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Chong JR, Chai YL, Xing H, Herr DR, Wenk MR, Francis PT, Ballard C, Aarsland D, Silver DL, Chen CP, Cazenave‐Gassiot A, Lai MKP. Decreased DHA-containing phospholipids in the neocortex of dementia with Lewy bodies are associated with soluble Aβ 42 , phosphorylated α-synuclein, and synaptopathology. Brain Pathol 2023; 33:e13190. [PMID: 37463072 PMCID: PMC10580008 DOI: 10.1111/bpa.13190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Accepted: 07/03/2023] [Indexed: 07/20/2023] Open
Abstract
Docosahexaenoic acid (DHA) is an essential omega-3 polyunsaturated fatty acid implicated in cognitive functions by promoting synaptic protein expression. While alterations of specific DHA-containing phospholipids have been described in the neocortex of patients with Alzheimer's disease (AD), the status of these lipids in dementia with Lewy bodies (DLB), known to manifest aggregated α-synuclein-containing Lewy bodies together with variable amyloid pathology, is unclear. In this study, post-mortem samples from the parietal cortex of 25 DLB patients and 17 age-matched controls were processed for phospholipidomics analyses using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) platform. After controlling for false discovery rate, six out of the 46 identified putative DHA-phospholipid species were significantly decreased in DLB, with only one showing increase. Altered putative DHA-phospholipid species were subsequently validated with further LC-MS/MS measurements. Of the DHA-containing phospholipid (DCP) species showing decreases, five negatively correlated with soluble beta-amyloid (Aβ42) levels, whilst three also correlated with phosphorylated α-synuclein (all p < 0.05). Furthermore, five of these phospholipid species correlated with deficits of presynaptic Rab3A, postsynaptic neurogranin, or both (all p < 0.05). Finally, we found altered immunoreactivities of brain lysolipid DHA transporter, MFSD2A, and the fatty acid binding protein FABP5 in DLB parietal cortex. In summary, we report alterations of specific DCP species in DLB, as well as their associations with markers of neuropathological burden and synaptopathology. These results support the potential role of DHA perturbations in DLB as well as therapeutic targets.
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Affiliation(s)
- Joyce R. Chong
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Memory, Aging and Cognition CentreNational University Health SystemKent RidgeSingapore
| | - Yuek Ling Chai
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Memory, Aging and Cognition CentreNational University Health SystemKent RidgeSingapore
| | - Huayang Xing
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
| | - Deron R. Herr
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
| | - Markus R. Wenk
- Department of BiochemistryYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Singapore Lipidomics Incubator (SLING), Life Sciences InstituteNational University of SingaporeKent RidgeSingapore
| | | | - Clive Ballard
- College of Medicine and HealthUniversity of ExeterExeterUK
| | - Dag Aarsland
- Department of Old Age PsychiatryInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
- Centre for Age‐Related MedicineStavanger University HospitalStavangerNorway
| | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic DisordersDuke‐National University of Singapore (NUS) Medical SchoolOutramSingapore
| | - Christopher P. Chen
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Memory, Aging and Cognition CentreNational University Health SystemKent RidgeSingapore
| | - Amaury Cazenave‐Gassiot
- Department of BiochemistryYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Singapore Lipidomics Incubator (SLING), Life Sciences InstituteNational University of SingaporeKent RidgeSingapore
| | - Mitchell K. P. Lai
- Department of PharmacologyYong Loo Lin School of Medicine, National University of SingaporeKent RidgeSingapore
- Memory, Aging and Cognition CentreNational University Health SystemKent RidgeSingapore
- College of Medicine and HealthUniversity of ExeterExeterUK
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2
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Chin CF, Galam DL, Gao L, Tan BC, Wong BH, Chua GL, Loke RY, Lim YC, Wenk MR, Lim MS, Leow WQ, Goh GB, Torta F, Silver DL. Blood-derived lysophospholipid sustains hepatic phospholipids and fat storage necessary for hepatoprotection in overnutrition. J Clin Invest 2023; 133:e171267. [PMID: 37463052 PMCID: PMC10471173 DOI: 10.1172/jci171267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 07/12/2023] [Indexed: 09/02/2023] Open
Abstract
The liver has a high demand for phosphatidylcholine (PC), particularly in overnutrition, where reduced phospholipid levels have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (Mfsd2a) as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust nonalcoholic steatohepatitis-like (NASH-like) phenotype within just 2 weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFAs). Treating hepatocytes with LPCs containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid docosahexaenoic acid (DHA) promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA-containing LPCs drive hepatic lipid droplet formation, suppress lipogenesis, and sustain hepatic phospholipid pools - processes that are critical for protecting the liver from excess dietary fat.
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Affiliation(s)
- Cheen Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Dwight L.A. Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Liang Gao
- Singapore Lipidomics Incubator, Life Sciences Institute and
- Precision Medicine Translational Research Programme and Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Bryan C. Tan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Bernice H. Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Geok-Lin Chua
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Randy Y.J. Loke
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Yen Ching Lim
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Markus R. Wenk
- Singapore Lipidomics Incubator, Life Sciences Institute and
- Precision Medicine Translational Research Programme and Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Miao-Shan Lim
- Department of Gastroenterology and Hepatology, Singapore General Hospital, Singapore
| | - Wei-Qiang Leow
- Department of Anatomical Pathology, Singapore General Hospital, and
| | - George B.B. Goh
- Department of Gastroenterology and Hepatology, Singapore General Hospital, Singapore
- Medicine Academic Clinical Program, Duke-NUS Medical School, Singapore
| | - Federico Torta
- Singapore Lipidomics Incubator, Life Sciences Institute and
- Precision Medicine Translational Research Programme and Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
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3
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Loke RYJ, Chin CF, Liang G, Wong BH, Galam DLA, Tan BC, Chua GL, Minegishi S, Morisawa N, Sidorov I, Heijs B, Titze J, Wenk MR, Torta F, Silver DL. Mfsd2a-mediated lysolipid transport is important for renal recovery after acute kidney injury. J Lipid Res 2023; 64:100416. [PMID: 37467896 PMCID: PMC10424216 DOI: 10.1016/j.jlr.2023.100416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Revised: 07/08/2023] [Accepted: 07/10/2023] [Indexed: 07/21/2023] Open
Abstract
Acute kidney injury (AKI) is a global public health concern with high mortality and morbidity. In ischemic-reperfusion injury (IRI), a main cause of AKI, the brush border membrane of S3 proximal tubules (PT) is lost to the tubular lumen. How injured tubules reconstitute lost membrane lipids during renal recovery is not known. Here, we identified Mfsd2a, a sodium-dependent lysophosphatidylcholine (LPC) transporter, to be expressed specifically in the basolateral membrane of S3 PT. Using an in vivo activity probe for Mfsd2a, transport activity was found to be specific to the S3 PT. Mice with haploinsufficiency of Mfsd2a exhibited delayed recovery of renal function after acute IRI, with depressed urine osmolality and elevated levels of histological markers of damage, fibrosis, and inflammation, findings corroborated by transcriptomic analysis. Lipidomics revealed a deficiency in docosahexaenoic acid (DHA) containing phospholipids in Mfsd2a haploinsufficiency. Treatment of Mfsd2a haploinsufficient mice with LPC-DHA improved renal function and reduced markers of injury, fibrosis, and inflammation. Additionally, LPC-DHA treatment restored S3 brush border membrane architecture and normalized DHA-containing phospholipid content. These findings indicate that Mfsd2a-mediated transport of LPC-DHA is limiting for renal recovery after AKI and suggest that LPC-DHA could be a promising dietary supplement for improving recovery following AKI.
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Affiliation(s)
- Randy Y J Loke
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Cheen Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Gao Liang
- Singapore Lipidomics Incubator, Life Sciences Institute, NUS, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, NUS, Singapore
| | - Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Dwight L A Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Bryan C Tan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Geok-Lin Chua
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Shintaro Minegishi
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Norihiko Morisawa
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Iulia Sidorov
- Center of Proteomics and Metabolomics, Leiden University Medical Center, Leiden, the Netherlands; The Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), Leiden University Medical Center, Leiden, the Netherlands
| | - Bram Heijs
- Center of Proteomics and Metabolomics, Leiden University Medical Center, Leiden, the Netherlands; The Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), Leiden University Medical Center, Leiden, the Netherlands
| | - Jens Titze
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore
| | - Markus R Wenk
- Singapore Lipidomics Incubator, Life Sciences Institute, NUS, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, NUS, Singapore
| | - Federico Torta
- Singapore Lipidomics Incubator, Life Sciences Institute, NUS, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, NUS, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore (NUS) Medical School, Singapore.
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4
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Kuk ACY, Silver DL. The cellular supply-side economics for phospholipids. Cell Metab 2023; 35:909-911. [PMID: 37285806 DOI: 10.1016/j.cmet.2023.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 06/09/2023]
Abstract
Choline is an essential nutrient, but how cells acquire it was not known. Two studies by Kenny et al. and Tsuchiya et al. identified the plasma membrane proteins FLVCR1 and FLVCR2 to be the bona fide choline transporters mediating choline uptake for de novo synthesis of phospholipids in all cells.
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Affiliation(s)
- Alvin C Y Kuk
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore 169857, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore 169857, Singapore.
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5
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Sengottuvel V, Hota M, Oh J, Galam DL, Wong BH, Wenk MR, Ghosh S, Torta F, Silver DL. Deficiency in the omega-3 lysolipid transporter Mfsd2a leads to aberrant oligodendrocyte lineage development and hypomyelination. J Clin Invest 2023:164118. [PMID: 37104036 DOI: 10.1172/jci164118] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023] Open
Abstract
Patients with Autosomal Recessive Microcephaly 15 caused by deficiency in the sodium-dependent lysophosphatidylcholine (LPC) transporter Major Facilitator Superfamily Domain containing 2a (Mfsd2a) present with both microcephaly and hypomyelination, suggesting an important role of LPC uptake by oligodendrocytes in the process of myelination. Here, we demonstrate that Mfsd2a is specifically expressed in oligodendrocyte precursor cells (OPC) and is critical for oligodendrocyte development. Single cell sequencing of the oligodendrocyte lineage revealed that OPCs from OPC-specific Mfsd2a KO mice (2aOKO) underwent precocious differentiation into immature oligodendrocytes (iOLs) and impaired maturation into myelinating oligodendrocytes, correlating with postnatal brain hypomyelination. 2aOKO mice did not exhibit microcephaly, consistent with microcephaly being consequential to absence of LPC uptake at the blood-brain barrier and not from deficiency in OPCs. Lipidomic analysis showed that OPCs and iOLs from 2aOKO mice had significantly decreased phospholipids containing omega-3 fatty acids with an opposite increase in unsaturated fatty acids, that latter being products of de novo synthesis governed by Srebp-1. RNA sequencing indicated activation of the Srebp-1 pathway and defective expression of regulators of oligodendrocyte development. Taken together, these findings indicate that the transport of LPCs by Mfsd2a in OPCs is important for maintaining OPC cell state to regulate postnatal brain myelination.
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Affiliation(s)
- Vetrivel Sengottuvel
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Monalisa Hota
- Centre for Computational Biology, Duke-NUS Medical School, Singapore, Singapore
| | - Jeongah Oh
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - Dwight L Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Markus R Wenk
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - Sujoy Ghosh
- Centre for Computational Biology, Duke-NUS Medical School, Singapore, Singapore
| | - Federico Torta
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
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6
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Chua GL, Tan BC, Loke RYJ, He M, Chin CF, Wong BH, Kuk ACY, Ding M, Wenk MR, Guan L, Torta F, Silver DL. Mfsd2a utilizes a flippase mechanism to mediate omega-3 fatty acid lysolipid transport. Proc Natl Acad Sci U S A 2023; 120:e2215290120. [PMID: 36848557 PMCID: PMC10013850 DOI: 10.1073/pnas.2215290120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 01/27/2023] [Indexed: 03/01/2023] Open
Abstract
Major Facilitator Superfamily Domain containing 2a (Mfsd2a) is a sodium-dependent lysophosphatidylcholine (LPC) transporter expressed at the blood-brain barrier that constitutes the main pathway by which the brain obtains omega-3 fatty acids, such as docosahexanoic acid. Mfsd2a deficiency in humans results in severe microcephaly, underscoring the importance of LPC transport by Mfsd2a for brain development. Biochemical studies and recent cryo-electron microscopy (cryo-EM) structures of Mfsd2a bound to LPC suggest that Mfsd2a transports LPC via an alternating access mechanism between outward-facing and inward-facing conformational states in which the LPC inverts during transport between the outer and inner leaflet of a membrane. However, direct biochemical evidence of flippase activity by Mfsd2a has not been demonstrated and it is not understood how Mfsd2a could invert LPC between the outer and inner leaflet of the membrane in a sodium-dependent manner. Here, we established a unique in vitro assay using recombinant Mfsd2a reconstituted in liposomes that exploits the ability of Mfsd2a to transport lysophosphatidylserine (LPS) coupled with a small molecule LPS binding fluorophore that allowed for monitoring of directional flipping of the LPS headgroup from the outer to the inner liposome membrane. Using this assay, we demonstrate that Mfsd2a flips LPS from the outer to the inner leaflet of a membrane bilayer in a sodium-dependent manner. Furthermore, using cryo-EM structures as guides together with mutagenesis and a cell-based transport assay, we identify amino acid residues important for Mfsd2a activity that likely constitute substrate interaction domains. These studies provide direct biochemical evidence that Mfsd2a functions as a lysolipid flippase.
