sBMP2 treatment induces ALK3 immobilization within and outside FAs. (A) Super-resolution intensity image of mEos2-ALK3 within FAs of a MEF obtained by sptPALM (50 Hz, 16,000 frames; left) Inset: Fluorescence image of β3-integrin-GFP. Corresponding trajectories are color-coded to show their diffusion modes: diffusive (green), confined (yellow), and immobile (red; right). (B) ALK3 diffusion analysis during sBMP2 treatment. (C) The evolution of trajectories within and outside of FAs were sorted and analyzed (see Materials and methods). Distribution of Log(D) within FA versus outside (mean for cells). The gray areas that include D values <0.011 µm² s⁻¹ correspond to immobile trajectories. (D) Fraction of diffusive, confined, and immobile populations within versus outside FAs (mean ± SEM for cells). (E) D values for free-diffusive events (mean ± SEM for trajectories). (F) Enrichment in FAs (mean ± SEM for cells) for ALK3, with or without sBMP2 (same color code). All results for each condition correspond to pooled data from several independent experiments: ALK3 (10 cells, 47,362 trajectories, 2,509,527 detections) and ALK3 + sBMP2 (10 cells, 83,460 trajectories, 4,147,397 detections).