Building a dynamic model for EGFR-family dimerization using quantitative, live-cell fluorescence methods.

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases plays a central role in cell signaling pathways that regulate proliferation, differentiation, and survival. Aberrant signaling within this family, often caused by mutations or overexpression, drives the progression of many cancers. EGFR and HER2, for example, serve as biomarkers for cancer detection and treatment; however, clinical outcomes still require significant improvement. This review examines the structural details of EGFR-family oligomerization, with a focus on insights gained from advanced fluorescence-based methodologies. We first summarize high-resolution structural studies, including cryo-EM and crystallography, that have contributed to the canonical mechanisms of ligand-induced dimerization and activation. These structural models, however, still leave open many questions about the transient and dynamic nature of receptor oligomerization. To address these dynamic structural details, we highlight recent applications of live-cell, quantitative fluorescence techniques like Förster resonance energy transfer, single-particle tracking, super-resolution microscopy, and fluorescence fluctuation spectroscopy. Fluorescence methods have revealed the existence and stability of both ligand-dependent and -independent receptor dimers, as well as higher-order oligomers, providing important insight into the spatiotemporal regulation of EGFR in physiological and pathological contexts. We also examine how oncogenic mutations disrupt the monomer-dimer equilibrium, driving constitutive signaling and resistance to therapeutics. Mutations such as EGFR L858R, exon 19 deletions, and HER2 S310F cause structural alterations that stabilize receptor oligomerization and drive tumorigenesis. Finally, we discuss how advanced fluorescence techniques are being used to improve the design of targeted therapies, including tyrosine kinase inhibitors and monoclonal antibodies, to better modulate receptor activity. This review describes the critical role of fluorescence-based methods in bridging the gap between structural data and in situ receptor function and also identifies future directions for resolving the regulatory mechanisms of EGFR-family signaling in health and disease.