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Affiliation(s)
- Geok-Lin Chua
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Bryan C. Tan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Randy Y. J. Loke
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Menglan He
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Cheen-Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Bernice H. Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Alvin C. Y. Kuk
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
| | - Mei Ding
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore117456, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117596, Singapore
| | - Markus R. Wenk
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore117456, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117596, Singapore
| | - Lan Guan
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX79430
| | - Federico Torta
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore117456, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore117596, Singapore
| | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore169857, Singapore
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7
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Zheng X, Ho QWC, Chua M, Stelmashenko O, Yeo XY, Muralidharan S, Torta F, Chew EGY, Lian MM, Foo JN, Jung S, Wong SH, Tan NS, Tong N, Rutter GA, Wenk MR, Silver DL, Berggren PO, Ali Y. Destabilization of β Cell FIT2 by saturated fatty acids alter lipid droplet numbers and contribute to ER stress and diabetes. Proc Natl Acad Sci U S A 2022; 119:e2113074119. [PMID: 35254894 PMCID: PMC8931238 DOI: 10.1073/pnas.2113074119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 01/29/2022] [Indexed: 02/05/2023] Open
Abstract
SignificanceWith obesity on the rise, there is a growing appreciation for intracellular lipid droplet (LD) regulation. Here, we show how saturated fatty acids (SFAs) reduce fat storage-inducing transmembrane protein 2 (FIT2)-facilitated, pancreatic β cell LD biogenesis, which in turn induces β cell dysfunction and death, leading to diabetes. This mechanism involves direct acylation of FIT2 cysteine residues, which then marks the FIT2 protein for endoplasmic reticulum (ER)-associated degradation. Loss of β cell FIT2 and LDs reduces insulin secretion, increases intracellular ceramides, stimulates ER stress, and exacerbates diet-induced diabetes in mice. While palmitate and stearate degrade FIT2, unsaturated fatty acids such as palmitoleate and oleate do not, results of which extend to nutrition and diabetes.
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Affiliation(s)
- Xiaofeng Zheng
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Singapore Eye Research Institute, Singapore General Hospital, S168751, Singapore
- Department of Endocrinology and Metabolism, Center for Diabetes and Metabolism Research, West China Hospital, Sichuan University, Chengdu 610041, People’s Republic of China
| | - Qing Wei Calvin Ho
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
| | - Minni Chua
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
| | - Olga Stelmashenko
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Singapore Eye Research Institute, Singapore General Hospital, S168751, Singapore
| | - Xin Yi Yeo
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, S138667, Singapore
- Department of Psychological Medicine, Yong Loo Lin School of Medicine, National University of Singapore, S119228, Singapore
| | - Sneha Muralidharan
- Singapore Lipidomics Incubator, Department of Medicine, National University of Singapore, S117456, Singapore
| | - Federico Torta
- Singapore Lipidomics Incubator, Department of Biochemistry, Life Sciences Institute and Yong Loo Lin School of Medicine, National University of Singapore, S117456, Singapore
| | - Elaine Guo Yan Chew
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Human Genetics, A*STAR, Genome Institute of Singapore, S138672, Singapore
| | - Michelle Mulan Lian
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Human Genetics, A*STAR, Genome Institute of Singapore, S138672, Singapore
| | - Jia Nee Foo
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Human Genetics, A*STAR, Genome Institute of Singapore, S138672, Singapore
| | - Sangyong Jung
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, S138667, Singapore
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, S117593, Singapore
| | - Sunny Hei Wong
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
| | - Nguan Soon Tan
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- School of Biological Sciences, Nanyang Technological University Singapore, S637551, Singapore
| | - Nanwei Tong
- Department of Endocrinology and Metabolism, Center for Diabetes and Metabolism Research, West China Hospital, Sichuan University, Chengdu 610041, People’s Republic of China
| | - Guy A. Rutter
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology, and Metabolism, Department of Metabolism, Digestion, and Reproduction, Imperial College London, London SW7 2AZ, United Kingdom
- Le Centre de recherche du Centre hospitalier de l’Université de Montréal (CR-CHUM), University of Montréal, Montréal, QC H2X 0A9, Canada
| | - Markus R. Wenk
- Singapore Lipidomics Incubator, Department of Biochemistry, Life Sciences Institute and Yong Loo Lin School of Medicine, National University of Singapore, S117456, Singapore
| | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke–National University of Singapore Graduate Medical School, S169857, Singapore
| | - Per-Olof Berggren
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Singapore Eye Research Institute, Singapore General Hospital, S168751, Singapore
- Department of Endocrinology and Metabolism, Center for Diabetes and Metabolism Research, West China Hospital, Sichuan University, Chengdu 610041, People’s Republic of China
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Yusuf Ali
- Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, S308232, Singapore
- Singapore Eye Research Institute, Singapore General Hospital, S168751, Singapore
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8
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Wong BH, Mei D, Chua GL, Galam DL, Wenk MR, Torta F, Silver DL. The lipid transporter Mfsd2a maintains pulmonary surfactant homeostasis. J Biol Chem 2022; 298:101709. [PMID: 35150739 PMCID: PMC8914330 DOI: 10.1016/j.jbc.2022.101709] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/02/2022] [Accepted: 02/03/2022] [Indexed: 11/18/2022] Open
Abstract
Pulmonary surfactant is a lipoprotein complex essential for lung function, and insufficiency or altered surfactant composition is associated with major lung diseases, such as acute respiratory distress syndromes, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease. Pulmonary surfactant is primarily composed of phosphatidylcholine (PC) in complex with specialized surfactant proteins and secreted by alveolar type 2 (AT2) cells. Surfactant homeostasis on the alveolar surface is balanced by the rates of synthesis and secretion with reuptake and recycling by AT2 cells, with some degradation by pulmonary macrophages and loss up the bronchial tree. However, whether phospholipid (PL) transporters exist in AT2 cells to mediate reuptake of surfactant PL remains to be identified. Here, we demonstrate that major facilitator superfamily domain containing 2a (Mfsd2a), a sodium-dependent lysophosphatidylcholine (LPC) transporter, is expressed at the apical surface of AT2 cells. A mouse model with inducible AT2 cell–specific deficiency of Mfsd2a exhibited AT2 cell hypertrophy with reduced total surfactant PL levels because of reductions in the most abundant surfactants, PC containing dipalmitic acid, and PC species containing the omega-3 fatty acid docosahexaenoic acid. These changes in surfactant levels and composition were mirrored by similar changes in the AT2 cell lipidome. Mechanistically, direct tracheal instillation of fluorescent LPC and PC probes indicated that Mfsd2a mediates the uptake of LPC generated by pulmonary phospholipase activity in the alveolar space. These studies reveal that Mfsd2a-mediated LPC uptake is quantitatively important in maintaining surfactant homeostasis and identify this lipid transporter as a physiological component of surfactant recycling.
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Affiliation(s)
- Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Ding Mei
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Geok Lin Chua
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Dwight L Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Markus R Wenk
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Federico Torta
- Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore, Singapore; Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore.
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9
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Cater RJ, Chua GL, Erramilli SK, Keener JE, Choy BC, Tokarz P, Chin CF, Quek DQY, Kloss B, Pepe JG, Parisi G, Wong BH, Clarke OB, Marty MT, Kossiakoff AA, Khelashvili G, Silver DL, Mancia F. Structural basis of omega-3 fatty acid transport across the blood-brain barrier. Nature 2021; 595:315-319. [PMID: 34135507 PMCID: PMC8266758 DOI: 10.1038/s41586-021-03650-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 05/17/2021] [Indexed: 02/05/2023]
Abstract
Docosahexaenoic acid is an omega-3 fatty acid that is essential for neurological development and function, and it is supplied to the brain and eyes predominantly from dietary sources1-6. This nutrient is transported across the blood-brain and blood-retina barriers in the form of lysophosphatidylcholine by major facilitator superfamily domain containing 2A (MFSD2A) in a Na+-dependent manner7,8. Here we present the structure of MFSD2A determined using single-particle cryo-electron microscopy, which reveals twelve transmembrane helices that are separated into two pseudosymmetric domains. The transporter is in an inward-facing conformation and features a large amphipathic cavity that contains the Na+-binding site and a bound lysolipid substrate, which we confirmed using native mass spectrometry. Together with our functional analyses and molecular dynamics simulations, this structure reveals details of how MFSD2A interacts with substrates and how Na+-dependent conformational changes allow for the release of these substrates into the membrane through a lateral gate. Our work provides insights into the molecular mechanism by which this atypical major facility superfamily transporter mediates the uptake of lysolipids into the brain, and has the potential to aid in the delivery of neurotherapeutic agents.
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Affiliation(s)
- Rosemary J Cater
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Geok Lin Chua
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Satchal K Erramilli
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - James E Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Brendon C Choy
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Piotr Tokarz
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Cheen Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Debra Q Y Quek
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Brian Kloss
- Center on Membrane Protein Production and Analysis, New York Structural Biology Center, New York, NY, USA
| | - Joseph G Pepe
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Giacomo Parisi
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
| | - Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Oliver B Clarke
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA
- Department of Anesthesiology, Columbia University Irving Medical Center, New York, NY, USA
| | - Michael T Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - George Khelashvili
- Department of Physiology and Biophysics, Weill Cornell Medical College, Cornell University, New York, NY, USA.
- Institute for Computational Biomedicine, Weill Cornell Medical College, Cornell University, New York, NY, USA.
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore.
| | - Filippo Mancia
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, USA.
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10
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Park S, Woon QTS, Er JC, Wong BH, Liu X, Kang N, Barathi VA, Silver DL, Chang Y. Cover Feature: Application of Neuron‐Selective Fluorescent Probe, NeuA, To Identify Mouse Retinal Degeneration (ChemBioChem 11/2021). Chembiochem 2021. [DOI: 10.1002/cbic.202100206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sung‐Jin Park
- Singapore Bioimaging Consortium Agency for Science Technology and Research Singapore 138667 Republic of Singapore
| | - Queenie Tan Shu Woon
- Institute of Molecular and Cell Biology Agency for Science Technology and Research Singapore 169856 Republic of Singapore
| | - Jun Cheng Er
- Singapore Bioimaging Consortium Agency for Science Technology and Research Singapore 138667 Republic of Singapore
| | - Bernice H. Wong
- Program in Cardiovascular and Metabolic Disorders Duke-NUS Medical School Singapore 169857 Republic of Singapore
| | - Xiao Liu
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Nam‐Young Kang
- Singapore Bioimaging Consortium Agency for Science Technology and Research Singapore 138667 Republic of Singapore
- Department of Creative IT Engineering Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
| | - Veluchamy A. Barathi
- Singapore Eye Research Institute Singapore 169856 Republic of Singapore
- Eye-ACP, Duke-NUS Graduate Medical School Singapore 169857 Republic of Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine National University of Singapore Singapore 119228 Republic of Singapore
| | - David L. Silver
- Program in Cardiovascular and Metabolic Disorders Duke-NUS Medical School Singapore 169857 Republic of Singapore
| | - Young‐Tae Chang
- Singapore Bioimaging Consortium Agency for Science Technology and Research Singapore 138667 Republic of Singapore
- Department of Chemistry Pohang University of Science and Technology (POSTECH) Pohang 37673 Republic of Korea
- Center for Self-assembly and Complexity Institute for Basic Science (IBS) Pohang 37673 Republic of Korea
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11
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Park SJ, Woon QTS, Er JC, Wong BH, Liu X, Kang NY, Barathi VA, Silver DL, Chang YT. Application of Neuron-Selective Fluorescent Probe, NeuA, To Identify Mouse Retinal Degeneration. Chembiochem 2021; 22:1915-1919. [PMID: 33617145 DOI: 10.1002/cbic.202100011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Revised: 02/20/2021] [Indexed: 11/09/2022]
Abstract
The retina is part of the central nerve system (CNS) and has various interneurons and sensory neurons such as photoreceptor cells. Retinitis pigmentosa (RP) is an inherited condition that is characterized by photoreceptor degeneration. Herein, we developed a fluorescent probe-NeuA-for detecting retinal neuronal cells and applied NeuA to discriminate between healthy and RP retinas. The staining pattern of NeuA in the retinas of healthy and RP mouse models was examined in vitro, ex vivo and in vivo using confocal microscopy, the fluorescent fundus microscopy and optical coherent tomography (OCT). NeuA strongly stained the outer segment layer of photoreceptor cells and some bipolar cells in the healthy retina, but there was only weak staining in the photoreceptor degenerated retinas. Therefore, NeuA probe can be used as the detecting RP tools in the preclinical conditions.
