Figure 6

Suggested model for diffusion of sterol-containing vesicles. (A) Log-Log plot of the average MSD of vesicles tracked in control cells at 37°C. Initially, the MSD has a slope described by anomalous subdiffusion (dashed line) with an eventual transition to a slope described by superdiffusion consistent with active transport (dotted line). From this, we suggest the model presented in panels B-E. On short time scales the vesicles are caught in the meshwork formed by the cytoskeleton, which is composed of microtubule and actin filaments. This meshwork of filaments undergoes thermal fluctuations and is interconnected by motor proteins, which are constantly pulling on the filaments. Thus, the cytoskeletal network is constantly rearranging, causing the vesicles to appear to move by anomalous subdiffusion. On longer time scales directional motion caused by motor proteins moving along a filament dominates, thus causing a directed vesicle motion on longer time scales.