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The Humanised NPY-mRFP RBL Reporter Cell Line Is a Fast and Inexpensive Tool for Detection of Allergen-Specific IgE in Human Sera. Diagnostics (Basel) 2022; 12:diagnostics12092063. [PMID: 36140465 PMCID: PMC9497870 DOI: 10.3390/diagnostics12092063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 08/21/2022] [Accepted: 08/23/2022] [Indexed: 12/01/2022] Open
Abstract
Rat basophilic leukaemia (RBL) cells have been used for decades as a model of high-affinity Immunoglobulin E (IgE) receptor (FcεRI) signalling. Here, we describe the generation and use of huNPY-mRFP, a new humanised fluorescent IgE reporter cell line. Fusion of Neuropeptide Y (NPY) with monomeric red fluorescent protein (mRFP) results in targeting of fluorescence to the granules and its fast release into the supernatant upon IgE-dependent stimulation. Following overnight sensitisation with serum, optimal release of fluorescence upon dose-dependent stimulation with allergen-containing extracts could be measured after 45 min, without cell lysis or addition of any reagents. Five substitutions (D194A, K212A, K216A, K226A, and K230A) were introduced into the FcεRIα cDNA used for transfection, which resulted in the removal of known endoplasmic reticulum retention signals and high surface expression of human FcεRIα* in huNPY-mRFP cells (where * denotes the penta-substituted variant), comparable to the ~500,000 FcεRIα molecules per cell in the RS-ATL8 humanised luciferase reporter, which is a human FcεRIα/FcεRIγ double transfectant. The huNPY-mRFP reporter was used to demonstrate engagement of specific IgE in sera of Echinococcus granulosus-infected individuals by E. granulosus elongation factor EgEF-1β and, to a lesser extent, by EgEF-1δ, which had been previously described as IgE-immunoreactive EgEF-1β/δ.
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Zhang Z, Kurashima Y. Two Sides of the Coin: Mast Cells as a Key Regulator of Allergy and Acute/Chronic Inflammation. Cells 2021; 10:cells10071615. [PMID: 34203383 PMCID: PMC8308013 DOI: 10.3390/cells10071615] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/18/2021] [Accepted: 06/25/2021] [Indexed: 12/17/2022] Open
Abstract
It is well known that mast cells (MCs) initiate type I allergic reactions and inflammation in a quick response to the various stimulants, including—but not limited to—allergens, pathogen-associated molecular patterns (PAMPs), and damage-associated molecular patterns (DAMPs). MCs highly express receptors of these ligands and proteases (e.g., tryptase, chymase) and cytokines (TNF), and other granular components (e.g., histamine and serotonin) and aggravate the allergic reaction and inflammation. On the other hand, accumulated evidence has revealed that MCs also possess immune-regulatory functions, suppressing chronic inflammation and allergic reactions on some occasions. IL-2 and IL-10 released from MCs inhibit excessive immune responses. Recently, it has been revealed that allergen immunotherapy modulates the function of MCs from their allergic function to their regulatory function to suppress allergic reactions. This evidence suggests the possibility that manipulation of MCs functions will result in a novel approach to the treatment of various MCs-mediated diseases.
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Affiliation(s)
- Zhongwei Zhang
- Department of Innovative Medicine, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan;
| | - Yosuke Kurashima
- Department of Innovative Medicine, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan;
- Department of Mucosal Immunology, The University of Tokyo Distinguished Professor Unit, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
- International Research and Development Center for Mucosal Vaccines, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
- CU-UCSD Center for Mucosal Immunology, Department of Pathology/Medicine, Allergy and Vaccines, University of California, San Diego, CA 92093-0063, USA
- Mucosal Immunology and Allergy Therapeutics, Institute for Global Prominent Research, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan
- Correspondence: ; Tel.: +81-43-226-2848; Fax: +81-43-226-2183
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Ali EA, Kalli M, Wan D, Nakamura R, Onion D, Alanine DGW, Alcocer MJC, Falcone FH. Characterization of human FcεRIα chain expression and gene copy number in humanized rat basophilic leukaemia (RBL) reporter cell lines. PLoS One 2019; 14:e0221034. [PMID: 31430311 PMCID: PMC6701790 DOI: 10.1371/journal.pone.0221034] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 07/29/2019] [Indexed: 01/23/2023] Open
Abstract
Several laboratories have created rat basophil leukemia (RBL) cell lines stably transfected with the human high affinity IgE receptor (FcεRIH). More recently, humanized RBL cell lines saw the introduction of reporter genes such as luciferase (RS-ATL8) and DsRed (RBL NFAT-DsRed). These reporters are more sensitive than their parental non-reporter humanized RBL cell lines. However, no studies so far have addressed the levels of FcεRIH surface expression on humanized RBL cell lines. This is a critical parameter, as it determines the ability of these cells to be efficiently sensitized with human IgE, hence it should affect the sensitivity of the cell assay–a critical parameter for any diagnostic application. Our purpose was to assess and compare the levels of expression of the transfected FcεRIH chain in humanized RBL cell