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Monteiro-Cardoso VF, Giordano F. Emerging functions of the mitochondria-ER-lipid droplet three-way junction in coordinating lipid transfer, metabolism, and storage in cells. FEBS Lett 2024; 598:1252-1273. [PMID: 38774950 DOI: 10.1002/1873-3468.14893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/18/2024] [Accepted: 04/05/2024] [Indexed: 05/25/2024]
Abstract
Over the past two decades, we have witnessed a growing appreciation for the importance of membrane contact sites (CS) in facilitating direct communication between organelles. CS are tiny regions where the membranes of two organelles meet but do not fuse and allow the transfer of metabolites between organelles, playing crucial roles in the coordination of cellular metabolic activities. The significant advancements in imaging techniques and molecular and cell biology research have revealed that CS are more complex than what originally thought, and as they are extremely dynamic, they can remodel their shape, composition, and functions in accordance with metabolic and environmental changes and can occur between more than two organelles. Here, we describe how recent studies led to the identification of a three-way mitochondria-ER-lipid droplet CS and discuss the emerging functions of these contacts in maintaining lipid storage, homeostasis, and balance. We also summarize the properties and functions of key protein components localized at the mitochondria-ER-lipid droplet interface, with a special focus on lipid transfer proteins. Understanding tripartite CS is essential for unraveling the complexities of inter-organelle communication and cooperation within cells.
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Affiliation(s)
- Vera Filipa Monteiro-Cardoso
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette cedex, France
- Inserm U1280, Gif-sur-Yvette cedex, France
| | - Francesca Giordano
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette cedex, France
- Inserm U1280, Gif-sur-Yvette cedex, France
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2
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Abstract
Cells store excess energy in the form of lipid droplets (LDs), a specialized sub-compartment of the endoplasmic reticulum (ER) network. The lipodystrophy protein seipin is a key player in LD biogenesis and ER-LD contact site maintenance. Recent structural and in silico studies have started to shed light on the molecular function of seipin as a LD nucleator in early LD biogenesis, whilst new cell biological work implies a role for seipin in ER-mitochondria contact sites and calcium metabolism. In this minireview, I discuss recent insights into the molecular function of seipin.
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Affiliation(s)
- Veijo T. Salo
- Structural and Computational Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
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3
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Lukmantara I, Chen F, Mak HY, Zadoorian A, Du X, Xiao FN, Norris DM, Pandzic E, Whan R, Zhong Q, Yang H. PI(3)P and DFCP1 regulate the biogenesis of lipid droplets. Mol Biol Cell 2022; 33:ar131. [PMID: 36129766 PMCID: PMC9727793 DOI: 10.1091/mbc.e22-07-0279] [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: 02/04/2023] Open
Abstract
The biogenesis of lipid droplets (LDs), key organelles for cellular lipid storage and homeostasis, remains poorly understood. Seipin is essential to normal LD biogenesis but exactly how it regulates LD initiation remains to be elucidated. Our previous results suggested that seipin may bind anionic phospholipids such as PI(3)P. Here, we investigate whether PI(3)P is functionally linked to seipin and whether PI(3)P can also impact LD biogenesis. In seipin-deficient cells, there were enlarged PI(3)P puncta where its effector, DFCP1, also appeared to congregate. Reducing cellular PI(3)P partially rescued the defective LD initiation caused by seipin deficiency. Increasing PI(3)P impeded the lipidation of nascent LDs. We further demonstrated that DFCP1 localized to LDs and facilitated the efficient lipidation of nascent LDs. However, the normal function and localization of DFCP1 were disrupted when cellular PI(3)P homeostasis was perturbed. Our results thus identify PI(3)P as a novel regulator of LD initiation and suggest that PI(3)P may impact the biogenesis of LDs through DFCP1.
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Affiliation(s)
- Ivan Lukmantara
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Fang Chen
- Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200240, China
| | - Hoi Yin Mak
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Armella Zadoorian
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Fanqian Nicole Xiao
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Dougall MacMurray Norris
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Elvis Pandzic
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, NSW 2052, Australia
| | - Renee Whan
- Katharina Gaus Light Microscopy Facility, Mark Wainwright Analytical Center, University of New South Wales, Sydney, NSW 2052, Australia
| | - Qing Zhong
- Key Laboratory of Cell Differentiation and Apoptosis of the Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200240, China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia,*Address correspondence to: Hongyuan Yang ()
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4
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Zhou H, Li J, Su H, Li J, Lydic TA, Young ME, Chen W. BSCL2/Seipin deficiency in hearts causes cardiac energy deficit and dysfunction via inducing excessive lipid catabolism. Clin Transl Med 2022; 12:e736. [PMID: 35384404 PMCID: PMC8982503 DOI: 10.1002/ctm2.736] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 01/26/2022] [Accepted: 01/29/2022] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Heart failure (HF) is one of the leading causes of death worldwide and is associated with cardiac metabolic perturbations. Human Type 2 Berardinelli-Seip Congenital Lipodystrophy (BSCL2) disease is caused by mutations in the BSCL2 gene. Global lipodystrophic Bscl2-/- mice exhibit hypertrophic cardiomyopathy with reduced cardiac steatosis. Whether BSCL2 plays a direct role in regulating cardiac substrate metabolism and/or contractile function remains unknown. METHODS We generated mice with cardiomyocyte-specific deletion of Bscl2 (Bscl2cKO ) and studied their cardiac substrate utilisation, bioenergetics, lipidomics and contractile function under baseline or after either a treatment regimen using fatty acid oxidation (FAO) inhibitor trimetazidine (TMZ) or a prevention regimen with high-fat diet (HFD) feeding. Mice with partial ATGL deletion and cardiac-specific deletion of Bscl2 were also generated followed by cardiac phenotyping. RESULTS Different from hypertrophic cardiomyopathy in Bscl2-/- mice, mice with cardiac-specific deletion of Bscl2 developed systolic dysfunction with dilation. Myocardial BSCL2 deletion led to elevated ATGL expression and FAO along with reduced cardiac lipid contents. Cardiac dysfunction in Bscl2cKO mice was independent of mitochondrial dysfunction and oxidative stress, but associated with decreased metabolic reserve and ATP levels. Importantly, cardiac dysfunction in Bscl2cKO mice could be partially reversed by FAO inhibitor TMZ, or prevented by genetic abolishment of one ATGL allele or HFD feeding. Lipidomic analysis further identified markedly reduced glycerolipids, glycerophospholipids, NEFA and acylcarnitines in Bscl2cKO hearts, which were partially normalised by TMZ or HFD. CONCLUSIONS We identified a new form of cardiac dysfunction with excessive lipid utilisation which ultimately causes cardiac substrate depletion and bioenergetics failure. Our findings also uncover a crucial role of BSCL2 in controlling cardiac lipid catabolism and contractile function and provide novel insights into metabolically treating energy-starved HF using FAO inhibitor or HFD.
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Affiliation(s)
- Hongyi Zhou
- Department of PhysiologyMedical College of Georgia at Augusta UniversityAugustaGeorgiaUSA
| | - Jie Li
- Vascular Biology CenterMedical College of Georgia at Augusta UniversityAugustaGeorgiaUSA
| | - Huabo Su
- Vascular Biology CenterMedical College of Georgia at Augusta UniversityAugustaGeorgiaUSA
| | - Ji Li
- Department of SurgeryMorsani College of MedicineUniversity of South FloridaTampaFloridaUSA
| | - Todd A. Lydic
- Department of PhysiologyMichigan State UniversityEast LansingMichiganUSA
| | - Martin E Young
- Department of MedicineUniversity of Alabama at BirminghamBirminghamAlabamaUSA
| | - Weiqin Chen
- Department of PhysiologyMedical College of Georgia at Augusta UniversityAugustaGeorgiaUSA
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5
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Schneiter R, Choudhary V. Seipin collaborates with the ER membrane to control the sites of lipid droplet formation. Curr Opin Cell Biol 2022; 75:102070. [PMID: 35306312 PMCID: PMC7615794 DOI: 10.1016/j.ceb.2022.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 12/24/2022]
Abstract
Most cells store metabolic energy in lipid droplets (LDs). LDs are composed of a hydrophobic core, covered by a phospholipid monolayer, and functionalized by a specific set of proteins. Formation of LDs takes place in the endoplasmic reticulum (ER), where neutral lipid biosynthetic enzymes are located. Recent evidence indicate that this process is confined to specific ER subdomains, where proteins meet to initiate LD assembly. The lipodystrophy protein Seipin, is emerging as a major coordinator of LD biogenesis. Seipin forms a large oligomeric toroidal structure, which traps neutral lipids to promote LD nucleation. Here, we discuss the role of LD biogenesis factors that associate with Seipin to assemble functional LDs.
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Affiliation(s)
- Roger Schneiter
- University of Fribourg, Department of Biology, 1700, Fribourg, Switzerland.
| | - Vineet Choudhary
- All India Institute of Medical Sciences (AIIMS), Department of Biotechnology, New Delhi, 110029, India.
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McPhee MJ, Salsman J, Foster J, Thompson J, Mathavarajah S, Dellaire G, Ridgway ND. Running 'LAPS' Around nLD: Nuclear Lipid Droplet Form and Function. Front Cell Dev Biol 2022; 10:837406. [PMID: 35178392 PMCID: PMC8846306 DOI: 10.3389/fcell.2022.837406] [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: 12/16/2021] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
The nucleus harbours numerous protein subdomains and condensates that regulate chromatin organization, gene expression and genomic stress. A novel nuclear subdomain that is formed following exposure of cells to excess fatty acids is the nuclear lipid droplet (nLD), which is composed of a neutral lipid core surrounded by a phospholipid monolayer and associated regulatory and lipid biosynthetic enzymes. While structurally resembling cytoplasmic LDs, nLDs are formed by distinct but poorly understood mechanisms that involve the emergence of lipid droplets from the lumen of the nucleoplasmic reticulum and de novo lipid synthesis. Luminal lipid droplets that emerge into the nucleoplasm do so at regions of the inner nuclear membrane that become enriched in promyelocytic leukemia (PML) protein. The resulting nLDs that retain PML on their surface are termed lipid-associated PML structures (LAPS), and are distinct from canonical PML nuclear bodies (NB) as they lack key proteins and modifications associated with these NBs. PML is a key regulator of nuclear signaling events and PML NBs are sites of gene regulation and post-translational modification of transcription factors. Therefore, the subfraction of nLDs that form LAPS could regulate lipid stress responses through their recruitment and retention of the PML protein. Both nLDs and LAPS have lipid biosynthetic enzymes on their surface suggesting they are active sites for nuclear phospholipid and triacylglycerol synthesis as well as global lipid regulation. In this review we have summarized the current understanding of nLD and LAPS biogenesis in different cell types, their structure and composition relative to other PML-associated cellular structures, and their role in coordinating a nuclear response to cellular overload of fatty acids.
