51
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Lamari F, Mochel F, Sedel F, Saudubray JM. Disorders of phospholipids, sphingolipids and fatty acids biosynthesis: toward a new category of inherited metabolic diseases. J Inherit Metab Dis 2013; 36:411-25. [PMID: 22814679 DOI: 10.1007/s10545-012-9509-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 05/29/2012] [Accepted: 06/12/2012] [Indexed: 12/29/2022]
Abstract
We wish to delineate a novel, and rapidly expanding, group of inborn errors of metabolism with neurological/muscular presentations: the defects in phospholipids, sphingolipids and long chain fatty acids biosynthesis. At least 14 disorders have been described so far. Clinical presentations are diverse but can be divided into (1) diseases of the central nervous system; (2) peripheral neuropathies; and (3) muscular/cardiac presentations. (1) Leukodystrophy and/or iron deposits in basal ganglia is a common feature of phospholipase A2 deficiency, fatty acid hydroxylase deficiency, and pantothenate kinase-associated neurodegeneration. Infantile epilepsy has been reported in GM3 synthetase deficiency. Spastic quadriplegia with ichthyosis and intellectual disability are the presenting signs of the elongase 4 deficiency and the Sjogren-Larsson syndrome caused by fatty aldehyde dehydrogenase deficiency. Spastic paraplegia and muscle wasting are also seen in patients with mutations in the neuropathy target esterase gene. (2) Peripheral neuropathy is a prominent feature in PHARC syndrome due to α/β-hydrolase 12 deficiency, and in hereditary sensory autonomic neuropathy type I due to serine palmitoyl-CoA transferase deficiency. (3) Muscular/cardiac presentations include recurrent myoglobinuria in phosphatidate phosphatase 1 (Lipin1) deficiency; cardiomyopathy and multivisceral involvement in Barth syndrome secondary to tafazzin mutations; congenital muscular dystrophy due to choline kinase deficiency, Sengers syndrome due to acylglycerol kinase deficiency and Chanarin Dorfman syndrome due to α/β- hydrolase 5 deficiency. These synthesis defects of complex lipid molecules stand at the frontier between classical inborn errors of metabolism and other genetic diseases involving the metabolism of structural proteins.
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Affiliation(s)
- F Lamari
- Neurometabolic Unit, Pitié-Salpêtrière Hospital, AP-HP & University Pierre and Marie Curie, Paris, France
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52
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Park S, Gidda SK, James CN, Horn PJ, Khuu N, Seay DC, Keereetaweep J, Chapman KD, Mullen RT, Dyer JM. The α/β hydrolase CGI-58 and peroxisomal transport protein PXA1 coregulate lipid homeostasis and signaling in Arabidopsis. THE PLANT CELL 2013; 25:1726-39. [PMID: 23667126 PMCID: PMC3694702 DOI: 10.1105/tpc.113.111898] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 04/17/2013] [Accepted: 04/23/2013] [Indexed: 05/21/2023]
Abstract
COMPARATIVE GENE IDENTIFICATION-58 (CGI-58) is a key regulator of lipid metabolism and signaling in mammals, but its underlying mechanisms are unclear. Disruption of CGI-58 in either mammals or plants results in a significant increase in triacylglycerol (TAG), suggesting that CGI-58 activity is evolutionarily conserved. However, plants lack proteins that are important for CGI-58 activity in mammals. Here, we demonstrate that CGI-58 functions by interacting with the PEROXISOMAL ABC-TRANSPORTER1 (PXA1), a protein that transports a variety of substrates into peroxisomes for their subsequent metabolism by β-oxidation, including fatty acids and lipophilic hormone precursors of the jasmonate and auxin biosynthetic pathways. We also show that mutant cgi-58 plants display changes in jasmonate biosynthesis, auxin signaling, and lipid metabolism consistent with reduced PXA1 activity in planta and that, based on the double mutant cgi-58 pxa1, PXA1 is epistatic to CGI-58 in all of these processes. However, CGI-58 was not required for the PXA1-dependent breakdown of TAG in germinated seeds. Collectively, the results reveal that CGI-58 positively regulates many aspects of PXA1 activity in plants and that these two proteins function to coregulate lipid metabolism and signaling, particularly in nonseed vegetative tissues. Similarities and differences of CGI-58 activity in plants versus animals are discussed.
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Affiliation(s)
- Sunjung Park
- U.S. Department of Agriculture–Agricultural Research Service, U.S. Arid-Land Agricultural Research Center, Maricopa, Arizona 85138
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, Texas 76203
| | - Satinder K. Gidda
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Christopher N. James
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, Texas 76203
| | - Patrick J. Horn
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, Texas 76203
| | - Nicholas Khuu
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - Damien C. Seay
- U.S. Department of Agriculture–Agricultural Research Service, U.S. Arid-Land Agricultural Research Center, Maricopa, Arizona 85138
| | - Jantana Keereetaweep
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, Texas 76203
| | - Kent D. Chapman
- Department of Biological Sciences, Center for Plant Lipid Research, University of North Texas, Denton, Texas 76203
| | - Robert T. Mullen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
| | - John M. Dyer
- U.S. Department of Agriculture–Agricultural Research Service, U.S. Arid-Land Agricultural Research Center, Maricopa, Arizona 85138
- Address correspondence to
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53
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Zierler KA, Jaeger D, Pollak NM, Eder S, Rechberger GN, Radner FPW, Woelkart G, Kolb D, Schmidt A, Kumari M, Preiss-Landl K, Pieske B, Mayer B, Zimmermann R, Lass A, Zechner R, Haemmerle G. Functional cardiac lipolysis in mice critically depends on comparative gene identification-58. J Biol Chem 2013; 288:9892-9904. [PMID: 23413028 DOI: 10.1074/jbc.m112.420620] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Efficient catabolism of cellular triacylglycerol (TG) stores requires the TG hydrolytic activity of adipose triglyceride lipase (ATGL). The presence of comparative gene identification-58 (CGI-58) strongly increased ATGL-mediated TG catabolism in cell culture experiments. Mutations in the genes coding for ATGL or CGI-58 in humans cause neutral lipid storage disease characterized by TG accumulation in multiple tissues. ATGL gene mutations cause a severe phenotype especially in cardiac muscle leading to cardiomyopathy that can be lethal. In contrast, CGI-58 gene mutations provoke severe ichthyosis and hepatosteatosis in humans and mice, whereas the role of CGI-58 in muscle energy metabolism is less understood. Here we show that mice lacking CGI-58 exclusively in muscle (CGI-58KOM) developed severe cardiac steatosis and cardiomyopathy linked to impaired TG catabolism and mitochondrial fatty acid oxidation. The marked increase in ATGL protein levels in cardiac muscle of CGI-58KOM mice was unable to compensate the lack of CGI-58. The addition of recombinant CGI-58 to cardiac lysates of CGI-58KOM mice completely reconstituted TG hydrolytic activities. In skeletal muscle, the lack of CGI-58 similarly provoked TG accumulation. The addition of recombinant CGI-58 increased TG hydrolytic activities in control and CGI-58KOM tissue lysates, elucidating the limiting role of CGI-58 in skeletal muscle TG catabolism. Finally, muscle CGI-58 deficiency affected whole body energy homeostasis, which is caused by impaired muscle TG catabolism and increased cardiac glucose uptake. In summary, this study demonstrates that functional muscle lipolysis depends on both CGI-58 and ATGL.
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Affiliation(s)
- Kathrin A Zierler
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Doris Jaeger
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Nina M Pollak
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Sandra Eder
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | | | - Franz P W Radner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Gerald Woelkart
- Department of Pharmacology and Toxicology, University of Graz, 8010 Graz, Austria
| | - Dagmar Kolb
- Center for Medical Research, Department of Internal Medicine, Medical University of Graz, 8036 Graz, Austria
| | - Albrecht Schmidt
- Department of Cardiology, Department of Internal Medicine, Medical University of Graz, 8036 Graz, Austria
| | - Manju Kumari
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | | | - Burkert Pieske
- Department of Cardiology, Department of Internal Medicine, Medical University of Graz, 8036 Graz, Austria
| | - Bernd Mayer
- Department of Pharmacology and Toxicology, University of Graz, 8010 Graz, Austria
| | - Robert Zimmermann
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria.
| | - Guenter Haemmerle
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
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54
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Barneda D, Frontini A, Cinti S, Christian M. Dynamic changes in lipid droplet-associated proteins in the "browning" of white adipose tissues. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:924-33. [PMID: 23376222 DOI: 10.1016/j.bbalip.2013.01.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 12/18/2012] [Accepted: 01/23/2013] [Indexed: 12/30/2022]
Abstract
The morphological and functional differences between lipid droplets (LDs) in brown (BAT) and white (WAT) adipose tissues will largely be determined by their associated proteins. Analysing mRNA expression in mice fat depots we have found that most LD protein genes are expressed at higher levels in BAT, with the greatest differences observed for Cidea and Plin5. Prolonged cold exposure, which induces the appearance of brown-like adipocytes in mice WAT depots, was accompanied with the potentiation of the lipolytic machinery, with changes in ATGL, CGI-58 and G0S2 gene expression. However the major change detected in WAT was the enhancement of Cidea mRNA. Together with the increase in Cidec, it indicates that LD enlargement through LD-LD transference of fat is an important process during WAT browning. To study the dynamics of this phenotypic change, we have applied 4D confocal microscopy in differentiated 3T3-L1 cells under sustained β-adrenergic stimulation. Under these conditions the cells experienced a LD remodelling cycle, with progressive reduction on the LD size by lipolysis, followed by the formation of new LDs, which were subjected to an enlargement process, likely to be CIDE-triggered, until the cell returned to the basal state. This transformation would be triggered by the activation of a thermogenic futile cycle of lipolysis/lipogenesis and could facilitate the molecular mechanism for the unilocular to multilocular transformation during WAT browning. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.
