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Development of a Novel Virus-Like Particle Vaccine Platform That Mimics the Immature Form of Alphavirus. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2017; 24:CVI.00090-17. [PMID: 28515133 PMCID: PMC5498722 DOI: 10.1128/cvi.00090-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 05/04/2017] [Indexed: 12/27/2022]
Abstract
Virus-like particles (VLPs) are noninfectious multiprotein structures that are engineered to self-assemble from viral structural proteins. Here, we developed a novel VLP-based vaccine platform utilizing VLPs from the chikungunya virus. We identified two regions within the envelope protein, a structural component of chikungunya, where foreign antigens can be inserted without compromising VLP structure. Our VLP displays 480 copious copies of an inserted antigen on the VLP surface in a highly symmetric manner and is thus capable of inducing strong immune responses against any inserted antigen. Furthermore, by mimicking the structure of the immature form of the virus, we altered our VLP's in vivo dynamics and enhanced its immunogenicity. We used the circumsporozoite protein (CSP) of the Plasmodium falciparum malaria parasite as an antigen and demonstrated that our VLP-based vaccine elicits strong immune responses against CSP in animals. The sera from immunized monkeys protected mice from malaria infection. Likewise, mice vaccinated with P. yoelii CSP-containing VLPs were protected from an infectious sporozoite challenge. Hence, our uniquely engineered VLP platform can serve as a blueprint for the development of vaccines against other pathogens and diseases.
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Saintamand A, Rouaud P, Garot A, Saad F, Carrion C, Oblet C, Cogné M, Pinaud E, Denizot Y. The IgH 3' regulatory region governs μ chain transcription in mature B lymphocytes and the B cell fate. Oncotarget 2016; 6:4845-52. [PMID: 25742787 PMCID: PMC4467119 DOI: 10.18632/oncotarget.3010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 12/21/2014] [Indexed: 12/11/2022] Open
Abstract
We report that the IgH 3' regulatory region (3'RR) has no role on μ chain transcription and pre-BCR expression in B cell progenitors. In contrast, analysis of heterozygous IgH aΔ3'RR/bwt mice indicated that the 3'RR controls μ chain transcripts in mature splenocytes and impacts membrane IgM density without obvious effect on BCR signals (colocalisation with lipid rafts and phosphorylation of Erk and Akt after BCR crosslinking). Deletion of the 3'RR modulates the B cell fate to less marginal zone B cells. In conclusion, the 3'RR is dispensable for pre-BCR expression and necessary for optimal commitments toward the marginal zone B cell fate. These results reinforce the concept of a dual regulation of the IgH locus transcription and accessibility by 5' elements at immature B cell stages, and by the 3'RR as early as the resting mature B cell stage and then along further activation and differentiation.
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Affiliation(s)
| | | | | | | | | | | | - Michel Cogné
- CNRS, CRIBL, UMR 7276, Limoges, France.,Université de Limoges, CRIBL, UMR 7276, Limoges, France.,Institut Universitaire de France, Paris, France
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Pfirsch-Maisonnas S, Aloulou M, Xu T, Claver J, Kanamaru Y, Tiwari M, Launay P, Monteiro RC, Blank U. Inhibitory ITAM Signaling Traps Activating Receptors with the Phosphatase SHP-1 to Form Polarized "Inhibisome" Clusters. Sci Signal 2011; 4:ra24. [DOI: 10.1126/scisignal.2001309] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Ladygina N, Martin BR, Altman A. Dynamic palmitoylation and the role of DHHC proteins in T cell activation and anergy. Adv Immunol 2011; 109:1-44. [PMID: 21569911 DOI: 10.1016/b978-0-12-387664-5.00001-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Although protein S-palmitoylation was first characterized >30 years ago, and is implicated in the function, trafficking, and localization of many proteins, little is known about the regulation and physiological implications of this posttranslational modification. Palmitoylation of various signaling proteins required for TCR-induced T cell activation is also necessary for their proper function. Linker for activation of T cells (LAT) is an essential scaffolding protein involved in T cell development and activation, and we found that its palmitoylation is selectively impaired in anergic T cells. The recent discovery of the DHHC family of palmitoyl acyl transferases and the establishment of sensitive and quantitative proteomics-based methods for global analysis of the palmitoyl proteome led to significant progress in studying the biology and underlying mechanisms of cellular protein palmitoylation. We are using these approaches to explore the palmitoyl proteome in T lymphocytes and, specifically, the mechanistic basis for the impaired palmitoylation of LAT in anergic T cells. This chapter reviews the history of protein palmitoylation and its role in T cell activation, the DHHC family and new methodologies for global analysis of the palmitoyl proteome, and summarizes our recent work in this area. The new methodologies will accelerate the pace of research and provide a greatly improved mechanistic and molecular understanding of the complex process of protein palmitoylation and its regulation, and the substrate specificity of the novel DHHC family. Reversible protein palmitoylation will likely prove to be an important posttranslational mechanism that regulates cellular responses, similar to protein phosphorylation and ubiquitination.
