Analysis of persistance during intracellular actin-based transport mediated by molecular motors

CARLA PALLAVICINI; MARCELO A. DESPÓSITO; VALERIA LEVI; LUCIANA BRUNO

Buzios

Workshop; XI LATIN AMERICAN WORKSHOP ON NONLINEAR PHENOMENA; 2009

Intracellular transport of large cargoes, such as organelles, vesicles or large proteins, is a complex dynamical process that involves the interplay of ATP-consuming molecular motors, cytoskeleton filaments and the viscoelastic cytoplasm. The displacements of particles or probes in the cell cytoplasm as a function of time are characterized by different (anomalous) diffusion regimes. We investigate the motion of pigment organelles (melanosomes) driven by myosin-V motors in Xenopus laevis melanocytes using a high spatio-temporal resolution tracking technique. By analyzing the turning angles (phi) of the obtained trajectories as a function of the time lag, we found the critical time of the transition between anticorrelated and directed motion which was paralleled by a crossover from subdiffusive to superdiffusive behavior in the mean square displacement. Using a stochastic theoretical model that starts from a generalized Langevin equation that explicitly considers the collective action of the molecular motors, we derive an analytical expression for cos(phi) as a function of the time lag, which also takes into account the experimental noise. By fitting our model to the experimental data we were able to obtain a quantitative description of active transport in living cells with a reduced number of parameters.