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Wang H, Nikain C, Amengual J, La Forest M, Yu Y, Wang MC, Watts R, Lehner R, Qiu Y, Cai M, Kurland IJ, Goldberg IJ, Rajan S, Hussain MM, Brodsky JL, Fisher EA. FITM2 deficiency results in ER lipid accumulation, ER stress, reduced apolipoprotein B lipidation, and VLDL triglyceride secretion in vitro and in mouse liver. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.05.570183. [PMID: 38106013 PMCID: PMC10723279 DOI: 10.1101/2023.12.05.570183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Objectives Triglyceride (TG) association with apolipoprotein B100 (apoB100) serves to form very low density lipoproteins (VLDL) in the liver. The repertoire of factors that facilitate this association is incompletely defined. FITM2, an integral endoplasmic reticulum (ER) protein, was originally discovered as a factor participating in cytoplasmic lipid droplets (LDs) in tissues that do not form VLDL. We hypothesized that in the liver, in addition to promoting cytosolic LD formation, FITM2 would also transfer TG from its site of synthesis in the ER membrane to nascent VLDL particles within the ER lumen. Methods Experiments were conducted using a rat hepatic cell line (McArdle-RH7777, or McA cells), an established model of mammalian lipoprotein metabolism, and mice. FITM2 expression was reduced using siRNA in cells and by liver specific cre-recombinase mediated deletion of the Fitm2 gene in mice. Effects of FITM2 deficiency on VLDL assembly and secretion in vitro and in vivo were measured by multiple methods, including density gradient ultracentrifugation, chromatography, mass spectrometry, simulated Raman spectroscopy (SRS) microscopy, sub-cellular fractionation, immunoprecipitation, immunofluorescence, and electron microscopy. Main findings 1) FITM2-deficient hepatic cells in vitro and in vivo secrete TG-depleted VLDL particles, but the number of particles is unchanged compared to controls; 2) FITM2 deficiency in mice on a high fat diet (HFD) results in decreased plasma TG levels. The number of apoB100-containing lipoproteins remains similar, but shift from VLDL to LDL density; 3) Both in vitro and in vivo , when TG synthesis is stimulated and FITM2 is deficient, TG accumulates in the ER, and despite its availability this pool is unable to fully lipidate apoB100 particles; 4) FITM2 deficiency disrupts ER morphology and results in ER stress. Principal conclusions The results suggest that FITM2 contributes to VLDL lipidation, especially when newly synthesized hepatic TG is in abundance. In addition to its fundamental importance in VLDL assembly, the results also suggest that under dysmetabolic conditions, FITM2 may be a limiting factor that ultimately contributes to non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH).
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Wang G, Chen A, Wu Y, Wang D, Chang C, Yu G. Fat storage-inducing transmembrane proteins: beyond mediating lipid droplet formation. Cell Mol Biol Lett 2022; 27:98. [DOI: 10.1186/s11658-022-00391-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/23/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractFat storage-inducing transmembrane proteins (FITMs) were initially identified in 2007 as members of a conserved endoplasmic reticulum (ER) resident transmembrane protein gene family, and were found to be involved in lipid droplet (LD) formation. Recently, several studies have further demonstrated that the ability of FITMs to directly bind to triglyceride and diacylglycerol, and the diphosphatase activity of hydrolyzing fatty acyl-CoA, might enable FITMs to maintain the formation of lipid droplets, engage in lipid metabolism, and protect against cellular stress. Based on the distribution of FITMs in tissues and their important roles in lipid droplet biology and lipid metabolism, it was discovered that FITMs were closely related to muscle development, adipocyte differentiation, and energy metabolism. Accordingly, the abnormal expression of FITMs was not only associated with type 2 diabetes and lipodystrophy, but also with cardiac disease and several types of cancer. This study reviews the structure, distribution, expression regulation, and functionality of FITMs and their potential relationships with various metabolic diseases, hoping to provide inspiration for fruitful research directions and applications of FITM proteins. Moreover, this review will provide an important theoretical basis for the application of FITMs in the diagnosis and treatment of related diseases.
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Antunes P, Cruz A, Barbosa J, Bonifácio VDB, Pinto SN. Lipid Droplets in Cancer: From Composition and Role to Imaging and Therapeutics. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27030991. [PMID: 35164256 PMCID: PMC8840564 DOI: 10.3390/molecules27030991] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/26/2022] [Accepted: 01/31/2022] [Indexed: 12/11/2022]
Abstract
Cancer is the second most common cause of death worldwide, having its origin in the abnormal growth of cells. Available chemotherapeutics still present major drawbacks, usually associated with high toxicity and poor distribution, with only a small fraction of drugs reaching the tumour sites. Thus, it is urgent to develop novel therapeutic strategies. Cancer cells can reprogram their lipid metabolism to sustain uncontrolled proliferation, and, therefore, accumulate a higher amount of lipid droplets (LDs). LDs are cytoplasmic organelles that store neutral lipids and are hypothesized to sequester anti-cancer drugs, leading to reduced efficacy. Thus, the increased biogenesis of LDs in neoplastic conditions makes them suitable targets for anticancer therapy and for the development of new dyes for cancer cells imaging. In recent years, cancer nanotherapeutics offered some exciting possibilities, including improvement tumour detection and eradication. In this review we summarize LDs biogenesis, structure and composition, and highlight their role in cancer theranostics.