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Affiliation(s)
- David Barneda
- Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, Du Cane Road, London W12 ONN, UK
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55
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Lord CC, Thomas G, Brown JM. Mammalian alpha beta hydrolase domain (ABHD) proteins: Lipid metabolizing enzymes at the interface of cell signaling and energy metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:792-802. [PMID: 23328280 DOI: 10.1016/j.bbalip.2013.01.002] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 12/07/2012] [Accepted: 01/02/2013] [Indexed: 11/16/2022]
Abstract
Dysregulation of lipid metabolism underlies many chronic diseases such as obesity, diabetes, cardiovascular disease, and cancer. Therefore, understanding enzymatic mechanisms controlling lipid synthesis and degradation is imperative for successful drug discovery for these human diseases. Genes encoding α/β hydrolase fold domain (ABHD) proteins are present in virtually all reported genomes, and conserved structural motifs shared by these proteins predict common roles in lipid synthesis and degradation. However, the physiological substrates and products for these lipid metabolizing enzymes and their broader role in metabolic pathways remain largely uncharacterized. Recently, mutations in several members of the ABHD protein family have been implicated in inherited inborn errors of lipid metabolism. Furthermore, studies in cell and animal models have revealed important roles for ABHD proteins in lipid metabolism, lipid signal transduction, and metabolic disease. The purpose of this review is to provide a comprehensive summary surrounding the current state of knowledge regarding mammalian ABHD protein family members. In particular, we will discuss how ABHD proteins are ideally suited to act at the interface of lipid metabolism and signal transduction. Although, the current state of knowledge regarding mammalian ABHD proteins is still in its infancy, this review highlights the potential for the ABHD enzymes as being attractive targets for novel therapies targeting metabolic disease.
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Affiliation(s)
- Caleb C Lord
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Gwynneth Thomas
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - J Mark Brown
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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56
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Li X, Suh Y, Kim E, Moeller SJ, Lee K. Alternative splicing and developmental and hormonal regulation of porcine comparative gene identification-58 (CGI-58) mRNA1. J Anim Sci 2012; 90:4346-54. [DOI: 10.2527/jas.2012-5151] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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57
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Hashimoto T, Segawa H, Okuno M, Kano H, Hamaguchi HO, Haraguchi T, Hiraoka Y, Hasui S, Yamaguchi T, Hirose F, Osumi T. Active involvement of micro-lipid droplets and lipid-droplet-associated proteins in hormone-stimulated lipolysis in adipocytes. J Cell Sci 2012; 125:6127-36. [PMID: 23108672 DOI: 10.1242/jcs.113084] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The regulation of lipolysis in adipocytes involves coordinated actions of many lipid droplet (LD)-associated proteins such as perilipin, hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL), and its activator protein, CGI-58. Here, we describe the cellular origin and physiological significance of micro LDs (mLDs) that emerge in the cytoplasm during active lipolysis, as well as the roles of key lipolytic proteins on mLDs in differentiated 3T3-L1 adipocytes. Multiplex coherent anti-Stokes Raman scattering (CARS) microscopy demonstrated that mLDs receive the fatty acid (FA) moiety of triglyceride from pre-existing LDs during lipolysis. However, when FA re-esterification was blocked, mLDs did not emerge. Time-lapse imaging of GFP-tagged LD-associated proteins and immunocytochemical analyses showed that particulate structures carrying LD-associated proteins emerged throughout the cells upon lipolytic stimulation, but not when FA re-esterification was blocked. Overall lipolysis, as estimated by glycerol release, was significantly lowered by blocking re-esterification, whereas release of free FAs was enhanced. ATGL was co-immunoprecipitated with CGI-58 from the homogenates of lipolytically stimulated cells. Following CGI-58 knockdown or ATGL inhibition with bromoenol lactone, release of both glycerol and FA was significantly lowered. AICAR, an activator of AMP-activated protein kinase, significantly increased FA release, in accordance with increased expression of ATGL, even in the absence of CGI-58. These results suggest that, besides on the surface of pre-existing central LDs, LD-associated proteins are actively involved in lipolysis on mLDs that are formed by FA re-esterification. Regulation of mLDs and LD-associated proteins may be an attractive therapeutic target against lipid-associated metabolic diseases.
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Affiliation(s)
- Takeshi Hashimoto
- Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.
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58
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Rani SH, Saha S, Rajasekharan R. A soluble diacylglycerol acyltransferase is involved in triacylglycerol biosynthesis in the oleaginous yeast Rhodotorula glutinis. MICROBIOLOGY-SGM 2012; 159:155-166. [PMID: 23103975 DOI: 10.1099/mic.0.063156-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The biosynthesis of triacylglycerol (TAG) occurs in the microsomal membranes of eukaryotes. Here, we report the identification and functional characterization of diacylglycerol acyltransferase (DGAT), a member of the 10 S cytosolic TAG biosynthetic complex (TBC) in Rhodotorula glutinis. Both a full-length and an N-terminally truncated cDNA clone of a single gene were isolated from R. glutinis. The DGAT activity of the protein encoded by RgDGAT was confirmed in vivo by the heterologous expression of cDNA in a Saccharomyces cerevisiae quadruple mutant (H1246) that is defective in TAG synthesis. RgDGAT overexpression in yeast was found to be capable of acylating diacylglycerol (DAG) in an acyl-CoA-dependent manner. Quadruple mutant yeast cells exhibit growth defects in the presence of oleic acid, but wild-type yeast cells do not. In an in vivo fatty acid supplementation experiment, RgDGAT expression rescued quadruple mutant growth in an oleate-containing medium. We describe a soluble acyl-CoA-dependent DAG acyltransferase from R. glutinis that belongs to the DGAT3 class of enzymes. The study highlights the importance of an alternative TAG biosynthetic pathway in oleaginous yeasts.
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Affiliation(s)
- Sapa Hima Rani
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Saikat Saha
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Ram Rajasekharan
- Central Food Technological Research Institute, Council of Scientific and Industrial Research, Mysore 570 020, India.,Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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59
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Tavian D, Missaglia S, Redaelli C, Pennisi EM, Invernici G, Wessalowski R, Maiwald R, Arca M, Coleman RA. Contribution of novel ATGL missense mutations to the clinical phenotype of NLSD-M: a strikingly low amount of lipase activity may preserve cardiac function. Hum Mol Genet 2012; 21:5318-28. [PMID: 22990388 DOI: 10.1093/hmg/dds388] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The lack of adipose triglyceride lipase (ATGL), a patatin-like phospholipase domain-containing enzyme that hydrolyzes fatty acids from triacylglycerol (TAG) stored in multiple tissues, causes the autosomal recessive disorder neutral lipid storage disease with myopathy (NLSD-M). In two families of Lebanese and Italian origin presenting with NLSD-M, we identified two new missense mutations in highly conserved regions of ATGL (p.Arg221Pro and p.Asn172Lys) and a novel nonsense mutation (p.Trp8X). The Lebanese patients harbor homozygous p.Arg221Pro, whereas the Italian patients are heterozygotes for p.Asn172Lys and the p.Trp8X mutation. The p.Trp8X mutation results in a complete absence of ATGL protein, while the p.Arg221Pro and p.Asn172Lys mutations result in proteins with minimal lipolytic activity. Although these mutations did not affect putative catalytic residues or the lipid droplet (LD)-binding domain of ATGL, cytosolic LDs accumulated in cultured skin fibroblasts from the patients. The missense mutations might destabilize a random coil (p.Asn172Lys) or a helix (p.Arg221Pro) structure within or proximal to the patatin domain of the lipase, thereby interfering with the enzyme activity, while leaving intact the residues required to localize the protein to LDs. Overexpressing wild-type ATGL in one patient's fibroblasts corrected the metabolic defect and effectively reduced the number and area of cellular LDs. Despite the poor lipase activity in vitro, the Lebanese siblings have a mild myopathy and not clinically evident myocardial dysfunction. The patients of Italian origin show a late-onset and slowly progressive skeletal myopathy. These findings suggest that a small amount of correctly localized lipase activity preserves cardiac function in NLSD-M.
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Affiliation(s)
- Daniela Tavian
- Laboratory of Human Molecular Biology and Genetics, Catholic University of the Sacred Heart, Milan, Italy.
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60
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Schittmayer M, Birner-Gruenberger R. Lipolytic proteomics. MASS SPECTROMETRY REVIEWS 2012; 31:570-582. [PMID: 22392637 DOI: 10.1002/mas.20355] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 11/10/2011] [Accepted: 11/10/2011] [Indexed: 05/31/2023]
Abstract
Activity-based proteomics (ABP) employs small molecular probes to specifically label sets of enzymes based on their shared catalytic mechanism. Given that the vast majority of lipases belong to the family of serine hydrolases and share a nucleophilic active-site serine as part of a catalytic triad, activity-based probes are ideal tools to study lipases and lipolysis. Moreover, the ability of ABP to highlight or isolate specific subproteomes results in a massive decrease of sample complexity. Thereby, in-depth analysis of enzymes of interest with mass spectrometry becomes feasible. In this review, we cover probe design, technological developments, and applications of ABP of lipases, as well as give an overview of relevant identified proteins.
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Affiliation(s)
- Matthias Schittmayer
- Research Group Functional Proteomics, Institute of Pathology, Medical University of Graz, Graz, Austria
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61
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Schweiger M, Paar M, Eder C, Brandis J, Moser E, Gorkiewicz G, Grond S, Radner FPW, Cerk I, Cornaciu I, Oberer M, Kersten S, Zechner R, Zimmermann R, Lass A. G0/G1 switch gene-2 regulates human adipocyte lipolysis by affecting activity and localization of adipose triglyceride lipase. J Lipid Res 2012; 53:2307-17. [PMID: 22891293 DOI: 10.1194/jlr.m027409] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The hydrolysis of triglycerides in adipocytes, termed lipolysis, provides free fatty acids as energy fuel. Murine lipolysis largely depends on the activity of adipose triglyceride lipase (ATGL), which is regulated by two proteins annotated as comparative gene identification-58 (CGI-58) and G0/G1 switch gene-2 (G0S2). CGI-58 activates and G0S2 inhibits ATGL activity. In contrast to mice, the functional role of G0S2 in human adipocyte lipolysis is poorly characterized. Here we show that overexpression or silencing of G0S2 in human SGBS adipocytes decreases and increases lipolysis, respectively. Human G0S2 is upregulated during adipocyte differentiation and inhibits ATGL activity in a dose-dependent manner. Interestingly, C-terminally truncated ATGL mutants, which fail to localize to lipid droplets, translocate to the lipid droplet upon coexpression with G0S2, suggesting that G0S2 anchors ATGL to lipid droplets independent of ATGL's C-terminal lipid binding domain. Taken together, our results indicate that G0S2 also regulates human lipolysis by affecting enzyme activity and intracellular localization of ATGL. Increased lipolysis is known to contribute to the pathogenesis of insulin resistance, and G0S2 expression has been shown to be reduced in poorly controlled type 2 diabetic patients. Our data indicate that downregulation of G0S2 in adipose tissue could represent one of the underlying causes leading to increased lipolysis in the insulin-resistant state.
