Biology subjects

Wilson, B. S.

Publications and source records attributed to Wilson, B. S..

5 recordsLinked to original sources

bioRxiv2025

IgE occupancy and antigen valency cooperate to control FcϵRI aggregation geometry and signaling efficiency

The crosslinking of IgE-bound Fc{varepsilon}RI by multivalent allergens initiates mast cell and basophil signaling underlying Type 1 allergy. Yet, how allergen properties and IgE occupancy impact receptor aggregation and downstream signaling remain unclear. We used Phl p 1-specific IgE and recombinant fusion proteins presenting a Phl p 1-derived peptide in defined valencies and positions (MB1N, MB2N, MB4N, MB1N1C) to probe antigen-dependent signaling. Tetravalent MB4N evoked stronger degranulation and Ca2+ response than bivalent antigens, MB2N and MB1N1C. MB4N was also capable of signaling at low IgE occupancy and in Lyn-deficient cells. Monte Carlo simulations predicted that MB4N forms larger, complex receptor aggregates, while MB2N and MB1N1C produce dimers and linear chains. Consistently, addition of MB4N showed larger aggregates by electron microscopy and slower mobility by single particle tracking, compared to bivalent antigens. Thus, allergen valency and epitope spatial arrangement dictate Fc{varepsilon}RI aggregate organization and subsequent effector cell activation.

immunology↗

bioRxiv2023

Antigen Geometry Tunes Mast Cell Signaling Through Distinct FcϵRI Aggregation andStructural Changes

Fc receptors containing immunoreceptor tyrosine-based activation motifs (ITAMs) are critical components of the innate immune system that bridge adaptive antibody recognition to cellular effector responses. In allergic responses, the high-affinity IgE receptor, Fc{varepsilon}RI, is activated when multivalent antigens crosslink receptor-bound IgE, yet the molecular mechanisms linking antigen structure to signaling output remain incompletely understood. Here, we compare two antigens presenting identical IgE-binding haptens but differing in geometry: the high-valency, heterogeneous DNP-BSA and the defined trivalent antigen DF3. We find that these ligands elicit distinct patterns of degranulation and Fc{varepsilon}RI {gamma}-chain phosphorylation, correlating with differences in the recruitment of the inhibitory lipid phosphatase SHIP1. Monte Carlo simulations predicted that each antigen generates receptor aggregates with distinct size, complexity, and inter-receptor spacing. Using direct stochastic optical reconstruction microscopy (dSTORM) and Bayesian Grouping of Localizations (BaGoL) analysis, we directly visualized the nanoscale aggregate geometry and found that DF3 induced smaller, more linear aggregates with tighter receptor spacing than DNP-BSA. Together, our results show that antigen properties, including size, valency, and epitope spacing, modulate Fc{varepsilon}RI aggregate architecture and tune the balance of positive and negative signaling to ultimately shape mast cell outcomes. Statement of SignificanceAllergic immune responses are initiated when multivalent antigens aggregate IgE-bound Fc{varepsilon}RI on mast cells, yet the relationship between antigen structure and signaling strength remains unclear. This study combines biochemical assays, Monte Carlo modeling, and super-resolution imaging to show that allergen properties, specifically valency and nanoscale epitope spacing, govern the geometry of Fc{varepsilon}RI aggregates and the balance of activating and inhibitory signals. These findings establish a direct mechanistic link between antigen structure and immune receptor output, providing new insight into how physical antigen features encode mast cell responses.

