1
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Nutter CA, Kidd BM, Carter HA, Hamel JI, Mackie PM, Kumbkarni N, Davenport ML, Tuyn DM, Gopinath A, Creigh PD, Sznajder ŁJ, Wang ET, Ranum LPW, Khoshbouei H, Day JW, Sampson JB, Prokop S, Swanson MS. Choroid plexus mis-splicing and altered cerebrospinal fluid composition in myotonic dystrophy type 1. Brain 2023; 146:4217-4232. [PMID: 37143315 PMCID: PMC10545633 DOI: 10.1093/brain/awad148] [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: 01/23/2023] [Revised: 04/08/2023] [Accepted: 04/18/2023] [Indexed: 05/06/2023] Open
Abstract
Myotonic dystrophy type 1 is a dominantly inherited multisystemic disease caused by CTG tandem repeat expansions in the DMPK 3' untranslated region. These expanded repeats are transcribed and produce toxic CUG RNAs that sequester and inhibit activities of the MBNL family of developmental RNA processing factors. Although myotonic dystrophy is classified as a muscular dystrophy, the brain is also severely affected by an unusual cohort of symptoms, including hypersomnia, executive dysfunction, as well as early onsets of tau/MAPT pathology and cerebral atrophy. To address the molecular and cellular events that lead to these pathological outcomes, we recently generated a mouse Dmpk CTG expansion knock-in model and identified choroid plexus epithelial cells as particularly affected by the expression of toxic CUG expansion RNAs. To determine if toxic CUG RNAs perturb choroid plexus functions, alternative splicing analysis was performed on lateral and hindbrain choroid plexi from Dmpk CTG knock-in mice. Choroid plexus transcriptome-wide changes were evaluated in Mbnl2 knockout mice, a developmental-onset model of myotonic dystrophy brain dysfunction. To determine if transcriptome changes also occurred in the human disease, we obtained post-mortem choroid plexus for RNA-seq from neurologically unaffected (two females, three males; ages 50-70 years) and myotonic dystrophy type 1 (one female, three males; ages 50-70 years) donors. To test that choroid plexus transcriptome alterations resulted in altered CSF composition, we obtained CSF via lumbar puncture from patients with myotonic dystrophy type 1 (five females, five males; ages 35-55 years) and non-myotonic dystrophy patients (three females, four males; ages 26-51 years), and western blot and osmolarity analyses were used to test CSF alterations predicted by choroid plexus transcriptome analysis. We determined that CUG RNA induced toxicity was more robust in the lateral choroid plexus of Dmpk CTG knock-in mice due to comparatively higher Dmpk and lower Mbnl RNA levels. Impaired transitions to adult splicing patterns during choroid plexus development were identified in Mbnl2 knockout mice, including mis-splicing previously found in Dmpk CTG knock-in mice. Whole transcriptome analysis of myotonic dystrophy type 1 choroid plexus revealed disease-associated RNA expression and mis-splicing events. Based on these RNA changes, predicted alterations in ion homeostasis, secretory output and CSF composition were confirmed by analysis of myotonic dystrophy type 1 CSF. Our results implicate choroid plexus spliceopathy and concomitant alterations in CSF homeostasis as an unappreciated contributor to myotonic dystrophy type 1 CNS pathogenesis.
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Affiliation(s)
- Curtis A Nutter
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Benjamin M Kidd
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Helmut A Carter
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Johanna I Hamel
- Department of Neurology, University of Rochester, Rochester, NY 14642, USA
| | - Philip M Mackie
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Nayha Kumbkarni
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Mackenzie L Davenport
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Dana M Tuyn
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Adithya Gopinath
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Peter D Creigh
- Department of Neurology, University of Rochester, Rochester, NY 14642, USA
| | - Łukasz J Sznajder
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Eric T Wang
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Laura P W Ranum
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, McKnight Brain Institute and the Fixel Institute for Neurological Diseases, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Habibeh Khoshbouei
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - John W Day
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Jacinda B Sampson
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94304, USA
| | - Stefan Prokop
- Department of Pathology, Immunology, and Laboratory Medicine, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute and the Fixel Institute for Neurological Diseases, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
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2
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Paterson HAB, Yu S, Artigas N, Prado MA, Haberman N, Wang YF, Jobbins AM, Pahita E, Mokochinski J, Hall Z, Guerin M, Paulo JA, Ng SS, Villarroya F, Rashid ST, Le Goff W, Lenhard B, Cebola I, Finley D, Gygi SP, Sibley CR, Vernia S. Liver RBFOX2 regulates cholesterol homeostasis via Scarb1 alternative splicing in mice. Nat Metab 2022; 4:1812-1829. [PMID: 36536133 PMCID: PMC9771820 DOI: 10.1038/s42255-022-00681-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 10/10/2022] [Indexed: 12/24/2022]
Abstract
RNA alternative splicing (AS) expands the regulatory potential of eukaryotic genomes. The mechanisms regulating liver-specific AS profiles and their contribution to liver function are poorly understood. Here, we identify a key role for the splicing factor RNA-binding Fox protein 2 (RBFOX2) in maintaining cholesterol homeostasis in a lipogenic environment in the liver. Using enhanced individual-nucleotide-resolution ultra-violet cross-linking and immunoprecipitation, we identify physiologically relevant targets of RBFOX2 in mouse liver, including the scavenger receptor class B type I (Scarb1). RBFOX2 function is decreased in the liver in diet-induced obesity, causing a Scarb1 isoform switch and alteration of hepatocyte lipid homeostasis. Our findings demonstrate that specific AS programmes actively maintain liver physiology, and underlie the lipotoxic effects of obesogenic diets when dysregulated. Splice-switching oligonucleotides targeting this network alleviate obesity-induced inflammation in the liver and promote an anti-atherogenic lipoprotein profile in the blood, underscoring the potential of isoform-specific RNA therapeutics for treating metabolism-associated diseases.
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Affiliation(s)
- Helen A B Paterson
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Sijia Yu
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Natalia Artigas
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Miguel A Prado
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Instituto de Investigación Sanitaria del Principado de Asturias, Avenida Hospital Universitario, Oviedo, Spain
| | - Nejc Haberman
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Yi-Fang Wang
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Andrew M Jobbins
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Elena Pahita
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Joao Mokochinski
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Zoe Hall
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Maryse Guerin
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Paris, France
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Soon Seng Ng
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Francesc Villarroya
- Biochemistry and Molecular Biomedicine Department, Institute of Biomedicine, University of Barcelona & Research Institute Sant Joan de Déu, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y Nutrición (CIBEROBN), ISCIII, Madrid, Spain
| | - Sheikh Tamir Rashid
- Division of Systems Medicine, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Wilfried Le Goff
- Sorbonne Université, Inserm, Institute of Cardiometabolism and Nutrition (ICAN), UMR_S1166, Paris, France
| | - Boris Lenhard
- MRC London Institute of Medical Sciences, London, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Inês Cebola
- Section of Genetics and Genomics, Department of Metabolism, Digestion and Reproduction, Imperial College London, Hammersmith Hospital Campus, London, UK
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Christopher R Sibley
- Institute of Quantitative Biology, Biochemistry and Biotechnology. School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Santiago Vernia
- MRC London Institute of Medical Sciences, London, UK.
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, London, UK.
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3
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Griffiths G, Gruenberg J, Marsh M, Wohlmann J, Jones AT, Parton RG. Nanoparticle entry into cells; the cell biology weak link. Adv Drug Deliv Rev 2022; 188:114403. [PMID: 35777667 DOI: 10.1016/j.addr.2022.114403] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 06/22/2022] [Accepted: 06/23/2022] [Indexed: 12/22/2022]
Abstract
Nanoparticles (NP) are attractive options for the therapeutic delivery of active pharmaceutical drugs, proteins and nucleic acids into cells, tissues and organs. Research into the development and application of NP most often starts with a diverse group of scientists, including chemists, bioengineers and material and pharmaceutical scientists, who design, fabricate and characterize NP in vitro (Stage 1). The next step (Stage 2) generally investigates cell toxicity as well as the processes by which NP bind, are internalized and deliver their cargo to appropriate model tissue culture cells. Subsequently, in Stage 3, selected NP are tested in animal systems, mostly mouse. Whereas the chemistry-based development and analysis in Stage 1 is increasingly sophisticated, the investigations in Stage 2 are not what could be regarded as 'state-of-the-art' for the cell biology field and the quality of research into NP interactions with cells is often sub-standard. In this review we describe our current understanding of the mechanisms by which particles gain entry into mammalian cells via endocytosis. We summarize the most important areas for concern, highlight some of the most common mis-conceptions, and identify areas where NP scientists could engage with trained cell biologists. Our survey of the different mechanisms of uptake into cells makes us suspect that claims for roles for caveolae, as well as macropinocytosis, in NP uptake into cells have been exaggerated, whereas phagocytosis has been under-appreciated.
