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Wigger D, Gulbins E, Kleuser B, Schumacher F. Monitoring the Sphingolipid de novo Synthesis by Stable-Isotope Labeling and Liquid Chromatography-Mass Spectrometry. Front Cell Dev Biol 2019; 7:210. [PMID: 31632963 PMCID: PMC6779703 DOI: 10.3389/fcell.2019.00210] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 09/11/2019] [Indexed: 12/11/2022] Open
Abstract
Sphingolipids are a class of lipids that share a sphingoid base backbone. They exert various effects in eukaryotes, ranging from structural roles in plasma membranes to cellular signaling. De novo sphingolipid synthesis takes place in the endoplasmic reticulum (ER), where the condensation of the activated C16 fatty acid palmitoyl-CoA and the amino acid L-serine is catalyzed by serine palmitoyltransferase (SPT). The product, 3-ketosphinganine, is then converted into more complex sphingolipids by additional ER-bound enzymes, resulting in the formation of ceramides. Since sphingolipid homeostasis is crucial to numerous cellular functions, improved assessment of sphingolipid metabolism will be key to better understanding several human diseases. To date, no assay exists capable of monitoring de novo synthesis sphingolipid in its entirety. Here, we have established a cell-free assay utilizing rat liver microsomes containing all the enzymes necessary for bottom-up synthesis of ceramides. Following lipid extraction, we were able to track the different intermediates of the sphingolipid metabolism pathway, namely 3-ketosphinganine, sphinganine, dihydroceramide, and ceramide. This was achieved by chromatographic separation of sphingolipid metabolites followed by detection of their accurate mass and characteristic fragmentations through high-resolution mass spectrometry and tandem-mass spectrometry. We were able to distinguish, unequivocally, between de novo synthesized sphingolipids and intrinsic species, inevitably present in the microsome preparations, through the addition of stable isotope-labeled palmitate-d3 and L-serine-d3. To the best of our knowledge, this is the first demonstration of a method monitoring the entirety of ER-associated sphingolipid biosynthesis. Proof-of-concept data was provided by modulating the levels of supplied cofactors (e.g., NADPH) or the addition of specific enzyme inhibitors (e.g., fumonisin B1). The presented microsomal assay may serve as a useful tool for monitoring alterations in sphingolipid de novo synthesis in cells or tissues. Additionally, our methodology may be used for metabolism studies of atypical substrates - naturally occurring or chemically tailored - as well as novel inhibitors of enzymes involved in sphingolipid de novo synthesis.
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Affiliation(s)
- Dominik Wigger
- Department of Toxicology, University of Potsdam, Nuthetal, Germany
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany.,Department of Surgery, University of Cincinnati, Cincinnati, OH, United States
| | - Burkhard Kleuser
- Department of Toxicology, University of Potsdam, Nuthetal, Germany
| | - Fabian Schumacher
- Department of Toxicology, University of Potsdam, Nuthetal, Germany.,Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
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2
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A selective inhibitor of ceramide synthase 1 reveals a novel role in fat metabolism. Nat Commun 2018; 9:3165. [PMID: 30131496 PMCID: PMC6104039 DOI: 10.1038/s41467-018-05613-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 07/17/2018] [Indexed: 02/06/2023] Open
Abstract
Specific forms of the lipid ceramide, synthesized by the ceramide synthase enzyme family, are believed to regulate metabolic physiology. Genetic mouse models have established C16 ceramide as a driver of insulin resistance in liver and adipose tissue. C18 ceramide, synthesized by ceramide synthase 1 (CerS1), is abundant in skeletal muscle and suggested to promote insulin resistance in humans. We herein describe the first isoform-specific ceramide synthase inhibitor, P053, which inhibits CerS1 with nanomolar potency. Lipidomic profiling shows that P053 is highly selective for CerS1. Daily P053 administration to mice fed a high-fat diet (HFD) increases fatty acid oxidation in skeletal muscle and impedes increases in muscle triglycerides and adiposity, but does not protect against HFD-induced insulin resistance. Our inhibitor therefore allowed us to define a role for CerS1 as an endogenous inhibitor of mitochondrial fatty acid oxidation in muscle and regulator of whole-body adiposity. Ceramides are signalling molecules that regulate several physiological functions including insulin sensitivity. Here the authors report a selective ceramide synthase 1 inhibitor that counteracts lipid accumulation within the muscle and adiposity by increasing fatty acid oxidation but without affecting insulin sensitivity in mice fed with an obesogenic diet.
