Influence of cytoskeletal filaments networks on organelles dynamics

M. CECILIA DE ROSSI; LUCIANA BRUNO; MARCELO A. DESPÓSITO; VALERIA LEVI

Congreso; XLI Reunión Anual de la Sociedad Argentina de Biofísica; 2012

Molecular motors are responsible for intracellular transport. These proteins use the energy provided by ATP hydrolysis to move different cargoes along microtubules or actin filaments toward their final destination. However, the cytoplasm behaves as a complex media and their properties may affect the transport in not completely known ways. The cytoplasm is as a viscoelastic media and the existence of mobile and immobile barriers and the unspecific interaction between different cellular components constitute obstacles in cargoes transport and diffusion. Particularly, it has been proposed that cytoskeletal elements like the intricate intermediate filaments network of vimentin can markedly reduce the motility of organelles [1-3]. In this work, we studied the in vivo dynamics of pigmented organelles (melanosomes) in Xenopus laevis melanophores. Using single particle tracking (SPT) we registered individual melanosomes trajectories to analyze the influence of their size on their motility. Our results showed that small organelles, which are supposed to experience a smaller drag force, present more tortuous trajectories in wild type cells. However, when actin filaments are depolimeryzed melanosomes motility markedly increased therefore the dependence with organelles radius was reduced. Contrary to what is expected, the disruption of vimentin network did not increased melanosomes motility in actin depolimeryzed cells furthermore the data exhibit a similar dependence of that observed in wild type cells. These data were interpreted according to a new model that can explain the local influence of the cytoplasm environment on melanosome motion.