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Shahinuzzaman M, Khetan J, Barua D. A spatio-temporal model reveals self-limiting Fc ɛRI cross-linking by multivalent antigens. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180190. [PMID: 30839725 PMCID: PMC6170560 DOI: 10.1098/rsos.180190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 08/23/2018] [Indexed: 06/09/2023]
Abstract
Aggregation of cell surface receptor proteins by multivalent antigens is an essential early step for immune cell signalling. A number of experimental and modelling studies in the past have investigated multivalent ligand-mediated aggregation of IgE receptors (FcɛRI) in the plasma membrane of mast cells. However, understanding of the mechanisms of FcɛRI aggregation remains incomplete. Experimental reports indicate that FcɛRI forms relatively small and finite-sized clusters when stimulated by a multivalent ligand. By contrast, modelling studies have shown that receptor cross-linking by a trivalent ligand may lead to the formation of large receptor superaggregates that may potentially give rise to hyperactive cellular responses. In this work, we have developed a Brownian dynamics-based spatio-temporal model to analyse FcɛRI aggregation by a trivalent antigen. Unlike the existing models, which implemented non-spatial simulation approaches, our model explicitly accounts for the coarse-grained site-specific features of the multivalent species (molecules and complexes). The model incorporates membrane diffusion, steric collisions and sub-nanometre-scale site-specific interaction of the time-evolving species of arbitrary structures. Using the model, we investigated temporal evolution of the species and their diffusivities. Consistent with a recent experimental report, our model predicted sharp decay in species mobility in the plasma membrane in response receptor cross-linking by a multivalent antigen. We show that, due to such decay in the species mobility, post-stimulation receptor aggregation may become self-limiting. Our analysis reveals a potential regulatory mechanism suppressing hyperactivation of immune cells in response to multivalent antigens.
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Affiliation(s)
| | | | - Dipak Barua
- Author for correspondence: Dipak Barua e-mail:
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Immuno-receptors: from recognition to signaling and function. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2018; 47:363-371. [PMID: 29600443 DOI: 10.1007/s00249-018-1294-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 03/06/2018] [Accepted: 03/13/2018] [Indexed: 01/20/2023]
Abstract
The vertebrate adaptive immune response is initiated by specific recognition of antigens. This is carried out by molecules, soluble or cell surface receptors that are members of the Multichain Immune Recognition Receptors (MIRR) group of proteins. The soluble arm of the response is based on antibodies. Kinetic analysis of antibody-antigenic epitope interactions pioneered insights into the complexity underlying the capacity of relatively limited repertoires of antibodies to recognize an essentially unlimited range of epitopes by employing conformational diversity of a given single sequence. The arm responsible for recognition of cellular targets involves a considerably more elaborate process, predominantly of antigen-derived peptides presented bound to molecules encoded by the major histocompatibility complex (MHC). This remarkable cellular recognition process performed by T-cell receptors requires earlier steps of peptide presentation and involves interactions of the receptor sites with the array of its MHC-peptide composite ligand. In both cases, antigen recognition needs to be followed by its coupling, by biochemical cascades, to different specific responses, namely activation of effector functions. The parameters required for coupling to functional responses are still a focus of intense research. In solution, antigen-antibody aggregation is one established activation process. Those required for coupling antigen recognition to cell activation, whether by Fc receptor bound antibodies or by the B-cell antigen receptor, are also still subject to active research efforts. Though activation by immune-receptors requires antigen recognition, considerable differences could exist among the requirements set by distinct cell types. Moreover, antigen binding requiring intercellular interactions introduces additional complexity.