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Affiliation(s)
- Michael J McPhee
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, NS, Canada
| | - Jason Foster
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Jordan Thompson
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | | | - Graham Dellaire
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.,Department of Pathology, Dalhousie University, Halifax, NS, Canada
| | - Neale D Ridgway
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.,Department of Pediatrics, Dalhousie University, Halifax, NS, Canada
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7
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Magré J, Prieur X. Seipin Deficiency as a Model of Severe Adipocyte Dysfunction: Lessons from Rodent Models and Teaching for Human Disease. Int J Mol Sci 2022; 23:740. [PMID: 35054926 PMCID: PMC8775404 DOI: 10.3390/ijms23020740] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/06/2022] [Accepted: 01/07/2022] [Indexed: 02/05/2023] Open
Abstract
Obesity prevalence is increasing worldwide, leading to cardiometabolic morbidities. Adipocyte dysfunction, impairing white adipose tissue (WAT) expandability and metabolic flexibility, is central in the development of obesity-related metabolic complications. Rare syndromes of lipodystrophy characterized by an extreme paucity of functional adipose tissue should be considered as primary adipocyte dysfunction diseases. Berardinelli-Seip congenital lipodystrophy (BSCL) is the most severe form with a near absence of WAT associated with cardiometabolic complications such as insulin resistance, liver steatosis, dyslipidemia, and cardiomyopathy. Twenty years ago, mutations in the BSCL2 gene have been identified as the cause of BSCL in human. BSCL2 encodes seipin, an endoplasmic reticulum (ER) anchored protein whose function was unknown back then. Studies of seipin knockout mice or rats demonstrated how seipin deficiency leads to severe lipodystrophy and to cardiometabolic complications. At the cellular levels, seipin is organized in multimers that are particularly enriched at ER/lipid droplet and ER/mitochondria contact sites. Seipin deficiency impairs both adipocyte differentiation and mature adipocyte maintenance. Experiments using adipose tissue transplantation in seipin knockout mice and tissue-specific deletion of seipin have provided a large body of evidence that liver steatosis, cardiomyopathy, and renal injury, classical diabetic complications, are all consequences of lipodystrophy. Rare adipocyte dysfunctions such as in BSCL are the key paradigm to unravel the pathways that control adipocyte homeostasis. The knowledge gathered through the study of these pathologies may bring new strategies to maintain and improve adipose tissue expandability.
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Affiliation(s)
| | - Xavier Prieur
- Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, L’institut du Thorax, Université de Nantes, F-44000 Nantes, France;
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8
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Seipin localizes at endoplasmic-reticulum-mitochondria contact sites to control mitochondrial calcium import and metabolism in adipocytes. Cell Rep 2022; 38:110213. [PMID: 35021082 DOI: 10.1016/j.celrep.2021.110213] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 10/11/2021] [Accepted: 12/14/2021] [Indexed: 12/31/2022] Open
Abstract
Deficiency of the endoplasmic reticulum (ER) protein seipin results in generalized lipodystrophy by incompletely understood mechanisms. Here, we report mitochondrial abnormalities in seipin-deficient patient cells. A subset of seipin is enriched at ER-mitochondria contact sites (MAMs) in human and mouse cells and localizes in the vicinity of calcium regulators SERCA2, IP3R, and VDAC. Seipin association with MAM calcium regulators is stimulated by fasting-like stimuli, while seipin association with lipid droplets is promoted by lipid loading. Acute seipin removal does not alter ER calcium stores but leads to defective mitochondrial calcium import accompanied by a widespread reduction in Krebs cycle metabolites and ATP levels. In mice, inducible seipin deletion leads to mitochondrial dysfunctions preceding the development of metabolic complications. Together, these data suggest that seipin controls mitochondrial energy metabolism by regulating mitochondrial calcium influx at MAMs. In seipin-deficient adipose tissue, reduced ATP production compromises adipocyte properties, contributing to lipodystrophy pathogenesis.
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9
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Hello from the other side: Membrane contact of lipid droplets with other organelles and subsequent functional implications. Prog Lipid Res 2021; 85:101141. [PMID: 34793861 DOI: 10.1016/j.plipres.2021.101141] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/10/2021] [Accepted: 11/10/2021] [Indexed: 02/06/2023]
Abstract
Lipid droplets (LDs) are ubiquitous organelles that play crucial roles in response to physiological and environmental cues. The identification of several neutral lipid synthesizing and regulatory protein complexes have propelled significant advance on the mechanisms of LD biogenesis in the endoplasmic reticulum (ER). Increasing evidence suggests that distinct proteins and regulatory factors, which localize to membrane contact sites (MCS), are involved not only in interorganellar lipid exchange and transport, but also function in other important cellular processes, including autophagy, mitochondrial dynamics and inheritance, ion signaling and inter-regulation of these MCS. More and more tethers and molecular determinants are associated to MCS and to a diversity of cellular and pathophysiological processes, demonstrating the dynamics and importance of these junctions in health and disease. The conjugation of lipids with proteins in supramolecular complexes is known to be paramount for many biological processes, namely membrane biosynthesis, cell homeostasis, regulation of organelle division and biogenesis, and cell growth. Ultimately, this physical organization allows the contact sites to function as crucial metabolic hubs that control the occurrence of chemical reactions. This leads to biochemical and metabolite compartmentalization for the purposes of energetic efficiency and cellular homeostasis. In this review, we will focus on the structural and functional aspects of LD-organelle interactions and how they ensure signaling exchange and metabolites transfer between organelles.
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10
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Rao MJ, Goodman JM. Seipin: harvesting fat and keeping adipocytes healthy. Trends Cell Biol 2021; 31:912-923. [PMID: 34215489 DOI: 10.1016/j.tcb.2021.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/29/2021] [Accepted: 06/03/2021] [Indexed: 01/17/2023]
Abstract
Seipin is a key protein in the assembly of cytoplasmic lipid droplets (cLDs) and their maintenance at endoplasmic reticulum (ER)-LD junctions; the absence of seipin results in generalized lipodystrophy. How seipin mediates LD dynamics and prevents lipodystrophy are not well understood. New evidence suggests that seipin attracts triglyceride monomers from the ER to sites of droplet formation. By contrast, seipin may not be directly involved in the assembly of nuclear LDs and may actually suppress their formation at a distance. Seipin promotes adipogenesis, but lipodystrophy may also involve postadipogenic effects. We hypothesize that among these are a cycle of runaway lipolysis and lipotoxicity caused by aberrant LDs, resulting in a depletion of fat stores and a failure of adipose and other cells to thrive.
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Affiliation(s)
- Monala Jayaprakash Rao
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX 75390-9041, USA
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX 75390-9041, USA.
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11
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Guéguen N, Le Moigne D, Amato A, Salvaing J, Maréchal E. Lipid Droplets in Unicellular Photosynthetic Stramenopiles. FRONTIERS IN PLANT SCIENCE 2021; 12:639276. [PMID: 33968100 PMCID: PMC8100218 DOI: 10.3389/fpls.2021.639276] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 03/17/2021] [Indexed: 06/12/2023]
Abstract
The Heterokonta or Stramenopile phylum comprises clades of unicellular photosynthetic species, which are promising for a broad range of biotechnological applications, based on their capacity to capture atmospheric CO2 via photosynthesis and produce biomolecules of interest. These molecules include triacylglycerol (TAG) loaded inside specific cytosolic bodies, called the lipid droplets (LDs). Understanding TAG production and LD biogenesis and function in photosynthetic stramenopiles is therefore essential, and is mostly based on the study of a few emerging models, such as the pennate diatom Phaeodactylum tricornutum and eustigmatophytes, such as Nannochloropsis and Microchloropsis species. The biogenesis of cytosolic LD usually occurs at the level of the endoplasmic reticulum. However, stramenopile cells contain a complex plastid deriving from a secondary endosymbiosis, limited by four membranes, the outermost one being connected to the endomembrane system. Recent cell imaging and proteomic studies suggest that at least some cytosolic LDs might be associated to the surface of the complex plastid, via still uncharacterized contact sites. The carbon length and number of double bonds of the acyl groups contained in the TAG molecules depend on their origin. De novo synthesis produces long-chain saturated or monounsaturated fatty acids (SFA, MUFA), whereas subsequent maturation processes lead to very long-chain polyunsaturated FA (VLC-PUFA). TAG composition in SFA, MUFA, and VLC-PUFA reflects therefore the metabolic context that gave rise to the formation of the LD, either via an early partitioning of carbon following FA de novo synthesis and/or a recycling of FA from membrane lipids, e.g., plastid galactolipids or endomembrane phosphor- or betaine lipids. In this review, we address the relationship between cytosolic LDs and the complex membrane compartmentalization within stramenopile cells, the metabolic routes leading to TAG accumulation, and the physiological conditions that trigger LD production, in response to various environmental factors.
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12
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Bscl2 Deficiency Does Not Directly Impair the Innate Immune Response in a Murine Model of Generalized Lipodystrophy. J Clin Med 2021; 10:jcm10030441. [PMID: 33498782 PMCID: PMC7865406 DOI: 10.3390/jcm10030441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/13/2021] [Accepted: 01/15/2021] [Indexed: 11/28/2022] Open
Abstract
Congenital Generalized Lipodystrophy type 2 (CGL2) is the most severe form of lipodystrophy and is caused by mutations in the BSCL2 gene. Affected patients exhibit a near complete lack of adipose tissue and suffer severe metabolic disease. A recent study identified infection as a major cause of death in CGL2 patients, leading us to examine whether Bscl2 loss could directly affect the innate immune response. We generated a novel mouse model selectively lacking Bscl2 in the myeloid lineage (LysM-B2KO) and also examined the function of bone-marrow-derived macrophages (BMDM) isolated from global Bscl2 knockout (SKO) mice. LysM-B2KO mice failed to develop lipodystrophy and metabolic disease, providing a model to study the direct role of Bscl2 in myeloid lineage cells. Lipopolysaccharide-mediated stimulation of inflammatory cytokines was not impaired in LysM-B2KO mice or in BMDM isolated from either LysM-B2KO or SKO mice. Additionally, intracellular fate and clearance of bacteria in SKO BMDM challenged with Staphylococcus aureus was indistinguishable from that in BMDM isolated from littermate controls. Overall, our findings reveal that selective Bscl2 deficiency in macrophages does not critically impact the innate immune response to infection. Instead, an increased susceptibility to infection in CGL2 patients is likely to result from severe metabolic disease.
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13
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Thiam AR, Ikonen E. Lipid Droplet Nucleation. Trends Cell Biol 2020; 31:108-118. [PMID: 33293168 DOI: 10.1016/j.tcb.2020.11.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/11/2020] [Accepted: 11/12/2020] [Indexed: 02/06/2023]
Abstract
All living organisms can make lipid droplets (LDs), intracellular oil-in-water droplets, surrounded by a phospholipid and protein monolayer. LDs are at the nexus of cellular lipid metabolism and function in diverse biological processes. During the past decade, multidisciplinary approaches have shed light on LD assembly steps from the endoplasmic reticulum (ER): nucleation, growth, budding, and formation of a separate organelle. However, the molecular mechanisms underpinning these steps remain elusive. In this review, we focus on the nucleation step, defining where and how LD assembly is initiated. We present how membrane biophysical and physicochemical properties control this step and how proteins act on it to orchestrate LD biogenesis.
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Affiliation(s)
- Abdou Rachid Thiam
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, F-75005 Paris, France.
| | - Elina Ikonen
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki, 00290 Helsinki, Finland; Minerva Foundation Institute for Medical Research, 00290 Helsinki, Finland.