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Affiliation(s)
- Sung-Jin Park
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore, 138667, Republic of Singapore
| | - Queenie Tan Shu Woon
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore, 169856, Republic of Singapore
| | - Jun Cheng Er
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore, 138667, Republic of Singapore
| | - Bernice H Wong
- Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, 169857, Republic of Singapore
| | - Xiao Liu
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Nam-Young Kang
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore, 138667, Republic of Singapore.,Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Veluchamy A Barathi
- Singapore Eye Research Institute, Singapore, 169856, Republic of Singapore.,Eye-ACP, Duke-NUS Graduate Medical School, Singapore, 169857, Republic of Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Republic of Singapore
| | - David L Silver
- Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, 169857, Republic of Singapore
| | - Young-Tae Chang
- Singapore Bioimaging Consortium, Agency for Science, Technology and Research, Singapore, 138667, Republic of Singapore.,Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.,Center for Self-assembly and Complexity, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
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12
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Mäe MA, He L, Nordling S, Vazquez-Liebanas E, Nahar K, Jung B, Li X, Tan BC, Foo JC, Cazenave-Gassiot A, Wenk MR, Zarb Y, Lavina B, Quaggin SE, Jeansson M, Gu C, Silver DL, Vanlandewijck M, Butcher EC, Keller A, Betsholtz C. Single-Cell Analysis of Blood-Brain Barrier Response to Pericyte Loss. Circ Res 2021; 128:e46-e62. [PMID: 33375813 PMCID: PMC10858745 DOI: 10.1161/circresaha.120.317473] [Citation(s) in RCA: 79] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RATIONALE Pericytes are capillary mural cells playing a role in stabilizing newly formed blood vessels during development and tissue repair. Loss of pericytes has been described in several brain disorders, and genetically induced pericyte deficiency in the brain leads to increased macromolecular leakage across the blood-brain barrier (BBB). However, the molecular details of the endothelial response to pericyte deficiency remain elusive. OBJECTIVE To map the transcriptional changes in brain endothelial cells resulting from lack of pericyte contact at single-cell level and to correlate them with regional heterogeneities in BBB function and vascular phenotype. METHODS AND RESULTS We reveal transcriptional, morphological, and functional consequences of pericyte absence for brain endothelial cells using a combination of methodologies, including single-cell RNA sequencing, tracer analyses, and immunofluorescent detection of protein expression in pericyte-deficient adult Pdgfbret/ret mice. We find that endothelial cells without pericyte contact retain a general BBB-specific gene expression profile, however, they acquire a venous-shifted molecular pattern and become transformed regarding the expression of numerous growth factors and regulatory proteins. Adult Pdgfbret/ret brains display ongoing angiogenic sprouting without concomitant cell proliferation providing unique insights into the endothelial tip cell transcriptome. We also reveal heterogeneous modes of pericyte-deficient BBB impairment, where hotspot leakage sites display arteriolar-shifted identity and pinpoint putative BBB regulators. By testing the causal involvement of some of these using reverse genetics, we uncover a reinforcing role for angiopoietin 2 at the BBB. CONCLUSIONS By elucidating the complexity of endothelial response to pericyte deficiency at cellular resolution, our study provides insight into the importance of brain pericytes for endothelial arterio-venous zonation, angiogenic quiescence, and a limited set of BBB functions. The BBB-reinforcing role of ANGPT2 (angiopoietin 2) is paradoxical given its wider role as TIE2 (TEK receptor tyrosine kinase) receptor antagonist and may suggest a unique and context-dependent function of ANGPT2 in the brain.
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Affiliation(s)
- Maarja A. Mäe
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
| | - Liqun He
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Neurosurgery, Tianjin Medical University General Hospital, Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin 300052, China
| | - Sofia Nordling
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Pathology, Stanford University School of Medicine, Stanford CA 94305, USA
| | - Elisa Vazquez-Liebanas
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
| | - Khayrun Nahar
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
| | - Bongnam Jung
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Present address: Harvard Medical School, Department of Surgery, Boston, MA 02115, USA
| | - Xidan Li
- Integrated Cardio Metabolic Center (ICMC) and Department of Medicine Huddinge, Karolinska Institutet Campus Flemingsberg, Blickagången 16, SE-141 57 Huddinge, Sweden
| | - Bryan C. Tan
- Duke-NUS Medical School, 8 College Road, Singapore 169857
| | - Juat Chin Foo
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore
| | - Amaury Cazenave-Gassiot
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore
- Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore
| | - Markus R. Wenk
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore
- Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore
| | - Yvette Zarb
- Neurosurgery, Clinical Neuroscience Centrum, Zürich University Hospital, Zürich University, Frauenklinikstrasse 10, CH-8091
| | - Barbara Lavina
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
| | - Susan E. Quaggin
- Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, United States
| | - Marie Jeansson
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Integrated Cardio Metabolic Center (ICMC) and Department of Medicine Huddinge, Karolinska Institutet Campus Flemingsberg, Blickagången 16, SE-141 57 Huddinge, Sweden
| | - Chengua Gu
- Neurobiology, Harvard Medical School, Boston
| | | | - Michael Vanlandewijck
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Integrated Cardio Metabolic Center (ICMC) and Department of Medicine Huddinge, Karolinska Institutet Campus Flemingsberg, Blickagången 16, SE-141 57 Huddinge, Sweden
| | - Eugene C. Butcher
- Pathology, Stanford University School of Medicine, Stanford CA 94305, USA
| | - Annika Keller
- Neurosurgery, Clinical Neuroscience Centrum, Zürich University Hospital, Zürich University, Frauenklinikstrasse 10, CH-8091
| | - Christer Betsholtz
- Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, Dag Hammarskjölds väg 20, SE-751 85 Uppsala, Sweden
- Integrated Cardio Metabolic Center (ICMC) and Department of Medicine Huddinge, Karolinska Institutet Campus Flemingsberg, Blickagången 16, SE-141 57 Huddinge, Sweden
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13
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Abstract
Lipids and essential fatty acids are required for normal brain development and continued photoreceptor membrane biogenesis for the maintenance of vision. The blood-brain barrier and blood-eye barriers prohibit the free diffusion of solutes into the brain and eye so that transporter-mediated uptake predominates at these barriers. The major facilitator superfamily of transporters constitutes one of the largest families of facilitative transporters across all domains of life. A unique family member, major facilitator superfamily domain containing 2a (Mfsd2a) is a lysophosphatidylcholine (LPC) transporter expressed at the blood-brain and blood-retinal barriers and demonstrated to be the major pathway for brain and eye accretion of docosahexaenoic acid (DHA) as an LPC. In addition to LPC-DHA, Mfsd2a can transport other LPCs containing mono- and polyunsaturated fatty acids. Mfsd2a deficiency in mouse and humans results in severe microcephaly, underscoring the importance of LPC transport in brain development. Beyond its role in brain development, LPC-DHA uptake in the brain and eye negatively regulates de novo lipogenesis. This review focuses on the current understanding of the physiological roles of Mfsd2a in the brain and eye and the proposed transport mechanism of Mfsd2a.
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Affiliation(s)
- Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore.
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14
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Piccirillo AR, Hyzny EJ, Beppu LY, Menk AV, Wallace CT, Hawse WF, Buechel HM, Wong BH, Foo JC, Cazenave-Gassiot A, Wenk MR, Delgoffe GM, Watkins SC, Silver DL, D'Cruz LM. The Lysophosphatidylcholine Transporter MFSD2A Is Essential for CD8 + Memory T Cell Maintenance and Secondary Response to Infection. J Immunol 2019; 203:117-126. [PMID: 31127034 DOI: 10.4049/jimmunol.1801585] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 04/29/2019] [Indexed: 01/09/2023]
Abstract
Access to nutrients is critical for an effective T cell immune response to infection. Although transporters for sugars and amino acids have previously been described in the context of the CD8+ T cell immune response, the active transport of exogenous fatty acids has remained enigmatic. In this study, we discovered that the sodium-dependent lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (MFSD2A) is upregulated on activated CD8+ T cells and is required for memory T cell maintenance. MFSD2A deficiency in mice resulted in decreased import of LPC esterified to long chain fatty acids into activated CD8+ T cells, and MFSD2A-deficient cells are at a competitive disadvantage resulting in reduced memory T cell formation and maintenance and reduced response to secondary infection. Mechanistically, import of LPCs was required to maintain T cell homeostatic turnover, which when lost resulted in a decreased memory T cell pool and thus a reduced secondary response to repeat infection.
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Affiliation(s)
- Ann R Piccirillo
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213
| | - Eric J Hyzny
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213
| | - Lisa Y Beppu
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213
| | - Ashley V Menk
- Tumor Microenvironment Center, UPMC Hillman Cancer Center, Pittsburgh, PA 15232
| | - Callen T Wallace
- Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA 15213
| | - William F Hawse
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213
| | - Heather M Buechel
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213
| | - Bernice H Wong
- Signature Research Program in Cardiovascular and Metabolic Diseases, Duke-National University of Singapore Graduate Medical School, Singapore 159857, Singapore; and
| | - Juat Chin Foo
- Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore
| | | | - Markus R Wenk
- Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore
| | - Greg M Delgoffe
- Tumor Microenvironment Center, UPMC Hillman Cancer Center, Pittsburgh, PA 15232
| | - Simon C Watkins
- Center for Biologic Imaging, University of Pittsburgh, Pittsburgh, PA 15213
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Diseases, Duke-National University of Singapore Graduate Medical School, Singapore 159857, Singapore; and
| | - Louise M D'Cruz
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213;
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15
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Chan JP, Wong BH, Chin CF, Galam DLA, Foo JC, Wong LC, Ghosh S, Wenk MR, Cazenave-Gassiot A, Silver DL. The lysolipid transporter Mfsd2a regulates lipogenesis in the developing brain. PLoS Biol 2018; 16:e2006443. [PMID: 30074985 PMCID: PMC6093704 DOI: 10.1371/journal.pbio.2006443] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 08/15/2018] [Accepted: 07/11/2018] [Indexed: 01/12/2023] Open
Abstract
Brain development requires a massive increase in brain lipogenesis and accretion of the essential omega-3 fatty acid docosahexaenoic acid (DHA). Brain acquisition of DHA is primarily mediated by the transporter Major Facilitator Superfamily Domain containing 2a (Mfsd2a) expressed in the endothelium of the blood-brain barrier (BBB) and other abundant cell types within the brain. Mfsd2a transports DHA and other polyunsaturated fatty acids (PUFAs) esterified to lysophosphatidylcholine (LPC-DHA). However, the function of Mfsd2a and DHA in brain development is incompletely understood. Here, we demonstrate, using vascular endothelial-specific and inducible vascular endothelial-specific deletion of Mfsd2a in mice, that Mfsd2a is uniquely required postnatally at the BBB for normal brain growth and DHA accretion, with DHA deficiency preceding the onset of microcephaly. In Mfsd2a-deficient mouse models, a lipidomic signature was identified that is indicative of increased de novo lipogenesis of PUFAs. Gene expression profiling analysis of these DHA-deficient brains indicated that sterol regulatory-element binding protein (Srebp)-1 and Srebp-2 pathways were highly elevated. Mechanistically, LPC-DHA treatment of primary neural stem cells down-regulated Srebp processing and activation in a Mfsd2a-dependent fashion, resulting in profound effects on phospholipid membrane saturation. In addition, Srebp regulated the expression of Mfsd2a. These data identify LPC-DHA transported by Mfsd2a as a physiological regulator of membrane phospholipid saturation acting in a feedback loop on Srebp activity during brain development. The brain is the most lipid-rich organ in the body. Brain development involves a tremendous increase in the synthesis and accretion of fatty acids. De novo synthesis of fatty acids is mediated by Srebp transcription factors, whereas acquisition of essential fatty acids via uptake of plasma-derived lysophosphatidylcholine containing the essential omega-3 fatty acid docosahexaenoic acid (LPC-DHA) is mediated by the transporter Mfsd2a in the cells that line the blood vessels in the brain. The function of Mfsd2a and DHA in brain development is incompletely understood. Our study determined that Mfsd2a is required at the blood-brain barrier for brain development and accretion of DHA after birth in mice. Moreover, we determined that a major function of DHA in the brain is to negatively regulate Srebp activation, resulting in profound effects on membrane phospholipid composition. These findings reveal that LPC-DHA transported by Mfsd2a plays a physiological role in both brain growth and in maintaining plasma membrane phospholipid composition during brain development.
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Affiliation(s)
- Jia Pei Chan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Bernice H. Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Cheen Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Dwight L. A. Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Juat Chin Foo
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - Loo Chin Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Sujoy Ghosh
- Centre for Computational Biology, Duke-NUS Medical School, Singapore, Singapore
| | - Markus R. Wenk
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | | | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
- * E-mail:
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16
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Harel T, Quek DQY, Wong BH, Cazenave-Gassiot A, Wenk MR, Fan H, Berger I, Shmueli D, Shaag A, Silver DL, Elpeleg O, Edvardson S. Homozygous mutation in MFSD2A, encoding a lysolipid transporter for docosahexanoic acid, is associated with microcephaly and hypomyelination. Neurogenetics 2018; 19:227-235. [DOI: 10.1007/s10048-018-0556-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 07/09/2018] [Indexed: 01/05/2023]
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17
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Agrawal M, Yeo CR, Shabbir A, Chhay V, Silver DL, Magkos F, Vidal-Puig A, Toh SA. Fat storage-inducing transmembrane protein 2 (FIT2) is less abundant in type 2 diabetes, and regulates triglyceride accumulation and insulin sensitivity in adipocytes. FASEB J 2018; 33:430-440. [PMID: 30020828 DOI: 10.1096/fj.201701321rr] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Fat storage-inducing transmembrane protein 2 (FIT2) aids in partitioning of cellular triacylglycerol into lipid droplets. A genome-wide association study reported FITM2-R3H domain containing like-HNF4A locus to be associated with type 2 diabetes (T2DM) in East Asian populations. Mice with adipose tissue (AT)-specific FIT2 knockout exhibited lipodystrophic features, with reduced AT mass, insulin resistance, and greater inflammation in AT when fed a high-fat diet. The role of FIT2 in regulating human adipocyte function is not known. Here, we found FIT2 protein abundance is lower in subcutaneous and omental AT obtained from patients with T2DM compared with nondiabetic control subjects. Partial loss of FIT2 protein in primary human adipocytes attenuated their lipid storage capacity and induced insulin resistance. After palmitate treatment, triacylglycerol accumulation, insulin-induced Akt (Ser-473) phosphorylation, and insulin-stimulated glucose uptake were significantly reduced in FIT2 knockdown adipocytes compared with control cells. Gene expression of proinflammatory cytokines IL-18 and IL-6 and phosphorylation of the endoplasmic reticulum stress marker inositol-requiring enzyme 1α were greater in FIT2 knockdown adipocytes than in control cells. Our results show for the first time that FIT2 is associated with T2DM in humans and plays an integral role in maintaining metabolically healthy AT function.-Agrawal, M., Yeo, C. R., Shabbir, A., Chhay, V., Silver, D. L., Magkos, F., Vidal-Puig, A., Toh, S.-A. Fat storage-inducing transmembrane protein 2 (FIT2) is less abundant in type 2 diabetes, and regulates triglyceride accumulation and insulin sensitivity in adipocytes.