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Affiliation(s)
- Patrícia Antunes
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (P.A.); (A.C.); (J.B.)
- Associate Laboratory i4HB-Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Adriana Cruz
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (P.A.); (A.C.); (J.B.)
- Associate Laboratory i4HB-Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - José Barbosa
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (P.A.); (A.C.); (J.B.)
- Associate Laboratory i4HB-Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Vasco D. B. Bonifácio
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (P.A.); (A.C.); (J.B.)
- Associate Laboratory i4HB-Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Bioengineering Department, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Correspondence: (V.D.B.B.); (S.N.P.)
| | - Sandra N. Pinto
- iBB-Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; (P.A.); (A.C.); (J.B.)
- Associate Laboratory i4HB-Institute for Health and Bioeconomy, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
- Correspondence: (V.D.B.B.); (S.N.P.)
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Zhang J, Hu Y, Wang Y, Fu L, Xu X, Li C, Xu J, Li C, Zhang L, Yang R, Jiang X, Wu Y, Liu P, Zou X, Liang B. mmBCFA C17iso ensures endoplasmic reticulum integrity for lipid droplet growth. J Cell Biol 2021; 220:212690. [PMID: 34623380 PMCID: PMC8563294 DOI: 10.1083/jcb.202102122] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 08/22/2021] [Accepted: 09/21/2021] [Indexed: 12/29/2022] Open
Abstract
In eukaryote cells, lipid droplets (LDs) are key intracellular organelles that dynamically regulate cellular energy homeostasis. LDs originate from the ER and continuously contact the ER during their growth. How the ER affects LD growth is largely unknown. Here, we show that RNAi knockdown of acs-1, encoding an acyl-CoA synthetase required for the biosynthesis of monomethyl branched-chain fatty acids C15iso and C17iso, remarkably prevented LD growth in Caenorhabditis elegans. Dietary C17iso, or complex lipids with C17iso including phosphatidylcholine, phosphatidylethanolamine, and triacylglycerol, could fully restore the LD growth in the acs-1RNAi worms. Mechanistically, C17iso may incorporate into phospholipids to ensure the membrane integrity of the ER so as to maintain the function of ER-resident enzymes such as SCD/stearoyl-CoA desaturase and DGAT2/diacylglycerol acyltransferase for appropriate lipid synthesis and LD growth. Collectively, our work uncovers a unique fatty acid, C17iso, as the side chain of phospholipids for determining the ER homeostasis for LD growth in an intact organism, C. elegans.
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Affiliation(s)
- Jingjing Zhang
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Ying Hu
- School of Traditional Chinese Medicine, Yunnan University of Chinese Medicine, Kunming, Yunnan, China
| | - Yanli Wang
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Lin Fu
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Xiumei Xu
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China.,Institute of Physical Science and Information Technology, Anhui University, Hefei, Anhui, China
| | - Chunxia Li
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China.,Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Jie Xu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China.,Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Chengbin Li
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Linqiang Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Rendan Yang
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
| | - Xue Jiang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Yingjie Wu
- Shandong Provincial Hospital, Shandong Laboratory Animal Center, Shandong First Medical University and Shandong Academy of Medical Sciences. Jinan, Shandong, China
| | - Pingsheng Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Xiaoju Zou
- School of Traditional Chinese Medicine, Yunnan University of Chinese Medicine, Kunming, Yunnan, China
| | - Bin Liang
- Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, Yunnan, China
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Choudhary V, Schneiter R. A Unique Junctional Interface at Contact Sites Between the Endoplasmic Reticulum and Lipid Droplets. Front Cell Dev Biol 2021; 9:650186. [PMID: 33898445 PMCID: PMC8060488 DOI: 10.3389/fcell.2021.650186] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 03/09/2021] [Indexed: 12/19/2022] Open
Abstract
Lipid droplets (LDs) constitute compartments dedicated to the storage of metabolic energy in the form of neutral lipids. LDs originate from the endoplasmic reticulum (ER) with which they maintain close contact throughout their life cycle. These ER-LD junctions facilitate the exchange of both proteins and lipids between these two compartments. In recent years, proteins that are important for the proper formation of LDs and localize to ER-LD junctions have been identified. This junction is unique as it is generally believed to invoke a transition from the ER bilayer membrane to a lipid monolayer that delineates LDs. Proper formation of this junction requires the ordered assembly of proteins and lipids at specialized ER subdomains. Without such a well-ordered assembly of LD biogenesis factors, neutral lipids are synthesized throughout the ER membrane, resulting in the formation of aberrant LDs. Such ectopically formed LDs impact ER and lipid homeostasis, resulting in different types of lipid storage diseases. In response to starvation, the ER-LD junction recruits factors that tether the vacuole to these junctions to facilitate LD degradation. In addition, LDs maintain close contacts with peroxisomes and mitochondria for metabolic channeling of the released fatty acids toward beta-oxidation. In this review, we discuss the function of different components that ensure proper functioning of LD contact sites, their role in lipogenesis and lipolysis, and their relation to lipid storage diseases.