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14
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Jin Y, Tan Y, Zhao P, Ren Z. SEIPIN: A Key Factor for Nuclear Lipid Droplet Generation and Lipid Homeostasis. Int J Mol Sci 2020; 21:ijms21218208. [PMID: 33147895 PMCID: PMC7663086 DOI: 10.3390/ijms21218208] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 12/28/2022] Open
Abstract
Lipid homeostasis is essential for normal cell physiology. Generally, lipids are stored in a lipid droplet (LD), a ubiquitous organelle consisting of a neutral lipid core and a single layer of phospholipid membrane. It is thought that LDs are generated from the endoplasmic reticulum and then released into the cytosol. Recent studies indicate that LDs can exist in the nucleus, where they play an important role in the maintenance of cell phospholipid homeostasis. However, the details of nuclear lipid droplet (nLD) generation have not yet been clearly characterized. SEIPIN is a nonenzymatic protein encoded by the Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2) gene. It is associated with lipodystrophy diseases. Many recent studies have indicated that SEIPIN is essential for LDs generation. Here, we review much of this research in an attempt to explain the role of SEIPIN in nLD generation. From an integrative perspective, we conclude by proposing a theoretical model to explain how SEIPIN might participate in maintaining homeostasis of lipid metabolism.
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Affiliation(s)
- Yi Jin
- Key Laboratory of Agriculture Animal Genetics, Breeding and Reproduction of the Ministry of Education & Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture and Rural Affairs, College of Animal Science, Huazhong Agricultural University, Wuhan 430070, Hubei, China; (Y.J.); (Y.T.); (P.Z.)
- Bio-Medical Center of Huazhong Agricultural University, Wuhan 430070, Hubei, China
| | - Yanjie Tan
- Key Laboratory of Agriculture Animal Genetics, Breeding and Reproduction of the Ministry of Education & Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture and Rural Affairs, College of Animal Science, Huazhong Agricultural University, Wuhan 430070, Hubei, China; (Y.J.); (Y.T.); (P.Z.)
- Institute of Biomedical Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Sciences, Shandong Normal University, Jinan 250014, Shandong, China
| | - Pengxiang Zhao
- Key Laboratory of Agriculture Animal Genetics, Breeding and Reproduction of the Ministry of Education & Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture and Rural Affairs, College of Animal Science, Huazhong Agricultural University, Wuhan 430070, Hubei, China; (Y.J.); (Y.T.); (P.Z.)
| | - Zhuqing Ren
- Key Laboratory of Agriculture Animal Genetics, Breeding and Reproduction of the Ministry of Education & Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture and Rural Affairs, College of Animal Science, Huazhong Agricultural University, Wuhan 430070, Hubei, China; (Y.J.); (Y.T.); (P.Z.)
- Bio-Medical Center of Huazhong Agricultural University, Wuhan 430070, Hubei, China
- Correspondence:
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Salo VT, Hölttä-Vuori M, Ikonen E. Seipin-Mediated Contacts as Gatekeepers of Lipid Flux at the Endoplasmic Reticulum–Lipid Droplet Nexus. ACTA ACUST UNITED AC 2020. [DOI: 10.1177/2515256420945820] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Lipid droplets (LDs) are dynamic cellular hubs of lipid metabolism. While LDs contact a plethora of organelles, they have the most intimate relationship with the endoplasmic reticulum (ER). Indeed, LDs are initially assembled at specialized ER subdomains, and recent work has unraveled an increasing array of proteins regulating ER-LD contacts. Among these, seipin, a highly conserved lipodystrophy protein critical for LD growth and adipogenesis, deserves special attention. Here, we review recent insights into the role of seipin in LD biogenesis and as a regulator of ER-LD contacts. These studies have also highlighted the evolving concept of ER and LDs as a functional continuum for lipid partitioning and pinpointed a role for seipin at the ER-LD nexus in controlling lipid flux between these compartments.
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Affiliation(s)
- Veijo T. Salo
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Maarit Hölttä-Vuori
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Elina Ikonen
- Department of Anatomy and Stem Cells and Metabolism Research Program, Faculty of Medicine, University of Helsinki
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
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16
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Lee J, Salsman J, Foster J, Dellaire G, Ridgway ND. Lipid-associated PML structures assemble nuclear lipid droplets containing CCTα and Lipin1. Life Sci Alliance 2020; 3:3/8/e202000751. [PMID: 32461215 PMCID: PMC7266991 DOI: 10.26508/lsa.202000751] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 05/13/2020] [Accepted: 05/14/2020] [Indexed: 11/24/2022] Open
Abstract
PML proteins assemble into noncanonical lipid-associated PML structures (LAPS) on nuclear lipid droplets, which recruit CCTα and Lipin1 for the synthesis of phosphatidylcholine and triacylglycerol. Nuclear lipid droplets (nLDs) form on the inner nuclear membrane by a mechanism involving promyelocytic leukemia (PML), the protein scaffold of PML nuclear bodies. We report that PML structures on nLDs in oleate-treated U2OS cells, referred to as lipid-associated PML structures (LAPS), differ from canonical PML nuclear bodies by the relative absence of SUMO1, SP100, and DAXX. These nLDs were also enriched in CTP:phosphocholine cytidylyltransferase α (CCTα), the phosphatidic acid phosphatase Lipin1, and DAG. Translocation of CCTα onto nLDs was mediated by its α-helical M-domain but was not correlated with its activator DAG. High-resolution imaging revealed that CCTα and LAPS occupied distinct polarized regions on nLDs. PML knockout U2OS (PML KO) cells lacking LAPS had a 40–50% reduction in nLDs with associated CCTα, and residual nLDs were almost devoid of Lipin1 and DAG. As a result, phosphatidylcholine and triacylglycerol synthesis was inhibited in PML KO cells. We conclude that in response to excess exogenous fatty acids, LAPS are required to assemble nLDs that are competent to recruit CCTα and Lipin1.
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Affiliation(s)
- Jonghwa Lee
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, Canada
| | - Jason Foster
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Graham Dellaire
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada .,Department of Pathology, Dalhousie University, Halifax, Canada
| | - Neale D Ridgway
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada .,Department of Pediatrics, Dalhousie University, Halifax, Canada
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17
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Renne MF, Klug YA, Carvalho P. Lipid droplet biogenesis: A mystery "unmixing"? Semin Cell Dev Biol 2020; 108:14-23. [PMID: 32192830 DOI: 10.1016/j.semcdb.2020.03.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 03/06/2020] [Accepted: 03/07/2020] [Indexed: 12/19/2022]
Abstract
Lipid droplets (LDs) are versatile organelles with central roles in lipid and energy metabolism in all eukaryotes. They primarily buffer excess fatty acids by storing them as neutral lipids, mainly triglycerides and steryl esters. The neutral lipids form a core, surrounded by a unique phospholipid monolayer coated with a defined set of proteins. Thus, the architecture of LDs sets them apart from all other membrane-bound organelles. The origin of LDs remained controversial for a long time. However, it has become clear that their biogenesis occurs at the endoplasmic reticulum (ER) and is a lipid driven process. LD formation is intiatied by the demixing of neutral lipids from membrane phospholipids, leading to the formation of a neutral lipid "lens" like structure between the leaflets of the ER bilayer. As this lens grows, it buds out of the membrane towards the cytosol to give rise to a LD. Recent biophysical and cell biological experiments indicate that LD biogenesis occurs at specific ER domains. These domains are enriched in various proteins required for normal LD formation and possibly have a lipid composition distinct from the remaining ER membrane. Here, we describe the prevailing model for LD formation and discuss recent insights on how proteins organize ER domains involved in LD biogenesis.
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Affiliation(s)
- Mike F Renne
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK.
| | - Yoel A Klug
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK.
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK.
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18
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Zhou H, Xu C, Lee H, Yoon Y, Chen W. Berardinelli-Seip congenital lipodystrophy 2/SEIPIN determines brown adipose tissue maintenance and thermogenic programing. Mol Metab 2020; 36:100971. [PMID: 32246911 PMCID: PMC7136632 DOI: 10.1016/j.molmet.2020.02.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2019] [Revised: 02/18/2020] [Accepted: 02/25/2020] [Indexed: 01/12/2023] Open
Abstract
Objective Understanding the mechanisms that control brown adipose tissue (BAT) mass and functionality is crucial for our understanding of how the disruption of energy homeostasis leads to obesity. Bernerdinali Seip Congenital Lipodystrophy (BSCL) type 2 (BSCL2, a.k.a. SEIPIN), a lipodystrophy-associated protein, has been shown to not be required for brown adipogenesis, but it has been shown to be essential for perinatal BAT development. However, its role in mature BAT maintenance and thermogenic programing remains poorly understood. Methods We subjected Bscl2f/f and Bscl2UCP1-BKO (BKO) mice with a brown adipose-specific loss of BSCL2 through UCP1 promoter-driven Cre to environmental, pharmacological and diet interventions to challenge BAT functionality and reprogramming. We carried out physiological, molecular and transcriptomic analyses of BAT. Results The deletion of BSCL2 in mature brown adipocytes increased sympathetic nervous system-independent cAMP/protein kinase A (PKA) signaling in BAT. Such activation reduced BAT triglyceride content and mass and was sufficient to reduce plasma triglyceride, but not enough to combat thermoneutral and high fat diet-induced obesity. Surprisingly, BKO mice displayed an impaired response to acute and chronic cold challenges despite cAMP/PKA activation. When subjected to chronic cold exposure or the administration of a β3-adrenergic agonist, CL 316,243, BKO mice failed to induce BAT recruitment and underwent dramatic brown adipocyte loss. Transcriptomic analysis revealed pathological BAT remodeling with inflammation and fibrosis, which was further exacerbated by a chronic thermogenic challenge in BKO mice. Mechanistically, we found abnormal mitochondrial shapes and function in BAT of BKO mice housed at 21 °C; as well as mitochondrial DNA depletion and necroptotic-mediated brown adipocyte death after chronic thermogenic insult. Conclusion BSCL2-mediated lipid catabolism within BAT is crucial for mature brown adipocyte function and survival both during times of activation and quiescence. BSCL2 is an important regulator of mature brown adipocyte mitochondrial metabolism, necroptosis and thus adaptive thermogenesis. Mature BAT-specific loss of BSCL2 (Bscl2UCP1-BKO) activates SNS-independent cAMP/PKA signaling. Bscl2UCP1-BKO increases BAT mitochondrial fission and uncoupling. Bscl2UCP1-BKO reduces plasma triglyceride but not adiposity under thermoneutrality or high fat diet. Bscl2UCP1-BKO blunts BAT reprograming and causes cold intolerance. BSCL2 deletion exposes brown adipocyte to necroptosis under chronic thermogenic stress.
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Affiliation(s)
- Hongyi Zhou
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA
| | - Cheng Xu
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA
| | - Hakjoo Lee
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA
| | - Yisang Yoon
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA
| | - Weiqin Chen
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA 30912, USA.
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19
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Sim MFM, Persiani E, Talukder MMU, Mcilroy GD, Roumane A, Edwardson JM, Rochford JJ. Oligomers of the lipodystrophy protein seipin may co-ordinate GPAT3 and AGPAT2 enzymes to facilitate adipocyte differentiation. Sci Rep 2020; 10:3259. [PMID: 32094408 PMCID: PMC7039881 DOI: 10.1038/s41598-020-59982-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 01/27/2020] [Indexed: 12/13/2022] Open
Abstract
Seipin deficiency causes severe congenital generalized lipodystrophy (CGL) and metabolic disease. However, how seipin regulates adipocyte development and function remains incompletely understood. We previously showed that seipin acts as a scaffold protein for AGPAT2, whose disruption also causes CGL. More recently, seipin has been reported to promote adipogenesis by directly inhibiting GPAT3, leading to the suggestion that GPAT inhibitors could offer novel treatments for CGL. Here we investigated the interactions between seipin, GPAT3 and AGPAT2. We reveal that seipin and GPAT3 associate via direct interaction and that seipin can simultaneously bind GPAT3 and AGPAT2. Inhibiting the expression of seipin, AGPAT2 or GPAT3 led to impaired induction of early markers of adipocyte differentiation in cultured cells. However, consistent with normal adipose mass in GPAT3-null mice, GPAT3 inhibition did not prevent the formation of mature adipocytes. Nonetheless, loss of GPAT3 in seipin-deficient preadipocytes exacerbated the failure of adipogenesis in these cells. Thus, our data indicate that GPAT3 plays a modest positive role in adipogenesis and argue against the potential of GPAT inhibitors to rescue white adipose tissue mass in CGL2. Overall, our study reveals novel mechanistic insights regarding the molecular pathogenesis of severe lipodystrophy caused by mutations in either seipin or AGPAT2.