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Affiliation(s)
- Nadejda Ladygina
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, California, USA
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Stanislas T, Bouyssie D, Rossignol M, Vesa S, Fromentin J, Morel J, Pichereaux C, Monsarrat B, Simon-Plas F. Quantitative proteomics reveals a dynamic association of proteins to detergent-resistant membranes upon elicitor signaling in tobacco. Mol Cell Proteomics 2009; 8:2186-98. [PMID: 19525550 PMCID: PMC2742443 DOI: 10.1074/mcp.m900090-mcp200] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 06/02/2009] [Indexed: 11/06/2022] Open
Abstract
A large body of evidence from the past decade supports the existence, in membrane from animal and yeast cells, of functional microdomains playing important roles in protein sorting, signal transduction, or infection by pathogens. In plants, as previously observed for animal microdomains, detergent-resistant fractions, enriched in sphingolipids and sterols, were isolated from plasma membrane. A characterization of their proteic content revealed their enrichment in proteins involved in signaling and response to biotic and abiotic stress and cell trafficking suggesting that these domains were likely to be involved in such physiological processes. In the present study, we used (14)N/(15)N metabolic labeling to compare, using a global quantitative proteomics approach, the content of tobacco detergent-resistant membranes extracted from cells treated or not with cryptogein, an elicitor of defense reaction. To analyze the data, we developed a software allowing an automatic quantification of the proteins identified. The results obtained indicate that, although the association to detergent-resistant membranes of most proteins remained unchanged upon cryptogein treatment, five proteins had their relative abundance modified. Four proteins related to cell trafficking (four dynamins) were less abundant in the detergent-resistant membrane fraction after cryptogein treatment, whereas one signaling protein (a 14-3-3 protein) was enriched. This analysis indicates that plant microdomains could, like their animal counterpart, play a role in the early signaling process underlying the setup of defense reaction. Furthermore proteins identified as differentially associated to tobacco detergent-resistant membranes after cryptogein challenge are involved in signaling and vesicular trafficking as already observed in similar studies performed in animal cells upon biological stimuli. This suggests that the ways by which the dynamic association of proteins to microdomains could participate in the regulation of the signaling process may be conserved between plant and animals.
