1
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Platt FM. The expanding boundaries of sphingolipid lysosomal storage diseases; insights from Niemann-Pick disease type C. Biochem Soc Trans 2023; 51:1777-1787. [PMID: 37844193 PMCID: PMC10657176 DOI: 10.1042/bst20220711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 10/04/2023] [Accepted: 10/06/2023] [Indexed: 10/18/2023]
Abstract
Lysosomal storage diseases are inborn errors of metabolism that arise due to loss of function mutations in genes encoding lysosomal enzymes, protein co-factors or lysosomal membrane proteins. As a consequence of the genetic defect, lysosomal function is impaired and substrates build up in the lysosome leading to 'storage'. A sub group of these disorders are the sphingolipidoses in which sphingolipids accumulate in the lysosome. In this review, I will discuss how the study of these rare lysosomal disorders reveals unanticipated links to other rare and common human diseases using Niemann-Pick disease type C as an example.
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Affiliation(s)
- Frances M. Platt
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, U.K
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2
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Ralhan I, Chang J, Moulton MJ, Goodman LD, Lee NY, Plummer G, Pasolli HA, Matthies D, Bellen HJ, Ioannou MS. Autolysosomal exocytosis of lipids protect neurons from ferroptosis. J Cell Biol 2023; 222:e202207130. [PMID: 37036445 PMCID: PMC10098143 DOI: 10.1083/jcb.202207130] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/25/2022] [Accepted: 03/20/2023] [Indexed: 04/11/2023] Open
Abstract
During oxidative stress neurons release lipids that are internalized by glia. Defects in this coordinated process play an important role in several neurodegenerative diseases. Yet, the mechanisms of lipid release and its consequences on neuronal health are unclear. Here, we demonstrate that lipid-protein particle release by autolysosome exocytosis protects neurons from ferroptosis, a form of cell death driven by lipid peroxidation. We show that during oxidative stress, peroxidated lipids and iron are released from neurons by autolysosomal exocytosis which requires the exocytic machinery VAMP7 and syntaxin 4. We observe membrane-bound lipid-protein particles by TEM and demonstrate that these particles are released from neurons using cryoEM. Failure to release these lipid-protein particles causes lipid hydroperoxide and iron accumulation and sensitizes neurons to ferroptosis. Our results reveal how neurons protect themselves from peroxidated lipids. Given the number of brain pathologies that involve ferroptosis, defects in this pathway likely play a key role in the pathophysiology of neurodegenerative disease.
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Affiliation(s)
- Isha Ralhan
- Department of Physiology, University of Alberta, Edmonton, Canada
- Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Canada
| | - Jinlan Chang
- Department of Physiology, University of Alberta, Edmonton, Canada
| | - Matthew J. Moulton
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, USA
| | - Lindsey D. Goodman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, USA
| | - Nathanael Y.J. Lee
- Department of Physiology, University of Alberta, Edmonton, Canada
- Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Canada
| | - Greg Plummer
- Faculty of Medicine & Dentistry Cell Imaging Core, University of Alberta, Edmonton, Canada
| | - H. Amalia Pasolli
- Electron Microscopy Resource Center, The Rockefeller University, New York, NY, USA
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Doreen Matthies
- Unit on Structural Biology, Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Hugo J. Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Maria S. Ioannou
- Department of Physiology, University of Alberta, Edmonton, Canada
- Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Canada
- Department of Cell Biology, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
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3
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Xicota L, Lagarde J, Eysert F, Grenier-Boley B, Rivals I, Botté A, Forlani S, Landron S, Gautier C, Gabriel C, Bottlaender M, Lambert JC, Chami M, Sarazin M, Potier MC. Modifications of the endosomal compartment in fibroblasts from sporadic Alzheimer's disease patients are associated with cognitive impairment. Transl Psychiatry 2023; 13:54. [PMID: 36788216 PMCID: PMC9929231 DOI: 10.1038/s41398-023-02355-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 01/31/2023] [Accepted: 02/03/2023] [Indexed: 02/16/2023] Open
Abstract
Morphological alterations of the endosomal compartment have been widely described in post-mortem brains from Alzheimer's disease (AD) patients and subjects with Down syndrome (DS) who are at high risk for AD. Immunostaining with antibodies against endosomal markers such as Early Endosome Antigen 1 (EEA1) revealed increased size of EEA1-positive puncta. In DS, peripheral cells such as peripheral blood mononuclear cells (PBMCs) and fibroblasts, share similar phenotype even in the absence of AD. We previously found that PBMCs from AD patients have larger EEA1-positive puncta, correlating with brain amyloid load. Here we analysed the endosomal compartment of fibroblasts from a very well characterised cohort of AD patients (IMABio3) who underwent thorough clinical, imaging and biomarkers assessments. Twenty-one subjects were included (7 AD with mild cognitive impairment (AD-MCI), 7 AD with dementia (AD-D) and 7 controls) who had amyloid-PET at baseline (PiB) and neuropsychological tests at baseline and close to skin biopsy. Fibroblasts isolated from skin biopsies were immunostained with anti-EEA1 antibody and imaged using a spinning disk microscope. Endosomal compartment ultrastructure was also analysed by electron microscopy. All fibroblast lines were genotyped and their AD risk factors identified. Our results show a trend to an increased EEA1-positive puncta volume in fibroblasts from AD-D as compared to controls (p.adj = 0.12) and reveal enhanced endosome area in fibroblasts from AD-MCI and AD-AD versus controls. Larger puncta size correlated with PiB retention in different brain areas and with worse cognitive scores at the time of biopsy as well as faster decline from baseline to the time of biopsy. Finally, we identified three genetic risk factors for AD (ABCA1, COX7C and MYO15A) that were associated with larger EEA1 puncta volume. In conclusion, the endosomal compartment in fibroblasts could be used as cellular peripheral biomarker for both amyloid deposition and cognitive decline in AD patients.
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Affiliation(s)
- Laura Xicota
- ICM Paris Brain Institute, CNRS UMR7225, INSERM U1127, Sorbonne University, Hôpital de la Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France.
| | - Julien Lagarde
- grid.414435.30000 0001 2200 9055Department of Neurology of Memory and Language, GHU Paris Psychiatrie & Neurosciences, Hôpital Sainte Anne, F-75014 Paris, France ,grid.508487.60000 0004 7885 7602Université Paris Cité, F-75006 Paris, France ,Université Paris-Saclay, BioMaps, Service Hospitalier Frederic Joliot CEA, CNRS, Inserm, F-91401 Orsay, France
| | - Fanny Eysert
- Institut of Molecular and Cellular Pharmacology, Laboratory of Excellence DistALZ, Université Côte d’Azur, INSERM, CNRS, Sophia-Antipolis, F-06560 Valbonne, France
| | - Benjamin Grenier-Boley
- grid.503422.20000 0001 2242 6780Univ. Lille, Inserm, CHU Lille, Institut Pasteur de Lille, U1167-RIDAGE– Facteurs de risque et déterminants moléculaires des maladies liées au vieillissement, F-59000 Lille, France
| | - Isabelle Rivals
- grid.440907.e0000 0004 1784 3645Equipe de Statistique Appliquée, ESPCI Paris, INSERM, UMRS 1158 Neurophysiologie Respiratoire Expérimentale et Clinique, PSL Research University, Paris, France
| | - Alexandra Botté
- grid.411439.a0000 0001 2150 9058ICM Paris Brain Institute, CNRS UMR7225, INSERM U1127, Sorbonne University, Hôpital de la Pitié-Salpêtrière, 47 Bd de l’Hôpital, 75013 Paris, France
| | - Sylvie Forlani
- grid.411439.a0000 0001 2150 9058ICM DNA and Cell Bank CNRS UMR7225, INSERM U1127, Sorbonne University, Hôpital de la Pitié-Salpêtrière, 47 Bd de l’Hôpital, 75013 Paris, France
| | - Sophie Landron
- Institut de Recherche Servier, 125 Chem. de Ronde, 78290 Croissy sur Seine, France
| | - Clément Gautier
- Institut de Recherche Servier, 125 Chem. de Ronde, 78290 Croissy sur Seine, France
| | - Cecilia Gabriel
- Institut de Recherche Servier, 125 Chem. de Ronde, 78290 Croissy sur Seine, France
| | - Michel Bottlaender
- grid.508487.60000 0004 7885 7602Université Paris Cité, F-75006 Paris, France ,grid.460789.40000 0004 4910 6535CEA, Neurospin, UNIACT, Paris Saclay University, 91191 Gif-sur-Yvette Cedex, France
| | - Jean-Charles Lambert
- grid.503422.20000 0001 2242 6780Univ. Lille, Inserm, CHU Lille, Institut Pasteur de Lille, U1167-RIDAGE– Facteurs de risque et déterminants moléculaires des maladies liées au vieillissement, F-59000 Lille, France
| | - Mounia Chami
- Institut of Molecular and Cellular Pharmacology, Laboratory of Excellence DistALZ, Université Côte d’Azur, INSERM, CNRS, Sophia-Antipolis, F-06560 Valbonne, France
| | - Marie Sarazin
- grid.414435.30000 0001 2200 9055Department of Neurology of Memory and Language, GHU Paris Psychiatrie & Neurosciences, Hôpital Sainte Anne, F-75014 Paris, France ,grid.508487.60000 0004 7885 7602Université Paris Cité, F-75006 Paris, France ,Université Paris-Saclay, BioMaps, Service Hospitalier Frederic Joliot CEA, CNRS, Inserm, F-91401 Orsay, France
| | - Marie-Claude Potier
- ICM Paris Brain Institute, CNRS UMR7225, INSERM U1127, Sorbonne University, Hôpital de la Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France.
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4
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Linking Late Endosomal Cholesterol with Cancer Progression and Anticancer Drug Resistance. Int J Mol Sci 2022; 23:ijms23137206. [PMID: 35806209 PMCID: PMC9267071 DOI: 10.3390/ijms23137206] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 06/22/2022] [Accepted: 06/25/2022] [Indexed: 11/16/2022] Open
Abstract
Cancer cells undergo drastic metabolic adaptions to cover increased bioenergetic needs, contributing to resistance to therapies. This includes a higher demand for cholesterol, which often coincides with elevated cholesterol uptake from low-density lipoproteins (LDL) and overexpression of the LDL receptor in many cancers. This implies the need for cancer cells to accommodate an increased delivery of LDL along the endocytic pathway to late endosomes/lysosomes (LE/Lys), providing a rapid and effective distribution of LDL-derived cholesterol from LE/Lys to other organelles for cholesterol to foster cancer growth and spread. LDL-cholesterol exported from LE/Lys is facilitated by Niemann–Pick Type C1/2 (NPC1/2) proteins, members of the steroidogenic acute regulatory-related lipid transfer domain (StARD) and oxysterol-binding protein (OSBP) families. In addition, lysosomal membrane proteins, small Rab GTPases as well as scaffolding proteins, including annexin A6 (AnxA6), contribute to regulating cholesterol egress from LE/Lys. Here, we summarize current knowledge that links upregulated activity and expression of cholesterol transporters and related proteins in LE/Lys with cancer growth, progression and treatment outcomes. Several mechanisms on how cellular distribution of LDL-derived cholesterol from LE/Lys influences cancer cell behavior are reviewed, some of those providing opportunities for treatment strategies to reduce cancer progression and anticancer drug resistance.
