Membrane Trafficking and Mechanics of the Golgi Apparatus: An in Cellulo Study by Optical Micromanipulation

Abstract

Membrane transport is based on the formation of tubulo-vesicular intermediates traveling from one compartment of the cell to another along cytoskeletal tracks. In vitro studies have shown that physical parameters, such as membrane curvature, tension and composition, influence the budding and fission of transport intermediates. A recent study in cells has highlighted the central role of the actin cytoskeleton in the fission of Rab6-positive transport intermediates from the Golgi apparatus (Miserey-Lenkei et al. 2010). Here we investigate the role of a mechanical stress on intracellular transport in cellulo. We focus on the mechanics of Golgi membranes and the formation of transport intermediates from the Golgi apparatus. Using confocal microscopy, we visualize the deformation of Rab6-positive Golgi membranes applied by an internalized microsphere trapped in an optical tweezers, and simultaneously measure the corresponding forces. Our results show that the force necessary to deform Golgi membranes drops when the actin cytoskeleton is depolymerized, suggesting that actin strongly contributes to the local rigidity of the Golgi apparatus. We also show that the applied stress has a long-range effect on Golgi membranes and induces a sharp decrease in the formation of vesicles from the Golgi apparatus.