51
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Heneberg P, Dráberová L, Bambousková M, Pompach P, Dráber P. Down-regulation of protein-tyrosine phosphatases activates an immune receptor in the absence of its translocation into lipid rafts. J Biol Chem 2010; 285:12787-802. [PMID: 20157115 DOI: 10.1074/jbc.m109.052555] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The earliest known biochemical step that occurs after ligand binding to the multichain immune recognition receptor is tyrosine phosphorylation of the receptor subunits. In mast cells and basophils activated by multivalent antigen-IgE complexes, this step is mediated by Src family kinase Lyn, which phosphorylates the high affinity IgE receptor (Fc epsilonRI). However, the exact molecular mechanism of this phosphorylation step is incompletely understood. In this study, we tested the hypothesis that changes in activity and/or topography of protein-tyrosine phosphatases (PTPs) could play a major role in the Fc epsilonRI triggering. We found that exposure of rat basophilic leukemia cells or mouse bone marrow-derived mast cells to PTP inhibitors, H(2)O(2) or pervanadate, induced phosphorylation of the Fc epsilonRI subunits, similarly as Fc epsilonRI triggering. Interestingly, and in sharp contrast to antigen-induced activation, neither H(2)O(2) nor pervanadate induced any changes in the association of Fc epsilonRI with detergent-resistant membranes and in the topography of Fc epsilonRI detectable by electron microscopy on isolated plasma membrane sheets. In cells stimulated with pervanadate, H(2)O(2) or antigen, enhanced oxidation of active site cysteine of several PTPs was detected. Unexpectedly, most of oxidized phosphatases bound to the plasma membrane were associated with the actin cytoskeleton. Several PTPs (SHP-1, SHP-2, hematopoietic PTP, and PTP-MEG2) showed changes in their enzymatic activity and/or oxidation state during activation. Based on these and other data, we propose that down-regulation of enzymatic activity of PTPs and/or changes in their accessibility to the substrates play a key role in initial tyrosine phosphorylation of the Fc epsilonRI and other multichain immune receptors.
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Affiliation(s)
- Petr Heneberg
- Laboratory of Signal Transduction, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, CZ-142 20 Prague 4, Czech Republic
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52
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Bäumer W, Wlaź P, Jennings G, Rundfeldt C. The putative lipid raft modulator miltefosine displays immunomodulatory action in T-cell dependent dermal inflammation models. Eur J Pharmacol 2010; 628:226-32. [DOI: 10.1016/j.ejphar.2009.11.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 10/27/2009] [Accepted: 11/10/2009] [Indexed: 10/20/2022]
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53
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Membrane rafting: From apical sorting to phase segregation. FEBS Lett 2009; 584:1685-93. [DOI: 10.1016/j.febslet.2009.12.043] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 12/10/2009] [Indexed: 11/23/2022]
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54
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Silveira e Souza AMM, Trindade ES, Jamur MC, Oliver C. Gangliosides are important for the preservation of the structure and organization of RBL-2H3 mast cells. J Histochem Cytochem 2009; 58:83-93. [PMID: 19786609 DOI: 10.1369/jhc.2009.954776] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Gangliosides are known to be important in many biological processes. However, details concerning the exact function of these glycosphingolipids in cell physiology are poorly understood. In this study, the role of gangliosides present on the surface of rodent mast cells in maintaining cell structure was examined using RBL-2H3 mast cells and two mutant cell lines (E5 and D1) deficient in the gangliosides, GM(1) and the alpha-galactosyl derivatives of the ganglioside GD(1b). The two deficient cell lines were morphologically different from each other as well as from the parental RBL-2H3 cells. Actin filaments in RBL-2H3 and E5 cells were under the plasma membrane following the spindle shape of the cells, whereas in D1 cells, they were concentrated in large membrane ruffles. Microtubules in RBL-2H3 and E5 cells radiated from the centrosome and were organized into long, straight bundles. The bundles in D1 cells were thicker and organized circumferentially under the plasma membrane. The endoplasmic reticulum, the Golgi complex, and the secretory granule matrix were also altered in the mutant cell lines. These results suggest that the mast cell-specific alpha-galactosyl derivatives of ganglioside GD(1b) and GM(1) are important in maintaining normal cell morphology.
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Affiliation(s)
- Adriana Maria Mariano Silveira e Souza
- Department of Cell and Molecular Biology and Pathogenic Bioagents, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, Ribeirão Preto, SP, Brazil
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55
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Abstract
Biological membranes are not structurally passive solvents of amphipathic proteins and lipids. Rather, it appears their constituents have evolved intrinsic characteristics that make homogeneous distribution of components unlikely. As a case in point, the concept of lipid rafts has received considerable attention from biologists and biophysicists since the formalization of the hypothesis more than 10 years ago. Today, it is clear that sphingolipid and cholesterol can self-associate into micron-scaled phases in model membranes and that these lipids are involved in the formation of highly dynamic nanoscale heterogeneity in the plasma membrane of living cells. However, it remains unclear whether these entities are manifestations of the same principle. A powerful means by which the molecular organization of rafts can be assessed is through analysis of their functionalized condition. Raft heterogeneity can be activated to coalesce and laterally reorganize/stabilize bioactivity in cell membranes. Evaluation of this property suggests that functional raft heterogeneity arises through principles of lipid-driven phase segregation coupled to additional chemical specificities, probably involving proteins.
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56
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Grochowy G, Hermiston ML, Kuhny M, Weiss A, Huber M. Requirement for CD45 in fine-tuning mast cell responses mediated by different ligand–receptor systems. Cell Signal 2009; 21:1277-86. [DOI: 10.1016/j.cellsig.2009.03.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 03/03/2009] [Accepted: 03/10/2009] [Indexed: 01/09/2023]
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57
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Han X, Smith NL, Sil D, Holowka DA, McLafferty FW, Baird BA. IgE receptor-mediated alteration of membrane-cytoskeleton interactions revealed by mass spectrometric analysis of detergent-resistant membranes. Biochemistry 2009; 48:6540-50. [PMID: 19496615 DOI: 10.1021/bi900181w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We use electrospray ionization mass spectrometry to quantify >100 phospholipid (PL) components in detergent-resistant membrane (DRM) domains that are related to ordered membrane compartments commonly known as lipid rafts. We previously compared PL compositions of DRMs with plasma membrane vesicles and whole cell lipid extracts from RBL mast cells, and we made the initial observation that antigen stimulation of IgE receptors (FcepsilonRI) causes a significant change in the PL composition of DRMs [Fridriksson, E. K., et al. (1999) Biochemistry 38, 8056-8063]. We now characterize the signaling requirements and time course for this change, which is manifested as an increase in the recovery of polyunsaturated PL in DRM, particularly in phosphatidylinositol species. We find that this change is largely independent of tyrosine phosphorylation, stimulated by engagement of FcepsilonRI, and can be activated by Ca(2+) ionophore in a manner independent of antigen stimulation. Unexpectedly, we found that inhibitors of actin polymerization (cytochalasin D and latrunculin A) cause a similar, but more rapid, change in the PL composition of DRMs in the absence of FcepsilonRI activation, indicating that perturbations in the actin cytoskeleton affect the organization of plasma membrane domains. Consistent with this interpretation, a membrane-permeable stabilizer of F-actin, jasplakinolide, prevents antigen-stimulated changes in DRM PL composition. These results are confirmed by a detailed analysis of multiple experiments, showing that receptor and cytochalasin D-stimulated changes in DRM lipid composition follow first-order kinetics. Analysis in terms of the number of double bonds in the fatty acid chains is valid for total PL of the major headgroups and for headgroups individually. In this manner, we show that, on average, concentrations of saturated or monounsaturated PL decrease in the DRM, whereas concentrations of PL with two or more double bonds (polyunsaturated PL) increase due to cytoskeletal perturbation. We find that these changes are independent of fatty acid chain length. Our mass spectrometric analyses provide a detailed accounting of receptor-activated alterations in the plasma membrane that are regulated by the actin cytoskeleton.
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Affiliation(s)
- Xuemei Han
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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58
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Kalipatnapu S, Chattopadhyay A. Membrane organization of the human serotonin1Areceptor monitored by detergent insolubility using GFP fluorescence. Mol Membr Biol 2009; 22:539-47. [PMID: 16373325 DOI: 10.1080/09687860500421738] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Insolubility in non-ionic detergents such as Triton X-100 at low temperature is a widely used biochemical criterion for characterization of membrane domains. In view of the emerging role of membrane organization in the function of G-protein coupled receptors, we have examined detergent insolubility of the 5-HT(1A) receptor in CHO cells using a novel GFP fluorescence approach developed by us. Using this approach, we have explored the membrane organization of the serotonin(1A) receptor tagged to enhanced yellow fluorescent protein (5-HT(1A)R-EYFP) stably expressed in CHO-K1 cells under conditions of varying detergent concentration, reduced membrane cholesterol and agonist stimulation. Our results show that a small yet significant fraction of the 5-HT(1A) receptor exhibits detergent insolubility, which increases upon depletion of membrane cholesterol. Stimulation of 5-HT(1A)R-EYFP by its endogenous ligand, serotonin, did not cause a significant change in the detergent insolubility of the receptor. Taken together, our results on detergent insolubility of 5-HT(1A)R-EYFP provide new insights into the membrane organization of the 5-HT(1A) receptor and could be relevant in the analysis of membrane organization of other G-protein coupled receptors.
