029. [PMID: 32348789 DOI: 10.1016/j.plipres.2020.101029] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 04/11/2020] [Accepted: 04/18/2020] [Indexed: 12/11/2022]
Abstract
Intracellular lipid droplets are utilized for lipid storage and metabolism in organisms as evolutionarily diverse as animals, fungi, plants, bacteria, and archaea. These lipid droplets demonstrate great diversity in biological functions and protein and lipid compositions, yet fundamentally share common molecular and ultrastructural characteristics. Lipid droplet research has been largely fragmented across the diversity of lipid droplet classes and sub-classes. However, we suggest that there is great potential benefit to the lipid community in better integrating the lipid droplet research fields. To facilitate such integration, we survey the protein and lipid compositions, functional roles, and mechanisms of biogenesis across the breadth of lipid droplets studied throughout the natural world. We depict the big picture of lipid droplet biology, emphasizing shared characteristics and unique differences seen between different classes. In presenting the known diversity of lipid droplets side-by-side it becomes necessary to offer for the first time a consistent system of categorization and nomenclature. We propose a division into three primary classes that reflect their sub-cellular location: i) cytoplasmic lipid droplets (CYTO-LDs), that are present in the eukaryotic cytoplasm, ii) prokaryotic lipid droplets (PRO-LDs), that exist in the prokaryotic cytoplasm, and iii) plastid lipid droplets (PL-LDs), that are found in plant plastids, organelles of photosynthetic eukaryotes. Within each class there is a remarkable array of sub-classes displaying various sizes, shapes and compositions. A more integrated lipid droplet research field will provide opportunities to better build on discoveries and accelerate the pace of research in ways that have not been possible.
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Affiliation(s)
- Peter K Lundquist
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA.
| | - Kiran-Kumar Shivaiah
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
| | - Roberto Espinoza-Corral
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
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Affiliation(s)
- Maria Bohnert
- Institute of Cell Dynamics and Imaging, University of Münster
- Cells-in-Motion Cluster of Excellence (EXC 1003—CiM), University of Münster
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Hugenroth M, Bohnert M. Come a little bit closer! Lipid droplet-ER contact sites are getting crowded. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118603. [PMID: 31733263 DOI: 10.1016/j.bbamcr.2019.118603] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/26/2019] [Accepted: 10/29/2019] [Indexed: 12/12/2022]
Abstract
Not so long ago, contact sites between the endoplasmic reticulum (ER) and lipid droplets (LDs) were largely unexplored on a molecular level. In recent years however, numerous proteins have been identified that are enriched or exclusively located at the interfaces between LDs and the ER. These comprise members of protein classes typically found in diverse types of contacts, such as organelle tethers and lipid transfer proteins, but also proteins that have no similarities to known contact site machineries. This structurally heterogeneous group of contact site residents might be required to fulfill unique aspects of LD-ER contact biology, such as de novo LD biogenesis, and maintenance of lipidic connections between LDs and ER. Here, we summarize the current knowledge on the molecular components of this special organelle contact site, and discuss their features and functions.
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Affiliation(s)
- Marie Hugenroth
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany
| | - Maria Bohnert
- Institute of Cell Dynamics and Imaging, University of Münster, Von-Esmarch-Str. 56, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany.
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