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Chen JJ, Fan Y, Boehning D. Regulation of Dynamic Protein S-Acylation. Front Mol Biosci 2021; 8:656440. [PMID: 33981723 PMCID: PMC8107437 DOI: 10.3389/fmolb.2021.656440] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 02/16/2021] [Indexed: 12/20/2022] Open
Abstract
Protein S-acylation is the reversible addition of fatty acids to the cysteine residues of target proteins. It regulates multiple aspects of protein function, including the localization to membranes, intracellular trafficking, protein interactions, protein stability, and protein conformation. This process is regulated by palmitoyl acyltransferases that have the conserved amino acid sequence DHHC at their active site. Although they have conserved catalytic cores, DHHC enzymes vary in their protein substrate selection, lipid substrate preference, and regulatory mechanisms. Alterations in DHHC enzyme function are associated with many human diseases, including cancers and neurological conditions. The removal of fatty acids from acylated cysteine residues is catalyzed by acyl protein thioesterases. Notably, S-acylation is now known to be a highly dynamic process, and plays crucial roles in signaling transduction in various cell types. In this review, we will explore the recent findings on protein S-acylation, the enzymatic regulation of this process, and discuss examples of dynamic S-acylation.
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2
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Rudd CE. How the Discovery of the CD4/CD8-p56 lck Complexes Changed Immunology and Immunotherapy. Front Cell Dev Biol 2021; 9:626095. [PMID: 33791292 PMCID: PMC8005572 DOI: 10.3389/fcell.2021.626095] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 01/11/2021] [Indexed: 12/22/2022] Open
Abstract
The past 25 years have seen enormous progress in uncovering the receptors and signaling mechanisms on T-cells that activate their various effecter functions. Until the late 1980s, most studies on T-cells had focused on the influx of calcium and the levels of cAMP/GMP in T-cells. My laboratory then uncovered the interaction of CD4 and CD8 co-receptors with the protein-tyrosine kinase p56lck which are now widely accepted as the initiators of the tyrosine phosphorylation cascade leading to T-cell activation. The finding explained how immune recognition receptors expressed by many immune cells, which lack intrinsic catalytic activity, can transduce activation signals via non-covalent association with non-receptor tyrosine kinases. The discovery also established the concept that a protein tyrosine phosphorylation cascade operated in T-cells. In this vein, we and others then showed that the CD4- and CD8-p56lck complexes phosphorylate the TCR complexes which led to the identification of other protein-tyrosine kinases such as ZAP-70 and an array of substrates that are now central to studies in T-cell immunity. Other receptors such as B-cell receptor, Fc receptors and others were also subsequently found to use src kinases to control cell growth. In T-cells, p56lck driven phosphorylation targets include co-receptors such as CD28 and CTLA-4 and immune cell-specific adaptor proteins such as LAT and SLP-76 which act to integrate signals proximal to surface receptors. CD4/CD8-p56lck regulated events in T-cells include intracellular calcium mobilization, integrin activation and the induction of transcription factors for gene expression. Lastly, the identification of the targets of p56lck in the TCR and CD28 provided the framework for the development of chimeric antigen receptor (CAR) therapy in the treatment of cancer. In this review, I outline a history of the development of events that led to the development of the “TCR signaling paradigm” and its implications to immunology and immunotherapy.
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Affiliation(s)
- Christopher E Rudd
- Division of Immunology-Oncology, Centre de Recherche Hôpital Maisonneuve-Rosemont (CR-HMR), Montreal, QC, Canada.,Department of Microbiology, Infection and Immunology, Faculty of Medicine, Universite de Montreal, Montreal, QC, Canada.,Division of Experimental Medicine, Department of Medicine, McGill University Health Center, McGill University, Montreal, QC, Canada
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3
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Yin SS, Gao FH. Molecular Mechanism of Tumor Cell Immune Escape Mediated by CD24/Siglec-10. Front Immunol 2020; 11:1324. [PMID: 32765491 PMCID: PMC7379889 DOI: 10.3389/fimmu.2020.01324] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 05/26/2020] [Indexed: 12/11/2022] Open
Abstract
Tumor immune escape is an important part of tumorigenesis and development. Tumor cells can develop a variety of immunosuppressive mechanisms to combat tumor immunity. Exploring tumor cells that escape immune surveillance through the molecular mechanism of related immunosuppression in-depth is helpful to develop the treatment strategies of targeted tumor immune escape. The latest studies show that CD24 on the surface of tumor cells interacts with Siglec-10 on the surface of immune cells to promote the immune escape of tumor cells. It is necessary to comment on the molecular mechanism of inhibiting the activation of immune cells through the interaction between CD24 on tumor cells and Siglec-10 on immune cells, and a treatment strategy of tumors through targeting CD24 on the surface of tumor cells or Siglec-10 on immune cells.
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Affiliation(s)
- Shan-Shan Yin
- Department of Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Feng-Hou Gao
- Department of Oncology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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4
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Gilson RC, Gunasinghe SD, Johannes L, Gaus K. Galectin-3 modulation of T-cell activation: mechanisms of membrane remodelling. Prog Lipid Res 2019; 76:101010. [PMID: 31682868 DOI: 10.1016/j.plipres.2019.101010] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 09/24/2019] [Accepted: 09/29/2019] [Indexed: 12/15/2022]
Abstract
Galectin-3 (Gal3) is a multifaceted protein which belongs to a family of lectins and binds β-galactosides. Gal3 expression is altered in many types of cancer, with increased expression generally associated with poor prognosis. Although the mechanisms remain unknown, Gal3 has been implicated in several biological processes involved in cancer progression, including suppression of T cell-mediated immune responses. Extracellular Gal3 binding to the plasma membrane of T cells alters membrane organization and the formation of an immunological synapse. Its multivalent capacity allows Gal3 to interact specifically with different membrane proteins and lipids, influencing endocytosis, trafficking and T cell receptor signalling. The ability of Gal3 to inhibit T cell responses may provide a mechanism by which Gal3 aids in cancer progression. In this review, we seek to give an overview of the mechanisms by which Gal3 alters the spatial organization of cell membranes and how these processes impact on T cell activation.
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Affiliation(s)
- Rebecca C Gilson
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney 2052, Australia; ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Sachith D Gunasinghe
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney 2052, Australia; ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Ludger Johannes
- Institut Curie, PSL Research University, Cellular and Chemical Biology unit, UMR3666, CNRS, U1143, INSERM, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney 2052, Australia; ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia.
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5
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Oncogenic KRas mobility in the membrane and signaling response. Semin Cancer Biol 2019; 54:109-113. [DOI: 10.1016/j.semcancer.2018.02.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/21/2018] [Accepted: 02/26/2018] [Indexed: 12/12/2022]
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6
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Albracht-Schulte K, Kalupahana NS, Ramalingam L, Wang S, Rahman SM, Robert-McComb J, Moustaid-Moussa N. Omega-3 fatty acids in obesity and metabolic syndrome: a mechanistic update. J Nutr Biochem 2018; 58:1-16. [PMID: 29621669 DOI: 10.1016/j.jnutbio.2018.02.012] [Citation(s) in RCA: 166] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 01/24/2018] [Accepted: 02/22/2018] [Indexed: 02/06/2023]
Abstract
Strategies to reduce obesity have become public health priorities as the prevalence of obesity has risen in the United States and around the world. While the anti-inflammatory and hypotriglyceridemic properties of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) are well known, their antiobesity effects and efficacy against metabolic syndrome, especially in humans, are still under debate. In animal models, evidence consistently suggests a role for n-3 PUFAs in reducing fat mass, particularly in the retroperitoneal and epididymal regions. In humans, however, published research suggests that though n-3 PUFAs may not aid weight loss, they may attenuate further weight gain and could be useful in the diet or as a supplement to help maintain weight loss. Proposed mechanisms by which n-3 PUFAs may work to improve body composition and counteract obesity-related metabolic changes include modulating lipid metabolism; regulating adipokines, such as adiponectin and leptin; alleviating adipose tissue inflammation; promoting adipogenesis and altering epigenetic mechanisms.
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Affiliation(s)
- Kembra Albracht-Schulte
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA
| | - Nishan Sudheera Kalupahana
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA; Department of Physiology, Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka.
| | - Latha Ramalingam
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA
| | - Shu Wang
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA
| | - Shaikh Mizanoor Rahman
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA
| | - Jacalyn Robert-McComb
- Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA; Department of Kinesiology, Texas Tech University, Lubbock, TX, USA
| | - Naima Moustaid-Moussa
- Department of Nutritional Sciences, Texas Tech University, Lubbock, TX, USA; Obesity Research Cluster, Texas Tech University, Lubbock, TX, USA.