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Affiliation(s)
- Martina Schweiger
- Institute of Molecular Biosciences University of Graz, 8010 Graz, Austria
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62
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Agarwal AK. Lysophospholipid acyltransferases: 1-acylglycerol-3-phosphate O-acyltransferases. From discovery to disease. Curr Opin Lipidol 2012; 23:290-302. [PMID: 22777291 DOI: 10.1097/mol.0b013e328354fcf4] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
PURPOSE OF REVIEW Over the past several years, many more isoforms for the same enzymes, specifically for 1-acylglycerol-3-phosphate O-acyltransferases (AGPATs), have been cloned and studied. In this review, we summarize their biochemical features and discuss their functional role. RECENT FINDINGS The most significant role of these AGPATs appeared from our observation of AGPAT2 in the biology of adipose tissue (adipocytes) in humans and mice. Other isoforms are shown to be implicated in lung, reproductive and cardiac muscle function and in the cause of cancer. In-vitro substrate specificities of these AGPATs also suggest the in-vivo role of these AGPATs in remodeling of several of the glycerophospholipids. SUMMARY Despite significant progress in understanding the role of these AGPATs, much is still to be discovered in terms of how each of these AGPATs function in the presence or absence of other AGPATs and what their functional role might be.
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Affiliation(s)
- Anil K Agarwal
- Division of Nutrition and Metabolic Diseases, Department of Internal Medicine, Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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63
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Fontanesi L, Galimberti G, Calò DG, Fronza R, Martelli PL, Scotti E, Colombo M, Schiavo G, Casadio R, Buttazzoni L, Russo V. Identification and association analysis of several hundred single nucleotide polymorphisms within candidate genes for back fat thickness in Italian Large White pigs using a selective genotyping approach1. J Anim Sci 2012; 90:2450-64. [DOI: 10.2527/jas.2011-4797] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Affiliation(s)
- L. Fontanesi
- Department of Agro-Food Science and Technology, Sezione di Allevamenti Zootecnici, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy
- Centre of Genome Biology, University of Bologna, 40126 Bologna, Italy
| | - G. Galimberti
- Department of Statistical Sciences “Paolo Fortunati,” University of Bologna, Via delle Belle Arti 41, 40126 Bologna, Italy
| | - D. G. Calò
- Department of Statistical Sciences “Paolo Fortunati,” University of Bologna, Via delle Belle Arti 41, 40126 Bologna, Italy
| | - R. Fronza
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via San Giacomo, 40126 Bologna, Italy
| | - P. L. Martelli
- Centre of Genome Biology, University of Bologna, 40126 Bologna, Italy
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via San Giacomo, 40126 Bologna, Italy
| | - E. Scotti
- Department of Agro-Food Science and Technology, Sezione di Allevamenti Zootecnici, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy
| | - M. Colombo
- Department of Agro-Food Science and Technology, Sezione di Allevamenti Zootecnici, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy
| | - G. Schiavo
- Department of Agro-Food Science and Technology, Sezione di Allevamenti Zootecnici, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy
- Centre of Genome Biology, University of Bologna, 40126 Bologna, Italy
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via San Giacomo, 40126 Bologna, Italy
| | - R. Casadio
- Centre of Genome Biology, University of Bologna, 40126 Bologna, Italy
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via San Giacomo, 40126 Bologna, Italy
| | - L. Buttazzoni
- CRA, Centro di Ricerca per la Produzione delle Carni e il Miglioramento Genetico, Via Salaria 31, 00015 Monterotondo Scalo, Rome, Italy
| | - V. Russo
- Department of Agro-Food Science and Technology, Sezione di Allevamenti Zootecnici, University of Bologna, Viale Fanin 46, 40127 Bologna, Italy
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Myocardial triacylglycerol metabolism. J Mol Cell Cardiol 2012; 55:101-10. [PMID: 22789525 DOI: 10.1016/j.yjmcc.2012.06.018] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 06/22/2012] [Accepted: 06/28/2012] [Indexed: 11/22/2022]
Abstract
Myocardial triacylglycerol (TAG) constitutes a highly dynamic fatty acid (FA) storage pool that can be used for an energy reserve in the cardiomyocyte. However, derangements in myocardial TAG metabolism and accumulation are commonly associated with cardiac disease, suggesting an important role of intramyocardial TAG turnover in the regulation of cardiac function. In cardiomyocytes, TAG is synthesized by acyltransferases and phosphatases at the sarcoplasmic reticulum and mitochondrial membrane and then packaged into cytosolic lipid droplets for temporary storage or into lipoproteins for secretion. A complex interplay among lipases, lipase regulatory proteins, and lipid droplet scaffold proteins leads to the controlled release of FAs from the cardiac TAG pool for subsequent mitochondrial β-oxidation and energy production. With the identification and characterization of proteins involved in myocardial TAG metabolism as well as the identification of the importance of cardiac TAG turnover, it is now evident that adequate regulation of myocardial TAG metabolism is critical for both cardiac energy metabolism and function. In this article, we review the current understanding of myocardial TAG metabolism and discuss the potential role of myocardial TAG turnover in cardiac health and disease. This article is part of a Special Issue entitled "Focus on Cardiac Metabolism".
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65
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Lehner R, Lian J, Quiroga AD. Lumenal lipid metabolism: implications for lipoprotein assembly. Arterioscler Thromb Vasc Biol 2012; 32:1087-93. [PMID: 22517367 DOI: 10.1161/atvbaha.111.241497] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Overproduction of apolipoprotein B (apoB)-containing lipoproteins by the liver and the intestine is 1 of the hallmarks of insulin resistance and type 2 diabetes and a well-established risk factor of cardiovascular disease. The assembly of apoB lipoproteins is regulated by the availability of lipids that form the neutral lipid core (triacylglycerol and cholesteryl ester) and the limiting lipoprotein monolayer (phospholipids and cholesterol). Although tremendous advances have been made over the past decade toward understanding neutral lipid and phospholipid biosynthesis and neutral lipid storage in cytosolic lipid droplets (LDs), little is known about the mechanisms that govern the transfer of lipids to the lumen of the endoplasmic reticulum for apoB lipidation. ApoB-synthesizing organs can deposit synthesized neutral lipids into at least 3 different types of LDs, each decorated with a subset of specific proteins: perilipin-decorated cytosolic LDs, and 2 types of LDs formed in the lumen of the endoplasmic reticulum, the secretion-destined LDs containing apoB, and resident lumenal LDs coated with microsomal triglyceride transfer protein and exchangeable apolipoproteins. This brief review will address the current knowledge of lumenal lipid metabolism in the context of apoB assembly and lipid storage.
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Affiliation(s)
- Richard Lehner
- Department of Pediatrics and Cell Biology, Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada.
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66
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Kumari M, Schoiswohl G, Chitraju C, Paar M, Cornaciu I, Rangrez AY, Wongsiriroj N, Nagy HM, Ivanova PT, Scott SA, Knittelfelder O, Rechberger GN, Birner-Gruenberger R, Eder S, Brown HA, Haemmerle G, Oberer M, Lass A, Kershaw EE, Zimmermann R, Zechner R. Adiponutrin functions as a nutritionally regulated lysophosphatidic acid acyltransferase. Cell Metab 2012; 15:691-702. [PMID: 22560221 PMCID: PMC3361708 DOI: 10.1016/j.cmet.2012.04.008] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 02/17/2012] [Accepted: 04/10/2012] [Indexed: 12/12/2022]
Abstract
Numerous studies in humans link a nonsynonymous genetic polymorphism (I148M) in adiponutrin (ADPN) to various forms of fatty liver disease and liver cirrhosis. Despite its high clinical relevance, the molecular function of ADPN and the mechanism by which I148M variant affects hepatic metabolism are unclear. Here we show that ADPN promotes cellular lipid synthesis by converting lysophosphatidic acid (LPA) into phosphatidic acid. The ADPN-catalyzed LPA acyltransferase (LPAAT) reaction is specific for LPA and long-chain acyl-CoAs. Wild-type mice receiving a high-sucrose diet exhibit substantial upregulation of Adpn in the liver and a concomitant increase in LPAAT activity. In Adpn-deficient mice, this diet-induced increase in hepatic LPAAT activity is reduced. Notably, the I148M variant of human ADPN exhibits increased LPAAT activity leading to increased cellular lipid accumulation. This gain of function provides a plausible biochemical mechanism for the development of liver steatosis in subjects carrying the I148M variant.
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Affiliation(s)
- Manju Kumari
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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67
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Birner-Gruenberger R, Bickmeyer I, Lange J, Hehlert P, Hermetter A, Kollroser M, Rechberger GN, Kühnlein RP. Functional fat body proteomics and gene targeting reveal in vivo functions of Drosophila melanogaster α-Esterase-7. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2012; 42:220-229. [PMID: 22198472 DOI: 10.1016/j.ibmb.2011.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2011] [Revised: 12/07/2011] [Accepted: 12/08/2011] [Indexed: 05/31/2023]
Abstract
Carboxylesterases constitute a large enzyme family in insects, which is involved in diverse functions such as xenobiotic detoxification, lipid metabolism and reproduction. Phylogenetically, many insect carboxylesterases are represented by multienzyme clades, which are encoded by evolutionarily ancient gene clusters such as the α-Esterase cluster. Much in contrast to the vital importance attributed to carboxylesterases in general, the in vivo function of individual α-Esterase genes is largely unknown. This study employs a functional proteomics approach to identify esterolytic enzymes of the vinegar fly Drosophila melanogaster fat body. One of the fat body carboxylesterases, α-Esterase-7, was selected for mutational analysis by gene targeting to generate a deletion mutant fly. Phenotypic characterization of α-Esterase-7 null mutants and transgenic flies, which overexpress a chimeric α-Esterase-7:EGFP gene, reveals important functions of α-Esterase-7 in insecticide tolerance, lipid metabolism and lifespan control. The presented first deletion mutant of any α-Esterase in the model insect D. melanogaster generated by gene targeting not only provides experimental evidence for the endogenous functions of this gene family. It also offers an entry point for in vivo structure-function analyses of α-Esterase-7, which is of central importance for naturally occurring insecticide resistance in wild populations of various dipteran insect species.