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Affiliation(s)
- Gareth Griffiths
- Department Biosciences, University of Oslo, Blindernveien 31, PO Box 1041, 0316 Oslo, Norway.
| | - Jean Gruenberg
- Department of Biochemistry, University of Geneva, 30 quai E. Ansermet, 1211-Geneva-4, Switzerland
| | - Mark Marsh
- Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Jens Wohlmann
- Department Biosciences, University of Oslo, Blindernveien 31, PO Box 1041, 0316 Oslo, Norway
| | - Arwyn T Jones
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Redwood Building, Cardiff, Wales CF103NB, UK
| | - Robert G Parton
- Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, The University of Queensland, Qld 4072, Australia
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4
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Casado ME, Huerta L, Marcos-Díaz A, Ortiz AI, Kraemer FB, Lasunción MA, Busto R, Martín-Hidalgo A. Hormone-sensitive lipase deficiency affects the expression of SR-BI, LDLr, and ABCA1 receptors/transporters involved in cellular cholesterol uptake and efflux and disturbs fertility in mouse testis. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:159043. [PMID: 34461308 DOI: 10.1016/j.bbalip.2021.159043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/18/2021] [Accepted: 08/19/2021] [Indexed: 12/14/2022]
Abstract
Hormone-sensitive lipase (HSL) hydrolyse acylglycerols, cholesteryl and retinyl esters. HSL is a key lipase in mice testis, as HSL deficiency results in male sterility. The present work study the effects of the deficiency and lack of HSL on the localization and expression of SR-BI, LDLr, and ABCA1 receptors/transporters involved in uptake and efflux of cholesterol in mice testis, to determine the impact of HSL gene dosage on testis morphology, lipid homeostasis and fertility. The results of this work show that the lack of HSL in mice alters testis morphology and spermatogenesis, decreasing sperm counts, sperm motility and increasing the amount of Leydig cells and lipid droplets. They also show that there are differences in the localization of HSL, SR-BI, LDLr and ABCA1 in HSL+/+, HSL+/- and HSL-/- mice. The deficiency or lack of HSL has effects on protein and mRNA expression of genes involved in lipid metabolisms in mouse testis. HSL-/- testis have augmented expression of SR-BI, LDLr, ABCA1 and LXRβ, a critical sterol sensor that regulate multiple genes involved in lipid metabolism; whereas LDLr expression decreased in HSL+/- mice. Plin2, Abca1 and Ldlr mRNA levels increased; and LXRα (Nr1h3) and LXRβ (Nr1h2) decreased in testis from HSL-/- compared with HSL+/+; with no differences in Scarb1. Together these data suggest that HSL deficiency or lack in mice testis induces lipid homeostasis alterations that affect the cellular localization and expression of key receptors/transporter involved in cellular cholesterol uptake and efflux (SR-BI, LDRr, ABCA1); alters normal cellular function and impact fertility.
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Affiliation(s)
- María Emilia Casado
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain
| | - Lydia Huerta
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain
| | - Ana Marcos-Díaz
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain
| | - Ana Isabel Ortiz
- Unidad de Cirugía Experimental y Animalario, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain
| | - Fredric B Kraemer
- Division of Endocrinology, Stanford University, United States of America; VA Palo Alto Health Care System, Palo Alto, CA, United States of America
| | - Miguel Angel Lasunción
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain
| | - Rebeca Busto
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain
| | - Antonia Martín-Hidalgo
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRyCIS), E-28034 Madrid, Spain; CIBER de Fisiopatología de la Obesidad y Nutrición (CIBERobn), ISCIII, Spain.
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5
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Hydrophobicity drives receptor-mediated uptake of heat-processed proteins by THP-1 macrophages and dendritic cells, but not cytokine responses. PLoS One 2020; 15:e0236212. [PMID: 32797100 PMCID: PMC7428126 DOI: 10.1371/journal.pone.0236212] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/02/2020] [Indexed: 11/24/2022] Open
Abstract
Although an impact of processing on immunogenicity of food proteins has clearly been demonstrated, the underlying mechanisms are still unclear. We applied 3 different processing methods: wet heating (60 °C) and low- or high-temperature (50 °C or 130 °C, respectively) dry-heating in absence or presence of reducing sugars, to β-lactoglobulin (BLG), lysozyme and thyroglobulin, which represent dietary proteins with different pI or molecular weight. Uptake of the soluble fraction of the samples was tested in two types of, genetically homogeneous, antigen-presenting cells (macrophages and dendritic cells derived from THP-1 monocytes). This revealed a strong correlation between the uptake of the different protein samples by macrophages and dendritic cells, and confirmed the key role of hydrophobicity, over aggregation, in determining the uptake. Several uptake routes were shown to contribute to the uptake of BLG by macrophages. However, cytokine responses following exposure of macrophages to BLG samples were not related to the levels of uptake. Together, our results demonstrate that heat-treatment-induced increased hydrophobicity is the prime driving factor in uptake, but not in cytokine production, by THP-1 macrophages.
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Marques PE, Nyegaard S, Collins RF, Troise F, Freeman SA, Trimble WS, Grinstein S. Multimerization and Retention of the Scavenger Receptor SR-B1 in the Plasma Membrane. Dev Cell 2019; 50:283-295.e5. [DOI: 10.1016/j.devcel.2019.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 04/05/2019] [Accepted: 05/10/2019] [Indexed: 10/26/2022]
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Velagapudi S, Schraml P, Yalcinkaya M, Bolck HA, Rohrer L, Moch H, von Eckardstein A. Scavenger receptor BI promotes cytoplasmic accumulation of lipoproteins in clear-cell renal cell carcinoma. J Lipid Res 2018; 59:2188-2201. [PMID: 30173145 PMCID: PMC6210910 DOI: 10.1194/jlr.m083311] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 06/21/2018] [Indexed: 01/01/2023] Open
Abstract
Clear-cell renal cell carcinomas (ccRCCs) are characterized by inactivation of the von Hippel-Lindau (VHL) gene and intracellular lipid accumulation by unknown pathomechanisms. The immunochemical analysis of 356 RCCs revealed high abundance of apoA-I and apoB, as well as scavenger receptor BI (SR-BI) in the ccRCC subtype. Given the characteristic loss of VHL function in ccRCC, we used VHL-defective and VHL-proficient cells to study the potential influence of VHL on lipoprotein uptake. VHL-defective patient-derived ccRCC cells and cell lines (786O and RCC4) showed enhanced uptake as well as less resecretion and degradation of radio-iodinated HDL and LDL (125I-HDL and 125I-LDL, respectively) compared with the VHL-proficient cells. The ccRCC cells showed enhanced vascular endothelial growth factor (VEGF) and SR-BI expression compared with normal kidney epithelial cells. Uptake of 125I-HDL and 125I-LDL by patient-derived normal kidney epithelial cells as well as the VHL-reexpressing ccRCC cell lines, 786-O-VHL and RCC4-O-VHL cells, was strongly enhanced by VEGF treatment. The knockdown of the VEGF coreceptor, neuropilin-1 (NRP1), as well as blocking of SR-BI significantly reduced the uptake of lipoproteins into ccRCC cells in vitro. LDL stimulated proliferation of 786-O cells more potently than 786-O-VHL cells in a NRP1- and SR-BI-dependent manner. In conclusion, enhanced lipoprotein uptake due to increased activities of VEGF/NRP1 and SR-BI promotes lipid accumulation and proliferation of VHL-defective ccRCC cells.
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Affiliation(s)
- Srividya Velagapudi
- Institute of Clinical Chemistry University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Peter Schraml
- Department of Pathology and Molecular Pathology, University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Mustafa Yalcinkaya
- Institute of Clinical Chemistry University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Hella A Bolck
- Department of Pathology and Molecular Pathology, University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Lucia Rohrer
- Institute of Clinical Chemistry University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Holger Moch
- Department of Pathology and Molecular Pathology, University of Zurich and University Hospital of Zurich, Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute of Clinical Chemistry University of Zurich and University Hospital of Zurich, Zurich, Switzerland
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Zucca FA, Vanna R, Cupaioli FA, Bellei C, De Palma A, Di Silvestre D, Mauri P, Grassi S, Prinetti A, Casella L, Sulzer D, Zecca L. Neuromelanin organelles are specialized autolysosomes that accumulate undegraded proteins and lipids in aging human brain and are likely involved in Parkinson's disease. NPJ Parkinsons Dis 2018; 4:17. [PMID: 29900402 PMCID: PMC5988730 DOI: 10.1038/s41531-018-0050-8] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 04/10/2018] [Accepted: 04/17/2018] [Indexed: 01/08/2023] Open
Abstract
During aging, neuronal organelles filled with neuromelanin (a dark-brown pigment) and lipid bodies accumulate in the brain, particularly in the substantia nigra, a region targeted in Parkinson's disease. We have investigated protein and lipid systems involved in the formation of these organelles and in the synthesis of the neuromelanin of human substantia nigra. Membrane and matrix proteins characteristic of lysosomes were found in neuromelanin-containing organelles at a lower number than in typical lysosomes, indicating a reduced enzymatic activity and likely impaired capacity for lysosomal and autophagosomal fusion. The presence of proteins involved in lipid transport may explain the accumulation of lipid bodies in the organelle and the lipid component in neuromelanin structure. The major lipids observed in lipid bodies of the organelle are dolichols with lower amounts of other lipids. Proteins of aggregation and degradation pathways were present, suggesting a role for accumulation by this organelle when the ubiquitin-proteasome system is inadequate. The presence of proteins associated with aging and storage diseases may reflect impaired autophagic degradation or impaired function of lysosomal enzymes. The identification of typical autophagy proteins and double membranes demonstrates the organelle's autophagic nature and indicates that it has engulfed neuromelanin precursors from the cytosol. Based on these data, it appears that the neuromelanin-containing organelle has a very slow turnover during the life of a neuron and represents an intracellular compartment of final destination for numerous molecules not degraded by other systems.
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Affiliation(s)
- Fabio A. Zucca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Renzo Vanna
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
- IRCCS Don Carlo Gnocchi ONLUS Foundation, Milan, Italy
| | - Francesca A. Cupaioli
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Chiara Bellei
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Antonella De Palma
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Dario Di Silvestre
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Pierluigi Mauri
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Sara Grassi
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate, Milan, Italy
| | - Alessandro Prinetti
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Segrate, Milan, Italy
| | - Luigi Casella
- Department of Chemistry, University of Pavia, Pavia, Italy
| | - David Sulzer
- Department of Psychiatry, Columbia University Medical Center, New York State Psychiatric Institute, New York, NY USA
- Department of Neurology, Columbia University Medical Center, New York, NY USA
- Department of Pharmacology, Columbia University Medical Center, New York, NY USA
| | - Luigi Zecca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
- Department of Psychiatry, Columbia University Medical Center, New York State Psychiatric Institute, New York, NY USA
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Novel mechanism of regulation of the 5-lipoxygenase/leukotriene B 4 pathway by high-density lipoprotein in macrophages. Sci Rep 2017; 7:12989. [PMID: 29021582 PMCID: PMC5636875 DOI: 10.1038/s41598-017-13154-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 09/19/2017] [Indexed: 02/06/2023] Open
Abstract
High-density lipoprotein (HDL) interacts with various cells, particularly macrophages, in functional cell-HDL interactions. Here, we found that HDL protein quality and lipid quality play critical roles in HDL functions. HDL fractions from healthy volunteers (HDLHealthy) and patients with recurrent coronary atherosclerotic disease (HDLCAD) were prepared. To analyse functional HDL-macrophage interactions, macrophages were co-incubated with each HDL, and lipid mediator production was assessed by liquid chromatography/mass spectrometry-based metabololipidomics. HDLHealthy treatment attenuated the pro-inflammatory lipid mediator production, particularly that of leukotriene (LT) B4, and this treatment enhanced lipoxin (LX) B4 and resolvin (Rv) E2 production. HDLHealthy treatment enhanced the proteasome-mediated degradation of the LTB4-producing enzyme 5-lipoxygenase (LO) in activated macrophages; however, HDLCAD did not show these anti-inflammatory effects. HDLHealthy was engulfed by macrophages via clathrin-mediated endocytosis, which was a critical step in 5-LO/LTB4 regulation. We also found that HDLCAD showed higher levels of the LTB4-producing enzymes and thus promoted LTB4 production from HDLCAD. In addition, LTB4 attenuated HDL endocytosis, HDL-mediated 5-LO degradation in macrophages, and HDL-derived augmentation of macrophage phagocytosis. These results indicated that local LTB4 produced de novo from HDLCAD regulates HDL-macrophage functional interactions and plays critical roles in dysfunctional, inflammatory HDL characteristics.