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Montgomery MK, Brown SHJ, Lim XY, Fiveash CE, Osborne B, Bentley NL, Braude JP, Mitchell TW, Coster ACF, Don AS, Cooney GJ, Schmitz-Peiffer C, Turner N. Regulation of glucose homeostasis and insulin action by ceramide acyl-chain length: A beneficial role for very long-chain sphingolipid species. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1828-1839. [PMID: 27591968 DOI: 10.1016/j.bbalip.2016.08.016] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 08/18/2016] [Accepted: 08/29/2016] [Indexed: 12/13/2022]
Abstract
In a recent study, we showed that in response to high fat feeding C57BL/6, 129X1, DBA/2 and FVB/N mice all developed glucose intolerance, while BALB/c mice displayed minimal deterioration in glucose tolerance and insulin action. Lipidomic analysis of livers across these five strains has revealed marked strain-specific differences in ceramide (Cer) and sphingomyelin (SM) species with high-fat feeding; with increases in C16-C22 (long-chain) and reductions in C>22 (very long-chain) Cer and SM species observed in the four strains that developed HFD-induced glucose intolerance. Intriguingly, the opposite pattern was observed in sphingolipid species in BALB/c mice. These strain-specific changes in sphingolipid acylation closely correlated with ceramide synthase 2 (CerS2) protein content and activity, with reduced CerS2 levels/activity observed in glucose intolerant strains and increased content in BALB/c mice. Overexpression of CerS2 in primary mouse hepatocytes induced a specific elevation in very long-chain Cer, but despite the overall increase in ceramide abundance, there was a substantial improvement in insulin signal transduction, as well as decreased ER stress and gluconeogenic markers. Overall our findings suggest that very long-chain sphingolipid species exhibit a protective role against the development of glucose intolerance and hepatic insulin resistance.
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Affiliation(s)
- Magdalene K Montgomery
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Simon H J Brown
- School of Medicine, University of Wollongong, Wollongong, NSW, Australia; Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - Xin Y Lim
- Prince of Wales Clinical School, UNSW Australia, Sydney, NSW, Australia
| | - Corrine E Fiveash
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Brenna Osborne
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Nicholas L Bentley
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Jeremy P Braude
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia
| | - Todd W Mitchell
- School of Medicine, University of Wollongong, Wollongong, NSW, Australia; Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
| | - Adelle C F Coster
- School of Mathematics and Statistics, UNSW Australia, Sydney, NSW, Australia
| | - Anthony S Don
- Prince of Wales Clinical School, UNSW Australia, Sydney, NSW, Australia
| | - Gregory J Cooney
- Diabetes & Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia; St Vincent's Clinical School, UNSW Australia, Sydney, NSW, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes & Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia; St Vincent's Clinical School, UNSW Australia, Sydney, NSW, Australia
| | - Nigel Turner
- Department of Pharmacology, School of Medical Sciences, UNSW Australia, Sydney, NSW, Australia.
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Martínez-Montañés F, Schneiter R. Tools for the analysis of metabolic flux through the sphingolipid pathway. Biochimie 2016; 130:76-80. [PMID: 27208414 DOI: 10.1016/j.biochi.2016.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/13/2016] [Indexed: 01/26/2023]
Abstract
Discerning the complex regulation of the enzymatic steps necessary for sphingolipid biosynthesis is facilitated by the utilization of tracers that allow a time-resolved analysis of the pathway dynamics without affecting the metabolic flux. Different strategies have been used and new tools are continuously being developed to probe the various enzymatic conversions that occur within this complex pathway. Here, we provide a short overview of the divergent fungal and mammalian sphingolipid biosynthetic routes, and of the tracers and methods that are frequently employed to follow the flux of intermediates throughout these pathways.
