Human Epidermal Growth Factor Receptor 2 Dynamics Regulated by Actin-Filament Integrity on Cell Membranes Revealed by Single-Nanoconstruct Tracking

This work demonstrates that the integrity of actin filaments can selectively regulate both lateral motion and in-plane orientation of transmembrane proteins on cell membranes. Using anisotropic gold nanostars functionalized with HER2 (human epidermal growth factor receptor)-targeting aptamers as optical probes, we tracked HER2 receptor dynamics on cancer cells using differential interference contrast microscopy. We found that for cells with an intact actin structure, the lateral mobility of receptors was restricted, consistent with actin-supported membrane compartmentalization. When actin filaments were disrupted after treatment with latrunculin A, HER2 receptors exhibited Brownian motion. In parallel, the receptors exhibited longer rotational dwell times corresponding to reduced orientational freedom. Analysis of receptor dynamics revealed that the coordinated translation-rotation regulation by actin filaments only occurred under directed diffusion modes when the cytoskeleton was intact. Two-dimensional single-nanoconstruct tracking provides a real-time approach to uncover how cytoskeletal architecture can organize receptor dynamics in living cells.