Epidermal growth factor receptor (EGFR) dimerization plays a pivotal role in cellular signaling, influencing proliferation and disease progression, particularly in cancer. Despite extensive studies, the quantitative relationship between EGFR expression levels and dimerization efficiency remains incompletely understood. In this study, we investigated EGFR dimerization kinetics using ensemble-level biochemical assays and single-molecule tracking (SMT) in living cells. Our findings revealed noncanonical negative cooperative dimerization, where the monomer-to-dimer transition rate decreased as EGFR expression increased, challenging the assumptions of a simplistic reaction model. Furthermore, we identified a dimer-specific degradation pathway highlighting the open-system nature of the plasma membrane environment. These findings establish a quantitative framework for understanding EGFR dimerization dynamics, offering insights into the complex regulatory principles governing membrane protein interactions. This model not only improves our understanding of EGFR-mediated signaling but also suggests broader applicability for the therapeutic targeting of membrane protein systems.
