GO:0019863 IgE binding: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0019863 IgE binding is a molecular function defined as binding to an immunoglobulin of the IgE isotype.
• IgE binding to its high-affinity receptor FcεRI on mast cells and basophils is the central trigger of allergic reactions.
• Structural flexibility and glycosylation of IgE modulate its binding to receptors and contribute to functional heterogeneity.
• Soluble IgE-binding factors, such as soluble FcεRI, can act as protective decoys in food allergy.
• IgE-binding monocytes have been identified in equine Culicoides hypersensitivity, showing the function extends beyond classical effector cells.
• Therapeutic anti-IgE antibodies block IgE binding to FcεRI and are used in allergic rhinitis and other IgE-mediated diseases.
Description
GO:0019863 IgE binding is a molecular function term that describes the selective interaction of a protein or other molecule with an immunoglobulin of the IgE isotype. IgE is the least abundant antibody class in serum, yet it plays a central role in type I hypersensitivity and allergic diseases. The binding of IgE to its high-affinity receptor FcεRI on mast cells and basophils initiates a signaling cascade that leads to degranulation and release of inflammatory mediators. This function is therefore critical for understanding allergy pathogenesis and for developing therapeutic strategies that target IgE-receptor interactions. Beyond classical effector cells, IgE binding has been observed on monocytes in equine hypersensitivity, indicating a broader cellular distribution. Structural studies have revealed that IgE flexibility and glycosylation influence receptor binding, adding layers of complexity to this molecular function. Soluble IgE-binding factors such as soluble FcεRI can interfere with IgE binding and may serve protective roles in food allergy. Given the clinical importance of IgE, researchers require robust models to dissect the molecular determinants of IgE binding and its downstream effects.
IgE binding At A Glance
| GO ID | GO:0019863 |
|---|---|
| GO term | IgE binding |
| Ontology | molecular_function |
| Synonym | none |
| Definition | Binding to an immunoglobulin of the IgE isotype. |
| Major function | Mediates interaction with IgE antibodies, initiating allergic signaling and immune modulation. |
| Related receptors | FcεRI, FcεRII (CD23), soluble FcεRI |
| Cellular context | Mast cells, basophils, monocytes, B cells |
What Is GO:0019863?
According to the Gene Ontology, GO:0019863 IgE binding is defined as the binding to an immunoglobulin of the IgE isotype. This molecular function encompasses any interaction between a protein or molecule and the Fc region of IgE, including binding to high-affinity receptors like FcεRI, low-affinity receptors such as CD23, and soluble IgE-binding factors. The term does not specify the identity of the binding partner, only that the target is IgE.
Why Is IgE binding Important in Cell Biology?
IgE binding is a fundamental event in allergic diseases, as it triggers the release of histamine and other mediators from mast cells and basophils upon allergen cross-linking. Understanding the molecular details of IgE binding is essential for designing inhibitors that block this interaction, such as anti-IgE antibodies used in allergic rhinitis. Moreover, IgE binding to low-affinity receptors like CD23 regulates IgE synthesis and antigen presentation. The discovery of soluble IgE-binding factors suggests endogenous mechanisms that modulate allergic responses and could be harnessed therapeutically. In veterinary species, IgE binding to monocytes has been linked to insect bite hypersensitivity, highlighting its broader biological relevance.
• IgE binding to FcεRI is the initiating step of immediate hypersensitivity reactions.
• Blocking IgE binding with anti-IgE antibodies reduces symptoms in allergic rhinitis.
• Soluble FcεRI acts as a protective factor by sequestering IgE in food allergy.
• IgE-binding monocytes are involved in equine Culicoides hypersensitivity.
• Structural flexibility and glycosylation of IgE affect receptor binding affinity.
• CD23 (FcεRII) binding to IgE regulates IgE production and allergic inflammation.
• Allergen-specific IgE binding is a diagnostic marker for allergic sensitization.
• Recombinant allergens with modified IgE binding sites are being developed for immunotherapy.
• IgE binding to receptors on dendritic cells influences T cell polarization.
• Understanding IgE binding at the molecular level aids in the design of small-molecule inhibitors.
Molecular Mechanism of IgE binding
IgE Structure and Flexibility
In simple terms: IgE is an antibody that can bend and flex, which helps it bind to receptors on cells.
