51
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Salo VT, Li S, Vihinen H, Hölttä-Vuori M, Szkalisity A, Horvath P, Belevich I, Peränen J, Thiele C, Somerharju P, Zhao H, Santinho A, Thiam AR, Jokitalo E, Ikonen E. Seipin Facilitates Triglyceride Flow to Lipid Droplet and Counteracts Droplet Ripening via Endoplasmic Reticulum Contact. Dev Cell 2019; 50:478-493.e9. [PMID: 31178403 DOI: 10.1016/j.devcel.2019.05.016] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 02/27/2019] [Accepted: 05/03/2019] [Indexed: 01/02/2023]
Abstract
Seipin is an oligomeric integral endoplasmic reticulum (ER) protein involved in lipid droplet (LD) biogenesis. To study the role of seipin in LD formation, we relocalized it to the nuclear envelope and found that LDs formed at these new seipin-defined sites. The sites were characterized by uniform seipin-mediated ER-LD necks. At low seipin content, LDs only grew at seipin sites, and tiny, growth-incompetent LDs appeared in a Rab18-dependent manner. When seipin was removed from ER-LD contacts within 1 h, no lipid metabolic defects were observed, but LDs became heterogeneous in size. Studies in seipin-ablated cells and model membranes revealed that this heterogeneity arises via a biophysical ripening process, with triglycerides partitioning from smaller to larger LDs through droplet-bilayer contacts. These results suggest that seipin supports the formation of structurally uniform ER-LD contacts and facilitates the delivery of triglycerides from ER to LDs. This counteracts ripening-induced shrinkage of small LDs.
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Affiliation(s)
- Veijo T Salo
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Shiqian Li
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Helena Vihinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Maarit Hölttä-Vuori
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | | | | | - Ilya Belevich
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Johan Peränen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | | | - Pentti Somerharju
- Department of Biochemistry, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Hongxia Zhao
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Alexandre Santinho
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Universite de Paris, Paris, France
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Universite de Paris, Paris, France.
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
| | - Elina Ikonen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland.
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52
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Jackson CL. Lipid droplet biogenesis. Curr Opin Cell Biol 2019; 59:88-96. [PMID: 31075519 DOI: 10.1016/j.ceb.2019.03.018] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 03/24/2019] [Accepted: 03/29/2019] [Indexed: 11/18/2022]
Abstract
Lipid droplets (LDs) store neutral lipids in their core as an energy source when nutrients are scarce. The center of an LD is hydrophobic, and hence it is surrounded by a phospholipid monolayer, unlike other organelles that have an aqueous interior and are bounded by a phospholipid bilayer. LDs arise from the ER, where neutral lipid synthesis enzymes are localized. A combination of biophysical analysis and modeling, in vitro reconstitution and cell biological analyses has provided a great deal of information over the past few years on the process of LD biogenesis from the ER. In addition to lipid composition, four protein families (seipin proteins, perilipins, FIT proteins and ER shaping proteins) are crucial for LD biogenesis. Recent studies have shown that LDs preferentially arise, along with peroxisomes, at special ER sites marked by the reticulon-like Pex30/MCTP2 protein. New functions for perilipins and FIT family proteins have been uncovered, and the cryo-electron microscopy structure of seipin coupled with high resolution imaging in cells has provided a more comprehensive picture of its function in LD biogenesis. Seipin, along with other proteins such as Rab18 and its effector NRZ, have been shown to carry out their functions at least in part through regulation of ER-LD contact sites, whose establishment and maintenance have emerged as an essential component of LD biogenesis and maturation.
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Affiliation(s)
- Catherine L Jackson
- Institut Jacques Monod, UMR7592 CNRS Université Paris-Diderot, Sorbonne Paris Cité, Paris, France.
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53
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Dejgaard SY, Presley JF. Rab18: new insights into the function of an essential protein. Cell Mol Life Sci 2019; 76:1935-1945. [PMID: 30830238 PMCID: PMC11105521 DOI: 10.1007/s00018-019-03050-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 02/14/2019] [Accepted: 02/19/2019] [Indexed: 12/14/2022]
Abstract
Rab18 is one of the small number of conserved Rab proteins which have been traced to the last eukaryotic common ancestor. It is found in organisms ranging from humans to trypanosomes, and localizes to multiple organelles, including most notably endoplasmic reticulum and lipid droplets. In humans, absence of Rab18 leads to a severe illness known as Warburg-Micro syndrome. Despite this evidence that Rab18 is essential, its role in cells remains mysterious. However, recent studies identifying effectors and interactors of Rab18, are now shedding light on its mechanism of action, suggesting functions related to organelle tethering and to autophagy. In this review, we examine the variety of roles proposed for Rab18 with a focus on new evidence giving insights into the molecular mechanisms it utilizes. Based on this summary of our current understanding, we identify priority areas for further research.
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Affiliation(s)
- Selma Yilmaz Dejgaard
- Department of Medical Biology, Near East University, Nicosia, Cyprus
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, QC, H3A 0C7, Canada
| | - John F Presley
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, QC, H3A 0C7, Canada.
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54
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Mather IH, Masedunskas A, Chen Y, Weigert R. Symposium review: Intravital imaging of the lactating mammary gland in live mice reveals novel aspects of milk-lipid secretion. J Dairy Sci 2019; 102:2760-2782. [PMID: 30471915 PMCID: PMC7094374 DOI: 10.3168/jds.2018-15459] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 09/21/2018] [Indexed: 12/22/2022]
Abstract
Milk fat comprises membrane-coated droplets of neutral lipid, which constitute the predominant source of lipids for survival of the suckling neonate. From the perspective of the dairy industry, they are the basis for the manufacture of butter and essential ingredients in the production of cheese, yogurt, and specialty dairy produce. To provide mechanistic insight into the assembly and secretion of lipid droplets during lactation, we developed novel intravital imaging techniques using transgenic mice, which express fluorescently tagged marker proteins. The number 4 mammary glands were surgically prepared under a deep plane of anesthesia and the exposed glands positioned as a skin flap with intact vascular supply on the stage of a laser-scanning confocal microscope. Lipid droplets were stained by prior exposure of the glands to hydrophobic fluorescent BODIPY (boron-dipyrromethene) dyes and their formation and secretion monitored by time-lapse subcellular microscopy over periods of 1 to 2 h. Droplets were transported to the cell apex by directed (superdiffusive) motion at relatively slow and intermittent rates (0-2 µm/min). Regardless of size, droplets grew by numerous fusion events during transport and as they were budding from the cell enveloped by apical membranes. Surprisingly, droplet secretion was not constitutive but required an injection of oxytocin to induce contraction of the myoepithelium with subsequent release of droplets into luminal spaces. These novel results are discussed in the context of the current paradigm for milk fat synthesis and secretion and as a template for future innovations in the dairy industry.
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Affiliation(s)
- Ian H Mather
- Department of Animal and Avian Sciences, University of Maryland, College Park 20742; National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892.
| | - Andrius Masedunskas
- National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
| | - Yun Chen
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21205
| | - Roberto Weigert
- National Cancer Institute and National Institute of Craniofacial and Dental Research, National Institutes of Health, Bethesda, MD 20892
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55
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Nian FS, Li LL, Cheng CY, Wu PC, Lin YT, Tang CY, Ren BS, Tai CY, Fann MJ, Kao LS, Hong CJ, Tsai JW. Rab18 Collaborates with Rab7 to Modulate Lysosomal and Autophagy Activities in the Nervous System: an Overlapping Mechanism for Warburg Micro Syndrome and Charcot-Marie-Tooth Neuropathy Type 2B. Mol Neurobiol 2019; 56:6095-6105. [PMID: 30721447 DOI: 10.1007/s12035-019-1471-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 01/10/2019] [Indexed: 01/24/2023]
Abstract
Mutations in RAB18, a member of small G protein, cause Warburg micro syndrome (WARBM), whose clinical features include vision impairment, postnatal microcephaly, and lower limb spasticity. Previously, our Rab18-/- mice exhibited hind limb weakness and spasticity as well as signs of axonal degeneration in the spinal cord and lumbar spinal nerves. However, the cellular and molecular function of RAB18 and its roles in the pathogenesis of WARBM are still not fully understood. Using immunofluorescence staining and expression of Rab18 and organelle markers, we find that Rab18 associates with lysosomes and actively traffics along neurites in cultured neurons. Interestingly, Rab18-/- neurons exhibit impaired lysosomal transport. Using autophagosome marker LC3-II, we show that Rab18 dysfunction leads to aberrant autophagy activities in neurons. Electron microscopy further reveals accumulation of lipofuscin-like granules in the dorsal root ganglion of Rab18-/- mice. Surprisingly, Rab18 colocalizes, cofractionates, and coprecipitates with the lysosomal regulator Rab7, mutations of which cause Charcot-Marie-Tooth (CMT) neuropathy type 2B. Moreover, Rab7 is upregulated in Rab18-deficient neurons, suggesting a compensatory effect. Together, our results suggest that the functions of RAB18 and RAB7 in lysosomal and autophagic activities may constitute an overlapping mechanism underlying WARBM and CMT pathogenesis in the nervous system.
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Affiliation(s)
- Fang-Shin Nian
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan.,Program in Molecular Medicine, National Yang-Ming University and Academia Sinica, Taipei, Taiwan
| | - Lei-Li Li
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
| | - Chih-Ya Cheng
- Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Pei-Chun Wu
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.,Brain Research Center, National Yang-Ming University, Taipei, Taiwan
| | - You-Tai Lin
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Cheng-Yung Tang
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Bo-Shiun Ren
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
| | - Chin-Yin Tai
- Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Taiwan
| | - Ming-Ji Fann
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.,Brain Research Center, National Yang-Ming University, Taipei, Taiwan
| | - Lung-Sen Kao
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan.,Brain Research Center, National Yang-Ming University, Taipei, Taiwan
| | - Chen-Jee Hong
- Brain Research Center, National Yang-Ming University, Taipei, Taiwan.,Division of Psychiatry, School of Medicine, National Yang-Ming University, Taipei, Taiwan.,Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Jin-Wu Tsai
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan. .,Brain Research Center, National Yang-Ming University, Taipei, Taiwan. .,Biopotonics and Molecular Imaging Research Center, National Yang-Ming University, Taipei, Taiwan.