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5
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Juhl AD, Wüstner D. Pathways and Mechanisms of Cellular Cholesterol Efflux-Insight From Imaging. Front Cell Dev Biol 2022; 10:834408. [PMID: 35300409 PMCID: PMC8920967 DOI: 10.3389/fcell.2022.834408] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/04/2022] [Indexed: 12/24/2022] Open
Abstract
Cholesterol is an essential molecule in cellular membranes, but too much cholesterol can be toxic. Therefore, mammalian cells have developed complex mechanisms to remove excess cholesterol. In this review article, we discuss what is known about such efflux pathways including a discussion of reverse cholesterol transport and formation of high-density lipoprotein, the function of ABC transporters and other sterol efflux proteins, and we highlight their role in human diseases. Attention is paid to the biophysical principles governing efflux of sterols from cells. We also discuss recent evidence for cholesterol efflux by the release of exosomes, microvesicles, and migrasomes. The role of the endo-lysosomal network, lipophagy, and selected lysosomal transporters, such as Niemann Pick type C proteins in cholesterol export from cells is elucidated. Since oxysterols are important regulators of cellular cholesterol efflux, their formation, trafficking, and secretion are described briefly. In addition to discussing results obtained with traditional biochemical methods, focus is on studies that use established and novel bioimaging approaches to obtain insight into cholesterol efflux pathways, including fluorescence and electron microscopy, atomic force microscopy, X-ray tomography as well as mass spectrometry imaging.
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Affiliation(s)
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, PhyLife, Physical Life Sciences, University of Southern Denmark, Odense, Denmark
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6
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HDL and Lipid Metabolism. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1377:49-61. [DOI: 10.1007/978-981-19-1592-5_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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7
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Butyrylcholinesterase-Protein Interactions in Human Serum. Int J Mol Sci 2021; 22:ijms221910662. [PMID: 34639003 PMCID: PMC8508650 DOI: 10.3390/ijms221910662] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/24/2021] [Accepted: 09/28/2021] [Indexed: 11/17/2022] Open
Abstract
Measuring various biochemical and cellular components in the blood is a routine procedure in clinical practice. Human serum contains hundreds of diverse proteins secreted from all cells and tissues in healthy and diseased states. Moreover, some serum proteins have specific strong interactions with other blood components, but most interactions are probably weak and transient. One of the serum proteins is butyrylcholinesterase (BChE), an enzyme existing mainly as a glycosylated soluble tetramer that plays an important role in the metabolism of many drugs. Our results suggest that BChE interacts with plasma proteins and forms much larger complexes than predicted from the molecular weight of the BChE tetramer. To investigate and isolate such complexes, we developed a two-step strategy to find specific protein–protein interactions by combining native size-exclusion chromatography (SEC) with affinity chromatography with the resin that specifically binds BChE. Second, to confirm protein complexes′ specificity, we fractionated blood serum proteins by density gradient ultracentrifugation followed by co-immunoprecipitation with anti-BChE monoclonal antibodies. The proteins coisolated in complexes with BChE were identified by mass spectroscopy. These binding studies revealed that BChE interacts with a number of proteins in the human serum. Some of these interactions seem to be more stable than transient. BChE copurification with ApoA-I and the density of some fractions containing BChE corresponding to high-density lipoprotein cholesterol (HDL) during ultracentrifugation suggest its interactions with HDL. Moreover, we observed lower BChE plasma activity in individuals with severely reduced HDL levels (≤20 mg/dL). The presented two-step methodology for determination of the BChE interactions can facilitate further analysis of such complexes, especially from the brain tissue, where BChE could be involved in the pathogenesis and progression of AD.
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8
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Tavares LA, Januário YC, daSilva LLP. HIV-1 Hijacking of Host ATPases and GTPases That Control Protein Trafficking. Front Cell Dev Biol 2021; 9:622610. [PMID: 34307340 PMCID: PMC8295591 DOI: 10.3389/fcell.2021.622610] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 06/07/2021] [Indexed: 12/22/2022] Open
Abstract
The human immunodeficiency virus (HIV-1) modifies the host cell environment to ensure efficient and sustained viral replication. Key to these processes is the capacity of the virus to hijack ATPases, GTPases and the associated proteins that control intracellular protein trafficking. The functions of these energy-harnessing enzymes can be seized by HIV-1 to allow the intracellular transport of viral components within the host cell or to change the subcellular distribution of antiviral factors, leading to immune evasion. Here, we summarize how energy-related proteins deviate from their normal functions in host protein trafficking to aid the virus in different phases of its replicative cycle. Recent discoveries regarding the interplay among HIV-1 and host ATPases and GTPases may shed light on potential targets for pharmacological intervention.
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Affiliation(s)
- Lucas A Tavares
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Yunan C Januário
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Luis L P daSilva
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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9
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Colaco A, Kaya E, Adriaenssens E, Davis LC, Zampieri S, Fernández‐Suárez ME, Tan CY, Deegan PB, Porter FD, Galione A, Bembi B, Dardis A, Platt FM. Mechanistic convergence and shared therapeutic targets in Niemann-Pick disease. J Inherit Metab Dis 2020; 43:574-585. [PMID: 31707734 PMCID: PMC7317544 DOI: 10.1002/jimd.12191] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 10/31/2019] [Accepted: 11/08/2019] [Indexed: 01/07/2023]
Abstract
Niemann-Pick disease type C (NPC) and Tangier disease are genetically and clinically distinct rare inborn errors of metabolism. NPC is caused by defects in either NPC1 or NPC2; whereas Tangier disease is caused by a defect in ABCA1. Tangier disease is currently without therapy, whereas NPC can be treated with miglustat, a small molecule inhibitor of glycosphingolipid biosynthesis that slows the neurological course of the disease. When a Tangier disease patient was misdiagnosed with NPC and treated with miglustat, her symptoms improved. This prompted us to consider whether there is mechanistic convergence between these two apparently unrelated rare inherited metabolic diseases. In this study, we found that when ABCA1 is defective (Tangier disease) there is secondary inhibition of the NPC disease pathway, linking these two diseases at the level of cellular pathophysiology. In addition, this study further supports the hypothesis that miglustat, as well as other substrate reduction therapies, may be potential therapeutic agents for treating Tangier disease as fibroblasts from multiple Tangier patients were corrected by miglustat treatment.
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Affiliation(s)
| | - Ecem Kaya
- Department of PharmacologyUniversity of OxfordOxfordUK
| | | | | | | | | | - Chong Y. Tan
- Lysosomal Disorders UnitAddenbrooke's HospitalCambridgeUK
| | | | - Forbes D. Porter
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIHBethesdaMaryland
| | | | - Bruno Bembi
- University Hospital Santa Maria della MisericordiaUdineItaly
| | - Andrea Dardis
- University Hospital Santa Maria della MisericordiaUdineItaly
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10
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Lake NJ, Taylor RL, Trahair H, Harikrishnan KN, Curran JE, Almeida M, Kulkarni H, Mukhamedova N, Hoang A, Low H, Murphy AJ, Johnson MP, Dyer TD, Mahaney MC, Göring HHH, Moses EK, Sviridov D, Blangero J, Jowett JBM, Bozaoglu K. TRAK2, a novel regulator of ABCA1 expression, cholesterol efflux and HDL biogenesis. Eur Heart J 2019; 38:3579-3587. [PMID: 28655204 DOI: 10.1093/eurheartj/ehx315] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 05/25/2017] [Indexed: 12/28/2022] Open
Abstract
Aims The recent failures of HDL-raising therapies have underscored our incomplete understanding of HDL biology. Therefore there is an urgent need to comprehensively investigate HDL metabolism to enable the development of effective HDL-centric therapies. To identify novel regulators of HDL metabolism, we performed a joint analysis of human genetic, transcriptomic, and plasma HDL-cholesterol (HDL-C) concentration data and identified a novel association between trafficking protein, kinesin binding 2 (TRAK2) and HDL-C concentration. Here we characterize the molecular basis of the novel association between TRAK2 and HDL-cholesterol concentration. Methods and results Analysis of lymphocyte transcriptomic data together with plasma HDL from the San Antonio Family Heart Study (n = 1240) revealed a significant negative correlation between TRAK2 mRNA levels and HDL-C concentration, HDL particle diameter and HDL subspecies heterogeneity. TRAK2 siRNA-mediated knockdown significantly increased cholesterol efflux to apolipoprotein A-I and isolated HDL from human macrophage (THP-1) and liver (HepG2) cells by increasing the mRNA and protein expression of the cholesterol transporter ATP-binding cassette, sub-family A member 1 (ABCA1). The effect of TRAK2 knockdown on cholesterol efflux was abolished in the absence of ABCA1, indicating that TRAK2 functions in an ABCA1-dependent efflux pathway. TRAK2 knockdown significantly increased liver X receptor (LXR) binding at the ABCA1 promoter, establishing TRAK2 as a regulator of LXR-mediated transcription of ABCA1. Conclusion We show, for the first time, that TRAK2 is a novel regulator of LXR-mediated ABCA1 expression, cholesterol efflux, and HDL biogenesis. TRAK2 may therefore be an important target in the development of anti-atherosclerotic therapies.
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Affiliation(s)
- Nicole J Lake
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia.,Murdoch Children's Research Institute, 50 Flemington Road, Parkville, VIC 3052, Australia
| | - Rachael L Taylor
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Hugh Trahair
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - K N Harikrishnan
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia.,Department of Pathology, University of Melbourne, Grattan Street, Parkville, VIC 3010, Australia
| | - Joanne E Curran
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Marcio Almeida
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Hemant Kulkarni
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Nigora Mukhamedova
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Anh Hoang
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Hann Low
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Andrew J Murphy
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Matthew P Johnson
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Thomas D Dyer
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Michael C Mahaney
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Harald H H Göring
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Eric K Moses
- University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.,Curtin University, Kent St, Bentley, WA 6102, Australia
| | - Dmitri Sviridov
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - John Blangero
- South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley School of Medicine, One West University Blvd. Brownsville, Texas 78520, USA
| | - Jeremy B M Jowett
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia
| | - Kiymet Bozaoglu
- Baker IDI Heart and Diabetes Institute, 75 Commercial Road, Melbourne, VIC 3004, Australia.,Murdoch Children's Research Institute, 50 Flemington Road, Parkville, VIC 3052, Australia.,Department of Paediatrics, University of Melbourne, 50 Flemington Road, Parkville,VIC 3052, Australia
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11
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Schultz ML, Fawaz MV, Azaria RD, Hollon TC, Liu EA, Kunkel TJ, Halseth TA, Krus KL, Ming R, Morin EE, McLoughlin HS, Bushart DD, Paulson HL, Shakkottai VG, Orringer DA, Schwendeman AS, Lieberman AP. Synthetic high-density lipoprotein nanoparticles for the treatment of Niemann-Pick diseases. BMC Med 2019; 17:200. [PMID: 31711490 PMCID: PMC6849328 DOI: 10.1186/s12916-019-1423-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 09/10/2019] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Niemann-Pick disease type C is a fatal and progressive neurodegenerative disorder characterized by the accumulation of unesterified cholesterol in late endosomes and lysosomes. We sought to develop new therapeutics for this disorder by harnessing the body's endogenous cholesterol scavenging particle, high-density lipoprotein (HDL). METHODS Here we design, optimize, and define the mechanism of action of synthetic HDL (sHDL) nanoparticles. RESULTS We demonstrate a dose-dependent rescue of cholesterol storage that is sensitive to sHDL lipid and peptide composition, enabling the identification of compounds with a range of therapeutic potency. Peripheral administration of sHDL to Npc1 I1061T homozygous mice mobilizes cholesterol, reduces serum bilirubin, reduces liver macrophage size, and corrects body weight deficits. Additionally, a single intraventricular injection into adult Npc1 I1061T brains significantly reduces cholesterol storage in Purkinje neurons. Since endogenous HDL is also a carrier of sphingomyelin, we tested the same sHDL formulation in the sphingomyelin storage disease Niemann-Pick type A. Utilizing stimulated Raman scattering microscopy to detect endogenous unlabeled lipids, we show significant rescue of Niemann-Pick type A lipid storage. CONCLUSIONS Together, our data establish that sHDL nanoparticles are a potential new therapeutic avenue for Niemann-Pick diseases.
