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Chouinard FC, Davis L, Gilbert C, Bourgoin SG. Functional Role of AGAP2/PIKE-A in Fcγ Receptor-Mediated Phagocytosis. Cells 2022; 12:cells12010072. [PMID: 36611866 PMCID: PMC9818964 DOI: 10.3390/cells12010072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
In phagocytes, cytoskeletal and membrane remodeling is finely regulated at the phagocytic cup. Various smaFll G proteins, including those of the Arf family, control these dynamic processes. Human neutrophils express AGAP2, an Arf GTPase activating protein (ArfGAP) that regulates endosomal trafficking and focal adhesion remodeling. We first examined the impact of AGAP2 on phagocytosis in CHO cells stably expressing the FcγRIIA receptor (CHO-IIA). In unstimulated CHO-IIA cells, AGAP2 only partially co-localized with cytoskeletal elements and intracellular compartments. In CHO-IIA cells, AGAP2 transiently accumulated at actin-rich phagocytic cups and increased Fcγ receptor-mediated phagocytosis. Enhanced phagocytosis was not dependent on the N-terminal GTP-binding protein-like (GLD) domain of AGAP2. AGAP2 deleted of its GTPase-activating protein (GAP) domain was not recruited to phagocytic cups and did not enhance the engulfment of IgG-opsonized beads. However, the GAP-deficient [R618K]AGAP2 transiently localized at the phagocytic cups and enhanced phagocytosis. In PLB-985 cells differentiated towards a neutrophil-like phenotype, silencing of AGAP2 reduced phagocytosis of opsonized zymosan. In human neutrophils, opsonized zymosan or monosodium urate crystals induced AGAP2 phosphorylation. The data indicate that particulate agonists induce AGAP2 phosphorylation in neutrophils. This study highlights the role of AGAP2 and its GAP domain but not GAP activity in FcγR-dependent uptake of opsonized particles.
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Affiliation(s)
- François C. Chouinard
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
| | - Lynn Davis
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
| | - Caroline Gilbert
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
- Département de Microbiologie-Infectiologie et D’immunologie, Université Laval, Québec City, QC G1V 0A6, Canada
| | - Sylvain G. Bourgoin
- Centre de Recherche du CHU de Québec—Université Laval, Québec City, QC G1V 4G2, Canada
- Département de Microbiologie-Infectiologie et D’immunologie, Université Laval, Québec City, QC G1V 0A6, Canada
- Centre ARThrite de L’université Laval, Québec City, QC G1V 4G2, Canada
- Correspondence:
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Abstract
Phagocytosis refers to the active process that allows cells to take up large particulate material upon binding to surface receptors. The discovery of phagocytosis in 1883 by Elie Metchnikoff, leading to the concept that specialized cells are implicated in the defense against microbes, was one of the starting points of the field of immunology. After more than a century of research, phagocytosis is now appreciated to be a widely used process that enables the cellular uptake of a remarkable variety of particles, including bacteria, fungi, parasites, viruses, dead cells, and assorted debris and solid materials. Uptake of foreign particles is performed almost exclusively by specialized myeloid cells, commonly termed "professional phagocytes": neutrophils, monocytes, macrophages, and dendritic cells. Phagocytosis of microbes not only stops or at least restricts the spread of infection but also plays an important role in regulating the innate and adaptive immune responses. Activation of the myeloid cells upon phagocytosis leads to the secretion of cytokines and chemokines that convey signals to a variety of immune cells. Moreover, foreign antigens generated by the degradation of microbes following phagocytosis are loaded onto the major histocompatibility complex for presentation to specific T lymphocytes. However, phagocytosis is not restricted to professional myeloid phagocytes; an expanding diversity of cell types appear capable of engulfing apoptotic bodies and debris, playing a critical role in tissue remodeling and in the clearance of billions of effete cells every day.
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Phagocytosis: A Fundamental Process in Immunity. BIOMED RESEARCH INTERNATIONAL 2017; 2017:9042851. [PMID: 28691037 PMCID: PMC5485277 DOI: 10.1155/2017/9042851] [Citation(s) in RCA: 289] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/18/2017] [Indexed: 01/12/2023]
Abstract
One hundred years have passed since the death of Élie Metchnikoff (1845-1916). He was the first to observe the uptake of particles by cells and realized the importance of this process for the host response to injury and infection. He also was a strong advocate of the role of phagocytosis in cellular immunity, and with this he gave us the basis for our modern understanding of inflammation and the innate and acquired immune responses. Phagocytosis is an elegant but complex process for the ingestion and elimination of pathogens, but it is also important for the elimination of apoptotic cells and hence fundamental for tissue homeostasis. Phagocytosis can be divided into four main steps: (i) recognition of the target particle, (ii) signaling to activate the internalization machinery, (iii) phagosome formation, and (iv) phagolysosome maturation. In recent years, the use of new tools of molecular biology and microscopy has provided new insights into the cellular mechanisms of phagocytosis. In this review, we present a general view of our current knowledge on phagocytosis. We emphasize novel molecular findings, particularly on phagosome formation and maturation, and discuss aspects that remain incompletely understood.