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10
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Vasquez M, Fioravanti J, Aranda F, Paredes V, Gomar C, Ardaiz N, Fernandez-Ruiz V, Méndez M, Nistal-Villan E, Larrea E, Gao Q, Gonzalez-Aseguinolaza G, Prieto J, Berraondo P. Interferon alpha bioactivity critically depends on Scavenger receptor class B type I function. Oncoimmunology 2016; 5:e1196309. [PMID: 27622065 PMCID: PMC5007953 DOI: 10.1080/2162402x.2016.1196309] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 05/10/2016] [Accepted: 05/27/2016] [Indexed: 12/11/2022] Open
Abstract
Scavenger receptor class B type I (SR-B1) binds pathogen-associated molecular patterns participating in the regulation of the inflammatory reaction but there is no information regarding potential interactions between SR-B1 and the interferon system. Herein, we report that SR-B1 ligands strongly regulate the transcriptional response to interferon α (IFNα) and enhance its antiviral and antitumor activity. This effect was mediated by the activation of TLR2 and TLR4 as it was annulled by the addition of anti-TLR2 or anti-TLR4 blocking antibodies. In vivo, we maximized the antitumor activity of IFNα co-expressing in the liver a SR-B1 ligand and IFNα by adeno-associated viruses. This gene therapy strategy eradicated liver metastases from colon cancer with reduced toxicity. On the other hand, genetic and pharmacological inhibition of SR-B1 blocks the clathrin-dependent interferon receptor recycling pathway with a concomitant reduction in IFNα signaling and bioactivity. This effect can be applied to enhance cancer immunotherapy with oncolytic viruses. Indeed, SR-B1 antagonists facilitate replication of oncolytic viruses amplifying their tumoricidal potential. In conclusion, SR-B1 agonists behave as IFNα enhancers while SR-B1 inhibitors dampen IFNα activity. These results demonstrate that SR-B1 is a suitable pharmacology target to enhance cancer immunotherapy based on IFNα and oncolytic viruses.
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Affiliation(s)
- Marcos Vasquez
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Jessica Fioravanti
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Fernando Aranda
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Vladimir Paredes
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA), Pamplona, Navarra, Spain; Centro Médico Nacional La Raza, IMSS, México DF, Mexico
| | - Celia Gomar
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Nuria Ardaiz
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Veronica Fernandez-Ruiz
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Miriam Méndez
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Estanislao Nistal-Villan
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Esther Larrea
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA), Pamplona, Navarra, Spain; Instituto de Salud Tropical, University of Navarra, Pamplona, Navarra, Spain
| | - Qinshan Gao
- Department of Microbiology, Icahn School of Medicine at Mount Sinai , New York, NY, USA
| | - Gloria Gonzalez-Aseguinolaza
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Jesus Prieto
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
| | - Pedro Berraondo
- Program of Immunology and Immunotherapy, Center for Applied Medical Research (CIMA), Navarra Institute for Health Research (IdiSNA) , Pamplona, Navarra, Spain
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11
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Lockett AD, Petrusca DN, Justice MJ, Poirier C, Serban KA, Rush NI, Kamocka M, Predescu D, Predescu S, Petrache I. Scavenger receptor class B, type I-mediated uptake of A1AT by pulmonary endothelial cells. Am J Physiol Lung Cell Mol Physiol 2015; 309:L425-34. [PMID: 26092999 DOI: 10.1152/ajplung.00376.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 06/09/2015] [Indexed: 12/13/2022] Open
Abstract
In addition to exerting a potent anti-elastase function, α-1 antitrypsin (A1AT) maintains the structural integrity of the lung by inhibiting endothelial inflammation and apoptosis. A main serpin secreted in circulation by hepatocytes, A1AT requires uptake by the endothelium to achieve vasculoprotective effects. This active uptake mechanism, which is inhibited by cigarette smoking (CS), involves primarily clathrin- but also caveola-mediated endocytosis and may require active binding to a receptor. Because circulating A1AT binds to high-density lipoprotein (HDL), we hypothesized that scavenging receptors are candidates for endothelial uptake of the serpin. Although the low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) internalizes only elastase-bound A1AT, the scavenger receptor B type I (SR-BI), which binds and internalizes HDL and is modulated by CS, may be involved in A1AT uptake. Transmission electron microscopy imaging of colloidal gold-labeled A1AT confirmed A1AT endocytosis in both clathrin-coated vesicles and caveolae in endothelial cells. SR-BI immunoprecipitation identified binding to A1AT at the plasma membrane. Pretreatment of human lung microvascular endothelial cells with SR-B ligands (HDL or LDL), knockdown of SCARB1 expression, or neutralizing SR-BI antibodies significantly reduced A1AT uptake by 30-50%. Scarb1 null mice exhibited decreased A1AT lung content following systemic A1AT administration and reduced lung anti-inflammatory effects of A1AT supplementation during short-term CS exposure. In turn, A1AT supplementation increased lung SR-BI expression and modulated circulating lipoprotein levels in wild-type animals. These studies indicate that SR-BI is an important mediator of A1AT endocytosis in pulmonary endothelium and suggest a cross talk between A1AT and lipoprotein regulation of vascular functions.
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Affiliation(s)
- Angelia D Lockett
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana;
| | - Daniela N Petrusca
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Matthew J Justice
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Christophe Poirier
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Karina A Serban
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Natalia I Rush
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Malgorzata Kamocka
- Division of Nephrology, Department of Medicine, Indiana University, Indianapolis, Indiana
| | - Dan Predescu
- Department of Pharmacology, Rush University, Chicago, Illinois; and
| | - Sanda Predescu
- Department of Pharmacology, Rush University, Chicago, Illinois; and
| | - Irina Petrache
- Division of Pulmonary, Allergy, Critical Care and Occupational Medicine, Department of Medicine, Indiana University, Indianapolis, Indiana; The Richard L. Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana
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12
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Zani IA, Stephen SL, Mughal NA, Russell D, Homer-Vanniasinkam S, Wheatcroft SB, Ponnambalam S. Scavenger receptor structure and function in health and disease. Cells 2015; 4:178-201. [PMID: 26010753 PMCID: PMC4493455 DOI: 10.3390/cells4020178] [Citation(s) in RCA: 217] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 12/23/2022] Open
Abstract
Scavenger receptors (SRs) are a ‘superfamily’ of membrane-bound receptors that were initially thought to bind and internalize modified low-density lipoprotein (LDL), though it is currently known to bind to a variety of ligands including endogenous proteins and pathogens. New family of SRs and their properties have been identified in recent years, and have now been classified into 10 eukaryote families, defined as Classes A-J. These receptors are classified according to their sequences, although in each class they are further classified based in the variations of the sequence. Their ability to bind a range of ligands is reflected on the biological functions such as clearance of modified lipoproteins and pathogens. SR members regulate pathophysiological states including atherosclerosis, pathogen infections, immune surveillance, and cancer. Here, we review our current understanding of SR structure and function implicated in health and disease.
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Affiliation(s)
- Izma Abdul Zani
- Endothelial Cell Biology Unit, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Sam L Stephen
- Endothelial Cell Biology Unit, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Nadeem A Mughal
- Endothelial Cell Biology Unit, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
- Leeds Vascular Institute, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK
| | - David Russell
- Leeds Vascular Institute, Leeds General Infirmary, Great George Street, Leeds LS1 3EX, UK
| | | | - Stephen B Wheatcroft
- Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Sreenivasan Ponnambalam
- Endothelial Cell Biology Unit, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
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13
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Jang S, Ohtani K, Fukuoh A, Mori K, Yoshizaki T, Kitamoto N, Kim Y, Suzuki Y, Wakamiya N. Scavenger receptor CL-P1 mediates endocytosis by associating with AP-2μ2. Biochim Biophys Acta Gen Subj 2014; 1840:3226-37. [DOI: 10.1016/j.bbagen.2014.07.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 07/27/2014] [Accepted: 07/28/2014] [Indexed: 10/24/2022]
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14
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Yu P, Gao Z, Zong Y, Bao L, Xu L, Deng W, Li F, Lv Q, Gao Z, Xu Y, Yao Y, Qin C. Histopathological features and distribution of EV71 antigens and SCARB2 in human fatal cases and a mouse model of enterovirus 71 infection. Virus Res 2014; 189:121-32. [PMID: 24842162 DOI: 10.1016/j.virusres.2014.05.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Revised: 05/08/2014] [Accepted: 05/08/2014] [Indexed: 10/25/2022]
Abstract
Enterovirus 71 (EV71) is a neurotropic pathogen that causes hand, foot, and mouth disease. While infection is usually self-limiting, a minority of patients infected with EV71 develop severe neurological complications. In humans, EV71 has been reported to utilize the scavenger receptor class B, member 2 (SCARB2) as a receptor for infectious cellular entry. In this study, we define the pathological features of EV71-associated disease as well as the distribution of EV71 antigen and SCARB2 in human fatal cases and a mouse model. Histopathologically, human fatal cases showed severe central nervous system (CNS) changes, mainly in the brainstems, spinal cords, and thalamus. These patient further exhibited pulmonary edema and necrotic enteritis. Immunohistochemical analysis of human fatal cases demonstrated that EV71 antigen and SCARB2 were observed mainly in neurons, microglia cells and inflammatory cells in the CNS, and epithelial cells in the intestines. However, skeletal muscle tissue was negative for EV71 antigen. In a mouse model of EV71 infection, we observed massive necrotic myositis, different degrees of viral diseases in CNS, and extensive interstitial pneumonia. In mice, EV71 exhibits strong myotropism compared to the neurotropism seen in humans. EV71 antigen was detected in the spinal cord and brainstem of mice. However, there was no clear correlation between mouse SCARB2 and EV71 antigen distribution in the mouse model, consistent with previous results that SCARB2 functions as a receptor for EV71 in humans but not mice. The EV71-induced lesions seen in the mouse model resembled the pathological changes seen in human samples. These results increase our understanding of EV71 pathogenesis and will inform further work developing a mouse model for EV71 infection.
