Figure 1. Tracking α_1A-AR in response to agonist stimulation.

(A) α_1A-ARs were detected with anti-FLAG antibody and Alexa-555 IgG in live HEK-293A–α_1A-AR cells at 37°C. Images were captured after 30-min stimulation with 10 µM phenylephrine (PE). Two sample trajectories of α_1A-AR particles are shown with red lines (1 and 2). Bar: 10 µm. (B) The trajectories in (A) were plotted (1 and 2, respectively). (C) The plot of the mean square displacement (<r²>) against time (t) to the trajectory in Fig. B(2). The red line is a fit by <r²> = 4Dt+(vt)². Directed movement was confirmed by the superlinear MSD-Δt plots. (D) Velocities of directional movements of α_1A-AR resolved from tracked trajectories at various times after 10 µM PE stimulation plotted in probability histograms. (n = 36, 61, 51, 58, 49 and 53 trajectories in separated cells, respectively).