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Jaumouillé V, Farkash Y, Jaqaman K, Das R, Lowell CA, Grinstein S. Actin cytoskeleton reorganization by Syk regulates Fcγ receptor responsiveness by increasing its lateral mobility and clustering. Dev Cell 2014; 29:534-546. [PMID: 24914558 DOI: 10.1016/j.devcel.2014.04.031] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 02/25/2014] [Accepted: 04/27/2014] [Indexed: 12/18/2022]
Abstract
Clustering of immunoreceptors upon association with multivalent ligands triggers important responses including phagocytosis, secretion of cytokines, and production of immunoglobulins. We applied single-molecule detection and tracking methods to study the factors that control the mobility and clustering of phagocytic Fcγ receptors (FcγR). While the receptors exist as monomers in resting macrophages, two distinct populations were discernible based on their mobility: some diffuse by apparent free motion, while others are confined within submicron boundaries that reduce the frequency of spontaneous collisions. Src-family and Syk kinases determine the structure of the actin cytoskeleton, which is fenestrated, accounting for the heterogeneous diffusion of the FcγR. Stimulation of these kinases during phagocytosis induces reorganization of the cytoskeleton both locally and distally in a manner that alters receptor mobility and clustering, generating a feedback loop that facilitates engagement of FcγR at the tip of pseudopods, directing the progression of phagocytosis.
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Affiliation(s)
- Valentin Jaumouillé
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G1X8, Canada
| | - Yoav Farkash
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G1X8, Canada
| | - Khuloud Jaqaman
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA
| | - Raibatak Das
- Department of Integrative Biology, University of Colorado Denver, Denver, CO 80204, USA
| | - Clifford A Lowell
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94143-0100, USA
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G1X8, Canada; Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, 209 Victoria Street, Toronto, ON M5C 1N8, Canada.
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Rollet-Labelle E, Vaillancourt M, Marois L, Newkirk MM, Poubelle PE, Naccache PH. Cross-linking of IgGs bound on circulating neutrophils leads to an activation of endothelial cells: possible role of rheumatoid factors in rheumatoid arthritis-associated vascular dysfunction. J Inflamm (Lond) 2013; 10:27. [PMID: 23902799 PMCID: PMC3734015 DOI: 10.1186/1476-9255-10-27] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 07/25/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rheumatoid arthritis is characterized by the presence of circulating auto-antibodies, including rheumatoid factors, which recognize the Fc portion of IgGs. The neutrophil is the most abundant circulating leukocyte and it expresses high levels of FcγRs on its surface. The aim of the present study was to examine the capacity of circulating human neutrophils to be activated by rheumatoid factors and the consequences of these events on endothelium. METHODS Neutrophil-bound IgGs were cross-linked with anti-human IgGs to mimick the presence of circulating rheumatoid factors and FcγRs-dependent signalling events and functions were examined. The IgG and IgM composition of rheumatoid factors isolated from the serum of RA patients was characterized. Adhesion of neutrophils to endothelial cells was quantified in response to the addition of rheumatoid factors. RESULTS Cross-linking of IgGs bound on neutrophils leads to FcγRs-dependent tyrosine phosphorylation, mobilisation of intracellular calcium and the extracellular release of superoxide anions and lysozyme. Incubation of endothelial cells with the supernatant of activated neutrophils increases ICAM-1 expression and IL-8 production by endothelial cells. Finally, rheumatoid factors enhance neutrophil adhesion to endothelial cells. CONCLUSIONS Our results show that activation of neutrophils' FcγRs by rheumatoid factors could participate in rheumatoid arthritis-associated vascular damage.
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Affiliation(s)
- Emmanuelle Rollet-Labelle
- Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Centre de recherche en rhumatologie et immunologie, Centre de recherche du CHU de Québec, Université Laval, Québec, QC, Canada
| | - Myriam Vaillancourt
- Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Centre de recherche en rhumatologie et immunologie, Centre de recherche du CHU de Québec, Université Laval, Québec, QC, Canada
| | - Louis Marois
- Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Centre de recherche en rhumatologie et immunologie, Centre de recherche du CHU de Québec, Université Laval, Québec, QC, Canada
| | - Marianna M Newkirk
- Department of Medicine, Division of Rheumatology, Research Institute of McGill University Health Centre, McGill University, Montreal, QC, Canada
| | - Patrice E Poubelle
- Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Faculté de médecine, Université Laval, Québec, QC, Canada
| | - Paul H Naccache
- Départements de Microbiologie-Infectiologie et Immunologie et de Médecine, Centre de recherche en rhumatologie et immunologie, Centre de recherche du CHU de Québec, Université Laval, Québec, QC, Canada
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Pál L, Árnyas EM, Tóth B, Ádám B, Rácz G, Ádány R, McKee M, Szűcs S. Aliphatic alcohol contaminants of illegally produced spirits inhibit phagocytosis by human granulocytes. Immunopharmacol Immunotoxicol 2013; 35:251-6. [DOI: 10.3109/08923973.2012.759962] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Antibody-aided clearance of extracellular α-synuclein prevents cell-to-cell aggregate transmission. J Neurosci 2012; 32:13454-69. [PMID: 23015436 DOI: 10.1523/jneurosci.1292-12.2012] [Citation(s) in RCA: 263] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Abnormal deposition and intercellular propagation of α-synuclein plays a central role in the pathogenesis of disorders such as Parkinson's Disease (PD) and dementia with Lewy bodies (DLB). Previous studies demonstrated that immunization against α-synuclein resulted in reduced α-synuclein accumulation and synaptic loss in a transgenic (tg) mouse model, highlighting the potential for immunotherapy. However, the mechanism by which immunization prevents synucleinopathy-associated deficits remains unknown. Here, we show that antibodies against α-synuclein specifically target and aid in clearance of extracellular α-synuclein proteins by microglia, thereby preventing their actions on neighboring cells. Antibody-assisted clearance occurs mainly in microglia through the Fcγ receptor, and not in neuronal cells or astrocytes. Stereotaxic administration of antibody into the brains of α-synuclein tg mice prevented neuron-to-astroglia transmission of α-synuclein and led to increased localization of α-synuclein and the antibody in microglia. Furthermore, passive immunization with α-synuclein antibody reduced neuronal and glial accumulation of α-synuclein and ameliorated neurodegeneration and behavioral deficits associated with α-synuclein overexpression. These findings provide an underlying mechanistic basis for immunotherapy for PD/DLB and suggest extracellular forms of α-synuclein as potential therapeutic targets.