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Affiliation(s)
- Mark L Schultz
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA
| | - Maria V Fawaz
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Ruth D Azaria
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA
| | - Todd C Hollon
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Elaine A Liu
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA
- Cellular and Molecular Biology Graduate Program, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Thaddeus J Kunkel
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA
| | - Troy A Halseth
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Kelsey L Krus
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA
| | - Ran Ming
- Department of Pharmaceutical Sciences, University of Michigan College of Pharmacy, B20-102W NCRC, 2800 Plymouth Road, Ann Arbor, MI, 48109, USA
| | - Emily E Morin
- Department of Pharmaceutical Sciences, University of Michigan College of Pharmacy, B20-102W NCRC, 2800 Plymouth Road, Ann Arbor, MI, 48109, USA
| | - Hayley S McLoughlin
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - David D Bushart
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Henry L Paulson
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Daniel A Orringer
- Department of Neurosurgery, University of Michigan Medical School, Ann Arbor, MI, 48109, USA
| | - Anna S Schwendeman
- Department of Pharmaceutical Sciences, University of Michigan College of Pharmacy, B20-102W NCRC, 2800 Plymouth Road, Ann Arbor, MI, 48109, USA.
- Biointerfaces Institute, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Andrew P Lieberman
- Department of Pathology, University of Michigan Medical School, 3510 MSRB1, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA.
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12
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Seeree P, Janvilisri T, Kangsamaksin T, Tohtong R, Kumkate S. Downregulation of ABCA1 and ABCG1 transporters by simvastatin in cholangiocarcinoma cells. Oncol Lett 2019; 18:5173-5184. [PMID: 31612028 PMCID: PMC6781495 DOI: 10.3892/ol.2019.10874] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 08/13/2019] [Indexed: 02/06/2023] Open
Abstract
Disturbances in cholesterol homeostasis of the bile duct epithelium, including transport interruption and the hyperaccumulation of intracellular cholesterol can lead to the initiation and progression of cholangiocarcinoma (CCA). Statins, which are lipid-lowering drugs, have been previously documented to exhibit anti-cancer properties. The role of statins in CCA cell cholesterol transport through the expression and function of ATP-binding cassette (ABC) A1 and ABCG1 was investigated in the current study. In four CCA cell lines, ABCA1 and ABCG1 expression was identified. However, neither ABCG5 nor ABCG8 expression was observed. Immunocytochemistry revealed that the expression of ABCA1 was localized in the proximity of the nucleus, while ABCG1 was more dispersed throughout the cytoplasm of KKU-100 cells. A cholesterol efflux assay was performed using bodipy cholesterol, and the translocation of cholesterol via ABCA1 and ABCG1 to Apo-A1 and high density lipoprotein was confirmed, respectively. Simvastatin and atorvastatin demonstrated the inhibitory effects on CCA cell viability. A reduction in intracellular lipid level and a lower expression of ABCA1 and ABCG1 were observed in KKU-100 cells under simvastatin treatment. The pre-exposure of KKU-100 cells to cholesterol diminished the statin effect. Furthermore, when KKU-100 cells were pre-loaded with cholesterol, ABCA1 and ABCG1-mediated exports were unaffected even though they were treated with simvastatin. The results of the current study indicated the limitations of the use of statin in CCA therapy, particularly under hypercholesterolemia conditions.
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Affiliation(s)
- Pattaya Seeree
- Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Tavan Janvilisri
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Thaned Kangsamaksin
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Rutaiwan Tohtong
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Supeecha Kumkate
- Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
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13
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Lorkowski SW, Brubaker G, Gulshan K, Smith JD. V-ATPase (Vacuolar ATPase) Activity Required for ABCA1 (ATP-Binding Cassette Protein A1)-Mediated Cholesterol Efflux. Arterioscler Thromb Vasc Biol 2019; 38:2615-2625. [PMID: 30354238 DOI: 10.1161/atvbaha.118.311814] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective- We have shown that ABCA1 (ATP-binding cassette protein A1) mediates unfolding of the apoA1 (apolipoprotein A1) N-terminal helical hairpin during apoA1 lipidation. Others have shown that an acidic pH exposes the hydrophobic surface of apoA1. We postulated that the V-ATPase (vacuolar ATPase) proton pump facilitates apoA1 unfolding and promotes ABCA1-mediated cholesterol efflux. Approach and Results- We found that V-ATPase inhibitors dose-dependently decreased ABCA1-mediated cholesterol efflux to apoA1 in baby hamster kidney cells and RAW264.7 cells; and similarly, siRNA knockdown of ATP6V0C inhibited ABCA1-mediated cholesterol efflux to apoA1 in RAW264.7 cells. Although ABCA1 expression did not alter total cellular levels of V-ATPase, ABCA1 increased the cell surface levels of the V0A1 and V1E1 subunits of V-ATPase. We generated a fluorescein isothiocyanate/Alexa647 double-labeled fluorescent ratiometric apoA1 pH indicator whose fluorescein isothiocyanate/Alexa647 emission ratio decreased as the pH drops. We found that ABCA1 induction in baby hamster kidney cells led to acidification of the cell-associated apoA1 pH indicator, compared with control cells without ABCA1 expression. The V-ATPase inhibitor bafilomycin A1 dose-dependently inhibited the apoA1 pH shift in ABCA1-expressing cells, without affecting the levels of cell-associated apoA1. However, we were not able to detect ABCA1-mediated extracellular proton release. We showed that acidic pH facilitated apoA1 unfolding, apoA1 solubilization of phosphatidycholine:phosphatidyserine liposomes, and increased lipid fluidity of these liposomes. Conclusions- Our results support a model that ABCA1 recruits V-ATPase to the plasma membrane where V-ATPase mediates apoA1 acidification and membrane remodeling that promote apoA1 unfolding and ABCA1-mediated HDL (high-density lipoprotein) biogenesis and lipid efflux.
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Affiliation(s)
- Shuhui Wang Lorkowski
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Gregory Brubaker
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Kailash Gulshan
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH
| | - Jonathan D Smith
- From the Department of Cellular and Molecular Medicine (S.W.L., G.B., K.G., J.D.S.), Cleveland Clinic, OH.,Department of Cardiovascular Medicine (J.D.S.), Cleveland Clinic, OH
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14
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Neufeld EB, Sato M, Gordon SM, Durbhakula V, Francone N, Aponte A, Yilmaz G, Sviridov D, Sampson M, Tang J, Pryor M, Remaley AT. ApoA-I-Mediated Lipoprotein Remodeling Monitored with a Fluorescent Phospholipid. BIOLOGY 2019; 8:E53. [PMID: 31336888 PMCID: PMC6784057 DOI: 10.3390/biology8030053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/01/2019] [Accepted: 07/08/2019] [Indexed: 01/10/2023]
Abstract
We describe simple, sensitive and robust methods to monitor lipoprotein remodeling and cholesterol and apolipoprotein exchange, using fluorescent Lissamine Rhodamine B head-group tagged phosphatidylethanolamine (*PE) as a lipoprotein reference marker. Fluorescent Bodipy cholesterol (*Chol) and *PE directly incorporated into whole plasma lipoproteins in proportion to lipoprotein cholesterol and phospholipid mass, respectively. *Chol, but not *PE, passively exchanged between isolated plasma lipoproteins. Fluorescent apoA-I (*apoA-I) specifically bound to high-density lipoprotein (HDL) and remodeled *PE- and *Chol-labeled synthetic lipoprotein-X multilamellar vesicles (MLV) into a pre-β HDL-like particle containing *PE, *Chol, and *apoA-I. Fluorescent MLV-derived *PE specifically incorporated into plasma HDL, whereas MLV-derived *Chol incorporation into plasma lipoproteins was similar to direct *Chol incorporation, consistent with apoA-I-mediated remodeling of fluorescent MLV to HDL with concomitant exchange of *Chol between lipoproteins. Based on these findings, we developed a model system to study lipid transfer by depositing fluorescent *PE and *Chol-labeled on calcium silicate hydrate crystals, forming dense lipid-coated donor particles that are readily separated from acceptor lipoprotein particles by low-speed centrifugation. Transfer of *PE from donor particles to mouse plasma lipoproteins was shown to be HDL-specific and apoA-I-dependent. Transfer of donor particle *PE and *Chol to HDL in whole human plasma was highly correlated. Taken together, these studies suggest that cell-free *PE efflux monitors apoA-I functionality.
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Affiliation(s)
- Edward B Neufeld
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Masaki Sato
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Scott M Gordon
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vinay Durbhakula
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nicolas Francone
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Angel Aponte
- Proteomics Core, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Gizem Yilmaz
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Denis Sviridov
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Maureen Sampson
- Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jingrong Tang
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Milton Pryor
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alan T Remaley
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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15
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Hu J, Yang Q, Chen Z, Liang W, Feng J, Ding G. Small GTPase Arf6 regulates diabetes-induced cholesterol accumulation in podocytes. J Cell Physiol 2019; 234:23559-23570. [PMID: 31206670 DOI: 10.1002/jcp.28924] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 05/19/2019] [Accepted: 05/20/2019] [Indexed: 12/29/2022]
Abstract
Podocyte injury is a critical factor for the initiation and progression of diabetic kidney disease (DKD). However, the underlying mechanisms of podocyte injury in DKD have not been completely elucidated. Studies suggested that intracellular cholesterol accumulation was correlated with podocyte injury, but the cause of podocyte cholesterol disorders in DKD are still unknown. ADP-ribosylation factor 6 (Arf6) is a small GTPase with pleiotropic effects and has previously been shown to regulate ATP-binding cassette transporter 1 (ABCA1) recycling, and thus, cholesterol homeostasis. However, Arf6 involvement in cholesterol metabolism in podocytes is scarce. To investigate the role of Arf6 in cholesterol modulation in podocytes, the effect of Arf6 on the regulation of the cholesterol transporter ABCA1 was studied in podocytes in vivo and in vitro. Intracellular cholesterol accumulation was significantly increased in podocytes from streptozotocin-induced diabetic rats and that hyperglycemia downregulated the expression of Arf6. Arf6 knockdown could cause ABCA1 recycling disorders, and thus, further aggravate cholesterol accumulation in podocytes under high-glucose (HG) conditions. Our results demonstrate that HG-induced cholesterol accumulation and cellular injury in podocytes may be related to the recycling disorder of ABCA1 caused by the downexpression of Arf6 in DKD.