IgE is a Y-shaped antibody composed of two heavy chains and two light chains. Its Fc region, particularly the Cε2 and Cε3 domains, exhibits conformational flexibility that allows it to adopt different shapes upon receptor binding. This flexibility is crucial for engaging both high-affinity FcεRI and low-affinity CD23 receptors. Glycosylation of the IgE Fc region further modulates its interaction with receptors, influencing binding affinity and downstream signaling.
High-Affinity Receptor FcεRI Binding
In simple terms: IgE binds tightly to a receptor called FcεRI on mast cells and basophils, triggering allergic reactions.
The high-affinity IgE receptor FcεRI is a tetrameric complex (αβγ2) expressed on mast cells, basophils, and dendritic cells. The extracellular α chain binds to the Cε3 domain of IgE with nanomolar affinity. Recent cryo-EM structures have revealed that IgE binding induces conformational changes in FcεRI that lead to receptor dimerization and activation of downstream signaling pathways, including Lyn and Syk kinases. This binding is the central event in allergic sensitization and effector cell activation.
Low-Affinity Receptor CD23 (FcεRII) Binding
In simple terms: IgE also binds to a lower-affinity receptor called CD23, which helps regulate IgE levels.
CD23, also known as FcεRII, is a C-type lectin expressed on B cells, monocytes, and eosinophils. It binds IgE with lower affinity than FcεRI but plays a critical role in regulating IgE synthesis and antigen presentation. The interaction between CD23 and IgE can either enhance or suppress allergic responses depending on the cellular context and the presence of soluble CD23 fragments. IgE-binding factors derived from CD23 have been shown to modulate IgE production in vitro.
Soluble IgE-Binding Factors
In simple terms: Some proteins in the blood can bind IgE and act as decoys, potentially protecting against allergies.
Soluble forms of FcεRI (sFcεRI) and other IgE-binding factors circulate in serum and can compete with membrane-bound receptors for IgE binding. In food-allergic patients, higher levels of sFcεRI are associated with a protective phenotype, suggesting that these soluble factors neutralize IgE and prevent effector cell activation. The precise mechanisms by which soluble IgE-binding factors modulate allergic responses are an active area of research.
IgE Binding to Monocytes and Other Cells
In simple terms: IgE can also bind to immune cells called monocytes, which may contribute to allergic inflammation.
In equine Culicoides hypersensitivity, a subset of monocytes expresses FcεRI and binds IgE, leading to the production of pro-inflammatory cytokines. This finding expands the known cellular targets of IgE binding beyond mast cells and basophils and suggests that monocytes may contribute to allergic inflammation in both humans and animals. The functional consequences of IgE binding to monocytes are still being elucidated.
Key Genes Involved in GO:0019863 IgE binding
The following genes encode proteins that directly bind IgE or are critical for IgE binding and its downstream effects.
| Gene | Major Role | Research Relevance |
|---|---|---|
| FCER1A | High-affinity IgE receptor alpha chain | Mediates IgE binding on mast cells and basophils; target for anti-allergy drugs. |
| FCER1B | High-affinity IgE receptor beta chain | Amplifies FcεRI signaling; mutations linked to atopy. |
| FCER1G | High-affinity IgE receptor gamma chain | Contains ITAM motifs for signal transduction. |
| FCER2 | Low-affinity IgE receptor (CD23) | Regulates IgE synthesis and antigen presentation. |
| IGHE | IgE heavy chain constant region | Determines IgE isotype and binding specificity. |
| MS4A2 | Beta subunit of FcεRI | Modulates receptor expression and signaling. |
| LYN | Src-family kinase | Phosphorylates ITAMs upon IgE binding. |
| SYK | Spleen tyrosine kinase | Key downstream effector of FcεRI signaling. |
| BTK | Bruton's tyrosine kinase | Required for mast cell activation after IgE binding. |
| PLCG1 | Phospholipase C gamma 1 | Mediates calcium flux and degranulation. |
| PIK3CD | Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta | Contributes to FcεRI signaling and cytokine production. |
| CD23 | Low-affinity IgE receptor | Soluble form regulates IgE levels. |
| IL4 | Interleukin-4 | Induces IgE class switching and FcεRI expression. |
| IL13 | Interleukin-13 | Promotes IgE production and allergic inflammation. |
| STAT6 | Signal transducer and activator of transcription 6 | Transduces IL-4/IL-13 signals for IgE synthesis. |
| SPINK5 | Serine peptidase inhibitor Kazal type 5 | Mutations cause Netherton syndrome with elevated IgE. |
| DERP2 | Dermatophagoides pteronyssinus allergen 2 | Binds IgE and is used in immunotherapy design. |
How Is IgE binding Regulated?