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Affiliation(s)
- Thomas Stanislas
- From the ‡Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) Plante Microbe Environnement 1088/CNRS 5184/Université de Bourgogne, 17 Rue Sully, BP 86510 F-21000 Dijon, France
| | - David Bouyssie
- ¶Institut de Pharmacologie et de Biologie Structurale (IPBS), CNRS, 205 route de Narbonne, F-31077 Toulouse, France
- ‖IPBS, Université Paul Sabatier, Université de Toulouse, F-31077 Toulouse, France, and
| | - Michel Rossignol
- ¶Institut de Pharmacologie et de Biologie Structurale (IPBS), CNRS, 205 route de Narbonne, F-31077 Toulouse, France
- ‖IPBS, Université Paul Sabatier, Université de Toulouse, F-31077 Toulouse, France, and
- **IPBS, Institut Fédératif de Recherche 40 Plateforme Protéomique, 205 route de Narbonne, F-31077 Toulouse, France
| | - Simona Vesa
- From the ‡Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) Plante Microbe Environnement 1088/CNRS 5184/Université de Bourgogne, 17 Rue Sully, BP 86510 F-21000 Dijon, France
| | - Jérôme Fromentin
- From the ‡Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) Plante Microbe Environnement 1088/CNRS 5184/Université de Bourgogne, 17 Rue Sully, BP 86510 F-21000 Dijon, France
| | - Johanne Morel
- From the ‡Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) Plante Microbe Environnement 1088/CNRS 5184/Université de Bourgogne, 17 Rue Sully, BP 86510 F-21000 Dijon, France
| | - Carole Pichereaux
- ¶Institut de Pharmacologie et de Biologie Structurale (IPBS), CNRS, 205 route de Narbonne, F-31077 Toulouse, France
- ‖IPBS, Université Paul Sabatier, Université de Toulouse, F-31077 Toulouse, France, and
- **IPBS, Institut Fédératif de Recherche 40 Plateforme Protéomique, 205 route de Narbonne, F-31077 Toulouse, France
| | - Bernard Monsarrat
- ¶Institut de Pharmacologie et de Biologie Structurale (IPBS), CNRS, 205 route de Narbonne, F-31077 Toulouse, France
- ‖IPBS, Université Paul Sabatier, Université de Toulouse, F-31077 Toulouse, France, and
| | - Françoise Simon-Plas
- From the ‡Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) Plante Microbe Environnement 1088/CNRS 5184/Université de Bourgogne, 17 Rue Sully, BP 86510 F-21000 Dijon, France
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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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Alvarez FJ, Douglas LM, Konopka JB. Sterol-rich plasma membrane domains in fungi. EUKARYOTIC CELL 2007; 6:755-63. [PMID: 17369440 PMCID: PMC1899238 DOI: 10.1128/ec.00008-07] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Francisco J Alvarez
- Graduate Program in Genetics, State University of New York, Stony Brook, NY 11794-5222, USA
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Barouch-Bentov R, Altman A. Protein kinase C-theta (PKCtheta): new perspectives on its functions in T cell biology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 584:1-13. [PMID: 16802595 DOI: 10.1007/0-387-34132-3_1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Rina Barouch-Bentov
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, California 92121, USA
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Beauséjour Y, Tremblay MJ. Interaction between the cytoplasmic domain of ICAM-1 and Pr55Gag leads to acquisition of host ICAM-1 by human immunodeficiency virus type 1. J Virol 2004; 78:11916-25. [PMID: 15479832 PMCID: PMC523275 DOI: 10.1128/jvi.78.21.11916-11925.2004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have examined the molecular basis for the selective incorporation of the adhesion molecule ICAM-1 within human immunodeficiency virus type 1 (HIV-1). The process of ICAM-1 incorporation was investigated by using different ICAM-1 constructs in combination with virus capture and immunoprecipitation studies, Western blot and confocal microscopy analyses, and infectivity assays. Experiments conducted with viruses bearing a truncated version of ICAM-1 revealed that the cytoplasmic domain of ICAM-1 governs insertion of this adhesion molecule into HIV-1. Further experiments suggested that there is an association between ICAM-1 and the virus-encoded Pr55(Gag) polyprotein. This study represents the first demonstration that structural Gag polyproteins play a key role in the uptake of a host-derived cell surface by the virus entity. Taken together, our results indicate that interactions between viral and cellular proteins are responsible for the selective uptake of host ICAM-1 by HIV-1. This observation describes a new strategy by which HIV-1 can modulate its replicative cycle, considering that insertion of ICAM-1 within nascent virions has been shown to increase virus infectivity.