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Affiliation(s)
- Madhur Agrawal
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, Kentucky, USA
| | - Chia Rou Yeo
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Asim Shabbir
- Department of Surgery, National University Hospital, Singapore
| | - Vanna Chhay
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Medical School, Singapore
| | - Faidon Magkos
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Singapore Institute of Clinical Sciences (SICS), Agency for Science, Technology, and Research (A*STAR), Singapore
| | - Antonio Vidal-Puig
- Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom.,Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Sue-Anne Toh
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Department of Medicine, National University Health System, Singapore
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18
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Piccirillo AR, Hawse WF, Buechel HM, Silver DL, D’Cruz LM. The long chain fatty acid transporter, MFSD2A, is essential for memory CD8+ T cell formation and maintenance. The Journal of Immunology 2018. [DOI: 10.4049/jimmunol.200.supp.51.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abstract
Access to nutrients is critical for an effective T cell immune response to infection. Although transporters for sugars and amino acids have previously been described in the context of the CD8+ T cell immune response, the active transport of exogenous esterified fatty acids has remained enigmatic. Here we discovered the long chain fatty acid transporter, Major Facilitator Super Family Domain Containing 2a (MFSD2A), is upregulated on activated CD8+ T cells and is essential for their memory cell formation. MFSD2A deficiency resulted in decreased import of long chain fatty acids (LCFAs) esterified to lysophosphatidylcholine (LPC) into activated CD8+ T cells but overall resulted in a normal primary effector T cell response. However, loss of MFSD2A led to reduced memory T cell formation and maintenance. MFSD2A deficient memory CD8+ T cells showed reduced CD127 and CD62L expression and their cell turnover was significantly impaired in contrast to their wildtype counterparts. Moreover, the secondary response to infection was severely diminished in MFSD2A deficient T cells. Mechanistically, import of LCFAs was required to maintain cell energy requirements and ‘fitness’, that when lost resulted in a decreased memory T cell pool and inability to proliferate upon secondary stimulation. Our results show that MFSD2A and LPC may be useful for future small molecule therapy design to generate a more robust T cell response for new vaccines or cancer treatments.
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19
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Miranda DA, Krause WC, Cazenave-Gassiot A, Suzawa M, Escusa H, Foo JC, Shihadih DS, Stahl A, Fitch M, Nyangau E, Hellerstein M, Wenk MR, Silver DL, Ingraham HA. LRH-1 regulates hepatic lipid homeostasis and maintains arachidonoyl phospholipid pools critical for phospholipid diversity. JCI Insight 2018. [PMID: 29515023 DOI: 10.1172/jci.insight.96151] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Excess lipid accumulation is an early signature of nonalcoholic fatty liver disease (NAFLD). Although liver receptor homolog 1 (LRH-1) (encoded by NR5A2) is suppressed in human NAFLD, evidence linking this phospholipid-bound nuclear receptor to hepatic lipid metabolism is lacking. Here, we report an essential role for LRH-1 in hepatic lipid storage and phospholipid composition based on an acute hepatic KO of LRH-1 in adult mice (LRH-1AAV8-Cre mice). Indeed, LRH-1-deficient hepatocytes exhibited large cytosolic lipid droplets and increased triglycerides (TGs). LRH-1-deficient mice fed high-fat diet displayed macrovesicular steatosis, liver injury, and glucose intolerance, all of which were reversed or improved by expressing wild-type human LRH-1. While hepatic lipid synthesis decreased and lipid export remained unchanged in mutants, elevated circulating free fatty acid helped explain the lipid imbalance in LRH-1AAV8-Cre mice. Lipidomic and genomic analyses revealed that loss of LRH-1 disrupts hepatic phospholipid composition, leading to lowered arachidonoyl (AA) phospholipids due to repression of Elovl5 and Fads2, two critical genes in AA biosynthesis. Our findings reveal a role for the phospholipid sensor LRH-1 in maintaining adequate pools of hepatic AA phospholipids, further supporting the idea that phospholipid diversity is an important contributor to healthy hepatic lipid storage.
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Affiliation(s)
- Diego A Miranda
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - William C Krause
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Amaury Cazenave-Gassiot
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - Miyuki Suzawa
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Hazel Escusa
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Juat Chin Foo
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - Diyala S Shihadih
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Andreas Stahl
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Mark Fitch
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Edna Nyangau
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Marc Hellerstein
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Diseases, Duke-National University of Singapore, Singapore
| | - Holly A Ingraham
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
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20
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Vu TM, Ishizu AN, Foo JC, Toh XR, Zhang F, Whee DM, Torta F, Cazenave-Gassiot A, Matsumura T, Kim S, Toh SAES, Suda T, Silver DL, Wenk MR, Nguyen LN. Mfsd2b is essential for the sphingosine-1-phosphate export in erythrocytes and platelets. Nature 2017; 550:524-528. [PMID: 29045386 DOI: 10.1038/nature24053] [Citation(s) in RCA: 162] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 08/31/2017] [Indexed: 12/28/2022]
Abstract
Sphingosine-1-phosphate (S1P), a potent signalling lipid secreted by red blood cells and platelets, plays numerous biologically significant roles. However, the identity of its long-sought exporter is enigmatic. Here we show that the major facilitator superfamily transporter 2b (Mfsd2b), an orphan transporter, is essential for S1P export from red blood cells and platelets. Comprehensive lipidomic analysis indicates a dramatic and specific accumulation of S1P species in Mfsd2b knockout red blood cells and platelets compared with that of wild-type controls. Consistently, biochemical assays from knockout red blood cells, platelets, and cell lines overexpressing human and mouse Mfsd2b proteins demonstrate that Mfsd2b actively exports S1P. Plasma S1P level in knockout mice is significantly reduced by 42-54% of that of wild-type level, indicating that Mfsd2b pathway contributes approximately half of the plasma S1P pool. The reduction of plasma S1P in knockout mice is insufficient to cause blood vessel leakiness, but it does render the mice more sensitive to anaphylactic shock. Stress-induced erythropoiesis significantly increased plasma S1P levels and knockout mice were sensitive to these treatments. Surprisingly, knockout mice exhibited haemolysis associated with red blood cell stomatocytes, and the haemolytic phenotype was severely increased with signs of membrane fragility under stress erythropoiesis. We show that S1P secretion by Mfsd2b is critical for red blood cell morphology. Our data reveal an unexpected physiological role of red blood cells in sphingolipid metabolism in circulation. These findings open new avenues for investigating the signalling roles of S1P derived from red blood cells and platelets.
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Affiliation(s)
- Thiet M Vu
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545
| | - Ayako-Nakamura Ishizu
- Cancer Science Institute, Yong Loo Lin School of Medicine, National University of Singapore, 14 Medical Drive, Singapore 117599
| | - Juat Chin Foo
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, 28 Medical Drive, Singapore 117456
| | - Xiu Ru Toh
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545
| | - Fangyu Zhang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545
| | - Ding Ming Whee
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545
| | - Federico Torta
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545.,Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, 28 Medical Drive, Singapore 117456
| | - Amaury Cazenave-Gassiot
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545.,Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, 28 Medical Drive, Singapore 117456
| | - Takayoshi Matsumura
- Cancer Science Institute, Yong Loo Lin School of Medicine, National University of Singapore, 14 Medical Drive, Singapore 117599
| | - Sangho Kim
- Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583.,Biomedical Institute for Global Health Research and Technology, National University of Singapore, 14 Medical Drive, Singapore 117599.,NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456
| | - Sue-Anne E S Toh
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599
| | - Toshio Suda
- Cancer Science Institute, Yong Loo Lin School of Medicine, National University of Singapore, 14 Medical Drive, Singapore 117599
| | - David L Silver
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Medical School, 8 College Road, Singapore 169857
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545.,Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, 28 Medical Drive, Singapore 117456
| | - Long N Nguyen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Medical Drive, Singapore 117545
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21
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Miranda DA, Krause WC, Cazenave A, Escusa HA, Shihadih DS, Stahl A, Wenk MR, Silver DL, Ingraham HA. Abstract 281: Hepatic Liver Receptor Homolog-1, a Key Regulator of Lipid Storage and Phospholipid Diversity. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiovascular disease and malignancy are the most common cause of death in Non-alcoholic Steatohepatitis (NASH) patients. Aside from lifestyle modification, there is currently no treatment for NASH. Activation of Liver Receptor Homolog-1 (Lrh-1), known to bind phospholipid ligands, has been shown to effectively reduce liver triglyceride (TG) in DIO mice, raising Lrh-1 as a possible target for treating NASH. Despite this finding, hepatic TGs are equivalent in controls and liver-specific Lrh-1 knockout (LKO or
Lrh1
AlbCre
) mice, regardless of diet. Given this discrepancy, we sought to characterize Lrh-1’s role in hepatic lipid metabolism by acutely deleting Lrh-1 in the adult liver, thus eliminating potential compensatory developmental effects associated with LKO. To acutely eliminate Lrh-1 in hepatocytes, 6-week old
Lrh-1
fl/f
l
male mice were infected with AVV8-TBG-eGFP (Control) or AAV8-TBG-Cre (LKO
AAVCre
) via retro-orbital injection and fed chow or high fat diet. LKO
AAVCre
mice developed hepatic steatosis after six weeks on standard chow or high fat diet. Furthermore, LKO
AAVCre
hepatocytes exhibited large lipid droplets, which were visible as early as 2 wks post-infection, thus suggesting that lipid handling is significantly altered in LKO
AAVCre
hepatocytes, independent of fatty acid transport or oxidation. LKO
AAVCre
exhibited lower
Pcsk9
expression, which correlated with decreased fasting plasma LDL-C. Consistent with other studies showing that perturbations in phospholipid pools affect lipid storage, lipidomic analyses revealed a significant reduction in phospholipid species containing arachidonic acid (AA), thus reducing the overall diversity of key membrane phospholipids. RNA-Seq analyses from LKO
AAVCre
livers confirmed that factors promoting lipid droplet size (
Cidec
,
Plin4
) were greatly increased while key enzymes in biosynthesis of unsaturated fatty acids were reduced (
Fads1, Fads2
and
Elovl5
). In addition, expression of human LRH-1 in LKO
AAVCre
decreased hepatic TG and improved glucose tolerance in DIO mice, in a ligand dependent manner. Collectively our data establish a novel role for Lrh-1 as a key regulator of lipid storage, thereby providing the first in vivo evidence as to why phospholipid serve as Lrh-1 ligands.
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Affiliation(s)
| | | | | | | | | | | | - Markus R Wenk
- Singapore Lipidomics Incubator, Singapore, Singapore
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22
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Ahmed MY, Al-Khayat A, Al-Murshedi F, Al-Futaisi A, Chioza BA, Pedro Fernandez-Murray J, Self JE, Salter CG, Harlalka GV, Rawlins LE, Al-Zuhaibi S, Al-Azri F, Al-Rashdi F, Cazenave-Gassiot A, Wenk MR, Al-Salmi F, Patton MA, Silver DL, Baple EL, McMaster CR, Crosby AH. A mutation of EPT1 (SELENOI) underlies a new disorder of Kennedy pathway phospholipid biosynthesis. Brain 2017; 140:547-554. [PMID: 28052917 PMCID: PMC5382949 DOI: 10.1093/brain/aww318] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 10/19/2016] [Indexed: 12/20/2022] Open
Abstract
Mutations in genes involved in lipid metabolism have increasingly been associated with various subtypes of hereditary spastic paraplegia, a highly heterogeneous group of neurodegenerative motor neuron disorders characterized by spastic paraparesis. Here, we report an unusual autosomal recessive neurodegenerative condition, best classified as a complicated form of hereditary spastic paraplegia, associated with mutation in the ethanolaminephosphotransferase 1 (EPT1) gene (now known as SELENOI), responsible for the final step in Kennedy pathway forming phosphatidylethanolamine from CDP-ethanolamine. Phosphatidylethanolamine is a glycerophospholipid that, together with phosphatidylcholine, constitutes more than half of the total phospholipids in eukaryotic cell membranes. We determined that the mutation defined dramatically reduces the enzymatic activity of EPT1, thereby hindering the final step in phosphatidylethanolamine synthesis. Additionally, due to central nervous system inaccessibility we undertook quantification of phosphatidylethanolamine levels and species in patient and control blood samples as an indication of liver phosphatidylethanolamine biosynthesis. Although this revealed alteration to levels of specific phosphatidylethanolamine fatty acyl species in patients, overall phosphatidylethanolamine levels were broadly unaffected indicating that in blood EPT1 inactivity may be compensated for, in part, via alternate biochemical pathways. These studies define the first human disorder arising due to defective CDP-ethanolamine biosynthesis and provide new insight into the role of Kennedy pathway components in human neurological function.