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MESH Headings
- Animals
- Antigens, Viral/analysis
- CD36 Antigens/analysis
- Child, Preschool
- Disease Models, Animal
- Enterovirus A, Human/physiology
- Female
- Genome, Viral
- Hand, Foot and Mouth Disease/pathology
- Hand, Foot and Mouth Disease/virology
- Humans
- Infant
- Lysosomal Membrane Proteins/analysis
- Male
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- RNA, Viral/genetics
- Receptors, Scavenger/analysis
- Receptors, Virus/analysis
- Sequence Analysis, DNA
- Viral Tropism
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Affiliation(s)
- Pin Yu
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Zifen Gao
- Department of Pathology, Peking University Health Science Center, Beijing 100191, China.
| | - Yuanyuan Zong
- Department of Pathology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan 250021, China.
| | - Linlin Bao
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Lili Xu
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Wei Deng
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Fengdi Li
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Qi Lv
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Zhancheng Gao
- Department of Respiratory & Critical Care Medicine, Peking University People's Hospital, Beijing 100044, China.
| | - Yanfeng Xu
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Yanfeng Yao
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
| | - Chuan Qin
- Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences (CAMS) & Comparative Medicine Center, Peking Union Medical College (PUMC), Key Laboratory of Human Disease Comparative Medicine, Ministry of Health, Beijing 100021, China.
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15
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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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16
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Roet KCD, Franssen EHP, de Bree FM, Essing AHW, Zijlstra SJJ, Fagoe ND, Eggink HM, Eggers R, Smit AB, van Kesteren RE, Verhaagen J. A multilevel screening strategy defines a molecular fingerprint of proregenerative olfactory ensheathing cells and identifies SCARB2, a protein that improves regenerative sprouting of injured sensory spinal axons. J Neurosci 2013; 33:11116-35. [PMID: 23825416 PMCID: PMC6618611 DOI: 10.1523/jneurosci.1002-13.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 05/14/2013] [Accepted: 05/15/2013] [Indexed: 11/21/2022] Open
Abstract
Olfactory ensheathing cells (OECs) have neuro-restorative properties in animal models for spinal cord injury, stroke, and amyotrophic lateral sclerosis. Here we used a multistep screening approach to discover genes specifically contributing to the regeneration-promoting properties of OECs. Microarray screening of the injured olfactory pathway and of cultured OECs identified 102 genes that were subsequently functionally characterized in cocultures of OECs and primary dorsal root ganglion (DRG) neurons. Selective siRNA-mediated knockdown of 16 genes in OECs (ADAMTS1, BM385941, FZD1, GFRA1, LEPRE1, NCAM1, NID2, NRP1, MSLN, RND1, S100A9, SCARB2, SERPINI1, SERPINF1, TGFB2, and VAV1) significantly reduced outgrowth of cocultured DRG neurons, indicating that endogenous expression of these genes in OECs supports neurite extension of DRG neurons. In a gain-of-function screen for 18 genes, six (CX3CL1, FZD1, LEPRE1, S100A9, SCARB2, and SERPINI1) enhanced and one (TIMP2) inhibited neurite growth. The most potent hit in both the loss- and gain-of-function screens was SCARB2, a protein that promotes cholesterol secretion. Transplants of fibroblasts that were genetically modified to overexpress SCARB2 significantly increased the number of regenerating DRG axons that grew toward the center of a spinal cord lesion in rats. We conclude that expression of SCARB2 enhances regenerative sprouting and that SCARB2 contributes to OEC-mediated neuronal repair.
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Affiliation(s)
- Kasper C D Roet
- Department of Neuroregeneration, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, 1105 BA Amsterdam, The Netherlands.
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17
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Casado ME, Huerta L, Ortiz AI, Pérez-Crespo M, Gutiérrez-Adán A, Kraemer FB, Lasunción MÁ, Busto R, Martín-Hidalgo A. HSL-knockout mouse testis exhibits class B scavenger receptor upregulation and disrupted lipid raft microdomains. J Lipid Res 2012; 53:2586-97. [PMID: 22988039 DOI: 10.1194/jlr.m028076] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
There is a tight relationship between fertility and changes in cholesterol metabolism during spermatogenesis. In the testis, class B scavenger receptors (SR-B) SR-BI, SR-BII, and LIMP II mediate the selective uptake of cholesterol esters from HDL, which are hydrolyzed to unesterified cholesterol by hormone-sensitive lipase (HSL). HSL is critical because HSL knockout (KO) male mice are sterile. The aim of the present work was to determine the effects of the lack of HSL in testis on the expression of SR-B, lipid raft composition, and related cell signaling pathways. HSL-KO mouse testis presented altered spermatogenesis associated with decreased sperm counts, sperm motility, and infertility. In wild-type (WT) testis, HSL is expressed in elongated spermatids; SR-BI, in Leydig cells and spermatids; SR-BII, in spermatocytes and spermatids but not in Leydig cells; and LIMP II, in Sertoli and Leydig cells. HSL knockout male mice have increased expression of class B scavenger receptors, disrupted caveolin-1 localization in lipid raft plasma membrane microdomains, and activated phospho-ERK, phospho-AKT, and phospho-SRC in the testis, suggesting that class B scavenger receptors are involved in cholesterol ester uptake for steroidogenesis and spermatogenesis in the testis.
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Affiliation(s)
- María Emilia Casado
- Servicio de Bioquímica-Investigación, Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria, Madrid, Spain
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18
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Lin YW, Lin HY, Tsou YL, Chitra E, Hsiao KN, Shao HY, Liu CC, Sia C, Chong P, Chow YH. Human SCARB2-mediated entry and endocytosis of EV71. PLoS One 2012; 7:e30507. [PMID: 22272359 PMCID: PMC3260287 DOI: 10.1371/journal.pone.0030507] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 12/18/2011] [Indexed: 01/16/2023] Open
Abstract
Enterovirus (EV) 71 infection is known to cause hand-foot-and-mouth disease (HFMD) and in severe cases, induces neurological disorders culminating in fatality. An outbreak of EV71 in South East Asia in 1997 affected over 120,000 people and caused neurological disorders in a few individuals. The control of EV71 infection through public health interventions remains minimal and treatments are only symptomatic. Recently, human scavenger receptor class B, member 2 (SCARB2) has been reported to be a cellular receptor of EV71. We expressed human SCARB2 gene in NIH3T3 cells (3T3-SCARB2) to study the mechanisms of EV71 entry and infection. We demonstrated that human SCARB2 serves as a cellular receptor for EV71 entry. Disruption of expression of SCARB2 using siRNAs can interfere EV71 infection and subsequent inhibit the expression of viral capsid proteins in RD and 3T3-SCARB2 but not Vero cells. SiRNAs specific to clathrin or dynamin or chemical inhibitor of clathrin-mediated endocytosis were all capable of interfering with the entry of EV71 into 3T3-SCARB2 cells. On the other hand, caveolin specific siRNA or inhibitors of caveolae-mediated endocytosis had no effect, confirming that only clathrin-mediated pathway was involved in EV71 infection. Endocytosis of EV71 was also found to be pH-dependent requiring endosomal acidification and also required intact membrane cholesterol. In summary, the mechanism of EV71 entry through SCARB2 as the receptor for attachment, and its cellular entry is through a clathrin-mediated and pH-dependent endocytic pathway. This study on the receptor and endocytic mechanisms of EV71 infection is useful for the development of effective medications and prophylactic treatment against the enterovirus.
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Affiliation(s)
- Yi-Wen Lin
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
- Graduate Program of Biotechnology in Medicine, Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan
| | - Hsiang-Yin Lin
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
| | - Yueh-Liang Tsou
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
- Graduate School of Life Science, National Defense Medical Center, Taipei, Taiwan
| | - Ebenezer Chitra
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
| | - Kuang-Nan Hsiao
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
| | - Hsiao-Yun Shao
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
| | - Chia-Chyi Liu
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
| | - Charles Sia
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
- Graduate Institute of Immunology, China Medical University, Taichung, Taiwan
| | - Pele Chong
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
- Graduate Institute of Immunology, China Medical University, Taichung, Taiwan
| | - Yen-Hung Chow
- National Institutes of Infectious Disease and Vaccinology, National Health Research Institutes, Taiwan, Republic of China
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19
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Coxsackievirus A24 variant uses sialic acid-containing O-linked glycoconjugates as cellular receptors on human ocular cells. J Virol 2011; 85:11283-90. [PMID: 21880775 DOI: 10.1128/jvi.05597-11] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Coxsackievirus A24 variant (CVA24v) is a main causative agent of acute hemorrhagic conjunctivitis (AHC), which is a highly contagious eye infection. Previously it has been suggested that CVA24v uses sialic acid-containing glycoconjugates as attachment receptors on corneal cells, but the nature of these receptors is poorly described. Here, we set out to characterize and identify the cellular components serving as receptors for CVA24v. Binding and infection experiments using corneal cells treated with deglycosylating enzymes or metabolic inhibitors of de novo glycosylation suggested that the receptor(s) used by CVA24v are constituted by sialylated O-linked glycans that are linked to one or more cell surface proteins but not to lipids. CVA24v bound better to mouse L929 cells overexpressing human P-selectin glycoprotein ligand-1 (PSGL-1) than to mock-transfected cells, suggesting that PSGL-1 is a candidate receptor for CVA24v. Finally, binding competition experiments using a library of mono- and oligosaccharides mimicking known PSGL-1 glycans suggested that CVA24v binds to Neu5Acα2,3Gal disaccharides (Neu5Ac is N-acetylneuraminic acid). These results provide further insights into the early steps of the CVA24v life cycle.