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59
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Molfetta R, Gasparrini F, Peruzzi G, Vian L, Piccoli M, Frati L, Santoni A, Paolini R. Lipid raft-dependent FcepsilonRI ubiquitination regulates receptor endocytosis through the action of ubiquitin binding adaptors. PLoS One 2009; 4:e5604. [PMID: 19440386 PMCID: PMC2680016 DOI: 10.1371/journal.pone.0005604] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 04/22/2009] [Indexed: 11/17/2022] Open
Abstract
The best characterized role for ubiquitination of membrane receptors is to negatively regulate signaling by targeting receptors for lysosomal degradation. The high affinity receptor for IgE (FcεRI) expressed on mast cells and basophils is rapidly ubiquitinated upon antigen stimulation. However, the nature and the role of this covalent modification are still largelly unknown. Here, we show that FcεRI subunits are preferentially ubiquitinated at multiple sites upon stimulation, and provide evidence for a role of ubiquitin as an internalization signal: under conditions of impaired receptor ubiquitination a decrease of receptor entry is observed by FACS analysis and fluorescence microscopy. We also used biochemical approaches combined with fluorescence microscopy, to demonstrate that receptor endocytosis requires the integrity of specific membrane domains, namely lipid rafts. Additionally, by RNA interference we demonstrate the involvement of ubiquitin-binding endocytic adaptors in FcεRI internalization and sorting. Notably, the triple depletion of Eps15, Eps15R and Epsin1 negatively affects the early steps of Ag-induced receptor endocytosis, whereas Hrs depletion retains ubiquitinated receptors into early endosomes and partially prevents their sorting into lysosomes for degradation. Our results are compatible with a scenario in which the accumulation of engaged receptor subunits into lipid rafts is required for receptor ubiquitination, a prerequisite for efficient receptor internalization, sorting and delivery to a lysosomal compartment.
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Affiliation(s)
- Rosa Molfetta
- Department of Experimental Medicine, Institute Pasteur-Fondazione Cenci Bolognetti, Sapienza University, Rome, Italy
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60
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Goldstein B, Coombs D, Faeder JR, Hlavacek WS. Kinetic proofreading model. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 640:82-94. [PMID: 19065786 DOI: 10.1007/978-0-387-09789-3_8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Kinetic proofreading is an intrinsic property of the cell signaling process. It arises as a consequence of the multiple interactions that occur after a ligand triggers a receptor to initiate a ignaling cascade and it ensures that false signals do not propagate to completion. In order for an active signaling complex to form after a ligand binds to a cell surface receptor, a sequence of binding and phosphorylation events must occur that are rapidly reversed if the ligand dissociates from the receptor. This gives rise to a mechanism by which cells can discriminate among ligands that bind to the same receptor but form ligand-receptor complexes with different lifetimes. We review experiments designed to test for kinetic proofreading and models that exhibit kinetic proofreading.
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Affiliation(s)
- Byron Goldstein
- Theoretical Biology and Biophysics Group, T-10 MS K710, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 875435, USA.
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61
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Gonnord P, Delarasse C, Auger R, Benihoud K, Prigent M, Cuif MH, Lamaze C, Kanellopoulos JM. Palmitoylation of the P2X7 receptor, an ATP-gated channel, controls its expression and association with lipid rafts. FASEB J 2008; 23:795-805. [PMID: 18971257 DOI: 10.1096/fj.08-114637] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The P2X7 receptor (P2X7R) is an ATP-gated cationic channel expressed by hematopoietic, epithelial, and neuronal cells. Prolonged ATP exposure leads to the formation of a nonselective pore, which can result in cell death. We show that P2X7R is associated with detergent-resistant membranes (DRMs) in both transfected human embryonic kidney (HEK) cells and primary macrophages independently from ATP binding. The DRM association requires the posttranslational modification of P2X7R by palmitic acid. Treatment of cells with the palmitic acid analog 2-bromopalmitate as well as mutations of cysteine to alanine residues abolished P2X7R palmitoylation. Substitution of the 17 intracellular cysteines of P2X7R revealed that 4 regions of the carboxyl terminus domain are involved in palmitoylation. Palmitoylation-defective P2X7R mutants showed a dramatic decrease in cell surface expression because of their retention in the endoplasmic reticulum and proteolytic degradation. Taken together, our data demonstrate that P2X7R palmitoylation plays a critical role in its association with the lipid microdomains of the plasma membrane and in the regulation of its half-life.
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Affiliation(s)
- P Gonnord
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, CNRS UMR 8619, Université Paris Sud, F-91405 Orsay cedex, France
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62
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Zhang Y, Li X, Becker KA, Gulbins E. Ceramide-enriched membrane domains--structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1788:178-83. [PMID: 18786504 DOI: 10.1016/j.bbamem.2008.07.030] [Citation(s) in RCA: 182] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 07/28/2008] [Accepted: 07/29/2008] [Indexed: 12/28/2022]
Abstract
Membrane lipids seem to be organized and not randomly distributed in the cell membrane. In particular, sphingolipids seem to interact with cholesterol in the outer leaflet of the cell membrane resulting in the formation of distinct membrane domains, i.e. rafts. The generation of ceramide within rafts alters their biophysical properties and results in the formation of large ceramide-enriched membrane platforms. These platforms serve to cluster receptor molecules and to organize intracellular signalling molecules to facilitate signal transduction via a receptor upon stimulation. Thus, ceramide-enriched membrane domains amplify not only receptor-, but also stress-mediated signalling events. Although many receptors cluster, the molecular mechanisms mediating this important and general event in signal transduction need to be identified.
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Affiliation(s)
- Yang Zhang
- Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
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63
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Johnson CM, Chichili GR, Rodgers W. Compartmentalization of phosphatidylinositol 4,5-bisphosphate signaling evidenced using targeted phosphatases. J Biol Chem 2008; 283:29920-8. [PMID: 18723502 DOI: 10.1074/jbc.m805921200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP(2)) is a prevalent phosphoinositide in cell membranes, with important functions in cell signaling and activation. A large fraction of PIP(2) associates with the detergent-resistant membrane "raft" fraction, but the functional significance of this association remains controversial. To measure the properties of raft and nonraft PIP(2) in cell signaling, we targeted the PIP(2)-specific phosphatase Inp54p to either the raft or nonraft membrane fraction using minimal membrane anchors. Interestingly, we observed that targeting Inp54p to the nonraft fraction resulted in an enrichment of raft-associated PIP(2) and striking changes in cell morphology, including a wortmannin-sensitive increase in cell filopodia and cell spreading. In contrast, raft-targeted Inp54p depleted the raft pool of PIP(2) and produced smooth T cells void of membrane ruffling and filopodia. Furthermore, raft-targeted Inp54p inhibited capping in T cells stimulated by cross-linking the T cell receptor, but without affecting the T cell receptor-dependent Ca(2+) flux. Altogether, these results provide evidence of compartmentalization of PIP(2)-dependent signaling in cell membranes such as predicted by the membrane raft model.
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Affiliation(s)
- Corey M Johnson
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104, USA
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64
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Peterfy H, Toth G, Pecht I, Erdei A. C3a-derived peptide binds to the type I Fc R and inhibits proximal-coupling signal processes and cytokine secretion by mast cells. Int Immunol 2008; 20:1239-45. [DOI: 10.1093/intimm/dxn083] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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65
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Davey AM, Krise KM, Sheets ED, Heikal AA. Molecular Perspective of Antigen-mediated Mast Cell Signaling. J Biol Chem 2008; 283:7117-27. [DOI: 10.1074/jbc.m708879200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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66
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Maroney SA, Mast AE. Expression of tissue factor pathway inhibitor by endothelial cells and platelets. Transfus Apher Sci 2008; 38:9-14. [PMID: 18261960 DOI: 10.1016/j.transci.2007.12.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Tissue factor pathway inhibitor (TFPI) is a potent anticoagulant protein that abrogates the activity of the tissue factor-factor VIIa catalytic complex that activates blood coagulation in vivo. The importance of TFPI in the regulation of blood coagulation is emphasized by how its activity is modulated in human disease. Decreased TFPI activity contributes to the development of both arterial and venous thrombosis and has been implicated in the thrombotic events occurring in women using oral contraceptives and in patients with paroxysmal nocturnal hemoglobinuria. Both endothelial cells and platelets produce TFPI. Our laboratory is interested in the mechanisms for expression of TFPI on the surface of these cells to better understand how TFPI prevents intravascular thrombosis. Studies of cultured endothelial cells and human placenta have demonstrated that TFPI associates with the cell surface through a glycosyl phosphatidyinositol (GPI)-anchor in a manner that is not dependent on GAGs or altered by heparin. TFPI is not directly bound to the GPI-anchor; instead it appears to bind tightly to a GPI-anchored protein. This GPI-anchored protein appears to be necessary for proper trafficking of TFPI to the cell surface. An alternatively spliced form of TFPI, TFPIbeta, is a truncated form of TFPI that is directly attached to a GPI-anchor. However, it is not clear that human endothelial cells produce TFPIbeta. Platelets produce TFPI but not TFPIbeta. TFPI is expressed on the platelet surface following dual activation with collagen plus thrombin, but not through a GPI-anchor. Studies using mouse models of TFPI deficiency are currently being conducted in our laboratory to determine if distinct physiological functions of endothelial and platelet TFPI exist in vivo.