IgE binding is regulated at multiple levels. The expression of FcεRI on mast cells and basophils is upregulated by IgE itself, creating a positive feedback loop that enhances sensitivity to allergens. Cytokines such as IL-4 and IL-13 promote IgE class switching and FcεRI expression through STAT6 signaling. Glycosylation of IgE modulates its binding affinity for FcεRI and CD23, with sialylation and fucosylation influencing receptor engagement. Soluble forms of FcεRI and other IgE-binding factors can compete with membrane receptors and downregulate allergic responses. Additionally, the structural flexibility of IgE allows it to adopt multiple conformations, which may be regulated by local environmental factors such as pH and ionic strength.
IgE binding and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FCER1A | Allergic rhinitis, asthma | Knockout mouse or human mast cell line (LAD2) with FCER1A KO. |
| FCER2 | Food allergy, atopic dermatitis | CD23 knockout mouse or B cell line with CD23 overexpression. |
| IGHE | Hyper-IgE syndrome, allergy | Humanized mouse expressing human IgE. |
| SPINK5 | Netherton syndrome | SPINK5 knockout mouse or keratinocyte model. |
| DERP2 | House dust mite allergy | Recombinant allergen with modified IgE binding site for immunotherapy. |
Allergic Rhinitis and Asthma
IgE binding to FcεRI on mast cells triggers the release of histamine and leukotrienes, leading to sneezing, rhinorrhea, and bronchoconstriction in allergic rhinitis and asthma. Anti-IgE therapy with omalizumab blocks this binding and reduces symptoms in patients with severe allergic rhinitis. The degree of IgE binding correlates with disease severity and can be monitored as a biomarker.
Food Allergy
In food allergy, allergen-specific IgE binds to FcεRI on mast cells and basophils, causing rapid hypersensitivity reactions upon food ingestion. Soluble FcεRI in serum can bind IgE and act as a protective factor, potentially preventing severe reactions. Understanding the molecular details of IgE binding to food allergens is critical for developing safe immunotherapies.
Atopic Dermatitis and Netherton Syndrome
Atopic dermatitis is characterized by elevated IgE levels and increased IgE binding to FcεRI on skin mast cells and dendritic cells, contributing to chronic inflammation. In Netherton syndrome, mutations in SPINK5 lead to skin barrier defects and highly elevated IgE, with increased IgE binding to receptors on immune cells.
Equine Culicoides Hypersensitivity
In horses, IgE binding to monocytes is a hallmark of Culicoides hypersensitivity, an allergic skin disease caused by insect bites. These IgE-binding monocytes produce pro-inflammatory cytokines and may serve as a model for studying IgE-mediated inflammation in humans.
From IgE binding-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does FCER1A mediate IgE binding in mast cells? | FCER1A knockout in human mast cell line (LAD2). |
| What is the role of IgE glycosylation in receptor binding? | Point mutations at glycosylation sites in IGHE, expressed in HEK293 cells. |
| Can soluble FcεRI block IgE binding in vivo? | Knock-in mouse expressing soluble FcεRI. |
| How does CD23 regulate IgE synthesis? | CD23 overexpression in B cell lines. |
| Does a specific allergen epitope trigger IgE binding? | Site-directed mutagenesis of Der p 2 to abrogate IgE binding. |
| What is the effect of anti-IgE antibodies on IgE binding? | Competitive binding assays with omalizumab and IgE. |
How to Study the IgE binding Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Surface Plasmon Resonance | Binding affinity and kinetics | Characterizing IgE-receptor interactions. |
| Flow Cytometry | Cell surface IgE binding | Quantifying FcεRI on mast cells and basophils. |
| ELISA | Allergen-specific IgE levels | Diagnosing food allergy and monitoring therapy. |
| Cryo-EM | 3D structure of IgE-receptor complexes | Elucidating activation mechanisms. |
| Isothermal Titration Calorimetry | Thermodynamics of IgE binding | Assessing the role of glycosylation. |
| Immunoprecipitation | Protein-protein interactions | Identifying novel IgE-binding factors. |
| Biolayer Interferometry | Real-time binding kinetics | Screening anti-IgE antibodies. |
| Site-directed mutagenesis | Effect of specific residues on binding | Mapping IgE binding sites on allergens. |
Surface Plasmon Resonance (SPR)
SPR measures real-time binding kinetics between IgE and its receptors or binding factors. It provides quantitative data on association and dissociation rates, which are critical for understanding the affinity of IgE binding. This method is widely used to screen inhibitors that block IgE-receptor interactions.