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20
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Scavenger receptor class B type I and the hypervariable region-1 of hepatitis C virus in cell entry and neutralisation. Expert Rev Mol Med 2011; 13:e13. [PMID: 21489334 DOI: 10.1017/s1462399411001785] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hepatitis C virus (HCV) infection is a leading cause of chronic liver disease worldwide and represents a major public health problem. Viral attachment and entry - the first encounter of the virus with the host cell - are major targets of neutralising immune responses. Thus, a detailed understanding of the HCV entry process offers interesting opportunities for the development of novel therapeutic strategies. Different cellular or soluble host factors mediate HCV entry, and considerable progress has been made in recent years to decipher how they induce HCV attachment, internalisation and membrane fusion. Among these factors, the scavenger receptor class B type I (SR-BI/SCARB1) is essential for HCV replication in vitro, through its interaction with the HCV E1E2 surface glycoproteins and, more particularly, the HVR1 segment located in the E2 protein. SR-BI is an interesting receptor because HCV, whose replication cycle intersects with lipoprotein metabolism, seems to exploit some aspects of its physiological functions, such as cholesterol transfer from high-density lipoprotein (HDL), during cell entry. SR-BI is also involved in neutralisation attenuation and therefore could be an important target for therapeutic intervention. Recent results suggest that it should be possible to identify inhibitors of the interaction of HCV with SR-BI that do not impair its important physiological properties, as discussed in this review.
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Kent AP, Stylianou IM. Scavenger receptor class B member 1 protein: hepatic regulation and its effects on lipids, reverse cholesterol transport, and atherosclerosis. Hepat Med 2011; 3:29-44. [PMID: 24367219 PMCID: PMC3846864 DOI: 10.2147/hmer.s7860] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Scavenger receptor class B member 1 (SR-BI, also known as SCARB1) is the primary receptor for the selective uptake of cholesterol from high-density lipoprotein (HDL). SR-BI is present in several key tissues; however, its presence and function in the liver is deemed the most relevant for protection against atherosclerosis. Cholesterol is transferred from HDL via SR-BI to the liver, which ultimately results in the excretion of cholesterol via bile and feces in what is known as the reverse cholesterol transport pathway. Much of our knowledge of SR-BI hepatic function and regulation is derived from mouse models and in vitro characterization. Multiple independent regulatory mechanisms of SR-BI have been discovered that operate at the transcriptional and post-transcriptional levels. In this review we summarize the critical discoveries relating to hepatic SR-BI cholesterol metabolism, atherosclerosis, and regulation of SR-BI, as well as alternative functions that may indirectly affect atherosclerosis.
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Affiliation(s)
- Anthony P Kent
- Department of Medicine and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
| | - Ioannis M Stylianou
- Department of Medicine and Institute for Translational Medicine and Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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22
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Fioravanti J, Medina-Echeverz J, Berraondo P. Scavenger receptor class B, type I: a promising immunotherapy target. Immunotherapy 2011; 3:395-406. [DOI: 10.2217/imt.10.104] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Scavenger receptor class B, type I (SR-BI) is a crucial molecule in lipid metabolism, since the interaction of high-density lipoproteins (HDLs) with SR-BI is involved in reverse cholesterol transport and cholesterol efflux. Recent findings also underscore a critical role of SR-BI in antimicrobial and immune responses. SR-BI is not only highly expressed in liver and steroidogenic glands, but also in endothelial cells, macrophages and dendritic cells. SR-BI mainly mediates anti-inflammatory responses, which may be altered by dysfunctional HDLs produced in several diseases. Moreover, SR-BI has been involved in the capture and cross-presentation of antigens from viruses, bacteria and parasites. It thus works as a pattern-recognition receptor that interacts with both damage-associated molecular patterns and pathogen-associated molecular patterns. These new findings in the microbiology and immunology fields present SR-BI as an unexplored therapeutic target that warrants further basic and applied research.
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Affiliation(s)
- Jessica Fioravanti
- Division of Hepatology & Gene Therapy, Center for Applied Medical Research, University of Navarra, Pamplona, Navarra, Spain
| | - José Medina-Echeverz
- Division of Hepatology & Gene Therapy, Center for Applied Medical Research, University of Navarra, Pamplona, Navarra, Spain
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23
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Pandey KN. Small peptide recognition sequence for intracellular sorting. Curr Opin Biotechnol 2011; 21:611-20. [PMID: 20817434 DOI: 10.1016/j.copbio.2010.08.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 08/10/2010] [Accepted: 08/11/2010] [Indexed: 02/05/2023]
Abstract
Increasing evidence indicate that complex arrays of short signals and recognition peptide sequence ensure accurate trafficking and distribution of transmembrane receptors and/or proteins and their ligands into intracellular compartments. Internalization and subsequent trafficking of cell-surface receptors into the cell interior is mediated by specific short-sequence peptide signals within the cytoplasmic domains of these receptor proteins. The short signals usually consist of small linear amino acid sequences, which are recognized by adaptor coat proteins along the endocytic and sorting pathways. In recent years, much has been learned about the function and mechanisms of endocytic pathways responsible for the trafficking and molecular sorting of membrane receptors and their ligands into intracellular compartments, however, the significance and scope of the short-sequence motifs in these cellular events is not well understood. Here a particular emphasis has been given to the functions of short-sequence signal motifs responsible for the itinerary and destination of membrane receptors and proteins moving into subcellular compartments.
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Affiliation(s)
- Kailash N Pandey
- Department of Physiology, Tulane University Health Sciences Center, School of Medicine, New Orleans, LA 70112, USA.
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24
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Boeynaems JM, Sirtori CR. The unexpected roles of extracellular ADP and P2Y(13) receptor in reverse cholesterol transport. Purinergic Signal 2010; 6:361-3. [PMID: 21437006 DOI: 10.1007/s11302-010-9211-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 12/07/2010] [Indexed: 10/18/2022] Open
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25
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Hussain KM, Leong KLJ, Ng MML, Chu JJH. The essential role of clathrin-mediated endocytosis in the infectious entry of human enterovirus 71. J Biol Chem 2010; 286:309-21. [PMID: 20956521 DOI: 10.1074/jbc.m110.168468] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Little is currently known about the infectious entry process of human enterovirus 71 (HEV71) into host cells, which may represent potential anti-viral targeting sites. In this study a targeted small-interfering RNA (siRNA) screening platform assay was established and validated to identify and profile key cellular genes involved in processes of endocytosis, cytoskeletal dynamics, and endosomal trafficking essential for HEV71 infection. Screen evaluation was conducted via the expression of well characterized dominant-negative mutants, bioimaging studies (double-labeled immunofluorescence assays, transmission electron microscopy analysis), secondary siRNA-based dosage dependence studies, and drug inhibition assays. The infectious entry of HEV71 into rhabdomyosarcoma cells was shown to be significantly inhibited by siRNAs targeting genes associated with clathrin-mediated endocytosis (CME) that include AP2A1, ARRB1, CLTC, CLTCL1, SYNJ1, ARPC5, PAK1, ROCK1, and WASF1. The functional role of CME was verified by the observation of strong co-localization between HEV71 particles and clathrin as well as dose-dependent inhibition of HEV71 infection upon siRNA knockdown of CME-associated genes. HEV71 entry by CME was further confirmed via inhibition by dominant-negative EPS15 mutants and treatment of CME drug inhibitors, with more than 80% inhibition observed at 20 μm chlorpromazine. Furthermore, HEV71 infection was shown to be sensitive to the disruption of human genes in regulating early to late endosomal trafficking as well as endosomal acidic pH. The identification of clathrin-mediated endocytosis as the entry pathway for HEV71 infection of susceptible host cells contributes to a better understanding of HEV71 pathogenesis and enables future development of anti-viral strategies against HEV71 infection.
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Affiliation(s)
- Khairunnisa' Mohamed Hussain
- Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System, 5 Science Drive 2, National University of Singapore, Singapore 117597
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26
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Truong TQ, Aubin D, Falstrault L, Brodeur MR, Brissette L. SR-BI, CD36, and caveolin-1 contribute positively to cholesterol efflux in hepatic cells. Cell Biochem Funct 2010; 28:480-9. [DOI: 10.1002/cbf.1680] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Abstract
Over the past decade, Human enterovirus (HEV)71 has emerged as a highly significant cause of viral encephalitis in the south-east Asian region. A pattern of increased epidemic activity has been observable since 1997, the cause of which is unclear. Ongoing investigations into the molecular basis of HEV71 infection and virulence, in particular viral translation and replication, have confirmed similarities between HEV71 and other enteroviruses, including the prototype species Poliovirus, but more work is required in this field. Although several putative receptors for HEV71 have been identified, it remains likely that other, as yet unidentified, receptors exist. Work in several established animal models for HEV71 infection has confirmed the protective efficacy of several inactivated vaccines. As more information emerges regarding the molecular processes involved in HEV71 infection, further advances may lead to the development of more effective antiviral treatments and, ultimately, a vaccine protection strategy.
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Affiliation(s)
- Emily J Bek
- Infectious Diseases & Immunology, Sydney Medical School, Blackburn Building D06, The University of Sydney, NSW 2006, Australia
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Abstract
Hand, foot and mouth disease (HFMD) is generally a benign febrile exanthematous childhood disease caused by human enteroviruses. The route of transmission is postulated to be faeco-oral in developing areas but attributed more to respiratory droplet in developed areas. Transmission is facilitated by the prolonged environmental survival of these viruses and their greater resistance to biocides. Serious outbreaks with neurological and cardiopulmonary complications caused by human enterovirus 71 (HEV-71) seem to be commoner in the Asian Pacific region than elsewhere in the world. This geographical predilection is unexplained but could be related to the frequency of intra- and inter-typic genetic recombinations of the virus, the host populations' genetic predisposition, environmental hygiene, and standard of healthcare. Vaccine development could be hampered by the general mildness of the illness and rapid genetic evolution of the virus. Antivirals are not readily available; the role of intravenous immunoglobulin in the treatment of serious complications should be investigated. Monitoring of this disease and its epidemiology in the densely populated Asia Pacific epicentre is important for the detection of emerging epidemics due to enteroviruses.