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7
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Bustos-Morán E, Blas-Rus N, Martín-Cófreces NB, Sánchez-Madrid F. Orchestrating Lymphocyte Polarity in Cognate Immune Cell-Cell Interactions. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 327:195-261. [PMID: 27692176 DOI: 10.1016/bs.ircmb.2016.06.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The immune synapse (IS) is a specialized structure established between different immune cells that fulfills several functions, including a role as a communication bridge. This intimate contact between a T cell and an antigen-presenting cell promotes the proliferation and differentiation of lymphocytes involved in the contact. T-cell activation requires the specific triggering of the T-cell receptor (TCR), which promotes the activation of different signaling pathways inducing the polarization of the T cell. During this process, different adhesion and signaling receptors reorganize at specialized membrane domains, concomitantly to the polarization of the tubulin and actin cytoskeletons, forming stable polarization platforms. The centrosome also moves toward the IS, driving the movement of different organelles, such as the biosynthetic, secretory, degrading machinery, and mitochondria, to sustain T-cell activation. A proper orchestration of all these events is essential for T-cell effector functions and the accomplishment of a complete immune response.
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Affiliation(s)
- Eugenio Bustos-Morán
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain
| | - Noelia Blas-Rus
- Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
| | - Noa Beatriz Martín-Cófreces
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain.,Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
| | - Francisco Sánchez-Madrid
- Vascular Pathophysiology Area, Spanish National Center of Cardiovascular Research (CNIC), Madrid, Spain.,Department of Immunology, La Princesa Hospital, Autonomus University of Madrid (UAM), Health Research Institute of Princesa Hospital (ISS-IP), Madrid, Spain
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8
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Jan HM, Chen YC, Shih YY, Huang YC, Tu Z, Ingle AB, Liu SW, Wu MS, Gervay-Hague J, Mong KKT, Chen YR, Lin CH. Metabolic labelling of cholesteryl glucosides in Helicobacter pylori reveals how the uptake of human lipids enhances bacterial virulence. Chem Sci 2016; 7:6208-6216. [PMID: 30034762 PMCID: PMC6024656 DOI: 10.1039/c6sc00889e] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 05/28/2016] [Indexed: 12/30/2022] Open
Abstract
Helicobacter pylori infects approximately half of the human population and is the main cause of various gastric diseases. This pathogen is auxotrophic for cholesterol, which it converts upon uptake to various cholesteryl α-glucoside derivatives, including cholesteryl 6'-acyl and 6'-phosphatidyl α-glucosides (CAGs and CPGs). Owing to a lack of sensitive analytical methods, it is not known if CAGs and CPGs play distinct physiological roles or how the acyl chain component affects function. Herein we established a metabolite-labelling method for characterising these derivatives qualitatively and quantitatively with a femtomolar detection limit. The development generated an MS/MS database of CGds, allowing for profiling of all the cholesterol-derived metabolites. The subsequent analysis led to the unprecedented information that these bacteria acquire phospholipids from the membrane of epithelial cells for CAG biosynthesis. The resulting increase in longer or/and unsaturated CAG acyl chains helps to promote lipid raft formation and thus delivery of the virulence factor CagA into the host cell, supporting the idea that the host/pathogen interplay enhances bacterial virulence. These findings demonstrate an important connection between the chain length of CAGs and the bacterial pathogenicity.
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Affiliation(s)
- Hau-Ming Jan
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan . .,Institute of Biochemical Sciences and Department of Chemistry , National Taiwan University , Taipei , 10617 , Taiwan
| | - Yi-Chi Chen
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan . .,Institute of Biochemical Sciences and Department of Chemistry , National Taiwan University , Taipei , 10617 , Taiwan
| | - Yu-Yin Shih
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan .
| | - Yu-Chen Huang
- Agriculture Biotechnology Research Center , Academia Sinica , Taipei , 11529 , Taiwan
| | - Zhijay Tu
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan .
| | - Arun B Ingle
- Department of Applied Chemistry , National Chiao-Tung University , Hsin-Chu 300 , Taiwan
| | - Sheng-Wen Liu
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan .
| | - Ming-Shiang Wu
- Division of Gastroenterology , Department of Internal Medicine , National Taiwan University Hospital , Taipei , 10002 , Taiwan
| | | | - Kwok-Kong Tony Mong
- Department of Applied Chemistry , National Chiao-Tung University , Hsin-Chu 300 , Taiwan
| | - Yet-Ran Chen
- Agriculture Biotechnology Research Center , Academia Sinica , Taipei , 11529 , Taiwan
| | - Chun-Hung Lin
- Institute of Biological Chemistry , Academia Sinica , No. 128 Academia Road Section 2, Nan-Kang , Taipei , 11529 , Taiwan . .,Institute of Biochemical Sciences and Department of Chemistry , National Taiwan University , Taipei , 10617 , Taiwan
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9
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Abstract
The hypothesis that the Golgi apparatus is capable of sorting proteins and sending them to the plasma membrane through "lipid rafts," membrane lipid domains highly enriched in glycosphingolipids, sphingomyelin, ceramide, and cholesterol, was formulated by van Meer and Simons in 1988 and came to a turning point when it was suggested that lipid rafts could be isolated thanks to their resistance to solubilization by some detergents, namely Triton X-100. An incredible number of papers have described the composition and properties of detergent-resistant membrane fractions. However, the use of this method has also raised the fiercest criticisms. In this chapter, we would like to discuss the most relevant methodological aspects related to the preparation of detergent-resistant membrane fractions, and to discuss the importance of discriminating between what is present on a cell membrane and what we can prepare from cell membranes in a laboratory tube.
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10
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Horejsi V, Hrdinka M. Membrane microdomains in immunoreceptor signaling. FEBS Lett 2014; 588:2392-7. [DOI: 10.1016/j.febslet.2014.05.047] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/26/2014] [Accepted: 05/28/2014] [Indexed: 11/26/2022]
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11
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Abstract
The cell type of election for the study of cell membranes, the mammalian non-nucleated erythrocyte, has been scarcely considered in the research of membrane rafts of the plasma membrane. However, detergent-resistant-membranes (DRM) were actually first described in human erythrocytes, as a fraction resisting solubilization by the nonionic detergent Triton X-100. These DRMs were insoluble entities of high density, easily pelleted by centrifugation, as opposed to the now accepted concept of lipid raft-like membrane fractions as material floating in low-density regions of sucrose gradients. The present article reviews the available literature on membrane rafts/DRMs in human erythrocytes from an historical point of view, describing the experiments that provided the solution to the above described discrepancy and suggesting possible avenue of research in the field of membrane rafts that, moving from the most studied model of living cell membrane, the erythrocyte's, could be relevant also for other cell types.
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Affiliation(s)
- Annarita Ciana
- Laboratories of Biochemistry, Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia , Pavia , Italy
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12
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The productive entry pathway of HIV-1 in macrophages is dependent on endocytosis through lipid rafts containing CD4. PLoS One 2014; 9:e86071. [PMID: 24465876 PMCID: PMC3899108 DOI: 10.1371/journal.pone.0086071] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 12/05/2013] [Indexed: 12/20/2022] Open
Abstract
Macrophages constitute an important reservoir of HIV-1 infection, yet HIV-1 entry into these cells is poorly understood due to the difficulty in genetically manipulating primary macrophages. We developed an effective genetic approach to manipulate the sub-cellular distribution of CD4 in macrophages, and investigated how this affects the HIV-1 entry pathway. Pluripotent Stem Cells (PSC) were transduced with lentiviral vectors designed to manipulate CD4 location and were then differentiated into genetically modified macrophages. HIV-1 infection of these cells was assessed by performing assays that measure critical steps of the HIV-1 lifecycle (fusion, reverse transcription, and expression from HIV-1 integrants). Expression of LCK (which tethers CD4 to the surface of T cells, but is not normally expressed in macrophages) in PSC-macrophages effectively tethered CD4 at the cell surface, reducing its normal endocytic recycling route, and increasing surface CD4 expression 3-fold. This led to a significant increase in HIV-1 fusion and reverse transcription, but productive HIV-1 infection efficiency (as determined by reporter expression from DNA integrants) was unaffected. This implies that surface-tethering of CD4 sequesters HIV-1 into a pathway that is unproductive in macrophages. Secondly, to investigate the importance of lipid rafts (as detergent resistant membranes - DRM) in HIV-1 infection, we generated genetically modified PSC-macrophages that express CD4 mutants known to be excluded from DRM. These macrophages were significantly less able to support HIV-1 fusion, reverse-transcription and integration than engineered controls. Overall, these results support a model in which productive infection by HIV-1 in macrophages occurs via a CD4-raft-dependent endocytic uptake pathway.