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Affiliation(s)
- Yannick Beauséjour
- Research Center in Infectious Diseases, RC709, CHUL Research Center, Faculty of Medicine, Laval University, Quebec, Canada
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10
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Abstract
The destiny of activated T cells is critical to the ultimate fate of immune response. After encountering antigen, naïve T cells receive signal 1 through the T-cell receptor (TCR)-major histocompatibility complex (MHC) plus antigenic peptide complex and signal 2 through "positive" costimulatory molecules leading to full activation. "Negative" T-cell costimulatory pathways, on the other hand, function to downregulate immune responses. The purpose of this article is to review the current state of knowledge and recent advances in our understanding of the functions of the positive and negative T-cell costimulatory pathways in alloimmune responses. Specifically, we discuss the functions of the CD28:B7 and the tumor necrosis factor receptor (TNFR):tumor necrosis factor (TNF) family of molecules in allograft rejection and tolerance. We address the following important questions: are T-cell costimulatory pathways merely redundant or do they provide distinct and unique functions? What are the important and unique interactions between the various pathways? And, what are the effects and mechanisms of targeting of these pathways in different types and patterns of allograft rejection and tolerance models?
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11
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Sancho R, Macho A, de La Vega L, Calzado MA, Fiebich BL, Appendino G, Muñoz E. Immunosuppressive activity of endovanilloids: N-arachidonoyl-dopamine inhibits activation of the NF-kappa B, NFAT, and activator protein 1 signaling pathways. THE JOURNAL OF IMMUNOLOGY 2004; 172:2341-51. [PMID: 14764703 DOI: 10.4049/jimmunol.172.4.2341] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Endogenous N-acyl dopamines such as N-arachidonoyldopamine (NADA) and N-oleoyldopamine have been recently identified as a new class of brain neurotransmitters sharing endocannabinoid and endovanilloid biological activities. As endocannabinoids show immunomodulatory activity, and T cells play a key role in the onset of several diseases that affect the CNS, we have evaluated the immunosuppressive activity of NADA and N-oleoyldopamine in human T cells, discovering that both compounds are potent inhibitors of early and late events in TCR-mediated T cell activation. Moreover, we found that NADA specifically inhibited both IL-2 and TNF-alpha gene transcription in stimulated Jurkat T cells. To further characterize the inhibitory mechanisms of NADA at the transcriptional level, we examined the DNA binding and transcriptional activities of NF-kappaB, NF-AT, and AP-1 transcription factors in Jurkat cells. We found that NADA inhibited NF-kappaB-dependent transcriptional activity without affecting either degradation of the cytoplasmic NF-kappaB inhibitory protein, IkappaBalpha, or DNA binding activity. However, phosphorylation of the p65/RelA subunit was clearly inhibited by NADA in stimulated cells. In addition, NADA inhibited both binding to DNA and the transcriptional activity of NF-AT and AP-1, as expected from the inhibition of NF-AT1 dephosphorylation and c-Jun N-terminal kinase activation in stimulated T cells. Finally, overexpression of a constitutively active form of calcineurin demonstrated that this phosphatase may represent one of the main targets of NADA. These findings provide new mechanistic insights into the anti-inflammatory activities of NADA and highlight their potential to design novel therapeutic strategies to manage inflammatory diseases.
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Affiliation(s)
- Rocío Sancho
- Departamento de Biología Celular, Fisiología e Inmunología, Universidad de Córdoba, Facultad de Medicina, Cordoba, Spain
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Favoreel HW, Mettenleiter TC, Nauwynck HJ. Copatching and lipid raft association of different viral glycoproteins expressed on the surfaces of pseudorabies virus-infected cells. J Virol 2004; 78:5279-87. [PMID: 15113909 PMCID: PMC400341 DOI: 10.1128/jvi.78.10.5279-5287.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudorabies virus (PRV) is a swine alphaherpesvirus that is closely related to human herpes simplex virus (HSV). Both PRV and HSV express a variety of viral envelope glycoproteins in the plasma membranes of infected cells. Here we show that at least four major PRV glycoproteins (gB, gC, gD, and gE) in the plasma membrane of infected swine kidney cells and monocytes seem to be linked, since monospecific antibody-induced patching of any one of these proteins results in copatching of the others. Further, for all four PRV glycoproteins, monospecific antibody-induced patches were enriched in GM1, a typical marker of lipid raft microdomains, but were excluded for transferrin receptor, a nonraft marker, suggesting that these viral proteins may associate with lipid rafts. However, only gB and, to a lesser extent, gE were found in lipid raft fractions by using detergent floatation assays, indicating that gC and gD do not show strong lipid raft association. Addition of methyl-beta-cyclodextrin (MCD), a cholesterol-depleting agent that is commonly used to disrupt lipid rafts, only slightly reduced copatching efficiency between the different viral proteins, indicating that other factors, perhaps tegument-glycoprotein interactions, may be important for the observed copatching events. On the other hand, MCD strongly reduced polarization of the antibody-induced viral glycoprotein patches to a cap structure, a gE-dependent process that has been described for specific PRV- and HSV-infected cells. Therefore, we hypothesize that efficient gE-mediated capping of antibody-antigen patches may require the lipid raft-associated signal transduction machinery.
