Tuesday, July 10, 2012
177 Stanley Hall, UC Berkeley
Effect of membrane curvature on protein sorting and lateral diffusion
Dr. Patricia Bassereau
Group Leader Membranes and Cellular Functions
Curie Institute, Paris, France
Membrane transport between intracellular compartments, entry or exit out of the cell, imply similar sequential events: membrane deformation, fission from the donor compartment, transport and eventually fusion with the acceptor membrane. The mechanisms behind these biological processes of membrane transformation are actively studied both in the cell biology and the biophysics contexts. Membrane nanotubes with a controlled diameter (15-500 nm) pulled out of Giant Unilamellar Vesicles (GUV) are very convenient tools to address the role of curvature in trafficking events and to measure mechanical effects due to protein binding using optical tweezers. As an example of this type of approach combining in vitro experiments and theoretical modeling, I will present our results on amphiphysin 1, which is implicated in clathrin-mediated endocytosis and contains a N-BAR membrane-binding domain. I will show that membrane curvature induces an enrichment of amphiphysin 1 on the tube, and that conversely proteins induce constriction of the membrane tube.
Another interesting application of membrane nanotubes is to study the role of the membrane geometry on the lateral diffusion of transmembrane proteins by measuring the mobility of individual proteins in tubes using single particle tracking of quantum dots attached to them. We find that diffusion is slower in tubular membranes with smaller radii, in agreement with an extension of the hydrodynamic Saffman-Delbrücks theory to tubular membranes.