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Affiliation(s)
- Ruth Birner-Gruenberger
- Research Group Functional Proteomics, Institute of Pathology, and Proteomics Core Facility, Center of Medical Research, Medical University of Graz, Stiftingtalstrasse 24, 8010 Graz, Austria
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68
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Badin PM, Loubière C, Coonen M, Louche K, Tavernier G, Bourlier V, Mairal A, Rustan AC, Smith SR, Langin D, Moro C. Regulation of skeletal muscle lipolysis and oxidative metabolism by the co-lipase CGI-58. J Lipid Res 2012; 53:839-848. [PMID: 22383684 DOI: 10.1194/jlr.m019182] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We investigated here the specific role of CGI-58 in the regulation of energy metabolism in skeletal muscle. We first examined CGI-58 protein expression in various muscle types in mice, and next modulated CGI-58 expression during overexpression and knockdown studies in human primary myotubes and evaluated the consequences on oxidative metabolism. We observed a preferential expression of CGI-58 in oxidative muscles in mice consistent with triacylglycerol hydrolase activity. We next showed by pulse-chase that CGI-58 overexpression increased by more than 2-fold the rate of triacylglycerol (TAG) hydrolysis, as well as TAG-derived fatty acid (FA) release and oxidation. Oppositely, CGI-58 silencing reduced TAG hydrolysis and TAG-derived FA release and oxidation (-77%, P < 0.001), whereas it increased glucose oxidation and glycogen synthesis. Interestingly, modulations of CGI-58 expression and FA release are reflected by changes in pyruvate dehydrogenase kinase 4 gene expression. This regulation involves the activation of the peroxisome proliferator activating receptor-δ (PPARδ) by lipolysis products. Altogether, these data reveal that CGI-58 plays a limiting role in the control of oxidative metabolism by modulating FA availability and the expression of PPARδ-target genes, and highlight an important metabolic function of CGI-58 in skeletal muscle.
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Affiliation(s)
- Pierre-Marie Badin
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Camille Loubière
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Maarten Coonen
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Katie Louche
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Geneviève Tavernier
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Virginie Bourlier
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Aline Mairal
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Arild C Rustan
- Department of Pharmaceutical Biosciences, School of Pharmacy, University of Oslo, Oslo, Norway
| | - Steven R Smith
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital and the Burnham Institute for Medical Research, Winter Park, FL
| | - Dominique Langin
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France
| | - Cedric Moro
- Inserm, 1048, Obesity Research Laboratory, Institute of Metabolic and Cardiovascular Diseases, Paul Sabatier University, Toulouse, France.
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69
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Bartholomew SR, Bell EH, Summerfield T, Newman LC, Miller EL, Patterson B, Niday ZP, Ackerman WE, Tansey JT. Distinct cellular pools of perilipin 5 point to roles in lipid trafficking. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1821:268-78. [PMID: 22063271 PMCID: PMC3740563 DOI: 10.1016/j.bbalip.2011.10.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2010] [Revised: 10/11/2011] [Accepted: 10/17/2011] [Indexed: 11/16/2022]
Abstract
The PAT family of lipid storage droplet proteins comprised five members, each of which has become an established regulator of cellular neutral lipid metabolism. Perilipin 5 (also known as lsdp-5, MLDP, PAT-1, and OXPAT), the most recently discovered member of the family, has been shown to localize to two distinct intracellular pools: the lipid storage droplet (LD), and a poorly characterized cytosolic fraction. We have characterized the denser of these intracellular pools and find that a population of perilipin 5 not associated with large LDs resides in complexes with a discrete density (~1.15 g/ml) and size (~575 kDa). Using immunofluorescence, western blotting of isolated sucrose density fractions, native gradient gel electrophoresis, and co-immunoprecipitation, we have shown that these small (~15 nm), perilipin 5-encoated structures do not contain the PAT protein perilipin 2 (ADRP), but do contain perilipin 3 and several other as of yet uncharacterized proteins. The size and density of these particles as well as their susceptibility to degradation by lipases suggest that like larger LDs, they have a neutral lipid rich core. When treated with oleic acid to promote neutral lipid deposition, cells ectopically expressing perilipin 5 experienced a reorganization of LDs in the cell, resulting in fewer, larger droplets at the expense of smaller ones. Collectively, these data demonstrate that a portion of cytosolic perilipin 5 resides in high density lipid droplet complexes that participate in cellular neutral lipid accumulation.
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Affiliation(s)
- Sadie R Bartholomew
- Department of Chemistry and Biochemistry, Otterbein University, Westerville, OH 43081, USA
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70
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Lord CC, Betters JL, Ivanova PT, Milne SB, Myers DS, Madenspacher J, Thomas G, Chung S, Liu M, Davis MA, Lee RG, Crooke RM, Graham MJ, Parks JS, Brasaemle DL, Fessler MB, Brown HA, Brown JM. CGI-58/ABHD5-derived signaling lipids regulate systemic inflammation and insulin action. Diabetes 2012; 61:355-63. [PMID: 22228714 PMCID: PMC3266405 DOI: 10.2337/db11-0994] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Mutations of comparative gene identification 58 (CGI-58) in humans cause Chanarin-Dorfman syndrome, a rare autosomal recessive disease in which excess triacylglycerol (TAG) accumulates in multiple tissues. CGI-58 recently has been ascribed two distinct biochemical activities, including coactivation of adipose triglyceride lipase and acylation of lysophosphatidic acid (LPA). It is noteworthy that both the substrate (LPA) and the product (phosphatidic acid) of the LPA acyltransferase reaction are well-known signaling lipids. Therefore, we hypothesized that CGI-58 is involved in generating lipid mediators that regulate TAG metabolism and insulin sensitivity. Here, we show that CGI-58 is required for the generation of signaling lipids in response to inflammatory stimuli and that lipid second messengers generated by CGI-58 play a critical role in maintaining the balance between inflammation and insulin action. Furthermore, we show that CGI-58 is necessary for maximal TH1 cytokine signaling in the liver. This novel role for CGI-58 in cytokine signaling may explain why diminished CGI-58 expression causes severe hepatic lipid accumulation yet paradoxically improves hepatic insulin action. Collectively, these findings establish that CGI-58 provides a novel source of signaling lipids. These findings contribute insight into the basic mechanisms linking TH1 cytokine signaling to nutrient metabolism.
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Affiliation(s)
- Caleb C. Lord
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Jenna L. Betters
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Pavlina T. Ivanova
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Stephen B. Milne
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - David S. Myers
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jennifer Madenspacher
- Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - Gwynneth Thomas
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Soonkyu Chung
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Mingxia Liu
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Matthew A. Davis
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Richard G. Lee
- Cardiovascular Group, Antisense Drug Discovery, Isis Pharmaceuticals, Carlsbad, California
| | - Rosanne M. Crooke
- Cardiovascular Group, Antisense Drug Discovery, Isis Pharmaceuticals, Carlsbad, California
| | - Mark J. Graham
- Cardiovascular Group, Antisense Drug Discovery, Isis Pharmaceuticals, Carlsbad, California
| | - John S. Parks
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Dawn L. Brasaemle
- Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey
| | - Michael B. Fessler
- Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina
| | - H. Alex Brown
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - J. Mark Brown
- Department of Pathology, Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, North Carolina
- Corresponding author: J. Mark Brown,
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71
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Coleman RA, Mashek DG. Mammalian triacylglycerol metabolism: synthesis, lipolysis, and signaling. Chem Rev 2011; 111:6359-86. [PMID: 21627334 PMCID: PMC3181269 DOI: 10.1021/cr100404w] [Citation(s) in RCA: 210] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rosalind A Coleman
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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72
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Kelly AA, Quettier AL, Shaw E, Eastmond PJ. Seed storage oil mobilization is important but not essential for germination or seedling establishment in Arabidopsis. PLANT PHYSIOLOGY 2011; 157:866-75. [PMID: 21825108 PMCID: PMC3192569 DOI: 10.1104/pp.111.181784] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 08/04/2011] [Indexed: 05/18/2023]
Abstract
Triacylglycerol (TAG) is a major storage reserve in many plant seeds. We previously identified a TAG lipase mutant called sugar-dependent1 (sdp1) that is impaired in TAG hydrolysis following Arabidopsis (Arabidopsis thaliana) seed germination (Eastmond, 2006). The aim of this study was to identify additional lipases that account for the residual TAG hydrolysis observed in sdp1. Mutants were isolated in three candidate genes (SDP1-LIKE [SDP1L], ADIPOSE TRIGLYCERIDE LIPASE-LIKE, and COMPARATIVE GENE IDENTIFIER-58-LIKE). Analysis of double, triple, and quadruple mutants showed that SDP1L is responsible for virtually all of the residual TAG hydrolysis present in sdp1 seedlings. Oil body membranes purified from sdp1 sdp1L seedlings were deficient in TAG lipase activity but could still hydrolyze di- and monoacylglycerol. SDP1L is expressed less strongly than SDP1 in seedlings. However, SDP1L could partially rescue TAG breakdown in sdp1 seedlings when expressed under the control of the SDP1 or 35S promoters and in vitro assays showed that both SDP1 and SDP1L can hydrolyze TAG, in preference to diacylglycerol or monoacylglycerol. Seed germination was slowed in sdp1 sdp1L and postgerminative seedling growth was severely retarded. The frequency of seedling establishment was also reduced, but sdp1 sdp1L was not seedling lethal under normal laboratory growth conditions. Our data show that together SDP1 and SDP1L account for at least 95% of the rate of TAG hydrolysis in Arabidopsis seeds, and that this hydrolysis is important but not essential for seed germination or seedling establishment.