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Halbwachs L, Lesavre P. Endothelium-neutrophil interactions in ANCA-associated diseases. J Am Soc Nephrol 2012; 23:1449-61. [PMID: 22942199 DOI: 10.1681/asn.2012020119] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The two salient features of ANCA-associated vasculitis (AAV) are the restricted microvessel localization and the mechanism of inflammatory damage, independent of vascular immune deposits. The microvessel localization of the disease is due to the ANCA antigen accessibility, which is restricted to the membrane of neutrophils engaged in β2-integrin-mediated adhesion, while these antigens are cytoplasmic and inaccessible in resting neutrophils. The inflammatory vascular damage is the consequence of maximal proinflammatory responses of neutrophils, which face cumulative stimulations by TNF-α, β2-integrin engagement, C5a, and ANCA by the FcγRII receptor. This results in the premature intravascular explosive release by adherent neutrophils of all of their available weapons, normally designed to kill IgG-opsonized bacteria after migration in infected tissues.
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Affiliation(s)
- Lise Halbwachs
- Institut National de la Santé et de la Recherche Medicale INSERM U845, Université Paris Descartes, Sorbonne Paris Cité, France
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Tada M, Ishii-Watabe A, Maekawa K, Fukushima-Uesaka H, Kurose K, Suzuki T, Kaniwa N, Sawada JI, Kawasaki N, Nakajima TE, Kato K, Yamada Y, Shimada Y, Yoshida T, Ura T, Saito M, Muro K, Doi T, Fuse N, Yoshino T, Ohtsu A, Saijo N, Okuda H, Hamaguchi T, Saito Y, Matsumura Y. Genetic polymorphisms of FCGR2A encoding Fcγ receptor IIa in a Japanese population and functional analysis of the L273P variant. Immunogenetics 2012; 64:869-77. [DOI: 10.1007/s00251-012-0646-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 08/06/2012] [Indexed: 01/21/2023]
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Filipp D, Ballek O, Manning J. Lck, Membrane Microdomains, and TCR Triggering Machinery: Defining the New Rules of Engagement. Front Immunol 2012; 3:155. [PMID: 22701458 PMCID: PMC3372939 DOI: 10.3389/fimmu.2012.00155] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 05/25/2012] [Indexed: 11/21/2022] Open
Abstract
In spite of a comprehensive understanding of the schematics of T cell receptor (TCR) signaling, the mechanisms regulating compartmentalization of signaling molecules, their transient interactions, and rearrangement of membrane structures initiated upon TCR engagement remain an outstanding problem. These gaps in our knowledge are exemplified by recent data demonstrating that TCR triggering is largely dependent on a preactivated pool of Lck concentrated in T cells in a specific type of membrane microdomains. Our current model posits that in resting T cells all critical components of TCR triggering machinery including TCR/CD3, Lck, Fyn, CD45, PAG, and LAT are associated with distinct types of lipid-based microdomains which represent the smallest structural and functional units of membrane confinement able to negatively control enzymatic activities and substrate availability that is required for the initiation of TCR signaling. In addition, the microdomains based segregation spatially limits the interaction of components of TCR triggering machinery prior to the onset of TCR signaling and allows their rapid communication and signal amplification after TCR engagement, via the process of their coalescence. Microdomains mediated compartmentalization thus represents an essential membrane organizing principle in resting T cells. The integration of these structural and functional aspects of signaling into a unified model of TCR triggering will require a deeper understanding of membrane biology, novel interdisciplinary approaches and the generation of specific reagents. We believe that the fully integrated model of TCR signaling must be based on membrane structural network which provides a proper environment for regulatory processes controlling TCR triggering.
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Affiliation(s)
- Dominik Filipp
- Laboratory of Immunobiology, Institute of Molecular Genetics AS CR Prague, Czech Republic
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Flannagan RS, Jaumouillé V, Grinstein S. The Cell Biology of Phagocytosis. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2012; 7:61-98. [PMID: 21910624 DOI: 10.1146/annurev-pathol-011811-132445] [Citation(s) in RCA: 652] [Impact Index Per Article: 54.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ronald S. Flannagan
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada;
| | - Valentin Jaumouillé
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada;
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada;
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Ballek O, Broučková A, Manning J, Filipp D. A specific type of membrane microdomains is involved in the maintenance and translocation of kinase active Lck to lipid rafts. Immunol Lett 2012; 142:64-74. [PMID: 22281390 DOI: 10.1016/j.imlet.2012.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 01/10/2012] [Accepted: 01/10/2012] [Indexed: 10/14/2022]
Abstract
Lck is the principal signal-generating tyrosine kinase of the T cell activation mechanism. We have previously demonstrated that induced Lck activation outside of lipid rafts (LR) results in the rapid translocation of a fraction of Lck to LR. While this translocation predicates the subsequent production of IL-2, the mechanism underpinning this process is unknown. Here, we describe the main attributes of this translocating pool of Lck. Using fractionation of Brij58 lysates, derived from primary naive non-activated CD4(+) T cells, we show that a significant portion of Lck is associated with high molecular weight complexes representing a special type of detergent-resistant membranes (DRMs) of relatively high density and sensitivity to laurylmaltoside, thus called heavy DRMs. TcR/CD4 coaggregation-mediated activation resulted in the redistribution of more than 50% of heavy DRM-associated Lck to LR in a microtubular network-dependent fashion. Remarkably, in non-activated CD4(+) T-cells, only heavy DRM-associated Lck is phosphorylated on its activatory tyrosine 394 and this pool of Lck is found to be membrane confined with CD45 phosphatase. These data are the first to illustrate a lipid microdomain-based mechanism concentrating the preactivated pool of cellular Lck and supporting its high stoichiometry of colocalization with CD45 in CD4(+) T cells. They also provide a new structural framework to assess the mechanism underpinning the compartmentalization of critical signaling elements and regulation of spatio-temporal delivery of Lck function during the T cell proximal signaling.
