Dynamics and Spatial Organization of Endosomes in Mammalian Cells

We combine particle tracking and stochastic simulations to analyze the dynamics and organization of early endocytic vesicles in mammalian cells. At short time scales (<10¹  sec) vesicles exhibit 1D symmetric bidirectional motor-driven transport on microtubules such that the mean squared displacement (MSD) scales as t^3/2, but the MSD shows a crossover to facilitated diffusion at longer times (>10¹  sec). Facilitated diffusion results in rapid equilibration of vesicles on microtubules. The asterlike organization of microtubules causes perinuclear accumulation of vesicles despite symmetric transport.