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Affiliation(s)
- Susan A Maroney
- Blood Research Institute, Blood Center of Wisconsin, P.O. Box 2178, Milwaukee, WI 53201-2178, USA
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67
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Beekman JM, van der Linden JA, van de Winkel JGJ, Leusen JHW. FcgammaRI (CD64) resides constitutively in lipid rafts. Immunol Lett 2008; 116:149-55. [PMID: 18207250 DOI: 10.1016/j.imlet.2007.12.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Revised: 12/05/2007] [Accepted: 12/06/2007] [Indexed: 01/24/2023]
Abstract
Cellular membranes contain microdomains known as 'lipid rafts' or detergent-insoluble microdomains (DRM), enriched in cholesterol and sphingolipids. DRM can play an important role in many cellular processes, including signal transduction, cytoskeletal organization, and pathogen entry. Many receptors like T cell receptors, B cell receptors and IgE receptors have been shown to reside in DRM. The majority of these receptors depend on multivalent ligand interaction to associate with these microdomains. We, here, study association between the high affinity IgG receptor, FcgammaRI (CD64), and membrane microdomains. FcgammaRI is a 72kDa type I glycoprotein that can mediate phagocytosis of opsonized pathogens, but can also effectively capture small immune complexes, and facilitates antigen presentation. We found FcgammaRI to predominantly reside within detergent-insoluble buoyant membranes, together with FcRgamma-chain, but independent of cross-linking ligand. With the use of confocal imaging, FcgammaRI was found to co-patch with GM1, a microdomain-enriched glycolipid. Depletion of cellular cholesterol, furthermore, modulated FcgammaRI-ligand interactions. These data indicated FcgammaRI to reside within lipid rafts without prior triggering of the receptor.
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Affiliation(s)
- Jeffrey M Beekman
- Immunotherapy Laboratory, Department of Immunology, University Medical Center Utrecht, Utrecht, The Netherlands
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68
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Abstract
The biological membrane is a complicated matrix wherein different lipid environments are thought to exist. The more ordered or raft environment has been perceived biochemically accessible via its relative resistance to detergent. This paper outlines the protocols developed in our laboratory for the analysis of such detergent-resistant membranes (DRMs). We stress the fact that DRMs are artifactual in nature and should not be equivocated to lipid rafts, their usefulness being limited to assigning raft-association potential most convincingly when changes in DRM composition are induced by biochemically/physiologically relevant events. These protocols are completed in 1-2 d.
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Affiliation(s)
- Daniel Lingwood
- Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
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69
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Sengupta P, Hammond A, Holowka D, Baird B. Structural determinants for partitioning of lipids and proteins between coexisting fluid phases in giant plasma membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:20-32. [PMID: 17936718 DOI: 10.1016/j.bbamem.2007.08.028] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 08/15/2007] [Accepted: 08/20/2007] [Indexed: 12/11/2022]
Abstract
The structural basis for organizational heterogeneity of lipids and proteins underlies fundamental questions about the plasma membrane of eukaryotic cells. A current hypothesis is the participation of liquid ordered (Lo) membrane domains (lipid rafts) in dynamic compartmentalization of membrane function, but it has been difficult to demonstrate the existence of these domains in live cells. Recently, giant plasma membrane vesicles (GPMVs) obtained by chemically induced blebbing of cultured cells were found to phase separate into optically resolvable, coexisting fluid domains containing Lo-like and liquid disordered (Ld)-like phases as identified by fluorescent probes. In the present study, we used these GPMVs to investigate the structural bases for partitioning of selected lipids and proteins between coexisting Lo-like/Ld-like fluid phases in compositionally complex membranes. Our results with lipid probes show that the structure of the polar headgroups, in addition to acyl chain saturation, can significantly affect partitioning. We find that the membrane anchor of proteins and the aggregation state of proteins both significantly influence their distributions between coexisting fluid phases in these biological membranes. Our results demonstrate the value of GPMVs for characterizing the phase preference of proteins and lipid probes in the absence of detergents and other perturbations of membrane structure.
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Affiliation(s)
- Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA
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70
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Kalipatnapu S, Chattopadhyay A. Membrane Organization and Function of the Serotonin1A Receptor. Cell Mol Neurobiol 2007; 27:1097-116. [PMID: 17710529 DOI: 10.1007/s10571-007-9189-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Accepted: 07/27/2007] [Indexed: 01/02/2023]
Abstract
(1) The serotonin(1A) receptor is a G-protein coupled receptor involved in several cognitive, behavioral, and developmental functions. It binds the neurotransmitter serotonin and signals across the membrane through its interactions with heterotrimeric G-proteins. (2) Lipid-protein interactions in membranes play an important role in the assembly, stability, and function of membrane proteins. The role of membrane environment in serotonin(1A) receptor function is beginning to be addressed by exploring the consequences of lipid manipulations on the ligand binding and G-protein coupling of serotonin(1A) receptors, the ability to functionally solubilize the serotonin(1A) receptor, and the factors influencing the membrane organization of the serotonin(1A) receptor. (3) Recent developments involving the application of detergent-based and detergent-free approaches to understand the membrane organization of the serotonin(1A) receptor under conditions of ligand activation and modulation of membrane lipid content, with an emphasis on membrane cholesterol, are described.
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Affiliation(s)
- Shanti Kalipatnapu
- Divisionof Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0377, USA
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71
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Sengupta P, Baird B, Holowka D. Lipid rafts, fluid/fluid phase separation, and their relevance to plasma membrane structure and function. Semin Cell Dev Biol 2007; 18:583-90. [PMID: 17764993 PMCID: PMC2147712 DOI: 10.1016/j.semcdb.2007.07.010] [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: 04/25/2007] [Accepted: 07/20/2007] [Indexed: 12/20/2022]
Abstract
Novel biophysical approaches combined with modeling and new biochemical data have helped to recharge the lipid raft field and have contributed to the generation of a refined model of plasma membrane organization. In this review, we summarize new information in the context of previous literature to provide new insights into the spatial organization and dynamics of lipids and proteins in the plasma membrane of live cells. Recent findings of large-scale separation of liquid-ordered and liquid-disordered phases in plasma membrane vesicles demonstrate this capacity within the complex milieu of plasma membrane proteins and lipids. Roles for membrane heterogeneity and reorganization in immune cell activation are discussed in light of this new information.
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Affiliation(s)
| | | | - David Holowka
- *To whom correspondence should be addressed: ; 607-255-6140 (phone); 607-255-4137 (fax)
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72
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Abstract
The type I Fc epsilon receptor (Fc epsilon RI) is one of the better understood members of its class and is central to the immunological activation of mast cells and basophils, the key players in immunoglobulin E (IgE)-dependent immediate hypersensitivity. This review provides background information on several distinct regulatory mechanisms controlling this receptor's stimulus-response coupling network. First, we review the current understanding of this network's operation, and then we focus on the inhibitory regulatory mechanisms. In particular, we discuss the different known cytosolic molecules (e.g. kinases, phosphatases, and adapters) as well as cell membrane proteins involved in negatively regulating the Fc epsilon RI-induced secretory responses. Knowledge of this field is developing at a fast rate, as new proteins endowed with regulatory functions are still being discovered. Our understanding of the complex networks by which these proteins exert regulation is limited. Although the scope of this review does not include addressing several important biochemical and biophysical aspects of the regulatory mechanisms, it does provide general insights into a central field in immunology.
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Affiliation(s)
- Jakub Abramson
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
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73
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Yuyama K, Sekino-Suzuki N, Sanai Y, Kasahara K. Translocation of activated heterotrimeric G protein Galpha(o) to ganglioside-enriched detergent-resistant membrane rafts in developing cerebellum. J Biol Chem 2007; 282:26392-400. [PMID: 17623667 DOI: 10.1074/jbc.m705046200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The association of gangliosides with specific proteins in the central nervous system was examined by co-immunoprecipitation with an anti-ganglioside antibody. The monoclonal antibody to the ganglioside GD3 immunoprecipitated phosphoproteins of 40, 53, 56, and 80 kDa from the rat cerebellum. Of these proteins, the 40-kDa protein was identified as the alpha-subunit of a heterotrimeric G protein, G(o) (Galpha(o)). Using sucrose density gradient analysis of cerebellar membranes, Galpha(o), but not Gbetagamma, was observed in detergent-resistant membrane (DRM) raft fractions in which GD3 was abundant after the addition of guanosine 5'-O-(thiotriphosphate) (GTPgammaS), which stabilizes G(o) in its active form. On the other hand, both Galpha(o) and Gbetagamma were excluded from the DRM raft fractions in the presence of guanyl-5'-yl thiophosphate, which stabilizes G(o) in its inactive form. Only Galpha(o) was observed in the DRM fractions from the cerebellum on postnatal day 7, but not from that in adult. After pertussis toxin treatment, Galpha(o) was not observed in the DRM fractions, even from the cerebellum on postnatal day 7. These results indicate the activation-dependent translocation of Galpha(o) into the DRM rafts. Furthermore, Galpha(o) was concentrated in the neuronal growth cones. Treatment with stromal cell-derived factor-1alpha, a physiological ligand for the G protein-coupled receptor, stimulated [(35)S]GTPgammaS binding to Galpha(o) and caused Galpha(o) translocation to the DRM fractions and RhoA translocation to the membrane fraction, leading to the growth cone collapse of cerebellar granule neurons. The collapse was partly prevented by pretreatment with the cholesterol-sequestering and raft-disrupting agent methyl-beta-cyclodextrin. These results demonstrate the involvement of signal-dependent Galpha(o) translocation to the DRM in the growth cone behavior of cerebellar granule neurons.