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Abstract
Dysregulation of cholesterol balance contributes significantly to atherosclerotic cardiovascular disease (ASCVD), the leading cause of death in the United States. The intestine has the unique capability to act as a gatekeeper for entry of cholesterol into the body, and inhibition of intestinal cholesterol absorption is now widely regarded as an attractive non-statin therapeutic strategy for ASCVD prevention. In this chapter we discuss the current state of knowledge regarding sterol transport across the intestinal brush border membrane. The purpose of this work is to summarize substantial progress made in the last decade in regards to protein-mediated sterol trafficking, and to discuss this in the context of human disease.
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Affiliation(s)
| | - Liqing Yu
- Address correspondence to: Liqing Yu, M.D., Ph.D., Department of Pathology Section on Lipid Sciences, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157-1040, Tel: 336-716-0920, Fax: 336-716-6279,
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30
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Hong M, Li S, Zhou F, Thomas PE, You G. Putative transmembrane domain 12 of the human organic anion transporter hOAT1 determines transporter stability and maturation efficiency. J Pharmacol Exp Ther 2009; 332:650-8. [PMID: 19892921 DOI: 10.1124/jpet.109.160515] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human organic anion transporter hOAT1 plays a critical role in the body disposition of clinically important drugs. In transmembrane segment (TM) 12, residues Tyr-490 and dileucine Leu-503/Leu-504 were identified to be critical for hOAT1 function. Substitution of Tyr-490 with alanine led to a dramatic reduction in protein expression of hOAT1 and its transport activity. The contribution of the side chain of Tyr-490 to transport activity was then evaluated by replacing this residue with Trp or Phe. Substitution of Tyr-490 with Trp or Phe partially or fully recovered the protein expression of hOAT1 and its transport activity, respectively, that were lost by substitution of Tyr-490 with alanine, suggesting that the aromatic ring and the size of the side chain of Tyr-490 are critical for hOAT1 expression and function. Studies with protease inhibitors and pulse-chase labeling further showed that the loss of expression of hOAT1 and its transport activity by replacing Tyr-490 with alanine resulted from accelerated degradation of the transporter, whereas its maturation efficiency was not affected. In contrast to Tyr-490, substitution of Leu-503/Leu-504 with alanine also resulted in complete loss of protein expression of hOAT1 and its transport activity. However, such loss of protein expression could not be prevented by treating mutant-expressing cells with protease inhibitors. Pulse-chase experiments showed that the mutant transporter (L503/L504A) was trapped in the endoplasmic reticulum without conversion into mature form of the transporter. Our results are the first to highlight the central role of TM 12 in maintaining the stability and in promoting the maturation efficiency of hOAT1.
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Affiliation(s)
- Mei Hong
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
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31
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Scheri RC, Lee J, Barofsky DF, Curtis LR. Chlordecone increased subcellular distribution of scavenger receptor class B type II to murine hepatic microsomes without altering cytosolic cholesterol binding proteins. Toxicol Lett 2009; 191:20-5. [PMID: 19666090 DOI: 10.1016/j.toxlet.2009.07.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 07/30/2009] [Accepted: 07/30/2009] [Indexed: 10/20/2022]
Abstract
Pretreatment of male C57BL/6 mice with low doses of the persistent organochlorine pesticide, chlordecone (CD), stimulated biliary excretion of exogenous cholesterol (CH) up to 3-fold. Increased biliary excretion occurred without changes in hepatic ATP-binding cassette transporter G8 (ABCG8) of the bile canaliculus or scavenger receptor class B type I (SR-BI) of the sinusoidal surface. A variety of tissues express scavenger receptor class B type II (SR-BII) and this protein was identified as a splice variant from the SR-BI gene. Although the function of SR-BII has not been elucidated it may play a role in CH homeostasis and trafficking distinctly different than SR-BI. Western blotting demonstrated that a single dose of CD promoted subcellular distribution of SR-BII to murine hepatic microsomes about 2.2-fold when compared to controls without effect on liver crude membrane SR-BII content. This was consistent with increased vesicular CH trafficking. Relative quantification of hepatic cytosolic proteins in a fraction that sequestered [(14)C]CH by mass spectrometry (MS) indicated no role for cytosolic CH binding proteins in CD altered CH homeostasis. Western blotting verified no effect of CD on liver fatty acid-binding protein (L-FABP) in cytosol. MS detected a statistically significant increase in myosin-9, which was also consistent with increased vesicular trafficking.
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Affiliation(s)
- Richard C Scheri
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA
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32
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Affiliation(s)
- Kunal P Patel
- Division of Infectious Diseases, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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33
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Rohrer L, Ohnsorg PM, Lehner M, Landolt F, Rinninger F, von Eckardstein A. High-density lipoprotein transport through aortic endothelial cells involves scavenger receptor BI and ATP-binding cassette transporter G1. Circ Res 2009; 104:1142-50. [PMID: 19372466 DOI: 10.1161/circresaha.108.190587] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cholesterol efflux from macrophage foam cells is a rate-limiting step in reverse cholesterol transport. In this process cholesterol acceptors like high-density lipoproteins (HDL) and apolipoprotein (apo)A-I must cross the endothelium to get access to the donor cells in the arterial intima. Previously, we have shown that apoA-I passes a monolayer of aortic endothelial cells (ECs) from the apical to the basolateral side by transcytosis, which is modulated by the ATP-binding cassette transporter (ABC)A1. Here, we analyzed the interaction of mature HDL with ECs. ECs bind HDL in a specific and saturable manner. Both cell surface biotinylation experiments and immunofluorescence microscopy of HDL recovered approximately 30% of the cell-associated HDL intracellularly. Cultivated on inserts ECs bind, internalize, and translocate HDL from the apical to the basolateral compartment in a specific and temperature-dependent manner. The size of the translocated particle was reduced, but its protein moiety remained intact. Using RNA interference, we investigated the impact of SR-BI, ABCA1, and ABCG1 on binding, internalization, and transcytosis of HDL by ECs. HDL binding was reduced by 50% and 30% after silencing of SR-BI and ABCG1, respectively, but not at all after diminishing ABCA1 expression. Knock down of SR-BI and, even more so, ABCG1 reduced HDL transcytosis but did not affect inulin permeability. Cosilencing of both proteins did not further reduce HDL binding, internalization, or transport. In conclusion, ECs transcytose HDL by mechanisms that involve either SR-BI or ABCG1 but not ABCA1.
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Affiliation(s)
- Lucia Rohrer
- Institute of Clinical Chemistry, University Hospital Zurich, Rämistrasse 100, 8091 Zurich, Switzerland.
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34
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Dreux M, Dao Thi VL, Fresquet J, Guérin M, Julia Z, Verney G, Durantel D, Zoulim F, Lavillette D, Cosset FL, Bartosch B. Receptor complementation and mutagenesis reveal SR-BI as an essential HCV entry factor and functionally imply its intra- and extra-cellular domains. PLoS Pathog 2009; 5:e1000310. [PMID: 19229312 PMCID: PMC2636890 DOI: 10.1371/journal.ppat.1000310] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Accepted: 01/23/2009] [Indexed: 12/11/2022] Open
Abstract
HCV entry into cells is a multi-step and slow process. It is believed that the
initial capture of HCV particles by glycosaminoglycans and/or lipoprotein
receptors is followed by coordinated interactions with the scavenger receptor
class B type I (SR-BI), a major receptor of high-density lipoprotein (HDL), the
CD81 tetraspanin, and the tight junction protein Claudin-1, ultimately leading
to uptake and cellular penetration of HCV via low-pH endosomes.
Several reports have indicated that HDL promotes HCV entry through interaction
with SR-BI. This pathway remains largely elusive, although it was shown that HDL
neither associates with HCV particles nor modulates HCV binding to SR-BI. In
contrast to CD81 and Claudin-1, the importance of SR-BI has only been addressed
indirectly because of lack of cells in which functional complementation assays
with mutant receptors could be performed. Here we identified for the first time
two cell types that supported HCVpp and HCVcc entry upon ectopic SR-BI
expression. Remarkably, the undetectable expression of SR-BI in rat hepatoma
cells allowed unambiguous investigation of human SR-BI functions during HCV
entry. By expressing different SR-BI mutants in either cell line, our results
revealed features of SR-BI intracellular domains that influence HCV infectivity
without affecting receptor binding and stimulation of HCV entry induced by
HDL/SR-BI interaction. Conversely, we identified positions of SR-BI ectodomain
that, by altering HCV binding, inhibit entry. Finally, we characterized
alternative ectodomain determinants that, by reducing SR-BI cholesterol uptake
and efflux functions, abolish HDL-mediated infection-enhancement. Altogether, we
demonstrate that SR-BI is an essential HCV entry factor. Moreover, our results
highlight specific SR-BI determinants required during HCV entry and
physiological lipid transfer functions hijacked by HCV to favor infection. More than 180 million people are chronically infected by hepatitis C virus (HCV),
a leading cause of liver failure and cancer, stimulating the need to fully
define the biology of HCV infection for developing novel and effective
therapeutics. During the first steps of infection, the virus is taken up and
penetrates hepatocytes. HCV entry is thought to be a coordinated multi-step
process mediated by specific factors, including CD81, Claudin-1, and the
scavenger receptor BI (SR-BI). Whereas the involvement of CD81 and Claudin-1 was
demonstrated by rendering susceptible cells that are otherwise refractory, SR-BI
complementation assays were lacking, raising questions as to its functions
during HCV entry. Here, we identify one hepatoma rat cell line, in which SR-BI
complementation assay and targeted mutagenesis could be performed. We therefore
demonstrate that SR-BI is an essential HCV entry factor. Our results shed light
on SR-BI intracellular domain functions in HCV entry, and, further, emphasize
the remarkable capacity of HCV to hijack the lipid transfer function of SR-BI,
hence favoring infection.