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Affiliation(s)
- Vineet Choudhary
- Department of Biotechnology, All India Institute of Medical Sciences (AIIMS), New Delhi, India
| | - Roger Schneiter
- Department of Biology, University of Fribourg, Fribourg, Switzerland
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The Puzzling Conservation and Diversification of Lipid Droplets from Bacteria to Eukaryotes. Results Probl Cell Differ 2020; 69:281-334. [PMID: 33263877 DOI: 10.1007/978-3-030-51849-3_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Membrane compartments are amongst the most fascinating markers of cell evolution from prokaryotes to eukaryotes, some being conserved and the others having emerged via a series of primary and secondary endosymbiosis events. Membrane compartments comprise the system limiting cells (one or two membranes in bacteria, a unique plasma membrane in eukaryotes) and a variety of internal vesicular, subspherical, tubular, or reticulated organelles. In eukaryotes, the internal membranes comprise on the one hand the general endomembrane system, a dynamic network including organelles like the endoplasmic reticulum, the Golgi apparatus, the nuclear envelope, etc. and also the plasma membrane, which are linked via direct lateral connectivity (e.g. between the endoplasmic reticulum and the nuclear outer envelope membrane) or indirectly via vesicular trafficking. On the other hand, semi-autonomous organelles, i.e. mitochondria and chloroplasts, are disconnected from the endomembrane system and request vertical transmission following cell division. Membranes are organized as lipid bilayers in which proteins are embedded. The budding of some of these membranes, leading to the formation of the so-called lipid droplets (LDs) loaded with hydrophobic molecules, most notably triacylglycerol, is conserved in all clades. The evolution of eukaryotes is marked by the acquisition of mitochondria and simple plastids from Gram-positive bacteria by primary endosymbiosis events and the emergence of extremely complex plastids, collectively called secondary plastids, bounded by three to four membranes, following multiple and independent secondary endosymbiosis events. There is currently no consensus view of the evolution of LDs in the Tree of Life. Some features are conserved; others show a striking level of diversification. Here, we summarize the current knowledge on the architecture, dynamics, and multitude of functions of the lipid droplets in prokaryotes and in eukaryotes deriving from primary and secondary endosymbiosis events.
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Monson EA, Crosse KM, Das M, Helbig KJ. Lipid droplet density alters the early innate immune response to viral infection. PLoS One 2018; 13:e0190597. [PMID: 29293661 PMCID: PMC5749834 DOI: 10.1371/journal.pone.0190597] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 12/17/2017] [Indexed: 12/30/2022] Open
Abstract
The cellular localisation of many innate signalling events following viral infection has yet to be elucidated, however there has been a few cases in which membranes of certain cellular organelles have acted as platforms to these events. Of these, lipid droplets (LDs) have recently been identified as signalling platforms for innate TLR7 and 9 signalling. Despite their wide range of similar roles in various metabolic pathways, LDs have been overlooked as potential platforms for antiviral innate signalling events. This study established an in vitro model to evaluate the efficiency of the early innate immune response in cells with reduced LD content to the viral mimics, dsDNA and dsRNA, and Sendai viral infection. Using RT-qPCR, the expression of IFN-β and IFN-λ was quantified following stimulation along with the expression of specific ISGs. Luciferase based assays evaluated the combined expression of ISRE-promoter driven ISGs under IFN-β stimulation. Cellular LD content did not alter the entry of fluorescently labelled viral mimics into cells, but significantly decreased the ability of both Huh-7 and HeLa cells to produce type I and III IFN, as well as downstream ISG expression, indicative of an impeded innate immune response. This observation was also seen during Sendai virus infection of HeLa cells, where both control and LD reduced cells replicated the virus to the same level, but a significantly impaired type I and III IFN response was observed in the LD reduced cells. In addition to altered IFN production, cells with reduced LD content exhibited decreased expression of specific antiviral ISGs: Viperin, IFIT-1 and OAS-1 under IFN-β stimulation; However the overall induction of the ISRE-promoter was not effected. This study implicates a role for LDs in an efficient early innate host response to viral infection and future work will endeavour to determine the precise role these important organelles play in induction of an antiviral response.
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Affiliation(s)
- Ebony A Monson
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria
| | - Keaton M Crosse
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria
| | - Mithun Das
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria
| | - Karla J Helbig
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria
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