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56
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Huang S, Jiang L, Zhuang X. Possible Roles of Membrane Trafficking Components for Lipid Droplet Dynamics in Higher Plants and Green Algae. FRONTIERS IN PLANT SCIENCE 2019; 10:207. [PMID: 30858860 PMCID: PMC6397863 DOI: 10.3389/fpls.2019.00207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 02/07/2019] [Indexed: 05/04/2023]
Abstract
Lipid droplets are ubiquitous dynamic organelles that contain neutral lipids surrounded by a phospholipid monolayer. They can store and supply lipids for energy metabolism and membrane synthesis. In addition, protein transport and lipid exchange often occur between LDs and various organelles to control lipid homeostasis in response to multiple stress responses and cellular signaling. In recent years, multiple membrane trafficking proteins have been identified through LD proteomics and genetic analyses. These membrane trafficking machineries are emerging as critical regulators to function in different LD-organelle interactions, e.g., for LD dynamics, biogenesis and turnover. In this review, we will summarize recent advances in regard to LD-related membrane trafficking proteins and discuss future investigations in higher plants and green algae.
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Affiliation(s)
- Shuxian Huang
- Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Liwen Jiang
- Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
- The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - Xiaohong Zhuang
- Centre for Cell and Developmental Biology, State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
- *Correspondence: Xiaohong Zhuang,
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57
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Abstract
The Golgi apparatus is a central sorting station in the cell. It receives newly synthesized molecules from the endoplasmic reticulum and directs them to different subcellular destinations, such as the plasma membrane or the endocytic pathway. Importantly, in the last few years, it has emerged that the maintenance of Golgi structure is connected to the proper regulation of membrane trafficking. Rab proteins are small GTPases that are considered to be the master regulators of the intracellular membrane trafficking. Several of the over 60 human Rabs are involved in the regulation of transport pathways at the Golgi as well as in the maintenance of its architecture. This chapter will summarize the different roles of Rab GTPases at the Golgi, both as regulators of membrane transport, scaffold, and tethering proteins and in preserving the structure and function of this organelle.
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58
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Elgner F, Hildt E, Bender D. Relevance of Rab Proteins for the Life Cycle of Hepatitis C Virus. Front Cell Dev Biol 2018; 6:166. [PMID: 30564577 PMCID: PMC6288913 DOI: 10.3389/fcell.2018.00166] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 11/20/2018] [Indexed: 12/18/2022] Open
Abstract
Although potent direct-acting antiviral drugs for the treatment of chronic hepatitis C virus (HCV) infection are licensed, there are more than 70 million individuals suffering from chronic HCV infection. In light of the limited access to these drugs, high costs, and a lot of undiagnosed cases, it is expected that the number of HCV cases will not decrease worldwide in the next years. Therefore, and due to the paradigmatic character of HCV for deciphering the crosstalk between viral pathogens and the host cell, characterization of HCV life cycle remains a challenge. HCV belongs to the family of Flaviviridae. As an enveloped virus HCV life cycle depends in many steps on intracellular trafficking. Rab GTPases, a large family of small GTPases, play a central role in intracellular trafficking processes controlling fusion, uncoating, vesicle budding, motility by recruiting specific effector proteins. This review describes the relevance of various Rab proteins for the different steps of the HCV life cycle.
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Affiliation(s)
- Fabian Elgner
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - Eberhard Hildt
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - Daniela Bender
- Department of Virology, Paul-Ehrlich-Institut, Langen, Germany
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59
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de Moliner F, King A, Dias GG, de Lima GF, de Simone CA, da Silva Júnior EN, Vendrell M. Quinone-Derived π-Extended Phenazines as New Fluorogenic Probes for Live-Cell Imaging of Lipid Droplets. Front Chem 2018; 6:339. [PMID: 30151362 PMCID: PMC6099520 DOI: 10.3389/fchem.2018.00339] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 07/19/2018] [Indexed: 01/14/2023] Open
Abstract
We describe a new synthetic methodology for the preparation of fluorescent π-extended phenazines from the naturally-occurring naphthoquinone lapachol. These novel structures represent the first fluorogenic probes based on the phenazine scaffold for imaging of lipid droplets in live cells. Systematic characterization and analysis of the compounds in vitro and in cells led to the identification of key structural features responsible for the fluorescent behavior of quinone-derived π-extended phenazines. Furthermore, live-cell imaging experiments identified one compound (P1) as a marker for intracellular lipid droplets with minimal background and enhanced performance over the lipophilic tracker Nile Red.
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Affiliation(s)
- Fabio de Moliner
- Medical Research Council Centre for Inflammation Research, The University of Edinburgh, Edinburgh, United Kingdom
| | - Aaron King
- Medical Research Council Centre for Inflammation Research, The University of Edinburgh, Edinburgh, United Kingdom
| | - Gleiston G. Dias
- Institute of Exact Sciences, Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Guilherme F. de Lima
- Institute of Exact Sciences, Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | | | - Eufrânio N. da Silva Júnior
- Institute of Exact Sciences, Department of Chemistry, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Marc Vendrell
- Medical Research Council Centre for Inflammation Research, The University of Edinburgh, Edinburgh, United Kingdom
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60
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Trypanosoma cruzi epimastigotes store cholesteryl esters in lipid droplets after cholesterol endocytosis. Mol Biochem Parasitol 2018; 224:6-16. [PMID: 30016698 DOI: 10.1016/j.molbiopara.2018.07.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/05/2018] [Accepted: 07/10/2018] [Indexed: 11/21/2022]
Abstract
The Chagas disease agent Trypanosoma cruzi proliferates in the insect vector as highly endocytic epimastigotes that store nutrients, including lipids in reservosomes (lysosome related compartments). Although nutrient storage is important for epimastigote transformation into infective metacyclics, the epimastigote lipid droplets (LDs) remain uncharacterized. Here, we characterized the epimastigote LDs and examined their relationship with the endocytic pathway. Fluorescence microscopy using BODIPY showed that LDs have high neutral lipid content and harbor Rab18, differently from other lipid-rich organelles (such as reservosomes). Using transmission electron microscopy (TEM), we observed a close relationship between LDs and the endoplasmic reticulum, mitochondria and glycosomes. We developed a reproducible protocol to isolate LDs, and showed (by HTPLC and GC/MS analyses) that they have 89% neutral lipids and 11% phospholipids, which are likely to form the LD monolayer seen by TEM. The LD neutral lipids were mostly sterols, although triacylglycerol, diacylglycerol, monoacylglycerol and free fatty acids (FFA) were also found. Endocytosis of 3H-labeled cholesterol-BSA showed that internalized cholesterol is stored in LDs mostly in the cholesteryl ester form. Together, these results suggest that exogenous cholesterol internalized by endocytosis reaches the reservosomes and is then stored into LDs after esterification.
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61
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Jayson CBK, Arlt H, Fischer AW, Lai ZW, Farese RV, Walther TC. Rab18 is not necessary for lipid droplet biogenesis or turnover in human mammary carcinoma cells. Mol Biol Cell 2018; 29:2045-2054. [PMID: 29949452 PMCID: PMC6232964 DOI: 10.1091/mbc.e18-05-0282] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Rab GTPases recruit peripheral membrane proteins and can define organelle identity. Rab18 localizes to the endoplasmic reticulum (ER) but also to lipid droplets (LDs), where it has been implicated in effector protein recruitment and in defining LD identity. Here, we studied Rab18 localization and function in a human mammary carcinoma cell line. Rab18 localized to the ER and to LD membranes on LD induction, with the latter depending on the Rab18 activation state. In cells lacking Rab18, LDs were modestly reduced in size and numbers, but we found little evidence for Rab18 function in LD formation, LD turnover on cell starvation, or the targeting of several proteins to LDs. We conclude that Rab18 is not a general, necessary component of the protein machinery involved in LD biogenesis or turnover.
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Affiliation(s)
- Christina B K Jayson
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Henning Arlt
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Alexander W Fischer
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115.,Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, DE-20246 Hamburg, Germany
| | - Zon Weng Lai
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115.,Broad Institute of MIT and Harvard, Cambridge, MA 02142
| | - Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, Boston, MA 02115.,Department of Cell Biology, Harvard Medical School, Boston, MA 02115.,Broad Institute of MIT and Harvard, Cambridge, MA 02142.,Howard Hughes Medical Institute, Boston, MA 02115
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62
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Woo HJ, Reifman J. Genetic interaction effects reveal lipid-metabolic and inflammatory pathways underlying common metabolic disease risks. BMC Med Genomics 2018; 11:54. [PMID: 29925367 PMCID: PMC6011398 DOI: 10.1186/s12920-018-0373-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Common metabolic diseases, including type 2 diabetes, coronary artery disease, and hypertension, arise from disruptions of the body's metabolic homeostasis, with relatively strong contributions from genetic risk factors and substantial comorbidity with obesity. Although genome-wide association studies have revealed many genomic loci robustly associated with these diseases, biological interpretation of such association is challenging because of the difficulty in mapping single-nucleotide polymorphisms (SNPs) onto the underlying causal genes and pathways. Furthermore, common diseases are typically highly polygenic, and conventional single variant-based association testing does not adequately capture potentially important large-scale interaction effects between multiple genetic factors. METHODS We analyzed moderately sized case-control data sets for type 2 diabetes, coronary artery disease, and hypertension to characterize the genetic risk factors arising from non-additive, collective interaction effects, using a recently developed algorithm (discrete discriminant analysis). We tested associations of genes and pathways with the disease status while including the cumulative sum of interaction effects between all variants contained in each group. RESULTS In contrast to non-interacting SNP mapping, which produced few genome-wide significant loci, our analysis revealed extensive arrays of pathways, many of which are involved in the pathogenesis of these metabolic diseases but have not been directly identified in genetic association studies. They comprised cell stress and apoptotic pathways for insulin-producing β-cells in type 2 diabetes, processes covering different atherosclerotic stages in coronary artery disease, and elements of both type 2 diabetes and coronary artery disease risk factors (cell cycle, apoptosis, and hemostasis) associated with hypertension. CONCLUSIONS Our results support the view that non-additive interaction effects significantly enhance the level of common metabolic disease associations and modify their genetic architectures and that many of the expected genetic factors behind metabolic disease risks reside in smaller genotyping samples in the form of interacting groups of SNPs.
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Affiliation(s)
- Hyung Jun Woo
- Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, USA
| | - Jaques Reifman
- Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, USA.