lines. We compared surface levels of FcεRIαH by flow cytometry, using a fluorescently labelled monoclonal antibody (CRA-1/AER-37) and determined receptor numbers using calibration microspheres. FcεRIαH copy numbers were assessed by qPCR, and the sequence verified. Transfection with FcεRIγH cDNA was assessed for its ability to increase FcεRIαH expression in the NFAT-DsRed reporter. While both SX-38 and RS-ATL8 expressed about 500.000 receptors/cell, RBL 703–21 and NFAT-DsRed had approximately 10- to 30-fold lower FcεRIαH expression, respectively. This was neither related to FcεRIH gene copy numbers, nor to differences in steady state mRNA levels, as determined by qPCR and RT-qPCR, respectively. Instead, FcεRIαH surface expression appeared to correlate with the co-expression of FcεRIγH. Stable transfection of NFAT-DsRed cells with pBJ1 neo-huFcεRI gamma, which constitutively expresses FcεRIγH, increased FcεRIαH chain expression levels. Levels of FcεRIαH surface expression vary greatly between humanized RBL reporter cell lines. This difference will affect the sensitivity of the reporter system when used for diagnostic purposes.
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Affiliation(s)
- Eman Ali Ali
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - Marina Kalli
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - Daniel Wan
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom
| | | | - David Onion
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Daniel G. W. Alanine
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
| | - Marcos J. C. Alcocer
- School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom
| | - Franco H. Falcone
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham, United Kingdom
- * E-mail:
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Transmembrane features governing Fc receptor CD16A assembly with CD16A signaling adaptor molecules. Proc Natl Acad Sci U S A 2017; 114:E5645-E5654. [PMID: 28652325 DOI: 10.1073/pnas.1706483114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many activating immunoreceptors associate with signaling adaptor molecules like FcεR1γ or CD247. FcεR1γ and CD247 share high sequence homology and form disulphide-linked homodimers that contain a pair of acidic aspartic acid residues in their transmembrane (TM) domains that mediate assembly, via interaction with an arginine residue at a similar register to these aspartic acids, with the activating immunoreceptors. However, this model cannot hold true for receptors like CD16A, whose TM domains do not contain basic residues. We have carried out an extensive site-directed mutagenesis analysis of the CD16A receptor complex and now report that the association of receptor with the signaling adaptor depends on a network of polar and aromatic residues along the length of the TM domain. Molecular modeling indicates that CD16A TM residues F202, D205, and T206 form the core of the membrane-embedded trimeric interface by establishing highly favorable contacts to the signaling modules through rearrangement of a hydrogen bond network previously identified in the CD247 TM dimer solution NMR structure. Strikingly, the amino acid D205 also regulates the turnover and surface expression of CD16A in the absence of FcεR1γ or CD247. Modeling studies indicate that similar features underlie the association of other activating immune receptors, including CD64 and FcεR1α, with signaling adaptor molecules, and we confirm experimentally that equivalent F, D, and T residues in the TM domain of FcεR1α markedly influence the biology of this receptor and its association with FcεR1γ.
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Briant K, Koay YH, Otsuka Y, Swanton E. ERAD of proteins containing aberrant transmembrane domains requires ubiquitylation of cytoplasmic lysine residues. J Cell Sci 2015; 128:4112-25. [PMID: 26446255 PMCID: PMC4712780 DOI: 10.1242/jcs.171215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Accepted: 09/28/2015] [Indexed: 11/29/2022] Open
Abstract
Clearance of misfolded proteins from the endoplasmic reticulum (ER) is mediated by the ubiquitin-proteasome system in a process known as ER-associated degradation (ERAD). The mechanisms through which proteins containing aberrant transmembrane domains are degraded by ERAD are poorly understood. To address this question, we generated model ERAD substrates based on CD8 with either a non-native transmembrane domain but a folded ER luminal domain (CD8TMD*), or the native transmembrane domain but a misfolded luminal domain (CD8LUM*). Although both chimeras were degraded by ERAD, we found that the location of the folding defect determined the initial site of ubiquitylation. Ubiquitylation of cytoplasmic lysine residues was required for the extraction of CD8TMD* from the ER membrane during ERAD, whereas CD8LUM* continued to be degraded in the absence of cytoplasmic lysine residues. Cytoplasmic lysine residues were also required for degradation of an additional ERAD substrate containing an unassembled transmembrane domain and when a non-native transmembrane domain was introduced into CD8LUM*. Our results suggest that proteins with defective transmembrane domains are removed from the ER through a specific ERAD mechanism that depends upon ubiquitylation of cytoplasmic lysine residues. Summary: Proteins containing defective transmembrane domains are removed from the endoplasmic reticulum through a specific mechanism that depends upon the ubiquitylation of cytoplasmic lysine residues.