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Affiliation(s)
- Kohei Yuyama
- Biomembrane Signaling Project 2, Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, 3-18-22 Honkomagome Bunkyo-ku, Tokyo, 113-8613 Japan
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74
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Surviladze Z, Harrison KA, Murphy RC, Wilson BS. FcϵRI and Thy-1 domains have unique protein and lipid compositions. J Lipid Res 2007; 48:1325-35. [PMID: 17387221 DOI: 10.1194/jlr.m600485-jlr200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Receptor activation leads to the dynamic remodeling of the plasma membrane. Previous work using immunoelectron microscopy showed that aggregated high-affinity receptor for immunoglobulin E (FcRI) and aggregated Thy-1, a glycerophosphoinositol (GPI)-anchored protein, have distinct membrane distributions. We now report lipidomics analysis of FcRI- and Thy-1-enriched vesicles obtained by magnetic bead isolation in the absence of detergent. Protein analyses show that FcRI domains are enriched in receptors and associated signaling molecules, whereas Thy-1 domains are devoid of FcRI subunits. Positive and negative ion electrospray mass spectrometry demonstrated that both domains retained a complex mixture of phospholipid classes and molecular species, predominantly glycerophosphocholine, glycerophosphoethanolamine (GPE), and sphingomyelin as well as glycerophosphoserine and GPI lipids. Analysis of total acyl groups showed that < 50% of fatty acids in these domains are fully saturated, inconsistent with the recruitment of aggregated receptors or GPI-anchored proteins to liquid ordered domains. However, further analysis showed that FcRI domains contain two times more sphingomyelin and a high ratio of cholesterol to total fatty acid content compared with Thy 1-enriched domains. Remarkably, plasmenyl glycerophosphoethanolamine phospholipids (plasmalogen GPE) were also 2.5-3 times more abundant in FcRI domains than in the Thy-1 microdomains, whereas most diacyl GPE molecular species were equally abundant in the two domains.
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Affiliation(s)
- Zurab Surviladze
- Department of Pathology, University of New Mexico, Albuquerque, NM, USA
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75
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Hong H, Kitaura J, Xiao W, Horejsi V, Ra C, Lowell CA, Kawakami Y, Kawakami T. The Src family kinase Hck regulates mast cell activation by suppressing an inhibitory Src family kinase Lyn. Blood 2007; 110:2511-9. [PMID: 17513616 PMCID: PMC1988937 DOI: 10.1182/blood-2007-01-066092] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
IgE/antigen-dependent mast cell activation plays a central role in immediate hypersensitivity and other allergic reactions. The Src family tyrosine kinase (SFK) Lyn is activated by the cross-linking of high-affinity IgE receptors (FcepsilonRI). Activated Lyn phosphorylates the FcepsilonRI subunits, beta and gamma, leading to subsequent activation of various signaling pathways. Lyn also plays a negative regulatory function by activating negative regulatory molecules. Another SFK, Fyn, also contributes to mast cell degranulation by inducing Gab2-dependent microtubule formation. Here we show that a third SFK, Hck, plays a critical role in mast cell activation. Degranulation and cytokine production are reduced in FcepsilonRI-stimulated hck(-/-) mast cells. The reduced degranulation can be accounted for by defects in Gab2 phosphorylation and microtubule formation. Importantly, Lyn activity is elevated in hck(-/-) cells, leading to increased phosphorylation of several negative regulators. However, positive regulatory events, such as activation of Syk, Btk, JNK, p38, Akt, and NF-kappaB, are substantially reduced in hck(-/-) mast cells. Analysis of lyn(-/-)hck(-/-), lyn(-/-)FcepsilonRIbeta(-/-), and hck(-/-)FcepsilonRIbeta(-/-) cells shows that Hck exerts these functions via both Lyn-dependent and Lyn-independent mechanisms. Thus, this study has revealed a hierarchical regulation among SFK members to fine-tune mast cell activation.
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Affiliation(s)
- Hong Hong
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, CA 92037, USA
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76
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Barisas BG, Smith SM, Liu J, Song J, Hagen GM, Pecht I, Roess DA. Compartmentalization of the Type I Fcε receptor and MAFA on mast cell membranes. Biophys Chem 2007; 126:209-17. [PMID: 16797115 DOI: 10.1016/j.bpc.2006.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Accepted: 05/17/2006] [Indexed: 11/22/2022]
Abstract
The Mast cell Function-associated Antigen (MAFA) is a membrane glycoprotein on rat mast cells (RBL-2H3) expressed at a ratio of approximately 1:30 with respect to the Type I Fc epsilon receptor (Fc epsilon RI). Despite this stoichiometry, clustering MAFA by its specific mAb G63 substantially inhibits secretion of both granular and de novo synthesized mediators induced upon Fc epsilon RI aggregation. Since the Fc epsilon RIs apparently signal from within raft micro-environments, we investigated possible co-localization of MAFA within these membrane compartments containing aggregated Fc epsilon RI. We used cholera toxin B subunit (CTB) to cluster the raft component ganglioside GM1 and studied the effects of this perturbation on rotation of Fc epsilon RI and MAFA by time-resolved phosphorescence anisotropy of erythrosin-conjugated probes. CTB treatment would be expected to substantially inhibit rotation of raft-associated molecules. Experimentally, CTB has no effect on rotational parameters such as the long-time anisotropy (r(infinity)) of unperturbed Fc epsilon RI or MAFA. However, on cells where Fc epsilon RI-IgE has previously been clustered by antigen (DNP(14)-BSA), CTB treatment increases the Fc epsilon RI-IgE's r(infinity) by 0.010 and MAFA's by 0.014. Similarly, CTB treatment of cells where MAFA had been clustered by mAb G63 increases MAFA's r(infinity) by 0.010 but leaves Fc epsilon RI's unaffected. Evaluation of raft localization of Fc epsilon RI and MAFA using sucrose gradient ultracentrifugation of Triton X-100 treated membrane fragments demonstrates that a significant fraction of MAFA molecules sediments with rafts when Fc epsilon RI is clustered by antigen or when MAFA itself is clustered by mAb G63. The large excess of Fc epsilon RI over MAFA explains why clustering MAFA does not substantively affect Fc epsilon RI dynamics. Moreover, in single-particle tracking studies of individual Fc epsilon RI-IgE or MAFA molecules, these proteins, upon clustering by antigen, move into small membrane compartments of reduced, but similar, dimensions. This provides additional indication of constitutive interactions between Fc epsilon RI and MAFA. Taken together, these results of distinct methodologies suggest that MAFA functions within raft microdomains of the RBL-2H3 cell membrane and thus in close proximity to the Fc epsilon RI which themselves signal from within the raft environment.
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Affiliation(s)
- B George Barisas
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
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77
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DeMorrow S, Glaser S, Francis H, Venter J, Vaculin B, Vaculin S, Alpini G. Opposing actions of endocannabinoids on cholangiocarcinoma growth: recruitment of Fas and Fas ligand to lipid rafts. J Biol Chem 2007; 282:13098-113. [PMID: 17329257 DOI: 10.1074/jbc.m608238200] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cholangiocarcinomas are devastating cancers of biliary origin with limited treatment options. Modulation of the endocannabinoid system is being targeted to develop possible therapeutic strategies for a number of cancers; therefore, we evaluated the effects of the two major endocannabinoids, anandamide and 2-arachidonylglycerol, on numerous cholangiocarcinoma cell lines. Although anandamide was antiproliferative and proapoptotic, 2-arachidonylglycerol stimulated cholangiocarcinoma cell growth. Specific inhibitors for each of the cannabinoid receptors did not prevent either of these effects nor did pretreatment with pertussis toxin, a G(i/o) protein inhibitor, suggesting that anandamide and 2-arachidonylglycerol did not exert their diametric effects through any known cannabinoid receptor or through any other G(i/o) protein-coupled receptor. Using the lipid raft disruptors methyl-beta-cyclodextrin and filipin, we demonstrated that anandamide, but not 2-arachidonylglycerol, requires lipid raft-mediated events to inhibit cellular proliferation. Closer inspection of the lipid raft structures within the cell membrane revealed that although anandamide treatment had no observable effect 2-arachidonylglycerol treatment effectively dissipated the lipid raft structures and caused the lipid raft-associated proteins lyn and flotillin-1 to disperse into the surrounding membrane. In addition, anandamide, but not 2-arachidonylglycerol, induced an accumulation of ceramide, which was required for anandamide-induced suppression of cell growth. Finally we demonstrated that anandamide and ceramide treatment of cholangiocarcinoma cells recruited Fas and Fas ligand into the lipid rafts, subsequently activating death receptor pathways. These findings suggest that modulation of the endocannabinoid system may be a target for the development of possible therapeutic strategies for the treatment of this devastating cancer.