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63
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Kramer DA, Quiroga AD, Lian J, Fahlman RP, Lehner R. Fasting and refeeding induces changes in the mouse hepatic lipid droplet proteome. J Proteomics 2018; 181:213-224. [DOI: 10.1016/j.jprot.2018.04.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 04/10/2018] [Accepted: 04/14/2018] [Indexed: 12/29/2022]
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64
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Zhu X, Liu Y, Zhang H, Liu P. Whole-genome RNAi screen identifies methylation-related genes influencing lipid metabolism in Caenorhabditis elegans. J Genet Genomics 2018; 45:259-272. [PMID: 29858166 DOI: 10.1016/j.jgg.2018.03.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 03/09/2018] [Accepted: 03/15/2018] [Indexed: 12/13/2022]
Abstract
Lipid droplets (LDs) are highly conserved multifunctional cellular organelles and aberrant lipid storage in LDs can lead to many metabolic diseases. However, the molecular mechanisms governing lipid dynamic changes remain elusive, and the high-throughput screen of genes influencing LD morphology was limited by lacking specific LD marker proteins in the powerful genetic tool Caenorhabditis elegans. In this study, we established a new method to conduct whole-genome RNAi screen using LD resident protein DHS-3 as a LD marker, and identified 78 genes involved in significant LD morphologic changes. Among them, mthf-1, as well as a series of methylation-related genes, was found dramatically influencing lipid metabolism. SREBP-1 and SCD1 homologs in C. elegans were involved in the lipid metabolic change of mthf-1(RNAi) worms, and the regulation of ATGL-1 also contributed to it by decreasing triacylglycerol (TAG) hydrolysis. Overall, this study not only identified important genes involved in LD dynamics, but also provided a new tool for LD study using C. elegans, with implications for the study of lipid metabolic diseases.
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Affiliation(s)
- Xiaotong Zhu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yangli Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hong Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Pingsheng Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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65
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Xu S, Zhang X, Liu P. Lipid droplet proteins and metabolic diseases. Biochim Biophys Acta Mol Basis Dis 2018; 1864:1968-1983. [DOI: 10.1016/j.bbadis.2017.07.019] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/14/2017] [Accepted: 07/19/2017] [Indexed: 12/13/2022]
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66
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Hegde B, Bodduluri SR, Satpathy SR, Alghsham RS, Jala VR, Uriarte SM, Chung DH, Lawrenz MB, Haribabu B. Inflammasome-Independent Leukotriene B 4 Production Drives Crystalline Silica-Induced Sterile Inflammation. THE JOURNAL OF IMMUNOLOGY 2018; 200:3556-3567. [PMID: 29610142 DOI: 10.4049/jimmunol.1701504] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 03/09/2018] [Indexed: 12/14/2022]
Abstract
Silicosis is a lung inflammatory disease caused by chronic exposure to crystalline silica (CS). Leukotriene B4 (LTB4) plays an important role in neutrophilic inflammation, which drives silicosis and promotes lung cancer. In this study, we examined the mechanisms involved in CS-induced inflammatory pathways. Phagocytosis of CS particles is essential for the production of LTB4 and IL-1β in mouse macrophages, mast cells, and neutrophils. Phagosomes enclosing CS particles trigger the assembly of lipidosome in the cytoplasm, which is likely the primary source of CS-induced LTB4 production. Activation of the JNK pathway is essential for both CS-induced LTB4 and IL-1β production. Studies with bafilomycin-A1- and NLRP3-deficient mice revealed that LTB4 synthesis in the lipidosome is independent of inflammasome activation. Small interfering RNA knockdown and confocal microscopy studies showed that GTPases Rab5c, Rab40c along with JNK1 are essential for lipidosome formation and LTB4 production. BI-78D3, a JNK inhibitor, abrogated CS-induced neutrophilic inflammation in vivo in an air pouch model. These results highlight an inflammasome-independent and JNK activation-dependent lipidosome pathway as a regulator of LTB4 synthesis and CS-induced sterile inflammation.
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Affiliation(s)
- Bindu Hegde
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202.,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
| | - Sobha R Bodduluri
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202.,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
| | - Shuchismita R Satpathy
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202.,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
| | - Ruqaih S Alghsham
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202.,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
| | - Venkatakrishna R Jala
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202.,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
| | - Silvia M Uriarte
- Department of Medicine, University of Louisville Health Sciences Center, Louisville, KY 40202
| | - Dong-Hoon Chung
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202
| | - Matthew B Lawrenz
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202
| | - Bodduluri Haribabu
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 40202; .,James Graham Brown Cancer Center, University of Louisville Health Sciences Center, Louisville, KY 40202; and
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67
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Tan Z, Xiao L, Tang M, Bai F, Li J, Li L, Shi F, Li N, Li Y, Du Q, Lu J, Weng X, Yi W, Zhang H, Fan J, Zhou J, Gao Q, Onuchic JN, Bode AM, Luo X, Cao Y. Targeting CPT1A-mediated fatty acid oxidation sensitizes nasopharyngeal carcinoma to radiation therapy. Am J Cancer Res 2018; 8:2329-2347. [PMID: 29721083 PMCID: PMC5928893 DOI: 10.7150/thno.21451] [Citation(s) in RCA: 152] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 02/28/2018] [Indexed: 12/17/2022] Open
Abstract
Nasopharyngeal carcinoma (NPC) has a particularly high prevalence in southern China, southeastern Asia and northern Africa. Radiation resistance remains a serious obstacle to successful treatment in NPC. This study aimed to explore the metabolic feature of radiation-resistant NPC cells and identify new molecular-targeted agents to improve the therapeutic effects of radiotherapy in NPC. Methods: Radiation-responsive and radiation-resistant NPC cells were used as the model system in vitro and in vivo. Metabolomics approach was used to illustrate the global metabolic changes. 13C isotopomer tracing experiment and Seahorse XF analysis were undertaken to determine the activity of fatty acid oxidation (FAO). qRT-PCR was performed to evaluate the expression of essential FAO genes including CPT1A. NPC tumor tissue microarray was used to investigate the prognostic role of CPT1A. Either RNA interference or pharmacological blockade by Etomoxir were used to inhibit CPT1A. Radiation resistance was evaluated by colony formation assay. Mitochondrial membrane potential, apoptosis and neutral lipid content were measured by flow cytometry analysis using JC-1, Annexin V and LipidTOX Red probe respectively. Molecular markers of mitochondrial apoptosis were detected by western blot. Xenografts were treated with Etomoxir, radiation, or a combination of Etomoxir and radiation. Mitochondrial apoptosis and lipid droplets content of tumor tissues were detected by cleaved caspase 9 and Oil Red O staining respectively. Liquid chromatography coupled with tandem mass spectrometry approach was used to identify CPT1A-binding proteins. The interaction of CPT1A and Rab14 were detected by immunoprecipitation, immunofluorescence and in situ proximity ligation analysis. Fragment docking and direct coupling combined computational protein-protein interaction prediction method were used to predict the binding interface. Fatty acid trafficking was measured by pulse-chase assay using BODIPY C16 and MitoTracker Red probe. Results: FAO was active in radiation-resistant NPC cells, and the rate-limiting enzyme of FAO, carnitine palmitoyl transferase 1 A (CPT1A), was consistently up-regulated in these cells. The protein level of CPT1A was significantly associated with poor overall survival of NPC patients following radiotherapy. Inhibition of CPT1A re-sensitized NPC cells to radiation therapy by activating mitochondrial apoptosis both in vitro and in vivo. In addition, we identified Rab14 as a novel CPT1A binding protein. The CPT1A-Rab14 interaction facilitated fatty acid trafficking from lipid droplets to mitochondria, which decreased radiation-induced lipid accumulation and maximized ATP production. Knockdown of Rab14 attenuated CPT1A-mediated fatty acid trafficking and radiation resistance. Conclusion: An active FAO is a vital signature of NPC radiation resistance. Targeting CPT1A could be a beneficial regimen to improve the therapeutic effects of radiotherapy in NPC patients. Importantly, the CPT1A-Rab14 interaction plays roles in CPT1A-mediated radiation resistance by facilitating fatty acid trafficking. This interaction could be an attractive interface for the discovery of novel CPT1A inhibitors.
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68
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Elander PH, Minina EA, Bozhkov PV. Autophagy in turnover of lipid stores: trans-kingdom comparison. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:1301-1311. [PMID: 29309625 DOI: 10.1093/jxb/erx433] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 11/14/2017] [Indexed: 05/24/2023]
Abstract
Lipids and their cellular utilization are essential for life. Not only are lipids energy storage molecules, but their diverse structural and physical properties underlie various aspects of eukaryotic biology, such as membrane structure, signalling, and trafficking. In the ever-changing environment of cells, lipids, like other cellular components, are regularly recycled to uphold the housekeeping processes required for cell survival and organism longevity. The ways in which lipids are recycled, however, vary between different phyla. For example, animals and plants have evolved distinct lipid degradation pathways. The major cell recycling system, autophagy, has been shown to be instrumental for both differentiation of specialized fat storing-cells, adipocytes, and fat degradation in animals. Does plant autophagy play a similar role in storage and degradation of lipids? In this review, we discuss and compare implications of bulk autophagy and its selective route, lipophagy, in the turnover of lipid stores in animals, fungi, and plants.
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Affiliation(s)
- Pernilla H Elander
- Department of Molecular Sciences, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala, Sweden
| | - Elena A Minina
- Department of Molecular Sciences, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala, Sweden
| | - Peter V Bozhkov
- Department of Molecular Sciences, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala, Sweden
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69
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Banworth MJ, Li G. Consequences of Rab GTPase dysfunction in genetic or acquired human diseases. Small GTPases 2018. [PMID: 29239692 DOI: 10.1080/215412481397833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2023] Open
Abstract
Rab GTPases are important regulators of intracellular membrane trafficking in eukaryotes. Both activating and inactivating mutations in Rab genes have been identified and implicated in human diseases ranging from neurological disorders to cancer. In addition, altered Rab expression is often associated with disease prognosis. As such, the study of diseases associated with Rabs or Rab-interacting proteins has shed light on the important role of intracellular membrane trafficking in disease etiology. In this review, we cover recent advances in the field with an emphasis on cellular mechanisms.