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Affiliation(s)
- M F Michelle Sim
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK
| | - Elisa Persiani
- Rowett Institute and the Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | | | - George D Mcilroy
- Rowett Institute and the Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | - Ahlima Roumane
- Rowett Institute and the Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
| | | | - Justin J Rochford
- University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK. .,Rowett Institute and the Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
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20
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The biogenesis of lipid droplets: Lipids take center stage. Prog Lipid Res 2019; 75:100989. [PMID: 31351098 DOI: 10.1016/j.plipres.2019.100989] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 05/21/2019] [Accepted: 06/27/2019] [Indexed: 11/20/2022]
Abstract
Lipid droplets (LDs) are multi-functional cellular organelles that store energy, and regulate many aspects of cell physiology. However, our understanding of the biogenesis of LDs remains very limited. Originating from the endoplasmic reticulum (ER), LDs are highly unique organelles in that each LD is bounded by a monolayer of amphipathic lipids. Recent progress has unveiled critical roles of non-bilayer lipids in LD formation. For instance, non-bilayer lipids such as lysophospholipids, diacylglycerol and phosphatidic acid (PA) can impact the curvature, surface and line tension of the ER, thereby impacting LD biogenesis. Two well-known regulators of LD formation, FIT2/FITM2 and seipin, have both been implicated in controlling the metabolism and/or distribution of non-bilayer lipids. We summarize and integrate these recent advances and propose that non-bilayer lipids may play a critical role in each step of LD biogenesis.
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21
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Zhou H, Lei X, Yan Y, Lydic T, Li J, Weintraub NL, Su H, Chen W. Targeting ATGL to rescue BSCL2 lipodystrophy and its associated cardiomyopathy. JCI Insight 2019; 5:129781. [PMID: 31185001 DOI: 10.1172/jci.insight.129781] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Mutations in BSCL2 gene underlie human type 2 Berardinelli-Seip Congenital Lipodystrophy (BSCL2) disease. Global Bscl2-/- mice recapitulate human BSCL2 lipodystrophy and develop insulin resistance and hypertrophic cardiomyopathy. The pathological mechanisms underlying the development of lipodystrophy and cardiomyopathy in BSCL2 are controversial. Here we report that Bscl2-/- mice develop cardiac hypertrophy due to increased basal IGF1 receptor (IGF1R)-mediated PI3K/AKT signaling. Bscl2-/- hearts exhibited increased adipose triglyceride lipase (ATGL) protein stability and expression causing drastic reduction of glycerolipids. Excessive fatty acid oxidation was overt in Bscl2-/- hearts, partially attributing to the hyperacetylation of cardiac mitochondrial proteins. Intriguingly, pharmacological inhibition or genetic inactivation of ATGL could rescue adipocyte differentiation and lipodystrophy in Bscl2-/- cells and mice. Restoring a small portion of fat mass by ATGL partial deletion in Bscl2-/- mice not only reversed the systemic insulin resistance, but also ameliorated cardiac protein hyperacetylation, normalized cardiac substrate metabolism and improved contractile function. Collectively, our study uncovers novel pathways underlying lipodystrophy-induced cardiac hypertrophy and metabolic remodeling and pinpoints ATGL as a downstream target of BSCL2 in regulating the development of lipodystrophy and its associated cardiomyopathy.
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Affiliation(s)
- Hongyi Zhou
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Xinnuo Lei
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Yun Yan
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Todd Lydic
- Department of Physiology, Michigan State University, East Lansing, Michigan, USA
| | - Jie Li
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Neal L Weintraub
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Huabo Su
- Vascular Biology Center, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Weiqin Chen
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
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22
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Nettebrock NT, Bohnert M. Born this way - Biogenesis of lipid droplets from specialized ER subdomains. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158448. [PMID: 31028912 DOI: 10.1016/j.bbalip.2019.04.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 12/20/2018] [Accepted: 01/06/2019] [Indexed: 01/21/2023]
Abstract
Both the endoplasmic reticulum (ER) and lipid droplets (LDs) are key players in lipid handling. In addition to this functional connection, the two organelles are also tightly linked due to the fact that the ER is the birthplace of LDs. LDs have an atypical architecture, consisting of a neutral lipid core that is covered by a phospholipid monolayer. LD biogenesis starts with neutral lipid synthesis in the ER membrane and formation of small neutral lipid lenses between its leaflets, followed by budding of mature LDs toward the cytosol. Several ER proteins have been identified that are required for efficient LD formation, among them seipin, Pex30, and FIT2. Recent evidence indicates that these LD biogenesis factors might cooperate with specific lipids, thus generating ER subdomains optimized for LD assembly. Intriguingly, LD biogenesis reacts dynamically to nutrient stress, resulting in a spatial reorganization of LD formation in the ER.
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Affiliation(s)
- Niclas T Nettebrock
- 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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23
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Lee J, Ridgway ND. Substrate channeling in the glycerol-3-phosphate pathway regulates the synthesis, storage and secretion of glycerolipids. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158438. [PMID: 30959116 DOI: 10.1016/j.bbalip.2019.03.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 01/16/2023]
Abstract
The successive acylation of glycerol-3-phosphate (G3P) by glycerol-3-phosphate acyltransferases and acylglycerol-3-phosphate acyltransferases produces phosphatidic acid (PA), a precursor for CDP-diacylglycerol-dependent phospholipid synthesis. PA is further dephosphorylated by LIPINs to produce diacylglycerol (DG), a substrate for the synthesis of triglyceride (TG) by DG acyltransferases and a precursor for phospholipid synthesis via the CDP-choline and CDP-ethanolamine (Kennedy) pathways. The channeling of fatty acids into TG for storage in lipid droplets and secretion in lipoproteins or phospholipids for membrane biogenesis is dependent on isoform expression, activity and localization of G3P pathway enzymes, as well as dietary and hormonal and tissue-specific factors. Here, we review the mechanisms that control partitioning of substrates into lipid products of the G3P pathway.
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Affiliation(s)
- Jonghwa Lee
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - Neale D Ridgway
- Atlantic Research Center, Depts. of Pediatrics and Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, Canada.
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24
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Castro IG, Eisenberg-Bord M, Persiani E, Rochford JJ, Schuldiner M, Bohnert M. Promethin Is a Conserved Seipin Partner Protein. Cells 2019; 8:E268. [PMID: 30901948 PMCID: PMC6468817 DOI: 10.3390/cells8030268] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/03/2019] [Accepted: 03/14/2019] [Indexed: 11/16/2022] Open
Abstract
Seipin (BSCL2/SPG17) is a key factor in lipid droplet (LD) biology, and its dysfunction results in severe pathologies, including the fat storage disease Berardinelli-Seip congenital lipodystrophy type 2, as well as several neurological seipinopathies. Despite its importance for human health, the molecular role of seipin is still enigmatic. Seipin is evolutionarily conserved from yeast to humans. In yeast, seipin was recently found to cooperate with the lipid droplet organization (LDO) proteins, Ldo16 and Ldo45, two structurally-related proteins involved in LD function and identity that display remote homology to the human protein promethin/TMEM159. In this study, we show that promethin is indeed an LD-associated protein that forms a complex with seipin, and its localization to the LD surface can be modulated by seipin expression levels. We thus identify promethin as a novel seipin partner protein.
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Affiliation(s)
- Inês G Castro
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Michal Eisenberg-Bord
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Elisa Persiani
- Rowett Institute and Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Aberdeen, AB25 2ZD, UK.
| | - Justin J Rochford
- Rowett Institute and Aberdeen Cardiovascular and Diabetes Centre, University of Aberdeen, Aberdeen, AB25 2ZD, UK.
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
| | - Maria Bohnert
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
- 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, 48149 Münster, Germany.
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25
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Female adipose tissue-specific Bscl2 knockout mice develop only moderate metabolic dysfunction when housed at thermoneutrality and fed a high-fat diet. Sci Rep 2018; 8:17863. [PMID: 30552349 PMCID: PMC6294754 DOI: 10.1038/s41598-018-36078-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 11/12/2018] [Indexed: 02/04/2023] Open
Abstract
Mutations affecting the BSCL2 gene cause the most severe form of congenital generalised lipodystrophy. Affected individuals almost completely lack adipose tissue and suffer from severe diabetes and metabolic complications. Likewise, mice lacking Bscl2 in all tissues have dramatically reduced adipose mass, glucose intolerance and hyperinsulinaemia. However, male adipose tissue-specific Bscl2 knockout mice fail to develop the metabolic dysfunction observed in Bscl2 null mice and BSCL2 deficient patients, despite a similar generalised lack of adipose tissues. Clinical reports indicate gender differences frequently exist in cases of lipodystrophy, with female patients more adversely affected than male patients. We therefore generated and characterised female mice lacking Bscl2 specifically in adipose tissue (Ad-B2(−/−)). We show that female Ad-B2(−/−) mice also develop early-onset lipodystrophy when fed a chow diet and are maintained under standard housing conditions (21 °C) or thermoneutrality (30 °C). Despite this, female Ad-B2(−/−) mice fail to develop severe metabolic dysfunction. Only when female Ad-B2(−/−) mice are maintained at thermoneutrality and fed a high-fat diet do subtle alterations to metabolic homeostasis manifest. This is despite a striking inability to expand adipose mass. Our findings provide further evidence that loss of Bscl2 in non-adipose tissues may contribute to the severity of metabolic dysfunction in this condition.
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26
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Sui X, Arlt H, Brock KP, Lai ZW, DiMaio F, Marks DS, Liao M, Farese RV, Walther TC. Cryo-electron microscopy structure of the lipid droplet-formation protein seipin. J Cell Biol 2018; 217:4080-4091. [PMID: 30327422 PMCID: PMC6279392 DOI: 10.1083/jcb.201809067] [Citation(s) in RCA: 120] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 10/03/2018] [Accepted: 10/05/2018] [Indexed: 01/11/2023] Open
Abstract
Sui et al. report the cryo-EM structure of the conserved luminal domain of the lipid droplet (LD)-formation protein seipin. The structure reveals key features of this domain and suggests a new model for seipin’s role in LD formation. Metabolic energy is stored in cells primarily as triacylglycerols in lipid droplets (LDs), and LD dysregulation leads to metabolic diseases. The formation of monolayer-bound LDs from the endoplasmic reticulum (ER) bilayer is poorly understood, but the ER protein seipin is essential to this process. In this study, we report a cryo–electron microscopy structure and functional characterization of Drosophila melanogaster seipin. The structure reveals a ring-shaped dodecamer with the luminal domain of each monomer resolved at ∼4.0 Å. Each luminal domain monomer exhibits two distinctive features: a hydrophobic helix (HH) positioned toward the ER bilayer and a β-sandwich domain with structural similarity to lipid-binding proteins. This structure and our functional testing in cells suggest a model in which seipin oligomers initially detect forming LDs in the ER via HHs and subsequently act as membrane anchors to enable lipid transfer and LD growth.