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Abstract
Tyrosine phosphorylation is one of the key covalent modifications that occur in multicellular organisms. Since its discovery more than 30 years ago, tyrosine phosphorylation has come to be understood as a fundamentally important mechanism of signal transduction and regulation in all eukaryotic cells. The tyrosine kinase Lck (lymphocyte-specific protein tyrosine kinase) plays a crucial role in the T-cell response by transducing early activation signals triggered by TCR (T-cell receptor) engagement. These signals result in the phosphorylation of immunoreceptor tyrosine-based activation motifs present within the cytosolic tails of the TCR-associated CD3 subunits that, once phosphorylated, serve as scaffolds for the assembly of a large supramolecular signalling complex responsible for T-cell activation. The existence of membrane nano- or micro-domains or rafts as specialized platforms for protein transport and cell signalling has been proposed. The present review discusses the signals that target Lck to membrane rafts and the importance of these specialized membranes in the transport of Lck to the plasma membrane, the regulation of Lck activity and the phosphorylation of the TCR.
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Byrum JN, Van Komen JS, Rodgers W. CD28 sensitizes TCR Ca²⁺ signaling during Ag-independent polarization of plasma membrane rafts. THE JOURNAL OF IMMUNOLOGY 2013; 191:3073-81. [PMID: 23966623 DOI: 10.4049/jimmunol.1300485] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
T cells become polarized during initial interactions with an APC to form an Ag-independent synapse (AIS) composed of membrane rafts, TCR, and TCR-proximal signaling molecules. AISs occur temporally before TCR triggering, but their role in downstream TCR signaling is not understood. Using both human and murine model systems, we studied the signals that activate AIS formation and the effect of these signals on TCR-dependent responses. We show that CD28 produces AISs detectable by spinning disc confocal microscopy seconds following initial interactions between the T cell and APC. AIS formation by CD28 coincided with costimulatory signaling, evidenced by a cholesterol-sensitive activation of the MAPK ERK that potentiated Ca²⁺ signaling in response to CD3 cross-linking. CD45 also enriched in AISs but to modulate Src kinase activity, because localization of CD45 at the cell interface reduced the activation of proximal Lck. In summary, we show that signaling by CD28 during first encounters between the T cell and APC both sensitizes TCR Ca²⁺ signaling by an Erk-dependent mechanism and drives formation of an AIS that modulates the early signaling until TCR triggering occurs. Thus, early Ag-independent encounters are an important window for optimizing T cell responses to Ag by CD28.
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Affiliation(s)
- Jennifer N Byrum
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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15
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Funkhouser CM, Mayer M, Solis FJ, Thornton K. Effects of interleaflet coupling on the morphologies of multicomponent lipid bilayer membranes. J Chem Phys 2013; 138:024909. [DOI: 10.1063/1.4773856] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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16
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Zeidman R, Buckland G, Cebecauer M, Eissmann P, Davis DM, Magee AI. DHHC2 is a protein S-acyltransferase for Lck. Mol Membr Biol 2012; 28:473-86. [PMID: 22034844 DOI: 10.3109/09687688.2011.630682] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lck is a non-receptor tyrosine kinase of the Src family that is essential for T cell activation. Dual N-terminal acylation of Lck with myristate (N-acylation) and palmitate (S-acylation) is essential for its membrane association and function. Reversible S-acylation of Lck is observed in vivo and may function as a control mechanism. Here we identify the DHHC family protein S-acyltransferase DHHC2 as an enzyme capable of palmitoylating of Lck in T cells. Reducing the DHHC2 level in Jurkat T cells using siRNA causes decreased Lck S-acylation and partial dislocation from membranes, and conversely overexpression of DHHC2 increases S-acylation of an Lck surrogate, LckN10-GFP. DHHC2 localizes primarily to the endoplasmic reticulum and Golgi apparatus suggesting that it is involved in S-acylation of newly-synthesized or recycling Lck involved in T cell signalling.
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Affiliation(s)
- Ruth Zeidman
- Molecular Medicine Section, National Heart & Lung Institute, Imperial College London, Sir Alexander Fleming Building, South Kensington, London, UK
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17
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Smith AW. Lipid–protein interactions in biological membranes: A dynamic perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:172-7. [DOI: 10.1016/j.bbamem.2011.06.015] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 06/21/2011] [Accepted: 06/23/2011] [Indexed: 01/31/2023]
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18
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Agüera-González S, Gross CC, Fernández-Messina L, Ashiru O, Esteso G, Hang HC, Reyburn HT, Long EO, Valés-Gómez M. Palmitoylation of MICA, a ligand for NKG2D, mediates its recruitment to membrane microdomains and promotes its shedding. Eur J Immunol 2011; 41:3667-76. [PMID: 21928280 PMCID: PMC3709245 DOI: 10.1002/eji.201141645] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 08/08/2011] [Accepted: 09/15/2011] [Indexed: 11/05/2022]
Abstract
MICA and MICB (MHC-class-I-related chain A/B) are transmembrane proteins expressed in pathological conditions that are ligands for NKG2D, an activating receptor found on cytotoxic lymphocytes. The recognition on target cells of NKG2D ligands leads to the activation of lysis and cytokine secretion by NK cells and T cells. Besides being expressed at the cell surface, MICA/B can be released as soluble proteins. Soluble NKG2D ligands downmodulate expression of the NKG2D receptor on lymphocytes, leading to a diminished cytotoxic response. Prior studies suggested that recruitment of MICA/B molecules to cholesterol-enriched microdomains was an important factor regulating the proteolytic release of these molecules. We now show that recruitment of MICA to these microdomains depends on palmitoylation of two cysteine residues that allow MICA molecules to reside in the membrane in the same domains as caveolin-1. Compared with WT molecules, nonpalmitoylated mutant MICA molecules were shed to the supernatant with low efficiency; however, both WT and mutant MICA were able to trigger NK cell cytotoxicity. These data suggest that the presence of NKG2D ligands at the plasma membrane is sufficient to activate cytotoxicity and reflect the need of different ligands to exploit different cellular pathways to reach the cell surface upon different stress situations.
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Affiliation(s)
- Sonia Agüera-González
- Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Catharina C. Gross
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA
| | - Lola Fernández-Messina
- Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK
- Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
| | - Omodele Ashiru
- Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Gloria Esteso
- Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
| | - Howard C. Hang
- The Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University, New York, NY, USA
| | - Hugh T. Reyburn
- Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
| | - Eric O. Long
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA
| | - Mar Valés-Gómez
- Division of Immunology, Department of Pathology, University of Cambridge, Cambridge, UK
- Centro Nacional de Biotecnología/Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
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CD8αα and -αβ isotypes are equally recruited to the immunological synapse through their ability to bind to MHC class I. EMBO Rep 2011; 12:1251-6. [PMID: 22081144 DOI: 10.1038/embor.2011.209] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 09/22/2011] [Accepted: 09/23/2011] [Indexed: 11/08/2022] Open
Abstract
Bimolecular fluorescence complementation was used to engineer CD8 molecules so that CD8αα and CD8αβ dimers can be independently visualized on the surface of a T cell during antigen recognition. Using this approach, we show that CD8αα is recruited to the immunological synapse almost as well as CD8αβ, but because the kinase Lck associates preferentially with CD8αβ in lipid rafts, CD8αα is the weaker co-receptor. During recognition of the strong CD8αα ligand H2-TL, CD8αα is preferentially recruited. Thus, recruitment of the two CD8 species correlates with their relative binding to the available ligands, rather than with the co-receptor functions of the CD8 species.
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20
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Chichili GR, Rodgers W. Cytoskeleton-membrane interactions in membrane raft structure. Cell Mol Life Sci 2009; 66:2319-28. [PMID: 19370312 PMCID: PMC2709161 DOI: 10.1007/s00018-009-0022-6] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 02/26/2009] [Accepted: 03/12/2009] [Indexed: 12/22/2022]
Abstract
Cell membranes are structurally heterogeneous, composed of discrete domains with unique physical and biological properties. Membrane domains can form through a number of mechanisms involving lipid-lipid and protein-lipid interactions. One type of membrane domain is the cholesterol-dependent membrane raft. How rafts form remains a current topic in membrane biology. We review here evidence of structuring of rafts by the cortical actin cytoskeleton. This includes evidence that the actin cytoskeleton associates with rafts, and that many of the structural and functional properties of rafts require an intact actin cytoskeleton. We discuss the mechanisms of the actin-dependent raft organization, and the properties of the actin cytoskeleton in regulating raft-associated signaling events. We end with a discussion of membrane rafts and the actin cytoskeleton in T cell activation, which function synergistically to initiate the adaptive immune response.