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Affiliation(s)
- Marcellus J Banworth
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
| | - Guangpu Li
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
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70
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Abstract
GTP-ases of the Rab family (about 70 in human) are key regulators of intracellular transport and membrane trafficking in eukaryotic cells. Remarkably, almost one third associate with membranes of the Golgi complex and TGN (trans-Golgi network). Through interactions with a variety of effectors that include molecular motors, tethering complexes, scaffolding proteins and lipid kinases, they play an important role in maintaining Golgi architecture.
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Affiliation(s)
- Bruno Goud
- a Institut Curie, PSL Research University, CNRS, UMR 144, Molecular Mechanisms of Intracellular Transport , Paris , France
| | - Shijie Liu
- b Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , USA
| | - Brian Storrie
- b Department of Physiology and Biophysics , University of Arkansas for Medical Sciences , Little Rock , USA
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71
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Xu D, Li Y, Wu L, Li Y, Zhao D, Yu J, Huang T, Ferguson C, Parton RG, Yang H, Li P. Rab18 promotes lipid droplet (LD) growth by tethering the ER to LDs through SNARE and NRZ interactions. J Cell Biol 2018; 217:975-995. [PMID: 29367353 PMCID: PMC5839781 DOI: 10.1083/jcb.201704184] [Citation(s) in RCA: 148] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 10/12/2017] [Accepted: 12/22/2017] [Indexed: 12/16/2022] Open
Abstract
Lipid incorporation from endoplasmic reticulum (ER) to lipid droplet (LD) is important in controlling LD growth and intracellular lipid homeostasis. However, the molecular link mediating ER and LD cross talk remains elusive. Here, we identified Rab18 as an important Rab guanosine triphosphatase in controlling LD growth and maturation. Rab18 deficiency resulted in a drastically reduced number of mature LDs and decreased lipid storage, and was accompanied by increased ER stress. Rab3GAP1/2, the GEF of Rab18, promoted LD growth by activating and targeting Rab18 to LDs. LD-associated Rab18 bound specifically to the ER-associated NAG-RINT1-ZW10 (NRZ) tethering complex and their associated SNAREs (Syntaxin18, Use1, BNIP1), resulting in the recruitment of ER to LD and the formation of direct ER-LD contact. Cells with defects in the NRZ/SNARE complex function showed reduced LD growth and lipid storage. Overall, our data reveal that the Rab18-NRZ-SNARE complex is critical protein machinery for tethering ER-LD and establishing ER-LD contact to promote LD growth.
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Affiliation(s)
- Dijin Xu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yuqi Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Lizhen Wu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ying Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Dongyu Zhao
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jinhai Yu
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Tuozhi Huang
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Charles Ferguson
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia
| | - Robert G Parton
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia.,Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Australia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Peng Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
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72
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Banworth MJ, Li G. Consequences of Rab GTPase dysfunction in genetic or acquired human diseases. Small GTPases 2017; 9:158-181. [PMID: 29239692 DOI: 10.1080/21541248.2017.1397833] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Rab GTPases are important regulators of intracellular membrane trafficking in eukaryotes. Both activating and inactivating mutations in Rab genes have been identified and implicated in human diseases ranging from neurological disorders to cancer. In addition, altered Rab expression is often associated with disease prognosis. As such, the study of diseases associated with Rabs or Rab-interacting proteins has shed light on the important role of intracellular membrane trafficking in disease etiology. In this review, we cover recent advances in the field with an emphasis on cellular mechanisms.
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Affiliation(s)
- Marcellus J Banworth
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
| | - Guangpu Li
- a Department of Biochemistry and Molecular Biology , University of Oklahoma Health Sciences Center , Oklahoma City , OK , USA
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73
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Zhang J, Lan Y, Sanyal S. Modulation of Lipid Droplet Metabolism-A Potential Target for Therapeutic Intervention in Flaviviridae Infections. Front Microbiol 2017; 8:2286. [PMID: 29234310 PMCID: PMC5712332 DOI: 10.3389/fmicb.2017.02286] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 11/06/2017] [Indexed: 12/21/2022] Open
Abstract
Lipid droplets (LDs) are endoplasmic reticulum (ER)-related dynamic organelles that store and regulate fatty acids and neutral lipids. They play a central role in cellular energy storage, lipid metabolism and cellular homeostasis. It has become evident that viruses have co-evolved in order to exploit host lipid metabolic pathways. This is especially characteristic of the Flaviviridae family, including hepatitis C virus (HCV) and several flaviviruses. Devoid of an appropriate lipid biosynthetic machinery of their own, these single-strand positive-sense RNA viruses can induce dramatic changes in host metabolic pathways to establish a favorable environment for viral multiplication and acquire essential components to facilitate their assembly and traffic. Here we have reviewed the current knowledge on the intracellular life cycle of those from the Flaviviridae family, with particular emphasis on HCV and dengue virus (DENV), and their association with the biosynthesis and metabolism of LDs, with the aim to identify potential antiviral targets for development of novel therapeutic interventions.
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Affiliation(s)
- Jingshu Zhang
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China
| | - Yun Lan
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China
| | - Sumana Sanyal
- HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China.,School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China
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74
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Maternal consumption of fish oil programs reduced adiposity in broiler chicks. Sci Rep 2017; 7:13129. [PMID: 29030616 PMCID: PMC5640664 DOI: 10.1038/s41598-017-13519-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 09/25/2017] [Indexed: 12/20/2022] Open
Abstract
Maternal intake of eicosapentaenoic acid (EPA; 20:5 n-3) and docosahexaenoic acid (22:6 n-3) has been associated with reduced adiposity in children, suggesting the possibility to program adipose development through dietary fatty acids before birth. This study determined if enriching the maternal diet in fish oil, the primary source of EPA and DHA, affected adipose development in offspring. Broiler chickens were used because they are obesity-prone, and because fatty acids provided to the embryo can be manipulated through the hen diet. Hens were fed diets supplemented (2.8% wt:wt) with corn oil (CO; n-6) or fish oil (FO; n-3) for 28 d. Chicks from both maternal diet groups were fed the same diet after hatch. Maternal FO consumption enriched chick adipose tissue in EPA and DHA and reduced adiposity by promoting more, but smaller, adipocytes. This adipocyte profile was paralleled by lower expression of the adipogenic regulator PPARG and its co-activator PPARGC1B, and elevated expression of LPL. Proteomics identified 95 differentially abundant proteins between FO and CO adipose tissue, including components of glucose metabolism, lipid droplet trafficking, and cytoskeletal organization. These results demonstrate that the maternal dietary fatty acid profile programs offspring adipose development.
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75
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Abstract
Lipid droplets (LDs) are ubiquitous organelles that store neutral lipids for energy or membrane synthesis and act as hubs for metabolic processes. Cells generate LDs de novo, converting cells to emulsions with LDs constituting the dispersed oil phase in the aqueous cytoplasm. Here we review our current view of LD biogenesis. We present a model of LD formation from the ER in distinct steps and highlight the biology of proteins that govern this biophysical process. Areas of incomplete knowledge are identified, as are connections with physiology and diseases linked to alterations in LD biology.
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Affiliation(s)
- Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142.,Howard Hughes Medical Institute, Boston, Massachusetts 02115
| | - Jeeyun Chung
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
| | - Robert V Farese
- Department of Genetics and Complex Diseases, Harvard T.H. Chan School of Public Health, Boston, Massachusetts 02115; , .,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115.,Broad Institute of Harvard and MIT, Cambridge, Massachusetts 02142
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76
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Luo X, Li C, Tan R, Xu X, Wu WKK, Satoh A, Wang T, Yu S. A RasGAP, DAB2IP, regulates lipid droplet homeostasis by serving as GAP toward RAB40C. Oncotarget 2017; 8:85415-85427. [PMID: 29156729 PMCID: PMC5689619 DOI: 10.18632/oncotarget.19960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 05/08/2017] [Indexed: 12/13/2022] Open
Abstract
Lipid droplet (LD) homeostasis involves activities of various RAB small GTPases. Recently, we found RAB40C was one of the RAB proteins regulating LD homeostasis. RAB40C contains a unique SOCS domain that is required for clustering of LDs. However, its precise functional role in LD homeostasis and mechanism of regulation remain largely unknown. In this study, we observed over-accumulation of LDs in cells with RAB40C deleted by Crispr-Cas9 editing. RAB40C appeared to reduce LD accumulation after long term incubation of cells with oleic acid (24 hours). Unexpectedly, we found that Ras GTPase activating protein (GAP), DAB2IP, bound to RAB40C mainly via its GAP domain and could serve as RAB40C GAP. Studies involving overexpression of DAB2IP and its GAP defective mutant and siRNA depletion of DAB2IP all confirmed that DAB2IP negatively regulated the effect of RAB40C on LD homeostasis. These results provide a novel perspective on the regulation of RAB40C and implicate various signalling pathways regulated by DAB2IP, which may play a role in LD homeostasis via RAB40C.
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Affiliation(s)
- Xiaomin Luo
- Guangdong and Shenzhen Key Laboratory of Male Reproductive Medicine and Genetics, Institute of Urology, Peking University Shenzhen Hospital, Shenzhen PKU-HKUST Medical Center, Shenzhen, P.R. China.,School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
| | - Chunman Li
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
| | - Ran Tan
- Department of Anesthesia, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
| | - Xiaohui Xu
- Department of Anesthesia, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
| | - William K K Wu
- School of Pharmaceutical Sciences, Xiamen University, Fujian, P.R. China
| | - Ayano Satoh
- The Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Tuanlao Wang
- Department of Anesthesia, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
| | - Sidney Yu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China.,Epithelial Cell Biology Research Centre, The Chinese University of Hong Kong, Hong Kong SAR, P.R. China
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77
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The Role of Lipid Bodies in the Microglial Aging Process and Related Diseases. Neurochem Res 2017; 42:3140-3148. [PMID: 28699057 DOI: 10.1007/s11064-017-2351-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 02/22/2017] [Accepted: 07/07/2017] [Indexed: 01/08/2023]
Abstract
Lipid bodies (LBs) have long been considered to be organelles merely for the storage of neutral lipids. However, recent studies have shown the significance of LBs in signal transduction, especially in glial cells, including microglia. Microglial cells are the resident mononuclear phagocytes in the central nervous system and have a close relationship with the aging process and neurodegenerative diseases. Evidence suggests that LBs accumulate and are remodeled during the aging process and the development of neuroinflammatory conditions. However, the mechanisms underlying the formation of LBs under these conditions and the mechanism by which LB remodeling influences the progression of neurodegeneration remain to be clarified. In this review, we have summarized the findings from recent studies with the aim of further elucidating these issues.