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Affiliation(s)
- Jijia Hu
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Qian Yang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhaowei Chen
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Wei Liang
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Jun Feng
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Guohua Ding
- Division of Nephrology, Renmin Hospital of Wuhan University, Wuhan, China
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16
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Impairment of trophoblast survival and differentiation by LXR ligands is prevented by cholesterol but not ABCA1 silencing. Placenta 2018; 69:50-56. [DOI: 10.1016/j.placenta.2018.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 07/02/2018] [Accepted: 07/06/2018] [Indexed: 01/31/2023]
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17
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Intracellular and Plasma Membrane Events in Cholesterol Transport and Homeostasis. J Lipids 2018; 2018:3965054. [PMID: 30174957 PMCID: PMC6106919 DOI: 10.1155/2018/3965054] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 07/26/2018] [Indexed: 12/13/2022] Open
Abstract
Cholesterol transport between intracellular compartments proceeds by both energy- and non-energy-dependent processes. Energy-dependent vesicular traffic partly contributes to cholesterol flux between endoplasmic reticulum, plasma membrane, and endocytic vesicles. Membrane contact sites and lipid transfer proteins are involved in nonvesicular lipid traffic. Only “active" cholesterol molecules outside of cholesterol-rich regions and partially exposed in water phase are able to fast transfer. The dissociation of partially exposed cholesterol molecules in water determines the rate of passive aqueous diffusion of cholesterol out of plasma membrane. ATP hydrolysis with concomitant conformational transition is required to cholesterol efflux by ABCA1 and ABCG1 transporters. Besides, scavenger receptor SR-B1 is involved also in cholesterol efflux by facilitated diffusion via hydrophobic tunnel within the molecule. Direct interaction of ABCA1 with apolipoprotein A-I (apoA-I) or apoA-I binding to high capacity binding sites in plasma membrane is important in cholesterol escape to free apoA-I. ABCG1-mediated efflux to fully lipidated apoA-I within high density lipoprotein particle proceeds more likely through the increase of “active” cholesterol level. Putative cholesterol-binding linear motifs within the structure of all three proteins ABCA1, ABCG1, and SR-B1 are suggested to contribute to the binding and transfer of cholesterol molecules from cytoplasmic to outer leaflets of lipid bilayer. Together, plasma membrane events and intracellular cholesterol metabolism and traffic determine the capacity of the cell for cholesterol efflux.
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18
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Phillips MC. Is ABCA1 a lipid transfer protein? J Lipid Res 2018; 59:749-763. [PMID: 29305383 DOI: 10.1194/jlr.r082313] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/02/2018] [Indexed: 12/16/2022] Open
Abstract
ABCA1 functions as a lipid transporter because it mediates the transfer of cellular phospholipid (PL) and free (unesterified) cholesterol (FC) to apoA-I and related proteins present in the extracellular medium. ABCA1 is a membrane PL translocase and its enzymatic activity leads to transfer of PL molecules from the cytoplasmic leaflet to the exofacial leaflet of a cell plasma membrane (PM). The presence of active ABCA1 in the PM promotes binding of apoA-I to the cell surface. About 10% of this bound apoA-I interacts directly with ABCA1 and stabilizes the transporter. Most of the pool of cell surface-associated apoA-I is bound to lipid domains in the PM that are created by the activity of ABCA1. The amphipathic α-helices in apoA-I confer detergent-like properties on the protein enabling it to solubilize PL and FC in these membrane domains to create a heterogeneous population of discoidal nascent HDL particles. This review focuses on current understanding of the structure-function relationships of human ABCA1 and the molecular mechanisms underlying HDL particle production.
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Affiliation(s)
- Michael C Phillips
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-5158
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19
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Haerian BS, Haerian MS, Roohi A, Mehrad-Majd H. ABCA1 genetic polymorphisms and type 2 diabetes mellitus and its complications. Meta Gene 2017. [DOI: 10.1016/j.mgene.2017.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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20
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O'Sullivan A, Henrick B, Dixon B, Barile D, Zivkovic A, Smilowitz J, Lemay D, Martin W, German JB, Schaefer SE. 21st century toolkit for optimizing population health through precision nutrition. Crit Rev Food Sci Nutr 2017; 58:3004-3015. [PMID: 28678528 DOI: 10.1080/10408398.2017.1348335] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Scientific, technological, and economic progress over the last 100 years all but eradicated problems of widespread food shortage and nutrient deficiency in developed nations. But now society is faced with a new set of nutrition problems related to energy imbalance and metabolic disease, which require new kinds of solutions. Recent developments in the area of new analytical tools enable us to systematically study large quantities of detailed and multidimensional metabolic and health data, providing the opportunity to address current nutrition problems through an approach called Precision Nutrition. This approach integrates different kinds of "big data" to expand our understanding of the complexity and diversity of human metabolism in response to diet. With these tools, we can more fully elucidate each individual's unique phenotype, or the current state of health, as determined by the interactions among biology, environment, and behavior. The tools of precision nutrition include genomics, metabolomics, microbiomics, phenotyping, high-throughput analytical chemistry techniques, longitudinal tracking with body sensors, informatics, data science, and sophisticated educational and behavioral interventions. These tools are enabling the development of more personalized and predictive dietary guidance and interventions that have the potential to transform how the public makes food choices and greatly improve population health.
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Affiliation(s)
| | - Bethany Henrick
- b Foods for Health Institute , University of California , Davis , USA
| | - Bonnie Dixon
- b Foods for Health Institute , University of California , Davis , USA
| | - Daniela Barile
- c Food Science and Technology , University of California , Davis , USA
| | - Angela Zivkovic
- d Department of Nutrition , University of California , Davis , USA
| | - Jennifer Smilowitz
- b Foods for Health Institute , University of California , Davis , USA.,e USDA-ARS Western Human Nutrition Research Center , Davis , USA
| | - Danielle Lemay
- f Nutritional Biology , University of California , Davis , USA
| | | | - J Bruce German
- h Department of Food Science and Technology , University of California , Davis , USA
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21
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Tomioka M, Toda Y, Mañucat NB, Akatsu H, Fukumoto M, Kono N, Arai H, Kioka N, Ueda K. Lysophosphatidylcholine export by human ABCA7. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:658-665. [PMID: 28373057 DOI: 10.1016/j.bbalip.2017.03.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Revised: 03/27/2017] [Accepted: 03/29/2017] [Indexed: 10/19/2022]
Abstract
The ATP-binding cassette transporter A7 (ABCA7), which is highly expressed in the brain, is associated with the pathogenesis of Alzheimer's disease (AD). However, the physiological function of ABCA7 and its transport substrates remain unclear. Immunohistochemical analyses of human brain sections from AD and non-AD subjects revealed that ABCA7 is expressed in neuron and microglia cells in the cerebral cortex. The transport substrates and acceptors were identified in BHK/ABCA7 cells and compared with those of ABCA1. Like ABCA1, ABCA7 exported choline phospholipids in the presence of apoA-I and apoE; however, unlike ABCA1, cholesterol efflux was marginal. Lipid efflux by ABCA7 was saturated by 5μg/ml apoA-I and was not dependent on apoE isoforms, whereas efflux by ABCA1 was dependent on apoA-I up to 20μg/ml and apoE isoforms. Liquid chromatography-tandem mass spectrometry analyses revealed that the two proteins had different preferences for phospholipid export: ABCA7 preferred phosphatidylcholine (PC)≥lysoPC>sphingomyelin (SM)=phosphatidylethanolamine (PE), whereas ABCA1 preferred PC>>SM>PE=lysoPC. The major difference in the pattern of lipid peaks between ABCA7 and ABCA1 was the high lysoPC/PC ratio of ABCA7. These results suggest that lysoPC is one of the major transport substrates for ABCA7 and that lysoPC export may be a physiologically important function of ABCA7 in the brain.
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Affiliation(s)
- Maiko Tomioka
- Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinobu Toda
- Faculty of Health Care, Tenri Health Care University, Tenri, Nara 632-0018, Japan.
| | - Noralyn B Mañucat
- Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroyasu Akatsu
- Graduate School of Medical Sciences and Medical School, Nagoya City University, Nagoya 467-8601, Japan
| | - Manabu Fukumoto
- Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Miyagi 980-8575, Japan
| | - Nozomu Kono
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hiroyuki Arai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Noriyuki Kioka
- Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan; Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Kazumitsu Ueda
- Institute for integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto 606-8502, Japan; Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
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22
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Jin X, Sviridov D, Liu Y, Vaisman B, Addadi L, Remaley AT, Kruth HS. ABCA1 (ATP-Binding Cassette Transporter A1) Mediates ApoA-I (Apolipoprotein A-I) and ApoA-I Mimetic Peptide Mobilization of Extracellular Cholesterol Microdomains Deposited by Macrophages. Arterioscler Thromb Vasc Biol 2016; 36:2283-2291. [PMID: 27758769 DOI: 10.1161/atvbaha.116.308334] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 09/02/2016] [Indexed: 11/16/2022]
Abstract
OBJECTIVE We examined the function of ABCA1 (ATP-binding cassette transporter A1) in ApoA-I (apolipoprotein A-I) mobilization of cholesterol microdomains deposited into the extracellular matrix by cholesterol-enriched macrophages. We have also determined whether an ApoA-I mimetic peptide without and with complexing to sphingomyelin can mobilize macrophage-deposited cholesterol microdomains. APPROACH AND RESULTS Extracellular cholesterol microdomains deposited by cholesterol-enriched macrophages were detected with a monoclonal antibody, 58B1. ApoA-I and an ApoA-I mimetic peptide 5A mobilized cholesterol microdomains deposited by ABCA1+/+ macrophages but not by ABCA1-/- macrophages. In contrast, ApoA-I mimetic peptide 5A complexed with sphingomyelin could mobilize cholesterol microdomains deposited by ABCA1-/- macrophages. CONCLUSIONS Our findings show that a unique pool of extracellular cholesterol microdomains deposited by macrophages can be mobilized by both ApoA-I and an ApoA-I mimetic peptide but that mobilization depends on macrophage ABCA1. It is known that ABCA1 complexes ApoA-I and ApoA-I mimetic peptide with phospholipid, a cholesterol-solubilizing agent, explaining the requirement for ABCA1 in extracellular cholesterol microdomain mobilization. Importantly, ApoA-I mimetic peptide already complexed with phospholipid can mobilize macrophage-deposited extracellular cholesterol microdomains even in the absence of ABCA1.
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Affiliation(s)
- Xueting Jin
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Denis Sviridov
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Ying Liu
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Boris Vaisman
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Lia Addadi
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Alan T Remaley
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.)
| | - Howard S Kruth
- From the Experimental Atherosclerosis Section (X.J., Y.L., H.S.K.) and Lipoprotein Metabolism Section (D.S., B.V., A.T.R.), National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD; and Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel (L.A.).
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Mukhamedova N, Hoang A, Cui HL, Carmichael I, Fu Y, Bukrinsky M, Sviridov D. Small GTPase ARF6 Regulates Endocytic Pathway Leading to Degradation of ATP-Binding Cassette Transporter A1. Arterioscler Thromb Vasc Biol 2016; 36:2292-2303. [PMID: 27758770 DOI: 10.1161/atvbaha.116.308418] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 09/19/2016] [Indexed: 11/16/2022]
Abstract
OBJECTIVE ABCA1 (ATP-binding cassette transporter A1) is the principal protein responsible for cellular cholesterol efflux. Abundance and functionality of ABCA1 is regulated both transcriptionally and post-translationally, with endocytosis of ABCA1 being an important element of post-translational regulation. Functional ABCA1 resides on the plasma membrane but can be internalized and either degraded or recycled back to the plasma membrane. The interaction between the degradative and recycling pathways determines the abundance of ABCA1 and may contribute to the efflux of intracellular cholesterol. APPROACH AND RESULTS Here, we show that the principal pathway responsible for the internalization of ABCA1 leading to its degradation in macrophages is ARF6-dependent endocytic pathway. This pathway was predominant in the regulation of ABCA1 abundance and efflux of plasma membrane cholesterol. Conversely, the efflux of intracellular cholesterol was predominantly controlled by ARF6-independent pathways, and inhibition of ARF6 shifted ABCA1 into recycling endosomes enhancing efflux of intracellular cholesterol. CONCLUSIONS We conclude that ARF6-dependent pathway is the predominant route responsible for the ABCA1 internalization and degradation, whereas ARF6-independent endocytic pathways may contribute to ABCA1 recycling and efflux of intracellular cholesterol.