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Affiliation(s)
- Herman W Favoreel
- Laboratory of Virology. Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
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Ge M, Gidwani A, Brown HA, Holowka D, Baird B, Freed JH. Ordered and disordered phases coexist in plasma membrane vesicles of RBL-2H3 mast cells. An ESR study. Biophys J 2003; 85:1278-88. [PMID: 12885671 PMCID: PMC1303245 DOI: 10.1016/s0006-3495(03)74563-9] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2002] [Accepted: 04/01/2003] [Indexed: 11/16/2022] Open
Abstract
Four chain spin labels and a spin-labeled cholestane were used to study the dynamic structure of plasma membrane vesicles (PMV) prepared from RBL-2H3 mast cells at temperatures ranging from 22 degrees C to 45 degrees C. Analysis shows that the spectra from most labels consist of two components. The abundant spectral components exhibit substantial ordering that is intermediate between that of a liquid-ordered (Lo) phase, and that of a liquid-crystalline (Lc) phase as represented by model membranes. Also, rotational diffusion rates of the spin labels are comparable to those in the Lo phase. In contrast, the ordering for the less abundant components is much lower. These results indicate that a Lo-like region or phase (the abundant component) and an Lc-like region or phase (the less abundant component) coexist in the PMV. In contrast, membranes reconstituted from extracted lipids exhibit the more ordered phase only. This suggests that membrane-associated proteins are important for the coexistence of Lo-like and Lc-like regions in the plasma membrane. In addition, binding of the myristoylated protein, ARF6 to PMV, leads to a new spectral component for a headgroup lipid spin label that indicates the formation of plasma membrane defects by this low molecular weight GTPase.
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Affiliation(s)
- Mingtao Ge
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA
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Venkatesan S, Rose JJ, Lodge R, Murphy PM, Foley JF. Distinct mechanisms of agonist-induced endocytosis for human chemokine receptors CCR5 and CXCR4. Mol Biol Cell 2003; 14:3305-24. [PMID: 12925765 PMCID: PMC181569 DOI: 10.1091/mbc.e02-11-0714] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Desensitization of the chemokine receptors, a large class of G protein-coupled receptors, is mediated in part by agonist-driven receptor endocytosis. However, the exact pathways have not been fully defined. Here we demonstrate that the rate of ligand-induced endocytosis of CCR5 in leukocytes and expression systems is significantly slower than that of CXCR4 and requires prolonged agonist treatment, suggesting that these two receptors use distinct mechanisms. We show that the C-terminal domain of CCR5 is the determinant of its slow endocytosis phenotype. When the C-tail of CXCR4 was exchanged for that of CCR5, the resulting CXCR4-CCR5 (X4-R5) chimera displayed a CCR5-like trafficking phenotype. We found that the palmitoylated cysteine residues in this domain anchor CCR5 to plasma membrane rafts. CXCR4 and a C-terminally truncated CCR5 mutant (CCR5-KRFX) lacking these cysteines are not raft associated and are endocytosed by a clathrin-dependent pathway. Genetic inhibition of clathrin-mediated endocytosis demonstrated that a significant fraction of ligand-occupied CCR5 trafficked by clathrin-independent routes into caveolin-containing vesicular structures. Thus, the palmitoylated C-tail of CCR5 is the major determinant of its raft association and endocytic itineraries, differentiating it from CXCR4 and other chemokine receptors. This novel feature of CCR5 may modulate its signaling potential and could explain its preferential use by HIV for person-to-person transmission of disease.