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Affiliation(s)
- Ondřej Ballek
- Laboratory of Immunobiology, Institute of Molecular Genetics AS CR, Prague, Czech Republic
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Marois L, Vaillancourt M, Paré G, Gagné V, Fernandes MJG, Rollet-Labelle E, Naccache PH. CIN85 modulates the down-regulation of Fc gammaRIIa expression and function by c-Cbl in a PKC-dependent manner in human neutrophils. J Biol Chem 2011; 286:15073-84. [PMID: 21372129 PMCID: PMC3083175 DOI: 10.1074/jbc.m110.213660] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/21/2011] [Indexed: 01/04/2023] Open
Abstract
We previously described a non-classical mechanism that arrests FcγRIIa signaling in human neutrophils once engaged by immune complexes or opsonized pathogens. The engagement of FcγRIIa leads to its ubiquitination by the ubiquitin ligase c-Cbl and degradation by the proteasome. Herein, we further examined some of the events regulating this novel pathway. The adaptor protein CIN85 was described in other systems to be involved in the regulation of the c-Cbl-dependent pathway. We found that CIN85 is expressed in human neutrophils and that it translocates like c-Cbl from the cytosol to the plasma membrane following receptor cross-linking. CIN85 was also recruited to the same subset of high density detergent-resistant membrane fractions in which stimulated FcγRIIa partitioned with c-Cbl. The integrity of these microdomains is essential to the FcγRIIa degradation process because the cholesterol-depleting agent methyl-β-cyclodextrin inhibits this event. Silencing the expression of CIN85 by siRNA in dibutyryl cyclic AMP-differentiated PLB 985 cells prevented FcγRIIa degradation and increased IgG-mediated phagocytosis. Confocal microscopy revealed that the presence of CIN85 is essential to the proper sorting of FcγRIIa during endocytosis. We also provide direct evidence that CIN85 is a substrate of serine/threonine kinase PKCs. Classical PKCs positively regulate FcγRIIa ubiquitination and degradation because these events were inhibited by Gö6976, a classical PKC inhibitor. We conclude that the ubiquitination and degradation of stimulated FcγRIIa mediated by c-Cbl are positively regulated by the adaptor protein CIN85 in a PKC-dependent manner and that these events contribute to the termination of FcγRIIa signaling.
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Affiliation(s)
- Louis Marois
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Myriam Vaillancourt
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Guillaume Paré
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Valérie Gagné
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Maria J. G. Fernandes
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Emmanuelle Rollet-Labelle
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
| | - Paul H. Naccache
- From the Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Département de Microbiologie-Infectiologie et Immunologie, Faculté de Médecine, Université Laval, Québec, Québec G1V 4G2, Canada
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Faugaret D, Chouinard FC, Harbour D, El azreq MA, Bourgoin SG. An essential role for phospholipase D in the recruitment of vesicle amine transport protein-1 to membranes in human neutrophils. Biochem Pharmacol 2011; 81:144-56. [PMID: 20858461 DOI: 10.1016/j.bcp.2010.09.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 09/08/2010] [Accepted: 09/10/2010] [Indexed: 12/13/2022]
Abstract
Although phosphatidic acid (PA) regulates a wide variety of physiological processes, its targets remain poorly characterized in human neutrophils. By co-sedimentation with PA-containing vesicles we identified several PA-binding proteins including vesicle amine transport protein-1 (VAT-1), Annexin A3 (ANXA3), Rac2, Cdc42 and RhoG in neutrophil cytosol. Except for ANXA3, protein binding to PA-containing liposomes was calcium-independent. Cdc42 and RhoG preferentially interacted with PA whereas VAT-1 bound to PA or phosphatidylserine with the same affinity. VAT-1 translocated to neutrophil membranes upon N-formyl-methionyl-leucyl-phenylalanine (fMLF) stimulation. Inhibition of fMLF-induced PLD activity with the Src kinase inhibitor PP2, the selective inhibitor of PLD FIPI, or of PA formation with primary alcohols reduced VAT-1 translocation. In contrast, inhibition of PA hydrolysis with propranolol enhanced fMLF-mediated VAT-1 recruitment to membranes. PMA also redistributed VAT-1 to membranes in a PKC- and PLD-dependent manner. Though fMLF and PMA increased VAT-1 phosphorylation, different kinases appear to be involved. Cell fractionation revealed that a pool of VAT-1 was co-localized with primary, secondary and tertiary granules and plasma membrane markers in resting neutrophils. Stimulation with fMLF enhanced VAT-1 co-localization with CD32a, a plasma membrane marker. Confocal microscopy revealed that VAT-1 decorates granular structures at the cell periphery and double labeling with VAT-1/lactoferrin antibodies showed a partial co-localization with secondary granules in control and fMLF-stimulated cells. Characterization of these putative PA-binding proteins constitutes another step forward for a better understanding of the role of PLD-derived PA in neutrophil physiology.