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Affiliation(s)
- Nigora Mukhamedova
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Anh Hoang
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Huanhuan L Cui
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Irena Carmichael
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Ying Fu
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Michael Bukrinsky
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.)
| | - Dmitri Sviridov
- From the Department of Lipoproteins and Atherosclerosis, Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia (N.M., A.H., H.L.C., I.C., Y.F., D.S.); Department of Medicine, Karolinska Institute, Stockholm, Sweden (H.L.C.); and Department of Microbiology, Immunology and Tropical Medicine, George Washington University School of Medicine and Health Sciences, Washington, DC (M.B.).
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Wang S, Peng DQ, Yi Y. The unsolved mystery of apoA-I recycling in adipocyte. Lipids Health Dis 2016; 15:35. [PMID: 26911989 PMCID: PMC4765186 DOI: 10.1186/s12944-016-0203-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/11/2016] [Indexed: 01/24/2023] Open
Abstract
As the major storage site for triglycerides and free cholesterol, adipose tissue plays a central role in energy metabolism. ApoA-I is the main constituent of HDL and plays an important role in removal of excess cholesterol from peripheral tissues. Recently, multiple studies have shown beneficial effects of apoA-I on adipose metabolism and function. ApoA-I was reported to improve insulin sensitivity and exert anti-inflammatory, anti-obesity effect in animal studies. Interestingly, Uptake and resecretion of apoA-I by adipocytes has been detected. However, the significance of apoA-I recycling by adipocytes is still not clear. This article reviewed methods used to study cellular recycling of apoA-I and summarized the current knowledge on the mechanisms involved in apoA-I uptake by adipocytes. Since the main function of apoA-I is to mediate reverse cholesterol transport from peripheral tissues, the role of apoA-I internalization and re-secretion by adipocytes in intracellular cholesterol transport under physiological and pathological conditions were discussed. In addition, findings on the correlation between apoA-I recycling and obesity were discussed. Finally, it was proposed that during intracellular transport, apoA-I-protein complex may acquire cargoes other than lipids and deliver regulatory information when they were resecreted into the plasma. Although apoA-I recycling by adipocytes is still an unsolved mystery, it's likely that it is more than a redundant pathway especially under pathological conditions.
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Affiliation(s)
- Shuai Wang
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
| | - Dao-quan Peng
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China.
| | - Yuhong Yi
- The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
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A Short Synthetic Peptide Mimetic of Apolipoprotein A1 Mediates Cholesterol and Globotriaosylceramide Efflux from Fabry Fibroblasts. JIMD Rep 2015. [PMID: 26683465 DOI: 10.1007/8904_2015_507] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] Open
Abstract
Fabry disease is an X-linked sphingolipid storage disorder caused by a deficiency of the lysosomal enzyme α-galactosidase A (AGA, EC 3.2.1.22) resulting in the intracellular accumulation of globotriaosylceramide (Gb3). We found that Gb3 storage also correlates with accumulation of endosomal-lysosomal cholesterol in Fabry fibroblasts. This cholesterol accumulation may contribute to the phenotypic pathology of Fabry disease by slowing endosomal-lysosomal trafficking. We found that LDL receptor expression is not downregulated in Fabry fibroblasts resulting in accumulation of both cholesterol and Gb3. 5A-Palmitoyl oleoyl-phosphatidylcholine (5AP) is a phospholipid complex containing a short synthetic peptide that mimics apolipoprotein A1, the main protein component of high-density lipoprotein (HDL) that mediates the efflux of cholesterol from cells via the ATP-binding cassette transporter. We used 5AP and HDL to remove cholesterol from Fabry fibroblasts to examine the fate of accumulated cellular Gb3. Using immunostaining techniques, we found that 5AP is highly effective for depleting cholesterol and Gb3 in these cells. 5AP restores the ApoA-1-mediated cholesterol efflux leading to mobilization of cholesterol and reduction of Gb3 in Fabry fibroblasts.
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26
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Wüstner D, Solanko K. How cholesterol interacts with proteins and lipids during its intracellular transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1908-26. [DOI: 10.1016/j.bbamem.2015.05.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2015] [Revised: 04/14/2015] [Accepted: 05/13/2015] [Indexed: 12/13/2022]
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Platt FM, Wassif C, Colaco A, Dardis A, Lloyd-Evans E, Bembi B, Porter FD. Disorders of cholesterol metabolism and their unanticipated convergent mechanisms of disease. Annu Rev Genomics Hum Genet 2015; 15:173-94. [PMID: 25184529 DOI: 10.1146/annurev-genom-091212-153412] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Cholesterol plays a key role in many cellular processes, and is generated by cells through de novo biosynthesis or acquired from exogenous sources through the uptake of low-density lipoproteins. Cholesterol biosynthesis is a complex, multienzyme-catalyzed pathway involving a series of sequentially acting enzymes. Inherited defects in genes encoding cholesterol biosynthetic enzymes or other regulators of cholesterol homeostasis result in severe metabolic diseases, many of which are rare in the general population and currently without effective therapy. Historically, these diseases have been viewed as discrete disorders, each with its own genetic cause and distinct pathogenic cascades that lead to its specific clinical features. However, studies have recently shown that three of these diseases have an unanticipated mechanistic convergence. This surprising finding is not only shedding light on details of cellular cholesterol homeostasis but also suggesting novel approaches to therapy.
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Affiliation(s)
- Frances M Platt
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom;
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Neufeld EB, O'Brien K, Walts AD, Stonik JA, Malide D, Combs CA, Remaley AT. The Human ABCG1 Transporter Mobilizes Plasma Membrane and Late Endosomal Non-Sphingomyelin-Associated-Cholesterol for Efflux and Esterification. BIOLOGY 2014; 3:866-91. [PMID: 25485894 PMCID: PMC4280515 DOI: 10.3390/biology3040866] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/22/2014] [Accepted: 11/26/2014] [Indexed: 11/16/2022]
Abstract
We have previously shown that GFP-tagged human ABCG1 on the plasma membrane (PM) and in late endosomes (LE) mobilizes sterol on both sides of the membrane lipid bilayer, thereby increasing cellular cholesterol efflux to lipid surfaces. In the present study, we examined ABCG1-induced changes in membrane cholesterol distribution, organization, and mobility. ABCG1-GFP expression increased the amount of mobile, non-sphingomyelin(SM)-associated cholesterol at the PM and LE, but not the amount of SM-associated-cholesterol or SM. ABCG1-mobilized non-SM-associated-cholesterol rapidly cycled between the PM and LE and effluxed from the PM to extracellular acceptors, or, relocated to intracellular sites of esterification. ABCG1 increased detergent-soluble pools of PM and LE cholesterol, generated detergent-resistant, non-SM-associated PM cholesterol, and increased resistance to both amphotericin B-induced (cholesterol-mediated) and lysenin-induced (SM-mediated) cytolysis, consistent with altered organization of both PM cholesterol and SM. ABCG1 itself resided in detergent-soluble membrane domains. We propose that PM and LE ABCG1 residing at the phase boundary between ordered (Lo) and disordered (Ld) membrane lipid domains alters SM and cholesterol organization thereby increasing cholesterol flux between Lo and Ld, and hence, the amount of cholesterol available for removal by acceptors on either side of the membrane bilayer for either efflux or esterification.
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Affiliation(s)
- Edward B Neufeld
- Lipoprotein Metabolism Section, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Katherine O'Brien
- Lipid Trafficking Core, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Avram D Walts
- Lipid Trafficking Core, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - John A Stonik
- Lipoprotein Metabolism Section, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Daniela Malide
- NHLBI Light Microscopy Core Facility, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Christian A Combs
- NHLBI Light Microscopy Core Facility, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Alan T Remaley
- Lipoprotein Metabolism Section, Cardiovascular and Pulmonary Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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29
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Cellular Localization and Trafficking of the Human ABCG1 Transporter. BIOLOGY 2014; 3:781-800. [PMID: 25405320 PMCID: PMC4280511 DOI: 10.3390/biology3040781] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 10/23/2014] [Accepted: 10/28/2014] [Indexed: 11/17/2022]
Abstract
We have developed a suitable heterologous cell expression system to study the localization, trafficking, and site(s) of function of the human ABCG1 transporter. Increased plasma membrane (PM) and late endosomal (LE) cholesterol generated by ABCG1 was removed by lipoproteins and liposomes, but not apoA-I. Delivery of ABCG1 to the PM and LE was required for ABCG1-mediated cellular cholesterol efflux. ABCG1 LEs frequently contacted the PM, providing a collisional mechanism for transfer of ABCG1-mobilized cholesterol, similar to ABCG1-mediated PM cholesterol efflux to lipoproteins. ABCG1-mobilized LE cholesterol also trafficked to the PM by a non-vesicular pathway. Transfer of ABCG1-mobilized cholesterol from the cytoplasmic face of LEs to the PM and concomitant removal of cholesterol from the outer leaflet of the PM bilayer by extracellular acceptors suggests that ABCG1 mobilizes cholesterol on both sides of the lipid bilayer for removal by acceptors. ABCG1 increased uptake of HDL into LEs, consistent with a potential ABCG1-mediated cholesterol efflux pathway involving HDL resecretion. Thus, ABCG1 at the PM mobilizes PM cholesterol and ABCG1 in LE/LYS generates mobile pools of cholesterol that can traffic by both vesicular and non-vesicular pathways to the PM where it can also be transferred to extracellular acceptors with a lipid surface.
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30
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A Comprehensive In Silico Analysis of the Functional and Structural Impact of Nonsynonymous SNPs in the ABCA1 Transporter Gene. CHOLESTEROL 2014; 2014:639751. [PMID: 25215231 PMCID: PMC4156994 DOI: 10.1155/2014/639751] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 07/07/2014] [Accepted: 07/24/2014] [Indexed: 12/24/2022]
Abstract
Disease phenotypes and defects in function can be traced to nonsynonymous single nucleotide polymorphisms (nsSNPs), which are important indicators of action sites and effective potential therapeutic approaches. Identification of deleterious nsSNPs is crucial to characterize the genetic basis of diseases, assess individual susceptibility to disease, determinate molecular and therapeutic targets, and predict clinical phenotypes. In this study using PolyPhen2 and MutPred in silico algorithms, we analyzed the genetic variations that can alter the expression and function of the ABCA1 gene that causes the allelic disorders familial hypoalphalipoproteinemia and Tangier disease. Predictions were validated with published results from in vitro, in vivo, and human studies. Out of a total of 233 nsSNPs, 80 (34.33%) were found deleterious by both methods. Among these 80 deleterious nsSNPs found, 29 (12.44%) rare variants resulted highly deleterious with a probability >0.8. We have observed that mostly variants with verified functional effect in experimental studies are correctly predicted as damage variants by MutPred and PolyPhen2 tools. Still, the controversial results of experimental approaches correspond to nsSNPs predicted as neutral by both methods, or contradictory predictions are obtained for them. A total of seventeen nsSNPs were predicted as deleterious by PolyPhen2, which resulted neutral by MutPred. Otherwise, forty two nsSNPs were predicted as deleterious by MutPred, which resulted neutral by PolyPhen2.