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Affiliation(s)
- Mustafa Y Ahmed
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | - Aisha Al-Khayat
- Department of Biology, College of Science, Sultan Qaboos University, Sultanate of Oman
| | - Fathiya Al-Murshedi
- Department of Genetics, College of Medicine, Sultan Qaboos University, Sultanate of Oman
| | - Amna Al-Futaisi
- Department of Paediatrics, Sultan Qaboos University Hospital, Sultanate of Oman
| | - Barry A Chioza
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | | | - Jay E Self
- Faculty of Medicine, University of Southampton, UK
| | - Claire G Salter
- West Midlands Regional Genetics Service, Birmingham Women's NHS Foundation Trust, Mindelsohn Way, Birmingham, B15 2TG, UK
| | - Gaurav V Harlalka
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | - Lettie E Rawlins
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | - Sana Al-Zuhaibi
- Department of Ophthalmology, Sultan Qaboos University Hospital, Sultanate of Oman
| | - Faisal Al-Azri
- Department of Radiology and Molecular Imaging, Sultan Qaboos University Hospital, Sultanate of Oman
| | - Fatma Al-Rashdi
- Department of Paediatrics, Sameal Hospital, Ministry of Health, Sultanate of Oman
| | - Amaury Cazenave-Gassiot
- SLING, Life Sciences Institute, National University of Singapore, Singapore.,Department of Biochemistry, National University of Singapore, Singapore
| | - Markus R Wenk
- SLING, Life Sciences Institute, National University of Singapore, Singapore.,Department of Biochemistry, National University of Singapore, Singapore
| | - Fatema Al-Salmi
- Department of Biology, College of Science, Sultan Qaboos University, Sultanate of Oman
| | - Michael A Patton
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK.,Department of Biology, College of Science, Sultan Qaboos University, Sultanate of Oman
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore
| | - Emma L Baple
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | | | - Andrew H Crosby
- Medical Research (Level 4), University of Exeter Medical School, RILD Wellcome Wolfson Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
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23
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Piccirillo A, Hawse WF, Menk AV, Wallace CT, Buechel HM, Watkins SC, Wendell SG, Delgoffe GM, Silver DL, D’Cruz LM. The role of LPC and lipid transporter MFSD2A in CD8 T cells. The Journal of Immunology 2017. [DOI: 10.4049/jimmunol.198.supp.121.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Abstract
Little is known about how effector CD8 T cells obtain exogenous long chain fatty acids (LCFAs) during T cell activation. LCFAs assist with membrane biogenesis and are required for rapid proliferation as well as effector molecule generation. One potential mechanism of fatty acid import is in the form of lysophophatidylcholine (LPC) by lipid carrier major facilitator superfamily domain containing 2a (MFSD2A). Here, we show that MFSD2A is highly expressed in activated CD8 T cells. Conditional loss of MFSD2A caused an altered effector response and resulted in defective memory cell formation. Taken together, these data show MFSD2A and LPC play a role in CD8 T cell metabolomics. Our future studies will use mass spectrometry lipidomics and gene expression analysis to identify the mechanisms by which CD8 T cells use LCFAs to mount a robust immune response to infection.
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Affiliation(s)
- Ann Piccirillo
- 1Natl. Univ. of Singapore, Singapore
- 2Univ. of Pittsburgh Grad. Sch. of Publ. Hlth
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24
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McMahon JJ, Miller EE, Silver DL. The exon junction complex in neural development and neurodevelopmental disease. Int J Dev Neurosci 2016; 55:117-123. [PMID: 27071691 DOI: 10.1016/j.ijdevneu.2016.03.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 03/28/2016] [Indexed: 11/17/2022] Open
Abstract
Post-transcriptional mRNA metabolism has emerged as a critical regulatory nexus in proper development and function of the nervous system. In particular, recent studies highlight roles for the exon junction complex (EJC) in neurodevelopment. The EJC is an RNA binding complex composed of 3 core proteins, EIF4A3 (DDX48), RBM8A (Y14), and MAGOH, and is a major hub of post-transcriptional regulation. Following deposition onto mRNA, the EJC serves as a platform for the binding of peripheral factors which together regulate splicing, nonsense mediated decay, translation, and RNA localization. While fundamental molecular roles of the EJC have been well established, the in vivo relevance in mammals has only recently been examined. New genetic models and cellular assays have revealed core and peripheral EJC components play critical roles in brain development, stem cell function, neuronal outgrowth, and neuronal activity. Moreover, human genetics studies increasingly implicate EJC components in the etiology of neurodevelopmental disorders. Collectively, these findings indicate that proper dosage of EJC components is necessary for diverse aspects of neuronal development and function. Going forward, genetic models of EJC components will provide valuable tools for further elucidating functions in the nervous system relevant for neurodevelopmental disease.
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Affiliation(s)
- J J McMahon
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, United States
| | - E E Miller
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, United States
| | - D L Silver
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, United States; Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, United States; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, United States; Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC 27710, United States.
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25
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Wong BH, Chan JP, Cazenave-Gassiot A, Poh RW, Foo JC, Galam DLA, Ghosh S, Nguyen LN, Barathi VA, Yeo SW, Luu CD, Wenk MR, Silver DL. Mfsd2a Is a Transporter for the Essential ω-3 Fatty Acid Docosahexaenoic Acid (DHA) in Eye and Is Important for Photoreceptor Cell Development. J Biol Chem 2016; 291:10501-14. [PMID: 27008858 DOI: 10.1074/jbc.m116.721340] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Indexed: 12/22/2022] Open
Abstract
Eye photoreceptor membrane discs in outer rod segments are highly enriched in the visual pigment rhodopsin and the ω-3 fatty acid docosahexaenoic acid (DHA). The eye acquires DHA from blood, but transporters for DHA uptake across the blood-retinal barrier or retinal pigment epithelium have not been identified. Mfsd2a is a newly described sodium-dependent lysophosphatidylcholine (LPC) symporter expressed at the blood-brain barrier that transports LPCs containing DHA and other long-chain fatty acids. LPC transport via Mfsd2a has been shown to be necessary for human brain growth. Here we demonstrate that Mfsd2a is highly expressed in retinal pigment epithelium in embryonic eye, before the development of photoreceptors, and is the primary site of Mfsd2a expression in the eye. Eyes from whole body Mfsd2a-deficient (KO) mice, but not endothelium-specific Mfsd2a-deficient mice, were DHA-deficient and had significantly reduced LPC/DHA transport in vivo Fluorescein angiography indicated normal blood-retinal barrier function. Histological and electron microscopic analysis indicated that Mfsd2a KO mice exhibited a specific reduction in outer rod segment length, disorganized outer rod segment discs, and mislocalization of and reduction in rhodopsin early in postnatal development without loss of photoreceptors. Minor photoreceptor cell loss occurred in adult Mfsd2a KO mice, but electroretinography indicated visual function was normal. The developing eyes of Mfsd2a KO mice had activated microglia and up-regulation of lipogenic and cholesterogenic genes, likely adaptations to loss of LPC transport. These findings identify LPC transport via Mfsd2a as an important pathway for DHA uptake in eye and for development of photoreceptor membrane discs.
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Affiliation(s)
- Bernice H Wong
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Jia Pei Chan
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Amaury Cazenave-Gassiot
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Rebecca W Poh
- the Carl Zeiss Pte. Ltd., Microscopy Business Group, Singapore, 50 Kaki Bukit Place, 05-01, Singapore 415926, Singapore
| | - Juat Chin Foo
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - Dwight L A Galam
- From the Signature Research Program in Cardiovascular and Metabolic Disorders
| | - Sujoy Ghosh
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Centre for Computational Biology, and
| | - Long N Nguyen
- the Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 5 Science Drive 2, Building MD4, Level 1-03A, Singapore 117545, Singapore
| | - Veluchamy A Barathi
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Rd 119228, NUHS Tower Block, Level 11, Singapore 117597, Singapore, and ACP Ophthalmology, Duke-National University of Singapore Graduate Medical School, 8 College Road, Singapore 169857, Singapore
| | - Sia W Yeo
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore
| | - Chi D Luu
- the Singapore Eye Research Institute, 11 Third Hospital Ave., Singapore 168751, Singapore, the Centre for Eye Research Australia, Level 1, 32 Gisborne St., East Melbourne, Victoria 3002, Australia
| | - Markus R Wenk
- the Department of Biochemistry, National University of Singapore, 8 Medical Drive, Block MD 7, Singapore 117597, Singapore
| | - David L Silver
- From the Signature Research Program in Cardiovascular and Metabolic Disorders,
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26
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Quek DQY, Nguyen LN, Fan H, Silver DL. Structural Insights into the Transport Mechanism of the Human Sodium-dependent Lysophosphatidylcholine Transporter MFSD2A. J Biol Chem 2016; 291:9383-94. [PMID: 26945070 DOI: 10.1074/jbc.m116.721035] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Indexed: 01/22/2023] Open
Abstract
Major facilitator superfamily domain containing 2A (MFSD2A) was recently characterized as a sodium-dependent lysophosphatidylcholine transporter expressed at the blood-brain barrier endothelium. It is the primary route for importation of docosohexaenoic acid and other long-chain fatty acids into fetal and adult brain and is essential for mouse and human brain growth and function. Remarkably, MFSD2A is the first identified major facilitator superfamily member that uniquely transports lipids, implying that MFSD2A harbors unique structural features and transport mechanism. Here, we present three three-dimensional structural models of human MFSD2A derived by homology modeling using MelB- and LacY-based crystal structures and refined by biochemical analysis. All models revealed 12 transmembrane helices and connecting loops and represented the partially outward-open, outward-partially occluded, and inward-open states of the transport cycle. In addition to a conserved sodium-binding site, three unique structural features were identified as follows: a phosphate headgroup binding site, a hydrophobic cleft to accommodate a hydrophobic hydrocarbon tail, and three sets of ionic locks that stabilize the outward-open conformation. Ligand docking studies and biochemical assays identified Lys-436 as a key residue for transport. It is seen forming a salt bridge with the negative charge on the phosphate headgroup. Importantly, MFSD2A transported structurally related acylcarnitines but not a lysolipid without a negative charge, demonstrating the necessity of a negatively charged headgroup interaction with Lys-436 for transport. These findings support a novel transport mechanism by which lysophosphatidylcholines are "flipped" within the transporter cavity by pivoting about Lys-436 leading to net transport from the outer to the inner leaflet of the plasma membrane.
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Affiliation(s)
- Debra Q Y Quek
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore 169857
| | - Long N Nguyen
- the Department of Biochemistry, Yong Loo Lin School of Medicine, and
| | - Hao Fan
- the Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 138671 Singapore, Singapore Department of Biological Sciences, National University of Singapore, Singapore 117545, and
| | - David L Silver
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore 169857,
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27
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Goh VJ, Tan JSY, Tan BC, Seow C, Ong WY, Lim YC, Sun L, Ghosh S, Silver DL. Postnatal Deletion of Fat Storage-inducing Transmembrane Protein 2 (FIT2/FITM2) Causes Lethal Enteropathy. J Biol Chem 2015; 290:25686-99. [PMID: 26304121 DOI: 10.1074/jbc.m115.676700] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 02/03/2023] Open
Abstract
Lipid droplets (LDs) are phylogenetically conserved cytoplasmic organelles that store neutral lipids within a phospholipid monolayer. LDs compartmentalize lipids and may help to prevent cellular damage caused by their excess or bioactive forms. FIT2 is a ubiquitously expressed transmembrane endoplasmic reticulum (ER) membrane protein that has previously been implicated in LD formation in mammalian cells and tissue. Recent data indicate that FIT2 plays an essential role in fat storage in an in vivo constitutive adipose FIT2 knock-out mouse model, but the physiological effects of postnatal whole body FIT2 depletion have never been studied. Here, we show that tamoxifen-induced FIT2 deletion using a whole body ROSA26CreER(T2)-driven FIT2 knock-out (iF2KO) mouse model leads to lethal intestinal pathology, including villus blunting and death of intestinal crypts, and loss of lipid absorption. iF2KO mice lose weight and die within 2 weeks after the first tamoxifen dose. At the cellular level, LDs failed to form in iF2KO enterocytes after acute oil challenge and instead accumulated within the ER. Intestinal bile acid transporters were transcriptionally dysregulated in iF2KO mice, leading to the buildup of bile acids within enterocytes. These data support the conclusion that FIT2 plays an essential role in regulating intestinal health and survival postnatally.
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Affiliation(s)
- Vera J Goh
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Jolene S Y Tan
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Bryan C Tan
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Colin Seow
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Wei-Yi Ong
- the Department of Anatomy and Neurobiology and Aging Research Programme, National University of Singapore, Singapore 119260, Singapore
| | - Yen Ching Lim
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Lei Sun
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - Sujoy Ghosh
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
| | - David L Silver
- From the Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, 8 College Road, 169857 Singapore and
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28
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Alakbarzade V, Hameed A, Quek DQY, Chioza BA, Baple EL, Cazenave-Gassiot A, Nguyen LN, Wenk MR, Ahmad AQ, Sreekantan-Nair A, Weedon MN, Rich P, Patton MA, Warner TT, Silver DL, Crosby AH. A partially inactivating mutation in the sodium-dependent lysophosphatidylcholine transporter MFSD2A causes a non-lethal microcephaly syndrome. Nat Genet 2015; 47:814-7. [PMID: 26005865 DOI: 10.1038/ng.3313] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 05/01/2015] [Indexed: 12/14/2022]
Abstract
The major pathway by which the brain obtains essential omega-3 fatty acids from the circulation is through a sodium-dependent lysophosphatidylcholine (LPC) transporter (MFSD2A), expressed in the endothelium of the blood-brain barrier. Here we show that a homozygous mutation affecting a highly conserved MFSD2A residue (p.Ser339Leu) is associated with a progressive microcephaly syndrome characterized by intellectual disability, spasticity and absent speech. We show that the p.Ser339Leu alteration does not affect protein or cell surface expression but rather significantly reduces, although not completely abolishes, transporter activity. Notably, affected individuals displayed significantly increased plasma concentrations of LPCs containing mono- and polyunsaturated fatty acyl chains, indicative of reduced brain uptake, confirming the specificity of MFSD2A for LPCs having mono- and polyunsaturated fatty acyl chains. Together, these findings indicate an essential role for LPCs in human brain development and function and provide the first description of disease associated with aberrant brain LPC transport in humans.