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Affiliation(s)
- Gurunadh R. Chichili
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, 825 NE 13th St., MS 45, Oklahoma City, OK 73104 USA
| | - William Rodgers
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, 825 NE 13th St., MS 45, Oklahoma City, OK 73104 USA
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21
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Myelin, DIGs, and membrane rafts in the central nervous system. Prostaglandins Other Lipid Mediat 2009; 91:118-29. [PMID: 19379822 DOI: 10.1016/j.prostaglandins.2009.04.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 04/08/2009] [Accepted: 04/09/2009] [Indexed: 11/21/2022]
Abstract
Over the past 40 years our understanding of the organization of cell membranes has changed dramatically. Membranes are no longer viewed as a homogenous sea of phospholipids studded with randomly positioned islands of proteins. Our current view of the membrane involves the formation of small lipid clusters, comprised mainly of cholesterol and sphingolipids, known as membrane rafts. These lipid clusters apparently include and exclude specific proteins leading to the hypothesis that these domains (1) regulate cellular polarity and compartmentalization through trafficking and sorting, (2) provide platforms for cellular signaling and adhesion, and (3) function as cellular gate keepers. Tremendous controversy surrounds the concept of membrane rafts primarily because these small, highly dynamic entities are too small to be observed with traditional microscopic methods and the most utilized approach for raft analysis relies on poorly quantified, inconsistent biochemical extractions. New analytical approaches are being developed and applied to the study of membrane rafts and these techniques provide great promise for furthering our understanding of these enigmatic domains. In this review we will provide a brief summary of the current understanding of membrane rafts, utilizing the CNS myelin literature for illustrative purposes, and present caveats that should be considered when studying these domains.
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Lalazar G, Ben Ya'acov A, Eliakim-Raz N, Livovsky DM, Pappo O, Preston S, Zolotarov L, Ilan Y. β-Glycosphingolipids-mediated lipid raft alteration is associated with redistribution of NKT cells and increased intrahepatic CD8+ T lymphocyte trapping. J Lipid Res 2008; 49:1884-93. [DOI: 10.1194/jlr.m800113-jlr200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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23
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Abstract
Covalent attachment of radiolabeled fatty acids (e.g., [(3)H]myristate or palmitate) is an alternative method for labeling proteins. This unit contains methods for biosynthetic labeling with fatty acids, analysis of the fatty acid linkage with protein, analysis of total protein-bound fatty acid level in cell extracts, and analysis of the identity of the bound fatty acid.
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Affiliation(s)
- C S Jackson
- National Institute For Medical Research, London, United Kingdom
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24
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Sandro S, Alessandro P. Membrane lipid domains and membrane lipid domain preparations: are they the same thing? TRENDS GLYCOSCI GLYC 2008. [DOI: 10.4052/tigg.20.315] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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25
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Van Komen JS, Mishra S, Byrum J, Chichili GR, Yaciuk JC, Farris AD, Rodgers W. Early and Dynamic Polarization of T Cell Membrane Rafts and Constituents Prior to TCR Stop Signals. THE JOURNAL OF IMMUNOLOGY 2007; 179:6845-55. [DOI: 10.4049/jimmunol.179.10.6845] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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26
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Jury EC, Flores-Borja F, Kabouridis PS. Lipid rafts in T cell signalling and disease. Semin Cell Dev Biol 2007; 18:608-15. [PMID: 17890113 PMCID: PMC2596300 DOI: 10.1016/j.semcdb.2007.08.002] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 07/24/2007] [Accepted: 08/16/2007] [Indexed: 11/18/2022]
Abstract
Lipid rafts is a blanket term used to describe distinct areas in the plasma membrane rich in certain lipids and proteins and which are thought to perform diverse functions. A large number of studies report on lipid rafts having a key role in receptor signalling and activation of lymphocytes. In T cells, lipid raft involvement was demonstrated in the early steps during T cell receptor (TCR) stimulation. Interestingly, recent evidence has shown that signalling in these domains differs in T cells isolated from patients with autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Here, we discuss these findings and explore the potential of lipid rafts as targets for the development of a new class of agents to downmodulate immune responses and for the treatment of autoimmune diseases.
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Affiliation(s)
- Elizabeth C. Jury
- Centre for Rheumatology, Royal Free and University College Medical School, University College London, London W1P 4JF, United Kingdom
- Corresponding author at: Bone and Joint Research Unit, Queen Mary's School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, United Kingdom. Tel.: +44 207 679 9634; fax: +44 207 679 9143.
| | - Fabian Flores-Borja
- Centre for Rheumatology, Royal Free and University College Medical School, University College London, London W1P 4JF, United Kingdom
| | - Panagiotis S. Kabouridis
- Bone and Joint Research Unit, Queen Mary's School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, United Kingdom
- Corresponding author. Tel.: +44 207882 5664; fax: +44 207882 6121.
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27
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Aires V, Hichami A, Boulay G, Khan NA. Activation of TRPC6 calcium channels by diacylglycerol (DAG)-containing arachidonic acid: A comparative study with DAG-containing docosahexaenoic acid. Biochimie 2007; 89:926-37. [PMID: 17532549 DOI: 10.1016/j.biochi.2006.10.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Accepted: 10/27/2006] [Indexed: 11/29/2022]
Abstract
We synthesized a diacylglycerol (DAG)-containing arachidonic acid, i.e., 1-stearoyl-2-arachidonyl-sn-glycerol (SAG), and studied its implication in the modulation of canonical transient receptor potential sub-type 6 (TRPC6) channels in stably-transfected HEK-293 cells. SAG induced the influx of Ca(2+), and also of other bivalent cations like Ba(2+) and Sr(2+), in these cells. SAG-evoked Ca(2+) influx was not due to its metabolites as inhibitors of DAG-lipase (RHC80267) and DAG-kinase (R50922) failed to inhibit the response of the same. To emphasise that SAG exerts its action via its DAG configuration, but not due to the presence of stearic acid at sn-1 position, we synthesized 1-palmitoyl-2-arachidonyl-sn-glycerol (PAG). PAG-induced increases in [Ca(2+)](i) were not significantly different from those induced by SAG. For the comparative studies, we also synthesized the DAG-containing docosahexaenoic acid, i.e., 1-stearoyl-2-docosahexaenoyl-sn-glycerol (SDG). We observed that SDG and 1,2-dioctanoyl-sn-glycerol (DOG), a DAG analogue, also evoked increases in [Ca(2+)](i), which were lesser than those evoked by SAG. However, activation of TRPC6 channels by all the DAG molecular species (SAG, DOG and SDG) required Src kinases as the tyrosine kinase inhibitors, PP2 and SU6656, significantly attenuated the increases in [Ca(2+)](i) evoked by these agents. Moreover, disruption of lipid rafts with methyl-beta-cyclodextrin completely abolished SAG-, DOG- and SDG-induced increases in [Ca(2+)](i). The present study shows that SAG as well as SDG and DOG stimulate Ca(2+) influx through the activation of TRPC6 calcium channels which are regulated by Src kinases and intact lipid raft domains.
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Affiliation(s)
- Virginie Aires
- Département de Physiologie, UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la Vie, 6 Boulevard Gabriel, 2100 Dijon, France
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28
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Camacho-Leal P, Zhai AB, Stanners CP. A co-clustering model involving alpha5beta1 integrin for the biological effects of GPI-anchored human carcinoembryonic antigen (CEA). J Cell Physiol 2007; 211:791-802. [PMID: 17286276 DOI: 10.1002/jcp.20989] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
CEA functions as an intercellular adhesion molecule and is up-regulated in a wide variety of human cancers, including colon, breast and lung. Its over-expression inhibits cellular differentiation, blocks cell polarization, distorts tissue architecture, and inhibits anoikis of many different cell types. Here we report results concerning the molecular mechanism involved in these biological effects, where relatively rapid molecular changes not requiring alterations in gene expression were emphasized. Confocal microscopy experiments showed that antibody-mediated clustering of a deletion mutant of CEA (DeltaNCEA), normally incapable of self binding and clustering, led to the co-localization of integrin alpha5beta1 with patches of DeltaNCEA on the cell surface. Activation of alpha5, as defined by an anti-alpha5 mAb-sensitive increase in cell adhesion to immobilized fibronectin, and an increased binding of soluble fibronectin to cells, was also observed. This was accompanied by the recruitment of integrin-linked kinase (ILK), protein kinase B (PKB/Akt), and the mitogen-activated protein kinase (MAPK) to membrane microdomains and the phosphorylation of Akt and MAPK. Inhibition of PI3-K and ILK, but not MAPK, prevented the alpha5beta1 integrin activation. Conversely, anti-alpha5 antibody inhibited the PI3-K-mediated activation of Akt, implying the involvement of outside-in and inside-out signaling in integrin activation. Therefore we propose that CEA-mediated signaling involves clustering of CEA and co-clustering and activation of the alpha5beta1 and associated specific signaling elements on the internal surfaces of membrane microdomains. These changes may represent a molecular mechanism for the biological effects of CEA.