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Affiliation(s)
- Xuewu Sui
- Department of Cell Biology, Harvard Medical School, Boston, MA.,Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA
| | - Henning Arlt
- Department of Cell Biology, Harvard Medical School, Boston, MA.,Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA
| | - Kelly P Brock
- Department of Systems Biology, Harvard Medical School, Boston, MA
| | - Zon Weng Lai
- Department of Cell Biology, Harvard Medical School, Boston, MA.,Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA
| | - Frank DiMaio
- Department of Biochemistry and Institute of Protein Design, University of Washington, Seattle, WA
| | - Debora S Marks
- Department of Systems Biology, Harvard Medical School, Boston, MA
| | - Maofu Liao
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Robert V Farese
- Department of Cell Biology, Harvard Medical School, Boston, MA .,Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA.,Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, MA
| | - Tobias C Walther
- Department of Cell Biology, Harvard Medical School, Boston, MA .,Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, MA.,Broad Institute, Massachusetts Institute of Technology and Harvard University, Cambridge, MA.,Howard Hughes Medical Institute, Boston, MA
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27
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Yan R, Qian H, Lukmantara I, Gao M, Du X, Yan N, Yang H. Human SEIPIN Binds Anionic Phospholipids. Dev Cell 2018; 47:248-256.e4. [PMID: 30293840 DOI: 10.1016/j.devcel.2018.09.010] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 07/05/2018] [Accepted: 09/07/2018] [Indexed: 10/28/2022]
Abstract
The biogenesis of lipid droplets (LDs) and the development of adipocytes are two key aspects of mammalian fat storage. SEIPIN, an integral membrane protein of the endoplasmic reticulum (ER), plays a critical role in both LD formation and adipogenesis. The molecular function of SEIPIN, however, has yet to be elucidated. Here, we report the cryogenic electron microscopy structure of human SEIPIN at 3.8 Å resolution. SEIPIN exists as an undecamer, and this oligomerization state is critical for its physiological function. The evolutionarily conserved lumenal domain of SEIPIN forms an eight-stranded β sandwich fold. Both full-length SEIPIN and its lumenal domain can bind anionic phospholipids including phosphatidic acid. Our results suggest that SEIPIN forms a scaffold that helps maintain phospholipid homeostasis and surface tension of the ER.
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Affiliation(s)
- Renhong Yan
- Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, State Key Laboratory of Membrane Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China
| | - Hongwu Qian
- Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, State Key Laboratory of Membrane Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China.
| | - Ivan Lukmantara
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia
| | - Mingming Gao
- Laboratory of Lipid Metabolism, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia
| | - Nieng Yan
- Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, State Key Laboratory of Membrane Biology, School of Life Sciences and School of Medicine, Tsinghua University, Beijing 100084, China; Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, USA.
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, NSW 2052, Australia.
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Exploring Seipin: From Biochemistry to Bioinformatics Predictions. Int J Cell Biol 2018; 2018:5207608. [PMID: 30402103 PMCID: PMC6192094 DOI: 10.1155/2018/5207608] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/12/2018] [Accepted: 09/03/2018] [Indexed: 01/30/2023] Open
Abstract
Seipin is a nonenzymatic protein encoded by the BSCL2 gene. It is involved in lipodystrophy and seipinopathy diseases. Named in 2001, all seipin functions are still far from being understood. Therefore, we reviewed much of the research, trying to find a pattern that could explain commonly observed features of seipin expression disorders. Likewise, this review shows how this protein seems to have tissue-specific functions. In an integrative view, we conclude by proposing a theoretical model to explain how seipin might be involved in the triacylglycerol synthesis pathway.
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29
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Ding L, Yang X, Tian H, Liang J, Zhang F, Wang G, Wang Y, Ding M, Shui G, Huang X. Seipin regulates lipid homeostasis by ensuring calcium-dependent mitochondrial metabolism. EMBO J 2018; 37:embj.201797572. [PMID: 30049710 DOI: 10.15252/embj.201797572] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 07/05/2018] [Accepted: 07/09/2018] [Indexed: 02/06/2023] Open
Abstract
Seipin, the gene that causes Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2), is important for adipocyte differentiation and lipid homeostasis. Previous studies in Drosophila revealed that Seipin promotes ER calcium homeostasis through the Ca2+-ATPase SERCA, but little is known about the events downstream of perturbed ER calcium homeostasis that lead to decreased lipid storage in Drosophila dSeipin mutants. Here, we show that glycolytic metabolites accumulate and the downstream mitochondrial TCA cycle is impaired in dSeipin mutants. The impaired TCA cycle further leads to a decreased level of citrate, a critical component of lipogenesis. Mechanistically, Seipin/SERCA-mediated ER calcium homeostasis is important for maintaining mitochondrial calcium homeostasis. Reduced mitochondrial calcium in dSeipin mutants affects the TCA cycle and mitochondrial function. The lipid storage defects in dSeipin mutant fat cells can be rescued by replenishing mitochondrial calcium or by restoring the level of citrate through genetic manipulations or supplementation with exogenous metabolites. Together, our results reveal that Seipin promotes adipose tissue lipid storage via calcium-dependent mitochondrial metabolism.
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Affiliation(s)
- Long Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xiao Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - He Tian
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Jingjing Liang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Fengxia Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Guodong Wang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Yingchun Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Guanghou Shui
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China .,University of Chinese Academy of Sciences, Beijing, China
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30
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Taurino M, Costantini S, De Domenico S, Stefanelli F, Ruano G, Delgadillo MO, Sánchez-Serrano JJ, Sanmartín M, Santino A, Rojo E. SEIPIN Proteins Mediate Lipid Droplet Biogenesis to Promote Pollen Transmission and Reduce Seed Dormancy. PLANT PHYSIOLOGY 2018; 176:1531-1546. [PMID: 29203558 PMCID: PMC5813562 DOI: 10.1104/pp.17.01430] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 11/30/2017] [Indexed: 05/08/2023]
Abstract
Lipid droplets (LDs) are ubiquitous organelles in plant cells, but their physiological roles are largely unknown. To gain insight into the function of LDs in plants, we have characterized the Arabidopsis homologs of SEIPIN proteins, which are crucial factors for LD biogenesis in yeast and animals. SEIPIN1 is expressed almost exclusively in embryos, while SEIPIN2 and SEIPIN3 have broader expression profiles with maximal levels in embryos and pollen, where LDs accumulate most abundantly. Genetic analysis demonstrates that all three SEIPINs contribute to proper LD biogenesis in embryos, whereas in pollen, only SEIPIN2 and SEIPIN3 play a significant role. The double seipin2 seipin3 and triple seipin mutants accumulate extremely enlarged LDs in seeds and pollen, which hinders their subsequent mobilization during germination. Interestingly, electron microscopy analysis reveals the presence of nuclear LDs attached to type I nucleoplasmic reticulum in triple seipin mutant embryos, supporting that SEIPINs are essential for maintaining the correct polarity of LD budding at the nuclear envelope, restricting it to the outer membrane. In pollen, the perturbations in LD biogenesis and turnover are coupled to reduced germination in vitro and with lower fertilization efficiency in vivo. In seeds, germination per se is not affected in seipin2 seipin3 and triple seipin mutants, but there is a striking increase in seed dormancy levels. Our findings reveal the relevance of SEIPIN-dependent LD biogenesis in pollen transmission and in adjusting the timing of seed germination, two key adaptive traits of great importance in agriculture.
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Affiliation(s)
- Marco Taurino
- Institute of Sciences of Food Production C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Sara Costantini
- Institute of Sciences of Food Production C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
- Centro Nacional de Biotecnología-CSIC, Cantoblanco, E-28049 Madrid, Spain
| | - Stefania De Domenico
- Institute of Sciences of Food Production C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
| | - Francesco Stefanelli
- Institute of Sciences of Food Production C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
- Centro Nacional de Biotecnología-CSIC, Cantoblanco, E-28049 Madrid, Spain
| | - Guillermo Ruano
- Centro Nacional de Biotecnología-CSIC, Cantoblanco, E-28049 Madrid, Spain
- Universidad Politécnica de Madrid, E-28223 Madrid, Spain
| | | | | | - Maite Sanmartín
- Centro Nacional de Biotecnología-CSIC, Cantoblanco, E-28049 Madrid, Spain
| | - Angelo Santino
- Institute of Sciences of Food Production C.N.R. Unit of Lecce, via Monteroni, 73100 Lecce, Italy
- Address correspondence to or
| | - Enrique Rojo
- Centro Nacional de Biotecnología-CSIC, Cantoblanco, E-28049 Madrid, Spain
- Address correspondence to or
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31
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Mcilroy GD, Suchacki K, Roelofs AJ, Yang W, Fu Y, Bai B, Wallace RJ, De Bari C, Cawthorn WP, Han W, Delibegović M, Rochford JJ. Adipose specific disruption of seipin causes early-onset generalised lipodystrophy and altered fuel utilisation without severe metabolic disease. Mol Metab 2018; 10:55-65. [PMID: 29459250 PMCID: PMC5985228 DOI: 10.1016/j.molmet.2018.01.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 01/16/2018] [Accepted: 01/23/2018] [Indexed: 11/29/2022] Open
Abstract
Objective Mutations to the BSCL2 gene disrupt the protein seipin and cause the most severe form of congenital generalised lipodystrophy (CGL). Affected individuals exhibit a near complete loss of white adipose tissue (WAT) and suffer from metabolic disease. Seipin is critical for adipocyte development in culture and mice with germline disruption to Bscl2 recapitulate the effects of BSCL2 disruption in humans. Here we examined whether loss of Bscl2 specifically in developing adipocytes in vivo is sufficient to prevent adipose tissue development and cause all features observed with congenital BSCL2 disruption. Methods We generated and characterised a novel mouse model of Bscl2 deficiency in developing adipocytes (Ad-B2(−/−)) using the adipose-specific Adiponectin-Cre line. Results We demonstrate that Ad-B2(−/−) mice display early onset lipodystrophy, in common with congenital Bscl2 null mice and CGL2 patients. However, glucose intolerance, insulin resistance, and severe hepatic steatosis are not apparent. Food intake and energy expenditure are unchanged, but Ad-B2(−/−) mice exhibit significantly altered substrate utilisation. We also find differential effects of seipin loss between specific adipose depots revealing new insights regarding their varied characteristics. When fed a high-fat diet, Ad-B2(−/−) mice entirely fail to expand adipose mass but remain glucose tolerant. Conclusions Our findings demonstrate that disruption of Bscl2 specifically in developing adipocytes is sufficient to cause the early-onset generalised lipodystrophy observed in patients with mutations in BSCL2. However, this significant reduction in adipose mass does not cause the overt metabolic dysfunction seen in Bscl2 knockout mice, even following a high-fat diet challenge. Seipin loss only in developing adipocytes drives severe early-onset lipodystrophy. This leads to significantly altered use of metabolic substrates. We uncover developmental differences between poorly characterised adipose depots. Despite severely reduced adipose mass mice do not show overt metabolic disease.