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Affiliation(s)
- Marlène Dreux
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
| | - Viet Loan Dao Thi
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
| | - Judith Fresquet
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
| | | | | | - Géraldine Verney
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
| | - David Durantel
- Université de Lyon, UCB-Lyon1, IFR62; INSERM, U871; Hospices
civils de Lyon (HCL), Lyon, France
| | - Fabien Zoulim
- Université de Lyon, UCB-Lyon1, IFR62; INSERM, U871; Hospices
civils de Lyon (HCL), Lyon, France
| | - Dimitri Lavillette
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
| | - François-Loïc Cosset
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
- * E-mail:
| | - Birke Bartosch
- Université de Lyon, UCB-Lyon1, IFR128; INSERM, U758; Ecole
Normale Supérieure de Lyon, Lyon, France
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Fenske SA, Yesilaltay A, Pal R, Daniels K, Barker C, Quiñones V, Rigotti A, Krieger M, Kocher O. Normal hepatic cell surface localization of the high density lipoprotein receptor, scavenger receptor class B, type I, depends on all four PDZ domains of PDZK1. J Biol Chem 2008; 284:5797-806. [PMID: 19116202 DOI: 10.1074/jbc.m808211200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PDZK1 is a four PDZ domain-containing scaffold protein that binds to scavenger receptor class B, type I (SR-BI), the high density lipoprotein receptor, by its first PDZ domain (PDZ1). PDZK1 knock-out mice exhibit a >95% decrease in hepatic SR-BI protein and consequently an approximately 70% increase in plasma cholesterol in abnormally large high density lipoprotein particles. These defects are corrected by hepatic overexpression of full-length PDZK1 but not the PDZ1 domain alone, which partially restores SR-BI protein abundance but not cell surface expression or function. We have generated PDZK1 knock-out mice with hepatic expression of four PDZK1 transgenes encoding proteins with nested C-terminal truncations: pTEM, which lacks the three C-terminal residues (putative PDZ-binding motif), and PDZ1.2, PDZ1.2.3, or PDZ1.2.3.4, which contain only the first two, three, or four N-terminal PDZ domains, respectively, but not the remaining C-terminal sequences. Hepatic overexpression of pTEM restored normal hepatic SR-BI abundance, localization, and function. Hepatic overexpression of PDZ1.2 or PDZ1.2.3 partially restored SR-BI abundance ( approximately 12 or approximately 30% of wild type, respectively) but did not (PDZ1.2) or only slightly (PDZ1.2.3) restored hepatic SR-BI cell surface localization and function. Hepatic overexpression of PDZ1.2.3.4 completely restored SR-BI protein abundance, cell surface expression, and function (normalization of plasma cholesterol levels). Thus, all four PDZ domains in PDZK1, but not PDZ1-3 alone, are sufficient for its normal control of the abundance, localization, and therefore function of hepatic SR-BI, whereas the residues C-terminal to the PDZ4 domain, including the C-terminal putative PDZ-binding domain, are not required.
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Affiliation(s)
- Sara A Fenske
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Stamataki Z, Grove J, Balfe P, McKeating JA. Hepatitis C virus entry and neutralization. Clin Liver Dis 2008; 12:693-712, x. [PMID: 18625435 DOI: 10.1016/j.cld.2008.03.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The processes of hepatitis C virus (HCV) entry and antibody-mediated neutralization are intimately linked. The high frequency of neutralizing antibodies (nAbs) that inhibit E2-CD81 interaction(s) suggests that this is a major target for the humoral immune response. The observation that HCV can transmit to naive cells by means of CD81-dependent and -independent routes in vitro awaits further investigation to assess the significance in vivo but may offer new strategies for HCV to escape nAbs. The identification of claudins in the entry process highlights the importance of cell polarity in defining routes of HCV entry and release, with recent experiments suggesting a polarized route of viral entry into cells in vitro. In this review, the authors summarize the current understanding of the mechanism(s) defining HCV entry and the role of nAbs in controlling HCV replication.
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Affiliation(s)
- Zania Stamataki
- Division of Immunity and Infection, Institute for Biomedical Research, University of Birmingham, Edgbaston, UK
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37
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Zhang X, Merkler KA, McLean MP. Characterization of regulatory intronic and exonic sequences involved in alternative splicing of scavenger receptor class B gene. Biochem Biophys Res Commun 2008; 372:173-8. [DOI: 10.1016/j.bbrc.2008.05.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 05/02/2008] [Indexed: 01/04/2023]
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38
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Fenske SA, Yesilaltay A, Pal R, Daniels K, Rigotti A, Krieger M, Kocher O. Overexpression of the PDZ1 domain of PDZK1 blocks the activity of hepatic scavenger receptor, class B, type I by altering its abundance and cellular localization. J Biol Chem 2008; 283:22097-104. [PMID: 18544532 DOI: 10.1074/jbc.m800029200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PDZK1 is a four-PDZ domain-containing scaffold protein that, via its first PDZ domain (PDZ1), binds to the C terminus of the high density lipoprotein (HDL) receptor scavenger receptor, class B, type I (SR-BI). Abolishing PDZK1 expression in PDZK1 knock-out (KO) mice leads to a post-transcriptional, tissue-specific decrease in SR-BI protein level and an increase in total plasma cholesterol carried in abnormally large HDL particles. Here we show that, although hepatic overexpression of PDZK1 restored normal SR-BI protein abundance and function in PDZK1 KO mice, hepatic overexpression of only the PDZ1 domain was not sufficient to restore normal SR-BI function. In wild-type mice, overexpression of the PDZ1 domain overcame the activity of the endogenous hepatic PDZK1, resulting in a 75% reduction in hepatic SR-BI protein levels and intracellular mislocalization of the remaining SR-BI. As a consequence, the plasma lipoproteins in PDZ1 transgenic mice resembled those in PDZK1 KO mice (hypercholesterolemia due to large HDL). These results indicate that the PDZ1 domain can control the abundance and localization, and therefore the function, of hepatic SR-BI and that structural features of PDZK1 in addition to its SR-BI-binding PDZ1 domain are required for normal hepatic SR-BI regulation.
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Affiliation(s)
- Sara A Fenske
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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39
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Influence of PDZK1 on lipoprotein metabolism and atherosclerosis. Biochim Biophys Acta Mol Basis Dis 2008; 1782:310-6. [PMID: 18342019 DOI: 10.1016/j.bbadis.2008.02.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/15/2008] [Accepted: 02/01/2008] [Indexed: 11/23/2022]
Abstract
PDZK1 is a scaffold protein containing four PDZ protein interaction domains, which bind to the carboxy termini of a number of membrane transporter proteins, including ion channels (e.g., CFTR) and cell surface receptors. One of these, the HDL receptor, scavenger receptor class B type I (SR-BI), exhibits a striking, tissue-specific dependence on PDZK1 for its expression and activity. In PDZK1 knockout (KO) mice there is a marked reduction of SR-BI protein expression (approximately 95%) in the liver, but not in steroidogenic tissues or, as we show in this report, in bone marrow- or spleen-derived macrophages, or lung-derived endothelial cells. Because of hepatic SR-BI deficiency, PDZK1 KO mice exhibit dyslipidemia characterized by elevated plasma cholesterol carried in abnormally large HDL particles. Here, we show that inactivation of the PDZK1 gene promotes the development of aortic root atherosclerosis in apolipoprotein E (apoE) KO mice fed with a high fat/high cholesterol diet. However, unlike complete SR-BI-deficiency in SR-BI/apoE double KO mice, PDZK1 deficiency in PDZK1/apoE double knockout mice did not result in development of occlusive coronary artery disease or myocardial infarction, presumably because of their residual expression of SR-BI. These findings demonstrate that deficiency of an adaptor protein essential for normal expression of a lipoprotein receptor promotes atherosclerosis in a murine model. They also define PDZK1 as a member of the family of proteins that is instrumental in preventing cardiovascular disease by maintaining normal lipoprotein metabolism.
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Zeisel MB, Koutsoudakis G, Schnober EK, Haberstroh A, Blum HE, Cosset FL, Wakita T, Jaeck D, Doffoel M, Royer C, Soulier E, Schvoerer E, Schuster C, Stoll-Keller F, Bartenschlager R, Pietschmann T, Barth H, Baumert TF. Scavenger receptor class B type I is a key host factor for hepatitis C virus infection required for an entry step closely linked to CD81. Hepatology 2007; 46:1722-31. [PMID: 18000990 DOI: 10.1002/hep.21994] [Citation(s) in RCA: 211] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
UNLABELLED Hepatitis C virus (HCV) is a major cause of chronic hepatitis worldwide. Scavenger receptor class B type I (SR-BI) has been shown to bind HCV envelope glycoprotein E2, participate in entry of HCV pseudotype particles, and modulate HCV infection. However, the functional role of SR-BI for productive HCV infection remains unclear. In this study, we investigated the role of SR-BI as an entry factor for infection of human hepatoma cells using cell culture-derived HCV (HCVcc). Anti-SR-BI antibodies directed against epitopes of the human SR-BI extracellular loop specifically inhibited HCVcc infection in a dose-dependent manner. Down-regulation of SR-BI expression by SR-BI-specific short interfering RNAs (siRNAs) markedly reduced the susceptibility of human hepatoma cells to HCVcc infection. Kinetic studies demonstrated that SR-BI acts predominately after binding of HCV at an entry step occurring at a similar time point as CD81-HCV interaction. Although the addition of high-density lipoprotein (HDL) enhanced the efficiency of HCVcc infection, anti-SR-BI antibodies and SR-BI-specific siRNA efficiently inhibited HCV infection independent of lipoprotein. CONCLUSION Our data suggest that SR-BI (i) represents a key host factor for HCV entry, (ii) is implicated in the same HCV entry pathway as CD81, and (iii) targets an entry step closely linked to HCV-CD81 interaction.
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Affiliation(s)
- Mirjam B Zeisel
- Institut National de la Santé et de la Recherche Médicale (INSERM), U748, Strasbourg, France
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Zhang Y, Ahmed AM, Tran TL, Lin J, McFarlane N, Boreham DR, Igdoura SA, Truant R, Trigatti BL. The inhibition of endocytosis affects HDL-lipid uptake mediated by the human scavenger receptor class B type I. Mol Membr Biol 2007; 24:442-54. [PMID: 17710648 DOI: 10.1080/09687680701300410] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The scavenger receptor SR-BI plays an important role in the hepatic clearance of HDL cholesterol and other lipids, driving reverse cholesterol transport and contributing to protection against atherosclerosis in mouse models. We characterized the role of endocytosis in lipid uptake from HDL, mediated by the human SR-BI, using a variety of approaches to inhibit endocytosis, including hypertonic shock, potassium or energy depletion and disassembly of the actin cytoskeleton. Our studies revealed that unlike mouse SR-BI, human SR-BI-mediated HDL-lipid uptake was reduced by inhibition of endocytosis. This was not dependent on the cytoplasmic C-terminus of SR-BI. Monitoring the uptake of both the protein and lipid components of HDL revealed that although overall lipid uptake was decreased, the degree of selective lipid uptake was increased. These data suggest that that endocytosis is a dynamic regulator of SR-BI's selective lipid uptake activity.
