Abstract
Membrane fission is the final step enabling the release of vesicles during endocytosis. Dynamin is a protein required for this crucial process in clathrin-mediated endocytosis. It polymerizes into a helix at the neck between the plasma membrane and the endocytic bud. A constriction of the helix occurs upon guanosine triphosphate (GTP) hydrolysis leading to fission. Here we show how the fission mechanism is regulated temporally, spatially and energetically. We perform in vitro experiments where all mechanical and chemical parameters are controlled. Membrane nanotubes are pulled from giant unilamellar vesicles (GUV) using optical tweezers. Membrane tension is set by aspirating the GUVs within a micropipette. Dynamin and GTP are injected near the tube. Tubes always break few seconds after dynamin starts polymerizing. We show that the probability of fission depends on GTP concentration. Membrane tension and bending rigidity are key parameters controlling fission times in a non trivial way. Saddle-like shape favors membrane fission supporting the idea that negative Gaussian curvature plays an important role in the process.
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