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31
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Akpovi CD, Murphy BD, Erickson RP, Pelletier RM. Dysregulation of testicular cholesterol metabolism following spontaneous mutation of the niemann-pick c1 gene in mice. Biol Reprod 2014; 91:42. [PMID: 25009206 DOI: 10.1095/biolreprod.114.119412] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The Niemann-Pick-type C1 (Npc1) protein mobilizes LDL-derived cholesterol from lysosomes. Npc1 deficiency disease is a panethnic autosomal recessive disorder of intracellular cholesterol trafficking, leading to accumulation of cholesterol in endosomes/lysosomes. This report assesses the effects of a spontaneous inactivating mutation of the Npc1 gene on spermatogenesis and cholesterol homeostasis in mice. We quantified 1) free and esterified cholesterol levels by enzymatic analysis, 2) cholesterol enzymes and transporter protein expression by Western blotting, and 3) the number of Apostain-labeled apoptotic germ cells and apoptosis levels by ELISA in seminiferous tubule-enriched fractions. In wild-type (WT) mice, esterified cholesterol was elevated when Npc1 expression was low during puberty, while in adulthood, the levels were low (P < 0.05) when Npc1 expression was high (P < 0.01). In Npc1-/- mice, free and esterified cholesterol were significantly elevated. The abundance of cholesterol regulatory proteins, HMGR ACAT1, ACAT2, SR-BI, and ABCA1 was significantly higher in Npc1-/- than in WT mice. The level of apoptosis determined by ELISA and the number of Apostain-labeled cells/tubule were higher in Npc1-/- than in WT mice. Circulating testosterone levels in the Npc1-/- males were threefold lower than those observed in the WT. Deleting the Npc1 gene is accompanied by an increase in germ cell apoptosis and compensatory imbalances in the expression of cholesterol enzymatic and transporter factors and is associated with esterified cholesterol accumulation in seminiferous tubules.
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Affiliation(s)
- Casimir D Akpovi
- Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
| | - Bruce D Murphy
- Centre de Recherche en Reproduction Animale, Faculté de Médecine Vétérinaire, Université de Montréal, St.-Hyacinthe, Québec, Canada
| | - Robert P Erickson
- Department of Pediatrics, University of Arizona College of Medicine, Tucson, Arizona
| | - R-Marc Pelletier
- Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, Québec, Canada
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32
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Neefjes J, van der Kant R. Stuck in traffic: an emerging theme in diseases of the nervous system. Trends Neurosci 2014; 37:66-76. [PMID: 24411104 DOI: 10.1016/j.tins.2013.11.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 11/25/2013] [Accepted: 11/27/2013] [Indexed: 12/11/2022]
Abstract
The past decade has seen an explosion of DNA sequencing activities and many mutations and genetic variances underlying neurological and neurodegenerative diseases have been determined. This wealth of genetic data is now placed in molecular pathways revealing the nodes that underlie the disrupted processes. Many mutations in neurological diseases affect proteins controlling endosomal/lysosomal transport. Although the age of onset of these diseases range from juvenile [i.e., Niemann-Pick type C (NPC) and Charcot-Marie-Tooth (CMT) disease] to late onset (Parkinson's and Alzheimer's disease), deregulation of endosomal transport is a common theme. This review summarizes how elucidating the genetic basis for the various neurological diseases has advanced our understanding of the endo-lysosomal system and why the various mutations all translate into similar disease phenotypes.
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Affiliation(s)
- Jacques Neefjes
- Division of Cell Biology, Netherlands Cancer Institute, 1066CX Amsterdam, The Netherlands.
| | - Rik van der Kant
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093, USA.
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33
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Westerterp M, Bochem AE, Yvan-Charvet L, Murphy AJ, Wang N, Tall AR. ATP-Binding Cassette Transporters, Atherosclerosis, and Inflammation. Circ Res 2014; 114:157-70. [DOI: 10.1161/circresaha.114.300738] [Citation(s) in RCA: 184] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Marit Westerterp
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Andrea E. Bochem
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Laurent Yvan-Charvet
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Andrew J. Murphy
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Nan Wang
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
| | - Alan R. Tall
- From the Division of Molecular Medicine, Department of Medicine, Columbia University, New York, NY (M.W., A.E.B., L.Y.-C., A.J.M., N.W., A.R.T.); Departments of Medical Biochemistry (M.W.) and Vascular Medicine (A.E.B.), Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; and Haematopoiesis and Leukocyte Biology, Baker IDI Heart and Diabetes Institute, Melbourne, Australia (A.J.M.)
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Abstract
Cardiovascular disease (CVD) is the leading cause of death globally. For close to four decades, we have known that high density lipoprotein (HDL) levels are inversely correlated with the risk of CVD. HDL is a complex particle that consists of proteins, phospholipids, and cholesterol and has the ability to carry micro-RNAs. HDL is constantly undergoing remodelling throughout its life-span and carries out many functions. This review summarizes many of the different aspects of HDL from its assembly, the receptors it interacts with, along with the functions it performs and how it can be altered in disease. While HDL is a key cholesterol efflux particle, this review highlights the many other important functions of HDL in the innate immune system and details the potential therapeutic uses of HDL outside of CVD.
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Benesh EC, Miller PM, Pfaltzgraff ER, Grega-Larson NE, Hager HA, Sung BH, Qu X, Baldwin HS, Weaver AM, Bader DM. Bves and NDRG4 regulate directional epicardial cell migration through autocrine extracellular matrix deposition. Mol Biol Cell 2013; 24:3496-510. [PMID: 24048452 PMCID: PMC3826988 DOI: 10.1091/mbc.e12-07-0539] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Bves and NDRG4 proteins interact to regulate directional cell movement by mediating cell surface fusion of internalized fibronectin for resecretion. This provides the first evidence of Bves/NDRG4 protein function within subcellular trafficking pathways and explains how the Bves complex diversely influences development, cancer, and repair. Directional cell movement is universally required for tissue morphogenesis. Although it is known that cell/matrix interactions are essential for directional movement in heart development, the mechanisms governing these interactions require elucidation. Here we demonstrate that a novel protein/protein interaction between blood vessel epicardial substance (Bves) and N-myc downstream regulated gene 4 (NDRG4) is critical for regulation of epicardial cell directional movement, as disruption of this interaction randomizes migratory patterns. Our studies show that Bves/NDRG4 interaction is required for trafficking of internalized fibronectin through the “autocrine extracellular matrix (ECM) deposition” fibronectin recycling pathway. Of importance, we demonstrate that Bves/NDRG4-mediated fibronectin recycling is indeed essential for epicardial cell directional movement, thus linking these two cell processes. Finally, total internal reflectance fluorescence microscopy shows that Bves/NDRG4 interaction is required for fusion of recycling endosomes with the basal cell surface, providing a molecular mechanism of motility substrate delivery that regulates cell directional movement. This is the first evidence of a molecular function for Bves and NDRG4 proteins within broader subcellular trafficking paradigms. These data identify novel regulators of a critical vesicle-docking step required for autocrine ECM deposition and explain how Bves facilitates cell-microenvironment interactions in the regulation of epicardial cell–directed movement.
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Affiliation(s)
- Emily C Benesh
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 Department of Pediatric Cardiology, Vanderbilt University School of Medicine, Nashville, TN 37232 Department of Pathology, Vanderbilt University School of Medicine, Nashville, TN 37232 Department of Medicine, Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232 Department of Obstetrics and Gynecology, Washington University in St. Louis, St. Louis, MO 63110
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Jones RJ, Gu D, Bjorklund CC, Kuiatse I, Remaley AT, Bashir T, Vreys V, Orlowski RZ. The novel anticancer agent JNJ-26854165 induces cell death through inhibition of cholesterol transport and degradation of ABCA1. J Pharmacol Exp Ther 2013; 346:381-92. [PMID: 23820125 DOI: 10.1124/jpet.113.204958] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
JNJ-26854165 (serdemetan) has previously been reported to inhibit the function of the E3 ligase human double minute 2, and we initially sought to characterize its activity in models of mantle cell lymphoma (MCL) and multiple myeloma (MM). Serdemetan induced a dose-dependent inhibition of proliferation in both wild-type (wt) and mutant (mut) p53 cell lines, with IC50 values from 0.25 to 3 μM/l, in association with an S phase cell cycle arrest. Caspase-3 activation was primarily seen in wtp53-bearing cells but also occurred in mutp53-bearing cells, albeit to a lesser extent. 293T cells treated with JNJ-26854165 and serdemetan-resistant fibroblasts displayed accumulation of cholesterol within endosomes, a phenotype reminiscent of that seen in the ATP-binding cassette subfamily A member-1 (ABCA1) cholesterol transport disorder, Tangiers disease. MM and MCL cells had decreased cholesterol efflux and electron microscopy demonstrated the accumulation of lipid whorls, confirming the lysosomal storage disease phenotype. JNJ-26854165 induced induction of cholesterol regulatory genes, sterol regulatory element-binding transcription factor-1 and -2, liver X receptors α and β, along with increased expression of Niemann-Pick disease type-C1 and -C2. However, JNJ-26854165 induced enhanced ABCA1 turnover despite enhancing transcription. Finally, ABCA1 depletion resulted in enhanced sensitivity to JNJ-26854165. Overall, these findings support the hypothesis that serdemetan functions in part by inhibiting cholesterol transport and that this pathway is a potential new target for the treatment of MCL and MM.
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Affiliation(s)
- Richard J Jones
- The Department of Lymphoma and Myeloma, The University of Texas MD Anderson Cancer Center, Houston, Texas 77054, USA
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Lv YC, Yin K, Fu YC, Zhang DW, Chen WJ, Tang CK. Posttranscriptional Regulation ofATP-Binding Cassette Transporter A1in Lipid Metabolism. DNA Cell Biol 2013; 32:348-58. [DOI: 10.1089/dna.2012.1940] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- Yun-cheng Lv
- Key Laboratory for Atherosclerology of Hunan Province, Institute of Cardiovascular Research, Life Science Research Center, University of South China, Hengyang, China
- Laboratory of Clinical Anatomy, University of South China, Hengyang, China
| | - Kai Yin
- Key Laboratory for Atherosclerology of Hunan Province, Institute of Cardiovascular Research, Life Science Research Center, University of South China, Hengyang, China
| | - Yu-chang Fu
- Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama
| | - Da-wei Zhang
- Department of Pediatrics and Group on the Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Canada
| | - Wu-jun Chen
- Key Laboratory for Atherosclerology of Hunan Province, Institute of Cardiovascular Research, Life Science Research Center, University of South China, Hengyang, China
| | - Chao-ke Tang
- Key Laboratory for Atherosclerology of Hunan Province, Institute of Cardiovascular Research, Life Science Research Center, University of South China, Hengyang, China
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Smilowitz JT, Zivkovic AM, Wan YJY, Watkins SM, Nording ML, Hammock BD, German JB. Nutritional lipidomics: molecular metabolism, analytics, and diagnostics. Mol Nutr Food Res 2013; 57:1319-35. [PMID: 23818328 DOI: 10.1002/mnfr.201200808] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 04/12/2013] [Accepted: 04/19/2013] [Indexed: 12/25/2022]
Abstract
The field of lipidomics is providing nutritional science a more comprehensive view of lipid intermediates. Lipidomics research takes advantage of the increase in accuracy and sensitivity of mass detection of MS with new bioinformatics toolsets to characterize the structures and abundances of complex lipids. Yet, translating lipidomics to practice via nutritional interventions is still in its infancy. No single instrumentation platform is able to solve the varying analytical challenges of the different molecular lipid species. Biochemical pathways of lipid metabolism remain incomplete and the tools to map lipid compositional data to pathways are still being assembled. Biology itself is dauntingly complex and simply separating biological structures remains a key challenge to lipidomics. Nonetheless, the strategy of combining tandem analytical methods to perform the sensitive, high-throughput, quantitative, and comprehensive analysis of lipid metabolites of very large numbers of molecules is poised to drive the field forward rapidly. Among the next steps for nutrition to understand the changes in structures, compositions, and function of lipid biomolecules in response to diet is to describe their distribution within discrete functional compartments lipoproteins. Additionally, lipidomics must tackle the task of assigning the functions of lipids as signaling molecules, nutrient sensors, and intermediates of metabolic pathways.