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73
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Caviglia JM, Betters JL, Dapito DH, Lord CC, Sullivan S, Chua S, Yin T, Sekowski A, Mu H, Shapiro L, Brown JM, Brasaemle DL. Adipose-selective overexpression of ABHD5/CGI-58 does not increase lipolysis or protect against diet-induced obesity. J Lipid Res 2011; 52:2032-42. [PMID: 21885429 DOI: 10.1194/jlr.m019117] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Adipose triglyceride lipase (ATGL) catalyzes the first step of triacylglycerol hydrolysis in adipocytes. Abhydrolase domain 5 (ABHD5) increases ATGL activity by an unknown mechanism. Prior studies have suggested that the expression of ABHD5 is limiting for lipolysis in adipocytes, as addition of recombinant ABHD5 increases in vitro TAG hydrolase activity of adipocyte lysates. To test this hypothesis in vivo, we generated transgenic mice that express 6-fold higher ABHD5 in adipose tissue relative to wild-type (WT) mice. In vivo lipolysis increased to a similar extent in ABHD5 transgenic and WT mice following an overnight fast or injection of either a β-adrenergic receptor agonist or lipopolysaccharide. Similarly, basal and β-adrenergic-stimulated lipolysis was comparable in adipocytes isolated from ABHD5 transgenic and WT mice. Although ABHD5 expression was elevated in thioglycolate-elicited macrophages from ABHD5 transgenic mice, Toll-like receptor 4 (TLR4) signaling was comparable in macrophages isolated from ABHD5 transgenic and WT mice. Overexpression of ABHD5 did not prevent the development of obesity in mice fed a high-fat diet, as shown by comparison of body weight, body fat percentage, and adipocyte hypertrophy of ABHD5 transgenic to WT mice. The expression of ABHD5 in mouse adipose tissue is not limiting for either basal or stimulated lipolysis.
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Affiliation(s)
- Jorge M Caviglia
- Rutgers Center for Lipid Research and Department of Nutritional Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA
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74
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Oberer M, Boeszoermenyi A, Nagy HM, Zechner R. Recent insights into the structure and function of comparative gene identification-58. Curr Opin Lipidol 2011; 22:149-58. [PMID: 21494142 PMCID: PMC5808844 DOI: 10.1097/mol.0b013e328346230e] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE OF REVIEW Comparative gene identification-58 (CGI-58) is an important player in lipid metabolism. It acts as activator of triglyceride hydrolases and as acyl-CoA-dependent lysophosphatidic acid acyltransferase. This review aims at establishing a structure-function relationship of this still rather enigmatic protein based on recent studies characterizing different functions of CGI-58. RECENT FINDINGS Novel studies confirm the important regulatory role of CGI-58 as activator of the triglyceride hydrolase adipose triglyceride lipase. New evidence, corroborated by the characterization of a CGI-58 knockout mouse model, also suggests the existence of yet unknown lipases that are activated by CGI-58. Additionally, CGI-58 was identified to exert acyl-CoA-dependent lysophosphatidic acid acyltransferase activity, which implies possible roles in triglyceride or phospholipid synthesis or signaling processes. Unlike mammalian CGI-58 proteins, orthologs from plants and yeast additionally act as weak triglyceride and phospholipid hydrolases. A first three-dimensional model was calculated and allows preliminary structural considerations for the functions of CGI-58. SUMMARY Despite important progress concerning the different biochemical functions of CGI-58, the physiological importance of these activities requires better characterization. Furthermore, three-dimensional structural data for CGI-58 are required to unveil the molecular mechanism of how CGI-58 acts as activator of lipases and exerts its enzymatic functions.
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Affiliation(s)
- Monika Oberer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Andras Boeszoermenyi
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Harald Manuel Nagy
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010 Graz, Austria
| | - Rudolf Zechner
- Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, 8010 Graz, Austria
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75
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Radner FP, Grond S, Haemmerle G, Lass A, Zechner R. Fat in the skin: Triacylglycerol metabolism in keratinocytes and its role in the development of neutral lipid storage disease. DERMATO-ENDOCRINOLOGY 2011; 3:77-83. [PMID: 21695016 PMCID: PMC3117006 DOI: 10.4161/derm.3.2.15472] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 03/10/2011] [Accepted: 03/11/2011] [Indexed: 12/11/2022]
Abstract
Keratinocyte differentiation is essential for skin development and the formation of the skin permeability barrier. This process involves an orchestrated remodeling of lipids. The cleavage of precursor lipids from lamellar bodies by β-glucocerebrosidase, sphingomyelinase, phospholipases and sterol sulfatase generates ceramides, non-esterified fatty acids and cholesterol for the lipid-containing extracellular matrix, the lamellar membranes in the stratum corneum. The importance of triacylglycerol (TAG) hydrolysis for the formation of a functional permeability barrier was only recently appreciated. Mice with defects in TAG synthesis (acyl-CoA:diacylglycerol acyltransferase-2-knock-out) or TAG catabolism (comparative gene identification-58, -CGI-58-knock-out) develop severe permeability barrier defects and die soon after birth because of desiccation. In humans, mutations in the CGI-58 gene also cause (non-lethal) neutral lipid storage disease with ichthyosis. As a result of defective TAG synthesis or catabolism, humans and mice lack ω-(O)-acylceramides, which are essential lipid precursors for the formation of the corneocyte lipid envelope. This structure plays an important role in linking the lipid-enriched lamellar membranes to highly cross-linked corneocyte proteins. This review focuses on the current knowledge of biochemical mechanisms that are essential for epidermal neutral lipid metabolism and the formation of a functional skin permeability barrier.
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Affiliation(s)
- Franz Pw Radner
- Institute of Molecular Biosciences; University of Graz; Graz, Austria
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76
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Granneman JG, Moore HPH, Mottillo EP, Zhu Z, Zhou L. Interactions of perilipin-5 (Plin5) with adipose triglyceride lipase. J Biol Chem 2010; 286:5126-35. [PMID: 21148142 DOI: 10.1074/jbc.m110.180711] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the perilipin family of lipid droplet scaffold proteins are thought to play important roles in tissue-specific regulation of triglyceride metabolism, but the mechanisms involved are not fully understood. Present results indicate that adipose triglyceride lipase (Atgl) interacts with perilipin-5 (Plin5) but not perilipin-1 (Plin1). Protein interaction assays in live cells and in situ binding experiments showed that Atgl and its protein activator, α-β-hydrolase domain-containing 5 (Abhd5), each bind Plin5. Surprisingly, competition experiments indicated that individual Plin5 molecules bind Atgl or Abhd5 but not both simultaneously. Thus, the ability of Plin5 to concentrate these proteins at droplet surfaces involves binding to different Plin5 molecules, possibly in an oligomeric complex. The association of Plin5-Abhd5 complexes on lipid droplet surfaces was more stable than Plin5-Atgl complexes, and oleic acid treatment selectively promoted the interaction of Plin5 and Abhd5. Analysis of chimeric and mutant perilipin proteins demonstrated that amino acids 200-463 are necessary and sufficient to bind both Atgl and Abhd5 and that the C-terminal 64 amino acids of Plin5 are critical for the differential binding of Atgl to Plin5 and Plin1. Mutant Plin5 that binds Abhd5 but not Atgl was defective in preventing neutral lipid accumulation compared with wild type Plin5, indicating that the ability of Plin5 to concentrate these proteins on lipid droplets is critical to functional Atgl activity in cells.
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Affiliation(s)
- James G Granneman
- Center for Integrative Metabolic and Endocrine Research, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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77
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Redaelli C, Coleman RA, Moro L, Dacou-Voutetakis C, Elsayed SM, Prati D, Colli A, Mela D, Colombo R, Tavian D. Clinical and genetic characterization of Chanarin-Dorfman syndrome patients: first report of large deletions in the ABHD5 gene. Orphanet J Rare Dis 2010; 5:33. [PMID: 21122093 PMCID: PMC3019207 DOI: 10.1186/1750-1172-5-33] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 12/01/2010] [Indexed: 12/02/2022] Open
Abstract
Background Chanarin-Dorfman syndrome (CDS) is a rare autosomal recessive disorder characterized by nonbullous congenital ichthyosiform erythroderma (NCIE) and an intracellular accumulation of triacylglycerol (TG) droplets in most tissues. The clinical phenotype involves multiple organs and systems, including liver, eyes, ears, skeletal muscle and central nervous system (CNS). Mutations in ABHD5/CGI58 gene are associated with CDS. Methods Eight CDS patients belonging to six different families from Mediterranean countries were enrolled for genetic study. Molecular analysis of the ABHD5 gene included the sequencing of the 7 coding exons and of the putative 5' regulatory regions, as well as reverse transcript-polymerase chain reaction analysis and sequencing of normal and aberrant ABHD5 cDNAs. Results Five different mutations were identified, four of which were novel, including two splice-site mutations (c.47+1G>A and c.960+5G>A) and two large deletions (c.898_*320del and c.662-1330_773+46del). All the reported mutations are predicted to be pathogenic because they lead to an early stop codon or a frameshift producing a premature termination of translation. While nonsense, missense, frameshift and splice-site mutations have been identified in CDS patients, large genomic deletions have not previously been described. Conclusions These results emphasize the need for an efficient approach for genomic deletion screening to ensure an accurate molecular diagnosis of CDS. Moreover, in spite of intensive molecular screening, no mutations were identified in one patient with a confirmed clinical diagnosis of CDS, appointing to genetic heterogeneity of the syndrome.