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Affiliation(s)
- Vafa Alakbarzade
- 1] Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK. [2] Reta Lila Weston Institute of Neurological Studies, Department of Molecular Neurosciences, University College London Institute of Neurology, London, UK
| | - Abdul Hameed
- Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, Pakistan
| | - Debra Q Y Quek
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Barry A Chioza
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK
| | - Emma L Baple
- 1] Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK. [2] Human Genetics and Genomic Medicine, Faculty of Medicine, University of Southampton, Southampton, UK. [3] Wessex Clinical Genetics Service, Princess Anne Hospital, Southampton, UK
| | | | - Long N Nguyen
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Markus R Wenk
- Life Sciences Institute, National University of Singapore, Singapore
| | - Arshia Q Ahmad
- 1] Department of Physical Medicine and Rehabilitation, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, Indiana, USA. [2] Rehabilitation Hospital Indiana, Indianapolis, Indiana, USA
| | - Ajith Sreekantan-Nair
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK
| | - Michael N Weedon
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK
| | - Phil Rich
- Department of Neuroradiology, St. George's Hospital, London, UK
| | - Michael A Patton
- 1] Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK. [2] Southwest Thames Regional Genetics Service, St George's Healthcare National Health Service (NHS) Trust, London, UK
| | - Thomas T Warner
- Reta Lila Weston Institute of Neurological Studies, Department of Molecular Neurosciences, University College London Institute of Neurology, London, UK
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Andrew H Crosby
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD Wellcome Wolfson Centre, Exeter, UK
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29
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Lu GD, Ang YH, Zhou J, Tamilarasi J, Yan B, Lim YC, Srivastava S, Salto-Tellez M, Hui KM, Shen HM, Nguyen LN, Tan BC, Silver DL, Hooi SC. CCAAT/enhancer binding protein α predicts poorer prognosis and prevents energy starvation-induced cell death in hepatocellular carcinoma. Hepatology 2015; 61:965-78. [PMID: 25363290 PMCID: PMC4365685 DOI: 10.1002/hep.27593] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 10/28/2014] [Indexed: 12/12/2022]
Abstract
UNLABELLED CCAAT enhancer binding protein α (C/EBPα) plays an essential role in cellular differentiation, growth, and energy metabolism. Here, we investigate the correlation between C/EBPα and hepatocellular carcinoma (HCC) patient outcomes and how C/EBPα protects cells against energy starvation. Expression of C/EBPα protein was increased in the majority of HCCs examined (191 pairs) compared with adjacent nontumor liver tissues in HCC tissue microarrays. Its upregulation was correlated significantly with poorer overall patient survival in both Kaplan-Meier survival (P=0.017) and multivariate Cox regression (P=0.028) analyses. Stable C/EBPα-silenced cells failed to establish xenograft tumors in nude mice due to extensive necrosis, consistent with increased necrosis in human C/EBPα-deficient HCC nodules. Expression of C/EBPα protected HCC cells in vitro from glucose and glutamine starvation-induced cell death through autophagy-involved lipid catabolism. Firstly, C/EBPα promoted lipid catabolism during starvation, while inhibition of fatty acid beta-oxidation significantly sensitized cell death. Secondly, autophagy was activated in C/EBPα-expressing cells, and the inhibition of autophagy by ATG7 knockdown or chloroquine treatment attenuated lipid catabolism and subsequently sensitized cell death. Finally, we identified TMEM166 as a key player in C/EBPα-mediated autophagy induction and protection against starvation. CONCLUSION The C/EBPα gene is important in that it links HCC carcinogenesis to autophagy-mediated lipid metabolism and resistance to energy starvation; its expression in HCC predicts poorer patient prognosis.
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Affiliation(s)
- Guo-Dong Lu
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
- School of Public Health, Guangxi Medical UniversityChina
| | - Yang Huey Ang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
| | - Jing Zhou
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
- Guangxi Scientific Experimental Center of Traditional Chinese Medicine, Guangxi University of Chinese MedicineChina
| | - Jegadeesan Tamilarasi
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
| | - Benedict Yan
- Department of Pathology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
| | - Yaw Chyn Lim
- Department of Pathology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
| | | | - Manuel Salto-Tellez
- Centre for Cancer Research and Cell Biology, Queen's University BelfastBelfast, UK
| | - Kam M Hui
- Division of Cellular and Molecular Research, National Cancer CentreSingapore
| | - Han-Ming Shen
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
| | - Long N Nguyen
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Graduate Medical SchoolSingapore
| | - Bryan C Tan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Graduate Medical SchoolSingapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Graduate Medical SchoolSingapore
| | - Shing Chuan Hooi
- Department of Physiology, Yong Loo Lin School of Medicine, National University of SingaporeSingapore
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30
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Abstract
The lipid droplet (LD) is a phylogenetically conserved organelle. In eukaryotes, it is born from the endoplasmic reticulum, but unlike its parent organelle, LDs are the only known cytosolic organelles that are micellar in structure. LDs are implicated in numerous physiological and pathophysiological functions. Many aspects of the LD has captured the attention of diverse scientists alike and has recently led to an explosion in information on the LD biogenesis, expansion and fusion, identification of LD proteomes and diseases associated with LD biology. This review will provide a brief history of this fascinating organelle and provide some contemporary views of unanswered questions in LD biogenesis.
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Affiliation(s)
- David A Gross
- Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School Singapore , Singapore , and
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31
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Siddiqi S, Foo JN, Vu A, Azim S, Silver DL, Mansoor A, Tay SKH, Abbasi S, Hashmi AH, Janjua J, Khalid S, Tai ES, Yeo GW, Khor CC. A novel splice-site mutation in ALS2 establishes the diagnosis of juvenile amyotrophic lateral sclerosis in a family with early onset anarthria and generalized dystonias. PLoS One 2014; 9:e113258. [PMID: 25474699 PMCID: PMC4256290 DOI: 10.1371/journal.pone.0113258] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 10/21/2014] [Indexed: 11/23/2022] Open
Abstract
The diagnosis of childhood neurological disorders remains challenging given the overlapping clinical presentation across subgroups and heterogeneous presentation within subgroups. To determine the underlying genetic cause of a severe neurological disorder in a large consanguineous Pakistani family presenting with severe scoliosis, anarthria and progressive neuromuscular degeneration, we performed genome-wide homozygosity mapping accompanied by whole-exome sequencing in two affected first cousins and their unaffected parents to find the causative mutation. We identified a novel homozygous splice-site mutation (c.3512+1G>A) in the ALS2 gene (NM_020919.3) encoding alsin that segregated with the disease in this family. Homozygous loss-of-function mutations in ALS2 are known to cause juvenile-onset amyotrophic lateral sclerosis (ALS), one of the many neurological conditions having overlapping symptoms with many neurological phenotypes. RT-PCR validation revealed that the mutation resulted in exon-skipping as well as the use of an alternative donor splice, both of which are predicted to cause loss-of-function of the resulting proteins. By examining 216 known neurological disease genes in our exome sequencing data, we also identified 9 other rare nonsynonymous mutations in these genes, some of which lie in highly conserved regions. Sequencing of a single proband might have led to mis-identification of some of these as the causative variant. Our findings established a firm diagnosis of juvenile ALS in this family, thus demonstrating the use of whole exome sequencing combined with linkage analysis in families as a powerful tool for establishing a quick and precise genetic diagnosis of complex neurological phenotypes.
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Affiliation(s)
- Saima Siddiqi
- Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, Pakistan
| | - Jia Nee Foo
- Human Genetics, Genome Institute of Singapore, A*STAR, Singapore, Singapore
- * E-mail:
| | - Anthony Vu
- Department of Cellular and Molecular Medicine and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California, United States of America
| | - Saad Azim
- Ali Medical Center, F8/1, Islamabad, Pakistan
| | - David L. Silver
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Atika Mansoor
- Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, Pakistan
| | - Stacey Kiat Hong Tay
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Sumiya Abbasi
- International Islamic University, Islamabad, Pakistan
| | | | - Jamal Janjua
- College of Physicians and Surgeons (CPSP), Islamabad, Pakistan
| | - Sumbal Khalid
- International Islamic University, Islamabad, Pakistan
| | - E. Shyong Tai
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, National University Hospital System, Singapore, Singapore
- Saw Swee Hock School of Public Health, National University of Singapore, National University Hospital System, Singapore, Singapore
| | - Gene W. Yeo
- Department of Cellular and Molecular Medicine and Institute for Genomic Medicine, University of California at San Diego, La Jolla, California, United States of America
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Chiea Chuen Khor
- Human Genetics, Genome Institute of Singapore, A*STAR, Singapore, Singapore
- Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
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32
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Kim HJ, Cho H, Alexander R, Patterson HC, Gu M, Lo KA, Xu D, Goh VJ, Nguyen LN, Chai X, Huang CX, Kovalik JP, Ghosh S, Trajkovski M, Silver DL, Lodish H, Sun L. MicroRNAs are required for the feature maintenance and differentiation of brown adipocytes. Diabetes 2014; 63:4045-56. [PMID: 25008181 PMCID: PMC4238002 DOI: 10.2337/db14-0466] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Brown adipose tissue (BAT) is specialized to burn lipids for heat generation as a natural defense against cold and obesity. Previous studies established microRNAs (miRNAs) as essential regulators of brown adipocyte differentiation, but whether miRNAs are required for the feature maintenance of mature brown adipocytes remains unknown. To address this question, we ablated Dgcr8, a key regulator of the miRNA biogenesis pathway, in mature brown as well as in white adipocytes. Adipose tissue-specific Dgcr8 knockout mice displayed enlarged but pale interscapular brown fat with decreased expression of genes characteristic of brown fat and were intolerant to cold exposure. Primary brown adipocyte cultures in vitro confirmed that miRNAs are required for marker gene expression in mature brown adipocytes. We also demonstrated that miRNAs are essential for the browning of subcutaneous white adipocytes in vitro and in vivo. Using this animal model, we performed miRNA expression profiling analysis and identified a set of BAT-specific miRNAs that are upregulated during brown adipocyte differentiation and enriched in brown fat compared with other organs. We identified miR-182 and miR-203 as new regulators of brown adipocyte development. Taken together, our study demonstrates an essential role of miRNAs in the maintenance as well as in the differentiation of brown adipocytes.
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Affiliation(s)
- Hye-Jin Kim
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Hyunjii Cho
- Whitehead Institute for Biomedical Research, Cambridge, MA Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Ryan Alexander
- Whitehead Institute for Biomedical Research, Cambridge, MA Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Heide Christine Patterson
- Whitehead Institute for Biomedical Research, Cambridge, MA Department of Pathology, Brigham and Women's Hospital, Boston, MA
| | - Minxia Gu
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | | | - Dan Xu
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Vera J Goh
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Long N Nguyen
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Xiaoran Chai
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Cher X Huang
- Whitehead Institute for Biomedical Research, Cambridge, MA Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Jean-Paul Kovalik
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Sujoy Ghosh
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Mirko Trajkovski
- University of Geneva, Medical Faculty, Department of Cell Physiology and Metabolism, Centre Médical Universitaire (CMU), Geneva, Switzerland
| | - David L Silver
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore
| | - Harvey Lodish
- Whitehead Institute for Biomedical Research, Cambridge, MA Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Lei Sun
- Cardiovascular and Metabolic Disorders, Duke-National University of Singapore Graduate Medical School, Singapore Institute of Molecular and Cell Biology, Singapore
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33
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Tan JSY, Seow CJP, Goh VJ, Silver DL. Recent advances in understanding proteins involved in lipid droplet formation, growth and fusion. J Genet Genomics 2014; 41:251-9. [PMID: 24894352 DOI: 10.1016/j.jgg.2014.03.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Revised: 03/03/2014] [Accepted: 03/05/2014] [Indexed: 01/29/2023]
Abstract
Lipid droplets (LDs) were once viewed as simple, inert lipid micelles. However, they are now known to be organelles with a rich proteome involved in a myriad of cellular processes. LDs are heterogeneous in nature with different sizes and compositions of phospholipids, neutral lipids and proteins. This review takes a focused look at the roles of proteins involved in the regulation of LD formation, expansion, and morphology. The related proteins are summarized such as the fat-specific protein (Fsp27), fat storage-inducing transmembrane (FIT) proteins, seipin and ADP-ribosylation factor 1-coat protein complex I (Arf-COPI). Finally, we present important challenges in LD biology for a deeper understanding of this dynamic organelle to be achieved.
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Affiliation(s)
- Jolene S Y Tan
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School Singapore, Singapore 169857, Singapore
| | - Colin J P Seow
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School Singapore, Singapore 169857, Singapore
| | - Vera J Goh
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School Singapore, Singapore 169857, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School Singapore, Singapore 169857, Singapore.
