Anomalous diffusive behavior in intracellular transport mediated by molecular motors

L. BRUNO; V. LEVI; M. BRUNSTEIN; M. DESPÓSITO

San Francisco, USA

Simposio; Biophysical Society 54th Annual Meeting; 2010

Biophysical Society

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. In this work we investigate the motion of pigment organelles or melanosomes driven by molecular motors in Xenopus laevis melanocytes using a high spatio-temporal resolution tracking technique. By analyzing the obtained trajectories, we show that the melanosomes mean-square displacement undergoes a transition from a subdiffusive to a superdiffusive behavior. A stochastic theoretical model, which explicitly considers the collective action of the molecular motors, is introduced to generalize the interpretation of our data. Starting from a generalized Langevin equation, we derive an analytical expression for the MSD, which also takes into account the experimental noise. By fitting theoretical expressions to experimental data we were able to discriminate the exponents that characterize the passive and active contributions to the dynamics. Then, our model gives a quantitative description of active transport in living cells with a reduced number of parameters.