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Affiliation(s)
| | - Karla Suchacki
- The Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Anke J Roelofs
- Institute of Medical Sciences, University of Aberdeen, UK
| | - Wulin Yang
- Cancer Hospital and Anhui Province Key Laboratory of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui, China
| | - Yanyun Fu
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Bo Bai
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Robert J Wallace
- Department of Orthopaedics, University of Edinburgh, Edinburgh, UK
| | - Cosimo De Bari
- Institute of Medical Sciences, University of Aberdeen, UK
| | - William P Cawthorn
- The Queen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Weiping Han
- Laboratory of Metabolic Medicine, Singapore Bioimaging Consortium, Agency for Science, Technology and Research (A*STAR), Singapore
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32
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Pyc M, Cai Y, Gidda SK, Yurchenko O, Park S, Kretzschmar FK, Ischebeck T, Valerius O, Braus GH, Chapman KD, Dyer JM, Mullen RT. Arabidopsis lipid droplet-associated protein (LDAP) - interacting protein (LDIP) influences lipid droplet size and neutral lipid homeostasis in both leaves and seeds. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 92:1182-1201. [PMID: 29083105 DOI: 10.1111/tpj.13754] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Cytoplasmic lipid droplets (LDs) are found in all types of plant cells; they are derived from the endoplasmic reticulum and function as a repository for neutral lipids, as well as serving in lipid remodelling and signalling. However, the mechanisms underlying the formation, steady-state maintenance and turnover of plant LDs, particularly in non-seed tissues, are relatively unknown. Previously, we showed that the LD-associated proteins (LDAPs) are a family of plant-specific, LD surface-associated coat proteins that are required for proper biogenesis of LDs and neutral lipid homeostasis in vegetative tissues. Here, we screened a yeast two-hybrid library using the Arabidopsis LDAP3 isoform as 'bait' in an effort to identify other novel LD protein constituents. One of the candidate LDAP3-interacting proteins was Arabidopsis At5g16550, which is a plant-specific protein of unknown function that we termed LDIP (LDAP-interacting protein). Using a combination of biochemical and cellular approaches, we show that LDIP targets specifically to the LD surface, contains a discrete amphipathic α-helical targeting sequence, and participates in both homotypic and heterotypic associations with itself and LDAP3, respectively. Analysis of LDIP T-DNA knockdown and knockout mutants showed a decrease in LD abundance and an increase in variability of LD size in leaves, with concomitant increases in total neutral lipid content. Similar phenotypes were observed in plant seeds, which showed enlarged LDs and increases in total amounts of seed oil. Collectively, these data identify LDIP as a new player in LD biology that modulates both LD size and cellular neutral lipid homeostasis in both leaves and seeds.
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Affiliation(s)
- Michal Pyc
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Yingqi Cai
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, TX, 76203, USA
| | - Satinder K Gidda
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Olga Yurchenko
- US Department of Agriculture, Agricultural Research Service, US Arid-Land Agricultural Research Center, Maricopa, AZ, 85138, USA
| | - Sunjung Park
- US Department of Agriculture, Agricultural Research Service, US Arid-Land Agricultural Research Center, Maricopa, AZ, 85138, USA
| | - Franziska K Kretzschmar
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, University of Goettingen, Justus-von-Liebig-Weg 11, 37007, Goettingen, Germany
| | - Till Ischebeck
- Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, University of Goettingen, Justus-von-Liebig-Weg 11, 37007, Goettingen, Germany
| | - Oliver Valerius
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and Genetics, University of Goettingen, Grisebachstrasse 8, 37077, Goettingen, Germany
| | - Gerhard H Braus
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and Genetics, University of Goettingen, Grisebachstrasse 8, 37077, Goettingen, Germany
| | - Kent D Chapman
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, TX, 76203, USA
| | - John M Dyer
- US Department of Agriculture, Agricultural Research Service, US Arid-Land Agricultural Research Center, Maricopa, AZ, 85138, USA
| | - Robert T Mullen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
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33
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Pagac M, Cooper DE, Qi Y, Lukmantara IE, Mak HY, Wu Z, Tian Y, Liu Z, Lei M, Du X, Ferguson C, Kotevski D, Sadowski P, Chen W, Boroda S, Harris TE, Liu G, Parton RG, Huang X, Coleman RA, Yang H. SEIPIN Regulates Lipid Droplet Expansion and Adipocyte Development by Modulating the Activity of Glycerol-3-phosphate Acyltransferase. Cell Rep 2017; 17:1546-1559. [PMID: 27806294 PMCID: PMC5647143 DOI: 10.1016/j.celrep.2016.10.037] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 09/03/2016] [Accepted: 10/10/2016] [Indexed: 12/26/2022] Open
Abstract
Berardinelli-Seip congenital lipodystrophy 2 (BSCL2) is caused by loss-of-function mutations in SEIPIN, a protein implicated in both adipogenesis and lipid droplet expansion but whose molecular function remains obscure. Here, we identify physical and functional interactions between SEIPIN and microsomal isoforms of glycerol-3-phosphate acyltransferase (GPAT) in multiple organisms. Compared to controls, GPAT activity was elevated in SEIPIN-deficient cells and tissues and GPAT kinetic values were altered. Increased GPAT activity appears to underpin the block in adipogenesis and abnormal lipid droplet morphology associated with SEIPIN loss. Overexpression of Gpat3 blocked adipogenesis, and Gpat3 knockdown in SEIPIN-deficient preadipocytes partially restored differentiation. GPAT overexpression in yeast, preadipocytes, and fly salivary glands also formed supersized lipid droplets. Finally, pharmacological inhibition of GPAT in Seipin-/- mouse preadipocytes partially restored adipogenesis. These data identify SEIPIN as an evolutionarily conserved regulator of microsomal GPAT and suggest that GPAT inhibitors might be useful for the treatment of human BSCL2 patients.
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Affiliation(s)
- Martin Pagac
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Daniel E Cooper
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yanfei Qi
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Ivan E Lukmantara
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Hoi Yin Mak
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Zengying Wu
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yuan Tian
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhonghua Liu
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Mona Lei
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Ximing Du
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Charles Ferguson
- Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD 4072, Australia
| | - Damian Kotevski
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Pawel Sadowski
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
| | - Weiqin Chen
- Department of Physiology, Medical College of Georgia Regents University, Augusta, GA 30912, USA
| | - Salome Boroda
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Thurl E Harris
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George Liu
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University Health Science Center, Beijing 100191, China
| | - Robert G Parton
- Institute for Molecular Bioscience, The University of Queensland, Queensland, QLD 4072, Australia
| | - Xun Huang
- State Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Rosalind A Coleman
- Department of Nutrition, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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34
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Pelosi M, Testet E, Le Lay S, Dugail I, Tang X, Mabilleau G, Hamel Y, Madrange M, Blanc T, Odent T, McMullen TPW, Alfò M, Brindley DN, de Lonlay P. Normal human adipose tissue functions and differentiation in patients with biallelic LPIN1 inactivating mutations. J Lipid Res 2017; 58:2348-2364. [PMID: 28986436 PMCID: PMC5711497 DOI: 10.1194/jlr.p075440] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 08/23/2017] [Indexed: 12/22/2022] Open
Abstract
Lipin-1 is a Mg2+-dependent phosphatidic acid phosphatase (PAP) that in mice is necessary for normal glycerolipid biosynthesis, controlling adipocyte metabolism, and adipogenic differentiation. Mice carrying inactivating mutations in the Lpin1 gene display the characteristic features of human familial lipodystrophy. Very little is known about the roles of lipin-1 in human adipocyte physiology. Apparently, fat distribution and weight is normal in humans carrying LPIN1 inactivating mutations, but a detailed analysis of adipose tissue appearance and functions in these patients has not been available so far. In this study, we performed a systematic histopathological, biochemical, and gene expression analysis of adipose tissue biopsies from human patients harboring LPIN1 biallelic inactivating mutations and affected by recurrent episodes of severe rhabdomyolysis. We also explored the adipogenic differentiation potential of human mesenchymal cell populations derived from lipin-1 defective patients. White adipose tissue from human LPIN1 mutant patients displayed a dramatic decrease in lipin-1 protein levels and PAP activity, with a concomitant moderate reduction of adipocyte size. Nevertheless, the adipose tissue develops without obvious histological signs of lipodystrophy and with normal qualitative composition of storage lipids. The increased expression of key adipogenic determinants such as SREBP1, PPARG, and PGC1A shows that specific compensatory phenomena can be activated in vivo in human adipocytes with deficiency of functional lipin-1.
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Affiliation(s)
- Michele Pelosi
- Centre de Référence des Maladies Héréditaires du Métabolisme, Institut Imagine des Maladies Génétiques, Laboratoire de génétique des maladies autoinflammatoires monogéniques, INSERM UMR1163, Université Paris Descartes et Hôpital Necker-Enfants malades (Assistance publique - Hôpitaux de Paris), Paris, France
| | - Eric Testet
- Laboratoire de Biogenèse Membranaire-UMR 5200, CNRS, Université de Bordeaux, Villenave d'Ornon, France
| | - Soazig Le Lay
- INSERM, UMR1063, Université d'Angers, UBL, Angers, France
| | - Isabelle Dugail
- INSERM, U1166, Equipe 6, Université Pierre et Marie Curie, Paris, France
| | - Xiaoyun Tang
- Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, Alberta, Canada
| | | | - Yamina Hamel
- Centre de Référence des Maladies Héréditaires du Métabolisme, Institut Imagine des Maladies Génétiques, Laboratoire de génétique des maladies autoinflammatoires monogéniques, INSERM UMR1163, Université Paris Descartes et Hôpital Necker-Enfants malades (Assistance publique - Hôpitaux de Paris), Paris, France
| | - Marine Madrange
- Centre de Référence des Maladies Héréditaires du Métabolisme, Institut Imagine des Maladies Génétiques, Laboratoire de génétique des maladies autoinflammatoires monogéniques, INSERM UMR1163, Université Paris Descartes et Hôpital Necker-Enfants malades (Assistance publique - Hôpitaux de Paris), Paris, France
| | - Thomas Blanc
- Department of Pediatric Surgery and Urology, Hôpital Necker-Enfants malades-Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Thierry Odent
- Department of Pediatric Orthopedics, Hôpital Necker-Enfants malades-Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Todd P W McMullen
- Department of Surgery, University of Alberta, Edmonton, Alberta, Canada
| | - Marco Alfò
- Dipartimento di Scienze Statistiche, Sapienza Università di Roma, Rome, Italy
| | - David N Brindley
- Department of Biochemistry, Signal Transduction Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Pascale de Lonlay
- Centre de Référence des Maladies Héréditaires du Métabolisme, Institut Imagine des Maladies Génétiques, Laboratoire de génétique des maladies autoinflammatoires monogéniques, INSERM UMR1163, Université Paris Descartes et Hôpital Necker-Enfants malades (Assistance publique - Hôpitaux de Paris), Paris, France
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35
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Joshi AS, Zhang H, Prinz WA. Organelle biogenesis in the endoplasmic reticulum. Nat Cell Biol 2017; 19:876-882. [DOI: 10.1038/ncb3579] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 06/21/2017] [Indexed: 12/16/2022]
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36
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Chen X, Goodman JM. The collaborative work of droplet assembly. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1205-1211. [PMID: 28711458 DOI: 10.1016/j.bbalip.2017.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 07/05/2017] [Accepted: 07/06/2017] [Indexed: 10/19/2022]
Abstract
Three proteins have been implicated in the assembly of cytoplasmic lipid droplets: seipin, FIT2, and perilipin. This review examines the current theories of seipin function as well as the evidence for the involvement of all three proteins in droplet biogenesis, and ends with a proposal of how they collaborate to regulate the formation of droplets. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Xiao Chen
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX 75390-9041, United States
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX 75390-9041, United States.