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Affiliation(s)
- Delphine Faugaret
- Centre de Recherche en Rhumatologie et Immunologie, Centre de recherche du CHUQ-CHUL et Faculté de Médecine de l'Université Laval, 2705 Boulevard Laurier, local T1-49, Québec, QC, G1V 4G2, Canada.
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Marois L, Paré G, Vaillancourt M, Rollet-Labelle E, Naccache PH. Fc gammaRIIIb triggers raft-dependent calcium influx in IgG-mediated responses in human neutrophils. J Biol Chem 2010; 286:3509-19. [PMID: 21123174 DOI: 10.1074/jbc.m110.169516] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human neutrophils constitutively express a unique combination of FcγRs, namely FcγRIIa and FcγRIIIb. Numerous lines of evidence support the concept that these FcγRs generate only partially characterized intracellular signals. However, despite the fact that both receptors are likely to be engaged simultaneously in a physiological setting, no recent publications have investigated the distinct, although partially convergent, results of their joint activation in IgG-dependent responses. To examine the significance of the co-expression of FcγRIIa and FcγRIIIb on human neutrophils, we analyzed the neutrophil responses to stimuli that engage these FcγRs, namely the phagocytosis of human IgG-opsonized zymosan and the responses to heat-aggregated IgGs. Blocking antibodies to either FcγR significantly decreased the phagocytic index and the stimulated production of superoxide anions. Both receptors are required for optimal IgG-dependent responses by human neutrophils. On the other hand, only blocking antibodies to FcγRIIIb, but not to FcγRIIa, inhibited the mobilization of calcium in response to heat-aggregated IgGs. Furthermore, phagocytosis of IgG-opsonized zymosan by human neutrophils required an extracellular influx of calcium that was blocked only by antibodies against FcγRIIIb. We also observed that this calcium influx as well as the IgG-dependent phagocytosis were dependent on the integrity of the plasma membrane detergent-resistant microdomains to which both isoforms were recruited following stimulation by heat-aggregated IgGs. These data clarify the mechanisms that regulate the FcγRs constitutively expressed on human neutrophils, describe a specific contribution of FcγRIIIb at the level of the mobilization of calcium, and provide evidence for a crucial role of detergent-resistant microdomains in this process.
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Affiliation(s)
- Louis Marois
- Centre de Recherche du Centre Hospitalier Universitaire de Québec, Department of Microbiology-Infectiology and Immunology, Faculty of Medicine, Laval University, Québec City, Québec G1V 4G2, Canada
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Florey O, Durgan J, Muller W. Phosphorylation of leukocyte PECAM and its association with detergent-resistant membranes regulate transendothelial migration. THE JOURNAL OF IMMUNOLOGY 2010; 185:1878-86. [PMID: 20581150 DOI: 10.4049/jimmunol.1001305] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Leukocyte migration across the endothelial lining is a critical step in the body's response to infection and inflammation. The homophilic interaction between endothelial PECAM and leukocyte PECAM is essential for this process. The molecular events that are triggered in the endothelial cell by PECAM engagement have been well characterized; however, the function of leukocyte PECAM remains to be elucidated. To study this, we first blocked leukocyte transmigration using anti-PECAM Ab and then specifically activated leukocyte PECAM. This was sufficient to overcome the block and promote transmigration, suggesting an active signaling role for leukocyte PECAM. Consistent with this, we found that ligation of leukocyte PECAM induces phosphorylation of two tyrosine residues on its cytoplasmic tail. By performing RNA interference-rescue experiments, we demonstrate that these phosphorylation events are indispensable for transendothelial migration. Finally, we show that leukocyte PECAM translocates to a detergent-resistant membrane (DRM) during transmigration. PECAM localized in DRMs displays reduced phosphorylation and does not support transmigration. Together, these data support a model whereby engagement of leukocyte PECAM induces its transient tyrosine phosphorylation and induction of downstream signals that drive transmigration. These signals are then downregulated following PECAM translocation to DRMs.
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Affiliation(s)
- Oliver Florey
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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18
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Otáhal P, Angelisová P, Hrdinka M, Brdicka T, Novák P, Drbal K, Horejsí V. A new type of membrane raft-like microdomains and their possible involvement in TCR signaling. THE JOURNAL OF IMMUNOLOGY 2010; 184:3689-96. [PMID: 20207997 DOI: 10.4049/jimmunol.0902075] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Membrane rafts and signaling molecules associated with them are thought to play important roles in immunoreceptor signaling. Rafts differ in their lipid and protein compositions from the rest of the membrane and are relatively resistant to solubilization by Triton X-100 or similar detergents, producing buoyant, detergent-resistant membranes (DRMs) that can be isolated by density gradient ultracentrifugation. One of the key signaling molecules present in T cell DRMs is the transmembrane adaptor protein LAT (linker for activation of T cells). In contrast to previous results, a recent study demonstrated that a LAT construct not present in the buoyant DRMs is fully able to support TCR signaling and development of T cells in vivo. This finding caused doubts about the real physiological role of rafts in TCR signaling. In this study, we demonstrate that these results can be explained by the existence of a novel type of membrane raft-like microdomains, producing upon detergent solubilization "heavy DRMs" containing a number of membrane molecules. At a moderate level of expression, LAT supported TCR signaling more efficiently than constructs targeted to the microdomains producing heavy DRMs or to nonraft membrane. We suggest that different types of membrane microdomains provide environments regulating the functional efficiencies of signaling molecules present therein.
