Abstract: The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes for intracellular transport of material in mammalian cells, yeast or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are formed during this process, and destabilize into vesicles. While the role of actin in tubule scission is still debated, literature also provides examples of actin-mediated stabilization of membranous structures.
To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatio-temporally. Depending on network cohesiveness, actin is able to entirely stabilize, or locally maintain membrane tubes under pulling. Indeed, on a single tube, thicker portions correlate with the presence of actin. Such structures relax over several minutes, and may provide enough time and curvature geometries for other proteins to act on tube stability.
In parallel, we developed a new platform to study the local mechanics of membrane tubes using atomic force microscopy (AFM). On a single coverslip we quickly generate millions of substrate-bound membrane tubes, out of which dozens can be imaged by AFM in a single experiment. In addition, we mimic in vivo actin polymerization on tubes, and use AFM to assess the induced changes in mechanical properties