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Affiliation(s)
| | - Roger Schneiter
- University of Fribourg, Department of Biology, 1700 Fribourg, Switzerland.
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Couttas TA, Kain N, Suchowerska AK, Quek LE, Turner N, Fath T, Garner B, Don AS. Loss of ceramide synthase 2 activity, necessary for myelin biosynthesis, precedes tau pathology in the cortical pathogenesis of Alzheimer's disease. Neurobiol Aging 2016; 43:89-100. [PMID: 27255818 DOI: 10.1016/j.neurobiolaging.2016.03.027] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 03/01/2016] [Accepted: 03/27/2016] [Indexed: 01/07/2023]
Abstract
The anatomical progression of neurofibrillary tangle pathology throughout Alzheimer's disease (AD) pathogenesis runs inverse to the pattern of developmental myelination, with the disease preferentially affecting thinly myelinated regions. Myelin is comprised 80% of lipids, and the prototypical myelin lipids, galactosylceramide, and sulfatide are critical for neurological function. We observed severe depletion of galactosylceramide and sulfatide in AD brain tissue, which can be traced metabolically to the loss of their biosynthetic precursor, very long chain ceramide. The synthesis of very long chain ceramides is catalyzed by ceramide synthase 2 (CERS2). We demonstrate a significant reduction in CERS2 activity as early as Braak stage I/II in temporal cortex, and Braak stage III/IV in hippocampus and frontal cortex, indicating that loss of myelin-specific ceramide synthase activity precedes neurofibrillary tangle pathology in cortical regions. These findings open a new vista on AD pathogenesis by demonstrating a defect in myelin lipid biosynthesis at the preclinical stages of the disease. We posit that, over time, this defect contributes significantly to myelin deterioration, synaptic dysfunction, and neurological decline.
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Affiliation(s)
- Timothy A Couttas
- Prince of Wales Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Nupur Kain
- Prince of Wales Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Alexandra K Suchowerska
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Lake-Ee Quek
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Nigel Turner
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Thomas Fath
- School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
| | - Brett Garner
- Illawarra Health and Medical Research Institute, School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Anthony S Don
- Prince of Wales Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia.
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Fluorescent Assays for Ceramide Synthase Activity. Methods Mol Biol 2015; 1376:23-33. [PMID: 26552672 DOI: 10.1007/978-1-4939-3170-5_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Ceramides are the central lipid metabolite of the sphingolipid family, and exert a potent influence over cell polarity, differentiation, and survival through their biophysical properties and their specific interactions with cell signaling proteins. Literature on the importance of ceramides in physiology and pathological conditions continues to grow, with ceramides having been identified as central effectors in major human pathologies such as diabetes and neurodegenerative conditions. In mammals, ceramide synthesis from a sphingoid base and a variable length fatty acid is catalyzed by a family of six ceramide synthases (CERS1-6), whose active sites exhibit differential specificity for different length fatty acids. CERS activity has traditionally been measured using radioactive substrates. More recently mass spectrometry has been used. In this chapter, we describe a fluorescent CERS assay, the results of which can be quantified using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC). Methods for quantification with either TLC or HPLC are described.
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Toop HD, Don AS, Morris JC. Synthesis and biological evaluation of analogs of AAL(S) for use as ceramide synthase 1 inhibitors. Org Biomol Chem 2015; 13:11593-6. [PMID: 26535908 DOI: 10.1039/c5ob01931a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A convergent synthesis to access hydrophobic tail analogs and head group modifications of AAL(S) is described. The analogs synthesised were evaluated for their ability to inhibit ceramide synthase 1 and for their cytotoxicity in K562 cells. Our results have identified inhibitors which are non-cytotoxic yet maintain CerS1 inhibition.
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Affiliation(s)
- Hamish D Toop
- School of Chemistry, UNSW Australia, Sydney, NSW 2052, Australia.
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