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37
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Lipid droplet growth and adipocyte development: mechanistically distinct processes connected by phospholipids. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1273-1283. [PMID: 28668300 DOI: 10.1016/j.bbalip.2017.06.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 06/20/2017] [Accepted: 06/23/2017] [Indexed: 12/19/2022]
Abstract
The differentiation of preadipocytes into mature adipocytes is accompanied by the growth and formation of a giant, unilocular lipid droplet (LD). Mechanistically however, LD growth and adipogenesis are two different processes. Recent studies have uncovered a number of proteins that are able to regulate both LD dynamics and adipogenesis, such as SEIPIN, LIPIN and CDP-Diacylglycerol Synthases. It appears that phospholipids, phosphatidic acid in particular, play a critical role in both LD budding/growth and adipocyte development. This review summarizes recent advances, and aims to provide a better understanding of LD growth as well as adipogenesis, two critical aspects in mammalian fat storage. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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38
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Schuldiner M, Bohnert M. A different kind of love - lipid droplet contact sites. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28627434 DOI: 10.1016/j.bbalip.2017.06.005] [Citation(s) in RCA: 128] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Lipid droplets (LDs) store lipids and hence serve as energy reservoir and as a source for building-blocks for the organelle membrane systems. LD biology therefore depends on tight communication with other organelles. The unique architecture of LDs, consisting of a neutral lipid core shielded by a phospholipid-monolayer, is however an obstacle to bulk-exchange of bilayer-bounded vesicles with other organelles. In recent years, it is emerging that contact sites, places where two organelles are positioned in close proximity allowing vesicle-independent communication, are an important way to integrate LDs into the organellar landscape. However, few LD contact sites have been studied in depth and our understanding of their structure, extent and function is only starting to emerge. Here, we highlight recent findings on the functions of LD contact sites and on the proteins involved in their formation and hypothesize about the unique characteristics of the contact sites formed by these intriguing organelles. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Maria Bohnert
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel.
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Zhang P, Reue K. Lipin proteins and glycerolipid metabolism: Roles at the ER membrane and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1583-1595. [PMID: 28411173 DOI: 10.1016/j.bbamem.2017.04.007] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/29/2017] [Accepted: 04/09/2017] [Indexed: 01/09/2023]
Abstract
The regulation of glycerolipid biosynthesis is critical for homeostasis of cellular lipid stores and membranes. Here we review the role of lipin phosphatidic acid phosphatase enzymes in glycerolipid synthesis. Lipin proteins are unique among glycerolipid biosynthetic enzymes in their ability to transit among cellular membranes, rather than remain membrane tethered. We focus on the mechanisms that underlie lipin protein interactions with membranes and the versatile roles of lipins in several organelles, including the endoplasmic reticulum, mitochondria, endolysosomes, lipid droplets, and nucleus. We also review the corresponding physiological roles of lipins, which have been uncovered by the study of genetic lipin deficiencies. We propose that the growing body of knowledge concerning the biochemical and cellular activities of lipin proteins will be valuable for understanding the physiological functions of lipin proteins in health and disease. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
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Affiliation(s)
- Peixiang Zhang
- Human Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, United States
| | - Karen Reue
- Human Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, United States; Molecular Biology Institute, University of California, Los Angeles, United States.
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40
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Barneda D, Christian M. Lipid droplet growth: regulation of a dynamic organelle. Curr Opin Cell Biol 2017; 47:9-15. [PMID: 28231490 DOI: 10.1016/j.ceb.2017.02.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 02/01/2017] [Accepted: 02/04/2017] [Indexed: 12/31/2022]
Abstract
Intracellular lipid droplets (LDs) are remarkably dynamic and complex organelles that enact regulated storage and release of lipids to fulfil their fundamental roles in energy metabolism, membrane synthesis and provision of lipid-derived signaling molecules. Although small LDs are observed in all types of eukaryotic cells, it is adipocytes that present the widest range of sizes up to the massive unilocular droplet of a white adipocyte. Our knowledge of the proteins and associated processes that control LD dynamics is improving. The dynamic expression of LD-associated proteins is vital for controlling LD biology and is most apparent during adipocyte differentiation. Recent findings on the molecular mechanisms of lipid droplet enlargement reveal the importance of distinct functional groups of proteins and phospholipids.
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Affiliation(s)
| | - Mark Christian
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
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41
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Regulation of lipid metabolism via a connection between the endoplasmic reticulum and lipid droplets. Anat Sci Int 2016; 92:50-54. [DOI: 10.1007/s12565-016-0378-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 09/29/2016] [Indexed: 01/06/2023]
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42
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Wang H, Becuwe M, Housden BE, Chitraju C, Porras AJ, Graham MM, Liu XN, Thiam AR, Savage DB, Agarwal AK, Garg A, Olarte MJ, Lin Q, Fröhlich F, Hannibal-Bach HK, Upadhyayula S, Perrimon N, Kirchhausen T, Ejsing CS, Walther TC, Farese RV. Seipin is required for converting nascent to mature lipid droplets. eLife 2016; 5. [PMID: 27564575 PMCID: PMC5035145 DOI: 10.7554/elife.16582] [Citation(s) in RCA: 253] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/25/2016] [Indexed: 12/16/2022] Open
Abstract
How proteins control the biogenesis of cellular lipid droplets (LDs) is poorly understood. Using Drosophila and human cells, we show here that seipin, an ER protein implicated in LD biology, mediates a discrete step in LD formation-the conversion of small, nascent LDs to larger, mature LDs. Seipin forms discrete and dynamic foci in the ER that interact with nascent LDs to enable their growth. In the absence of seipin, numerous small, nascent LDs accumulate near the ER and most often fail to grow. Those that do grow prematurely acquire lipid synthesis enzymes and undergo expansion, eventually leading to the giant LDs characteristic of seipin deficiency. Our studies identify a discrete step of LD formation, namely the conversion of nascent LDs to mature LDs, and define a molecular role for seipin in this process, most likely by acting at ER-LD contact sites to enable lipid transfer to nascent LDs.
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Affiliation(s)
- Huajin Wang
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States.,Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Michel Becuwe
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | | | - Chandramohan Chitraju
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Ashley J Porras
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Morven M Graham
- Center for Cellular and Molecular Imaging, Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Xinran N Liu
- Center for Cellular and Molecular Imaging, Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Abdou Rachid Thiam
- Laboratoire de Physique Statistique, École Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris-Cité, Sorbonne Universités UPMC Univ Paris 06, CNRS UMR 8550, Paris, France
| | - David B Savage
- The University of Cambridge Metabolic Research Laboratories, Wellcome Trust-MRC Institute of Metabolic Science, Cambridge, United Kingdom
| | - Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, United States
| | - Abhimanyu Garg
- Division of Nutrition and Metabolic Diseases, Department of Internal Medicine, UT Southwestern Medical Center, Dallas, United States
| | - Maria-Jesus Olarte
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Qingqing Lin
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Florian Fröhlich
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States.,Molecular Membrane Biology Section, Department of Biology/Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Hans Kristian Hannibal-Bach
- VILLUM Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Srigokul Upadhyayula
- Department of Cell Biology, Harvard Medical School, Boston, United States.,Department of Pediatrics, Harvard Medical School, Boston, United States.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, United States.,Howard Hughes Medical Institute, Boston, United States
| | - Tomas Kirchhausen
- Department of Cell Biology, Harvard Medical School, Boston, United States.,Department of Pediatrics, Harvard Medical School, Boston, United States.,Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, United States
| | - Christer S Ejsing
- VILLUM Center for Bioanalytical Sciences, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States.,Howard Hughes Medical Institute, Boston, United States.,Broad Institute of Harvard and MIT, Cambridge, United States
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T H Chan School of Public Health, Boston, United States.,Department of Cell Biology, Harvard Medical School, Boston, United States.,Broad Institute of Harvard and MIT, Cambridge, United States
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43
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Fernández-Murray JP, McMaster CR. Lipid synthesis and membrane contact sites: a crossroads for cellular physiology. J Lipid Res 2016; 57:1789-1805. [PMID: 27521373 DOI: 10.1194/jlr.r070920] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Indexed: 12/17/2022] Open
Abstract
Membrane contact sites (MCSs) are regions of close apposition between different organelles that contribute to the functional integration of compartmentalized cellular processes. In recent years, we have gained insight into the molecular architecture of several contact sites, as well as into the regulatory mechanisms that underlie their roles in cell physiology. We provide an overview of two selected topics where lipid metabolism intersects with MCSs and organelle dynamics. First, the role of phosphatidic acid phosphatase, Pah1, the yeast homolog of metazoan lipin, toward the synthesis of triacylglycerol is outlined in connection with the seipin complex, Fld1/Ldb16, and lipid droplet formation. Second, we recapitulate the different contact sites connecting mitochondria and the endomembrane system and emphasize their contribution to phospholipid synthesis and their coordinated regulation. A comprehensive view is emerging where the multiplicity of contact sites connecting different cellular compartments together with lipid transfer proteins functioning at more than one MCS allow for functional redundancy and cross-regulation.
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Berardinelli-Seip Congenital Lipodystrophy 2/Seipin Is Not Required for Brown Adipogenesis but Regulates Brown Adipose Tissue Development and Function. Mol Cell Biol 2016; 36:2027-38. [PMID: 27185876 DOI: 10.1128/mcb.01120-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/08/2016] [Indexed: 01/08/2023] Open
Abstract
Brown adipose tissue (BAT) plays a unique role in regulating whole-body energy homeostasis by dissipating energy through thermogenic uncoupling. Berardinelli-Seip congenital lipodystrophy (BSCL) type 2 (BSCL2; also known as seipin) is a lipodystrophy-associated endoplasmic reticulum membrane protein essential for white adipocyte differentiation. Whether BSCL2 directly participates in brown adipocyte differentiation, development, and function, however, is unknown. We show that BSCL2 expression is increased during brown adipocyte differentiation. Its deletion does not impair the classic brown adipogenic program but rather induces premature activation of differentiating brown adipocytes through cyclic AMP (cAMP)/protein kinase A (PKA)-mediated lipolysis and fatty acid and glucose oxidation, as well as uncoupling. cAMP/PKA signaling is physiologically activated during neonatal BAT development in wild-type mice and greatly potentiated in mice with genetic deletion of Bscl2 in brown progenitor cells, leading to reduced BAT mass and lipid content during neonatal brown fat formation. However, prolonged overactivation of cAMP/PKA signaling during BAT development ultimately causes apoptosis of brown adipocytes through inflammation, resulting in BAT atrophy and increased overall adiposity in adult mice. These findings reveal a key cell-autonomous role for BSCL2 in controlling BAT mass/activity and provide novel insights into therapeutic strategies targeting cAMP/PKA signaling to regulate brown adipocyte function, viability, and metabolic homeostasis.