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Affiliation(s)
- Pavel Otáhal
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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19
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Puerta-Guardo H, Mosso C, Medina F, Liprandi F, Ludert JE, del Angel RM. Antibody-dependent enhancement of dengue virus infection in U937 cells requires cholesterol-rich membrane microdomains. J Gen Virol 2009; 91:394-403. [DOI: 10.1099/vir.0.015420-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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FcgammaRI ligation leads to a complex with BLT1 in lipid rafts that enhances rat lung macrophage antimicrobial functions. Blood 2009; 114:3316-24. [PMID: 19657115 PMCID: PMC2759654 DOI: 10.1182/blood-2009-01-199919] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Leukotriene (LT) B(4) is generated in response to engagement of the Fc gamma receptor (Fc gamma R) and potently contributes to Fc gamma R-mediated antimicrobial functions in pulmonary alveolar macrophages. In this study, we report that the LTB(4) receptor leukotriene B(4) receptor 1 (BLT1) redistributes from nonlipid raft (LR) to LR membrane microdomains upon immunoglobulin G-red blood cell, but not LTB(4), challenge. Cholesterol depletion to disrupt LRs abolished LTB(4)-induced enhancement of phagocytosis, microbicidal activity, and signaling. The dependence on LR integrity for BLT1 signaling correlated with formation of a complex consisting of BLT1, its primary coupled G protein G alpha i3, Src kinase, and Fc gamma RI within LRs. This association was dependent on Src-mediated phosphorylation of BLT1. These data identify a novel form of regulation in which engagement of a macrophage immunoreceptor recruits a stimulatory G protein-coupled receptor into a LR microdomain with resultant enhanced antimicrobial signaling.
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Surface RANKL of Toll-like receptor 4-stimulated human neutrophils activates osteoclastic bone resorption. Blood 2009; 114:1633-44. [PMID: 19546479 DOI: 10.1182/blood-2008-09-178301] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Inflammatory bone loss in septic and inflammatory conditions is due to increased activity of osteoclasts that requires receptor activator of NF-kappa B-ligand (RANKL). Neutrophils are the predominant infiltrating cells in these conditions. Although disease severity is linked to neutrophils, their role in evolution of bony lesions is not clear. We show that lipopolysaccharide (LPS), a toll-like receptor 4 ligand, up-regulated the expression of membrane RANKL in human blood neutrophils and murine air pouch-derived neutrophils. LPS-activated human and murine neutrophils, cocultured with human monocyte-derived osteoclasts and RAW 264.7 cells, respectively, stimulated bone resorption. Transfection of PLB-985 neutrophil-like cells with RANKL antisense RNA reduced osteoclastogenesis. Synovial fluid neutrophils of patients with exacerbation of rheumatoid arthritis strongly expressed RANKL and activated osteoclastogenesis in coculture systems. Osteoprotegerin, the RANKL decoy receptor, suppressed osteoclast activation by neutrophils from these different sources. Moreover, direct cell-cell contact between neutrophils and osteoclasts was visualized by confocal laser microscopy. Activation of neutrophil membrane-bound RANKL was linked to tyrosine phosphorylation of Src-homology domain-containing cytosolic phosphatase 1 with concomitant down-regulation of cytokine production. The demonstration of these novel functions of neutrophils highlights their potential role in osteoimmunology and in therapeutics of inflammatory bone disease.
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Bournazos S, Hart SP, Chamberlain LH, Glennie MJ, Dransfield I. Association of FcgammaRIIa (CD32a) with lipid rafts regulates ligand binding activity. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2009; 182:8026-36. [PMID: 19494328 DOI: 10.4049/jimmunol.0900107] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Binding of Igs to myeloid cells via FcR is a key event in the control of innate and acquired immunity. FcgammaRIIa (CD32a) is a receptor for multivalent IgG expressed predominantly by myeloid cells, and its association with microdomains rich in cholesterol and sphingolipids, termed as lipid rafts, has been reported to be essential for efficient signaling. However, for many myeloid cell types, ligand binding to CD32a is suppressed by as yet undefined mechanisms. In this study, we have examined the role of CD32a-lipid raft interactions in the regulation of IgG binding to CD32a. Disruption of lipid raft structure following depletion or sequestration of membrane cholesterol greatly inhibited CD32a-mediated IgG binding. Furthermore, specific CD32a mutants, which show reduced association with lipid rafts (A224S and C241A), displayed decreased levels of IgG binding compared with wild-type CD32a. In contrast, constitutively lipid raft-associated CD32a (GPI-anchored CD32a) exhibited increased capacity for IgG binding compared with the full-length transmembrane CD32a. Our findings clearly suggest a major role for lipid rafts in the regulation of IgG binding and, more specifically, that suppression of CD32a-mediated IgG binding in myeloid cells is achieved by receptor exclusion from lipid raft membrane microdomains.
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Affiliation(s)
- Stylianos Bournazos
- University of Edinburgh/Medical Research Council Centre for Inflammation Research, Queen's Medical Research Institute, Edinburgh, UK
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23
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Marois L, Vaillancourt M, Marois S, Proulx S, Paré G, Rollet-Labelle E, Naccache PH. The ubiquitin ligase c-Cbl down-regulates FcgammaRIIa activation in human neutrophils. THE JOURNAL OF IMMUNOLOGY 2009; 182:2374-84. [PMID: 19201892 DOI: 10.4049/jimmunol.0801420] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Little is known about the mechanisms that arrest FcgammaRIIa signaling in human neutrophils once engaged by immune complexes or opsonized pathogens. In our previous studies, we observed a loss of immunoreactivity of Abs directed against FcgammaRIIa following its cross-linking. In this study, we report on the mechanisms involved in this event. A stimulated internalization of FcgammaRIIa leading to the down-regulation of its surface expression was observed by flow cytometry and confocal microscopy. Immunoprecipitation of the receptor showed that FcgammaRIIa is ubiquitinated after stimulation. MG132 and clasto-lactacystin beta-lactone inhibited the loss of immunoreactivity of FcgammaRIIa, suggesting that this receptor was down-regulated via the proteasomal pathway. The E3 ubiquitin ligase c-Cbl was found to translocate from the cytosol to the plasma membrane following receptor cross-linking. Furthermore, c-Cbl was recruited to the same subset of high-density, detergent-resistant membrane fractions as stimulated FcgammaRIIa itself. Silencing the expression of c-Cbl by small interfering RNA decreased FcgammaRIIa ubiquitination and prevented its degradation without affecting the internalisation process. It also prolonged the stimulation of the tyrosine phosphorylation response to the cross-linking of the receptor. We conclude that c-Cbl mediates the ubiquitination of stimulated FcgammaRIIa and thereby contributes to the termination of FcgammaRIIa signaling via its proteasomal degradation, thus leading to the down-regulation of neutrophil signalisation and function (phagocytosis) through this receptor.