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Affiliation(s)
- Sundararajan Venkatesan
- Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Abstract
Shc is a prototype adapter protein that is expressed from the earliest stages of T-cell development. Shc becomes rapidly tyrosine phosphorylated after T-cell receptor (TCR) engagement. Expression of dominant negative forms of Shc in T-cell lines had also suggested a role for this adapter downstream of the TCR. However, until recently, the relative significance of Shc compared to several other adapters in T cells was unclear. Mice lacking Shc expression specifically in the T-cell lineage together with inducible expression of dominant negative Shc in transgenic mice have revealed an essential and nonredundant role for Shc in thymic T-cell development. Functional defects in a Jurkat T-cell line lacking Shc expression also suggest a role for Shc in mature T-cell functions. While the requirement of Shc in T-cell signaling is now established, precisely what signaling pathways downstream of Shc make this adapter unique are less clear. Although the Shc-mediated activation of the extracellular signal regulated kinase (Erk)/mitogen-activated protein kinase (MAPK) pathway could be one component, Shc likely signals to other pathways in T cells that are not yet discovered. A better molecular understanding of Shc function in the future could provide insights into how multiple adapters coordinate the various outcomes downstream of the TCR.
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Affiliation(s)
- Li Zhang
- Department of Microbiology and the Beirne B. Carter Center for Immunology Research, University of Virginia, Charlottesville, VA 22908, USA
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Hayes S, Chawla A, Corvera S. TGF beta receptor internalization into EEA1-enriched early endosomes: role in signaling to Smad2. J Cell Biol 2002; 158:1239-49. [PMID: 12356868 PMCID: PMC2173232 DOI: 10.1083/jcb.200204088] [Citation(s) in RCA: 239] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Transforming growth factor (TGF)beta is an important physiological regulator of cellular growth and differentiation. It activates a receptor threonine/serine kinase that phosphorylates the transcription factor Smad2, which then translocates into the nucleus to trigger specific transcriptional events. Here we show that activated type I and II TGF beta receptors internalize into endosomes containing the early endosomal protein EEA1. The extent of TGF beta-stimulated Smad2 phosphorylation, Smad2 nuclear translocation, and TGF beta-stimulated transcription correlated closely with the extent of internalization of the receptor. TGF beta signaling also requires SARA (Smad anchor for receptor activation), a 135-kD polypeptide that contains a FYVE Zn(++) finger motif. Here we show that SARA localizes to endosomes containing EEA1, and that disruption of this localization inhibits TGF beta-induced Smad2 nuclear translocation. These results indicate that traffic of the TGF beta receptor into the endosome enables TGF beta signaling, revealing a novel function for the endosome as a compartment specialized for the amplification of certain extracellular signals.
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Affiliation(s)
- Susan Hayes
- Program in Molecular Medicine and Interdisciplinary Graduate Program, University of Massachusetts Medical School, Worcester, MA 01605, USA
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17
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Abstract
As immunology developed into a discrete discipline, the principal experimental efforts were directed towards uncovering the molecular basis of the specificity exhibited by antibodies and the mechanism by which antigens induced their production. Less attention was given to how antibodies carry out some of their effector functions, although this subject presents an interesting protein-chemical and evolutionary problem; that is, how does a family of proteins that can bind a virtually infinite variety of ligands, many of which the species producing that protein has never encountered, reproducibly initiate an appropriate response? The experimental data persuasively suggested that aggregation of the antibody was a necessary and likely sufficient initiating event, but this only begged the question: how does aggregation induce a response? I used the IgE:mast cell system as a paradigm to investigate this subject. Data from our own group and from many others led to a molecular model that appears to explain how a cell 'senses' that antigen has reacted with the IgE. The model is directly applicable to one of the fundamental questions cited above, i.e. the mechanism by which antigens induce the production of antibodies. Although the model is conceptually simple, incorporating the actual molecular events into a quantitatively accurate scheme represents an enormous challenge.
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Affiliation(s)
- Henry Metzger
- Section on Chemical Immunology, Arthritis and Rheumatism Branch, NIAMS, NIH, Bethesda, MD 20892-1820, USA.
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