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Affiliation(s)
- Sharon DeMorrow
- Division of Research and Education, Scott and White Hospital and Texas A&M University System Health Science Center College of Medicine, Temple, Texas 76504, USA
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78
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Baumgart T, Hammond AT, Sengupta P, Hess ST, Holowka DA, Baird BA, Webb WW. Large-scale fluid/fluid phase separation of proteins and lipids in giant plasma membrane vesicles. Proc Natl Acad Sci U S A 2007; 104:3165-70. [PMID: 17360623 PMCID: PMC1805587 DOI: 10.1073/pnas.0611357104] [Citation(s) in RCA: 606] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The membrane raft hypothesis postulates the existence of lipid bilayer membrane heterogeneities, or domains, supposed to be important for cellular function, including lateral sorting, signaling, and trafficking. Characterization of membrane lipid heterogeneities in live cells has been challenging in part because inhomogeneity has not usually been definable by optical microscopy. Model membrane systems, including giant unilamellar vesicles, allow optical fluorescence discrimination of coexisting lipid phase types, but thus far have focused on coexisting optically resolvable fluid phases in simple lipid mixtures. Here we demonstrate that giant plasma membrane vesicles (GPMVs) or blebs formed from the plasma membranes of cultured mammalian cells can also segregate into micrometer-scale fluid phase domains. Phase segregation temperatures are widely spread, with the vast majority of GPMVs found to form optically resolvable domains only at temperatures below approximately 25 degrees C. At 37 degrees C, these GPMV membranes are almost exclusively optically homogenous. At room temperature, we find diagnostic lipid phase fluorophore partitioning preferences in GPMVs analogous to the partitioning behavior now established in model membrane systems with liquid-ordered and liquid-disordered fluid phase coexistence. We image these GPMVs for direct visual characterization of protein partitioning between coexisting liquid-ordered-like and liquid-disordered-like membrane phases in the absence of detergent perturbation. For example, we find that the transmembrane IgE receptor FcepsilonRI preferentially segregates into liquid-disordered-like phases, and we report the partitioning of additional well known membrane associated proteins. Thus, GPMVs now provide an effective approach to characterize biological membrane heterogeneities.
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Affiliation(s)
| | - Adam T. Hammond
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Prabuddha Sengupta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Samuel T. Hess
- Department of Physics and Astronomy, University of Maine, Orono, ME 04469
| | - David A. Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Barbara A. Baird
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853; and
| | - Watt W. Webb
- *School of Applied and Engineering Physics and
- To whom correspondence should be addressed at:
Cornell University, 212 Clark Hall, Ithaca, NY 14853. E-mail:
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79
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Kitaura J, Kawakami Y, Maeda-Yamamoto M, Horejsi V, Kawakami T. Dysregulation of Src Family Kinases in Mast Cells from Epilepsy-Resistant ASK versus Epilepsy-Prone EL Mice. THE JOURNAL OF IMMUNOLOGY 2006; 178:455-62. [PMID: 17182584 DOI: 10.4049/jimmunol.178.1.455] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
EL mice have been used as a model of epilepsy, whereas ASK mice are an epilepsy-resistant variant originating from a colony of EL mice. Mast cell-dependent anaphylaxis is easily inducible by stimulation with IgE and Ag in ASK mice, whereas EL mice are resistant to such stimuli. In this study we have characterized mast cells derived from these two strains. ASK mast cells proliferated more vigorously than EL cells in response to IL-3 and stem cell factor. Although ASK mast cells degranulated less vigorously than EL mast cells upon stimulation with IgE and Ag, ASK cells produced and secreted several-fold more TNF-alpha and IL-2 than EL cells. Consistent with the similarities of these ASK and EL mast cell responses with phenotypes of lyn(-/-) and wild-type mast cells, respectively, Lyn activity was reduced in ASK cells. In addition to the impaired Lyn activity, ASK cells just like lyn(-/-) cells exhibited reduced Syk activity, prolonged activation of ERK and JNK, and enhanced activation of Akt. Furthermore, the lipid raft-resident transmembrane adaptor protein Cbp/PAG that associates with Lyn was hypophosphorylated in ASK cells. Importantly, similar to lyn(-/-) cells, Fyn was hyperactivated in ASK cells. Therefore, these results are consistent with the notion that Lyn-dependent phosphorylation of Cbp/PAG negatively regulates Src family kinases. This study also suggests that reduced activity of Lyn, a negative regulator of mast cell activation, underlies the susceptibility of ASK mice to anaphylaxis and implies that dysregulation of Lyn and other Src family kinases contributes to epileptogenesis.
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Affiliation(s)
- Jiro Kitaura
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA
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80
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Aker J, Borst JW, Karlova R, de Vries S. The Arabidopsis thaliana AAA protein CDC48A interacts in vivo with the somatic embryogenesis receptor-like kinase 1 receptor at the plasma membrane. J Struct Biol 2006; 156:62-71. [PMID: 16621602 DOI: 10.1016/j.jsb.2006.03.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Revised: 03/01/2006] [Accepted: 03/08/2006] [Indexed: 10/24/2022]
Abstract
Fluorescent cell division cycle (CDC)48 proteins were studied in living plant protoplasts. CDC48A and somatic embryogenesis receptor like kinase 1 (SERK1) were found to co-localize in the endoplasmatic reticulum (ER) and at the plasma membrane (PM), but not in endosomal compartments. Fluorescent lifetime imaging microscopy (FLIM) was used to detect Förster resonance energy transfer (FRET) between CrFP/YFP-tagged CDC48A and SERK1. FRET is indicative of direct protein-protein interaction. CDC48A was found to interact only with SERK1 in small areas at the PM, but not in endosomes. These findings confirm and extend our previous findings that CDC48A in plants directly interacts with SERK1.
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Affiliation(s)
- José Aker
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
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81
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Abstract
Lipid rafts are membrane microdomains rich in cholesterol and glycosphingolipids that have been implicated in the regulation of intracellular protein trafficking. During exocytosis, a class of proteins termed SNAREs mediate secretory granule-plasma membrane fusion. To investigate the role of lipid rafts in secretory granule exocytosis, we examined the raft association of SNARE proteins and SNARE complexes in rat basophilic leukemia (RBL) mast cells. The SNARE protein SNAP-23 co-localized with a lipid raft marker and was present in detergent-insoluble lipid raft microdomains in RBL cells. By contrast, only small amounts (<20%) of the plasma membrane SNARE syntaxin 4 or the granule-associated SNARE vesicle-associated membrane protein (VAMP)-2 were present in these microdomains. Despite this, essentially all syntaxin 4 and most of VAMP-2 in these rafts were present in SNARE complexes containing SNAP-23, while essentially none of these complexes were present in nonraft membranes. Whereas SNAP-23 is membrane anchored by palmitoylation, the association of the transmembrane protein syntaxin 4 with lipid rafts was because of its binding to SNAP-23. After stimulating mast cells exocytosis, the amount of syntaxin 4 and VAMP-2 present in rafts increased twofold, and these proteins were now present in raft-associated phospho-SNAP-23/syntaxin 4/VAMP-2 complexes, revealing differential association of SNARE fusion complexes during the process of regulated exocytosis.
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Affiliation(s)
- Niti Puri
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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82
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Kato N, Nakanishi M, Hirashima N. Flotillin-1 regulates IgE receptor-mediated signaling in rat basophilic leukemia (RBL-2H3) cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:147-54. [PMID: 16785509 DOI: 10.4049/jimmunol.177.1.147] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Cross-linking of high-affinity IgE receptors by multivalent Ag on mast cells (rat basophilic leukemia (RBL)-2H3) induces the phosphorylation of ITAM motifs of an IgE receptor by Src family tyrosine kinase, Lyn. The phosphorylation of IgE receptors is followed by a series of intracellular signals, such as Ca(2+) mobilization, MAPK activation, and degranulation. Therefore, Lyn is a key molecule in the activation of mast cells, but the molecular mechanisms for the activation of Lyn are still unclear. Recently, it is suggested that the localization of Lyn in lipid rafts is critical for its activation in several cell lines, although the precise mechanism is still unknown. In this study, we found that flotillin-1, which is localized in lipid rafts, is involved in the process of Lyn activation. We obtained flotillin-1 knockdown (KD)(2) rat basophilic leukemia (RBL)-2H3 cells, which express a low level of flotillin-1. In the flotillin-1 KD cells, we observed a significant decrease in Ca(2+) mobilization, the phosphorylation of ERKs, tyrosine phosphorylation of the gamma-subunit of IgE receptor, and IgE receptor-mediated degranulation. We also found that flotillin-1 is constitutively associated with Lyn in lipid rafts in RBL-2H3 cells, and Ag stimulation induced the augmentation of flotillin-1 binding to Lyn, resulting in enhancement of kinase activity of Lyn. These results suggest that flotillin-1 is an essential molecule in IgE receptor-mediated mast cell activation, and regulates the kinase activity of Lyn in lipid rafts.
