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Barneda D, Planas-Iglesias J, Gaspar ML, Mohammadyani D, Prasannan S, Dormann D, Han GS, Jesch SA, Carman GM, Kagan V, Parker MG, Ktistakis NT, Klein-Seetharaman J, Dixon AM, Henry SA, Christian M. The brown adipocyte protein CIDEA promotes lipid droplet fusion via a phosphatidic acid-binding amphipathic helix. eLife 2015; 4:e07485. [PMID: 26609809 PMCID: PMC4755750 DOI: 10.7554/elife.07485] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 11/25/2015] [Indexed: 12/22/2022] Open
Abstract
Maintenance of energy homeostasis depends on the highly regulated storage and release of triacylglycerol primarily in adipose tissue, and excessive storage is a feature of common metabolic disorders. CIDEA is a lipid droplet (LD)-protein enriched in brown adipocytes promoting the enlargement of LDs, which are dynamic, ubiquitous organelles specialized for storing neutral lipids. We demonstrate an essential role in this process for an amphipathic helix in CIDEA, which facilitates embedding in the LD phospholipid monolayer and binds phosphatidic acid (PA). LD pairs are docked by CIDEA trans-complexes through contributions of the N-terminal domain and a C-terminal dimerization region. These complexes, enriched at the LD–LD contact site, interact with the cone-shaped phospholipid PA and likely increase phospholipid barrier permeability, promoting LD fusion by transference of lipids. This physiological process is essential in adipocyte differentiation as well as serving to facilitate the tight coupling of lipolysis and lipogenesis in activated brown fat. DOI:http://dx.doi.org/10.7554/eLife.07485.001 If other energy sources become unavailable, cells fall back on stores of fatty molecules called lipids. These are held in membrane-enclosed compartments in the cell called lipid droplets, which in mammals are particularly abundant in fat cells called adipocytes. There are two main types of adipocytes: white adipocytes have a single giant lipid droplet, whereas brown adipocytes contain many smaller droplets. Proteins embedded in the membrane that surrounds a lipid droplet help to control the droplet’s growth and when it releases lipids. For example, a protein called CIDEA, which is only found in brown adipocytes, helps lipid droplets to grow by enabling one droplet to transfer its contents to another droplet. However, little is known about how this occurs. By combining cell biology, biophysical and computer modelling approaches, Barneda et al. investigated how normal and mutant forms of CIDEA affect the growth of lipid droplets. These experiments identified a helix in the structure of CIDEA that embeds it in the membrane, from where it can then interact with CIDEA proteins on other lipid droplets to hold the droplets together. In addition, the helix interacts with a molecule in the lipid droplet membrane called phosphatidic acid. Barneda et al. suggest that this interaction helps to transfer the contents of one droplet to another by making it easier for lipids to move through the droplets’ membranes. The next challenge is to characterize the mechanisms that control CIDEA activity to influence the formation of the multiple lipid droplets that distinguish brown and BRITE (brown-in-white) adipocytes from white adipocytes. The lipid droplets in brown adipocytes are an important target for research to combat obesity, due to the 'burning' rather than storing of lipids that occurs in these cells. DOI:http://dx.doi.org/10.7554/eLife.07485.002
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Affiliation(s)
- David Barneda
- Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | | | - Maria L Gaspar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Dariush Mohammadyani
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, United States
| | - Sunil Prasannan
- Department of Chemistry, University of Warwick, Coventry, United Kingdom
| | - Dirk Dormann
- Microscopy Facility, MRC Clinical Sciences Centre, Imperial College London, London, United Kingdom
| | - Gil-Soo Han
- Department of Food Science, Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Stephen A Jesch
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - George M Carman
- Department of Food Science, Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Valerian Kagan
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, United States
| | - Malcolm G Parker
- Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom
| | | | - Judith Klein-Seetharaman
- Warwick Medical School, University of Warwick, Coventry, United Kingdom.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, United States
| | - Ann M Dixon
- Department of Chemistry, University of Warwick, Coventry, United Kingdom
| | - Susan A Henry
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Mark Christian
- Institute of Reproductive and Developmental Biology, Imperial College London, London, United Kingdom.,Warwick Medical School, University of Warwick, Coventry, United Kingdom
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Konige M, Wang H, Sztalryd C. Role of adipose specific lipid droplet proteins in maintaining whole body energy homeostasis. Biochim Biophys Acta Mol Basis Dis 2013; 1842:393-401. [PMID: 23688782 DOI: 10.1016/j.bbadis.2013.05.007] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 04/10/2013] [Accepted: 05/03/2013] [Indexed: 12/15/2022]
Abstract
Excess or insufficient lipid storage in white adipose tissue lipid droplets is associated with dyslipidemia, insulin resistance and increased risk for diabetes type 2. Thus, maintenance of adipose lipid droplet growth and function is critical to preserve whole body insulin sensitivity and energy homeostasis. Progress in understanding biology of lipid droplets has underscored the role of proteins that interact with lipid droplets. Here, we review the current knowledge of adipose specific lipid droplet proteins, which share unique functions controlling adipocyte lipid storage, limiting lipid spill-over and lipotoxic effects thought to contribute to disease. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.
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Affiliation(s)
- Manige Konige
- Department of Medicine, Division of Endocrinology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Hong Wang
- Department of Medicine, Division of Endocrinology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Carole Sztalryd
- Department of Medicine, Division of Endocrinology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; Geriatric Research, Education, and Clinical Center, Baltimore Veterans Affairs Health Care Center, Baltimore, MD 21201, USA.
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