This seminar will explore the relationship between membrane curvature and the crowded molecular environment found on cellular membrane surfaces. Biological membranes, which consist of lipids and proteins, define the cellular boundary, facilitate interactions with the extracellular environment, and compartmentalize cellular functions in the organelles. Curved membranes are an essential feature of dynamic cellular structures including endocytic pits, filopodia protrusions, viral buds, and most organelles. Specialized proteins capable of binding membranes and inducing curvature are being identified. However, we lack an understanding of how these proteins function in the crowded membrane environment, achieving the required concentration and organization to drive membrane bending. Based on studies of proteins involved in clathrin-mediated endocytosis, as well as engineered protein-lipid interactions, we propose that protein-protein crowding can drive membrane bending. Specifically, by correlating membrane bending with FRET-based measurements of protein density on synthetic membrane surfaces, we demonstrate that lateral pressure generated by collisions between bound proteins can induce curvature. These findings suggest an efficient mechanism by which the crowded protein environment on the surface of cellular membranes can contribute to membrane shape change.
Our research group is broadly interested in the physical mechanisms that underlie the function of cellular membranes, as well as the opportunity to solve problems in medicine by creating bio-inspired materials and systems that borrow these mechanisms. We are specifically interested in (i) understanding how protein assembly on membrane surfaces defines the shape and content of trafficking vesicles and (ii) applying this understanding to design of drug and gene delivery systems that can actuate their own endocytic uptake and define their own intracellular route.