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MESH Headings
- Animals
- Calcium/metabolism
- Calcium Signaling/physiology
- Cell Degranulation/physiology
- Cell Line, Tumor
- Enzyme Activation/physiology
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Leukemia, Basophilic, Acute/enzymology
- Leukemia, Basophilic, Acute/immunology
- Leukemia, Basophilic, Acute/metabolism
- Mast Cells/enzymology
- Mast Cells/immunology
- Mast Cells/metabolism
- Membrane Microdomains/enzymology
- Membrane Microdomains/immunology
- Membrane Microdomains/metabolism
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Phosphorylation
- Rats
- Receptors, IgE/biosynthesis
- Receptors, IgE/metabolism
- Receptors, IgE/physiology
- Signal Transduction/immunology
- Transfection
- Tyrosine/metabolism
- src-Family Kinases/metabolism
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Affiliation(s)
- Naoto Kato
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
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83
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Fattakhova G, Masilamani M, Borrego F, Gilfillan AM, Metcalfe DD, Coligan JE. The high-affinity immunoglobulin-E receptor (FcepsilonRI) is endocytosed by an AP-2/clathrin-independent, dynamin-dependent mechanism. Traffic 2006; 7:673-85. [PMID: 16637889 DOI: 10.1111/j.1600-0854.2006.00423.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Aggregation of the high-affinity immunoglobulin E (IgE) receptor (FcepsilonRI), expressed on mast cells and basophils, initiates the immediate hypersensitivity reaction. Aggregated FcepsilonRI has been reported to rapidly migrate to lipid rafts in RBL-2H3 cells. We confirmed that aggregated FcepsilonRI is found in the lipid raft fractions of cellular lysates. Furthermore, we show that the cross-linked FcepsilonRI remains associated with detergent-resistant structures upon internalization. Previous morphological studies have reported that aggregated FepsiloncRI is endocytosed via clathrin-coated pits, which in general are not lipid raft associated. To address this apparent discrepancy, we employed siRNA to suppress expression of components of the clathrin-mediated internalization machinery, namely, clathrin heavy chain, and the AP-2 (alpha-adaptin or mu2-subunit). Transferrin receptor (TfR) is endocytosed by a clathrin-mediated process and, as expected, each transfected siRNA caused a two to threefold elevation of TfR surface expression and almost completely inhibited its endocytosis. In contrast, there was no effect on surface expression levels of FcepsilonRI nor on the endocytosis of the dinitrophenyl-human serum albumin (DNP-HSA)/IgE/FcepsilonRI complex. On the contrary, internalization of DNP-HSA/IgE/FcepsilonRI was inhibited by overexpression of a dominant-negative dynamin mutant. We conclude that internalization of cross-linked FcRI does not require the AP-2/clathrin complex but is dynamin-dependent and may be lipid raft mediated.
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Affiliation(s)
- Gul'nar Fattakhova
- Receptor Cell Biology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
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84
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Dumitru CA, Gulbins E. TRAIL activates acid sphingomyelinase via a redox mechanism and releases ceramide to trigger apoptosis. Oncogene 2006; 25:5612-25. [PMID: 16636669 DOI: 10.1038/sj.onc.1209568] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have previously shown that activation of the acid sphingomyelinase (ASM), the release of ceramide and the formation of ceramide-enriched membrane domains are central for the induction of apoptosis by CD95. Here, we demonstrate that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95 activate the ASM via a redox mechanism resulting in release of ceramide and formation of ceramide-enriched membrane platforms. Ceramide-enriched membrane platforms serve to cluster DR5 upon stimulation. Antioxidants prevent TRAIL-mediated stimulation of ASM, the release of ceramide, the formation of ceramide-enriched membrane platforms and the induction of apoptosis by TRAIL. Further, ASM-deficient splenocytes fail to cluster DR5 in ceramide-enriched membrane domains upon TRAIL stimulation and resist TRAIL-induced apoptosis, events that were restored by addition of natural C(16)-ceramide. A dose-response analysis indicates that ceramide-enriched membrane platforms greatly sensitized tumor cells to TRAIL-induced apoptosis. Our data indicate that ceramide-enriched membrane platforms are required for the signaling of TRAIL-DR5 complexes under physiological conditions.
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Affiliation(s)
- C A Dumitru
- Department of Molecular Biology, University of Duisburg-Essen, Hufelandstrasse 55, 45122 Essen, Germany
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85
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Kovarova M, Wassif CA, Odom S, Liao K, Porter FD, Rivera J. Cholesterol deficiency in a mouse model of Smith-Lemli-Opitz syndrome reveals increased mast cell responsiveness. ACTA ACUST UNITED AC 2006; 203:1161-71. [PMID: 16618793 PMCID: PMC2121200 DOI: 10.1084/jem.20051701] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mutation of the 3β-hydroxysterol Δ7-reductase gene (Dhcr7−/−) results in Smith-Lemli-Opitz syndrome (SLOS). Patients, and genetically altered mice, are unable to produce cholesterol and accumulate 7-dehydrocholesterol (DHC) in serum and tissue. This causes multiple growth and developmental abnormalities as well as immune system anomalies including allergy. Because cholesterol is a key component of liquid-ordered membranes (lipid rafts) and these domains have been implicated in regulating mast cell activation, we examined whether mast cell responsiveness is altered in this model. Mast cells derived from Dhcr7−/− mice (DHCR KO) showed constitutive cytokine production and hyper-degranulation after stimulation of the high affinity IgE receptor (FcɛRI). DHCR KO mast cells, but not wild-type mast cells, accumulated DHC in lipid rafts. DHC partially disrupted lipid raft stability and displaced Lyn kinase protein and activity from lipid rafts. This led to down-regulation of some Lyn-dependent signaling events but increased Fyn kinase activity and Akt phosphorylation. The Lyn-dependent phosphorylation of Csk-binding protein, which negatively regulates Fyn activity, was decreased. This phenotype reproduces some of the characteristics of Lyn-null mast cells, which also demonstrate hyper-degranulation. These findings provide the first evidence of lipid raft dysfunction in SLOS and may explain the observed association of allergy with SLOS.
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Affiliation(s)
- Martina Kovarova
- Molecular Inflammation Section, Molecular Immunology and Inflammation Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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86
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Frankel DJ, Pfeiffer JR, Surviladze Z, Johnson AE, Oliver JM, Wilson BS, Burns AR. Revealing the topography of cellular membrane domains by combined atomic force microscopy/fluorescence imaging. Biophys J 2006; 90:2404-13. [PMID: 16415053 PMCID: PMC1403184 DOI: 10.1529/biophysj.105.073692] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Simultaneous atomic force microscopy (AFM) and confocal fluorescence imaging were used to observe in aqueous buffer the three-dimensional landscape of the inner surface of membrane sheets stripped from fixed tumor mast cells. The AFM images reveal prominent, irregularly shaped raised domains that label with fluorescent markers for both resting and activated immunoglobin E receptors (FcepsilonRI), as well as with cholera toxin-aggregated GM1 and clathrin. The latter suggests that coated pits bud from these regions. These features are interspersed with flatter regions of membrane and are frequently surrounded and interconnected by cytoskeletal assemblies. The raised domains shrink in height by approximately 50% when cholesterol is extracted with methyl-beta-cyclodextrin. Based on composition, the raised domains seen by AFM correspond to the cholesterol-enriched dark patches observed in transmission electron microscopy (TEM). These patches were previously identified as sites of signaling and endocytosis based on their localization of activated FcepsilonRI, at least 10 associated signaling molecules, and the presence of clathrin-coated pits. Overall the data suggest that signaling and endocytosis occur in mast cells from raised membrane regions that depend on cholesterol for their integrity and may be organized in specific relationship with the cortical cytoskeleton.
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Affiliation(s)
- D J Frankel
- Biomolecular Materials and Interfaces Department, MS1413 Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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87
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Holowka D, Gosse JA, Hammond AT, Han X, Sengupta P, Smith NL, Wagenknecht-Wiesner A, Wu M, Young RM, Baird B. Lipid segregation and IgE receptor signaling: A decade of progress. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:252-9. [PMID: 16054713 DOI: 10.1016/j.bbamcr.2005.06.007] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 06/11/2005] [Accepted: 06/15/2005] [Indexed: 11/25/2022]
Abstract
Recent work to characterize the roles of lipid segregation in IgE receptor signaling has revealed a mechanism by which segregation of liquid ordered regions from disordered regions of the plasma membrane results in protection of the Src family kinase Lyn from inactivating dephosphorylation by a transmembrane tyrosine phosphatase. Antigen-mediated crosslinking of IgE receptors drives their association with the liquid ordered regions, commonly called lipid rafts, and this facilitates receptor phosphorylation by active Lyn in the raft environment. Previous work showed that the membrane skeleton coupled to F-actin regulates stimulated receptor phosphorylation and downstream signaling processes, and more recent work implicates cytoskeletal interactions with ordered lipid rafts in this regulation. These and other results provide an emerging view of the complex role of membrane structure in orchestrating signal transduction mediated by immune and other cell surface receptors.