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Schwartz SL, Yan Q, Telmer CA, Lidke KA, Bruchez MP, Lidke DS. Fluorogen-activating proteins provide tunable labeling densities for tracking FcεRI independent of IgE. ACS Chem Biol 2015; 10:539-46. [PMID: 25343439 PMCID: PMC4340345 DOI: 10.1021/cb5005146] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Crosslinking of IgE bound FcεRI on mast cells and basophils by multivalent antigen leads to degranulation and the release of key inflammatory mediators that stimulate the allergic response. Here, we present and characterize the use of fluorogen-activating proteins (FAPs) for single particle tracking of FcεRI to investigate how receptor mobility is influenced after IgE-induced changes in mast cell behavior. FAPs are genetically encoded tags that bind a fluorogen dye and increase its brightness upon binding up to 20,000-fold. We demonstrate that, by titrating fluorogen concentration, labeling densities from ensemble to single particle can be achieved, independent of expression level and without the need for wash steps or photobleaching. The FcεRI γ-subunit fused to a FAP (FAP-γ) provides, for the first time, an IgE-independent probe for tracking this signaling subunit of FcεRI at the single molecule level. We show that the FcεRI γ-subunit dynamics are controlled by the IgE-binding α-subunit and that the cytokinergic IgE, SPE-7, induces mast cell activation without altering FcεRI mobility or promoting internalization. We take advantage of the far-red emission of the malachite green (MG) fluorogen to track FcεRI relative to dynamin-GFP and find that immobilized receptors readily correlate with locations of dynamin recruitment only under conditions that promote rapid endocytosis. These studies demonstrate the usefulness of the FAP system for single molecule studies and have provided new insights into the relationship among FcεRI structure, activity, and mobility.
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Affiliation(s)
- Samantha L. Schwartz
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
| | - Qi Yan
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
| | - Cheryl A. Telmer
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
| | - Keith A. Lidke
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
| | - Marcel P. Bruchez
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
| | - Diane S. Lidke
- Department of Pathology and Cancer
Research and Treatment Center, ‡Department of Physics
and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Molecular Biosensor and Imaging Center, ∥Department of Biological
Sciences, ⊥Lane Center for
Computational Biology, #Department of Chemistry, Carnegie Mellon University, Pittsburgh Pennsylvania 15213, United States
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Spatio-temporal signaling in mast cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 716:91-106. [PMID: 21713653 DOI: 10.1007/978-1-4419-9533-9_6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
This chapter summarizes the evidence for localized signaling domains in mast cells and basophils, with a particular focus on the high affinity IgE receptor, FcεRI and its crosstalk with other membrane proteins. It is noteworthy that a literature spanning 30 years established the FcεRI as a model receptor for studying activation-induced changes in receptor diffusion and lipid raft association. Now a combination of high resolution microscopy methods, including immunoelectron microscopy and sophisticated fluorescence-based techniques, provide new insight into the nanoscale spatial and temporal aspects of receptor topography on the mast cell plasma membrane. Physical crosslinking of FcεRI with multivalent ligands leads to formation of IgE receptor clusters, termed "signaling patches," that recruit downstream signaling molecules. However, classes of receptors that engage solely withmono valent ligands can also form distinctive signaling patches. The dynamic relationships between receptor diffusion, aggregation state, clustering, signal initiation and signal strength are discussed in the context of these recent findings.
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Jaumouillé V, Grinstein S. Receptor mobility, the cytoskeleton, and particle binding during phagocytosis. Curr Opin Cell Biol 2010; 23:22-9. [PMID: 21074980 DOI: 10.1016/j.ceb.2010.10.006] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2010] [Revised: 10/11/2010] [Accepted: 10/17/2010] [Indexed: 02/04/2023]
Abstract
Particle engulfment during phagocytosis has long been appreciated to be an active, actin-driven process. By contrast, the preceding stage--securing the target to the surface of the phagocyte--was thought to result from the passive diffusion of receptors along the membrane towards their ligands on the particle surface. Recent evidence, however, challenges this notion, demonstrating that receptors do not diffuse freely along the phagocyte surface and that actin polymerization and tyrosine phosphorylation are required for optimal particle binding. The interpretation and significance of these observations are the subject of this opinion piece.
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Affiliation(s)
- Valentin Jaumouillé
- Cell Biology Program, Hospital for Sick Children, 555 University Ave., Toronto M5G 1X8, Canada
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Sigalov AB. The SCHOOL of nature: I. Transmembrane signaling. SELF/NONSELF 2010; 1:4-39. [PMID: 21559175 PMCID: PMC3091606 DOI: 10.4161/self.1.1.10832] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 11/30/2009] [Accepted: 12/01/2009] [Indexed: 11/19/2022]
Abstract
Receptor-mediated transmembrane signaling plays an important role in health and disease. Recent significant advances in our understanding of the molecular mechanisms linking ligand binding to receptor activation revealed previously unrecognized striking similarities in the basic structural principles of function of numerous cell surface receptors. In this work, I demonstrate that the Signaling Chain Homooligomerization (SCHOOL)-based mechanism represents a general biological mechanism of transmembrane signal transduction mediated by a variety of functionally unrelated single- and multichain activating receptors. within the SCHOOL platform, ligand binding-induced receptor clustering is translated across the membrane into protein oligomerization in cytoplasmic milieu. This platform resolves a long-standing puzzle in transmembrane signal transduction and reveals the major driving forces coupling recognition and activation functions at the level of protein-protein interactions-biochemical processes that can be influenced and controlled. The basic principles of transmembrane signaling learned from the SCHOOL model can be used in different fields of immunology, virology, molecular and cell biology and others to describe, explain and predict various phenomena and processes mediated by a variety of functionally diverse and unrelated receptors. Beyond providing novel perspectives for fundamental research, the platform opens new avenues for drug discovery and development.