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78
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Schulze RJ, Sathyanarayan A, Mashek DG. Breaking fat: The regulation and mechanisms of lipophagy. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28642194 DOI: 10.1016/j.bbalip.2017.06.008] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Lipophagy is defined as the autophagic degradation of intracellular lipid droplets (LDs). While the field of lipophagy research is relatively young, an expansion of research in this area over the past several years has greatly advanced our understanding of lipophagy. Since its original characterization in fasted liver, the contribution of lipophagy is now recognized in various organisms, cell types, metabolic states and disease models. Moreover, recent studies provide exciting new insights into the underlying mechanisms of lipophagy induction as well as the consequences of lipophagy on cell metabolism and signaling. This review summarizes recent work focusing on LDs and lipophagy as well as highlighting challenges and future directions of research as our understanding of lipophagy continues to grow and evolve. 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)
- Ryan J Schulze
- Department of Biochemistry and Molecular Biology and the Center for Digestive Diseases, Mayo Clinic, Rochester, MN, United States
| | - Aishwarya Sathyanarayan
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States
| | - Douglas G Mashek
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, United States; Department of Medicine, Division of Diabetes, Endocrinology and Metabolism, University of Minnesota, Minneapolis, MN, United States.
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79
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Bersuker K, Olzmann JA. Establishing the lipid droplet proteome: Mechanisms of lipid droplet protein targeting and degradation. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28627435 DOI: 10.1016/j.bbalip.2017.06.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are ubiquitous, endoplasmic reticulum (ER)-derived organelles that mediate the sequestration of neutral lipids (e.g. triacylglycerol and sterol esters), providing a dynamic cellular storage depot for rapid lipid mobilization in response to increased cellular demands. LDs have a unique ultrastructure, consisting of a core of neutral lipids encircled by a phospholipid monolayer that is decorated with integral and peripheral proteins. The LD proteome contains numerous lipid metabolic enzymes, regulatory scaffold proteins, proteins involved in LD clustering and fusion, and other proteins of unknown functions. The cellular role of LDs is inherently determined by the composition of its proteome and alteration of the LD protein coat provides a powerful mechanism to adapt LDs to fluctuating metabolic states. Here, we review the current understanding of the molecular mechanisms that govern LD protein targeting and degradation. 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)
- Kirill Bersuker
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA
| | - James A Olzmann
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA.
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80
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Schulze RJ, Drižytė K, Casey CA, McNiven MA. Hepatic Lipophagy: New Insights into Autophagic Catabolism of Lipid Droplets in the Liver. Hepatol Commun 2017; 1:359-369. [PMID: 29109982 PMCID: PMC5669271 DOI: 10.1002/hep4.1056] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The liver is a central fat‐storage organ, making it especially susceptible to steatosis as well as subsequent inflammation and cirrhosis. The mechanisms by which the liver mobilizes stored lipid for energy production, however, remain incompletely defined. The catabolic process of autophagy, a well‐known process of bulk cytoplasmic recycling and cellular self‐regeneration, is a central regulator of lipid metabolism in the liver. In the past decade, numerous studies have examined a selective form of autophagy that specifically targets a unique neutral lipid storage organelle, the lipid droplet, to better understand the function for this process in hepatocellular fatty acid metabolism. In the liver (and other oxidative tissues), this specialized pathway, lipophagy, likely plays as important a role in lipid turnover as conventional lipase‐driven lipolysis. In this review, we highlight several recent studies that have contributed to our understanding about the regulation and effects of hepatic lipophagy. (Hepatology Communications 2017;1:359–369)
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Affiliation(s)
- Ryan J Schulze
- Department of Biochemistry and Molecular Biology and the Center for Digestive Diseases, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
| | - Kristina Drižytė
- Department of Biochemistry and Molecular Biology and the Center for Digestive Diseases, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA.,Biochemistry and Molecular Biology Program, Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, 200 1st St SW, Rochester, MN 55905, USA
| | - Carol A Casey
- Department of Internal Medicine, University of Nebraska Medical Center, 988090 Nebraska Medical Center, Omaha, NE, 68198, USA.,Research Service, VA Nebraska-Western Iowa Health Care System (VA NWIHCS), Omaha, NE, 68198, USA
| | - Mark A McNiven
- Department of Biochemistry and Molecular Biology and the Center for Digestive Diseases, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
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81
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Golgi trafficking defects in postnatal microcephaly: The evidence for “Golgipathies”. Prog Neurobiol 2017; 153:46-63. [DOI: 10.1016/j.pneurobio.2017.03.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 02/22/2017] [Accepted: 03/29/2017] [Indexed: 12/17/2022]
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82
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Nolan SJ, Romano JD, Coppens I. Host lipid droplets: An important source of lipids salvaged by the intracellular parasite Toxoplasma gondii. PLoS Pathog 2017; 13:e1006362. [PMID: 28570716 PMCID: PMC5469497 DOI: 10.1371/journal.ppat.1006362] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 06/13/2017] [Accepted: 04/18/2017] [Indexed: 12/13/2022] Open
Abstract
Toxoplasma is an obligate intracellular parasite that replicates in mammalian cells within a parasitophorous vacuole (PV) that does not fuse with any host organelles. One mechanism developed by the parasite for nutrient acquisition is the attraction of host organelles to the PV. Here, we examined the exploitation of host lipid droplets (LD), ubiquitous fat storage organelles, by Toxoplasma. We show that Toxoplasma replication is reduced in host cells that are depleted of LD, or impaired in TAG lipolysis or fatty acid catabolism. In infected cells, the number of host LD and the expression of host LD-associated genes (ADRP, DGAT2), progressively increase until the onset of parasite replication. Throughout infection, the PV are surrounded by host LD. Toxoplasma is capable of accessing lipids stored in host LD and incorporates these lipids into its own membranes and LD. Exogenous addition of oleic acid stimulates LD biogenesis in the host cell and results in the overaccumulation of neutral lipids in very large LD inside the parasite. To access LD-derived lipids, Toxoplasma intercepts and internalizes within the PV host LD, some of which remaining associated with Rab7, which become wrapped by an intravacuolar network of membranes (IVN). Mutant parasites impaired in IVN formation display diminished capacity of lipid uptake from host LD. Moreover, parasites lacking an IVN-localized phospholipase A2 are less proficient in salvaging lipids from host LD in the PV, suggesting a major contribution of the IVN for host LD processing in the PV and, thus lipid content release. Interestingly, gavage of parasites with lipids unveils, for the first time, the presence in Toxoplasma of endocytic-like structures containing lipidic material originating from the PV lumen. This study highlights the reliance of Toxoplasma on host LD for its intracellular development and the parasite’s capability in scavenging neutral lipids from host LD. Toxoplasma is an obligate intracellular pathogen that multiplies in mammalian cells within a specialized compartment, named the parasitophorous vacuole (PV). While the vacuole does not fuse with host organelles, the parasite scavenges nutrients, including lipids, from these compartments. Present in all mammalian cells, lipid droplets (LD) are dynamic structures that store neutral lipids. Whether Toxoplasma targets host LD for their nutritional content remains to be investigated. We demonstrate that the parasite relies on host LD lipids and their lipolytic enzymatic activities to grow. Toxoplasma salvages lipids from host LD, which surround the PV and, at least partially, accesses these lipids by intercepting and engulfing within the PV host Rab7-associated LD. In the PV lumen, a parasite lipase releases lipids from host LD, thus making them available to the parasite. Exogenous addition of fatty acids stimulates host LD biogenesis and results in the accumulation of enlarged LD containing neutral lipids in Toxoplasma. This study highlights the ability of Toxoplasma to scavenge and store lipids from host LD. Interestingly, exposure of Toxoplasma to excess lipids reveals, for the first time, coated invaginations of the parasite’s plasma membrane and cytoplasmic vesicles containing lipids originating from the PV lumen, potentially involved in endocytosis.
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Affiliation(s)
- Sabrina J. Nolan
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Julia D. Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail:
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83
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Teo WX, Yang Z, Kerr MC, Luo L, Guo Z, Alexandrov K, Stow JL, Teasdale RD. Salmonella effector SopD2 interferes with Rab34 function. Cell Biol Int 2017; 41:433-446. [PMID: 28185347 DOI: 10.1002/cbin.10739] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 01/31/2017] [Indexed: 11/10/2022]
Abstract
Many intracellular pathogens have evolved highly specialized mechanisms to isolate themselves from the host cell's innate immune response while still obtaining the necessary nutrients to survive. Salmonella utilizes type 3 secretion systems (T3SSs) to deliver bacterial proteins called effectors, across the encompassing Salmonella Containing vacuole (SCV) membrane, to subvert the host's membrane trafficking pathways and alter other cellular processes. The Salmonella Pathogenicity Island (SPI)-2 effector SopD2 has recently been demonstrated to modulate multiple members of the Rab GTPase family such as Rab7, Rab8, Rab10, and Rab32 (D'Costa et al., , Cell Reports, 12:1508-18; Spano et al., , Cell Host & Microbe, 19:216-26). Here, we demonstrate the additional capacity of SopD2 to bind Rab34 and modulate its function. Our data indicate that depletion of Rab34 delays maturation of the SCV, and consequently, inhibits intracellular Salmonella enterica serotype typhimurium (S. typhimurium) growth. Interestingly, intracellular growth of the S. typhimurium lacking SopD2 was severely impaired in Rab34-depleted cells, suggesting a compounding virulence effect. Overall this study reveals an additional member of the Rab GTPase family, Rab34, that is modulated by SopD2 and provides insight into its role in Salmonella biology.
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Affiliation(s)
- Wei Xuan Teo
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Zhe Yang
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Markus Charles Kerr
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Lin Luo
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Zhong Guo
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Kirill Alexandrov
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Jenny Lea Stow
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
| | - Rohan David Teasdale
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD, 4072, Australia
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84
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Abstract
Lipid droplets are the universal cellular organelles for the transient or long-term storage of lipids. The number, size and composition of lipid droplets vary greatly within cells in a homogenous population as well as in different cell types. The variability of intracellular lipid-storage organelles reflects the diversification of lipid droplet composition and function. Lipid droplet diversification results, for example, in two cellular lipid droplet populations that are prone to diminish and grow, respectively. The aberrant accumulation or depletion of lipids are hallmarks or causes of various human pathologies. Thus, a better understanding of the origins of lipid droplet diversification is not only a fascinating cell biology question but also potentially serves to improve comprehension of pathologies that entail the accumulation of lipids. This Commentary covers the lipid droplet life cycle and highlights the early steps during lipid droplet biogenesis, which we propose to be the potential driving forces of lipid droplet diversification.