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Affiliation(s)
- Louis Marois
- Centre de recherche en rhumatologie et immunologie, Centre de recherche du Centre hospitalier universitaire de Québec, Department of Medicine, Faculty of Medicine, Laval University, Quebec, Canada
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Pivot-Pajot C, Varoqueaux F, de Saint Basile G, Bourgoin SG. Munc13-4 Regulates Granule Secretion in Human Neutrophils. THE JOURNAL OF IMMUNOLOGY 2008; 180:6786-97. [DOI: 10.4049/jimmunol.180.10.6786] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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25
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Schneider B, Schueller C, Utermoehlen O, Haas A. Lipid Microdomain-Dependent Macropinocytosis Determines Compartmentation of Afipia felis. Traffic 2006; 8:226-40. [PMID: 17319800 DOI: 10.1111/j.1600-0854.2006.00525.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phagocytic compartments are specialized endocytic organelles and usually mature along the degradative pathway into phagolysosomes. The rare human pathogen Afipia felis localizes to a compartment that is different from canonical phagocytic compartments. Here, we present evidence that internalization of Afipia by macrophages and unusual phagosome development are considerably decreased by attachment of cholera toxin B subunit to macrophage ganglioside GM1 or by extraction or oxidation of plasma membrane cholesterol. Amiloride (an inhibitor of Na(+)/H(+) exchanger and macropinocytosis) strongly inhibited uptake of A. felis at a late step, i.e. the closure of macropinocytic structures rather than the production of membrane ruffles. Ultrastructural evidence showed that A. felis was taken up by macrophages via macropinocytosis. In contrast, A. felis opsonized with a monoclonal IgG antibody was ingested by a zipper-like mechanism, resulting in normal phagosome maturation. Hence, while the preferred path of A. felis uptake is dependent on the integrity of lipid microdomains and on macropinocytosis, and while this uptake leads to an unusual phagosome and to intracellular survival of A. felis, those bacteria that enter using Fcgamma receptors are delivered to a late endocytic compartment.
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Affiliation(s)
- Bianca Schneider
- Institute for Cell Biology, University of Bonn, Ulrich-Haberland-Strasse 61a, 53121 Bonn, Germany
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26
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Vaillancourt M, Levasseur S, Tremblay ML, Marois L, Rollet-Labelle E, Naccache PH. The Src Homology 2-Containing Inositol 5-Phosphatase 1 (SHIP1) is involved in CD32a signaling in human neutrophils. Cell Signal 2006; 18:2022-32. [PMID: 16682172 DOI: 10.1016/j.cellsig.2006.03.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 03/22/2006] [Accepted: 03/23/2006] [Indexed: 01/05/2023]
Abstract
Phosphatidylinositol(3,4,5)triphosphate (PtdIns(3,4,5)P(3)) plays important signaling roles in immune cells, particularly in the control of activating pathways and of survival. It is formed by a family of phosphatidylinositol 3'-kinases (PI3Ks) which phosphorylate PtdIns(4,5)P(2) in vivo. In human neutrophils, the levels of PtdIns(3,4,5)P(3) increase rapidly at the leading edge of locomoting cells and at the base of the phagocytic cup during FcgammaR-mediated particle ingestion. Even though these, and other, data indicate that PtdIns(3,4,5)P(3) is involved in the control of chemotaxis and phagocytosis in human neutrophils, the mechanisms that regulate its levels have yet to be fully elucidated in these cells. We evaluated the potential implication of SHIP1 and PTEN, two lipid phosphatases that utilize PtdIns(3,4,5)P(3) as substrate, in the signaling pathways called upon in response to CD32a cross-linking. We observed that the cross-linking of CD32a resulted in a transient accumulation of PtdIns(3,4,5)P(3). CD32a cross-linking also induced the tyrosine phosphorylation of SHIP1, its translocation to the plasma membrane and its co-immunoprecipitation with CD32a. CD32a cross-linking had no effect on the level of serine/threonine phosphorylation of PTEN and did not stimulate its translocation to the plasma membrane. PP2, a Src kinase inhibitor, inhibited the tyrosine phosphorylation of SHIP1 as well as its translocation to the plasma membrane. Wortmannin, a PI3K inhibitor, had no effect on either of these two indices of activation of SHIP1. Our results indicate that SHIP1 is involved, in a Src kinase-dependent manner, in the early signaling events observed upon the cross-linking of CD32a in human neutrophils.