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Affiliation(s)
- Kit Briant
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Yee-Hui Koay
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Yuka Otsuka
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
| | - Eileithyia Swanton
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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Abstract
GLUT4 is regulated by its intracellular localization. In the absence of insulin, GLUT4 is efficiently retained intracellularly within storage compartments in muscle and fat cells. Upon insulin stimulation (and contraction in muscle), GLUT4 translocates from these compartments to the cell surface where it transports glucose from the extracellular milieu into the cell. Its implication in insulin-regulated glucose uptake makes GLUT4 not only a key player in normal glucose homeostasis but also an important element in insulin resistance and type 2 diabetes. Nevertheless, how GLUT4 is retained intracellularly and how insulin acts on this retention mechanism is largely unclear. In this review, the current knowledge regarding the various molecular processes that govern GLUT4 physiology is discussed as well as the questions that remain.
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Anchors aweigh: protein localization and transport mediated by transmembrane domains. Trends Cell Biol 2013; 23:511-7. [PMID: 23806646 PMCID: PMC3783643 DOI: 10.1016/j.tcb.2013.05.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 05/17/2013] [Accepted: 05/20/2013] [Indexed: 11/23/2022]
Abstract
TMDs control the intracellular transport of many membrane proteins. The length and hydrophobicity of TMDs determine their sorting. Some membrane receptors for sorting TMDs have been identified. Lipid partitioning may also participate in the sorting of TMDs.
The transmembrane domains (TMDs) of integral membrane proteins have emerged as major determinants of intracellular localization and transport in the secretory and endocytic pathways. Unlike sorting signals in cytosolic domains, TMD sorting determinants are not conserved amino acid sequences but physical properties such as the length and hydrophilicity of the transmembrane span. The underlying sorting machinery is still poorly characterized, but several mechanisms have been proposed, including TMD recognition by transmembrane sorting receptors and partitioning into membrane lipid domains. Here we review the nature of TMD sorting determinants and how they may dictate transmembrane protein localization and transport.
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Abstract
Elevated IgE levels and increased IgE sensitization to allergens are central features of allergic asthma. IgE binds to the high-affinity Fcε receptor I (FcεRI) on mast cells, basophils, and dendritic cells and mediates the activation of these cells upon antigen-induced cross-linking of IgE-bound FcεRI. FcεRI activation proceeds through a network of signaling molecules and adaptor proteins and is negatively regulated by a number of cell surface and intracellular proteins. Therapeutic neutralization of serum IgE in moderate-to-severe allergic asthmatics reduces the frequency of asthma exacerbations through a reduction in cell surface FcεRI expression that results in decreased FcεRI activation, leading to improved asthma control. Our increasing understanding of IgE receptor signaling may lead to the development of novel therapeutics for the treatment of asthma.
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Affiliation(s)
- Lawren C Wu
- Department of Immunology, Genentech, Incorporated, South San Francisco, California 94080, USA.
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Platzer B, Fiebiger E. The signal peptide of the IgE receptor alpha-chain prevents surface expression of an immunoreceptor tyrosine-based activation motif-free receptor pool. J Biol Chem 2010; 285:15314-15323. [PMID: 20304923 PMCID: PMC2865261 DOI: 10.1074/jbc.m110.104281] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 02/22/2010] [Indexed: 01/02/2023] Open
Abstract
The high affinity receptor for IgE, Fc epsilon receptor I (FcepsilonRI), is an activating immune receptor and key regulator of allergy. Antigen-mediated cross-linking of IgE-loaded FcepsilonRI alpha-chains induces cell activation via immunoreceptor tyrosine-based activation motifs in associated signaling subunits, such as FcepsilonRI gamma-chains. Here we show that the human FcepsilonRI alpha-chain can efficiently reach the cell surface by itself as an IgE-binding receptor in the absence of associated signaling subunits when the endogenous signal peptide is swapped for that of murine major histocompatibility complex class-I H2-K(b). This single-chain isoform of FcepsilonRI exited the endoplasmic reticulum (ER), trafficked to the Golgi and, subsequently, trafficked to the cell surface. Mutational analysis showed that the signal peptide regulates surface expression in concert with other described ER retention signals of FcepsilonRI-alpha. Once the FcepsilonRI alpha-chain reached the cell surface by itself, it formed a ligand-binding receptor that stabilized upon IgE contact. Independently of the FcepsilonRI gamma-chain, this single-chain FcepsilonRI was internalized after receptor cross-linking and trafficked into a LAMP-1-positive lysosomal compartment like multimeric FcepsilonRI. These data suggest that the single-chain isoform is capable of shuttling IgE-antigen complexes into antigen loading compartments, which plays an important physiologic role in the initiation of immune responses toward allergens. We propose that, in addition to cytosolic and transmembrane ER retention signals, the FcepsilonRI alpha-chain signal peptide contains a negative regulatory signal that prevents expression of an immunoreceptor tyrosine-based activation motif-free IgE receptor pool, which would fail to induce cell activation.