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Affiliation(s)
- 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; 24 rue Lhomond, Paris 75005, France
| | - Mathias Beller
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany .,Systems Biology of Lipid Metabolism, Heinrich Heine University, Universitätsstr. 1, Düsseldorf 40225, Germany
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85
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Thul PJ, Tschapalda K, Kolkhof P, Thiam AR, Oberer M, Beller M. Lipid droplet subset targeting of the Drosophila protein CG2254/dmLdsdh1. J Cell Sci 2017; 130:3141-3157. [DOI: 10.1242/jcs.199661] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 07/26/2017] [Indexed: 01/02/2023] Open
Abstract
Lipid droplets (LDs) are the principal organelles of lipid storage. They consist of a hydrophobic core of storage lipids, surrounded by a phospholipid monolayer with proteins attached. While some of these proteins are essential to regulate cellular and organismic lipid metabolism, key questions concerning LD protein function, such as their targeting to LDs, are still unanswered. Intriguingly, some proteins are restricted to LD subsets by an as yet unknown mechanism. This finding makes LD targeting even more complex.
Here, we characterize the Drosophila protein CG2254 which targets LD subsets in cultured cells and different larval Drosophila tissues, where the prevalence of LD subsets appears highly dynamic. We find that an amphipathic amino acid stretch mediates CG2254 LD localization. Additionally, we identified a juxtaposed sequence stretch limiting CG2254 localization to LD subsets. This sequence is sufficient to restrict a chimeric protein - consisting of the subset targeting sequence introduced to an otherwise pan LD localized protein sequence - to LD subsets. Based on its subcellular localization and annotated function, we suggest to rename CG2254 to Lipid droplet subset dehydrogenase 1 (Ldsdh1).
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Affiliation(s)
- Peter J. Thul
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Department of Molecular Developmental Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Kirsten Tschapalda
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Department of Molecular Developmental Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Systems Biology of Lipid Metabolism, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Department of Chemical Biology, Max Planck Institute for Molecular Physiology, Dortmund, Germany
| | - Petra Kolkhof
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Abdou Rachid Thiam
- Laboratoire de Physique Statistique, Ecole Normale Superieure, PSL Research University, Universite de Paris Diderot Sorbonne Paris-Cite, Paris, France
| | - Monika Oberer
- Institute of Molecular Biosciences, BioTechMed Graz, University of Graz, Austria
| | - Mathias Beller
- Institute for Mathematical Modeling of Biological Systems, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Systems Biology of Lipid Metabolism, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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86
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Zhi Y, Taylor MC, Campbell PM, Warden AC, Shrestha P, El Tahchy A, Rolland V, Vanhercke T, Petrie JR, White RG, Chen W, Singh SP, Liu Q. Comparative Lipidomics and Proteomics of Lipid Droplets in the Mesocarp and Seed Tissues of Chinese Tallow ( Triadica sebifera). FRONTIERS IN PLANT SCIENCE 2017; 8:1339. [PMID: 28824675 PMCID: PMC5541829 DOI: 10.3389/fpls.2017.01339] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 07/18/2017] [Indexed: 05/04/2023]
Abstract
Lipid droplets (LDs) are composed of a monolayer of phospholipids (PLs), surrounding a core of non-polar lipids that consist mostly of triacylglycerols (TAGs) and to a lesser extent diacylglycerols. In this study, lipidome analysis illustrated striking differences in non-polar lipids and PL species between LDs derived from Triadica sebifera seed kernels and mesocarp. In mesocarp LDs, the most abundant species of TAG contained one C18:1 and two C16:0 and fatty acids, while TAGs containing three C18 fatty acids with higher level of unsaturation were dominant in the seed kernel LDs. This reflects the distinct differences in fatty acid composition of mesocarp (palmitate-rich) and seed-derived oil (α-linoleneate-rich) in T. sebifera. Major PLs in seed LDs were found to be rich in polyunsaturated fatty acids, in contrast to those with relatively shorter carbon chain and lower level of unsaturation in mesocarp LDs. The LD proteome analysis in T. sebifera identified 207 proteins from mesocarp, and 54 proteins from seed kernel, which belong to various functional classes including lipid metabolism, transcription and translation, trafficking and transport, cytoskeleton, chaperones, and signal transduction. Oleosin and lipid droplets associated proteins (LDAP) were found to be the predominant proteins associated with LDs in seed and mesocarp tissues, respectively. We also show that LDs appear to be in close proximity to a number of organelles including the endoplasmic reticulum, mitochondria, peroxisomes, and Golgi apparatus. This comparative study between seed and mesocarp LDs may shed some light on the structure of plant LDs and improve our understanding of their functionality and cellular metabolic networks in oleaginous plant tissues.
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Affiliation(s)
- Yao Zhi
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China
- CSIRO Agriculture and FoodCanberra, ACT, Australia
| | | | | | | | | | | | | | | | | | | | - Wenli Chen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural UniversityWuhan, China
- *Correspondence: Wenli Chen
| | | | - Qing Liu
- CSIRO Agriculture and FoodCanberra, ACT, Australia
- Qing Liu
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87
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Boschi F, Rizzatti V, Zamboni M, Sbarbati A. Simulating the dynamics of lipid droplets in adipocyte differentiation. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2017; 138:65-71. [PMID: 27886716 DOI: 10.1016/j.cmpb.2016.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 10/03/2016] [Accepted: 10/18/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND Lipid droplets are cellular organelles that regulate the storage and hydrolysis of neutral lipids. The dynamic of lipid droplets (LDs), during the differentiation process from fibroblast-like cells into adipocyte, is strictly related to the lipid storage in cells. The number and size of the LDs depends on the lipidic or lipolytic stimulations to which the cells are exposed. METHOD Here, we propose a computational approach to study the processes regulating the LDs' number and growth/reduction in size using Monte Carlo simulations. The number and size of LDs are measured before and after experimental treatment in 3T3-L1 cell cultures. The algorithms simulating the evolution from basal to differentiate (lipidic or lipolytic) conditions are here detailed step by step. The algorithms can mimic thousand interacting events between LDs or squeezing/enlargement events of a single LD in a very brief computational time, from seconds up to few minutes. RESULTS The main processes regulating the interactions between LDs are here presented, and for each of them, all the needed information to re-write the computational routine are provided. More specifically, the results obtained, analyzing the fusion process between LDs, are here presented. CONCLUSIONS Here, we would like to supply the basis to explore the dynamics of lipid storage in cells with a computational approach and to encourage the applications of numerical simulation to cell studies.
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Affiliation(s)
- Federico Boschi
- Department of Computer Science, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy.
| | - Vanni Rizzatti
- Department of Medicine, Geriatric Section, University of Verona, Piazzale Stefani 1, 37126 Verona, Italy
| | - Mauro Zamboni
- Department of Medicine, Geriatric Section, University of Verona, Piazzale Stefani 1, 37126 Verona, Italy
| | - Andrea Sbarbati
- Department of Neurological and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy
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88
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Li C, Luo X, Zhao S, Siu GK, Liang Y, Chan HC, Satoh A, Yu SS. COPI-TRAPPII activates Rab18 and regulates its lipid droplet association. EMBO J 2016; 36:441-457. [PMID: 28003315 DOI: 10.15252/embj.201694866] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 11/11/2016] [Accepted: 11/16/2016] [Indexed: 11/09/2022] Open
Abstract
The transport protein particle (TRAPP) was initially identified as a vesicle tethering factor in yeast and as a guanine nucleotide exchange factor (GEF) for Ypt1/Rab1. In mammals, structures and functions of various TRAPP complexes are beginning to be understood. We found that mammalian TRAPPII was a GEF for both Rab18 and Rab1. Inactivation of TRAPPII-specific subunits by various methods including siRNA depletion and CRISPR-Cas9-mediated deletion reduced lipolysis and resulted in aberrantly large lipid droplets. Recruitment of Rab18 onto lipid droplet (LD) surface was defective in TRAPPII-deleted cells, but the localization of Rab1 on Golgi was not affected. COPI regulates LD homeostasis. We found that the previously documented interaction between TRAPPII and COPI was also required for the recruitment of Rab18 to the LD We hypothesize that the interaction between COPI and TRAPPII helps bring TRAPPII onto LD surface, and TRAPPII, in turn, activates Rab18 and recruits it on the LD surface to facilitate its functions in LD homeostasis.
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Affiliation(s)
- Chunman Li
- Department of Anatomy, Histology and Developmental Biology, School of Basic Medical Sciences, Health Science Centre, Shenzhen University, Shenzhen, China.,School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Xiaomin Luo
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Shan Zhao
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Gavin Ky Siu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Yongheng Liang
- Key Laboratory of Agricultural Environmental Microbiology of MOA, College of Life Sciences, Nanjing Agricultural University, Nanjing, China
| | - Hsiao Chang Chan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China.,Epithelial Cell Biology Research Centre, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Ayano Satoh
- The Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan
| | - Sidney Sb Yu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China .,Epithelial Cell Biology Research Centre, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
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89
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Gentile G, Ceccarelli M, Micheli L, Tirone F, Cavallaro S. Functional Genomics Identifies Tis21-Dependent Mechanisms and Putative Cancer Drug Targets Underlying Medulloblastoma Shh-Type Development. Front Pharmacol 2016; 7:449. [PMID: 27965576 PMCID: PMC5127835 DOI: 10.3389/fphar.2016.00449] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 11/09/2016] [Indexed: 12/11/2022] Open
Abstract
We have recently generated a novel medulloblastoma (MB) mouse model with activation of the Shh pathway and lacking the MB suppressor Tis21 (Patched1+/-/Tis21KO ). Its main phenotype is a defect of migration of the cerebellar granule precursor cells (GCPs). By genomic analysis of GCPs in vivo, we identified as drug target and major responsible of this defect the down-regulation of the promigratory chemokine Cxcl3. Consequently, the GCPs remain longer in the cerebellum proliferative area, and the MB frequency is enhanced. Here, we further analyzed the genes deregulated in a Tis21-dependent manner (Patched1+/-/Tis21 wild-type vs. Ptch1+/-/Tis21 knockout), among which are a number of down-regulated tumor inhibitors and up-regulated tumor facilitators, focusing on pathways potentially involved in the tumorigenesis and on putative new drug targets. The data analysis using bioinformatic tools revealed: (i) a link between the Shh signaling and the Tis21-dependent impairment of the GCPs migration, through a Shh-dependent deregulation of the clathrin-mediated chemotaxis operating in the primary cilium through the Cxcl3-Cxcr2 axis; (ii) a possible lineage shift of Shh-type GCPs toward retinal precursor phenotype, i.e., the neural cell type involved in group 3 MB; (iii) the identification of a subset of putative drug targets for MB, involved, among the others, in the regulation of Hippo signaling and centrosome assembly. Finally, our findings define also the role of Tis21 in the regulation of gene expression, through epigenetic and RNA processing mechanisms, influencing the fate of the GCPs.
