Impact of External Stimuli and Cell Micro‐Architecture on Intracellular Transport States

Unraveling the fast and complex processes involved in intracellular transport: Herein, the authors use a rolling‐window analysis with very high temporal resolution to dissect the trajectory of an intracellular tracer and isolate transient active states (see graph). This is a signature of the activity which characterizes living materials. magnified image A living cell is a complex out‐of‐equilibrium system, in which a great variety of biochemical and physical processes have to be coordinated to ensure viability. We investigate properties of intracellular transport in single cells of the amoeba Dictyostelium discoideum , a relevant model organism due to its cytoskeleton simplicity. In the cells, vesicles undergo two types of motion: directed transport, driven by molecular motors on filaments, or thermal diffusion in a crowded active medium. We present results obtained with our recently developed TRAnSpORT algorithm, which performs a high‐resolution temporal analysis of the track of endosomal superparamagnetic particles and splits intracellular transport into different motion states. It results in a two‐state model, distinguishing active and passive transport phenomena. We can extract the precise effect of cellular micro‐ and nanoarchitecture on endosomal transport by disturbing the cytoskeleton through the use of depolymerizing drugs (Benomyl for microtubules, and Latrunculin A for F‐actin). Further, we investigate how cytoskeleton filaments act together in order to maintain cell integrity, by applying external mechanical force on the magnetic particle and influencing its motion.