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Affiliation(s)
- Myriam Vaillancourt
- Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUL, Room T1-49, 2705, Boulevard Laurier and Department of Medicine, Faculty of Medicine, Laval University, Sainte-Foy, QC, Canada
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27
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Solomkin JS, Robinson CT, Cave CM, Umanskiy K, Matlin K, Williams MA, Lentsch AB. FORMATION OF FOCAL ADHESION-LIKE STRUCTURES IN CIRCULATING HUMAN NEUTROPHILS AFTER SEVERE INJURY. Shock 2006; 25:440-5. [PMID: 16680007 DOI: 10.1097/01.shk.0000209559.77198.91] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Neutrophils play a key role in injury to the lung, kidney, liver, and gastrointestinal tract, often seen after major trauma. We evaluated the role of integrin-linked focal adhesions in the primed state, previously identified in peripheral blood neutrophils from severely injured patients. Immunoblot analysis of Triton-insoluble cell fractions revealed that total paxillin content was unchanged in comparison with that found in neutrophils from healthy volunteers, but phosphorylation of paxillin on tyrosine residue 118 was increased by more than 2-fold. Immunoprecipitation with antipaxillin and immunoblotting for proline-rich tyrosine kinase 2 (Pyk2) and for fgr showed significantly more colocalization. Densitometric analysis of total phosphotyrosine profiles also demonstrated significantly more in patient cells as compared with healthy cells. When allowed to adhere to fibronectin-coated plates, healthy and patient cells demonstrate a significant increase in tyrosine phosphorylation from that found in suspension-phase cells. Differential interference contrast microscopy of healthy neutrophils adherent to fibronectin matrices demonstrated rounded cells, without evidence of spreading; spreading was induced by addition of TNF-alpha. Patient neutrophils spread spontaneously, a response not further enhanced by TNF-alpha. Confocal imaging using anti-Pyk2 demonstrated aggregation of Pyk2 into punctate structures in patient but not in healthy cells. We conclude that neutrophils from severely injured patients are in a primed state, characterized by formation of focal adhesion-like structures. The identification of such structures in a clinical disease setting where they likely participate in unwanted consequences provides a novel area for study of regulation of neutrophil function.
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Affiliation(s)
- Joseph S Solomkin
- Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0558, USA.
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Fernandes MJG, Rollet-Labelle E, Paré G, Marois S, Tremblay ML, Teillaud JL, Naccache PH. CD16b associates with high-density, detergent-resistant membranes in human neutrophils. Biochem J 2006; 393:351-9. [PMID: 16171455 PMCID: PMC1383694 DOI: 10.1042/bj20050129] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
CD16b is unique in that it is the only Fc receptor linked to the plasma membrane by a GPI (glycosylphosphatidylinositol) anchor. GPI-anchored proteins often preferentially localize to DRMs (detergent-resistant membranes) that are rich in sphingolipids and cholesterol and play an important role in signal transduction. Even though the responses to CD16b engagement have been intensively investigated, the importance of DRM integrity for CD16b signalling has not been characterized in human neutrophils. We provide direct evidence that CD16b constitutively partitions with both low- and high-density DRMs. Moreover, upon CD16b engagement, a significant increase in the amount of the receptor is observed in high-density DRMs. Similarly to CD16b, CD11b also resides in low- and high-density DRMs. In contrast with CD16b, the partitioning of CD11b in DRMs does not change in response to CD16b engagement. We also provide evidence for the implication of Syk in CD16b signalling and its partitioning to DRMs in resting and activated PMNs (polymorphonuclear neutrophils). Additionally, DRM-disrupting agents, such as nystatin and methyl-beta-cyclodextrin, alter cellular responses to CD16b receptor ligation. Notably, a significant increase in the mobilization of intracellular Ca2+ and in tyrosine phosphorylation of intracellular substrates after CD16b engagement is observed. Altogether, the results of this study provide evidence that high-density DRMs play a role in CD16b signalling in human neutrophils.
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Affiliation(s)
- Maria J G Fernandes
- Department of Rheumatology and Immunology, CHUL Research Centre, Laval University, 2705 boulevarde Laurier, Sainte-Foy, Québec, Canada, G1V 4G2.
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Lam RS, Shaw AR, Duszyk M. Membrane cholesterol content modulates activation of BK channels in colonic epithelia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1667:241-8. [PMID: 15581861 DOI: 10.1016/j.bbamem.2004.11.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Revised: 11/03/2004] [Accepted: 11/09/2004] [Indexed: 10/26/2022]
Abstract
Changes in the level of membrane cholesterol regulate a variety of signaling processes including those mediated by acylated signaling molecules that localize to lipid rafts. Recently several types of ion channels have been shown to have cholesterol-dependent activity and to localize to lipid rafts. In this study, we have investigated the role of cholesterol in the regulation of ion transport in colonic epithelial cells. We observed that methyl-beta-cyclodextrin (MbetaCD), a cholesterol-sequestering molecule, activated transepithelial short circuit current (Isc), but only from the basolateral side. Similar results were obtained with a cholesterol-binding agent, filipin, and with the sphingomyelin-degrading enzyme, sphingomyelinase. Experiments with DeltaF508CFTR mutant mice indicated that raft disruption affected CFTR-mediated anion secretion, while pharmacological studies showed that this effect was due to activation of basolateral large conductance Ca2+-activated K+ (BK) channels. Sucrose density gradient centrifugation studies demonstrated that BK channels were normally present in the high-density fraction containing the detergent-insoluble cytoskeleton, and that following treatment with MbetaCD, BK channels redistributed into detergent-soluble fractions. Our evidence therefore implicates novel high-density cholesterol-enriched plasma membrane microdomains in the modulation of BK channel activation and anion secretion in colonic epithelia.
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Affiliation(s)
- Rebecca S Lam
- Department of Physiology, University of Alberta, 7-46 Medical Sciences Bldg., Edmonton, Alberta, Canada T6G 2H7
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