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Affiliation(s)
- Giulia Gentile
- Institute of Neurological Sciences, National Research Council Catania, Italy
| | - Manuela Ceccarelli
- Institute of Cell Biology and Neurobiology, National Research Council, Fondazione Santa Lucia Rome, Italy
| | - Laura Micheli
- Institute of Cell Biology and Neurobiology, National Research Council, Fondazione Santa Lucia Rome, Italy
| | - Felice Tirone
- Institute of Cell Biology and Neurobiology, National Research Council, Fondazione Santa Lucia Rome, Italy
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90
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Li C, Yu SSB. Rab proteins as regulators of lipid droplet formation and lipolysis. Cell Biol Int 2016; 40:1026-32. [PMID: 27453349 DOI: 10.1002/cbin.10650] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 07/22/2016] [Indexed: 12/11/2022]
Abstract
Lipid droplets (LDs) are highly dynamic organelles that not only store neutral lipids but also are involved in multiple cellular processes. Dysregulation of lipogenesis or lipolysis greatly contributes to the pathogenesis of several human diseases, including obesity, diabetes, and fatty liver disease. Rab proteins have been found to be associated with LDs in proteomic studies and are also known to extensively regulate intracellular membrane traffic, suggesting that LDs actively communicate with other membrane compartments to maintain energy homeostasis. This review discusses recent studies that provide mechanistic insights into the regulation of LD formation and catabolism by Rab proteins in mammalian cells.
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Affiliation(s)
- Chunman Li
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China
| | - Sidney S B Yu
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China. .,Epithelial Cell Biology Research Centre, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
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91
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Makino A, Hullin-Matsuda F, Murate M, Abe M, Tomishige N, Fukuda M, Yamashita S, Fujimoto T, Vidal H, Lagarde M, Delton I, Kobayashi T. Acute accumulation of free cholesterol induces the degradation of perilipin 2 and Rab18-dependent fusion of ER and lipid droplets in cultured human hepatocytes. Mol Biol Cell 2016; 27:3293-3304. [PMID: 27582390 PMCID: PMC5170862 DOI: 10.1091/mbc.e15-10-0730] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 08/26/2016] [Indexed: 01/19/2023] Open
Abstract
Free cholesterol accumulation in the liver is relevant to the pathogenesis of nonalcoholic steatohepatitis. Acute free cholesterol accumulation induced the fusion of LDs, followed by degradation of the coat protein of LDs, perilipin 2, and association of apolipoprotein 100 to LDs in Rab18-dependent manner. Dysregulated hepatic cholesterol homeostasis with free cholesterol accumulation in the liver is relevant to the pathogenesis of nonalcoholic steatohepatitis, contributing to the chronicity of liver toxicity. Here we examined the effect of free cholesterol accumulation on the morphology and biochemical properties of lipid droplets (LDs) in cultured hepatocytes. Acute free cholesterol accumulation induced the fusion of LDs, followed by degradation of the coat protein of LDs, perilipin 2 (PLIN2; also called adipophilin or adipose differentiation–related protein), and association of apolipoprotein B 100 (ApoB 100) to LDs. The degradation of PLIN2 was inhibited by inhibitors of ubiquitination, autophagy, and protein synthesis. The results indicate that association of ApoB 100 with LDs is dependent on the activity of low–molecular weight GTP-binding protein Rab18 and highlight the role of LDs as targets of free cholesterol toxicity in hepatocytes.
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Affiliation(s)
- Asami Makino
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France.,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France.,Lipid Biology Laboratory, RIKEN, Wako 351-0198, Japan
| | - Françoise Hullin-Matsuda
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France.,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France.,Lipid Biology Laboratory, RIKEN, Wako 351-0198, Japan
| | | | - Mitsuhiro Abe
- Lipid Biology Laboratory, RIKEN, Wako 351-0198, Japan
| | | | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Shizuya Yamashita
- Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Hubert Vidal
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France.,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France
| | - Michel Lagarde
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France.,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France
| | - Isabelle Delton
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France.,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France
| | - Toshihide Kobayashi
- INSERM-RIKEN Lipidomics Unit, Université Lyon 1, 69621 Villeurbanne, France .,INSERM U1060, INSA-Lyon, Université Lyon 1, 69621 Villeurbanne, France.,Lipid Biology Laboratory, RIKEN, Wako 351-0198, Japan.,UMR 7213 CNRS, University of Strasbourg, 67401 Illkirch, France
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92
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Zhang S, Wang Y, Cui L, Deng Y, Xu S, Yu J, Cichello S, Serrero G, Ying Y, Liu P. Morphologically and Functionally Distinct Lipid Droplet Subpopulations. Sci Rep 2016; 6:29539. [PMID: 27386790 PMCID: PMC4937419 DOI: 10.1038/srep29539] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 06/20/2016] [Indexed: 12/12/2022] Open
Abstract
Lipid droplet (LD), a multi-functional organelle, is often found to associate with other cellular membranous structures and vary in size in a given cell, which may be related to their functional diversity. Here we established a method to separate LD subpopulations from isolated CHO K2 LDs into three different size categories. The subpopulation with smallest LDs was nearly free of ER and other membranous structures while those with larger LDs contained intact ER. These distinct subpopulations of LDs differed in their protein composition and ability to recruit proteins. This method was also applicable to LDs obtained from other sources, such as Huh7 cells, mouse liver and brown adipose tissue, et al. We developed an in vitro assay requiring only isolated LDs, Coenzyme A, and ATP to drive lipid synthesis. The LD subpopulation nearly depleted of ER was able to incorporate fatty acids into triacylglycerol and phospholipids. Together, our data demonstrate that LDs in a given cell are heterogeneous in size and function, and suggest that LDs are one of cellular lipid synthetic organelles.
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Affiliation(s)
- Shuyan Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yang Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Liujuan Cui
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yaqin Deng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shimeng Xu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jinhai Yu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Simon Cichello
- School of Life Sciences, La Trobe University, Melbourne Victoria 3086, Australia
| | | | - Yunshu Ying
- University of Texas Southwestern Medical Center, Dallas 75390, USA
| | - Pingsheng Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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93
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Endoplasmic Reticulum: The Favorite Intracellular Niche for Viral Replication and Assembly. Viruses 2016; 8:v8060160. [PMID: 27338443 PMCID: PMC4926180 DOI: 10.3390/v8060160] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 05/23/2016] [Accepted: 05/26/2016] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum (ER) is the largest intracellular organelle. It forms a complex network of continuous sheets and tubules, extending from the nuclear envelope (NE) to the plasma membrane. This network is frequently perturbed by positive-strand RNA viruses utilizing the ER to create membranous replication factories (RFs), where amplification of their genomes occurs. In addition, many enveloped viruses assemble progeny virions in association with ER membranes, and viruses replicating in the nucleus need to overcome the NE barrier, requiring transient changes of the NE morphology. This review first summarizes some key aspects of ER morphology and then focuses on the exploitation of the ER by viruses for the sake of promoting the different steps of their replication cycles.
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94
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The HSP70 co-chaperone DNAJC14 targets misfolded pendrin for unconventional protein secretion. Nat Commun 2016; 7:11386. [PMID: 27109633 PMCID: PMC4848490 DOI: 10.1038/ncomms11386] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 03/18/2016] [Indexed: 12/19/2022] Open
Abstract
Mutations in SLC26A4, which encodes pendrin, are responsible for hearing loss with an enlarged vestibular aqueduct and Pendred syndrome. The most prevalent mutation in East Asia is p.H723R (His723Arg), which leads to defects in protein folding and cell-surface expression. Here we show that H723R-pendrin can be rescued to the cell surface by an HSP70 co-chaperone DNAJC14-dependent unconventional trafficking pathway. Blockade of ER-to-Golgi transport or activation of ER stress signals induced Golgi-independent cell-surface expression of H723R-pendrin and restored its cell-surface Cl−/HCO3− exchange activity. Proteomic and short interfering RNA screenings with subsequent molecular analyses showed that Hsc70 and DNAJC14 are required for the unconventional trafficking of H723R-pendrin. Moreover, DNAJC14 upregulation was able to induce the unconventional cell-surface expression of H723R-pendrin. These results indicate that Hsc70 and DNAJC14 play central roles in ER stress-associated unconventional protein secretion and are potential therapeutic targets for diseases such as Pendred syndrome, which arise from transport defects of misfolded proteins. Mutations in pendrin, a plasma membrane transporter, lead to Pendred syndrome, which is associated with hearing loss. Here, Jung et al. show that cell-surface expression of a mutated form of pendrin can be restored by blocking ER-to-Golgi traffic and triggering a DNAJC14 dependent unconventional secretion pathway.
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95
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Handley MT, Carpanini SM, Mali GR, Sidjanin DJ, Aligianis IA, Jackson IJ, FitzPatrick DR. Warburg Micro syndrome is caused by RAB18 deficiency or dysregulation. Open Biol 2016; 5:150047. [PMID: 26063829 PMCID: PMC4632505 DOI: 10.1098/rsob.150047] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
RAB18, RAB3GAP1, RAB3GAP2 and TBC1D20 are each mutated in Warburg Micro syndrome, a rare autosomal recessive multisystem disorder. RAB3GAP1 and RAB3GAP2 form a binary ‘RAB3GAP’ complex that functions as a guanine-nucleotide exchange factor (GEF) for RAB18, whereas TBC1D20 shows modest RAB18 GTPase-activating (GAP) activity in vitro. Here, we show that in the absence of functional RAB3GAP or TBC1D20, the level, localization and dynamics of cellular RAB18 is altered. In cell lines where TBC1D20 is absent from the endoplasmic reticulum (ER), RAB18 becomes more stably ER-associated and less cytosolic than in control cells. These data suggest that RAB18 is a physiological substrate of TBC1D20 and contribute to a model in which a Rab-GAP can be essential for the activity of a target Rab. Together with previous reports, this indicates that Warburg Micro syndrome can be caused directly by loss of RAB18, or indirectly through loss of RAB18 regulators RAB3GAP or TBC1D20.