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Affiliation(s)
- Barbara Platzer
- Department of Medicine, Division of Gastroenterology and Nutrition, Children's Hospital Boston, Boston, Massachusetts 02115
| | - Edda Fiebiger
- Department of Medicine, Division of Gastroenterology and Nutrition, Children's Hospital Boston, Boston, Massachusetts 02115.
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The first transmembrane region of the beta-chain stabilizes the tetrameric Fc epsilon RI complex. Mol Immunol 2009; 46:2333-9. [PMID: 19406478 DOI: 10.1016/j.molimm.2009.03.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Accepted: 03/28/2009] [Indexed: 12/26/2022]
Abstract
The family of activating immune receptors stabilizes via the 3-helix assembly principle. A charged basic transmembrane residue interacts with two charged acidic transmembrane residues and forms a 3-helix interface to stabilize receptor complexes in the lipid bilayer. One family member, the high affinity receptor for IgE, Fc epsilon RI, is a key regulator of immediate allergic responses. Tetrameric Fc epsilon RI consists of the IgE-binding alpha-chain, the multimembrane-spanning beta-chain and a dimer of the gamma-subunit (Fc epsilon R gamma). Comparative analysis of these seven transmembrane regions indicates that Fc epsilon RI does not meet the charge requirements for the 3-helix assembly mechanism. We performed alanine mutagenesis to show that the only basic amino acid in the transmembrane regions, beta K97, is not involved in Fc epsilon RI stabilization or surface upregulation, a hallmark function of the beta-chain. Even a beta K97E mutant is functional despite four negatively charged acidic amino acids in the transmembrane regions. Using truncation mutants, we demonstrate that the first uncharged transmembrane domain of the beta-chain contains the interface for receptor stabilization. In vitro translation experiments depict the first transmembrane region as the internal signal peptide of the beta-chain. We also show that this beta-chain domain can function as a cleavable signal peptide when used as a leader peptide for a Type I protein. Our results provide evidence that tetrameric Fc epsilon RI does not assemble according to the 3-helix assembly principle. We conclude that receptors formed with multispanning proteins use different mechanisms of shielding transmembrane charged amino acids.
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Ganguly S, Grodzki C, Sugden D, Møller M, Odom S, Gaildrat P, Gery I, Siraganian RP, Rivera J, Klein DC. Neural adrenergic/cyclic AMP regulation of the immunoglobulin E receptor alpha-subunit expression in the mammalian pinealocyte: a neuroendocrine/immune response link? J Biol Chem 2007; 282:32758-64. [PMID: 17728245 DOI: 10.1074/jbc.m705950200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high affinity immunoglobulin E receptor (FcepsilonRI) complex is dedicated to immunoglobulin E-mediated allergic responses. Expression of the FcepsilonRI receptor is thought to be relatively stable and limited to mast cells, basophils, eosinophils, monocytes, Langerhans cells, platelets, and neutrophils. We now report that the FcepsilonRIalpha and FcepsilonRIgamma polypeptides are expressed in the pinealocyte, the melatonin-secreting cell of the pineal gland. Moreover, Fcer1a mRNA levels increased approximately 100-fold at night to levels that were higher than in other tissues examined. Pineal FcepsilonRIalpha protein also increased markedly at night from nearly undetectable daytime levels. Our studies indicate that pineal Fcer1a mRNA levels are controlled by a well described neural pathway that controls pineal function. This pathway includes the master circadian oscillator in the suprachiasmatic nucleus and passes through central and peripheral structures. The circadian expression of FcepsilonRIalpha in the pineal gland is driven by this neural circuit via an adrenergic/cyclic AMP mechanism. Pineal FcepsilonRIalpha and FcepsilonRIgamma may represent a previously unrealized molecular link between the neuroendocrine and immune systems.
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Affiliation(s)
- Surajit Ganguly
- Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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