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Affiliation(s)
- David Holowka
- Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853-1301, USA
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88
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Gosse JA, Wagenknecht-Wiesner A, Holowka D, Baird B. Transmembrane sequences are determinants of immunoreceptor signaling. THE JOURNAL OF IMMUNOLOGY 2005; 175:2123-31. [PMID: 16081778 DOI: 10.4049/jimmunol.175.4.2123] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To investigate structural features critical for signal initiation by Ag-stimulated immunoreceptors, we constructed a series of single-chain chimeric receptors that incorporate extracellular human Fc epsilonRIalpha for IgE binding, a variable transmembrane (TM) segment, and the ITAM-containing cytoplasmic tail of the TCR zeta-chain. We find that functional responses mediated by these receptors are strongly dependent on their TM sequences, and these responses are highly correlated to cross-link-dependent association with detergent-resistant lipid rafts. For one chimera designated alpha Fzeta, mutation of a TM cysteine abolishes robust signaling and lipid raft association. In addition, TM disulfide-mediated oligomerization of another chimeric receptor, alpha zetazeta, enhances signaling. These results demonstrate an important role for TM segments in immunoreceptor signaling and a strong correspondence between strength of signaling and cross-link-dependent partitioning into ordered membrane domains.
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Affiliation(s)
- Julie A Gosse
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA
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89
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Kawakami T, Kitaura J. Mast cell survival and activation by IgE in the absence of antigen: a consideration of the biologic mechanisms and relevance. THE JOURNAL OF IMMUNOLOGY 2005; 175:4167-73. [PMID: 16177053 PMCID: PMC1415266 DOI: 10.4049/jimmunol.175.7.4167] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mast cells are not only major effector cells in allergy and host defense against parasites and bacteria but also important cellular components in other immune responses. Recent studies on the effects of monomeric IgE on mast cell survival and activation have made an impact on our view of the IgE binding to its high-affinity receptors, Fc epsilonRI. Traditionally, IgE binding to Fc epsilonRI has been considered as a passive action of "sensitization" before receptor aggregation by Ag. However, recent studies indicate that at high concentrations some monoclonal IgEs have effects on mast cells similar to or identical to those induced by IgE+Ag stimulation. These effects may be due to induction of Fc epsilonRI aggregation by these IgEs in the absence of Ag. This review will synthesize recent findings of the heterogeneity of IgEs in their ability to induce survival and activation events, their mechanisms, the potential in vivo significance of IgE-Fc epsilonRI interactions, and the implications of the mouse studies to human diseases.
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Affiliation(s)
- Toshiaki Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA.
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90
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Buk DM, Renner O, Graeve L. Increased association with detergent-resistant membranes/lipid rafts of apically targeted mutants of the interleukin-6 receptor gp80. Eur J Cell Biol 2005; 84:819-31. [PMID: 16270750 DOI: 10.1016/j.ejcb.2005.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Interleukin (IL)-6 is an important cytokine in inflammatory processes, differentiation and growth. The IL-6 receptor complex comprises the specific IL-6 receptor (gp80) and two molecules of the signal tranducing component gp130 which transduces the signal into the nucleus via the Jak-STAT pathway. Both, gp80 and gp130 are sorted preferentially to the basolateral membrane of polarised Madin-Darby canine kidney (MDCK) cells. Previously, we have shown that gp130 partially localises to detergent-resistant membranes (DRMs)/lipid rafts and that lipid raft integrity is crucial for signalling to occur. Here we now demonstrate that wild-type gp80 is associated with DRMs only to a minor extent. However, gp80 mutants which lack parts of the cytoplasmic domain and therefore are more apically expressed than the wild type show an increased affinity for the liquid-ordered membrane domain. Studies with non-polarised MDCK cells suggest that the lipid raft association of the different mutants of gp80 precedes the establishment of cell polarity. Our findings suggest that lipid rafts play a role in the sorting of apically targeted gp80.
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Affiliation(s)
- Deborah M Buk
- Institut für Biologische Chemie und Ernährungswissenschaft, Universität Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
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91
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López JA, del Conde I, Shrimpton CN. Receptors, rafts, and microvesicles in thrombosis and inflammation. J Thromb Haemost 2005; 3:1737-44. [PMID: 16102040 DOI: 10.1111/j.1538-7836.2005.01463.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hemostasis at sites of blood vessel injury and its pathologic counterpart, thrombosis, involve a complex interplay between several blood elements: soluble proteins of the blood coagulation system, blood cells (most prominently platelets) and cell fragments, and elements of the vessel wall (endothelial cells and, at sites of injury, the exposed matrix and deeper cellular components). In this review, we focus on ways in which specialized membrane microdomains known as lipid rafts are involved in various phases of hemostasis and thrombosis.
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Affiliation(s)
- J A López
- Baylor College of Medicine, Thrombosis Research Section, Houston, TX 77030, USA.
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92
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Kubo SI, Nemani VM, Chalkley RJ, Anthony MD, Hattori N, Mizuno Y, Edwards RH, Fortin DL. A combinatorial code for the interaction of alpha-synuclein with membranes. J Biol Chem 2005; 280:31664-72. [PMID: 16020543 DOI: 10.1074/jbc.m504894200] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Considerable genetic and pathological evidence has implicated the small, soluble protein alpha-synuclein in the pathogenesis of familial and sporadic forms of Parkinsons disease (PD). However, the precise role of alpha-synuclein in the disease process as well as its normal function remain poorly understood. We recently found that an interaction with lipid rafts is crucial for the normal, pre-synaptic localization of alpha-synuclein. To understand how alpha-synuclein interacts with lipid rafts, we have now developed an in vitro binding assay to rafts purified from native membranes. Recapitulating the specificity observed in vivo, recombinant wild type but not PD-associated A30P mutant alpha-synuclein binds to lipid rafts isolated from cultured cells and purified synaptic vesicles. Proteolytic digestion of the rafts does not disrupt the binding of alpha-synuclein, indicating an interaction with lipid rather than protein components of these membranes. We have also found that alpha-synuclein binds directly to artificial membranes whose lipid composition mimics that of lipid rafts. The binding of alpha-synuclein to these raft-like liposomes requires acidic phospholipids, with a preference for phosphatidylserine (PS). Interestingly, a variety of synthetic PS with defined acyl chains do not support binding when used individually. Rather, the interaction with alpha-synuclein requires a combination of PS with oleic (18:1) and polyunsaturated (either 20:4 or 22:6) fatty acyl chains, suggesting a role for phase separation within the membrane. Furthermore, alpha-synuclein binds with higher affinity to artificial membranes with the PS head group on the polyunsaturated fatty acyl chain rather than on the oleoyl side chain, indicating a stringent combinatorial code for the interaction of alpha-synuclein with membranes.
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Affiliation(s)
- Shin-ichiro Kubo
- Department of Neurology, Graduate Program in Biomedical Sciences, University of California, San Francisco, California 94143-2140, USA
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93
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Affiliation(s)
- Lawrence Rajendran
- Max-Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307, Dresden, Germany
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94
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Furumoto Y, Gonzalez-Espinosa C, Gomez G, Kovarova M, Odom S, Parravicini V, Ryana JJ, Rivera J. Rethinking the role of Src family protein tyrosine kinases in the allergic response: new insights on the functional coupling of the high affinity IgE receptor. Immunol Res 2005; 30:241-53. [PMID: 15477664 DOI: 10.1385/ir:30:2:241] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Antigen-induced cross-linking of immunoglobulin E (IgE) antibodies bound to the high-affinity IgE receptor (FcepsilonRI), on mast cells results in the release of mediators that initiate an inflammatory response. This normal immune response has been abducted by immunological adaptation, through the production of IgE antibodies to normally innocuous substances, to cause allergic disease. Therefore, understanding the molecular requirements in IgE-dependent mast-cell activation holds promise for therapeutic intervention in disease. Recent investigation on the functional coupling of FcepsilonRI to the intracellular signaling apparatus has provided paradigm-altering insights on the importance and function of Src family protein tyrosine kinases (Src PTK) in mast-cell activation. In this synopsis, we review the current knowledge on the role of the Src PTKs, Fyn and Lyn, in mast-cell activation and discuss the implications of our findings on allergic disease.
