Protein Induced Membrane Remodeling Assayed in Vitro using Lipid Multilayer Micro- and Nanostructures

Abstract

The dynamic self-organization of lipids in biological systems is a highly regulated process that enables the compartmentalization of living systems at cellular and sub-cellular scales. Lipid multilayer micro- and nanostructures on surfaces are a promising new tool with the ability of quantitatively assaying membrane remodeling activity in vitro. This approach combines capabilities of assays based on vesicles in solution, which allow 3D compartmentalization and remodeling, with surface based assays such as supported lipid bilayers that allow rapid optical characterization and microarray compatibility. Here we expose lipid multilayer nanostructures and microstructures to membrane binding and remodeling proteins Sar1 and NDPK. These proteins are found to inflate the multilayers into vesicular compartments. Sar1 inflates them to form giant unilamellar vesicles, while NDPK produces a new inflated phase composed of hemifused vesicles which we refer to as a “foam phase”. A model fit to the data allows quantification of binding affinity and both binding and remodeling kinetics. The lipid multilayer micro- and nanostructures can be easily made by nanointaglio stamping and demonstrate critical dimensions for unique remodeling capabilities. The results suggest implications for the in vivo function of these proteins in vesicle trafficking and lipid transfer between membranes.