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Affiliation(s)
- Alexander B Sigalov
- Department of Pathology; University of Massachusetts Medical School; Worcester, MA USA
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Andrews NL, Pfeiffer JR, Martinez AM, Haaland DM, Davis RW, Kawakami T, Oliver JM, Wilson BS, Lidke DS. Small, mobile FcepsilonRI receptor aggregates are signaling competent. Immunity 2009; 31:469-79. [PMID: 19747859 DOI: 10.1016/j.immuni.2009.06.026] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Revised: 06/15/2009] [Accepted: 06/24/2009] [Indexed: 10/20/2022]
Abstract
Crosslinking of IgE-bound FcepsilonRI triggers mast cell degranulation. Previous fluorescence recovery after photobleaching (FRAP) and phosphorescent anisotropy studies suggested that FcepsilonRI must immobilize to signal. Here, single quantum dot (QD) tracking and hyperspectral microscopy methods were used for defining the relationship between receptor mobility and signaling. QD-IgE-FcepsilonRI aggregates of at least three receptors remained highly mobile over extended times at low concentrations of antigen that induced Syk kinase activation and near-maximal secretion. Multivalent antigen, presented as DNP-QD, also remained mobile at low doses that supported secretion. FcepsilonRI immobilization was marked at intermediate and high antigen concentrations, correlating with increases in cluster size and rates of receptor internalization. The kinase inhibitor PP2 blocked secretion without affecting immobilization or internalization. We propose that immobility is a feature of highly crosslinked immunoreceptor aggregates and a trigger for receptor internalization, but is not required for tyrosine kinase activation leading to secretion.
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Affiliation(s)
- Nicholas L Andrews
- Department of Pathology and Cancer Research and Treatment Center, University of New Mexico, Albuquerque, NM 87131, USA
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Signaling Chain Homooligomerization (SCHOOL) Model. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 640:121-63. [DOI: 10.1007/978-0-387-09789-3_12] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Schweitzer-Stenner R, Pecht I. Parameters determining the stimulatory capacity of the type I Fc epsilon-receptor. Immunol Lett 1999; 68:59-69. [PMID: 10397157 DOI: 10.1016/s0165-2478(99)00031-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several experiments and theoretical considerations aimed at obtaining the parameters which determine the capacity of type I Fc epsilon-receptors to stimulate the secretion of mast cells are reviewed. Earlier studies have established that secretion requires Fc epsilon RI clustering at least two dimers. The roles of such clusters lifetimes and configuration requires a detailed and quantitative analysis of Fc epsilon RI clustering and stimulus secretion. Different approaches to these issues are described and discussed. We especially address the relevance of the general concept of kinetical proof reading (T.W. McKeithan, Proc. Natl. Acad. Sci. USA 92 (1995) 5042) which is based on the assumption that the stimulating receptors must stay in an active state sufficiently long to bridge the time interval between initiation and termination of cell activation. For mast cells which generally secrete upon clustering of type I Fc epsilon-receptors, this implies that effective stimulation requires a sufficiently long lifetime of such clusters. This notion is corroborated by results obtained from several experiments performed in the last 20 years which are briefly described and compared in this review.