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Affiliation(s)
- Chiara Redaelli
- Department of Psychology, Catholic University of the Sacred Heart, Milan, Italy
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78
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Lass A, Zimmermann R, Oberer M, Zechner R. Lipolysis - a highly regulated multi-enzyme complex mediates the catabolism of cellular fat stores. Prog Lipid Res 2010; 50:14-27. [PMID: 21087632 PMCID: PMC3031774 DOI: 10.1016/j.plipres.2010.10.004] [Citation(s) in RCA: 454] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 10/12/2010] [Accepted: 10/13/2010] [Indexed: 12/17/2022]
Abstract
Lipolysis is the biochemical pathway responsible for the catabolism of triacylglycerol (TAG) stored in cellular lipid droplets. The hydrolytic cleavage of TAG generates non-esterified fatty acids, which are subsequently used as energy substrates, essential precursors for lipid and membrane synthesis, or mediators in cell signaling processes. Consistent with its central importance in lipid and energy homeostasis, lipolysis occurs in essentially all tissues and cell types, it is most abundant, however, in white and brown adipose tissue. Over the last 5years, important enzymes and regulatory protein factors involved in lipolysis have been identified. These include an essential TAG hydrolase named adipose triglyceride lipase (ATGL) [annotated as patatin-like phospholipase domain-containing protein A2], the ATGL activator comparative gene identification-58 [annotated as α/β hydrolase containing protein 5], and the ATGL inhibitor G0/G1 switch gene 2. Together with the established hormone-sensitive lipase [annotated as lipase E] and monoglyceride lipase, these proteins constitute the basic "lipolytic machinery". Additionally, a large number of hormonal signaling pathways and lipid droplet-associated protein factors regulate substrate access and the activity of the "lipolysome". This review summarizes the current knowledge concerning the enzymes and regulatory processes governing lipolysis of fat stores in adipose and non-adipose tissues. Special emphasis will be given to ATGL, its regulation, and physiological function.
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Affiliation(s)
- Achim Lass
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
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79
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Disruption of the Arabidopsis CGI-58 homologue produces Chanarin-Dorfman-like lipid droplet accumulation in plants. Proc Natl Acad Sci U S A 2010; 107:17833-8. [PMID: 20876112 DOI: 10.1073/pnas.0911359107] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CGI-58 is the defective gene in the human neutral lipid storage disease called Chanarin-Dorfman syndrome. This disorder causes intracellular lipid droplets to accumulate in nonadipose tissues, such as skin and blood cells. Here, disruption of the homologous CGI-58 gene in Arabidopsis thaliana resulted in the accumulation of neutral lipid droplets in mature leaves. Mass spectroscopy of isolated lipid droplets from cgi-58 loss-of-function mutants showed they contain triacylglycerols with common leaf-specific fatty acids. Leaves of mature cgi-58 plants exhibited a marked increase in absolute triacylglycerol levels, more than 10-fold higher than in wild-type plants. Lipid levels in the oil-storing seeds of cgi-58 loss-of-function plants were unchanged, and unlike mutations in β-oxidation, the cgi-58 seeds germinated and grew normally, requiring no rescue with sucrose. We conclude that the participation of CGI-58 in neutral lipid homeostasis of nonfat-storing tissues is similar, although not identical, between plant and animal species. This unique insight may have implications for designing a new generation of technologies that enhance the neutral lipid content and composition of crop plants.
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80
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Yamaguchi T. Crucial role of CGI-58/alpha/beta hydrolase domain-containing protein 5 in lipid metabolism. Biol Pharm Bull 2010; 33:342-5. [PMID: 20190389 DOI: 10.1248/bpb.33.342] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The surfaces of lipid droplets (LDs) constitute major sites of regulated accumulation and degradation of lipid in cells, and hence play important roles in lipid homeostasis of the whole body. CGI-58 (also called alpha/beta hydrolase domain-containing protein 5 (ABHD5)) is a member of the alpha/beta-hydrolase family of proteins and is a product of the causal gene of Chanarin-Dorfman syndrome (CDS), which is characterized by excessive storage of triacylglycerol (TG) in various tissues. CGI-58 is distributed predominantly on the surface of LDs and plays a crucial role in TG degradation in cells. In the process of lipolysis, CGI-58 coordinates with several proteins, including perilipin, a member of the PAT family of proteins, and adipose triglyceride lipase (ATGL), a putative rate-limiting enzyme for TG degradation in adipocytes. Besides its role in adipocytes, CGI-58 is involved in lipid degradation in various tissues, including those of skin and liver. This review focuses on the functions and protein interactions of CGI-58 on the surface of LDs in the regulation of fat mobilization in cells.
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Affiliation(s)
- Tomohiro Yamaguchi
- School of Pharmaceutical Sciences, Showa University, Shinagawa, Tokyo 142-8555, Japan
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81
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Granneman JG, Kimler VA, Moore HPH. Cell Biology Symposium: imaging the organization and trafficking of lipolytic effectors in adipocytes. J Anim Sci 2010; 89:701-10. [PMID: 20852075 DOI: 10.2527/jas.2010-3370] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The storage and mobilization of lipid energy are central functions of adipocytes. Lipid energy is stored as triglyceride in lipid droplet structures that are now recognized as bona fide organelles and whose functions are greatly influenced by members of the perilipin family of lipid droplet scaffolds. Recent work indicates that the signaling events underlying fatty acid mobilization involve protein trafficking to a specialized subset of lipid droplets. Furthermore, the core lipolytic machinery is composed of evolutionarily conserved proteins whose functions are conserved in avian and mammalian production species. Lipolysis affects many aspects of animal nutrition and physiology, which can have an important influence on growth efficiency, lactation, and meat quality. This review focuses on recent research that addresses the organization and trafficking of key players in hormone-stimulated lipolysis, and the central role of perilipin1A in adipocyte lipolysis. The review emphasizes recent work from the laboratories of the authors that utilizes imaging techniques to explore the organization and interactions among lipolytic effectors in live cells during lipolytic activation. A mechanistic understanding of lipolysis may lead to new strategies for promoting human and animal health.
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Affiliation(s)
- J G Granneman
- Center for Integrative Metabolic and Endocrine Research, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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82
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Brown JM, Betters JL, Lord C, Ma Y, Han X, Yang K, Alger HM, Melchior J, Sawyer J, Shah R, Wilson MD, Liu X, Graham MJ, Lee R, Crooke R, Shulman GI, Xue B, Shi H, Yu L. CGI-58 knockdown in mice causes hepatic steatosis but prevents diet-induced obesity and glucose intolerance. J Lipid Res 2010; 51:3306-15. [PMID: 20802159 DOI: 10.1194/jlr.m010256] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Mutations of Comparative Gene Identification-58 (CGI-58) in humans cause triglyceride (TG) accumulation in multiple tissues. Mice genetically lacking CGI-58 die shortly after birth due to a skin barrier defect. To study the role of CGI-58 in integrated lipid and energy metabolism, we utilized antisense oligonucleotides (ASOs) to inhibit CGI-58 expression in adult mice. Treatment with two distinct CGI-58-targeting ASOs resulted in ∼80-95% knockdown of CGI-58 protein expression in both liver and white adipose tissue. In chow-fed mice, ASO-mediated depletion of CGI-58 did not alter weight gain, plasma TG, or plasma glucose, yet raised hepatic TG levels ∼4-fold. When challenged with a high-fat diet (HFD), CGI-58 ASO-treated mice were protected against diet-induced obesity, but their hepatic contents of TG, diacylglycerols, and ceramides were all elevated, and intriguingly, their hepatic phosphatidylglycerol content was increased by 10-fold. These hepatic lipid alterations were associated with significant decreases in hepatic TG hydrolase activity, hepatic lipoprotein-TG secretion, and plasma concentrations of ketones, nonesterified fatty acids, and insulin. Additionally, HFD-fed CGI-58 ASO-treated mice were more glucose tolerant and insulin sensitive. Collectively, this work demonstrates that CGI-58 plays a critical role in limiting hepatic steatosis and maintaining hepatic glycerophospholipid homeostasis and has unmasked an unexpected role for CGI-58 in promoting HFD-induced obesity and insulin resistance.
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Affiliation(s)
- J Mark Brown
- Departments of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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83
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Radner FPW, Streith IE, Schoiswohl G, Schweiger M, Kumari M, Eichmann TO, Rechberger G, Koefeler HC, Eder S, Schauer S, Theussl HC, Preiss-Landl K, Lass A, Zimmermann R, Hoefler G, Zechner R, Haemmerle G. Growth retardation, impaired triacylglycerol catabolism, hepatic steatosis, and lethal skin barrier defect in mice lacking comparative gene identification-58 (CGI-58). J Biol Chem 2010; 285:7300-11. [PMID: 20023287 PMCID: PMC2844178 DOI: 10.1074/jbc.m109.081877] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 12/14/2009] [Indexed: 11/06/2022] Open
Abstract
Comparative gene identification-58 (CGI-58), also designated as alpha/beta-hydrolase domain containing-5 (ABHD-5), is a lipid droplet-associated protein that activates adipose triglyceride lipase (ATGL) and acylates lysophosphatidic acid. Activation of ATGL initiates the hydrolytic catabolism of cellular triacylglycerol (TG) stores to glycerol and nonesterified fatty acids. Mutations in both ATGL and CGI-58 cause "neutral lipid storage disease" characterized by massive accumulation of TG in various tissues. The analysis of CGI-58-deficient (Cgi-58(-/-)) mice, presented in this study, reveals a dual function of CGI-58 in lipid metabolism. First, systemic TG accumulation and severe hepatic steatosis in newborn Cgi-58(-/-) mice establish a limiting role for CGI-58 in ATGL-mediated TG hydrolysis and supply of nonesterified fatty acids as energy substrate. Second, a severe skin permeability barrier defect uncovers an essential ATGL-independent role of CGI-58 in skin lipid metabolism. The neonatal lethal skin barrier defect is linked to an impaired hydrolysis of epidermal TG. As a consequence, sequestration of fatty acids in TG prevents the synthesis of acylceramides, which are essential lipid precursors for the formation of a functional skin permeability barrier. This mechanism may also underlie the pathogenesis of ichthyosis in neutral lipid storage disease patients lacking functional CGI-58.
