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A quantitative approach for studying IgE-FcepsilonRI aggregation
Richard G Posner1, Paul B Savage, Adam S Peters
1Department of Chemistry, Northern Arizona University, Flagstaff, AZ 86011-5698, USA. richard.posner@nau.edu
Insights
Ligand valence significantly impacts cell signaling. Increasing ligand valence from two to three dramatically amplifies the cellular response by enhancing receptor aggregation. This study quantifies this effect using advanced flow cytometry.
Area of Science:
- Cellular Biology
- Immunology
- Biophysics
Background:
- Cell surface receptor aggregation initiates signal transduction.
- The IgE-FcεRI pathway on RBL cells is a key model for studying receptor-mediated signaling.
Purpose of the Study:
- To develop and apply a multiparameter flow cytometry assay for measuring ligand-induced IgE-FcεRI aggregation kinetics.
- To investigate the influence of ligand valence on receptor aggregation and cellular response.
Main Methods:
- Utilized multiparameter flow cytometry with fluorescently labeled ligands and surface IgE (sIgE).
- Employed advanced mixing technologies for sub-second temporal resolution of aggregation.
- Synthesized chemically defined ligands of valences 1-3 to probe IgE-FcεRI aggregation.
Main Results:
- Developed an assay to simultaneously measure sIgE binding and antigen association, enabling direct calculation of receptor aggregation.
- Achieved sub-second resolution of ligand-induced receptor aggregation.
- Demonstrated a dramatic increase in cellular response magnitude with increasing ligand valence from two to three.
Conclusions:
- Ligand valence is a critical determinant of the cellular response magnitude in IgE-FcεRI signaling.
- The developed flow cytometry assay provides a powerful tool for studying rapid receptor-ligand interactions and aggregation dynamics.
Abstract:
Aggregation of cell surface receptors is a ubiquitous means of initiating signal transduction in many cellular systems. In this manuscript, we describe a combined theoretical and experimental approach based on multiparameter flow cytometry for measuring the time course of ligand induced aggregation of IgE-FcepsilonRI on RBL cells. By fluorescently labeling both the ligand and surface IgE (sIgE), we have developed an assay that permits us to simultaneously measure both occupancy of sIgE combining sites and association of antigen with the cell surface. This allows for a direct calculation of the degree of receptor aggregation present on the cell. By employing new mixing technologies developed for flow cytometry, we are able to look at aggregation in the sub second time domain. To extend our work, we have synthesized a new set of chemically well defined ligands (of valences 1-3) to use as probes in our studies. We show that the magnitude of the cellular response is dramatically increased as the valence of our ligand is raised from two to three.