Flow Cytometry
Flow cytometry detects IgE binding to cell surface receptors using fluorescently labeled IgE or anti-IgE antibodies. It is used to quantify FcεRI expression on mast cells, basophils, and monocytes, and to assess competitive binding of therapeutic antibodies.
Enzyme-Linked Immunosorbent Assay (ELISA)
ELISA measures allergen-specific IgE in serum and can be adapted to assess IgE binding to recombinant allergens or soluble receptors. It is a standard diagnostic tool for allergy and is used to evaluate the inhibitory capacity of soluble FcεRI.
Cryo-Electron Microscopy (Cryo-EM)
Cryo-EM resolves the three-dimensional structure of IgE-receptor complexes at near-atomic resolution, revealing conformational changes that occur upon binding. This technique has been instrumental in understanding how IgE binding activates FcεRI.
How CRISPR Can Be Used to Study GO:0019863 IgE binding
Knockout
CRISPR knockout of FCER1A, FCER1B, or FCER1G in mast cell lines (e.g., LAD2) abolishes IgE binding and downstream signaling, providing a clean model to study the receptor's role in allergic responses. Knockout of FCER2 (CD23) in B cells helps dissect its function in IgE regulation.
Point Mutation
Introducing point mutations in the IgE-binding domains of FcεRI or CD23 can fine-tune binding affinity and reveal critical residues. For example, mutating glycosylation sites in IgE heavy chain alters receptor binding, which can be modeled by CRISPR-mediated knock-in of mutant IGHE.
Knock-in
Knock-in of human FCER1A into mouse mast cells or knock-in of tagged FcεRI allows tracking of receptor trafficking and binding in vivo. Knock-in of soluble FcεRI into mouse models can test its protective role in food allergy.
Overexpression
Overexpression of CD23 or FcεRI in cell lines via CRISPR activation or lentiviral delivery enhances IgE binding and can be used for high-throughput screening of inhibitors. Overexpression of Der p 2 mutants with altered IgE binding helps design hypoallergens for immunotherapy.
How EDITGENE Supports IgE binding Research
Researchers studying IgE binding-related genes often need to determine whether a candidate gene is causally involved in allergic sensitization or effector cell activation. CRISPR-based models provide a precise way to manipulate genes encoding IgE receptors, binding factors, and signaling molecules, enabling functional validation in relevant cell types.
Contact EDITGENE today to design your custom CRISPR model for IgE binding research.
Frequently Asked Questions About IgE binding
What is GO:0019863 IgE binding?
GO:0019863 IgE binding is a Gene Ontology molecular function term defined as binding to an immunoglobulin of the IgE isotype.
What genes are involved in IgE binding?
Key genes include FCER1A, FCER1B, FCER1G, FCER2 (CD23), IGHE, and signaling molecules like LYN, SYK, and BTK.
How does IgE bind to mast cells?
IgE binds to the high-affinity receptor FcεRI on mast cells via its Cε3 domain, triggering receptor aggregation and degranulation.
What is the role of CD23 in IgE binding?
CD23 (FcεRII) is a low-affinity receptor that binds IgE and regulates IgE synthesis and antigen presentation.
Can IgE binding be blocked therapeutically?
Yes, anti-IgE antibodies such as omalizumab block IgE binding to FcεRI and are used to treat allergic rhinitis and asthma.
What are soluble IgE-binding factors?
Soluble IgE-binding factors, such as soluble FcεRI, are circulating proteins that bind IgE and may protect against allergic reactions.
How is IgE binding measured in the lab?
Common methods include ELISA, flow cytometry, surface plasmon resonance, and cryo-EM.
What diseases are associated with IgE binding?
Allergic rhinitis, asthma, food allergy, atopic dermatitis, and Netherton syndrome are linked to IgE binding.
What animal models are used to study IgE binding?
Mouse models with humanized IgE receptors and equine models of Culicoides hypersensitivity are used.
How can CRISPR help study IgE binding?
CRISPR knockout, knock-in, and overexpression models allow precise manipulation of IgE receptors and binding factors to study their function.
Conclusion
GO:0019863 IgE binding is a central molecular function in allergic diseases, mediating the interaction between IgE and its receptors on immune cells. Understanding its structural and regulatory mechanisms has led to therapeutic advances such as anti-IgE antibodies and soluble receptor decoys. Continued research using CRISPR models and advanced biophysical methods will further unravel the complexities of IgE binding and identify new targets for intervention.
References
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