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34
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Miranda DA, Kim JH, Nguyen LN, Cheng W, Tan BC, Goh VJ, Tan JSY, Yaligar J, Kn BP, Velan SS, Wang H, Silver DL. Fat storage-inducing transmembrane protein 2 is required for normal fat storage in adipose tissue. J Biol Chem 2014; 289:9560-72. [PMID: 24519944 DOI: 10.1074/jbc.m114.547687] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Triglycerides within the cytosol of cells are stored in a phylogenetically conserved organelle called the lipid droplet (LD). LDs can be formed at the endoplasmic reticulum, but mechanisms that regulate the formation of LDs are incompletely understood. Adipose tissue has a high capacity to form lipid droplets and store triglycerides. Fat storage-inducing transmembrane protein 2 (FITM2/FIT2) is highly expressed in adipocytes, and data indicate that FIT2 has an important role in the formation of LDs in cells, but whether FIT2 has a physiological role in triglyceride storage in adipose tissue remains unproven. Here we show that adipose-specific deficiency of FIT2 (AF2KO) in mice results in progressive lipodystrophy of white adipose depots and metabolic dysfunction. In contrast, interscapular brown adipose tissue of AF2KO mice accumulated few but large LDs without changes in cellular triglyceride levels. High fat feeding of AF2KO mice or AF2KO mice on the genetically obese ob/ob background accelerated the onset of lipodystrophy. At the cellular level, primary adipocyte precursors of white and brown adipose tissue differentiated in vitro produced fewer but larger LDs without changes in total cellular triglyceride or triglyceride biosynthesis. These data support the conclusion that FIT2 plays an essential, physiological role in fat storage in vivo.
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Affiliation(s)
- Diego A Miranda
- From the Signature Research Program in Cardiovascular and Metabolic Disorders and
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35
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Abstract
Nonalcoholic fatty liver disease (NAFLD) is a growing problem worldwide. Nonalcoholic fatty liver disease is characterized by an abnormal accumulation of triglyceride-rich lipid droplets (LDs) in the liver, which can lead to liver inflammation and metabolic disturbances. Lipid droplets are dynamic organelles that have recently gained considerable scientific interest. Their formation and growth are regulated processes requiring the participation of many endoplasmic reticulum- (ER-) and LD-associated proteins, which may serve as potential therapeutic targets for NAFLD. Protein families such as fat-inducing transmembrane proteins 1 and 2 (FITM1/FIT1 and FITM2/FIT2), the CIDE family of proteins, and the perilipin family, play important roles in LD biology. In this review, the authors discuss current views on LD formation and growth, and how various proteins may affect LD metabolism and lipoprotein assembly in the pathogenesis of NAFLD.
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Affiliation(s)
- Vera J Goh
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School, Singapore
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36
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Berger JH, Charron MJ, Silver DL. Major facilitator superfamily domain-containing protein 2a (MFSD2A) has roles in body growth, motor function, and lipid metabolism. PLoS One 2012; 7:e50629. [PMID: 23209793 PMCID: PMC3510178 DOI: 10.1371/journal.pone.0050629] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 10/22/2012] [Indexed: 12/24/2022] Open
Abstract
The metabolic adaptations to fasting in the liver are largely controlled by the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARα), where PPARα upregulates genes encoding the biochemical pathway for β-oxidation of fatty acids and ketogenesis. As part of an effort to identify and characterize nutritionally regulated genes that play physiological roles in the adaptation to fasting, we identified Major facilitator superfamily domain-containing protein 2a (Mfsd2a) as a fasting-induced gene regulated by both PPARα and glucagon signaling in the liver. MFSD2A is a cell-surface protein homologous to bacterial sodium-melibiose transporters. Hepatic expression and turnover of MFSD2A is acutely regulated by fasting/refeeding, but expression in the brain is constitutive. Relative to wildtype mice, gene-targeted Mfsd2a knockout mice are smaller, leaner, and have decreased serum, liver and brown adipose triglycerides. Mfsd2a knockout mice have normal liver lipid metabolism but increased whole body energy expenditure, likely due to increased β-oxidation in brown adipose tissue and significantly increased voluntary movement, but surprisingly exhibited a form of ataxia. Together, these results indicate that MFSD2A is a nutritionally regulated gene that plays myriad roles in body growth and development, motor function, and lipid metabolism. Moreover, these data suggest that the ligand(s) that are transported by MFSD2A play important roles in these physiological processes and await future identification.
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Affiliation(s)
- Justin H. Berger
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Maureen J. Charron
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Medicine, Division of Endocrinology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Obstetrics and Gynecology and Women’s Health, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David L. Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular & Metabolic Disorders, Duke-NUS Graduate Medical School, Singapore, Singapore
- * E-mail:
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37
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Nguyen LN, Cesar GV, Le GTT, Silver DL, Nimrichter L, Nosanchuk JD. Inhibition of Candida parapsilosis fatty acid synthase (Fas2) induces mitochondrial cell death in serum. PLoS Pathog 2012; 8:e1002879. [PMID: 22952445 PMCID: PMC3431346 DOI: 10.1371/journal.ppat.1002879] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 07/12/2012] [Indexed: 11/21/2022] Open
Abstract
We have recently observed that a fatty acid auxotrophic mutant (fatty acid synthase, Fas2Δ/Δ) of the emerging human pathogenic yeast Candida parapsilosis dies after incubation in various media including serum. In the present study we describe the mechanism for cell death induced by serum and glucose containing media. We show that Fas2Δ/Δ yeast cells are profoundly susceptible to glucose leading us to propose that yeast cells lacking fatty acids exhibit uncontrolled metabolism in response to glucose. We demonstrate that incubation of Fas2Δ/Δ yeast cells with serum leads to cell death, and this process can be prevented with inhibition of protein or DNA synthesis, indicating that newly synthesized cellular components are detrimental to the mutant cells. Furthermore, we have found that cell death is mediated by mitochondria. Suppression of electron transport enzymes using inhibitors such as cyanide or azide prevents ROS overproduction and Fas2Δ/Δ yeast cell death. Additionally, deletion of mitochondrial DNA, which encodes several subunits for enzymes of the electron transport chain, significantly reduces serum-induced Fas2Δ/Δ yeast cell death. Therefore, our results show that serum and glucose media induce Fas2Δ/Δ yeast cell death by triggering unbalanced metabolism, which is regulated by mitochondria. To our knowledge, this is the first study to critically define a link between cytosolic fatty acid synthesis and mitochondrial function in response to serum stress in C. parapsilosis. Candida parapsilosis is a human opportunistic pathogen associated with significant morbidity and mortality, especially in immunocompromised individuals such as premature, low-birthweight neonates. Our prior studies have indicated that C. parapsilosis effectively utilizes fatty acids/lipids for growth and virulence. We now show that inhibition of the fatty acid synthase (Fas2) results in a hypersensitivity to serum, indicating that yeast cell survival and replication in serum medium or in vivo is dependent on Fas2. Serum hypersensitivity of Fas2-inhibited yeast cells is due to mitochondrial mediated dysregulation of metabolism. Thus, we conclude that Fas2 is candidate antifungal target to combat disseminated fungal infections.
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Affiliation(s)
- Long Nam Nguyen
- Department of Medicine (Division of Infectious Diseases), Albert Einstein College of Medicine, New York, New York, United States of America
- Signature Research Program in Cardiovascular & Metabolic Disorders, DUKE-NUS Graduate Medical School, Singapore
- * E-mail: (LNN); (JDN)
| | - Gabriele Vargas Cesar
- Laboratório de Estudos Integrados em Bioquímica Microbiana, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Giang Thi Thu Le
- University of Hamburg, Biocenter Klein Flottbek, Department of Molecular Phytopathology and Genetics, Hamburg, Germany
| | - David L. Silver
- Signature Research Program in Cardiovascular & Metabolic Disorders, DUKE-NUS Graduate Medical School, Singapore
| | - Leonardo Nimrichter
- Laboratório de Estudos Integrados em Bioquímica Microbiana, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Joshua D. Nosanchuk
- Department of Medicine (Division of Infectious Diseases), Albert Einstein College of Medicine, New York, New York, United States of America
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, New York, United States of America
- * E-mail: (LNN); (JDN)
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Moir RD, Gross DA, Silver DL, Willis IM. SCS3 and YFT2 link transcription of phospholipid biosynthetic genes to ER stress and the UPR. PLoS Genet 2012; 8:e1002890. [PMID: 22927826 PMCID: PMC3426550 DOI: 10.1371/journal.pgen.1002890] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 06/19/2012] [Indexed: 11/21/2022] Open
Abstract
The ability to store nutrients in lipid droplets (LDs) is an ancient function that provides the primary source of metabolic energy during periods of nutrient insufficiency and between meals. The Fat storage-Inducing Transmembrane (FIT) proteins are conserved ER–resident proteins that facilitate fat storage by partitioning energy-rich triglycerides into LDs. FIT2, the ancient ortholog of the FIT gene family first identified in mammals has two homologs in Saccharomyces cerevisiae (SCS3 and YFT2) and other fungi of the Saccharomycotina lineage. Despite the coevolution of these genes for more than 170 million years and their divergence from higher eukaryotes, SCS3, YFT2, and the human FIT2 gene retain some common functions: expression of the yeast genes in a human embryonic kidney cell line promotes LD formation, and expression of human FIT2 in yeast rescues the inositol auxotrophy and chemical and genetic phenotypes of strains lacking SCS3. To better understand the function of SCS3 and YFT2, we investigated the chemical sensitivities of strains deleted for either or both genes and identified synthetic genetic interactions against the viable yeast gene-deletion collection. We show that SCS3 and YFT2 have shared and unique functions that connect major biosynthetic processes critical for cell growth. These include lipid metabolism, vesicular trafficking, transcription of phospholipid biosynthetic genes, and protein synthesis. The genetic data indicate that optimal strain fitness requires a balance between phospholipid synthesis and protein synthesis and that deletion of SCS3 and YFT2 impacts a regulatory mechanism that coordinates these processes. Part of this mechanism involves a role for SCS3 in communicating changes in the ER (e.g. due to low inositol) to Opi1-regulated transcription of phospholipid biosynthetic genes. We conclude that SCS3 and YFT2 are required for normal ER membrane biosynthesis in response to perturbations in lipid metabolism and ER stress. The ability to form lipid droplets is a conserved property of eukaryotic cells that allows the storage of excess metabolic energy in a form that can be readily accessed. In adipose tissue, the storage of excess calories in lipid droplets normally protects other tissues from lipotoxicity and insulin resistance, but this protection is lost with chronic over-nutrition. The FAT storage-inducing transmembrane (FIT) proteins were recently identified as a conserved family of proteins that reside in the lipid bilayer of the endoplasmic reticulum and are implicated in lipid droplet formation. In this work we show that specific functions of the FIT proteins are conserved between yeast and humans and that SCS3 and YFT2, the yeast homologs of mammalian FIT2, are part of a large genetic interaction network connecting lipid metabolism, vesicle trafficking, transcription, and protein synthesis. From these interactions we determined that yeast strains lacking SCS3 and YFT2 are defective in their response to chronic ER stress and cannot induce the unfolded protein response pathway or transcription of phospholipid biosynthetic genes in low inositol. Our findings suggest that the mammalian FIT genes may play an important role in ER stress pathways, which are linked to obesity and type 2 diabetes.
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Affiliation(s)
- Robyn D. Moir
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David A. Gross
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke–NUS Graduate Medical School Singapore, Singapore, Singapore
| | - David L. Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke–NUS Graduate Medical School Singapore, Singapore, Singapore
- * E-mail: (IMW); (DLS)
| | - Ian M. Willis
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail: (IMW); (DLS)
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39
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Miranda DA, Silver DL. Fat storage‐inducing Transmembrane Protein 2 adipose tissue deficiency results in decreased adipose tissue mass. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.594.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Diego A Miranda
- Program in Cardiovascular and Metabolic DiseasesDuke-NUS Graduate Medical SchoolSingaporeSingapore
| | - David L Silver
- Program in Cardiovascular and Metabolic DiseasesDuke-NUS Graduate Medical SchoolSingaporeSingapore
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40
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Gross DA, Zhan C, Silver DL. Biochemical Mechanism of FIT Proteins in Mediating Lipid Droplet Formation. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.594.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- David A. Gross
- Department of BiochemistryAlbert Einstein College of MedicineBronxNY
- Program in Cardiovascular and Metabolic DiseasesDuke-NUS Graduate Medical SchoolSingaporeSingapore
| | - Chenyang Zhan
- Department of BiochemistryAlbert Einstein College of MedicineBronxNY
| | - David L. Silver
- Department of BiochemistryAlbert Einstein College of MedicineBronxNY
- Program in Cardiovascular and Metabolic DiseasesDuke-NUS Graduate Medical SchoolSingaporeSingapore
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41
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Berger JH, Silver DL. Major Facilitator Superfamily Domain‐containing protein 2a is a novel regulator of hepatic lipid metabolism. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.790.13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Justin H Berger
- Department of BiochemistryAlbert Einstein College of MedicineBronxNY
| | - David L Silver
- Program in Cardiovascular and Metabolic DiseasesDuke-NUS Graduate Medical SchoolSingaporeSingapore
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42
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Silver DL. The Function of FIT Proteins in Triglyceride Storage. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.104.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- David L Silver
- Program in Cardiovascular and Metabolic DiseasesDuke-National University of SingaporeOutramSingapore
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43
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Miranda DA, Koves TR, Gross DA, Chadt A, Al-Hasani H, Cline GW, Schwartz GJ, Muoio DM, Silver DL. Re-patterning of skeletal muscle energy metabolism by fat storage-inducing transmembrane protein 2. J Biol Chem 2011; 286:42188-42199. [PMID: 22002063 DOI: 10.1074/jbc.m111.297127] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Triacylglyceride stored in cytosolic lipid droplets (LDs) constitutes a major energy reservoir in most eukaryotes. The regulated turnover of triacylglyceride in LDs provides fatty acids for mitochondrial β-oxidation and ATP generation in physiological states of high demand for energy. The mechanisms for the formation of LDs in conditions of energy excess are not entirely understood. Fat storage-inducing transmembrane protein 2 (FIT2/FITM2) is the anciently conserved member of the fat storage-inducing transmembrane family of proteins implicated to be important in the formation of LDs, but its role in energy metabolism has not been tested. Here, we report that expression of FIT2 in mouse skeletal muscle had profound effects on muscle energy metabolism. Mice with skeletal muscle-specific overexpression of FIT2 (CKF2) had significantly increased intramyocellular triacylglyceride and complete protection from high fat diet-induced weight gain due to increased energy expenditure. Mass spectrometry-based metabolite profiling suggested that CKF2 skeletal muscle had increased oxidation of branched chain amino acids but decreased oxidation of fatty acids. Glucose was primarily utilized in CKF2 muscle for synthesis of the glycerol backbone of triacylglyceride and not for glycogen production. CKF2 muscle was ATP-deficient and had activated AMP kinase. Together, these studies indicate that FIT2 expression in skeletal muscle plays an unexpected function in regulating muscle energy metabolism and indicates an important role for lipid droplet formation in this process.