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45
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Cautivo KM, Lizama CO, Tapia PJ, Agarwal AK, Garg A, Horton JD, Cortés VA. AGPAT2 is essential for postnatal development and maintenance of white and brown adipose tissue. Mol Metab 2016; 5:491-505. [PMID: 27408775 PMCID: PMC4921804 DOI: 10.1016/j.molmet.2016.05.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 04/29/2016] [Accepted: 05/06/2016] [Indexed: 01/18/2023] Open
Abstract
Objective Characterize the cellular and molecular events responsible for lipodystrophy in AGPAT2 deficient mice. Methods Adipose tissue and differentiated MEF were assessed using light and electron microscopy, followed by protein (immunoblots) and mRNA analysis (qPCR). Phospholipid profiling was determined by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Results In contrast to adult Agpat2−/− mice, fetuses and newborn Agpat2−/− mice have normal mass of white and brown adipose tissue. Loss of both the adipose tissue depots occurs during the first week of postnatal life as a consequence of adipocyte death and inflammatory infiltration of the adipose tissue. At the ultrastructural level, adipose tissue of newborn Agpat2−/− mice is virtually devoid of caveolae and has abnormal mitochondria and lipid droplets. Autophagic structures are also abundant. Consistent with these findings, differentiated Agpat2−/− mouse embryonic fibroblasts (MEFs) also have impaired adipogenesis, characterized by a lower number of lipid-laden cells and ultrastructural abnormalities in lipid droplets, mitochondria and plasma membrane. Overexpression of PPARγ, the master regulator of adipogenesis, increased the number of Agpat2−/− MEFs that differentiated into adipocyte-like cells but did not prevent morphological abnormalities and cell death. Furthermore, differentiated Agpat2−/− MEFs have abnormal phospholipid compositions with 3-fold increased levels of phosphatidic acid. Conclusion We conclude that lipodystrophy in Agpat2−/− mice results from postnatal cell death of adipose tissue in association with acute local inflammation. It is possible that AGPAT2 deficient adipocytes have an altered lipid filling or a reduced capacity to adapt the massive lipid availability associated with postnatal feeding. Post weaning Agpat2−/− mice are lipodystrophic. However, they are born with normal mass of white and brown adipose tissue. Adipose tissue in Agpat2−/− mice undergoes postnatal inflammatory cell death. Differentiated Agpat2−/− MEFs recapitulate abnormalities of Agpat2−/− adipocytes. Abnormal phospholipid composition might underlies lipodystrophy in Agpat2−/− mice.
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Affiliation(s)
- Kelly M Cautivo
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile; Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Carlos O Lizama
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Pablo J Tapia
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
| | - Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, TX 75390, USA
| | - Abhimanyu Garg
- Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, TX 75390, USA
| | - Jay D Horton
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Víctor A Cortés
- Department of Nutrition, Diabetes and Metabolism, School of Medicine, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile.
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46
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Adipose tissue deficiency results in severe hyperlipidemia and atherosclerosis in the low-density lipoprotein receptor knockout mice. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:410-8. [PMID: 26921684 DOI: 10.1016/j.bbalip.2016.02.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 02/11/2016] [Accepted: 02/23/2016] [Indexed: 12/17/2022]
Abstract
Adipose tissue can store over 50% of whole-body cholesterol; however, the physiological role of adipose tissue in cholesterol metabolism and atherogenesis has not been directly assessed. Here, we examined lipoprotein metabolism and atherogenesis in a unique mouse model of severe lipodystrophy: the Seipin(-/-) mice, and also in mice deficient in both low-density lipoprotein receptor (Ldlr) and Seipin: the Ldlr(-/-)Seipin(-/-) mice. Plasma cholesterol was moderately increased in the Seipin(-/-) mice when fed an atherogenic diet. Strikingly, plasma cholesterol reached ~6000 mg/dl in the Seipin(-/-)Ldlr(-/-) mice on an atherogenic diet, as compared to ~1000 mg/dl in the Ldlr(-/-) mice on the same diet. The Seipin(-/-)Ldlr(-/-) mice also developed spontaneous atherosclerosis on chow diet and severe atherosclerosis on an atherogenic diet. Rosiglitazone treatment significantly reduced the hypercholesterolemia of the Seipin(-/-)Ldlr(-/-) mice, and also alleviated the severity of atherosclerosis. Our results provide direct evidence, for the first time, that the adipose tissue plays a critical role in the clearance of plasma cholesterol. Our results also reveal a previously unappreciated strong link between adipose tissue and LDLR in plasma cholesterol metabolism.
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47
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Ramanathan N, Lim N, Stewart CL. DDX5/p68 RNA helicase expression is essential for initiating adipogenesis. Lipids Health Dis 2015; 14:160. [PMID: 26637310 PMCID: PMC4670549 DOI: 10.1186/s12944-015-0163-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 12/01/2015] [Indexed: 12/29/2022] Open
Abstract
Background DDX5/p68 RNA helicase is a member of the DEAD (Asp-Glu-Ala-Asp) box proteins. Apart from RNA unwinding, DDX5 is an important transcriptional factor and co-activator in cell proliferation and differentiation. Findings Here, we have characterised the role of DDX5 in adipogenesis in 3T3-L1 cells using siRNA mediated suppression. Transient inhibition of Ddx5 mRNA expression at the start of adipogenesis impairs the differentiation programme even when DDX5 expression is restored later in adipogenesis. However transient suppression of Ddx5 at the later stages of adipogenesis do not impair adipogenesis or triglyceride accumulation suggesting Ddx5 expression is dispensable in a mature adipocyte. Conclusion These results implicate DDX5 as a crucial factor involved in the complex transcriptional cascade of events that regulate adipogenesis and essential to the initiation of adipogenesis.
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Affiliation(s)
- Nardev Ramanathan
- Developmental and Regenerative Biology Laboratory, Institute of Medical Biology, #06-06, 8A Biomedical Grove, Singapore, 138648, Republic of Singapore. .,Present address: Davos Life Science Pte Ltd, 3 Biopolis Drive, #04-19, Synapse, Singapore, 138623, Republic of Singapore.
| | - Nicole Lim
- Developmental and Regenerative Biology Laboratory, Institute of Medical Biology, #06-06, 8A Biomedical Grove, Singapore, 138648, Republic of Singapore. .,School of Biological Sciences, College of Science, Nanyang Technological University, Singapore, 637551, Republic of Singapore.
| | - Colin L Stewart
- Developmental and Regenerative Biology Laboratory, Institute of Medical Biology, #06-06, 8A Biomedical Grove, Singapore, 138648, Republic of Singapore. .,School of Biological Sciences, College of Science, Nanyang Technological University, Singapore, 637551, Republic of Singapore.
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48
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Abstract
Congenital generalized lipodystrophy (CGL) is a heterogeneous autosomal recessive disorder characterized by a near complete lack of adipose tissue from birth and, later in life, the development of metabolic complications, such as diabetes mellitus, hypertriglyceridaemia and hepatic steatosis. Four distinct subtypes of CGL exist: type 1 is associated with AGPAT2 mutations; type 2 is associated with BSCL2 mutations; type 3 is associated with CAV1 mutations; and type 4 is associated with PTRF mutations. The products of these genes have crucial roles in phospholipid and triglyceride synthesis, as well as in the formation of lipid droplets and caveolae within adipocytes. The predominant cause of metabolic complications in CGL is excess triglyceride accumulation in the liver and skeletal muscle owing to the inability to store triglycerides in adipose tissue. Profound hypoleptinaemia further exacerbates metabolic derangements by inducing a voracious appetite. Patients require psychological support, a low-fat diet, increased physical activity and cosmetic surgery. Aside from conventional therapy for hyperlipidaemia and diabetes mellitus, metreleptin replacement therapy can dramatically improve metabolic complications in patients with CGL. In this Review, we discuss the molecular genetic basis of CGL, the pathogenesis of the disease's metabolic complications and therapeutic options for patients with CGL.
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Affiliation(s)
- Nivedita Patni
- Division of Paediatric Endocrinology, Department of Paediatrics, Department of Internal Medicine, Centre for Human Nutrition, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8537, USA
| | - Abhimanyu Garg
- Division of Nutrition and Metabolic Diseases, Department of Internal Medicine, Center for Human Nutrition, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-8537, USA
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49
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Zhou H, Lei X, Benson T, Mintz J, Xu X, Harris RB, Weintraub NL, Wang X, Chen W. Berardinelli-Seip congenital lipodystrophy 2 regulates adipocyte lipolysis, browning, and energy balance in adult animals. J Lipid Res 2015; 56:1912-25. [PMID: 26269358 DOI: 10.1194/jlr.m060244] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Indexed: 11/20/2022] Open
Abstract
Mutations in BSCL2/SEIPIN cause Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2), but the mechanisms whereby Bscl2 regulates adipose tissue function are unclear. Here, we generated adipose tissue (mature) Bscl2 knockout (Ad-mKO) mice, in which Bscl2 was specifically ablated in adipocytes of adult animals, to investigate the impact of acquired Bscl2 deletion on adipose tissue function and energy balance. Ad-mKO mice displayed reduced adiposity and were protected against high fat diet-induced obesity, but not insulin resistance or hepatic steatosis. Gene expression profiling and biochemical assays revealed increased lipolysis and fatty acid oxidation in white adipose tissue (WAT) and brown adipose tissue , as well as browning of WAT, owing to induction of cAMP/protein kinase A signaling upon Bscl2 deletion. Interestingly, Bscl2 deletion reduced food intake and downregulated adipose β3-adrenergic receptor (ADRB3) expression. Impaired ADRB3 signaling partially offsets upregulated browning-induced energy expenditure and thermogenesis in Ad-mKO mice housed at ambient temperature. However, this counter-regulatory response was abrogated under thermoneutral conditions, resulting in even greater body mass loss in Ad-mKO mice. These findings suggest that Bscl2 regulates adipocyte lipolysis and β-adrenergic signaling to produce complex effects on adipose tissues and whole-body energy balance.
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Affiliation(s)
- Hongyi Zhou
- Department of Physiology, Georgia Regents University, Augusta, GA 30912
| | - Xinnuo Lei
- Department of Physiology, Georgia Regents University, Augusta, GA 30912
| | - Tyler Benson
- Vascular Biology Center, Georgia Regents University, Augusta, GA 30912
| | - James Mintz
- Vascular Biology Center, Georgia Regents University, Augusta, GA 30912
| | - Xiaojing Xu
- Georgia Prevention Institute, Department of Pediatrics, Georgia Regents University, Augusta, GA 30912
| | - Ruth B Harris
- Department of Physiology, Georgia Regents University, Augusta, GA 30912
| | - Neal L Weintraub
- Vascular Biology Center, Georgia Regents University, Augusta, GA 30912
| | - Xiaoling Wang
- Georgia Prevention Institute, Department of Pediatrics, Georgia Regents University, Augusta, GA 30912
| | - Weiqin Chen
- Department of Physiology, Georgia Regents University, Augusta, GA 30912
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50
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Gao Q, Goodman JM. The lipid droplet-a well-connected organelle. Front Cell Dev Biol 2015; 3:49. [PMID: 26322308 PMCID: PMC4533013 DOI: 10.3389/fcell.2015.00049] [Citation(s) in RCA: 159] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/24/2015] [Indexed: 12/19/2022] Open
Abstract
Our knowledge of inter-organellar communication has grown exponentially in recent years. This review focuses on the interactions that cytoplasmic lipid droplets have with other organelles. Twenty-five years ago droplets were considered simply particles of coalesced fat. Ten years ago there were hints from proteomics studies that droplets might interact with other structures to share lipids and proteins. Now it is clear that the droplets interact with many if not most cellular structures to maintain cellular homeostasis and to buffer against insults such as starvation. The evidence for this statement, as well as probes to understand the nature and results of droplet interactions, are presented.
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Affiliation(s)
- Qiang Gao
- Department of Pharmacology, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical Center Dallas, TX, USA
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