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Affiliation(s)
- Franz P. W. Radner
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Ingo E. Streith
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Gabriele Schoiswohl
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Martina Schweiger
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Manju Kumari
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Thomas O. Eichmann
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Gerald Rechberger
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | | | - Sandra Eder
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Silvia Schauer
- the Institute of Pathology, Medical University of Graz, A-8010 Graz, and
| | | | - Karina Preiss-Landl
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Achim Lass
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Robert Zimmermann
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Gerald Hoefler
- the Institute of Pathology, Medical University of Graz, A-8010 Graz, and
| | - Rudolf Zechner
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
| | - Guenter Haemmerle
- From the Institute of Molecular Biosciences, University of Graz, Heinrichstrasse 31, A-8010 Graz
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84
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Gruber A, Cornaciu I, Lass A, Schweiger M, Poeschl M, Eder C, Kumari M, Schoiswohl G, Wolinski H, Kohlwein SD, Zechner R, Zimmermann R, Oberer M. The N-terminal region of comparative gene identification-58 (CGI-58) is important for lipid droplet binding and activation of adipose triglyceride lipase. J Biol Chem 2010; 285:12289-98. [PMID: 20164531 DOI: 10.1074/jbc.m109.064469] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In mammals, excess energy is stored in the form of triacylglycerol primarily in lipid droplets of white adipose tissue. The first step of lipolysis (i.e. the mobilization of fat stores) is catalyzed by adipose triglyceride lipase (ATGL). The enzymatic activity of ATGL is strongly enhanced by CGI-58 (comparative gene identification-58), and the loss of either ATGL or CGI-58 function causes systemic triglyceride accumulation in humans and mice. However, the mechanism by which CGI-58 stimulates ATGL activity is unknown. To gain insight into CGI-58 function using structural features of the protein, we generated a three-dimensional homology model based on sequence similarity with other proteins. Interestingly, the model of CGI-58 revealed that the N terminus forms an extension of the otherwise compact structure of the protein. This N-terminal region (amino acids 1-30) harbors a lipophilic tryptophan-rich stretch, which affects the localization of the protein. (1)H NMR experiments revealed strong interaction between the N-terminal peptide and dodecylphosphocholine micelles as a lipid droplet-mimicking system. A role for this N-terminal region of CGI-58 in lipid droplet binding was further strengthened by localization studies in cultured cells. Although wild-type CGI-58 localizes to the lipid droplet, the N-terminally truncated fragments of CGI-58 are dispersed in the cytoplasm. Moreover, CGI-58 lacking the N-terminal extension loses the ability to stimulate ATGL, implying that the ability of CGI-58 to activate ATGL is linked to correct localization. In summary, our study shows that the N-terminal, Trp-rich region of CGI-58 is essential for correct localization and ATGL-activating function of CGI-58.
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Affiliation(s)
- Astrid Gruber
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse, A-8010 Graz, Austria
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85
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Identification of a novel splicing isoform of murine CGI-58. FEBS Lett 2010; 584:903-10. [PMID: 20083112 DOI: 10.1016/j.febslet.2009.12.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 12/13/2009] [Accepted: 12/23/2009] [Indexed: 11/23/2022]
Abstract
The comparative gene identification-58 (CGI-58) gene, mutations of which are linked to Chanarin-Dorfman syndrome, encodes a protein of the alpha/beta hydrolase domain subfamily. We report here a new alternative splicing isoform of the murine CGI-58 gene, termed mCGI-58S. Sequence comparison indicates the lack of second and third exons in this cDNA variant. While the full-length protein displayed perilipin-dependent localization to lipid droplets, mCGI-58S showed a predominant cytoplasmic staining when expressed in cells. mCGI-58S was incapable of activating adipose triglyceride lipase but retained the capacity to acylate lysophosphatidic acid. Overexpression of mCGI-58S failed to promote lipid droplet turnover and loss of intracellular triacylglycerols. These results suggest that this splicing event may be involved in the regulation of lipid homeostasis.
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86
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Sandhoff R. Very long chain sphingolipids: Tissue expression, function and synthesis. FEBS Lett 2009; 584:1907-13. [DOI: 10.1016/j.febslet.2009.12.032] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 12/18/2009] [Indexed: 11/26/2022]
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87
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Rajakumari S, Daum G. Janus-faced enzymes yeast Tgl3p and Tgl5p catalyze lipase and acyltransferase reactions. Mol Biol Cell 2009; 21:501-10. [PMID: 20016004 PMCID: PMC2820416 DOI: 10.1091/mbc.e09-09-0775] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The yeast triacylglycerol (TAG) lipases Tgl3p and Tgl5p not only contain a TAG lipase, but also an acyltransferase motif. We show that purified Tgl3p and Tgl5p indeed exhibit lysophospholipid acyltransferase activity. Both Tgl3p and Tgl5p affect the level of glycerophospholipids, and Tgl3p is also important for efficient sporulation of yeast. In the yeast, mobilization of triacylglycerols (TAGs) is facilitated by the three TAG lipases Tgl3p, Tgl4p, and Tgl5p. Motif search analysis, however, indicated that Tgl3p and Tgl5p do not only contain the TAG lipase motif GXSXG but also an H-(X)4-D acyltransferase motif. Interestingly, lipid analysis revealed that deletion of TGL3 resulted in a decrease and overexpression of TGL3 in an increase of glycerophospholipids. Similar results were obtained with TGL5. Therefore, we tested purified Tgl3p and Tgl5p for acyltransferase activity. Indeed, both enzymes not only exhibited lipase activity but also catalyzed acylation of lysophosphatidylethanolamine and lysophosphatidic acid, respectively. Experiments using variants of Tgl3p created by site-directed mutagenesis clearly demonstrated that the two enzymatic activities act independently of each other. We also showed that Tgl3p is important for efficient sporulation of yeast cells, but rather through its acyltransferase than lipase activity. In summary, our results demonstrate that yeast Tgl3p and Tgl5p play a dual role in lipid metabolism contributing to both anabolic and catabolic processes.
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Affiliation(s)
- Sona Rajakumari
- Institute of Biochemistry, Graz University of Technology, A-8010 Graz, Austria
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88
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Montero-Moran G, Caviglia JM, McMahon D, Rothenberg A, Subramanian V, Xu Z, Lara-Gonzalez S, Storch J, Carman GM, Brasaemle DL. CGI-58/ABHD5 is a coenzyme A-dependent lysophosphatidic acid acyltransferase. J Lipid Res 2009; 51:709-19. [PMID: 19801371 DOI: 10.1194/jlr.m001917] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mutations in human CGI-58/ABHD5 cause Chanarin-Dorfman syndrome (CDS), characterized by excessive storage of triacylglycerol in tissues. CGI-58 is an alpha/beta-hydrolase fold enzyme expressed in all vertebrates. The carboxyl terminus includes a highly conserved consensus sequence (HXXXXD) for acyltransferase activity. Mouse CGI-58 was expressed in Escherichia coli as a fusion protein with two amino terminal 6-histidine tags. Recombinant CGI-58 displayed acyl-CoA-dependent acyltransferase activity to lysophosphatidic acid, but not to other lysophospholipid or neutral glycerolipid acceptors. Production of phosphatidic acid increased with time and increasing concentrations of recombinant CGI-58 and was optimal between pH 7.0 and 8.5. The enzyme showed saturation kinetics with respect to 1-oleoyl-lysophosphatidic acid and oleoyl-CoA and preference for arachidonoyl-CoA and oleoyl-CoA. The enzyme showed slight preference for 1-oleoyl lysophosphatidic acid over 1-palmitoyl, 1-stearoyl, or 1-arachidonoyl lysophosphatidic acid. Recombinant CGI-58 showed intrinsic fluorescence for tryptophan that was quenched by the addition of 1-oleoyl-lysophosphatidic acid, oleoyl-CoA, arachidonoyl-CoA, and palmitoyl-CoA, but not by lysophosphatidyl choline. Expression of CGI-58 in fibroblasts from humans with CDS increased the incorporation of radiolabeled fatty acids released from the lipolysis of stored triacylglycerols into phospholipids. CGI-58 is a CoA-dependent lysophosphatidic acid acyltransferase that channels fatty acids released from the hydrolysis of stored triacylglycerols into phospholipids.
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Affiliation(s)
- Gabriela Montero-Moran
- Rutgers Center for Lipid Research, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA
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89
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Olofsson SO, Boström P, Andersson L, Li L, Højlund K, Adiels M, Perkins R, Borén J. Lipid droplets and their role in the development of insulin resistance and diabetic dyslipidemia. ACTA ACUST UNITED AC 2009. [DOI: 10.2217/clp.09.54] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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90
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Ghosh AK, Chauhan N, Rajakumari S, Daum G, Rajasekharan R. At4g24160, a soluble acyl-coenzyme A-dependent lysophosphatidic acid acyltransferase. PLANT PHYSIOLOGY 2009; 151:869-81. [PMID: 19700561 PMCID: PMC2754629 DOI: 10.1104/pp.109.144261] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 08/17/2009] [Indexed: 05/19/2023]
Abstract
Human CGI-58 (for comparative gene identification-58) and YLR099c, encoding Ict1p in Saccharomyces cerevisiae, have recently been identified as acyl-CoA-dependent lysophosphatidic acid acyltransferases. Sequence database searches for CGI-58 like proteins in Arabidopsis (Arabidopsis thaliana) revealed 24 proteins with At4g24160, a member of the alpha/beta-hydrolase family of proteins being the closest homolog. At4g24160 contains three motifs that are conserved across the plant species: a GXSXG lipase motif, a HX(4)D acyltransferase motif, and V(X)(3)HGF, a probable lipid binding motif. Dendrogram analysis of yeast ICT1, CGI-58, and At4g24160 placed these three polypeptides in the same group. Here, we describe and characterize At4g24160 as, to our knowledge, the first soluble lysophosphatidic acid acyltransferase in plants. A lipidomics approach revealed that At4g24160 has additional triacylglycerol lipase and phosphatidylcholine hydrolyzing enzymatic activities. These data establish At4g24160, a protein with a previously unknown function, as an enzyme that might play a pivotal role in maintaining the lipid homeostasis in plants by regulating both phospholipid and neutral lipid levels.
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Affiliation(s)
- Ananda K Ghosh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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91
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Abstract
Human obesity and its complications are an increasing burden in developed and underdeveloped countries. Adipose tissue mass and the mechanisms that control it are central to elucidating the aetiology of obesity and insulin resistance. Over the past 15 years tremendous progress has been made in several avenues relating to adipose tissue. Knowledge of the lipolytic machinery has grown with the identification of new lipases, cofactors and interactions between proteins and lipids that are central to the regulation of basal and stimulated lipolysis. The dated idea of an inert lipid droplet has been appropriately revamped to that of a dynamic and highly-structured organelle that in itself offers regulatory control over lipolysis. The present review provides an overview of the numerous partners and pathways involved in adipose tissue lipolysis and their interaction under various metabolic states. Integration of these findings into whole adipose tissue metabolism and its systemic effects is also presented in the context of inflammation and insulin resistance.