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Affiliation(s)
- Pilar Camacho-Leal
- Department of Biochemistry and McGill Cancer Centre, McGill University, Quebec, Canada
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29
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Campbell EM, Perez O, Melar M, Hope TJ. Labeling HIV-1 virions with two fluorescent proteins allows identification of virions that have productively entered the target cell. Virology 2007; 360:286-93. [PMID: 17123568 PMCID: PMC1885464 DOI: 10.1016/j.virol.2006.10.025] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Revised: 07/31/2006] [Accepted: 10/04/2006] [Indexed: 11/23/2022]
Abstract
GFP-Vpr labeled HIV-1 virions have provided a method to visually examine the interactions between the virus and target cell during infection. However, existing methods to discriminate between virions that have been non-specifically endocytosed from those that have productively entered the host cell cytoplasm have remained problematic. Therefore, we examined the ability of a series of membrane-targeted fluorescent fusion protein constructs to be incorporated into virions. We find that a fluorescent protein fusion targeted to the plasma membrane by the addition of the N-terminal 15 amino acid sequence of c-Src (S15) is efficiently packaged into HIV virions. Using fluorescent proteins fused to this sequence, we have generated virions dually labeled with S15-mCherry and GFP-Vpr. Importantly, we can detect the loss of this S15-mCherry membrane signal following fusion. After infection with VSV-g pseudotyped HIV virions, we find a measurable, specific loss of membrane label during infection. This loss of fluorescence is not observed when fusion is prevented using bafilomycin A. This increased ability to discriminate between non-productively endocytosed virions and those actively undergoing steps in the infectious process will facilitate efforts to examine early steps in infection microscopically.
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Affiliation(s)
- Edward M. Campbell
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Omar Perez
- Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, Illinois, 60612, USA
| | - Marta Melar
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Thomas J. Hope
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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30
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Abstract
Fluorescence microscopy of model membranes is a powerful tool for identifying the nature and extent of coexisting phases in biologically relevant lipid mixtures. Planar supported bilayers offer the advantage over spherical model membranes in that both overall composition and lipid asymmetry can be controlled. In addition, the membrane can be easily accessed by perfusion of soluble components. Here, the necessary techniques for reconstituting bilayers of complex composition and phase behavior in planar systems are outlined. Effective methods for the formation of both symmetric and asymmetric bilayers are described. Considerations that must be taken into account in choosing suitable lipid compositions, effective fluorescent lipid dyes, and adequate microscope setups are discussed.
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Affiliation(s)
- Jonathan M Crane
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, USA
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31
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Lommerse PHM, Vastenhoud K, Pirinen NJ, Magee AI, Spaink HP, Schmidt T. Single-molecule diffusion reveals similar mobility for the Lck, H-ras, and K-ras membrane anchors. Biophys J 2006; 91:1090-7. [PMID: 16920696 PMCID: PMC1563745 DOI: 10.1529/biophysj.105.079053] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent evidence on the occurrence of small (5-700 nm diameter) lipid microdomains in the exoplasmic leaflet of the plasma membrane has evoked interest in the possibility that similar domains may also be present in the cytoplasmic leaflet of the plasma membrane. However, current knowledge about these "lipid rafts", in live cells is limited. One way to obtain insight into the occurrence and the size of lipid rafts is the use of single-molecule microscopy, which allows one to study the diffusive motion of individual molecules with high positional and temporal accuracy. Using this technique, we compared the diffusion behavior of the Lck membrane anchor, which has a high affinity for lipid rafts, to the diffusion behavior of the K-Ras membrane anchor, which has negligible affinity for rafts and compared the results with those of the H-Ras membrane anchor. Surprisingly, we found only minor differences in the diffusion behavior of the various lipid anchors, indicating that putative cytoplasmic leaflet lipid rafts would have to be small (<137 nm diameter) and do not affect the mobility of membrane-anchored molecules much on timescales up to 60 ms.
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Affiliation(s)
- Piet H M Lommerse
- Physics of Life Processes, Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
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32
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Kiessling V, Crane JM, Tamm LK. Transbilayer effects of raft-like lipid domains in asymmetric planar bilayers measured by single molecule tracking. Biophys J 2006; 91:3313-26. [PMID: 16905614 PMCID: PMC1614489 DOI: 10.1529/biophysj.106.091421] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Cell membranes have complex lipid compositions, including an asymmetric distribution of phospholipids between the opposing leaflets of the bilayer. Although it has been demonstrated that the lipid composition of the outer leaflet of the plasma membrane is sufficient for the formation of raft-like liquid-ordered (l(o)) phase domains, the influence that such domains may have on the lipids and proteins of the inner leaflet remains unknown. We used tethered polymer supports and a combined Langmuir-Blodgett/vesicle fusion (LB/VF) technique to build asymmetric planar bilayers that mimic plasma membrane asymmetry in many ways. We show that directly supported LB monolayers containing cholesterol-rich l(o) phases are inherently unstable when exposed to water or vesicle suspensions. However, tethering the LB monolayer to the solid support with the lipid-anchored polymer 1,2-dimyristoyl phophatidylethanolamine-N-[poly(ethylene glycol)-triethoxysilane] significantly improves stability and allows for the formation of complex planar-supported bilayers that retain >90% asymmetry for 1-2 h. We developed a single molecule tracking (SPT) system for the study of lipid diffusion in asymmetric bilayers with coexisting liquid phases. SPT allowed us to study in detail the diffusion of individual lipids inside, outside, or directly opposed to l(o) phase domains. We show here that l(o) phase domains in one monolayer of an asymmetric bilayer do not induce the formation of domains in the opposite leaflet when this leaflet is composed of palmitoyl-oleoyl phosphatidylcholine and cholesterol but do induce domains when this leaflet is composed of porcine brain phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and cholesterol. The diffusion of lipids is similar in l(o) and liquid-disordered phase domains and is not affected by transbilayer coupling, indicating that lateral and transverse lipid interactions that give rise to the domain structure are weak in the biological lipid mixtures that were employed in this work.
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Affiliation(s)
- Volker Kiessling
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, 22908-0736, USA
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33
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Abstract
The molecular events and the protein components that are involved in signalling by the T cell receptor (TCR) for antigen have been extensively studied. Activation of signalling cascades following TCR stimulation depends on the phosphorylation of the receptor by the tyrosine kinase Lck, which localizes to the cytoplasmic face of the plasma membrane by virtue of its post-translational modification. However, the precise order of events during TCR phosphorylation at the plasma membrane, remains to be defined. A current theory that describes early signalling events incorporates the function of lipid rafts, microdomains at the plasma membrane with distinct lipid and protein composition. Lipid rafts have been implicated in diverse biological functions in mammalian cells. In T cells, molecules with a key role in TCR signalling, including Lck, localize to these domains. Importantly, mutant versions of these proteins which fail to localise to raft domains were unable to support signalling by the TCR. Biochemical studies using purified detergent-resistant membranes (DRM) and confocal microscopy have suggested that upon stimulation, the TCR and Lck-containing lipid rafts may come into proximity allowing phosphorylation of the receptor. Further, there are data suggesting that phosphorylation of the TCR could depend on a transient increase in Lck activity that takes place within lipid rafts to initiate signalling. Current results and a model of how lipid rafts may regulate TCR signalling are discussed.
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Affiliation(s)
- Panagiotis S Kabouridis
- Bone & Joint Research Unit, William Harvey Research Institute, Queen Mary's School of Medicine & Dentistry, University of London, UK.
