Intracellular motor-driven transport of rod-like dynamic organelles along microtubules

BRUNO, LUCIANA; FERNÁNDEZ CASAFUZ, AGUSTINA BELÉN

Puerto Madryn

Conferencia; Statistical Physics on Biological Networks; 2020

INFERNET BA

Intracellular organization requires localizing organelles and other components with high time-space precision. In order to do this, cells use an active transport system consisting of molecular motors and polymerized filaments, i.e. actin filaments and microtubules. Molecular motors are specialized proteins that can attach to different cargoes and carry them along cytoskeletal filaments using energy provided by ATP. Even though several transport models have been proposed and studied, many aspects regarding motor dynamics and organization remain unclear. In particular, most of these models deal with spheric and rigid organelles, which do not allow to explore neither the motor distribution on the organelle?s surface nor their effect on reshaping flexible organelles such as mitochondria.We propose a 1D model for motor-driven transport of rod-like organelles. The model assumes an internal degree of freedom for the organelle that allows it to deform in a damped elastic potential. The motors follow stochastic dynamics and exert local forces on the cargo. Through computational simulations we study the action of different types of motor teams, focussing on transport properties observable during the experiments, such as mean velocity and length variation.We compare these results with experimental trajectories of rod-shaped mitochondria during microtubule-dependent motion in Xenopus Laevis melanophore cells. To this end, we tracked single organelles from confocal microscopy images and analyzed their velocity and changes in their length during processive transport.The novelty in our model relies on the description of the intracellular transport of non-spherical deformable organelles. It allows us to explore in detail the distribution of motors along the organelle and the forces responsible for the length variation, which are not accessible through experimental images. Therefore we can use it to obtain a preliminary interpretation to the deformations of mitochondria observed in living cells.