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92
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Goodman JM. Demonstrated and inferred metabolism associated with cytosolic lipid droplets. J Lipid Res 2009; 50:2148-56. [PMID: 19696439 DOI: 10.1194/jlr.r001446] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cytosolic lipid droplets were considered until recently to be rather inert particles of stored neutral lipid. Largely through proteomics is it now known that droplets are dynamic organelles and that they participate in several important metabolic reactions as well as trafficking and interorganellar communication. In this review, the role of droplets in metabolism in the yeast Saccharomyces cerevisiae, the fly Drosophila melanogaster, and several mammalian sources are discussed, particularly focusing on those reactions shared by these organisms. From proteomics and older work, it is clear that droplets are important for fatty acid and sterol biosynthesis, fatty acid activation, and lipolysis. However, many droplet-associated enzymes are predicted to span a membrane two or more times, which suggests either that droplet structure is more complex than the current model posits, or that there are tightly bound membranes, particularly derived from the endoplasmic reticulum, which account for the association of several of these proteins.
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Affiliation(s)
- Joel M Goodman
- Department of Pharmacology University of Texas Southwestern Medical School Dallas TX 75390-9041, USA.
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93
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Schweiger M, Lass A, Zimmermann R, Eichmann TO, Zechner R. Neutral lipid storage disease: genetic disorders caused by mutations in adipose triglyceride lipase/PNPLA2 or CGI-58/ABHD5. Am J Physiol Endocrinol Metab 2009; 297:E289-96. [PMID: 19401457 DOI: 10.1152/ajpendo.00099.2009] [Citation(s) in RCA: 211] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neutral lipid storage disease (NLSD) is a group of autosomal recessive disorders characterized by the excessive accumulation of neutral lipids in multiple tissues. Recently, two genes, adipose triglyceride lipase (ATGL/PNPLA2) and comparative gene identification-58 (CGI-58/ABHD5), have been shown to cause NLSD. ATGL specifically hydrolyzes the first fatty acid from triacylglycerols (TG) and CGI-58/ABHD5 stimulates ATGL activity by a currently unknown mechanism. Mutations in both the ATGL and the CGI-58 genes are associated with systemic TG accumulation, yet the resulting clinical manifestations are not identical. Patients with defective ATGL function suffer from more severe myopathy (NLSDM) than patients with defective CGI-58 function. On the other hand, CGI-58 mutations are always associated with ichthyosis (NLSDI), which was not observed in patients with defective ATGL function. These observations indicate an ATGL-independent function of CGI-58. This review summarizes recent findings with the goal of relating structural variants of ATGL and CGI-58 to functional consequences in lipid metabolism.
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Affiliation(s)
- Martina Schweiger
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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94
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Schittmayer M, Birner-Gruenberger R. Functional proteomics in lipid research: Lipases, lipid droplets and lipoproteins. J Proteomics 2009; 72:1006-18. [DOI: 10.1016/j.jprot.2009.05.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 05/06/2009] [Accepted: 05/19/2009] [Indexed: 01/22/2023]
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95
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Affiliation(s)
- Yi Guo
- Gladstone Institute of Cardiovascular Disease, 1650 Owens Street, San Francisco, CA 94158, USA.
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96
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Yamaguchi T, Osumi T. Chanarin–Dorfman syndrome: Deficiency in CGI-58, a lipid droplet-bound coactivator of lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:519-23. [DOI: 10.1016/j.bbalip.2008.10.012] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 10/28/2008] [Accepted: 10/29/2008] [Indexed: 11/28/2022]
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97
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Abstract
PURPOSE OF REVIEW: This review summarizes recent research implicating Forkhead box (Fox)O1, a key transcription factor in glucose metabolism, in the regulation of hepatic lipid metabolism. Insulin dysregulation leading to hypertriglyceridemia is associated with increased hepatic VLDL secretion. FoxO1 is integrated in action with other regulatory factors in VLDL metabolism. The role of FoxO1 is defined in context of recent controversies. RECENT FINDINGS: FoxO1 regulates transcription of microsomal triglyceride transfer protein and apolipoprotein (apo)CIII involved in hepatic assembly and postsecretory catabolism of VLDL. Insulin activation of Akt leads to the phosphorylation of FoxO1 with nuclear exclusion and loss of transcriptional activity. Reduced insulin action increases FoxO1 activity and induces microsomal triglyceride transfer protein favoring VLDL assembly and induces apoCIII reducing peripheral triglyceride catabolism. This new mechanistic link between insulin resistance and VLDL overproduction and hypertriglyceridemia compounds effects of other known VLDL regulatory factors. SUMMARY: This review highlights recent advances in research of insulin regulation of hepatic VLDL metabolism. Formation of VLDL requires lipid, apoB structural protein, and microsomal triglyceride transfer protein. FoxO1 is a major factor in hepatic microsomal triglyceride ransfer protein regulation. A unifying hypothesis is presented linking regulation of the three necessary hepatic components for VLDL assembly with insulin action and insulin resistance.
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Affiliation(s)
- Janet D. Sparks
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine & Dentistry, Rochester, New York
| | - Henry H. Dong
- Rangos Research Center, Children's Hospital of Pittsburgh, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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98
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Quettier AL, Eastmond PJ. Storage oil hydrolysis during early seedling growth. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2009; 47:485-90. [PMID: 19136267 DOI: 10.1016/j.plaphy.2008.12.005] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/05/2008] [Accepted: 12/08/2008] [Indexed: 05/04/2023]
Abstract
Storage oil breakdown plays an important role in the life cycle of many plants by providing the carbon skeletons that support seedling growth immediately following germination. This metabolic process is initiated by lipases (EC: 3.1.1.3), which catalyze the hydrolysis of triacylglycerols (TAGs) to release free fatty acids and glycerol. A number of lipases have been purified to near homogeneity from seed tissues and analysed for their in vitro activities. Furthermore, several genes encoding lipases have been cloned and characterised from plants. However, only recently has data been presented to establish the molecular identity of a lipase that has been shown to be required for TAG breakdown in seeds. In this review we briefly outline the processes of TAG synthesis and breakdown. We then discuss some of the biochemical literature on seed lipases and describe the cloning and characterisation of a lipase called SUGAR-DEPENDENT1, which is required for TAG breakdown in Arabidopsis thaliana seeds.
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Affiliation(s)
- Anne-Laure Quettier
- Warwick HRI, University of Warwick, Wellesbourne, Warwickshire, United Kingdom
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99
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Lipolysis and lipid mobilization in human adipose tissue. Prog Lipid Res 2009; 48:275-97. [PMID: 19464318 DOI: 10.1016/j.plipres.2009.05.001] [Citation(s) in RCA: 518] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Revised: 05/04/2009] [Accepted: 05/08/2009] [Indexed: 01/04/2023]
Abstract
Triacylglycerol (TAG) stored in adipose tissue (AT) can be rapidly mobilized by the hydrolytic action of the three main lipases of the adipocyte. The non-esterified fatty acids (NEFA) released are used by other tissues during times of energy deprivation. Until recently hormone-sensitive lipase (HSL) was considered to be the key rate-limiting enzyme responsible for regulating TAG mobilization. A novel lipase named adipose triglyceride lipase/desnutrin (ATGL) has been identified as playing an important role in the control of fat cell lipolysis. Additionally perilipin and other proteins of the surface of the lipid droplets protecting or exposing the TAG core of the droplets to lipases are also potent regulators of lipolysis. Considerable progress has been made in understanding the mechanisms of activation of the various lipases. Lipolysis is under tight hormonal regulation. The best understood hormonal effects on AT lipolysis concern the opposing regulation by insulin and catecholamines. Heart-derived natriuretic peptides (i.e., stored in granules in the atrial and ventricle cardiomyocytes and exerting stimulating effects on diuresis and natriuresis) and numerous autocrine/paracrine factors originating from adipocytes and other cells of the stroma-vascular fraction may also participate in the regulation of lipolysis. Endocrine and autocrine/paracrine factors cooperate and lead to a fine regulation of lipolysis in adipocytes. Age, anatomical site, sex, genotype and species differences all play a part in the regulation of lipolysis. The manipulation of lipolysis has therapeutic potential in the metabolic disorders frequently associated with obesity and probably in several inborn errors of metabolism.
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100
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Bezaire V, Mairal A, Ribet C, Lefort C, Girousse A, Jocken J, Laurencikiene J, Anesia R, Rodriguez AM, Ryden M, Stenson BM, Dani C, Ailhaud G, Arner P, Langin D. Contribution of adipose triglyceride lipase and hormone-sensitive lipase to lipolysis in hMADS adipocytes. J Biol Chem 2009; 284:18282-91. [PMID: 19433586 DOI: 10.1074/jbc.m109.008631] [Citation(s) in RCA: 160] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Lipolysis is the catabolic pathway by which triglycerides are hydrolyzed into fatty acids. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) have the capacity to hydrolyze in vitro the first ester bond of triglycerides, but their respective contributions to whole cell lipolysis in human adipocytes is unclear. Here, we have investigated the roles of HSL, ATGL, and its coactivator CGI-58 in basal and forskolin-stimulated lipolysis in a human white adipocyte model, the hMADS cells. The hMADS adipocytes express the various components of fatty acid metabolism and show lipolytic capacity similar to primary cultured adipocytes. We show that lipolysis and fatty acid esterification are tightly coupled except in conditions of stimulated lipolysis. Immunocytochemistry experiments revealed that acute forskolin treatment promotes HSL translocation from the cytosol to small lipid droplets and redistribution of ATGL from the cytosol and large lipid droplets to small lipid droplets, resulting in enriched colocalization of the two lipases. HSL or ATGL overexpression resulted in increased triglyceride-specific hydrolase capacity, but only ATGL overexpression increased whole cell lipolysis. HSL silencing had no effect on basal lipolysis and only partially reduced forskolin-stimulated lipolysis. Conversely, silencing of ATGL or CGI-58 significantly reduced basal lipolysis and essentially abolished forskolin-stimulated lipolysis. Altogether, these results suggest that ATGL/CGI-58 acts independently of HSL and precedes its action in the sequential hydrolysis of triglycerides in human hMADS adipocytes.
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Affiliation(s)
- Véronic Bezaire
- INSERM U858, Laboratoire de Recherches sur les Obésités, F-31432 Toulouse, France
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