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34
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Pozo D, Valés-Gómez M, Mavaddat N, Williamson SC, Chisholm SE, Reyburn H. CD161 (Human NKR-P1A) Signaling in NK Cells Involves the Activation of Acid Sphingomyelinase. THE JOURNAL OF IMMUNOLOGY 2006; 176:2397-406. [PMID: 16455998 DOI: 10.4049/jimmunol.176.4.2397] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
NK and NKT cells play a major role in both innate immunity and in influencing the development of adaptive immune responses. CD161 (human NKR-P1A), a protein encoded in the NK gene complex, is a major phenotypic marker of both these cell types and is thought to be involved in the regulation of NK and NKT cell function. However, the mechanisms of action and signaling pathways of CD161 are poorly understood. To identify molecules able to interact with the cytoplasmic tail of human CD161 (NKR-P1A), we have conducted a yeast two-hybrid screen and identified acid sphingomyelinase as a novel intracellular signaling pathway linked to CD161. mAb-mediated cross-linking of CD161, in both transfectants and primary human NK cells, triggers the activation of acid, but not neutral sphingomyelinase. The sphingomyelinases represent the catabolic pathway for N-acyl-sphingosine (ceramide) generation, an emerging second messenger with key roles in the induction of apoptosis, proliferation, and differentiation. These data therefore define a novel signal transduction pathway for the CD161 (NKR-P1A) receptor and provide fresh insights into NK and NKT cell biology.
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Affiliation(s)
- David Pozo
- Immunology Division, Department of Pathology, University of Cambridge, UK
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35
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Leser GP, Lamb RA. Influenza virus assembly and budding in raft-derived microdomains: a quantitative analysis of the surface distribution of HA, NA and M2 proteins. Virology 2005; 342:215-27. [PMID: 16249012 DOI: 10.1016/j.virol.2005.09.049] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/02/2005] [Accepted: 09/20/2005] [Indexed: 11/24/2022]
Abstract
Influenza virus hemagglutinin (HA) and neuraminidase (NA) are known to associate with lipid rafts, membrane microdomains comprised of densely packed cholesterol and sphingolipids. These specialized membrane regions are believed to be involved in the budding of many enveloped viruses including influenza virus. Quantitative analysis of HA distribution on the surface of virus-infected cells by immunogold staining shows an organization into clusters that grow in size as the expression level of HA increases with time post-infection (p.i.) ( approximately 325-500 nm at 4 h p.i. and approximately 425-600 nm at 6 h p.i.). These HA-containing clusters are likely derived from lipid rafts as they contain a high density of the raft marker ganglioside GM1 and are dependent upon the presence of cholesterol. The clustering of HA is an intrinsic property of the HA protein and occurs in the absence of expression of other viral proteins. NA is also found sequestered within the same microdomains as HA, whereas the M2 ion channel protein does not concentrate within the raft-like microdomains. Quantification of the distribution of surface expressed HA by examining serial sections of virus-infected cells suggests that the HA-containing microdomains give rise to regions of influenza assembly and budding.
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Affiliation(s)
- George P Leser
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, 2205 Tech Drive, Evanston, IL 60208-3500, USA
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36
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Barnett-Norris J, Lynch D, Reggio PH. Lipids, lipid rafts and caveolae: Their importance for GPCR signaling and their centrality to the endocannabinoid system. Life Sci 2005; 77:1625-39. [PMID: 15993425 DOI: 10.1016/j.lfs.2005.05.040] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Scientific views of cell membrane organization are presently changing. Rather than serving only as the medium through which membrane proteins diffuse, lipid bilayers have now been shown to form compartmentalized domains with different biophysical properties (rafts/caveolae). For membrane proteins such as the G protein coupled receptors (GPCRs), a raft domain provides a platform for the assembly of signaling complexes and prevents cross-talk between pathways. Lipid composition also has a strong influence on the conformational activity of GPCRs. For certain GPCRs, such as the cannabinoid receptors, the lipid bilayer has additional significance. Endocannabinoids such as anandamide (AEA) are created in a lipid bilayer from lipid and act at the membrane embedded CB1 receptor. Endocannabinoids exiting the CB1 receptor are transported either by a carrier-mediated or a simple diffusion process to the membrane of the postsynaptic cell. Following cellular uptake, perhaps via caveolae/lipid raft-related endocytosis, AEA is rapidly metabolized by a membrane-associated enzyme, fatty acid amide hydrolase (FAAH) located in the endoplasmic reticulum. The entry point for AEA into FAAH appears to be from the lipid bilayer. This review explores the importance of lipid composition and lipid rafts to GPCR signaling and then focuses on the intimate relationship that exists between the lipid environment and the endocannabinoid system.
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Affiliation(s)
- Judy Barnett-Norris
- Department of Chemistry and Biochemistry, University of North Carolina Greensboro, P.O. Box 26170, 435 New Science Building, Greensboro, NC 27402-6170, USA
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37
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Fawcett VCJ, Lorenz U. Localization of Src homology 2 domain-containing phosphatase 1 (SHP-1) to lipid rafts in T lymphocytes: functional implications and a role for the SHP-1 carboxyl terminus. THE JOURNAL OF IMMUNOLOGY 2005; 174:2849-59. [PMID: 15728495 DOI: 10.4049/jimmunol.174.5.2849] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The protein tyrosine phosphatase Src homology 2 domain-containing phosphatase 1 (SHP-1) has previously been shown to be a negative regulator of signaling mediated via the TCR. A growing body of evidence indicates that the regulated localization of proteins within certain membrane subdomains, referred to as lipid rafts, is important for the successful transduction of signaling events downstream of the TCR. However, considerably less is known about the localization of negative regulators during these lipid raft-dependent signaling events. In this study we have investigated the subcellular localization of SHP-1 and its role in regulation of TCR-mediated signaling. Our studies demonstrate that in a murine T cell hybridoma as well as in primary murine thymocytes, a fraction of SHP-1 localizes to the lipid rafts, both basally and after TCR stimulation. Interestingly, although SHP-1 localized in the nonraft fractions is tyrosine phosphorylated, the SHP-1 isolated from the lipid rafts lacks the TCR-induced tyrosine phosphorylation, suggesting physical and/or functional differences between these two subpopulations. We identify a requirement for the C-terminal residues of SHP-1 in optimal localization to the lipid rafts. Although expression of SHP-1 that localizes to lipid rafts potently inhibits TCR-mediated early signaling events and IL-2 production, the expression of lipid raft-excluded SHP-1 mutants fails to elicit any of the inhibitory effects. Taken together these studies reveal a key role for lipid raft localization of SHP-1 in mediating the inhibitory effects on T cell signaling events.
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MESH Headings
- Animals
- Antibodies, Monoclonal/metabolism
- Binding Sites, Antibody
- Cell Line
- Interleukin-2/antagonists & inhibitors
- Interleukin-2/biosynthesis
- Intracellular Signaling Peptides and Proteins
- Membrane Microdomains/enzymology
- Membrane Microdomains/genetics
- Membrane Microdomains/metabolism
- Mice
- Mice, Inbred C3H
- Mutagenesis, Site-Directed
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/metabolism
- Peptide Fragments/physiology
- Phosphorylation
- Protein Phosphatase 1
- Protein Structure, Tertiary
- Protein Tyrosine Phosphatase, Non-Receptor Type 6
- Protein Tyrosine Phosphatases/biosynthesis
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/metabolism
- Protein Tyrosine Phosphatases/physiology
- Receptor-CD3 Complex, Antigen, T-Cell/antagonists & inhibitors
- Receptor-CD3 Complex, Antigen, T-Cell/physiology
- Sequence Deletion
- Signal Transduction/immunology
- Subcellular Fractions/metabolism
- T-Lymphocytes/cytology
- T-Lymphocytes/enzymology
- Tyrosine/metabolism
- src Homology Domains/genetics
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Affiliation(s)
- Vicki C J Fawcett
- Department of Microbiology and The Beirne Carter Center for Immunology Research, University of Virginia, Charlottesville, VA 22908, USA
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38
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Abstract
During invasion by Toxoplasma gondii, host cell transmembrane proteins are excluded from the forming parasitophorous vacuole membrane (PVM) by the tight apposition of host and parasite cellular membranes. Previous studies suggested that the basis for the selective partitioning of membrane constituents may be a preference for membrane microdomains, and this hypothesis was herein tested. The partitioning of a diverse group of molecular reporters for raft and nonraft membrane subdomains was monitored during parasite invasion by time-lapse video or confocal microscopy. Unexpectedly, both raft and nonraft lipid probes, as well as both raft and nonraft cytosolic leaflet proteins, flowed unhindered past the host-parasite junction into the PVM. Moreover, neither a raft-associated type 1 transmembrane protein nor its raft-dissociated counterpart accessed the PVM, while a multispanning membrane raft protein readily did so. Considered together with previous data, these studies demonstrate that selective partitioning at the host-parasite interface is a highly complex process, in which raft association favors, but is neither necessary nor sufficient for, inclusion into the T. gondii PVM.
