Single-molecule imaging reveals the stoichiometry change of epidermal growth factor receptor during transactivation by β 2 -adrenergic receptor

Stimulation of G protein-coupled receptors (GPCRs) can lead to the transactivation of the epidermal growth factor receptors (EGFR). The cross-communication between the two signaling pathways regulates several important physiological or pathological processes. However, the molecule mechanism underlying EGFR transactivation remains poorly understood. Here, we aim to study the GPCR-mediated EGFR transactivation process using the single-molecule fluorescence imaging and tracking approach. We found that although EGFR existed as monomers at the plasma membrane of resting cells, they became dimers and thus diffused slower following the activation of β 2 -adrenergic receptor (β 2 -AR) by isoproterenol (ISO). We further proved that β 2 -AR-mediated changes of EGFR in stoichiometry and dynamics were mediated by Src kinase. Thus, the observations obtained via the single-molecule imaging and tracking methods shed new insights into the molecular mechanism of EGFR transactivation at single molecule level.