Heterogeneity in VEGF Receptor-2 mobility and organization on the endothelial cell surface leads to diverse activation models by VEGF

The nanoscale organization of cell surface receptors plays an important role in signaling. We determined this organization and its relation to receptor activation for VEGF Receptor-2 (VEGFR-2), a critical receptor tyrosine kinase in endothelial cells (ECs), by combining live-cell single-molecule imaging of endogenous VEGFR-2 with rigorous computational analysis. We found that surface VEGFR-2 can be mobile or immobile/confined, and monomeric or non-monomeric, with a complex interplay between the two. The mobility and interaction heterogeneity of VEGFR-2 in the basal state led to heterogeneity in the sequence of steps leading to VEGFR-2 activation by VEGF. Specifically, we found that VEGF can bind to both monomeric and non-monomeric VEGFR-2, and, when binding to monomeric VEGFR-2, promotes dimer formation but only for immobile/confined receptors. Overall, our study highlights the dynamic and heterogeneous nature of cell surface receptor organization and its complex relationships with receptor activation and signaling.