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Affiliation(s)
- Mark T Handley
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Sarah M Carpanini
- Division of Neurobiology, The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
| | - Girish R Mali
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Duska J Sidjanin
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Irene A Aligianis
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - Ian J Jackson
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
| | - David R FitzPatrick
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK
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96
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Comparative Proteomic Study of Fatty Acid-treated Myoblasts Reveals Role of Cox-2 in Palmitate-induced Insulin Resistance. Sci Rep 2016; 6:21454. [PMID: 26899878 PMCID: PMC4761885 DOI: 10.1038/srep21454] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 12/18/2015] [Indexed: 12/14/2022] Open
Abstract
Accumulated studies demonstrate that saturated fatty acids (FAs) such as palmitic acid (PA) inhibit insulin signaling in skeletal muscle cells and monounsaturated fatty acids such as oleic acid (OA) reverse the effect of PA on insulin signaling. The detailed molecular mechanism of these opposite effects remains elusive. Here we provide a comparative proteomic study of skeletal myoblast cell line C2C12 that were untreated or treated with PA, and PA plus OA. A total of 3437 proteins were quantified using SILAC in this study and 29 proteins fall into the pattern that OA reverses PA effect. Expression of some these proteins were verified using qRT-PCR and Western blot. The most significant change was cyclooxygenase-2 (Cox-2). In addition to whole cell comparative proteomic study, we also compared lipid droplet (LD)-associated proteins and identified that Cox-2 was one of three major altered proteins under the FA treatment. This finding was then confirmed using immunofluorescence. Finally, Cox-2 selective inhibitor, celecoxib protected cells from PA-reduced insulin signaling Akt phosphorylation. Together, these results not only provide a dataset of protein expression change in FA treatment but also suggest that Cox-2 and lipid droplets (LDs) are potential players in PA- and OA-mediated cellular processes.
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97
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Wu Q, Sun X, Yue W, Lu T, Ruan Y, Chen T, Zhang D. RAB18, a protein associated with Warburg Micro syndrome, controls neuronal migration in the developing cerebral cortex. Mol Brain 2016; 9:19. [PMID: 26879639 PMCID: PMC4754921 DOI: 10.1186/s13041-016-0198-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/08/2016] [Indexed: 01/23/2023] Open
Abstract
Background Loss of function mutations in RAB18, has been identified in patients with the human neurological and developmental disorder Warburg Micro syndrome. However, the function of RAB18 in brain remains unknown. Results In this study, we report that RAB18 is a critical regulator of neuronal migration and morphogenesis. Using in utero electroporation suppression of RAB18 in the mouse brain impairs radial migration. Overexpression of dominant negative RAB18 or disruption of RAB3GAP (RAB18GEF) also results in delayed neuronal migration in the developing mouse cortex and inhibition of neurite growth in vitro. Moreover, loss of RAB18 induces an acceleration of N-cadherin degradation by lysosomal pathway resulting in the decrease of surface level of N-cadherin on neurons. Conclusions RAB18 regulates neuronal migration and morphogenesis during development. Our findings highlight the critical role of RAB3GAP-RAB18 pathway in the developing cerebral cortex and might explain some of clinical features observed in patients with Warburg Micro syndrome. Electronic supplementary material The online version of this article (doi:10.1186/s13041-016-0198-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Qinwei Wu
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China. .,Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China. .,Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China.
| | - Xiaqin Sun
- Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China.
| | - Weihua Yue
- Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China.
| | - Tianlan Lu
- Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China.
| | - Yanyan Ruan
- Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China.
| | - Tianda Chen
- Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China.
| | - Dai Zhang
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China. .,Peking University Sixth Hospital/Institute of Mental Health, Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders/Key Laboratory for Mental Health, Ministry of Health (Peking University), Beijing, 100191, China. .,PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China.
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98
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Small GTPases in peroxisome dynamics. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1006-13. [PMID: 26775587 DOI: 10.1016/j.bbamcr.2016.01.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 12/12/2022]
Abstract
In this review article, we summarize current knowledge on peroxisome biogenesis/functions and the role that small GTPases may play in these processes. Precise intracellular distribution of cell organelles requires their regulated association to microtubules and the actin cytoskeleton. In this respect, RhoGDP/RhoGTP favor binding of peroxisomes to microtubules and actin filaments. In its GTP-bound form, RhoA activates a regulatory cascade involving Rho kinaseII and non-muscle myosinIIA. Such interactions frequently depend on phosphoinositides (PIs) of which PI4P, PI(4,5)P2, and PI(3,5)P2 were found to be present in the peroxisomal membrane. PIs are pivotal determinants of intracellular signaling and known to regulate a wide range of cellular functions. In many of these functions, small GTPases are implicated. The small GTPase ADP-ribosylation factor 1 (Arf1), for example, is known to stimulate synthesis of PI4P and PI(4,5)P2 on the Golgi to regulate protein and lipid sorting. In vitro binding assays localized Arf1 and the COPI complex to peroxisomes. In light of the recent discussion of pre-peroxisomal vesicle generation at the ER, peroxisomal Arf1-COPI vesicles may serve retrograde transport of ER-resident components. A mass spectrometric screen localized various Rab proteins to peroxisomes. Overexpression of these proteins in combination with laser-scanning fluorescence microscopy co-localized Rab6, Rab8, Rab10, Rab14, and Rab18 with peroxisomal structures. By analogy to the role these proteins play in other organelle dynamics, we may envisage what the function of these proteins may be in relation to the peroxisomal compartment.
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99
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Mhlanga-Mutangadura T, Johnson GS, Schnabel RD, Taylor JF, Johnson GC, Katz ML, Shelton GD, Lever TE, Giuliano E, Granger N, Shomper J, O'Brien DP. A mutation in the Warburg syndrome gene, RAB3GAP1, causes a similar syndrome with polyneuropathy and neuronal vacuolation in Black Russian Terrier dogs. Neurobiol Dis 2015; 86:75-85. [PMID: 26607784 DOI: 10.1016/j.nbd.2015.11.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Revised: 11/13/2015] [Accepted: 11/18/2015] [Indexed: 11/30/2022] Open
Abstract
An autosomal recessive disease of Black Russian Terriers was previously described as a juvenile-onset, laryngeal paralysis and polyneuropathy similar to Charcot Marie Tooth disease in humans. We found that in addition to an axonal neuropathy, affected dogs exhibit microphthalmia, cataracts, and miotic pupils. On histopathology, affected dogs exhibit a spongiform encephalopathy characterized by accumulations of abnormal, membrane-bound vacuoles of various sizes in neuronal cell bodies, axons and adrenal cells. DNA from an individual dog with this polyneuropathy with ocular abnormalities and neuronal vacuolation (POANV) was used to generate a whole genome sequence which contained a homozygous RAB3GAP1:c.743delC mutation that was absent from 73 control canine whole genome sequences. An additional 12 Black Russian Terriers with POANV were RAB3GAP1:c.743delC homozygotes. DNA samples from 249 Black Russian Terriers with no known signs of POANV were either heterozygotes or homozygous for the reference allele. Mutations in human RAB3GAP1 cause Warburg micro syndrome (WARBM), a severe developmental disorder characterized by abnormalities of the eye, genitals and nervous system including a predominantly axonal peripheral neuropathy. RAB3GAP1 encodes the catalytic subunit of a GTPase activator protein and guanine exchange factor for Rab3 and Rab18 respectively. Rab proteins are involved in membrane trafficking in the endoplasmic reticulum, axonal transport, autophagy and synaptic transmission. The neuronal vacuolation and membranous inclusions and vacuoles in axons seen in this canine disorder likely reflect alterations of these processes. Thus, this canine disease could serve as a model for WARBM and provide insight into its pathogenesis and treatment.
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Affiliation(s)
| | - Gary S Johnson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, USA
| | - Robert D Schnabel
- Division of Animal Sciences, University of Missouri, Columbia, USA; Informatics Institute, University of Missouri, Columbia, USA
| | - Jeremy F Taylor
- Division of Animal Sciences, University of Missouri, Columbia, USA
| | - Gayle C Johnson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, USA
| | - Martin L Katz
- Mason Eye Institute, University of Missouri, Columbia, USA
| | - G Diane Shelton
- Department of Pathology, University of California, San Diego, La Jolla, USA
| | - Teresa E Lever
- Department of Otolaryngology, University of Missouri, Columbia, USA
| | - Elizabeth Giuliano
- Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, USA
| | - Nicolas Granger
- School of Veterinary Sciences, University of Bristol, Langford House, Langford, Somerset BS40 5DU, UK
| | - Jeremy Shomper
- Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, USA
| | - Dennis P O'Brien
- Department of Veterinary Medicine & Surgery, University of Missouri, Columbia, USA.
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100
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Analysis of biogenesis of lipid droplets by examining Rab40c associating with lipid droplets. Methods Mol Biol 2015; 1270:125-35. [PMID: 25702114 DOI: 10.1007/978-1-4939-2309-0_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The biogenesis of lipid droplets (LDs) is regulated by multiple proteins. Rab40c is a recently characterized small GTPase associating with LDs. Here we describe our approaches to analyze the involvement of Rab40c in the biogenesis of LDs. Co-localization of Rab40c and LDs was revealed through fluorescence confocal microscopy by expressing GFP-Rab40c and labeling LDs with dyes Oil Red O, Nile Red, or BODIPY 493/503. Association of Rab40c with LDs was further confirmed by fractionation with sucrose density centrifugation. The relationship of Rab40c with adipocyte differentiation was examined by detecting the protein level of Rab40c during adipocyte differentiation of 3T3-L1 cells. The roles of Rab40c in the biogenesis of LDs were analyzed by inducing LD formation in HepG2 cells.
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