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Luquain-Costaz C, Lefai E, Arnal-Levron M, Markina D, Sakaï S, Euthine V, Makino A, Guichardant M, Yamashita S, Kobayashi T, Lagarde M, Moulin P, Delton-Vandenbroucke I. Bis(monoacylglycero)phosphate accumulation in macrophages induces intracellular cholesterol redistribution, attenuates liver-X receptor/ATP-Binding cassette transporter A1/ATP-binding cassette transporter G1 pathway, and impairs cholesterol efflux. Arterioscler Thromb Vasc Biol 2013; 33:1803-11. [PMID: 23788762 DOI: 10.1161/atvbaha.113.301857] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Endosomal signature phospholipid bis(monoacylglycero)phosphate (BMP) has been involved in the regulation of cellular cholesterol homeostasis. Accumulation of BMP is a hallmark of lipid storage disorders and was recently reported as a noticeable feature of oxidized low-density lipoprotein-laden macrophages. This study was designed to delineate the consequences of macrophage BMP accumulation on intracellular cholesterol distribution, metabolism, and efflux and to unravel the underlying molecular mechanisms. APPROACH AND RESULTS We have developed an experimental design to specifically increase BMP content in RAW 264.7 macrophages. After BMP accumulation, cell cholesterol distribution was markedly altered, despite no change in low-density lipoprotein uptake and hydrolysis, cholesterol esterification, or total cell cholesterol content. The expression of cholesterol-regulated genes sterol regulatory element-binding protein 2 and hydroxymethylglutaryl-coenzyme A reductase was decreased by 40%, indicative of an increase of endoplasmic reticulum-associated cholesterol. Cholesterol delivery to plasma membrane was reduced as evidenced by the 20% decrease of efflux by cyclodextrin. Functionally, BMP accumulation reduced cholesterol efflux to both apolipoprotein A1 and high-density lipoprotein by 40% and correlated with a 40% decrease in mRNA contents of ATP-binding cassette transporter A1, ATP-binding cassette transporter G1, and liver-X receptor α and β. Foam cell formation induced by oxidized low-density lipoprotein exposure was exacerbated in BMP-enriched cells. CONCLUSIONS The present work shows for the first time a strong functional link between BMP and cholesterol-regulating genes involved in both intracellular metabolism and efflux. We propose that accumulation of cellular BMP might contribute to the deregulation of cholesterol homeostasis in atheromatous macrophages.
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Affiliation(s)
- Céline Luquain-Costaz
- Université de Lyon, UMR 1060 Inserm, CarMeN, Institut National des Sciences Appliquées-Lyon, Villeurbanne, France
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Lin S, Zhou C, Neufeld E, Wang YH, Xu SW, Lu L, Wang Y, Liu ZP, Li D, Li C, Chen S, Le K, Huang H, Liu P, Moss J, Vaughan M, Shen X. BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein modulates ATP-binding cassette transporter A-1 trafficking and function. Arterioscler Thromb Vasc Biol 2012; 33:e31-8. [PMID: 23220274 DOI: 10.1161/atvbaha.112.300720] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Cell-surface localization and intracellular trafficking are essential for the function of ATP-binding cassette transporter A-1 (ABCA1). However, regulation of these activities is still largely unknown. Brefeldin A, an uncompetitive inhibitor of brefeldin A-inhibited guanine nucleotide-exchange proteins (BIGs), disturbs the intracellular distribution of ABCA1, and thus inhibits cholesterol efflux. This study aimed to define the possible roles of BIGs in regulating ABCA1 trafficking and cholesterol efflux, and further to explore the potential mechanism. METHODS AND RESULTS By vesicle immunoprecipitation, we found that BIG1 was associated with ABCA1 in vesicles preparation from rat liver. BIG1 depletion reduced surface ABCA1 on HepG2 cells, and inhibited by 60% cholesterol release. In contrast, BIG1 overexpression increased surface ABCA1 and cholesterol secretion. With partial restoration of BIG1 through overexpression in BIG1-depleted cells, surface ABCA1 was also restored. Biotinylation and glutathione cleavage revealed that BIG1 small interfering RNA dramatically decreased the internalization and recycling of ABCA1. This novel function of BIG1 was dependent on the guanine nucleotide-exchange activity and achieved through activation of ADP-ribosylation factor 1. CONCLUSIONS BIG1, through its ability to activate ADP-ribosylation factor 1, regulates cell-surface levels and function of ABCA1, indicating a transcription-independent mechanism for controlling ABCA1 action.
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Affiliation(s)
- Sisi Lin
- Laboratory of Pharmacology and Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, No. 132, East Wai-Huan Rd, College Town, Guangzhou 510006, PR China
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Sundaram M, Yao Z. Intrahepatic role of exchangeable apolipoproteins in lipoprotein assembly and secretion. Arterioscler Thromb Vasc Biol 2012; 32:1073-8. [PMID: 22517365 DOI: 10.1161/atvbaha.111.241455] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Exchangeable apolipoproteins, composed mainly of amphipathic α-helices, are associated with various plasma lipoproteins and play an important role in the metabolism of those lipoproteins to which they bind. Accumulating experimental evidence suggests that exchangeable apolipoproteins, such as apoE, apoA-IV, and apoC-III, also play a role intracellularly in facilitating lipid recruitment at different stages of very low-density lipoprotein assembly and trafficking through the endoplasmic reticulum-Golgi secretory compartments. Experimental evidence also suggests that apoA-I may become lipidated intracellularly through mechanisms dependent on or independent of ATP-binding cassette transporter A1. Thus, expression of these secretory proteins may exert an impact on hepatic triglyceride and cholesterol homeostasis during their transit from the endoplasmic reticulum through the Golgi apparatus. This review summarizes findings related to the modulation of intracellular assembly of very low-density lipoprotein and high-density lipoprotein by exchangeable apolipoproteins.
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Affiliation(s)
- Meenakshi Sundaram
- Department of Biochemistry, Microbiology, and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, Ontario, Canada
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Arciello A, De Marco N, Del Giudice R, Guglielmi F, Pucci P, Relini A, Monti DM, Piccoli R. Insights into the fate of the N-terminal amyloidogenic polypeptide of ApoA-I in cultured target cells. J Cell Mol Med 2012; 15:2652-63. [PMID: 21306558 PMCID: PMC4373434 DOI: 10.1111/j.1582-4934.2011.01271.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Apolipoprotein A-I (ApoA-I) is an extracellular lipid acceptor, whose role in cholesterol efflux and high-density lipoprotein formation is mediated by ATP-binding cassette transporter A1 (ABCA1). Nevertheless, some ApoA-I variants are associated to systemic forms of amyloidosis, characterized by extracellular fibril deposition in peripheral organs. Heart amyloid fibrils were found to be mainly constituted by the 93-residue N-terminal fragment of ApoA-I, named [1-93]ApoA-I. In this paper, rat cardiomyoblasts were used as target cells to analyse binding, internalization and intracellular fate of the fibrillogenic polypeptide in comparison to full-length ApoA-I. We provide evidence that the polypeptide: (i) binds to specific sites on cell membrane (K(d) = 5.90 ± 0.70 × 10(-7) M), where it partially co-localizes with ABCA1, as also described for ApoA-I; (ii) is internalized mostly by chlatrin-mediated endocytosis and lipid rafts, whereas ApoA-I is internalized preferentially by chlatrin-coated pits and macropinocytosis and (iii) is rapidly degraded by proteasome and lysosomes, whereas ApoA-I partially co-localizes with recycling endosomes. Vice versa, amyloid fibrils, obtained by in vitro aggregation of [1-93]ApoA-I, were found to be unable to enter the cells. We propose that internalization and intracellular degradation of [1-93]ApoA-I may divert the polypeptide from amyloid fibril formation and contribute to the slow progression and late onset that characterize this pathology.
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Affiliation(s)
- Angela Arciello
- Department of Structural and Functional Biology, University of Naples Federico II, School of Biotechnological Sciences, Naples, Italy
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Zhao GJ, Yin K, Fu YC, Tang CK. The interaction of ApoA-I and ABCA1 triggers signal transduction pathways to mediate efflux of cellular lipids. Mol Med 2012; 18:149-58. [PMID: 22064972 DOI: 10.2119/molmed.2011.00183] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 11/01/2011] [Indexed: 12/17/2022] Open
Abstract
Reverse cholesterol transport (RCT) has been characterized as a crucial step for antiatherosclerosis, which is initiated by ATP-binding cassette A1 (ABCA1) to mediate the efflux of cellular phospholipids and cholesterol to lipid-free apolipoprotein A-I (apoA-I). However, the mechanisms underlying apoA-I/ABCA1 interaction to lead to the lipidation of apoA-I are poorly understood. There are several models proposed for the interaction of apoA-I with ABCA1 as well as the lipidation of apoA-I mediated by ABCA1. ApoA-I increases the levels of ABCA1 protein markedly. In turn, ABCA1 can stabilize apoA-I. The interaction of apoA-I with ABCA1 could activate signaling molecules that modulate posttranslational ABCA1 activity or lipid transport activity. The key signaling molecules in these processes include protein kinase A (PKA), protein kinase C (PKC), Janus kinase 2 (JAK2), Rho GTPases and Ca²⁺, and many factors also could influence the interaction of apoA-I with ABCA1. This review will summarize these mechanisms for the apoA-I interaction with ABCA1 as well as the signal transduction pathways involved in these processes.
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Affiliation(s)
- Guo-Jun Zhao
- Institute of Cardiovascular Research, Key Laboratory for Atherosclerology of Hunan Province, Life Science Research Center, University of South China, Hengyang, China
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Goedeke L, Fernández-Hernando C. Regulation of cholesterol homeostasis. Cell Mol Life Sci 2012; 69:915-30. [PMID: 22009455 PMCID: PMC11114919 DOI: 10.1007/s00018-011-0857-5] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 09/29/2011] [Accepted: 09/29/2011] [Indexed: 01/24/2023]
Abstract
Cholesterol homeostasis is among the most intensely regulated processes in biology. Since its isolation from gallstones at the time of the French Revolution, cholesterol has been extensively studied. Insufficient or excessive cellular cholesterol results in pathological processes including atherosclerosis and metabolic syndrome. Mammalian cells obtain cholesterol from the circulation in the form of plasma lipoproteins or intracellularly, through the synthesis of cholesterol from acetyl coenzyme A (acetyl-CoA). This process is tightly regulated at multiple levels. In this review, we provide an overview of the multiple mechanisms by which cellular cholesterol metabolism is regulated. We also discuss the recent advances in the post-transcriptional regulation of cholesterol homeostasis, including the role of small non-coding RNAs (microRNAs). These novel findings may open new avenues for the treatment of dyslipidemias and cardiovascular diseases.