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Affiliation(s)
- Audra J Charron
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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39
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Horejsí V. Lipid rafts and their roles in T-cell activation. Microbes Infect 2005; 7:310-6. [PMID: 15715974 DOI: 10.1016/j.micinf.2004.12.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Accepted: 09/01/2004] [Indexed: 10/25/2022]
Abstract
Lipid rafts are defined as detergent-resistant membrane microdomains of specific lipid and protein composition. They are involved in many aspects of cell biology, including T-cell activation and immunoreceptor signaling. This review discusses current controversies around lipid rafts and summarizes recent developments in the area.
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Affiliation(s)
- Václav Horejsí
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
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40
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Razzaq TM, Ozegbe P, Jury EC, Sembi P, Blackwell NM, Kabouridis PS. Regulation of T-cell receptor signalling by membrane microdomains. Immunology 2004; 113:413-26. [PMID: 15554919 PMCID: PMC1782593 DOI: 10.1111/j.1365-2567.2004.01998.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Revised: 09/09/2004] [Accepted: 09/15/2004] [Indexed: 01/04/2023] Open
Abstract
There is now considerable evidence suggesting that the plasma membrane of mammalian cells is compartmentalized by functional lipid raft microdomains. These structures are assemblies of specialized lipids and proteins and have been implicated in diverse biological functions. Analysis of their protein content using proteomics and other methods revealed enrichment of signalling proteins, suggesting a role for these domains in intracellular signalling. In T lymphocytes, structure/function experiments and complementary pharmacological studies have shown that raft microdomains control the localization and function of proteins which are components of signalling pathways regulated by the T-cell antigen receptor (TCR). Based on these studies, a model for TCR phosphorylation in lipid rafts is presented. However, despite substantial progress in the field, critical questions remain. For example, it is unclear if membrane rafts represent a homogeneous population and if their structure is modified upon TCR stimulation. In the future, proteomics and the parallel development of complementary analytical methods will undoubtedly contribute in further delineating the role of lipid rafts in signal transduction mechanisms.
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Affiliation(s)
- Tahir M Razzaq
- Bone and Joint Research Unit, William Harvey Research Institute, Queen Mary's School of Medicine and Dentistry, Queen Mary's College, London
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41
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Krishnan S, Nambiar MP, Warke VG, Fisher CU, Mitchell J, Delaney N, Tsokos GC. Alterations in lipid raft composition and dynamics contribute to abnormal T cell responses in systemic lupus erythematosus. THE JOURNAL OF IMMUNOLOGY 2004; 172:7821-31. [PMID: 15187166 DOI: 10.4049/jimmunol.172.12.7821] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In response to appropriate stimulation, T lymphocytes from systemic lupus erythematosus (SLE) patients exhibit increased and faster intracellular tyrosine phosphorylation and free calcium responses. We have explored whether the composition and dynamics of lipid rafts are responsible for the abnormal T cell responses in SLE. SLE T cells generate and possess higher amounts of ganglioside-containing lipid rafts and, unlike normal T cells, SLE T cell lipid rafts include FcRgamma and activated Syk kinase. IgM anti-CD3 Ab-mediated capping of TCR complexes occurs more rapidly in SLE T cells and concomitant with dramatic acceleration of actin polymerization kinetics. The significance of these findings is evident from the observation that cross-linking of lipid rafts evokes earlier and higher calcium responses in SLE T cells. Thus, we propose that alterations in the lipid raft signaling machinery represent an important mechanism that is responsible for the heightened and accelerated T cell responses in SLE.
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Affiliation(s)
- Sandeep Krishnan
- Department of Cellular Injury, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
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42
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Watson ARO, Lee WT. Differences in signaling molecule organization between naive and memory CD4+ T lymphocytes. THE JOURNAL OF IMMUNOLOGY 2004; 173:33-41. [PMID: 15210756 DOI: 10.4049/jimmunol.173.1.33] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The immunological synapse is a highly organized complex formed at the junction between Ag-specific T cells and APCs as a prelude to cell activation. Although its exact role in modulating T cell signaling is unknown, it is commonly believed that the immunological synapse is the site of cross-talk between the T cell and APC (or target). We have examined the synapses formed by naive and memory CD4 cells during Ag-specific cognate interactions with APCs. We show that the mature immunological synapse forms more quickly during memory T cell activation. We further show that the composition of the synapse found in naive or memory cell conjugates with APCs is distinct with the tyrosine phosphatase, CD45, being a more integral component of the mature synapses formed by memory cells. Finally, we show that signaling molecules, including CD45, are preassociated in discrete, lipid-raft microdomains in resting memory cells but not in naive cells. Thus, enhanced memory cell responses may be due to intrinsic properties of signaling molecule organization.
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Affiliation(s)
- Andrew R O Watson
- Department of Biomedical Sciences, School of Public Health, State University of New York, Albany, NY 12201-0509, USA
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43
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Lommerse PHM, Spaink HP, Schmidt T. In vivo plasma membrane organization: results of biophysical approaches. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1664:119-31. [PMID: 15328044 DOI: 10.1016/j.bbamem.2004.05.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 04/29/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
In the last two decades, various biophysical techniques have been used to investigate the organization of the plasma membrane in live cells. This review describes some of the most important experimental findings and summarizes the characteristics and limitations of a few frequently used biophysical techniques. In addition, the current knowledge about three membrane organizational elements: the membrane-associated cytoskeleton, caveolae and lipid microdomains, is described in detail. Unresolved issues, experimental contradictions and future directions to integrate the variety of experimental data into a revised model of the plasma membrane of eukaryotic cells are discussed in the last section.
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Affiliation(s)
- P H M Lommerse
- Department of Biophysics, Leiden University, Niels Bohrweg 2, 2333 CA, The Netherlands
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44
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Zehmer JK, Hazel JR. Membrane order conservation in raft and non-raft regions of hepatocyte plasma membranes from thermally acclimated rainbow trout. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2004; 1664:108-16. [PMID: 15238264 DOI: 10.1016/j.bbamem.2004.04.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 04/12/2004] [Accepted: 04/30/2004] [Indexed: 11/19/2022]
Abstract
Homeoviscous adaptation (HVA), the thermal conservation of membrane fluidity/order at different body temperatures, has been observed to varying degrees in different membranes. However, HVA has not been studied in raft and non-raft regions of the plasma membrane (PM) separately. Rafts are ordered PM microdomains implicated in signal transduction, membrane traffic and cholesterol homeostasis. Using infrared spectroscopy, we measured order in raft-enriched PM (raft) and raft-depleted PM (RDPM) isolated from hepatocytes of rainbow trout (Oncorhynchus mykiss) acclimated to 5 and 20 degrees C. We found approximately 130% and 90% order compensation in raft and RDPM, respectively, suggesting their independent regulation. Raft was more ordered than RDPM in the warm-acclimated trout, a difference fully explained by a 58% enrichment of cholesterol, compared to RPDM. Unexpectedly, raft and RDPM from cold-acclimated trout did not differ in cholesterol content or order. Freezing the membrane samples during preparation had no effect on order. Treatment with cyclodextrin depleted cholesterol by 36%, 56%, and 55%, producing significant decreases in order in raft and RDPM from warm-acclimated trout and RDPM from cold-acclimated trout, respectively. However, a 69% depletion of cholesterol from raft from cold-acclimated trout had no significant effect on order. This result, and the lack of a difference in order between raft and RDPM, suggests that raft and non-raft PM in cold-acclimated trout are not spatially segregated by phase separation due to cholesterol.
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Affiliation(s)
- John K Zehmer
- School of Life Sciences, Arizona State University,Tempe, AZ 85287, USA.