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Affiliation(s)
- Yasuko Furumoto
- Molecular Inflammation Section, Molecular Immunology and Inflammation Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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95
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Fortin DL, Troyer MD, Nakamura K, Kubo SI, Anthony MD, Edwards RH. Lipid rafts mediate the synaptic localization of alpha-synuclein. J Neurosci 2005; 24:6715-23. [PMID: 15282274 PMCID: PMC6729723 DOI: 10.1523/jneurosci.1594-04.2004] [Citation(s) in RCA: 402] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alpha-synuclein contributes to the pathogenesis of Parkinson's disease (PD), but its precise role in the disorder and its normal function remain poorly understood. Consistent with a presumed role in neurotransmitter release and its prominent deposition in the dystrophic neurites of PD, alpha-synuclein localizes almost exclusively to the nerve terminal. In brain extracts, however, alpha-synuclein behaves as a soluble, monomeric protein. Using a binding assay to characterize the association of alpha-synuclein with cell membranes, we find that alpha-synuclein binds saturably and with high affinity to characteristic intracellular structures that double label for components of lipid rafts. Biochemical analysis demonstrates the interaction of alpha-synuclein with detergent-resistant membranes and reveals a shift in electrophoretic mobility of the raft-associated protein. In addition, the A30P mutation associated with PD disrupts the interaction of alpha-synuclein with lipid rafts. Furthermore, we find that both the A30P mutation and raft disruption redistribute alpha-synuclein away from synapses, indicating an important role for raft association in the normal function of alpha-synuclein and its role in the pathogenesis of PD.
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Affiliation(s)
- Doris L Fortin
- Department of Neurology, Graduate Programs in Biomedical Sciences, Cell Biology and Neuroscience, University of California San Francisco School of Medicine, San Francisco, California 94143-2140, USA
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96
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Fleischer A, Ghadiri A, Dessauge F, Duhamel M, Cayla X, Garcia A, Rebollo A. Bad-Dependent Rafts Alteration Is a Consequence of an Early Intracellular Signal Triggered by Interleukin-4 Deprivation. Mol Cancer Res 2004. [DOI: 10.1158/1541-7786.674.2.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Many molecules are inducibly localized in lipid rafts, and their alteration inhibits early activation events, supporting a critical role for these domains in signaling. Using confocal microscopy and cellular fractionation, we have shown that the pool of Bad, attached to lipid rafts in proliferating cells, is released when cells undergo apoptosis. Kinetic studies indicate that rafts alteration is a consequence of an intracellular signal triggered by interleukin-4 deprivation. Growth factor deprivation in turn induces PP1α phosphatase activation, responsible for cytoplasmic Bad dephosphorylation as well as caspase-9 and caspase-3 activation. Caspases translocate to rafts and induce their modification followed by translocation of Bad from rafts to mitochondria, which correlates with apoptosis. Taken together, our results suggest that alteration of lipid rafts is an early event in the apoptotic cascade indirectly induced by interleukin-4 deprivation via PP1α activation, dephosphorylation of cytoplasmic Bad, and caspase activation.
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Affiliation(s)
- Aarne Fleischer
- 1Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière
| | - Ata Ghadiri
- 1Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière
| | - Frédéric Dessauge
- 1Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière
| | - Marianne Duhamel
- 1Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière
| | - Xavier Cayla
- 3Equipe Hypophyse, UMR6073 INRA-Centre National de la Recherche Scientifique, Université de Tours, Physiologie de la Reproduction et des Comportements, Nouzilly, France
| | - Alphonse Garcia
- 2Unité de Chimie Organique, Institut Pasteur, Paris, France and
| | - Angelita Rebollo
- 1Laboratoire d'Immunologie Cellulaire et Tissulaire, Institut National de la Sante et de la Recherche Medicale U543, Hôpital Pitié Salpetrière
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97
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Young RM, Zheng X, Holowka D, Baird B. Reconstitution of regulated phosphorylation of FcepsilonRI by a lipid raft-excluded protein-tyrosine phosphatase. J Biol Chem 2004; 280:1230-5. [PMID: 15537644 DOI: 10.1074/jbc.m408339200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To examine the exquisite regulation of IgE-FcepsilonRI tyrosine phosphorylation by Lyn kinase that is stimulated by antigen-mediated cross-linking, we utilized co-expression of FcepsilonRI and Lyn in Chinese hamster ovary cells, which results in high basal levels of Lyn kinase activity and spontaneous phosphorylation of FcepsilonRI. We found that co-expression of a lipid raft-excluded transmembrane tyrosine phosphatase, PTPalpha, suppresses Lyn kinase activity and markedly reduces the level of spontaneous phosphorylation of FcepsilonRI, while facilitating its antigen-stimulated phosphorylation. Other tyrosine phosphatases, including SHP-1, CD45, and a lipid raft-preferring chimeric version of PTPalpha fail to reconstitute antigen-dependent FcepsilonRI phosphorylation. We concluded that both substrate specificity and submembrane location are critical to phosphatase-mediated regulation of Lyn kinase activity that supports activation of FcepsilonRI.
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Affiliation(s)
- Ryan M Young
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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98
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Wollscheid B, von Haller PD, Yi E, Donohoe S, Vaughn K, Keller A, Nesvizhskii AI, Eng J, Li XJ, Goodlett DR, Aebersold R, Watts JD. Lipid raft proteins and their identification in T lymphocytes. Subcell Biochem 2004; 37:121-52. [PMID: 15376619 DOI: 10.1007/978-1-4757-5806-1_3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
This review focuses on how membrane lipid rafts have been detected and isolated, mostly from lymphocytes, and their associated proteins identified. These proteins include transmembrane antigens/receptors, GPI-anchored proteins, cytoskeletal proteins, Src-family protein kinases, G-proteins, and other proteins involved in signal transduction. To further understand the biology of lipid rafts, new methodological approaches are needed to help characterize the raft protein component, and changes that occur in this component as a result of cell perturbation. We describe the application of new proteomic approaches to the identification and quantification of raft proteins in T-lymphocytes. Similar approaches, applied to other model cell systems, will provide valuable new insights into both cellular signal transduction and lipid raft biology.
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99
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Urtz N, Olivera A, Bofill-Cardona E, Csonga R, Billich A, Mechtcheriakova D, Bornancin F, Woisetschläger M, Rivera J, Baumruker T. Early activation of sphingosine kinase in mast cells and recruitment to FcepsilonRI are mediated by its interaction with Lyn kinase. Mol Cell Biol 2004; 24:8765-77. [PMID: 15367693 PMCID: PMC516729 DOI: 10.1128/mcb.24.19.8765-8777.2004] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sphingosine kinase has been recognized as an essential signaling molecule that mediates the intracellular conversion of sphingosine to sphingosine-1-phosphate. In mast cells, induction of sphingosine kinase and generation of sphingosine-1-phosphate have been linked to the initial rise in Ca(2+), released from internal stores, and to degranulation. These events either precede or are concomitant with the activation of phospholipase C-gamma and the generation of inositol trisphosphate. Here we show that sphingosine kinase type 1 (SPHK1) interacts directly with the tyrosine kinase Lyn and that this interaction leads to the recruitment of this lipid kinase to the high-affinity receptor for immunoglobulin E (FcepsilonRI). The interaction of SPHK1 with Lyn caused enhanced lipid and tyrosine kinase activity. After FcepsilonRI triggering, enhanced sphingosine kinase activity was associated with FcepsilonRI in sphingolipid-enriched rafts of mast cells. Bone marrow-derived mast cells from Lyn(-/)(-) mice, compared to syngeneic wild-type cells, were defective in the initial induction of SPHK1 activity, and the defect was overcome by retroviral Lyn expression. These findings position the activation of SPHK1 as an FcepsilonRI proximal event.
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Affiliation(s)
- Nicole Urtz
- Novartis Institute for Biomedical Research, Brunner Strasse 59, A-1235 Vienna, Austria
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100
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Kraft S, Rana S, Jouvin MH, Kinet JP. The role of the FcepsilonRI beta-chain in allergic diseases. Int Arch Allergy Immunol 2004; 135:62-72. [PMID: 15316148 DOI: 10.1159/000080231] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The high affinity receptor for IgE, FcepsilonRI, is a multimeric surface receptor that is expressed exclusively as a tetramer on rodent cells, but exists as a tetramer or trimer on human cells. The tetrameric form is expressed on effector cells of allergic responses such as mast cells and basophils and is composed of an IgE-binding alpha-subunit, a beta-subunit and a gamma-subunit dimer. Complexes lacking the beta-subunit are found on human antigen-presenting cells. On mast cells and basophils, FcepsilonRI is essential for IgE-mediated acute allergic reactions. Crosslinking of FcepsilonRI by IgE and multivalent antigen induces a signaling cascade that culminates in the release of preformed mediators and the synthesis of lipid mediators and cytokines. The beta-subunit functions as an amplifier of FcepsilonRI expression and signaling. As a consequence, strongly enhanced mast cell effector functions and in vivo allergic reactions can be observed in the presence of FcepsilonRIbeta. In contrast, a truncated beta-isoform (betaT) that is produced by alternative splicing acts as an inhibitor of FcepsilonRI surface expression. Thus, by producing two proteins with antagonistic functions, the FcepsilonRIbeta gene could serve as a potent regulator of allergic responses. In addition, the genomic region encompassing the beta-chain has been linked to atopy and a number of polymorphisms within the FcepsilonRIbeta gene are associated with various atopic diseases. It remains to be elucidated how these polymorphisms might affect the allergic phenotype. These functions of the beta-chain together with the described genetic linkages to atopy make it a candidate for a role in the pathophysiology of allergic diseases.
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Affiliation(s)
- Stefan Kraft
- Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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