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Affiliation(s)
- Leigh Goedeke
- Departments of Medicine and Cell Biology, Leon H. Charney Division of Cardiology, New York University School of Medicine, 522 First Avenue, Smilow 703, New York, NY 10016 USA
| | - Carlos Fernández-Hernando
- Departments of Medicine and Cell Biology, Leon H. Charney Division of Cardiology, New York University School of Medicine, 522 First Avenue, Smilow 703, New York, NY 10016 USA
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Abstract
ABC (ATP-binding cassette) proteins actively transport a wide variety of substrates, including peptides, amino acids, sugars, metals, drugs, vitamins and lipids, across extracellular and intracellular membranes. Of the 49 hum an ABC proteins, a significant number are known to mediate the extrusion of lipids from membranes or the flipping of membrane lipids across the bilayer to generate and maintain membrane lipid asymmetry. Typical lipid substrates include phospholipids, sterols, sphingolipids, bile acids and related lipid conjugates. Members of the ABCA subfamily of ABC transporters and other ABC proteins such as ABCB4, ABCG1 and ABCG5/8 implicated in lipid transport play important roles in diverse biological processes such as cell signalling, membrane lipid asymmetry, removal of potentially toxic compounds and metabolites, and apoptosis. The importance of these ABC lipid transporters in cell physiology is evident from the finding that mutations in the genes encoding many of these proteins are responsible for severe inherited diseases. For example, mutations in ABCA1 cause Tangier disease associated with defective efflux of cholesterol and phosphatidylcholine from the plasma membrane to the lipid acceptor protein apoA1 (apolipoprotein AI), mutations in ABCA3 cause neonatal surfactant deficiency associated with a loss in secretion of the lipid pulmonary surfactants from lungs of newborns, mutations in ABCA4 cause Stargardt macular degeneration, a retinal degenerative disease linked to the reduced clearance of retinoid compounds from photoreceptor cells, mutations in ABCA12 cause harlequin and lamellar ichthyosis, skin diseases associated with defective lipid trafficking in keratinocytes, and mutations in ABCB4 and ABCG5/ABCG8 are responsible for progressive intrafamilial hepatic disease and sitosterolaemia associated with defective phospholipid and sterol transport respectively. This chapter highlights the involvement of various mammalian ABC transporters in lipid transport in the context of their role in cell signalling, cellular homoeostasis, apoptosis and inherited disorders.
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Boadu E, Nelson RC, Francis GA. ABCA1-dependent mobilization of lysosomal cholesterol requires functional Niemann-Pick C2 but not Niemann-Pick C1 protein. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:396-404. [PMID: 22179027 DOI: 10.1016/j.bbalip.2011.11.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 10/28/2011] [Accepted: 11/28/2011] [Indexed: 10/14/2022]
Abstract
Niemann-Pick disease type C (NPC) is caused by mutations leading to loss of function of NPC1 or NPC2 proteins, resulting in accumulation of unesterified cholesterol in late endosomes and lysosomes. We previously reported that expression of the ATP-binding cassette transporter A1 (ABCA1) is impaired in human NPC1(-/-) fibroblasts, resulting in reduced HDL particle formation and providing a mechanism for the reduced plasma HDL cholesterol seen in the majority of NPC1 patients. We also found that treatment of NPC1(-/-) fibroblasts with an agonist of liver X-receptor corrects ABCA1 expression and HDL formation and reduces lysosomal cholesterol accumulation. We have confirmed that ABCA1 expression is also reduced in NPC2(-/-) cells, and found that α-HDL particle formation is impaired in these cells. To determine whether selective up-regulation of ABCA1 can correct lysosomal cholesterol accumulation in NPC disease cells and HDL particle formation, we produced and infected NPC1(-/-) and NPC2(-/-) fibroblasts with an adenovirus expressing full-length ABCA1 and enhanced green fluorescent protein (AdABCA1-EGFP). ABCA1-EGFP expression in NPC1(-/-) fibroblasts resulted in normalization of cholesterol efflux to apolipoprotein A-I (apoA-I) and α-HDL particle formation, plus a marked reduction in filipin staining of unesterified cholesterol in late endosomes/lysosomes. In contrast, AdABCA1-EGFP treatment of NPC2(-/-) fibroblasts to normalize ABCA1 expression had no effect on cholesterol efflux to apoA-I or accumulation of excess cholesterol in lysosomes, and only partially corrected α-HDL formation by these cells. These results suggest that correction of ABCA1 expression can bypass the mutation of NPC1 but not NPC2 to mobilize excess cholesterol from late endosomes and lysosomes in NPC disease cells. Expression of ABCA1-EGFP in NPC1(-/-) cells increased cholesterol available for esterification and reduced levels of HMG-CoA reductase protein, effects that were abrogated by co-incubation with apoA-I. A model can be generated in which ABCA1 is able to mobilize cholesterol, to join the intracellular regulatory pool or to be effluxed for HDL particle formation, either directly or indirectly from the lysosomal membrane, but not from the lysosomal lumen. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Affiliation(s)
- Emmanuel Boadu
- Department of Medicine and UBC James Hogg Research Centre, Providence Heart and Lung Institute, University of British Columbia, Vancouver, Canada
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Zhong JK, Guo ZG, Li C, Wang ZK, Lai WY, Tu Y. Probucol alleviates atherosclerosis and improves high density lipoprotein function. Lipids Health Dis 2011; 10:210. [PMID: 22078494 PMCID: PMC3253062 DOI: 10.1186/1476-511x-10-210] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2011] [Accepted: 11/12/2011] [Indexed: 12/19/2022] Open
Abstract
Background Probucol is a unique hypolipidemic agent that decreases high density lipoprotein cholesterol (HDL-C). However, it is not definite that whether probucol hinders the progression of atherosclerosis by improving HDL function. Methods Eighteen New Zealand White rabbits were randomly divided into the control, atherosclerosis and probucol groups. Control group were fed a regular diet; the atherosclerosis group received a high fat diet, and the probucol group received the high fat diet plus probucol. Hepatocytes and peritoneal macrophages were isolated for [3H] labeled cholesterol efflux rates and expression of ABCA1 and SR-B1 at gene and protein levels; venous blood was collected for serum paraoxonase 1, myeloperoxidase activity and lipid analysis. Aorta were prepared for morphologic and immunohistochemical analysis after 12 weeks. Results Compared to the atherosclerosis group, the paraoxonase 1 activity, cholesterol efflux rates, expression of ABCA1 and SR-BI in hepatocytes and peritoneal macrophages, and the level of ABCA1 and SR-BI in aortic lesions were remarkably improved in the probucol group, But the serum HDL cholesterol concentration, myeloperoxidase activity, the IMT and the percentage plaque area of aorta were significantly decreased. Conclusion Probucol alleviated atherosclerosis by improving HDL function. The mechanisms include accelerating the process of reverse cholesterol transport, improving the anti-inflammatory and anti-oxidant functions.
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Affiliation(s)
- Jian-Kai Zhong
- Division of Cardiology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, Guangdong, PR China
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Liu Y, Tang C. Regulation of ABCA1 functions by signaling pathways. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:522-9. [PMID: 21920460 DOI: 10.1016/j.bbalip.2011.08.015] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 08/02/2011] [Accepted: 08/20/2011] [Indexed: 10/17/2022]
Abstract
ATP-binding cassette transporter A1 (ABCA1) is an integral cell membrane protein that protects cardiovascular disease by at least two mechanisms: by export of excess cholesterol from cells and by suppression of inflammation. ABCA1 exports cholesterol and phospholipids from cells by multiple steps that involve forming cell surface lipid domains, binding of apolipoproteins to ABCA1, activating signaling pathways, and solubilizing these lipids by apolipoproteins. ABCA1 executes its anti-inflammatory effect by modifying cell membrane lipid rafts and directly activating signaling pathways. The interaction of apolipoproteins with ABCA1 activates multiple signaling pathways, including Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3), protein kinase A, Rho family G protein CDC42 and protein kinase C. Activating protein kinase A and Rho family G protein CDC42 regulates ABCA1-mediated lipid efflux, activating PKC stabilizes ABCA1 protein, and activating JAK2/STAT3 regulates both ABCA1-mediated lipid efflux and anti-inflammation. Thus, ABCA1 behaves both as a lipid exporter and a signaling receptor. Targeting ABCA1 receptor-like property using agonists for ABCA1 protein could become a promising new therapeutic target for increasing ABCA1 function and treating cardiovascular disease. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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Affiliation(s)
- Yuhua Liu
- Deparment of Medicine, Diabetes and Obesity Center of Excellence, University of Washington, Seattle, WA 98195-8055, USA
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Le Lay S, Rodriguez M, Jessup W, Rentero C, Li Q, Cartland S, Grewal T, Gaus K. Caveolin-1-mediated apolipoprotein A-I membrane binding sites are not required for cholesterol efflux. PLoS One 2011; 6:e23353. [PMID: 21858084 PMCID: PMC3155548 DOI: 10.1371/journal.pone.0023353] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 07/13/2011] [Indexed: 11/18/2022] Open
Abstract
Caveolin-1 (Cav1), a structural protein required for the formation of invaginated membrane domains known as caveolae, has been implicated in cholesterol trafficking and homeostasis. Here we investigated the contribution of Cav1 to apolipoprotein A-I (apoA-I) cell surface binding and intracellular processing using mouse embryonic fibroblasts (MEFs) derived from wild type (WT) or Cav1-deficient (Cav1(-/-)) animals. We found that cells expressing Cav1 have 2.6-fold more apoA-I binding sites than Cav1(-/-) cells although these additional binding sites are not associated with detergent-free lipid rafts. Further, Cav1-mediated binding targets apoA-I for internalization and degradation and these processes are not correlated to cholesterol efflux. Despite lower apoA-I binding, cholesterol efflux from Cav1(-/-) MEFs is 1.7-fold higher than from WT MEFs. Stimulation of ABCA1 expression with an LXR agonist enhances cholesterol efflux from both WT and Cav1(-/-) cells without increasing apoA-I surface binding or affecting apoA-I processing. Our results indicate that there are at least two independent lipid binding sites for apoA-I; Cav1-mediated apoA-I surface binding and uptake is not linked to cholesterol efflux, indicating that membrane domains other than caveolae regulate ABCA1-mediated cholesterol efflux.
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Affiliation(s)
- Soazig Le Lay
- Centre de Recherche des Cordeliers, INSERM, U872, Paris, France
| | - Macarena Rodriguez
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Wendy Jessup
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Carles Rentero
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Qiong Li
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Siân Cartland
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Thomas Grewal
- Faculty of Pharmacy, University of Sydney, Sydney, Australia
| | - Katharina Gaus
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
- * E-mail:
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Trypanosoma cruzi epimastigotes are able to store and mobilize high amounts of cholesterol in reservosome lipid inclusions. PLoS One 2011; 6:e22359. [PMID: 21818313 PMCID: PMC3144899 DOI: 10.1371/journal.pone.0022359] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Accepted: 06/26/2011] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Reservosomes are lysosome-related organelles found in Trypanosoma cruzi epimastigotes. They represent the last step in epimastigote endocytic route, accumulating a set of proteins and enzymes related to protein digestion and lipid metabolism. The reservosome matrix contains planar membranes, vesicles and lipid inclusions. Some of the latter may assume rectangular or sword-shaped crystalloid forms surrounded by a phospholipid monolayer, resembling the cholesterol crystals in foam cells. METHODOLOGY/PRINCIPAL FINDINGS Using Nile Red fluorimetry and fluorescence microscopy, as well as electron microscopy, we have established a direct correlation between serum concentration in culture medium and the presence of crystalloid lipid inclusions. Starting from a reservosome purified fraction, we have developed a fractionation protocol to isolate lipid inclusions. Gas-chromatography mass-spectrometry (GC-MS) analysis revealed that lipid inclusions are composed mainly by cholesterol and cholesterol esters. Moreover, when the parasites with crystalloid lipid-loaded reservosomes were maintained in serum free medium for 48 hours the inclusions disappeared almost completely, including the sword shaped ones. CONCLUSIONS/SIGNIFICANCE Taken together, our results suggest that epimastigote forms of T. cruzi store high amounts of neutral lipids from extracellular medium, mostly cholesterol or cholesterol esters inside reservosomes. Interestingly, the parasites are able to disassemble the reservosome cholesterol crystalloid inclusions when submitted to serum starvation.
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