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Affiliation(s)
- Diego A Miranda
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Timothy R Koves
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, North Carolina 27704
| | - David A Gross
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Alexandra Chadt
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, 40225 Dusseldorf, Germany
| | - Hadi Al-Hasani
- Institute for Clinical Biochemistry and Pathobiochemistry, German Diabetes Center, 40225 Dusseldorf, Germany
| | - Gary W Cline
- Diabetes Endocrinology Research Center, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Gary J Schwartz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Deborah M Muoio
- Sarah W. Stedman Nutrition and Metabolism Center, Department of Medicine, Duke University, Durham, North Carolina 27704
| | - David L Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461.
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Shimizu T, Sugiura T, Wakayama T, Kijima A, Nakamichi N, Iseki S, Silver DL, Kato Y. PDZK1 Regulates Breast Cancer Resistance Protein in Small Intestine. Drug Metab Dispos 2011; 39:2148-54. [DOI: 10.1124/dmd.111.040295] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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Takeuchi K, Sugiura T, Umeda S, Matsubara K, Horikawa M, Nakamichi N, Silver DL, Ishiwata N, Kato Y. Pharmacokinetics and hepatic uptake of eltrombopag, a novel platelet-increasing agent. Drug Metab Dispos 2011; 39:1088-96. [PMID: 21422191 DOI: 10.1124/dmd.110.037960] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Eltrombopag (ELT) is a novel thrombopoietin receptor agonist for the treatment of idiopathic thrombocytopenic purpura. Previous reports indicate that ELT is mainly eliminated in the liver, although its pharmacokinetic profile has not yet been clarified in detail. The purpose of the present study is to investigate the overall elimination mechanism of ELT. After intravenous administration of ELT to rats, approximately 40% of unchanged ELT was excreted into the bile in 72 h, whereas less than 0.02% of the dose was excreted in urine, indicating that liver is the major elimination organ for ELT. The total clearance was much lower than the hepatic blood flow rate and comparable with hepatic uptake clearance obtained from integration plot analysis. Coadministration of rifampicin, an organic anion transporter inhibitor, reduced both total clearance and hepatic uptake clearance of ELT. These results suggest that hepatic uptake is the rate-limiting process in the overall elimination of ELT. To further characterize the uptake mechanism, uptake of ELT by freshly isolated mouse hepatocytes was examined. The ELT uptake showed concentration and energy dependence and was inhibited by various compounds, including not only organic anions but also organic cations. Hepatic uptake clearance in vivo was reduced by coadministration of an organic cation, tetrapentylammonium. Finally, uptake of ELT was observed in human embryonic kidney 293 cells transfected with human hepatic transporters organic anion-transporting polypeptide (OATP) 1B1 and OATP2B1 and organic cation transporter OCT1. These results suggest that multiple transporters, including organic anion transporters and organic cation transporters, are involved in hepatic ELT uptake.
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Affiliation(s)
- Kazuya Takeuchi
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan
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Nagajyothi F, Weiss LM, Silver DL, Desruisseaux MS, Scherer PE, Herz J, Tanowitz HB. Trypanosoma cruzi utilizes the host low density lipoprotein receptor in invasion. PLoS Negl Trop Dis 2011; 5:e953. [PMID: 21408103 PMCID: PMC3051337 DOI: 10.1371/journal.pntd.0000953] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 01/05/2011] [Indexed: 11/23/2022] Open
Abstract
Background Trypanosoma cruzi, an intracellular protozoan parasite that infects humans and other mammalian hosts, is the etiologic agent in Chagas disease. This parasite can invade a wide variety of mammalian cells. The mechanism(s) by which T. cruzi invades its host cell is not completely understood. The activation of many signaling receptors during invasion has been reported; however, the exact mechanism by which parasites cross the host cell membrane barrier and trigger fusion of the parasitophorous vacuole with lysosomes is not understood. Methodology/Principal Findings In order to explore the role of the Low Density Lipoprotein receptor (LDLr) in T. cruzi invasion, we evaluated LDLr parasite interactions using immunoblot and immunofluorescence (IFA) techniques. These experiments demonstrated that T. cruzi infection increases LDLr levels in infected host cells, inhibition or disruption of LDLr reduces parasite load in infected cells, T. cruzi directly binds recombinant LDLr, and LDLr-dependent T. cruzi invasion requires PIP2/3. qPCR analysis demonstrated a massive increase in LDLr mRNA (8000 fold) in the heart of T. cruzi infected mice, which is observed as early as 15 days after infection. IFA shows a co-localization of both LDL and LDLr with parasites in infected heart. Conclusions/Significance These data highlight, for the first time, that LDLr is involved in host cell invasion by this parasite and the subsequent fusion of the parasitophorous vacuole with the host cell lysosomal compartment. The model suggested by this study unifies previous models of host cell invasion for this pathogenic protozoon. Overall, these data indicate that T. cruzi targets LDLr and its family members during invasion. Binding to LDL likely facilitates parasite entry into host cells. The observations in this report suggest that therapeutic strategies based on the interaction of T. cruzi and the LDLr pathway should be pursued as possible targets to modify the pathogenesis of disease following infection. Trypanosoma cruzi, an intracellular protozoan parasite that causes Chagas disease in humans and results in the development of cardiomyopathy, is a major health problem in endemic areas. This parasite can invade a wide variety of mammalian cells. The mechanisms by which these parasites invade their host cells are not completely understood. Our study highlights, for the first time, that the Low Density Lipoprotein receptor (LDLr) is important in the invasion and the subsequent fusion of the parasitophorous vacuole with host lysosomes. We demonstrate that T. cruzi directly binds to LDLr, and inhibition or disruption of LDLr significantly decreases parasite entry. Additionally, we have determined that this cross-linking triggers the accumulation of LDLr and phosphotidylinositol phosphates in coated pits, which initiates a signaling cascade that results in the recruitment of lysosomes, possibly via the sorting motif in the cytoplasmic tail of LDLr, to the site of adhesion/invasion. Studies of infected CD1 mice demonstrate that LDLs accumulate in infected heart and that LDLr co-localize with internalized parasites. Overall, this study demonstrates that LDLr and its family members, engaged mainly in lipoprotein transportation, are also involved in T. cruzi entry into host cells and this interaction likely contributes to the progression of chronic cardiomyopathy.
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Affiliation(s)
- Fnu Nagajyothi
- Department of Pathology, Albert Einstein College of Medicine, Bronx, New York, USA.
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Sugiura T, Otake T, Shimizu T, Wakayama T, Silver DL, Utsumi R, Nishimura T, Iseki S, Nakamichi N, Kubo Y, Tsuji A, Kato Y. PDZK1 regulates organic anion transporting polypeptide Oatp1a in mouse small intestine. Drug Metab Pharmacokinet 2010; 25:588-98. [PMID: 21084765 DOI: 10.2133/dmpk.dmpk-10-rg-074] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent studies indicate that various members of the organic anion transporting polypeptide (OATP) family are expressed on apical membranes of the small intestine. In the present study, we investigated possible interaction of Oatp with the PDZ protein PDZK1 in mouse small intestine, using [³H]estrone-3-sulfate (E3S) as a typical substrate. After intraduodenal administration, the level of [³H]E3S appearing in the portal vein of pdzk1 gene knockout (pdzk1(-/-)) mice was much lower than that in wild-type mice. Lower intestinal absorption of [³H]E3S in pdzk1(-/-) mice was confirmed in Ussing-type chamber experiments, which showed smaller uptake of [³H]E3S from the apical side in intestinal tissues of pdzk1(-/-) mice compared with wild-type mice. The kinetics and inhibition profile of [³H]E3S uptake in the Ussing-type chamber were similar to those in HEK293 cells stably expressing Oatp1a5, suggesting involvement of Oatp1a5 in [³H]E3S uptake. Immunoreactivity to anti-Oatp1a antibody was colocalized with PDZK1 in the small intestine of wild-type mice, whereas apical localization of Oatp1a protein was reduced in pdzk1(-/-) mice. An immunoprecipitation study revealed physical interaction of PDZK1 with Oatp1a. Thus, PDZK1 appears to act as an adaptor for Oatp1a. This is the first demonstration of a regulatory protein directly interacting with small-intestinal OATP.
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Affiliation(s)
- Tomoko Sugiura
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan
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Gross DA, Snapp EL, Silver DL. Structural insights into triglyceride storage mediated by fat storage-inducing transmembrane (FIT) protein 2. PLoS One 2010; 5:e10796. [PMID: 20520733 PMCID: PMC2875400 DOI: 10.1371/journal.pone.0010796] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 05/03/2010] [Indexed: 11/19/2022] Open
Abstract
Fat storage-Inducing Transmembrane proteins 1 & 2 (FIT1/FITM1 and FIT2/FITM2) belong to a unique family of evolutionarily conserved proteins localized to the endoplasmic reticulum that are involved in triglyceride lipid droplet formation. FIT proteins have been shown to mediate the partitioning of cellular triglyceride into lipid droplets, but not triglyceride biosynthesis. FIT proteins do not share primary sequence homology with known proteins and no structural information is available to inform on the mechanism by which FIT proteins function. Here, we present the experimentally-solved topological models for FIT1 and FIT2 using N-glycosylation site mapping and indirect immunofluorescence techniques. These methods indicate that both proteins have six-transmembrane-domains with both N- and C-termini localized to the cytosol. Utilizing this model for structure-function analysis, we identified and characterized a gain-of-function mutant of FIT2 (FLL(157-9)AAA) in transmembrane domain 4 that markedly augmented the total number and mean size of lipid droplets. Using limited-trypsin proteolysis we determined that the FLL(157-9)AAA mutant has enhanced trypsin cleavage at K86 relative to wild-type FIT2, indicating a conformational change. Taken together, these studies indicate that FIT2 is a 6 transmembrane domain-containing protein whose conformation likely regulates its activity in mediating lipid droplet formation.
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Affiliation(s)
- David A. Gross
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Erik L. Snapp
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - David L. Silver
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Sugiura T, Kato Y, Wakayama T, Silver DL, Kubo Y, Iseki S, Tsuji A. PDZK1 Regulates Two Intestinal Solute Carriers (Slc15a1 and Slc22a5) in Mice. Drug Metab Dispos 2008; 36:1181-8. [DOI: 10.1124/dmd.107.020321] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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50
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Zhu W, Saddar S, Seetharam D, Chambliss KL, Longoria C, Silver DL, Yuhanna IS, Shaul PW, Mineo C. The scavenger receptor class B type I adaptor protein PDZK1 maintains endothelial monolayer integrity. Circ Res 2008; 102:480-7. [PMID: 18174467 DOI: 10.1161/circresaha.107.159079] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Circulating levels of high-density lipoprotein (HDL) cholesterol are inversely related to the risk of cardiovascular disease, and HDL and the HDL receptor scavenger receptor class B type I (SR-BI) initiate signaling in endothelium through src that promotes endothelial NO synthase activity and cell migration. Such signaling requires the C-terminal PDZ-interacting domain of SR-BI. Here we show that the PDZ domain-containing protein PDZK1 is expressed in endothelium and required for HDL activation of endothelial NO synthase and cell migration; in contrast, endothelial cell responses to other stimuli, including vascular endothelial growth factor, are PDZK1-independent. Coimmunoprecipitation experiments reveal that Src interacts with SR-BI, and this process is PDZK1-independent. PDZK1 also does not regulate SR-BI abundance or plasma membrane localization in endothelium or HDL binding or cholesterol efflux. Alternatively, PDZK1 is required for HDL/SR-BI to induce Src phosphorylation. Paralleling the in vitro findings, carotid artery reendothelialization following perivascular electric injury is absent in PDZK1-/- mice, and this phenotype persists in PDZK1-/- mice with genetic reconstitution of PDZK1 expression in liver, where PDZK1 modifies SR-BI abundance. Thus, PDZK1 is uniquely required for HDL/SR-BI signaling in endothelium, and through these mechanisms, it is critically involved in the maintenance of endothelial monolayer integrity.
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Affiliation(s)
- Weifei Zhu
- Division of Pulmonary and Vascular Biology, Department of Pediatrics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas, USA
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