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45
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Gordy C, Mishra S, Rodgers W. Visualization of antigen presentation by actin-mediated targeting of glycolipid-enriched membrane domains to the immune synapse of B cell APCs. THE JOURNAL OF IMMUNOLOGY 2004; 172:2030-8. [PMID: 14764667 DOI: 10.4049/jimmunol.172.4.2030] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glycolipid-enriched membrane (GEM) domains, or lipid rafts, function in signaling in immune cells, but their properties during Ag presentation are less clear. To address this question, GEM domains were studied using fluorescence cell imaging of mouse CH27 B cells presenting Ag to D10 T cells. Our experiments showed that APCs were enriched with GEM domains in the immune synapse, and this occurred in an actin-dependent manner. This enrichment was specific to GEM domains, because a marker for non-GEM regions of the membrane was excluded from the immune synapse. Furthermore, fluorescence photobleaching experiments showed that protein in the immune synapse was dynamic and rapidly exchanged with that in other compartments of CH27 cells. To identify the signals for targeting GEM domains to the immune synapse in APCs, capping of the domains was measured in cells after cross-linking surface molecules. This showed that co-cross-linking CD48 with MHC class II was required for efficient capping and intracellular signaling. Capping of GEM domains by co-cross-linking CD48 and MHC class II occurred with co-capping of filamentous actin, and both domain capping and T cell-CH27 cell conjugation were inhibited by pretreating CH27 cells with latrunculin B. Furthermore, disruption of the actin cytoskeleton of the CH27 cells also inhibited formation of a mature immune synapse in those T cells that did conjugate to APCs. Thus, Ag presentation and efficient T cell stimulation occur by an actin-dependent targeting of GEM domains in the APC to the site of T cell engagement.
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Affiliation(s)
- Claire Gordy
- Molecular Immunogenetics Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
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46
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Cherukuri A, Carter RH, Brooks S, Bornmann W, Finn R, Dowd CS, Pierce SK. B cell signaling is regulated by induced palmitoylation of CD81. J Biol Chem 2004; 279:31973-82. [PMID: 15161911 DOI: 10.1074/jbc.m404410200] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signaling through the B cell antigen receptor (BCR) is amplified and prolonged by coligation of the BCR to the CD19/CD21/CD81 coreceptor complex. Coligation is induced during immune responses by the simultaneous binding of complement-tagged antigens to the complement receptor, CD21, and to the BCR. Enhanced signaling is due in part to the ability of the CD19/CD21/CD81 complex to stabilize the BCR in sphingolipid- and cholesterol-rich membrane microdomains termed lipid rafts. The tetraspanin CD81 is essential for the raft-stabilizing function of the coreceptor. Here we show that coligation of the BCR and the CD19/CD21/CD81 complex leads to selective, rapid, and reversible palmitoylation of CD81 and that palmitoylation is necessary for the raft stabilizing function of the CD19/CD21/CD81 complex. Inducible palmitoylation may represent a novel mechanism by which tetraspanins function to facilitate lipid raft-dependent receptor signaling.
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Affiliation(s)
- Anu Cherukuri
- Laboratory of Immunogenetics, NIAID, National Institutes of Health, Rockville, Maryland 20852, USA
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47
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Wurm S, Paar C, Sonnleitner A, Sonnleitner M, Höglinger O, Romanin C, Wechselberger C. Co-localization of CD3 and prion protein in Jurkat lymphocytes after hypothermal stimulation. FEBS Lett 2004; 566:121-5. [PMID: 15147880 DOI: 10.1016/j.febslet.2004.03.114] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2004] [Revised: 03/31/2004] [Accepted: 03/31/2004] [Indexed: 11/16/2022]
Abstract
While long-term effects of temperature treatment in respect of, e.g., gene-expression and cellular function have already been studied in some detail, nothing is known on the physiological responses of lymphocytes during short-term hypothermal shifts. In this report, we characterized the effects of such a stimulation using the human lymphocyte cell line Jurkat E6.1 and present evidence that warming from 4 to 37 degrees C for only 2 min is sufficient to cause co-localization of CD3, prion protein and the lipid-raft ganglioside GM1 paralleling lymphocyte activation as observed by Ca(2+) mobilization and mitogen-activated protein kinase-phosphorylation.
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Affiliation(s)
- Susanne Wurm
- Upper Austrian Research GmbH, Center for Biomedical Nanotechnology, Scharitzerstr. 6-8, 4020 Linz, Austria
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48
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Abstract
Regulated secretion and exocytosis require the selective packaging of regulated secretory proteins in secretory storage organelles and the controlled docking and fusion of these organelles with the plasma membrane. Secretory granule biogenesis involves sorting of secretory proteins and membrane components both at the level of the trans-Golgi network and the immature secretory granule. Sorting is thought to be mediated by selective protein aggregation and the interaction of these proteins with specific membrane domains. There is now considerable interest in the understanding of the complex lipid-protein and protein-protein interactions at the trans-Golgi network and the granule membrane. A role for lipid microdomains and associated sorting receptors in membrane targeting and granule formation is vividly discussed for (neuro)endocrine cells. In exocrine cells, however, little has been known of granule membrane composition and membrane protein function. With the cloning and characterization of granule membrane proteins and their interactions at the inner leaflet of zymogen granules of pancreatic acinar cells, it is now possible to elucidate their function in membrane targeting and sorting of zymogens at the molecular level.
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Affiliation(s)
- Michael Schrader
- Department of Cell Biology and Cell Pathology, University of Marburg, Robert Koch Str 6, 35037 Marburg, Germany
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49
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Nagafuku M, Kabayama K, Oka D, Kato A, Tani-ichi S, Shimada Y, Ohno-Iwashita Y, Yamasaki S, Saito T, Iwabuchi K, Hamaoka T, Inokuchi JI, Kosugi A. Reduction of Glycosphingolipid Levels in Lipid Rafts Affects the Expression State and Function of Glycosylphosphatidylinositol-anchored Proteins but Does Not Impair Signal Transduction via the T Cell Receptor. J Biol Chem 2003; 278:51920-7. [PMID: 14506277 DOI: 10.1074/jbc.m307674200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Lipid rafts are highly enriched in cholesterol and sphingolipids. In contrast to many reports that verify the importance of cholesterol among raft lipid components, studies that address the role of sphingolipids in raft organization and function are scarce. Here, we investigate the role of glycosphingolipids (GSLs) in raft structure and raft-mediated signal transduction in T lymphocytes by the usage of a specific GSL synthesis inhibitor, d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP). Surface GM1 expression and the expression of GSLs in rafts were profoundly reduced by D-PDMP treatment, whereas the expression of other lipid and protein constituents, such as cholesterol, sphingomyelin, Lck, and linker for activation of T cells, was not affected. T cell receptor-mediated signal transduction induced by antigen stimulation or by antibody cross-linking was normal in D-PDMP-treated T cells. In contrast, the signal through glycosylphosphatidylinositol (GPI)-anchored proteins was clearly augmented by D-PDMP treatment. Moreover, GPI-anchored proteins became more susceptible to phosphatidylinositol-specific phospholipase C cleavage in D-PDMP-treated cells, demonstrating that GSL depletion from rafts primarily influences the expression state and function of GPI-anchored proteins. Finally, by comparing the effect of D-PDMP with that of methyl-beta-cyclodextrin, we identified that compared with cholesterol depletion, GSL depletion has the opposite effect on the phosphatidylinositol-specific phospholipase C sensitivity and signaling ability of GPI-anchored proteins. These results indicate a specific role of GSLs in T cell membrane rafts that is dispensable for T cell receptor signaling but is important for the signal via GPI-anchored proteins.
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Affiliation(s)
- Masakazu Nagafuku
- Department of Immunobiology, Medical Technology and Science, Osaka University Graduate School of Medicine, Suita, Japan
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50
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Dykstra M, Cherukuri A, Sohn HW, Tzeng SJ, Pierce SK. Location is everything: lipid rafts and immune cell signaling. Annu Rev Immunol 2003; 21:457-81. [PMID: 12615889 DOI: 10.1146/annurev.immunol.21.120601.141021] [Citation(s) in RCA: 370] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The cells of both the adaptive and innate immune systems express a dizzying array of receptors that transduce and integrate an enormous amount of information about the environment that allows the cells to mount effective immune responses. Over the past several years, significant advances have been made in elucidating the molecular details of signal cascades initiated by the engagement of immune cell receptors by their ligands. Recent evidence indicates that immune receptors and components of their signaling cascades are spatially organized and that this spatial organization plays a central role in the initiation and regulation of signaling. A key organizing element for signaling receptors appears to be cholesterol- and sphingolipid-rich plasma membrane microdomains termed lipid rafts. Research into the molecular basis of the spatial segregation and organization of signaling receptors provided by rafts is adding fundamentally to our understanding of the initiation and prolongation of signals in the immune system.
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Affiliation(s)
- Michelle Dykstra
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland 20852, USA.
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