biophysics↗

bioRxiv2020

EGFR transactivates RON to drive oncogenic crosstalk

SUMMARYCrosstalk between disparate membrane receptors is thought to drive oncogenic signaling and allow for therapeutic resistance. EGFR and RON are members of two unique receptor tyrosine kinase (RTK) subfamilies that engage in crosstalk through unknown mechanisms. We combined high resolution imaging with biochemical studies and structural mutants to understand how EGFR and RON communicate. We found that EGF stimulation results in EGFR-dependent RON phosphorylation. Crosstalk is unidirectional, since MSP stimulation of RON does not trigger EGFR phosphorylation. Two-color single particle tracking captured the formation of complexes between RON and EGFR, supporting a role for direct interactions in propagating crosstalk. We further show that RON is a substrate for EGFR kinase, and transactivation of RON requires the formation of a signaling competent EGFR dimer. These results identify critical structural features of EGFR/RON crosstalk and provide new mechanistic insights into therapeutic resistance.

cancer biology↗

bioRxiv2018

Molecular aspects of multivalent engagement between Syk and FcϵRIγ

Syk/Zap70 family kinases are essential for signaling via multichain immune-recognition receptors such as the tetrameric ({beta}{gamma}2) Fc{varepsilon}RI The simplest model assumes that Syk activation occurs through cis binding of its tandem SH2 domains to dual phosphotyrosines within immunoreceptor tyrosine-based activation motifs of individual {gamma} chains. In this model, Syk activity is modulated by phosphorylation occurring between adjacent Syk molecules docked on {gamma} homodimers and by Lyn molecules bound to Fc{varepsilon}RI{beta}. However, the mechanistic details of Syk docking on {gamma} homodimers are not fully resolved, particularly the possibility of trans binding orientations and the impact of Y130 autophosphorylation within Syk interdomain A. Analytical modeling shows that multivalent interactions lead to increased WT Syk cis-oriented binding by three orders of magnitude. Molecular dynamics (MD) simulations show increased inter-SH2 flexibility in a Y130E phosphomimetic form of Syk, associated with reduced overall helicity of interdomain A. Hybrid MD/worm-like chain polymer models show that the Y130E substitution reduces cis binding of Syk. We report computational models and estimates of relative binding for all possible cis and trans 2:2 Syk:Fc{varepsilon}RI{gamma} complexes. Calcium imaging experiments confirm model predictions that cis binding of WT Syk is strongly preferred for efficient signaling, while trans conformations trigger weak but measurable responses.

biophysics↗

bioRxiv2017

Differential Mast Cell Outcomes Are Sensitive to FcϵRI-Syk Binding Kinetics

Crosslinking of IgE-bound Fc{varepsilon}RI triggers multiple cellular responses, including degranulation and cytokine production. Signaling is dependent on recruitment of Syk via docking of its dual SH2 domains to phosphorylated tyrosines within the Fc{varepsilon}RI immunoreceptor tyrosine-based activation motifs. Using single molecule imaging in live cells, we directly visualized and quantified the binding of individual mNeonGreen-tagged Syk molecules as they associated with the plasma membrane after Fc{varepsilon}RI activation. We found that Syk colocalizes transiently to Fc{varepsilon}RI and that Syk-Fc{varepsilon}RI binding dynamics are independent of receptor aggregate size. Substitution of glutamic acid for tyrosine between the Syk SH2 domains (SykY130E) led to an increased Syk-Fc{varepsilon}RI off-rate, loss of site-specific Syk autophosphorylation, and impaired downstream signaling. CRISPR-Cas9 engineered cells expressing only SykY130E were deficient in antigen-stimulated calcium release, degranulation and production of some cytokines (TNF-a, IL-3) but not others (MCP-1, IL-4). We propose that kinetic discrimination along the Fc{varepsilon}RI signaling pathway occurs at the level of Syk-Fc{varepsilon}RI interactions, with key outcomes dependent upon sufficiently long-lived Syk binding events.\n\nSummarySchwartz et al. use single molecule imaging to quantify the transient nature of Fc{varepsilon}RI-Syk interactions in live mast cells. A functional mutation that increases Syk off-rate leads to loss of site-specific Syk phosphorylation and impaired signaling, highlighting the importance of finely tuned protein interactions in directing cellular outcomes.

cell biology↗