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Affiliation(s)
- Yi Zhang
- Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada
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42
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Zhang X, Moor AN, Merkler KA, Liu Q, McLean MP. Regulation of alternative splicing of liver scavenger receptor class B gene by estrogen and the involved regulatory splicing factors. Endocrinology 2007; 148:5295-304. [PMID: 17673517 DOI: 10.1210/en.2007-0376] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The scavenger receptor class B isoforms (SR-B) type I and type II mediate the selective uptake of high-density lipoprotein cholesterol and promote reverse cholesterol transport, an important atherosclerosis protection mechanism, in the liver. Previously it was shown that the hepatic expression of SR-BI and SR-BII is regulated by estrogen. In the present study, we demonstrate that estrogen differentially regulates expression of the glycosylated and nonglycosylated forms of SR-BI and SR-BII in rat liver and hepatic cells. We report that estrogen mainly induces the down-regulation of glycosylated SR-BI and the up-regulation of nonglycosylated SR-BII. To study how estrogen regulates expression of the SR-B isoforms, we constructed a SR-B minigene containing minimal genomic sequences and were able to demonstrate that estrogen directly regulates the pre-mRNA alternative splicing of the exogenously expressed SR-B minigene in hepatic cells. Furthermore, we showed that the overexpression of splicing factors alternative splicing factor/splicing factor 2, Transformer (Tra)-2alpha, and Tra2beta changes the splicing pattern of SR-B dramatically, whereas other splicing factors, such as heterogeneous nuclear ribonucleoprotein-G, SC-35, and arginine/serine-rich p40, had no effect. We also demonstrate that estrogen regulates Tra2beta expression levels in liver cells. These studies suggest that estrogen may regulate SR-B isoform expression at both the RNA splicing and posttranslational modification levels and that, for alternative splicing regulation, estrogen may function by regulating the expression of the splicing factors alternative splicing factor/splicing factor 2, Tra2alpha, and especially Tra2beta.
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Affiliation(s)
- Xiaohui Zhang
- Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, FL 33612, USA
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Grove J, Huby T, Stamataki Z, Vanwolleghem T, Meuleman P, Farquhar M, Schwarz A, Moreau M, Owen JS, Leroux-Roels G, Balfe P, McKeating JA. Scavenger receptor BI and BII expression levels modulate hepatitis C virus infectivity. J Virol 2007; 81:3162-9. [PMID: 17215280 PMCID: PMC1866051 DOI: 10.1128/jvi.02356-06] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2006] [Accepted: 01/03/2007] [Indexed: 12/11/2022] Open
Abstract
Hepatitis C virus (HCV) enters cells via a pH- and clathrin-dependent endocytic pathway. Scavenger receptor BI (SR-BI) and CD81 are important entry factors for HCV internalization into target cells. The SR-BI gene gives rise to at least two mRNA splice variants, SR-BI and SR-BII, which differ in their C termini. SR-BI internalization remains poorly understood, but SR-BII is reported to endocytose via a clathrin-dependent pathway, making it an attractive target for HCV internalization. We demonstrate that HCV soluble E2 can interact with human SR-BI and SR-BII. Increased expression of SR-BI and SR-BII in the Huh-7.5 hepatoma cell line enhanced HCV strain J6/JFH and JFH infectivity, suggesting that endogenous levels of these receptors limit infection. Elevated expression of SR-BI, but not SR-BII, increased the rate of J6/JFH infection, which may reflect altered intracellular trafficking of the splice variants. In human plasma, HCV particles have been reported to be complexed with lipoproteins, suggesting an indirect interaction of the virus with SR-BI and other lipoprotein receptors. Plasma from J6/JFH-infected uPA-SCID mice transplanted with human hepatocytes demonstrates an increased infectivity for SR-BI/II-overexpressing Huh-7.5 cells. Plasma-derived J6/JFH infectivity was inhibited by an anti-E2 monoclonal antibody, suggesting that plasma virus interaction with SR-BI was glycoprotein dependent. Finally, anti-SR-BI antibodies inhibited the infectivity of cell culture- and plasma-derived J6/JFH, suggesting a critical role for SR-BI/II in HCV infection.
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Affiliation(s)
- Joe Grove
- Division of Immunity and Infection, Institute for Biomedical Research, The Medical School, Birmingham University, Edgbaston B14 2TT, United Kingdom
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Harder CJ, Meng A, Rippstein P, McBride HM, McPherson R. SR-BI undergoes cholesterol-stimulated transcytosis to the bile canaliculus in polarized WIF-B cells. J Biol Chem 2006; 282:1445-55. [PMID: 17105723 DOI: 10.1074/jbc.m604627200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The scavenger receptor BI (SR-BI) is highly expressed in hepatocytes, where it mediates the uptake of lipoprotein cholesterol, promotes the secretion of cholesterol into bile, and protects against atherosclerosis. Despite a strong correlation between the hepatic expression of SR-BI and biliary cholesterol secretion, little is known about SR-BI trafficking in response to changes in sterol availability. Using a well characterized polarized hepatocyte cell model, WIF-B, we determine that in cholesterol-depleted cells, SR-BI is extensively located on the basolateral surface, where it can access circulating lipoproteins. However, in response to cholesterol loading, SR-BI undergoes a slow transcytosis to the apical bile canaliculus independently of lipoprotein binding and new protein synthesis. In cholesterol-replete WIF-B cells, SR-BI that resides on the canalicular membrane is dynamically associated with defined microdomains and does not rapidly recycle to and from the subapical or basolateral regions. Taken together, these data demonstrate that hepatic SR-BI transcytosis is regulated by cholesterol and suggest that SR-BI has a stationary function on the bile canaliculus.
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Affiliation(s)
- Christopher J Harder
- Lipoprotein and Atherosclerosis Group, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada
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Voolstra O, Kiefer C, Hoehne M, Welsch R, Vogt K, von Lintig J. The Drosophila Class B Scavenger Receptor NinaD-I Is a Cell Surface Receptor Mediating Carotenoid Transport for Visual Chromophore Synthesis. Biochemistry 2006; 45:13429-37. [PMID: 17087496 DOI: 10.1021/bi060701u] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The blind Drosophila mutant ninaD lacks the visual chromophore. Genetic evidence that the molecular basis is a defect in carotenoid uptake which causes vitamin A deficiency exists. The ninaD gene encodes a scavenger receptor that is significantly homologous in sequence with the mammalian scavenger receptors SR-BI (scavenger receptor class B type I) and CD36 (cluster determinant 36), yet NinaD has not been characterized in functional detail. Therefore, we established a Drosophila S2 cell culture system for biochemically characterizing the ninaD gene products. We show that the two splice variant isoforms encoded by ninaD exhibit different subcellular localizations. NinaD-I, the long protein variant, is localized at the plasma membrane, whereas the short variant, NinaD-II, is localized at intracellular membranes. Only NinaD-I could mediate the cellular uptake of carotenoids from micelles in this cell culture system. Carotenoid uptake was concentration-dependent and saturable. By in vivo analyses of different mutant and transgenic fly strains, we provide evidence of an essential role of NinaD-I in the absorption of dietary carotenoids to support visual chromophore synthesis. Moreover, our analyses suggest a role of NinaD-I in tocopherol metabolism. Even though Drosophila is a sterol auxotroph, we found no evidence of a contribution of NinaD-I to the uptake of these compounds. Together, our study establishes an evolutionarily conserved connection between class B scavenger receptors and the numerous functions of fat soluble vitamins in animal physiology.
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Affiliation(s)
- Olaf Voolstra
- Institute of Biology I, University of Freiburg, Hauptstrasse 1, D-79104 Freiburg im Breisgau, Germany
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Chen Y, Wang X, Ben J, Yue S, Bai H, Guan X, Bai X, Jiang L, Ji Y, Fan L, Chen Q. The Di-Leucine Motif Contributes to Class A Scavenger Receptor-Mediated Internalization of Acetylated Lipoproteins. Arterioscler Thromb Vasc Biol 2006; 26:1317-22. [PMID: 16574888 DOI: 10.1161/01.atv.0000220171.50282.0c] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective—
The di-leucine motif exists in the intracellular domains of certain cell surface receptors, participating in the receptor-mediated endocytosis. The present study was aimed at determining the role of the di-leucine motif in class A scavenger receptor (SR-A)-mediated ligand endocytosis.
Methods and Results—
cDNA coding for a mutant (SR-A mutant N3132LM) with deletion of the di-leucine structure was transfected into Chinese hamster ovary (CHO) cells. Compared with wild-type SR-A–expressing cells, the cells expressing the SR-A mutant N3132LM showed a significant decrease in uptake but almost no change in binding of the SR-A ligand acetylated low-density lipoprotein (AcLDL). Western blot analysis revealed coimmunoprecipitation of SR-A mutant and clathrin from the lysates of the mutant but not wild-type CHO cells, suggesting that AcLDL-bound SR-A mutant N3132LM is associated with the clathrin-coated pit of cellular membrane. Removal of the first 27 amino acid residues from the SR-A N-terminus further reduced AcLDL uptake by the cells with the di-leucine motif mutation.
Conclusions—
The di-leucine motif of SR-A intracellular domain contributes to the SR-A–mediated cellular internalization of AcLDL. Di-leucine pair exists in the cytoplasmic domain of class A scavenger receptor. The cells expressing di-leucine mutants showed decreased uptake and unchanged binding of AcLDL. The di-leucine pair was not associated to coated pits. It suggests that di-leucine motif acts as a signal sequence to mediate SR-A into cell.
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Affiliation(s)
- Yaoyu Chen
- Institute of Reproductive Medicine, Nanjing Medical University, Nanjing, People's Republic of China
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