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Schweitzer-Stenner R, Tamir I, Pecht I. Analysis of Fc(epsilon)RI-mediated mast cell stimulation by surface-carried antigens. Biophys J 1997; 72:2470-8. [PMID: 9168023 PMCID: PMC1184445 DOI: 10.1016/s0006-3495(97)78891-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Clustering of the type I receptor for IgE (Fc[epsilon]RI) on mast cells initiates a cascade of biochemical processes that result in secretion of inflammatory mediators. To determine the Fc(epsilon)RI proximity, cluster size, and mobility requirements for initiating the Fc(epsilon)RI cascade, a novel experimental protocol has been developed in which mast cells are reacted with glass surfaces carrying different densities of both antigen and bound IgE, and the cell's secretory response to these stimuli is measured. The results have been analyzed in terms of a model based on the following assumptions: 1) the glass surface antigen distribution and consequently that of the bound IgE are random; 2) Fc(epsilon)RI binding to these surface-bound IgEs immobilizes the former and saturates the latter; 3) the cell surface is formally divided into small elements, which function as a secretory stimulus unit when occupied by two or more immobilized IgE-Fc(epsilon)RI complexes; 4) alternatively, similar stimulatory units can be formed by binding of surface-carried IgE dimers to two Fc(epsilon)RI. This model yielded a satisfactory and self-consistent fitting of all of the different experimental data sets. Hence the present results establish the essential role of Fc(epsilon)RI immobilization for initiating its signaling cascade. Moreover, it provides independent support for the notion that as few as two Fc(epsilon)RIs immobilized at van der Waals contact constitute an "elementary stimulatory unit" leading to mast cell (RBL-2H3 line) secretory response.
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Mao SY, Metzger H. Characterization of protein-tyrosine phosphatases that dephosphorylate the high affinity IgE receptor. J Biol Chem 1997; 272:14067-73. [PMID: 9162030 DOI: 10.1074/jbc.272.22.14067] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
An early event that follows aggregation of the high affinity receptor for IgE (FcepsilonRI) is the phosphorylation of protein tyrosines, especially those on the beta- and gamma-subunits of the receptor. Disaggregation of the receptors leads to their rapid dephosphorylation, but even stably aggregated receptors undergo continual rounds of phosphorylation and dephosphorylation. We developed assays to study dephosphorylation of the receptors and other cellular proteins. Whole cell extracts dephosphorylated both subunits of the receptors rapidly and were as active against aggregated as against disaggregated FcepsilonRI. Upon disaggregation, the in vivo dephosphorylation of the FcepsilonRI and several other proteins followed first-order kinetics with closely similar rate constants despite substantial differences in the extent of phosphorylation. These results suggest that the level of phosphorylation of FcepsilonRI is largely controlled by the aggregation-induced action of kinase(s) and not from changes in susceptibility to or activity of the phosphatases. Much of the total phosphatase is lost when the cells are permeabilized, but the rate of dephosphorylation of disaggregated FcepsilonRI was comparable in intact and permeabilized cells. Thus, much of the activity utilized by the cell to dephosphorylate the FcepsilonRI is likely to be associated with the plasma membrane.
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Affiliation(s)
- S Y Mao
- Arthritis and Rheumatism Branch, NIAMS, National Institutes of Health, Bethesda, Maryland 20892, USA
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Abstract
This review deals with membrane Fc receptors (FcR) of the immunoglobulin superfamily. It is focused on the mechanisms by which FcR trigger and regulate biological responses of cells on which they are expressed. FcR deliver signals when they are aggregated at the cell surface. The aggregation of FcR having immunoreceptor tyrosine-based activation motifs (ITAMs) activates sequentially src family tyrosine kinases and syk family tyrosine kinases that connect transduced signals to common activation pathways shared with other receptors. FcR with ITAMs elicit cell activation, endocytosis, and phagocytosis. The nature of responses depends primarily on the cell type. The aggregation of FcR without ITAM does not trigger cell activation. Most of these FcR internalize their ligands, which can be endocytosed, phagocytosed, or transcytosed. The fate of internalized receptor-ligand complexes depends on defined sequences in the intracytoplasmic domain of the receptors. The coaggregation of different FcR results in positive or negative cooperation. Some FcR without ITAM use FcR with ITAM as signal transduction subunits. The coaggregation of antigen receptors or of FcR having ITAMs with FcR having immunoreceptor tyrosine-based inhibition motifs (ITIMs) negatively regulates cell activation. FcR therefore appear as the subunits of multichain receptors whose constitution is not predetermined and which deliver adaptative messages as a function of the environment.
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Affiliation(s)
- M Daëron
- Laboratoire d'Immunologie Cellulaire et Clinique, INSERM U.255, Institut Curie, Paris, France.
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